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Title: The Invention of the Track Circuit
The history of Dr. William Robinson's invention of the
track circuit, the fundamental unit which made possible
our present automatic block signaling and interlocking
systems
Author: American Railway Association
Release Date: March 20, 2014 [EBook #45179]
Language: English
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[Illustration: Photograph and written signature of William Robinson]
THE INVENTION OF THE TRACK CIRCUIT
THE HISTORY OF DR. WILLIAM ROBINSON'S INVENTION OF THE TRACK CIRCUIT
THE FUNDAMENTAL UNIT WHICH MADE POSSIBLE OUR PRESENT AUTOMATIC BLOCK
SIGNALING AND INTERLOCKING SYSTEMS
SIGNAL SECTION
AMERICAN RAILWAY ASSOCIATION
NEW YORK 1922
PREFACE
Believing that no more fitting memorial can be prepared in honor of Dr.
William Robinson than to reproduce the salient points relating to his
great achievement as written and published by himself in 1906 under the
title of "History of Automatic Electric and Electrically Controlled
Fluid Pressure Signal Systems for Railroads," the committee has
accordingly drawn largely from this pamphlet for the material contained
in Part I.
Part II is devoted to W. A. Baldwin, formerly General Superintendent of
the Pennsylvania Railroad, who was responsible for the first
installations of automatic block signals controlled by track circuits.
As this memorial would not be complete without a description of the
track circuit, its principle and operation under present day signaling
practices, Part III is accordingly devoted to this subject.
HERBERT S. BALLIET, _Chairman_;
KEITH E. KELLENBERGER,
HENRY M. SPERRY,
_Committee_.
CONTENTS
RESOLUTION 1
I
THE INVENTION OF THE TRACK CIRCUIT 3
Robinson's Patent 42
Robinson's Description of His Invention 50
Dr. Robinson's Record, Wesleyan University 59
Dr. Robinson's Record, A.I.E.E. 60
II
WILLIAM A. BALDWIN 68
III
THE TRACK CIRCUIT 76
Its Principle 77
Its Characteristics 85
The Extent of its Use 98
IV
THE TRACK CIRCUIT IN GREAT BRITAIN AND ON THE CONTINENT,
BY T. S. LASCELLES 103
Some of the First Installations 106
Track Circuits on the Continent 109
THE TRACK CIRCUIT[1]
"Perhaps no single invention in the history of the development of
railway transportation has contributed more toward safety and despatch
in that field than the track circuit. By this invention, simple in
itself, the foundation was obtained for the development of practically
every one of the intricate systems of railway block signaling in use
today wherein the train is, under all conditions, _continuously active_
in maintaining its own protection.
"In other words, the track circuit is today the only medium recognized
as fundamentally safe by experts in railway signaling whereby _a train
or any part thereof may retain continuous and direct control of a block
signal while occupying any portion of the track guarded by the signal_."
[1] From the Third Annual Report of _The Block Signal and
Train Control Board to the Interstate Commerce Commission_.
Dated Nov. 22, 1910.
Resolution
Adopted at Annual Meeting of Signal Section, A.R.A. Chicago, June,
1921
WHEREAS, Almighty God, in the exercise of His Divine will, has removed
from this world our late honorary member, Dr. William Robinson, and,
WHEREAS, Dr. Robinson, well called the "father of automatic block
signaling" because of his basic invention of the closed track circuit
August 20, 1872, began the development of an automatic signal system
in 1867 and installed the so-called "open circuit" system at Kinzua,
Pa., on the Philadelphia & Erie, now the Pennsylvania Railroad, in
1870, and,
WHEREAS, he worked on the development of fiber for insulated rail
joints in 1876 and also developed the channel pin about the same time,
and,
WHEREAS, one of the first signals controlled by more than one track
circuit was installed under his direction at the Tehauntepec tunnel in
California in 1877, and,
WHEREAS, his death at Brooklyn, N.Y., on January 2, 1921, at the age
of 80, is an irreparable loss to the Association.
THEREFORE, we, members of the Signal Section, American Railway
Association, pay our last sad tribute to his memory and express our
deep appreciation of the many and lasting obligations that our members
and friends owe to him, and by words and outward token express our
sincere sorrow for the irreparable loss the Association has sustained.
THEREFORE, be it _Resolved_, that a fitting memorial to the memory of
Dr. William Robinson, commemorating the 50th anniversary of his
invention of the closed track circuit, be prepared and presented to
this Association at the Annual Meeting in 1922.
_Resolved_, that these resolutions be spread upon the records of the
Association.
THE INVENTION OF THE TRACK CIRCUIT
About 1867 William Robinson, then a recent graduate from college,
entered actively upon the development of an automatic signal system
for preventing accidents of various kinds on railroads. His attention
was called to the subject by the consideration of certain railroad
accidents which had occurred, and for the prevention of which there
were no adequate means known.
From this starting point he developed such a system, and in 1869,
constructed an elaborate model illustrating the same, which he
exhibited at the American Institute Fair in New York City, in 1870.
This system was what is now known in the art as a "wire" or "open
circuit" system; that is, there were circuit-instruments in proximity
to the track which were actuated by the wheels of a car. The action of
the wheels on a lever at one point closed the circuit through a relay,
whose magnet was so arranged that the instant it was magnetized it
attracted its armature and kept its own circuit closed. The circuit of
the magnet which directly actuated or controlled the signal was under
control of the relay, which operated to open and close the signal
circuit directly.
When the train or car proceeded to the proper point beyond, it
actuated a reversing lever, thus opening the relay circuit and
reversing the signal.
In the model described the reversing lever operated to open the relay
circuit by cutting off the battery therefrom by short circuiting.
This model was in continuous and perfect operation throughout the
duration of the fair.
At the close of the fair Mr. Robinson had some of his descriptive
circulars left over. These he immediately sent out to railroad
companies at random.
One of these circulars, at least, was as seed sown in good ground. It
elicited an immediate response from Mr. William A. Baldwin, general
superintendent of the Philadelphia and Erie railroad, with the result
that Mr. Baldwin, who was an old telegraph operator and a very able
and progressive railroad man, on looking into the system was so
impressed with its practicability and importance that he at once
arranged with Mr. Robinson to make an installation of the system on
his road. This was in 1870.
At that time Mr. Theodore N. Ely, now chief of motive power (1906) of
the Pennsylvania railroad, was assistant superintendent of the
Philadelphia & Erie, and, under direction of Mr. Baldwin, furnished
Mr. Robinson with all the facilities and material necessary for
prosecuting the work of installation.
This installation was made at Kinzua, Pa., and after a little
experimenting was soon in perfect working order, performing all
claimed for it, and considered satisfactory by the railroad company.
This was a normally open-circuit wire system, however, controlled by
track levers, as above described, in connection with the model.
As soon as it was found to be working perfectly and accomplishing all
claimed for it, Mr. Robinson, who aimed to be the most severe critic
of his own work, entered systematically into a deeper study of the
system from the standpoint of a railroad man, with a view of finding
the weak points in it, if any existed.
He soon discovered the following serious defects, which are inherent
in all normally open circuit or wire systems of automatic signaling,
without exception.
Such systems are extremely limited in their functions, and _may, under
certain circumstances_, show a SAFETY signal when the danger actually
exists which they are designed to avert, as in the following cases:
_First_: A train enters regularly upon the section and sets the signal
at danger; the train breaks in two, the forward part passes off the
section, reverses the signal and shows ALL CLEAR behind that portion
of the train remaining on the section; and a following train, lured on
by the false signal ALL CLEAR, dashes into the stalled portion of the
preceding train left standing on the section. This is extremely liable
to happen on sharp curves and grades, where breaks are not of uncommon
occurrence.
_Second_: A train may enter within the section from the opposite end
or from a siding, thus blocking the track, while the signal, not
having been affected, shows ALL CLEAR as before, a false signal again.
_Third_: If a line wire break or other connection be interfered with
accidentally or maliciously, or the battery fail from any cause, the
signal will invariably show ALL CLEAR, under every train passing over
the section, a false signal again.
Mr. Robinson at this early date recognized the above serious
objections as inseparable from open circuit system of signaling,
apparently, before these defects were recognized by any one else, and
at once entered upon the solution of the problem presented, of
eliminating these objections by producing a signal system which would
meet all the requirements of safe and efficient railroading.
He reasoned, first, that to accomplish this result every car and every
pair of wheels in the train must have controlling power over the
signal throughout every inch of the block section, and second, the
signal should go to danger by gravity, the electric current being used
to hold it at safety.
Could these two results be accomplished? Could the rails be used in
any way to carry the primary current in a reliable manner? Manifestly
not by any open circuit means, for the reason that sections of rails
of even moderate length, on open circuit, would form a good ground,
especially in damp or wet weather, thus keeping the circuit closed
continuously and preventing any operation of any kind.
He at once cast aside this open rail circuit idea as fruitless, and
having previously, in 1869-70, used the short circuiting principle in
his model, as above stated, he concluded that this principle presented
the only possible solution of the problem.
He then made drawings of the closed rail circuit system substantially
as it is used today, and in 1871 applied for a patent thereon, broadly
covering the closed rail circuit system.
In 1872 he made an exhibition of this system at the State Fair, held
at Erie, Pa. Here he placed a large gong on the end of one of the
buildings, on the outside, and inside he had a track made in sections
placed in a long water tank made for the purpose. The track was
covered several inches deep with water and the running gear of the car
model was similarly immersed.
The system was connected on the short circuit principle through the
rails. Wires connected the gong with the back contact of the track
relay.
The water had no perceptible effect on the operation of the apparatus,
and when the car was run on the signal section it short circuited the
current from the relay, which, releasing its armature, closed circuit
through its back contact and thus through the magnet of the gong
circuit, thus setting the gong ringing loud enough to be heard all
over the grounds.
On running the car off the section the current returned to the relay
energizing the same and thus opening the gong circuit at the back
contact of the relay, thereby causing the gong to cease ringing.
The whole operation was perfect, demonstrating the successful
operation of the closed circuit system, and attracted great crowds of
people as well as the marked attention of practical railroad men.
It will be understood, of course, that the local circuit may be
normally open as above described and used, or normally closed as now
commonly used, according to the exigencies or requirements, or
preferences of the parties using the same, and when desired, a visual
signal may be substituted for the audible signal above described.
These are all minor details not involving separate invention.
Mr. Robinson had previously explained the new closed rail circuit
system to Mr. Baldwin, who was greatly interested and expressed his
confidence in it and requested Mr. Robinson to install the system at
Kinzua, where he had already installed the open circuit wire system.
[Illustration: Fig. 1.
Robinson's Closed Rail Circuit System. Philadelphia & Erie Railroad,
1872.]
As all the signal apparatus, relays, batteries, office switches and
overlapping devices were already in operation there, it took but a
short time to convert this open circuit system into a closed rail
circuit system.
The first experiments proved conclusively that the system would work.
The track, however, was in a fearfully unsuitable condition for the
purpose. The light rails were fished together by a four foot wooden
bar on the outside, and a twelve inch fish plate on the inside. There
were two holes through the iron fish plate, allowing one bolt for each
rail and four holes through the wooden bar, two for each rail.
However, with a little care he managed to get the current working
through the whole length of the section about a mile and a quarter in
length.
It was evident, however, that on such a section as this a rail bond of
some kind would be necessary for reliable, continuous service, and
here, at this time, in 1872 Mr. Robinson conceived the invention of
the bond wire method of electrically connecting the rails, now in
universal use, or its equivalent, on every electric railway throughout
the world using the rails for a return.
As it had been determined to lay new rails at Kinzua, another
installation of the closed rail circuit system was ordered and
immediately made at Irvineton, Pa. This signal is illustrated in Fig.
1.
It will be observed that the above installation, like that at Kinzua,
not only displays a visual block signal, but also operates in
connection therewith a loud gong which has been easily heard at a
distance of a half mile, and was really heard by passengers in trains
passing, with closed windows. An engineer could not possibly pass
without hearing it.
A wire is seen at the upper part of the signal box, running out to the
right. This is an overlapping signal wire.
A tell-tale bell was also placed in the station, indicating the actual
position of the signal, and also a manual switch, whereby the agent
could at any time cut off or short circuit the track battery and
expose the danger signal against a train and instantly receive a
return signal when the danger signal was actually exposed.
The Irvineton installation worked perfectly from the first never
failing. The locomotive engineers were delighted with it and soon gave
it the name of "The old reliable."
[Illustration: THE ROBINSON CLOSED RAIL CIRCUIT.
Fig. 2.
Wm. Robinson, 1871, Patented in France, February 29, 1872, and
United States August 20, 1872. Re-issued July 7, 1874. No. 5958.]
The Robinson closed rail circuit, which now forms the basis, according
to the best information, of every efficient automatic electric,
electro-pneumatic and electrically controlled fluid pressure system
throughout the world, is illustrated in its simplest form, in Fig. 2.
This figure shows the railroad track divided into sections, a mile
more or less in length, the section rails being insulated from
adjacent sections. A light battery has its terminals connected to the
opposite rails at one end of the section and at the other end a relay
magnet has its terminals connected to the opposite rails. Thus the
current passes through the whole length of the section, keeping the
relay on continuously closed circuit and magnetized as its normal
condition. The relay thus keeps the secondary circuit, which directly
controls the signal, normally closed, whereby the signal is normally
held in a position indicating safety.
When a train enters upon the section, the wheels and axles, connecting
the opposite rails thereof, short circuit the current from the relay,
which instantly releases its armature, thus opening the signal
circuit. The signal is then instantly thrown to the danger position by
means of a counterbalance.
The signal may be of the enclosed disk type, electro-mechanical,
electro-pneumatic, electrically controlled gas, or of any other kind.
The Robinson patented system is broad, basic and a generic creation;
it is not limited to any specific construction or arrangement of
signal but covers all kinds.
In expounding the early history of the art of automatic signaling, the
following photographic reproductions from some of Robinson's early
circulars and patents will be of interest.
The following sections on CURVE, TUNNEL, STATION, SWITCH and
DRAW-BRIDGE SIGNALS are a photographic reproduction from a circular
issued by Mr. Robinson in 1870:
CURVE AND TUNNEL SIGNALS.
A train approaching a curve will throw up a red signal around the
curve as a warning to trains from the opposite direction, and will
also exhibit a signal in its rear. Thus, collisions from front or
rear are guarded against. These signals may be used throughout the
whole extent of a road.
In entering a tunnel a train will exhibit a signal at the other
end to indicate its entry, and when it gets through it will lower
the signal and ring a bell at the opposite end to indicate its
exit.
STATION SIGNALS.
A train when it leaves a station, and at various points as it
passes, will indicate to the stations along the line, its
Location, Direction, Rapidity and Length. Thus all necessary
information regarding moving trains will be automatically
announced every few minutes at the stations.
SWITCH AND DRAW-BRIDGE SIGNALS.
If a switch or draw-bridge is misplaced an approaching train will
set an alarm ringing at the station and will also exhibit a red
signal ahead of the train as a warning to the engineer that the
switch is misplaced.
The following heading and sections are photographic reproductions of
parts of a circular issued by Mr. Robinson at the time of its date,
"September, 1872."
It will be observed that certain of these sections are the same as
above reproduced from the circular of 1870.
It will be noted also that the description of the system begun after
the heading is not here completed, for the reason that a full
description is found elsewhere in this history.
ROBINSON'S IMPROVED SYSTEMS
OF
ELECTRIC RAILWAY SIGNALS
For Switches, Draw-bridges, Crossings, Curves, Cuts, and Tunnels;
also, to indicate the Location, Direction, Rapidity, and Length of
Trains.
IMPORTANT IMPROVEMENTS.--ELECTRIC SIGNALING WITHOUT TRACK
INSTRUMENTS, OR LINE WIRES.
THE NEW SYSTEM.
The operation of this system is as follows: A railroad track is
divided into sections of any desired length, say one mile, more or
less, by separating the abutting rails from metallic contact with
the adjacent sections, but preserving metallic continuity
throughout the length of the section. The insulation of the
abutting rails is accomplished
CURVE AND TUNNEL SIGNALS.
A train approaching a curve throws up a red signal around the
curve, as a warning to trains from the opposite direction, and
also exhibits a signal in its rear. Thus, collisions from front or
rear are guarded against. These signals may be used throughout the
whole extent of a road.
In entering a tunnel a train exhibits a signal at the other end to
indicate its entry, and when it gets through it exhibits a signal
at the opposite end to indicate its exit.
STATION SIGNALS.
A train when it leaves a station, and at various points as it
passes, indicates to the stations along the line, its Location,
Direction, Rapidity, and Length. Thus all necessary information
regarding moving trains is automatically announced every few
minutes at the stations.
The batteries for operating the signals will last for months
without attention, and one man can readily attend to all the
signals and batteries throughout the whole extent of a road.
In all cases, where practicable, the signal wire should be carried
through the coils of a bell-magnet in the nearest office. By this
means the operator is informed when the battery power is
decreasing, and warned that it requires renewing.
Office connections can be made, when desired, so that the signals
may be operated by a telegraph key from the office, as well as by
passing trains.
The signal wires may be tapped at intervals all along the line,
and led into small cast iron boxes placed conveniently on the
telegraph poles. Conductors of all trains, furnished with keys to
these boxes, can, in case of special accident, go to the nearest
box, touch a key within the same, and thus set danger signals at
some distance in front and rear of their trains. The telegraph
keys in these boxes not only set the danger signals as described,
but they also place the said signals, for the time being, entirely
out of control of moving trains.
THE CLOSED CIRCUIT.
The new system, as described, with closed circuit, is the best
ever devised for "block-signaling," since the failure of the
battery through neglect or otherwise, cannot possibly be
productive of disastrous results to the train, however implicitly
the signals may be relied on.
_From the French of Feb. 1872 [Translation]._
88th claim. "Connecting a battery B5, and a magnet M5 with the
rails _a9_, _b9_, of a section of railroad track C5 in such a
manner that when said rails are joined by a metallic bridge,
the electric current will be diverted from the magnet M5, but
so that when said bridging device is removed from said section
C5 the electric current will be free to pass through and
charge the magnet M5."
93d. "A signal or signals audible or visual in combination
with the battery B5 and the rails of a railroad track, the
whole being arranged to actuate the signal or signals,
substantially as described."
~WILLIAM ROBINSON.~
ST. PETERSBURG, Clarion County, Pa., September, 1872.
It will be observed that some of the foregoing sections refer to the
open circuit system, some specifically to the closed circuit system
and some are applicable to either or both.
The following is a photographic reproduction of a postal card issued
and distributed broadcast by Mr. Robinson at the time of its date,
"May, 1873." It needs no comments.
ROBINSON'S
WIRELESS ELECTRIC SIGNALS,
THE SIMPLEST, CHEAPEST, and
Only Absolutely SAFE Electric Signals in Existence,
NOW IN SUCCESSFUL OPERATION ON THE
BALTIMORE AND OHIO,
PHILA., WILMINGTON & BALTIMORE,
PHILADELPHIA AND ERIE,
AND OTHER RAIL ROADS.
They work as AUTOMATIC BLOCKS with tell-tale alarms, OFFICE,
STATION, ROAD CROSSING and SWITCH SIGNALS, and BROKEN RAIL
DETECTORS. These signals have worked uninterruptedly through
last winter regardless of rain, snow, slush or sunshine.
Descriptive circulars on application.
MAY 1873. WM. ROBINSON, St. Petersburg, Pa.
[Illustration: Fig. 3.
Illustration from Robinson's Circular of "January, 1874," showing
the Closed Rail Circuit, Relay and Overlapping System.]
It is pointed out that the above illustration of January, 1874, shows
the Robinson closed track circuit, as heretofore described, the relay
R and the track battery I forming a part thereof, the signal actuating
magnet E, the signal C operated thereby, the circuit wires of said
magnet E connected to, and controlled by, the relay R, and the
overlapping or distant signal L, with its circuit H controlled
absolutely by the position of the signal C, the whole showing a
complete closed track circuit overlapping system, with home and
distant signals.
The following sections are from this circular of January, 1874:
"When it is desired to operate a secondary signal thrown forward
or back of the primary, a line wire H is used, attached to the
primary signal C in such a way that the secondary signal cannot
possibly operate unless the primary signal C is first exposed,
thus closing circuit on the wire H. The primary signal battery K
is used to operate the secondary signal."
"To set the signal from an intermediate station a wire from each
rail of the section A is run into the station. When these wires
are connected by a key, the current from the battery I is placed
on short circuit, and the signal exposed as before." (See Fig. 7.)
"The following functions may be embraced in the signals of a
single section. BLOCK SIGNALING, both automatic and manipulated,
SWITCH, DRAWBRIDGE, ROAD-CROSSING, and STATION-APPROACH SIGNALING,
and BROKEN RAIL DETECTING."
"In this system it will be observed that, since the signal is
exposed mechanically, any tampering with the rails or connections,
or failure of the battery, will invariably result in exposing the
signal; any error therefore which may occur from any cause will be
in behalf of safety. _It is impossible to show safety when the
danger exists which the signal is designed to avert._"
During the early seventies Mr. Robinson made other closed rail circuit
installations on the Philadelphia & Erie and other railroads in
Pennsylvania and Maryland.
Visit of the Pennsylvania R.R. Officials
On October 24, 1873, a special inspection train of the Pennsylvania
railroad passed over the Philadelphia & Erie railroad, westward. The
Pennsylvania R.R. officials aboard were: Mr. A. J. Cassatt, at that
time general manager; Mr. Gardner, general superintendent; Mr. Lewis,
controller; Mr. Robert Pitcairn, superintendent western division, and
Mr. Frank Thomson, superintendent motive power.
Mr. Wm. A. Baldwin, general superintendent of the P. & E. road, was of
the party, and Mr. Robinson joined the party on the latter road, and
continued with it through to Erie, which was reached in the evening.
Stops were made at Ridgway on the Middle division and at Irvineton on
the Western division to examine the Robinson closed circuit rail
system of signals, which were in full operation at those points. A
thorough examination and various tests were made, to all of which the
signals responded promptly and perfectly.
The following is from a letter by Mr. Robinson to his brother on
October 25, 1873:
"Mr. Baldwin could not say enough in favor of the signals." * * *
"Of course I remained in the background, except, as to giving
explanations. After a while Cassatt, Pitcairn and Thomson got into
a discussion of the battery and other points, and called me into
the ring to enter into the discussion, and it was quite animated
for some time. Pitcairn proceeded to give his idea of what a
signal should be, and Mr. Baldwin and the rest proceeded to show
him that this, was exactly his ideal."
"Mr. Gardner, after learning _modus operandi_ from diagrams &c.
proceeded to lay down the law to the rest, demonstrating how they
would have 'prevented those accidents.'"
"They were all very much pleased with the signals but their
operation seemed such a surprise that I judge it will take them
several days to think over and realize the actual operation and
importance of the thing."
Robinson's Work in New England
In December, 1875, Mr. Robinson went to Boston and took up his
residence there.
In January, 1876, he made an installation of his closed rail circuit
system between Elm street and North avenue, West Somerville, on a
branch of the Boston and Lowell railroad. This installation worked
perfectly from the beginning.
The Emperor of Brazil Examines the Robinson Signal System
In June, 1876, His Imperial Majesty, Dom Pedro II, Emperor of Brazil,
being then in Boston, graciously accepted an invitation from Mr.
Robinson to examine his Wireless Signal System in operation on the
Boston & Lowell railroad. Accordingly, on June 14, they proceeded
together by special train to West Somerville for the purpose.
The following is an account of the visit, from the _Boston Post_
of June 15, 1876:
"DOM PEDRO II.
"HIS MAJESTY WITNESSES THE OPERATIONS OF RAILROAD SIGNALS.
"Though the visit of His Majesty, the Emperor of Brazil, to this
city has been a brief one, yet it is not hazardous to say that no
other crowned head or representative of royalty who has ever
appeared in Boston has more closely inspected the places where
centre arts, sciences and manufacturers than he.
"In compliance with an invitation, the Dom proceeded yesterday
morning to witness the workings of Robinson's Wireless Signal
System, now in operation on a portion of the Lowell railroad. The
Emperor and several members of his suit took passage on board a
special train on the Lowell railroad soon after 8 o'clock
yesterday morning and arrived at the West Somerville station about
8:30, where they were met by Professor Robinson, who at once began
to explain to the royal party his system. At Elm street a large
visual signal is placed which is controlled by the current from a
single cell of a battery connected with the rail sections at North
avenue, no line wires whatever being used. While the Emperor
watched the signal at Elm street trains were run over the whole
length of the signal section in both directions. As soon as the
train entered upon the section at either end, the signal, without
a moment's delay, showed the track "blocked," and when the train
passed off the section it instantly changed the signal to "all
clear." Then a rail was torn up, and almost instantly thereafter
the signal denoted "danger" and remained so until the rail was
restored and properly coupled up, when it as quickly changed to
"all right." Mr. Robinson gave various other demonstrations
illustrating the working of the system. To all the tests the
signal instantly responded. His Majesty was much interested, and
entered into a somewhat lengthy discussion with Professor Robinson
in regard to the operations which he had witnessed. The Emperor's
questions displayed profound scientific knowledge, and he fully
comprehended the system. At the conclusion of the experiment Dom
Pedro thanked Professor Robinson for his kindness in explaining
and illustrating his system, and invited him to communicate with
the Brazilian government with a view to introducing the system in
Brazil. On the return of the party to the Lowell depot in Boston,
the Emperor was received with great applause, which he politely
acknowledged by waving his hat."
It will be interesting to note that on June 14, 1876, the day the
Emperor inspected the Robinson Signal System at West Somerville, the
battery had been in operation exactly 180 days without any attention
whatever except that on two occasions a little water had been added to
make up for evaporation, the signal working perfectly all that time
and the battery with full strength.
[Illustration: Fig. 4.
Robinson's Electro-Mechanical Signal in Operation at West Somerville
when Inspected by the Emperor of Brazil in 1876.]
The following is from a report on the above signal by the station
agent at Elm street, dated June 2, 1877, eighteen months after it had
been installed:
"Robinson's Electric Signal at this place has been working
uninterruptedly since it was first put in operation. * * * The
signal is entirely reliable."
The above signal continued to work perfectly for a number of years
until the signal post, which was of wood, rotted down.
[Illustration: Fig. 4a.]
The signal mechanism used on the Robinson signal at Elm street was of
the electro-mechanical type.
Figure 4 is a half tone of the identical signal mechanism in operation
there when the Emperor of Brazil examined the system with Mr.
Robinson, on June 14, 1876.
It is pointed out that the above signal mechanism, Fig. 4, shows a
battery or pole changing attachment which is more clearly shown in
Fig. 4a, reproduced from Robinson's British patent No. 3479 of August
29, 1879.
In this device the movement of the cam i^2 not only changes the
battery but changes the polarity through the magnet M^2, which may be
placed anywhere and used for any purpose.
A special device for the same purpose was used not only in connection
with the relay on the West Somerville signal, but on many others
installed by Mr. Robinson.
This battery and pole changing device is more fully described in
Robinson's U.S. patent, August 25, 1874, No. 154,520, Automatic
Commutator; Application filed July 18, 1873.
The following extract therefrom, and claim, may be interesting:
"It will be observed also, that while the actual change of battery
may be caused to take place when the magnet attracts its armature,
yet I prefer to arrange it so that no change of connections shall
take place when the armature is attracted, the actual change
taking place only during the reverse movement of the armature,
caused by the retractile force of the spring. Furthermore, when
desired, the batteries may be so connected in circuit that reverse
currents shall be passed through the magnets every time the
batteries are changed."
CLAIM 2. "In combination with the electro-magnetic commutator
having the described circuit connections, the rail sections A'A*,
the one closing the circuit through the commutator, and thereby
determining the battery to be connected to the other rail section,
substantially as and for the purpose set forth."
It must be admitted that there does not seem to be a very long step
between the disclosures of this patent and the present method of
operating a distant signal by reversing current through a rail
section.
It will be observed that in this patent one rail is used as a return
for a plurality of batteries connected to independent opposite rail
sections.
In an autograph letter addressed to the author by Professor Henry,
secretary of the Smithsonian Institution, under date of October 14,
1875, the Professor discusses Robinson's peculiar method of using
batteries in signaling by which he obtained the above wonderful
durability of 180 days or more without renewal, and pronounced the
results obtained "very remarkable." His discussion of the subject is
somewhat suggestive of the principles of the storage battery.
Switches
In 1876, 7 and 8, Mr. Robinson made a number of installations on the
Boston and Providence, Old Colony and the Boston, Lowell and Nashua
railroads.
On the latter road, at Wilmington Junction, he equipped two parallel
sections of the double track, including six switches, in this short
space, five of them connected with one of the blocks. These sections
were arranged as regular closed circuit blocks, operative under the
moving trains. The switches were also connected up in such a way that
every switch had to be closed and locked for the main line or the
danger signal would be exposed against approaching trains. This
installation was made in 1876.
The switch connection applied to these switches is shown in Fig. 5 and
a general plan of the same is illustrated in Fig. 6. Both of these
figures are reproductions from Robinson's aforesaid British patent of
1879.
[Illustration: Fig. 5.]
[Illustration: Fig. 6.]
It will be observed that when the switch is on the main line the wires
7, 8 are connected by the plug 6 on the switch connection, thus
completing a working circuit through the rails and around the switch,
but when the switch is placed for a siding the wires 7 and 9 are
connected by the plug 5, thus short circuiting the current from the
magnet M, thus producing the same effect as would the presence of a
train on the section. It is always better to short circuit the current
than trust to the mere opening of circuit since short circuiting is
sure to produce instantaneous results.
It will be observed, however, that in the above case the movement of
the switch connection both opens the rail circuit and short circuits
the current from the relay.
It may be here stated that Mr. Robinson equipped three switches in one
closed circuit block, in the manner described above, on the
Philadelphia and Erie railroad in 1873.
[Illustration: Fig. 7.]
Fig. 7, from Robinson's English patent of 1879, aforesaid, shows the
switch G arranged to operate the signal by hand from an office,
station or telegraph post by the roadside, as heretofore described.
Drawbridges
About the time he made the Wilmington installations above described,
Mr. Robinson made an installation of his system also on the Old Colony
railroad, in which one block signal section at Somerset included a
drawbridge. He included the track rails of the drawbridge in the track
circuit in such a way that the withdrawing or loosening of any one of
the bridge lock-bolts would display the danger signal, which remained
exposed until the bridge and its lock-bolts were all restored to their
normal condition insuring safety.
Tunnels
Long wet tunnels present peculiar difficulties to the reliable
operation of the rail circuit; and yet these difficulties are readily
overcome by including one or more additional relays in the signal
section, as shown in Fig. 8, which illustrates the application of the
Robinson track circuit system as applied to the Tehauntepec tunnel in
California.
Mr. Robinson forwarded the signals and necessary instructions, and the
installation was made by Mr. Stephen D. Field, secretary of the
Electrical Construction and Maintenance Co. of San Francisco.
[Illustration: Fig. 8.]
Figure 8 is from a sketch made by Mr. Field in a letter dated San
Francisco, March 21, 1877, addressed to Mr. Robinson.
In this letter Mr. Field says: "I am just in the receipt of yours of
the 12th. I had anticipated your diagram and have the signals arranged
as you show.
"I use the system connected up as follows:
"In the tunnel the rails are buried in wet mud; outside no moisture
touches them for six months of the year."
It will be noted that in the above case the signal section is two
miles long, the tunnel being one mile long, with its rails "buried in
wet mud," and the section extending one-half mile at either end of the
tunnel. An extra relay and battery are placed in the center of the
section connected up as shown. Thus, where conditions require, a
signal section may be divided up into a number of sub-sections.
Later advices showed that the above signals worked perfectly and gave
entire satisfaction.
Insulated Joints
In 1872 and the early seventies Mr. Robinson insulated the rail joints
to form the sections by wooden bars, substantially as shown in Fig. 9.
[Illustration: Fig. 9.]
[Illustration: Fig. 10.]
In 1876 and later he usually insulated the joints as shown in Fig. 10,
using the Fisher & Norris trussed joint as a basis. Vulcanized fiber
is placed between the bottom of the rail ends and the base plate, and
fiber is placed between the flanges of the rails and the forelocks,
and fiber, the shape of the rail section is placed between the ends of
the adjacent rails, all as shown in Fig. 10. This makes an excellent
insulated joint, both mechanically and electrically.
Rail Bonding
Dry rust forming between the fish plates and the rails of the track,
at the joints, makes a poor conductor, and hence the low current,
from only one or two cells of battery used in the rail circuit for
signaling is very liable to find sufficient resistance at the joints
from this cause to prevent the continuous passage of the current
through the rails to the relay.
Mr. Robinson discovered this difficulty in his first experiments in
rail signaling in 1872 and the necessity for making a reliable
electrical connection from rail to rail in order to insure the
reliability of his closed circuit signal system.
As heretofore stated, therefore, he at that time conceived the
invention of the bond wire, Fig. 11, for this purpose, the connection
to be made by drilling holes in the adjacent rails, driving the ends
of the wires tightly into these holes, and making the connection so
close that there would be no room for moisture to penetrate or rust to
form. And as an alternative form he proposed to secure the ends of the
wire, or of a plate, to the adjacent rails by soldering, as shown in
Fig. 12.
In those early days there were serious technical objections to both of
these methods.
_First_: The difficulty and expense of boring holes in all the rails
of the section and connecting them up, and the difficulty of getting
the railroad company to consent to such an innovation to test what at
that time might be regarded as an experiment, and
_Second_: Soldering seemed impracticable on account of the difficulty
of heating up the rail quickly enough at the required point.
Mr. Robinson, therefore, postponed the application of the bond wire
until he could secure better facilities for applying and using it.
He, meantime, experimented along other lines, however, for the purpose
of securing good electrical connection between adjacent rails without
boring holes therein. One of these methods was very successful. It
consisted in the use of elastic split springs having their ends
resting on the flanges of the adjacent rails, and held in place by
small blocks secured to the ties. The passing of a train depressing
the rails slightly caused a slight frictional movement between the
rails and the springs, thus preserving good electrical contact.
In the West Somerville installation, near Boston, made in January,
1876, as heretofore described, Mr. Robinson used the bond wire shown
in Fig. 11. In applying this, holes were bored in the rails and the
wire, fitting the holes as closely as possible, were forced in. A
semi-circular punch was then carefully used to set the metal up close
around the wire.
There has been no better bond wire devised since then except in
mechanical construction. Bonds of various designs have been made
heavier, and with heavier end plugs for mechanical connection to the
rails.
These are good features as they render the bond less liable to
breakage, and, as is well known, for electric railroads they should be
much heavier than required in signaling, for the sake of conductivity.
A bond wire, to get best results, should be homogeneous, made of a
single piece of metal, or if made of several pieces, all the pieces
should be welded, or at least, soldered together. They should be of
sufficient length to insure flexibility without disturbing the
connection if the rails should move relatively to each other, and the
whole circumferential surface of the plug end, or its equivalent, when
possible, should be in the closest possible direct contact with the
rail, that is, the bond plug should make connection with the rail as
nearly as possible--homogeneous. Welding would be the ideal connection
but it is not always practicable.
The reason for the above is obvious: that there should be no room left
between the bond and rail for rust to form. It follows then that a
bond held in position by an independent plug which renders it
necessary for the current to pass from the bond to the intermediate
plug and from that plug to the rail, is not the best form of bond, for
the reason that it presents a double surface on which rust may form.
Figures 11 and 12 show Robinson's bond wires and strips of 1872, Fig.
12 showing the bond soldered to the rail.
In 1876, 7 and 8 he used on various roads in the vicinity of Boston,
the bond shown in Fig. 11. In 1876 he used on the Boston and
Providence road the bond shown in Figs. 11, 13 and 14.
In the form shown in Fig. 13, holes are bored through the upper ends
of the plugs, which were slightly tapering. The wire was forced
through these holes, and the wire and plugs were then soldered
together with hard solder. The plugs being materially larger than the
wire, could readily be driven home with a good deal of force, thus
insuring an excellent electrical connection without endangering the
wire.
[Illustration: Fig. 11.]
[Illustration: Fig. 12.]
[Illustration: Fig. 13.]
[Illustration: Fig. 14.]
[Illustration: Fig. 15.]
[Illustration: Fig. 16.]
In Robinson's British patent No. 3479, of August 29, 1879, aforesaid,
he illustrated the form of bond shown in Figs. 15 and 16, which is an
equivalent of that shown in Fig. 14, used by him in 1876.
Mr. Robinson claimed the bond wire broadly in this British patent, in
the following claims:
10. "The wire A^3 in combination with the rails B^3, B^3, and
securely fastened thereto, for the purpose described.
11. "In combination the wire A^3, the rails B^3, B^3, and the
rivets _a_^3, _a_^3, the whole arranged substantially as described
for the purpose of securing electrical continuity between said
rails."
The above is believed to be the first disclosure of means for
electrically connecting rails by a bond wire in any patent, although
Robinson had disclosed it to various parties, and used it on
installations years before.
On the subject of rail bonding the following bit of evidence may be of
interest:
In a letter dated Baltimore, October 29, 1874, addressed to Mr.
Robinson by Mr. J. H. C. Watts, of Watts & Co., manufacturers of
Robinson's signal apparatus, he says:
"Am afraid your idea of soldering a strip of copper to the rails
will prove very troublesome in carrying out, as it is a most
difficult matter to heat so large a body of iron sufficiently to
make a _sure_ joint such as you require, or that will stand the
jarring of passing trains, &c., to say nothing of sneak thieves
who abound wherever copper is lying around loose. I know however
you scoff at _theory_ so will 'dry up.'"
The electric dynamo of today has removed the above pointed out
difficulty. Bond wires or strips are now welded to the adjacent rails
for the purpose of securing reliable electrical connection between
them. Welding is soldering, according to the definition of the term.
Thus, the Encyclopedic dictionary gives the definition: Solder: "To
unite or cement together in any way. * * * In autogenous soldering the
two pieces are directly united by the partial fusion of their
contiguous surfaces."
Thus, more than thirty years ago Robinson proposed to solder bond
wires or strips to the rails for the purpose of securing good
electrical continuity between the same. But it became necessary to
wait some twenty years for the development of a commercially practical
process for accomplishing this result. This is found in the modern
electric welding process.
Robinson's object was to secure a perfectly homogeneous joint or
connection between the bond and the rail. His invention, in this
connection, consisted in a metallic bond arranged for electrically
connecting adjacent rails of the track and means for forming a
homogeneous connection between the bond and the rails. This embraces
any mode of accomplishing that result. Robinson had simply anticipated
the electric process by some twenty years, but that process now
accomplishes the result in a simple manner impossible thirty years
ago.
The splice bars now welded to opposite sides of street rails in many
places are used primarily for the purpose of electrically bonding the
rails; incidentally they serve the double purpose of also making a
good joint mechanically. Every electric railroad uses the bond wire or
plate in some form, originally invented and used by Robinson, for
electrically bonding rails together.
Thus, it is clear, this simple invention of Robinson made more than
thirty years ago, an outgrowth of his original creation of the closed
rail circuit system, has made possible the electric railroading of
today, and the method of rail-bonding is now used on every electric
railway using a rail return, throughout the world.
[Illustration: ROBINSON'S LATEST ELECTRIC SIGNALING APPARATUS.
Fig. 17.
Rings a Bell on the Engine when Track ahead is all Clear.]
Figure 17 is a reproduction from a postal card dated September, 1875,
and issued at that time. It illustrates means for operating a positive
safety signal in the cab of a locomotive when the track ahead is clear
and safe, the operative current passing through the rails from the
distant end of the track section upon which the train is entering.
This system is elaborated in Robinson's British patent of August 29,
1879, where it is shown operatively applied to a single track in such
a manner as to operate a signal on a locomotive approaching from
either direction, the operative current coming from the opposite end
of the section--no line wires being used.
It is not thought necessary, therefore, to more fully describe the
system here.
In General
The scriptural injunction, "Prove all things, hold fast that which is
good," is the key note of scientific progress. He who would discover
truth must not accept anything _because_ it is popularly accepted, or
reject anything _because_ it is popularly rejected; nor must he regard
anything as impossible _because_ never heretofore accomplished,
although perhaps attempted by the most able scientists. While giving
full weight to principles and laws demonstrated and verified by
original investigations, he must bear in mind that those principles
and laws may be capable of various combinations and interpretations;
that the popular interpretation may not be capable of general
application, and if not, it must be erroneous. In short, he must enter
upon his investigations systematically, independently and untrammeled
by prejudice.
These remarks apply to electrical science with great force at the
present time. Those who enter this field to advantage should be men of
culture, of theoretical knowledge, and eminently practical.
These facts are illustrated by the efforts heretofore put forth in
Europe and the United States to develop systems of rail signaling.
Such efforts, in the early days, appear to have been exerted
principally by theorists whose propositions and complications prove
them to be not only ignorant of some of the fundamental principles of
electrical science, but also, some of them, extremely unpractical.
That the efforts in this direction may be fairly understood we will
direct attention to a few of the systems of rail signaling
proposed,--those which have elicited most attention--giving outline
illustrations of some of the circuits which form their bases, and
pointing out their defects and merits.
Early Rail Systems
So far as we have knowledge, the idea of using the rails as conductors
for electric signaling purposes was first suggested in an English
patent of 1848. This was merely a suggestion, however, and no attempt
was made to describe any specific method of using the rails for the
purpose.
In 1853, however, an English patent was granted to George Dugmore and
George Millward, in which is described a method proposed for using the
rails as conductors. The design of the invention is to communicate
between trains on the same line, and between trains and stations, for
which purpose it is proposed to use long sections of rails. The
unpractical part of this system is that to make it operate it is
necessary, as the inventors say, to insulate the opposite wheels of
all the carriages from each other, in order that electrical connection
may _not_ be established between the opposite rail line by the wheels
and axle.
Imagine one of our gigantic locomotives having its opposite drivers
electrically insulated from one another!
Figure 18 represents the signal system described in William Bull's
English patent of October 31, 1860. In this system, it will be
observed, the rail sections used are short, "twenty feet, more or
less," and are the terminals of line wires which connect with the
battery and magnet at the station. The signal at the station is visual
and consists of an indicator operated by wheel work actuated or
controlled by the electro-magnet M shown in the diagram. The signal as
described, moved in one direction only, by a step-by-step movement.
In the following diagram M represents magnet and B battery.
[Illustration: Fig. 18.
William Bull's British Patent, October 31, 1860, and Frank L. Pope's
Experiment at Charlestown, Mass., in 1871.]
Mr. Bull says: "At the stations at which it is required that the
progress of the train shall be indicated, a battery is fixed and in
connection therewith a dial or indicator, both of which are also
connected with the line permanent way wire, the terminals of which are
the pairs of insulated rails, as before described.
* * * * *
"When the train arrives at the contact points on the line, the
electric circuit would be completed by the wheels of the engine
connecting the two insulated rails, when the current would flow and
actuate the electro-magnetic armature," &c.
The mode of insulating the rails from each other is described by Bull
as follows:--"Between the end of the rails, and also between the joint
plates and rail ends, I insert a thin piece of leather, mill-board,
gutta percha, or other suitable substance, suitable for cutting off
metallic contact, and thereby insulate one rail of twenty feet, more
or less, as may be necessary."
In Pope, in a description of his experiment at Charlestown, in a paper
read by him before the New York Society of Practical Engineers--of
which, by the way, Mr. Robinson was a charter member--and subsequently
published, admits that he did not use the "rail circuit" at all in any
proper sense of the term. On the contrary, he used line wires forming
his main circuit terminating in short sections of rails, forty-two
feet in length according to my recollection, that is, the length of
one rail.
The train passing over the short rail section at one point closed the
circuit through the line wires, thus exposing the signal, which was
held in place by a "detent." The train, having reached a distant
point, passed over another similar short section of rails, closing
circuit through another magnet which released the "detent" and
reversed the signal.
It will be observed that the essential features of the device used in
Pope's experiment, on which he laid great stress, and described in
Bull's patent, are identical, that is, the circuit closer consists, in
the one case of a section of rails "twenty feet long, more or less,"
on open circuit, and the other identically the same, but with a rail
section forty-two feet long, both using line wires.
Pope and his friends heralded this experiment--a revival of Bull's
device--as demonstrating a wonderful invention on the part of Pope.
What Robinson Has Done in Automatic Electric Signaling
1. He has created an epoch making invention of incalculable value to
the human race in the wholesale saving of life and property on
railroads, an invention of increasing importance and efficiency as
time passes and its use is extended.
It is an invention so unique and profoundly philosophical that those
best skilled in the electrical art at the time it was made, declared
that it was contrary to all known laws of electrical action and could
not possibly work.
2. Robinson's invention was not an improvement on something that
preceded it. It had no precedent. It was an entirely new creation
involving principles and methods of operation never before known or
used by anybody.
3. His invention was almost unique in this: It was a basic invention
conceived, tested, put in practical operation in many installations,
and _perfected_, as a system, in all its details, by its original
inventor. He reduced it to its lowest terms and its highest
efficiency, a perfection and efficiency of operation which have not
been exceeded since it left his hands many years ago.
4. His invention has made possible, with safety, the high speed
railroading of today.
5. As already stated, the automatic signal system used in and
controlling the operation of traffic of the New York subway is purely
and exclusively a Robinson system.
6. Robinson's automatic signal system has increased the traffic
capacity of the New York subway at least three-fold, and probably
twice that. Without it the subway equipment could not transport with
safety, one-fourth the number of passengers now carried.
7. This invention has created a practically new industry, giving
employment to many thousands of men, in various capacities, skilled
and unskilled.
8. It is enriching the railroads by enabling them to carry on twice
the traffic, with a given equipment, that they could ever do before,
and also by saving their equipment from destruction by collisions and
other destructive means.
9. The Robinson automatic system is admittedly the only signal system
ever produced that meets all the requirements of safe and rapid
railroading.
10. Robinson's subsidiary invention of the rail bond, made more than
fifty years ago in connection with his automatic system of signaling,
and now in universal use on all electric roads using the track return,
throughout the world, has made possible electric railroading as
practiced today. Without this Robinson bond or its equivalent those
electric roads using the track return could not be operated.
11. The Robinson automatic system is a humanitarian invention of the
very highest order, to which thousands of travelers by rail are
indebted for the preservation of life and limb.
[Illustration: W. ROBINSON.
Improvement in Electric Signaling Apparatus for Railroads.
No. 130,661. Patented Aug 20, 1872.]
UNITED STATES PATENT OFFICE
WILLIAM ROBINSON, OF BROOKLYN, NEW YORK.
Improvement in Electric-Signaling Apparatus for Railroads
Specifications forming part of Letters Patent No. 130,661, dated
August 20, 1872.
Be it known that I, WILLIAM ROBINSON, of Brooklyn, in the county of
Kings and State of New York, have invented a new and useful Electric
Signaling Apparatus for Railways, of which the following is a full,
clear, and exact description, reference being had to the accompanying
drawing forming part of this specification.
The figure represents a top view of a double-track railway, with
suitable sections and wire connections, together with an elevation of
the signal-box with its face removed to show the signal within, the
whole being arranged to illustrate my invention.
The object of this invention is to operate electric signals, audible
or visible, by means of moving or standing vehicles or trains without
the use of ordinary track connections for closing or breaking
circuits, and without the use or with a limited use of line-wires for
conducting the electric current, the rails of the track being used for
the latter purpose. The invention consists in an improved signal of
very simple construction, by which great ease of action is secured. It
also embraces certain peculiarities in the arrangement of wires from
the signal and battery to the track. A in the drawing represents a
double-track railroad. C is a section of track, which may be a mile
long, more or less, and having its rails _a b_ separated from metallic
contact with the rails of the sections D and E, as shown at _a' b'_.
In like manner the section C' of the other track has its rails
separated from metallic contact with the rails of the sections D'
and E'. The rails _a b c d_ should each have metallic continuity
throughout the length of its section. The signal-box F is constructed
of any suitable material, and is provided with an orifice, preferably
in the center, covered with glass windows capable of illumination,
through which the signal may be seen when exposed, day or night.
Within this signal-box is placed the signal G, consisting of a disk,
S, attached to the lever _e_, which, pivoted at _f_, turns on a
horizontal axis. To the lever _e_ or its arbor is fixed the small
projection or lever, preferably segmental, _g_. A cord, link, chain,
or delicate elastic spring, _i_, is attached to the lever _g_ and to
the upper part of the long lever L, in such a manner that when the
armature _m_, which is attached to the lever L, is attracted by its
magnet M and the upper part of said lever L swings in the direction of
the arrow _z_, the upper part of the segmental lever _g_ moves forward
and downward, thus permitting the chain _i_ to work closer to the
pivot _f_. By this arrangement it will be seen that the greatest
leverage-power is secured for moving the signal when the armature _m_
is the greatest distance from its magnet and the magnetic force is
consequently weakest, the leverage-power diminishing gradually as the
armature approaches the magnet. The vertical lever L moves on a
horizontal axis, _f'_, and is prevented from swinging too far back
from the magnet by the adjustable stop _s_, which may be so adjusted
as to bring the armature _m_ a greater or less distance from its
magnet M, as may be found necessary. The levers L and _e_ may be made
of any suitable material and in any manner; but are preferably
constructed of thin tubular metal for the purpose of securing great
strength and rigidity with minimum weight and friction of parts.
Furthermore, the disk S is counterbalanced by an adjustable weight,
_w_, and by making that part of the lever _e_ embraced between the
pivot _f_ and the disk S of considerable length, the disk S is brought
from a state of concealment to a state of exposure, or the reverse, by
passing through a comparatively small angle, and by arranging the
disk-lever _e_, as shown in the drawing, in such a manner that in
bringing the disk from a state of concealment to a state of exposure,
or the reverse, said lever _e_ shall swing to and beyond a horizontal
position, the greatest uniformity of motion with the least possible
loss of power are secured.
Having thus described the construction of the visual signal G, it will
be seen that when the electro-magnet M is charged it attracts the
armature _m_ to itself, thus swinging the upper end of the lever L in
the direction of the arrow _z_, and carrying the upper end of the
lever _g_ forward, at the same time turning the same together with the
lever _e_ on the axis _f_, and carrying the disk S down into the
position indicated in dotted outline. Now connect one pole of the
battery B with the rails _a_ and _c_, and the other pole with the
rails _b_ and _d_ of the sections C and C' by means of the wires _k_
and _k'_, respectively. In like manner connect the ends of the coils
of the magnet M, the one end with the rails _a_ and _c_ and the other
end with the rails _b_ and _d_ of the same sections C and C' by the
wires _l_ and _l'_, as shown in the drawing, and the apparatus is
operative. The wires from the battery and the signal to the track are
preferably insulated.
Before describing the operation of the apparatus as a whole, it may be
stated that the electric current will follow a naked metallic
conductor if of sufficient surface, even when immersed in a river or
in the mud at the bottom of a river, because the metal offers less
resistance to its passage than either water or mud. Much more will it
follow the rails of a railroad track when they are made a part of the
circuit, since the rails present a large surface of good conducting
material, which offers much less resistance to its passage than any
surrounding mediums; and it is well known that when several courses
are presented the electric current will follow that course which
offers least resistance to its passage.
The mode of operation is as follows: Suppose the sections C and C' to
be entirely clear of cars; then the electric current from the positive
pole P of the battery B will pass as indicated by the arrows _x x_,
through the wire _k'_, rail _b_, wire _l'_, and magnet M, charging the
same, and return through the wire _l_, rail _a_, and wire _k_, as
indicated by the arrows _y' y_, to the negative pole N of the battery.
The magnet M, being thus charged, attracts its armature and swings the
signal-disk S into the position of concealment shown in dotted
outline, and holds it in that position as long as the sections C C'
are clear. Now let a train enter upon C or C', as indicated at H C',
and the wheels and axles of the same will bridge over the rails _c_
and _d_, and thus, by offering a large conducting-surface, will
present to the electric current a complete circuit, which offers much
less resistance to its passage than that through the magnet M. The
electricity now takes the course over the wire _k'_, rail _d_, wheels
and axle H, returning, by the rail _c_ and wire _k_, to the battery,
as indicated by the arrows _x x' y_, using the rails _c_ and _d_, as
will be seen, with their bridge, and entirely avoiding the magnet M,
which, being thus demagnetized, lets go its armature, and the
counterpoise _w_, which slightly overbalances the disk S, carries the
same up in front of the orifice, into a position of exposure, where it
remains, as shown, while a train is on section C or C'. When, however,
the train has run off, leaving sections C and C' clear, the magnet M
is instantly charged again and the signal-disk is removed and kept
concealed until the track is again blocked by the presence of another
train, when the same process is repeated. When the signal-disk is in a
position of exposure, as shown, the lever _l_ may serve to close an
additional circuit through the battery B, which may be used to operate
an alarm, I, in conjunction with the signal S, or to actuate another
signal at a distant point. Furthermore, the concealment of the signal
S may serve to close another circuit for exposing another signal, or
the reverse. Instead of using the signal G, constructed as herein
minutely described, a signal of any suitable construction may be used
without affecting the spirit of the invention. Furthermore, instead of
using the magnet M to actuate the signal directly, it may be used as a
relay, operating, when charged, to keep the circuit which directly
actuates the signal open or closed, as desired. It is evident that an
alarm may be used either in conjunction with or independently of a
visual signal. The drawing shows an application particularly adapted
to road-crossing signals on a double track. The signals may be used,
also, on a single track and be applied as block signals and for other
purposes on single or double tracks. When used as a block-signal or
for other purposes, it may be desirable to indicate at a distant
station when the signal is operative. To accomplish this object, carry
one of the wires from the magnet M to the distant station. Here let
the wire be passed through the coils of a bell-magnet or other
signaling device, and thence be carried to the track and attached to
the same, as already described. The office signal will operate
simultaneously with the signal S. Thus any desired number of signals
may be operated simultaneously, at different points, from a single
section of track.
By a slight modification of the plan described an efficient switch and
drawbridge signal may be operated, the rails being used as conductors.
Thus half a mile, more or less, from a switch may be placed a
signal-box and signal, substantially as described, and connected with
the rails, as shown. Near this point let the rails be divided, taking
care that the signal and battery wire are connected to the section
toward the switch. Now, while the switch is on the main line, the bars
connecting the rails of the switch will act as a bridge to divert the
electricity from the signal-magnet. But when the switch is misplaced
the metallic connection of the rails of the track will be interrupted.
The signal-magnet will thus become charged and the position of the
signal changed. In this case the signal should be exposed when the
magnet M is charged. In like manner a cross-bar may bridge the rails
on a draw-bridge. The displacing of the draw-bridge or withdrawing of
the bolt or bolts which hold the same in position will allow the
signal-magnet to become charged and the signal to be changed,
substantially as described, in connection with a switch.
It is not necessary in all cases that the rails _a_ and _b_, section
C, should both be separated from metallic contact with the sections D
and E. It may often, if not always, be sufficient to separate only one
of said rails from such metallic contact with the adjacent sections.
What I here claim as new, and desire to secure by Letters Patent, is--
1. The battery B and magnet M, so connected with the rails of a
section of railroad track that when said section is bridged by the
wheels and axle of a car the electric circuit is changed and the
signal operated through the demagnetization of the magnet M,
substantially as specified.
2. A signal constructed partially of tubular material, for the purpose
of securing lightness combined with strength, in the manner
substantially as herein set forth.
3. The arrangement of the pivotal bearing of the lever _e_ at a point
midway between the horizontal lines of exposure and concealment of the
signal-disk, as shown and described, for the purpose set forth.
4. The combination of the elastic spring _i_, or its equivalent, with
the levers L and _e_ and signal-disk S, substantially as set forth.
5. The battery B, in combination with the wires _k k'_, rails _a b_ of
a railroad track, wires _l l'_, and magnet M, substantially as and for
the purpose herein described.
6. The additional or local circuit _r_, in combination with the magnet
M, wires _l l'_ _k k'_, battery B, and section of rails of a railroad
track, for operation, essentially as described.
WILLIAM ROBINSON.
Witnesses:
JOHN ROONEY,
VAN WYCK FOSTER.
DR. WILLIAM ROBINSON[2]
Electrical and Mechanical Engineer
Fellow American Institute of Electrical Engineers Graduate of Wesleyan
University with Degrees of A.B. and A.M. Post Graduate of Boston
University with Degree of Ph.D.
[2] Reprinted from a circular published by Dr. Robinson in 1913.
Data Notes
Originator and patentee (basic patents, 1872) of the Closed Track
Circuit System of Automatic Electric Signaling, the basis of
practically every automatic electric block signal system in use on
railroads today.
The following brief description and comments on this Robinson closed
track circuit system are from the Third Annual Report of the Block
Signal and Train Control Board to the Interstate Commerce Commission,
dated November 22, 1910, pages 177 et seq.
"The Track Circuit
"Perhaps no single invention in the history of the development of
railway transportation has contributed more toward safety and despatch
in that field than the track circuit. By this invention, simple in
itself, the foundation was obtained for the development of practically
every one of the intricate systems of railway block signaling in use
today wherein the train is, under all conditions, _continuously
active_ in maintaining its own protection.
"In other words the track circuit is today the only medium recognized
as fundamentally safe by experts in railway signaling whereby _a
train or any part thereof may retain continuous and direct control of
a block signal while occupying any portion of the track guarded by the
signal_."
"Invention of the Rail Circuit
"To Mr. William Robinson the Patent Office records concede the honor
of having devised the first practical track or 'rail circuit.' This
comprised what is termed the _closed_ track circuit in distinction
from the _open_ form that preceded it." * * *
"Closed track circuits are very reliable, wholly safe in principle,
and simple of application and maintenance."
* * * "Attention is therefore directed to the closed track
circuit--the basis of all modern automatic signal systems that are
entitled to recognition as embodying the highest attainments in the
matter of safety."
"The Closed Track Circuit
"The closed track circuit in its simplest form consists of the two
rails of a section acting as prime conductors, a generator maintaining
a difference of potential between them when the rails are unoccupied,
and one or more relays connected across the rails."
* * * "The closed track circuit maintains the relay, normally, in
an energized state, and the influence of the train upon the rails
is to totally de-energize it by shunting or short-circuiting the
generator--a thing as effectively done by a single car or locomotive
as by a train of any length, for all practical purposes."
* * * "A failure of the generator or a break in the circuit, whether
in the rails themselves or in other parts of the circuit, produces the
same effect upon the relay as that of a train upon the rails.
"This is in full conformity with the accepted principles of safe
signaling, which give heed not alone to the action of the devices of
the system under normal conditions, but _embrace also an equal
regard for safe results following derangements of them_."
Historical Notes
In this connection a few historical notes on the origin and
introduction of the closed rail circuit system of automatic electric
block signaling on railroads may prove of interest.
In 1870 Mr. William Robinson exhibited at the American Institute Fair
held in New York City, an elaborate working model of an automatic
electric signal system for railroads. This was a road crossing signal
operated by trains approaching in either direction. When at a suitable
distance the train set a gong ringing at the road crossing ahead,
which continued sounding an alarm until the train had passed, when it
ceased ringing. In this model the relays were de-energized by short
circuiting, although the signal was operated on the normally open
circuit plan. This is believed to be the first case in which
short-circuiting had been used in the operation of railway signals.
In 1871 Mr. Robinson installed this system as an automatic block
signal on a block over a mile in length, at Kinzua, Pa., on the
Philadelphia and Erie Railroad. This installation embodied a relay, a
large visual signal under control of the relay, a heavy electric gong
operated in conjunction with the visual signal, all at the signal
station. From this station an overlap extended to the agent's station
a mile ahead. Here a signal bell was provided so that when the visual
signal was actually in the danger position it closed circuit on the
bell magnet in the agent's station, the hammer remaining against the
bell until the reversal of the distant signal opened the circuit of
this check signal.
This system worked perfectly, performing all claimed for it; but it
was a normally open circuit system, the only principle ever dreamed of
up to that time for operating an automatic electric railway signal.
Immediately on the completion of this open circuit installation Mr.
Robinson began to look for weak points about it, and soon discovered
several now well known as inherent in all normally open circuit
systems, not the least of which was that if the circuit were broken or
the current failed from any cause the signal would remain at safety,
thus showing a false signal although danger might be imminent, a
radical error in principle fatal to the reliability of any normally
open circuit system of signaling.
He therefore, after much study, devised the closed track circuit
system, the construction and operation of which are clearly described
above by the Interstate Commerce Commission.
In devising this system Mr. Robinson reasoned that to make an
efficient and reliable system every pair of wheels in the train must
control the signal, whereby a single car on the block, or a break in
any part of the circuit, or loss of current from any cause affecting
the relay, would keep the signal at danger as effectively as the
presence of a whole train on the block.
These considerations led him to the invention of the closed track
circuit operating as heretofore clearly described by the Interstate
Commerce Commission.
Before making tests of the system, however, he applied for and was
allowed basic patents on the closed track circuit system in the United
States and France, the United States patent dated August 20, 1872, No.
130,661, and the French patent February 29, 1872, No. 94,393.
Having all the signal apparatus in operation at Kinzua, in the open
circuit system, as above described, it was a simple matter for him to
test the closed circuit system at this point. He therefore divided the
opposite rails of the track into sections insulated from the adjacent
continuous track rails and connected the relay terminals to these
sections at one end and similarly connected a battery thereto at a
suitable distance from the relay, thus forming a closed track circuit.
This being done, the first train that passed connected the opposite
rail lines through the wheels and axles, short circuited the relay,
thus operating all the signal circuits under its control, thereby
practically demonstrating the feasibility of the system. This was in
1872. This block was extended to the agent's station over a mile from
the signal, at which station the track battery was placed and also a
switch for the manual operation of the signal, and also an overlapping
telltale signal showing to the agent when the distant main signal was
actually exposed at danger. The signal also indicated to the agent the
approach of a train when a mile away.
Another installation was immediately ordered to be made at Irvineton
on the same road. This was completed early in 1873 and worked
perfectly from the beginning, performing all the functions described
in connection with the installation at Kinzua. The locomotive
engineers were greatly interested and soon christened the Irvineton
signal "The Old Reliable." This was followed by other installations on
this road and in 1873 Mr. Robinson had made installations of his
closed rail circuit system of signaling on four different railroads,
followed by various installations on many other railroads in the
following years, as he was the sole owner of the system for about nine
years, that is, until about 1880 or 1881, when the Westinghouse people
obtained control of the system by the purchase of Robinson's
interests. This was promptly followed by a reorganization under the
name of the Union Switch and Signal Company, the terms "Union" and
"Signal" representing the Robinson interests in the reorganization.
This company thus became the sole owner of the Robinson Closed Circuit
System of signaling until the expiration of his patents, when all
other signal companies adopted the Robinson system as the basis of
their signal work.
The original name of the Robinson Company was _The Union Electric
Signal Company_, which Robinson organized and owned in 1878. In the
reorganization the word "Electric" was canceled from this title and
the words "Switch and" substituted, thus forming the present title:
"_The Union Switch and Signal Company_."
Rail Bonding
Experience at Kinzua with a very poor track demonstrated the necessity
of a rail bond to secure reliable electrical continuity throughout the
rails constituting the block. Here, in 1872, Mr. Robinson conceived
the invention of the bond wire as used today.
In an effort, however, to avoid the handicap of having to bore two
holes in every rail of long sections of track, he equipped a signal
section in 1873 with elastic steel plates bearing on the adjacent
rails at the joints. This did not prove as satisfactory, however, as
the bond wire. He therefore used bond wires made after his original
conception, on every installation he made after 1873.
He made his bond wire in two forms. In the second form he made studs
slightly tapering, bored holes through them, inserted the ends of the
wire in these holes, brazed them together and drove these studs
securely into holes bored in the adjacent rails. An examination of
these bonds after several years' service showed that they were
apparently in as good condition mechanically and electrically as when
first put in place.
The Rail Bond is now an essential basic feature of practically every
one of the electric railway systems now in operation, since they all
use the track for a return, and the track rails must be securely
bonded in order to insure indispensable electrical continuity of the
circuit.
In addition to his signal system, therefore, Dr. Robinson is clearly
entitled to the credit of having made, before the inception of
electric railroading, a simple basic invention in his bond wire, which
has made modern electric railroading possible, an invention
indispensable to the successful operation of electric railroading as
practiced today.
This invention has saved the electric roads untold millions of dollars
and enabled them to accomplish results in a simple manner which could
not otherwise be as well secured at any cost, by the only alternative
method, of running return contact conductors in the air.
WILLIAM ROBINSON.
[Illustration: WILLIAM ROBINSON, PH.D.; E. & M.E.
Original inventor and patentee of the Automatic Electric Signal
Systems now in use on the leading railroads in the United States and
Foreign Countries.]
DR. ROBINSON'S RECORD FROM WESLEYAN UNIVERSITY
William Robinson, B.A., 1865; M.A., 1868, Alpha Delta Phi. Ph.D.
Boston University, 1907. Born November 22, 1840, in Ireland.
Principal of High School, Ansonia, Conn., 1865-66. In the oil region,
Pennsylvania, 1866. Taught in Stamford, Conn., 1867. Principal of
Spring Valley Academy, N.Y., 1867-69. Engaged in the oil business in
Pennsylvania, 1869-72. President and General Manager of the Robinson
Electric Railway Signal Company, 1873. Engaged in business in Boston,
Mass., 1875-81. Organized the Union Electric Signal Company, 1878.
Traveled in Europe, Egypt and Palestine for fifteen months, 1879-80.
Inventor of the Robinson wireless electric railway signal system, of
the Robinson radial car truck, of the coaster brake used on bicycles,
of roller bearing skates, and of a repeating telephone. Engaged in
developing and practising electric engineering. Author: History of
Automatic Electric and Electrically Controlled Fluid Pressure Signal
Systems for Railroads.
Died January 2, 1921, Brooklyn, New York.
A.I.E.E. RECORD OF DR. WILLIAM ROBINSON
Copy of Dr. Robinson's record made from original application No. 1265
to the American Institute of Electrical Engineers, 33 West 39th
Street, New York City. (Record filed July, 1909.)
References given by Dr. Robinson:
William B. Potter.
E. W. Rice, Jr.
Theodore Stebbins, Dallas, Texas.
Frank J. Sprague, 165 Broadway.
Prof. Chas. A. Cross, M.I.T.
Prof. Elihu Thomson.
Goss & Bryce, Mech. Eng., 76 William Street.
George L. Fowler, Cons. Eng., 53 Broadway.
Wm. Wallace White, Foreign Patent Solicitor and Consul, 309 Broadway.
WILLIAM ROBINSON (A.M., PH.D.)
ELECTRICAL AND MECHANICAL ENGINEER
Born November 22, 1840, North of Ireland, of Scotch-Irish descent on
paternal side and English on maternal side.
ELIGIBLE FOR TRANSFER: Under clauses (a) and (c).
EDUCATION: Graduate of Wesleyan University, full Academic course,
receiving the degrees of A.B. in 1865 and A.M. in 1868.
Post-Graduate of Boston University in 1907, with degree of Doctor of
Philosophy; course including Electrical and Mechanical Engineering.
OCCUPATION AND WORK DONE: Engaged in developing and practising
electrical engineering from prior to 1870 up to the present time
(1909).
Original inventor and patentee of the automatic electrical and
electrically controlled fluid pressure signal systems for railroads
now in universal use on the leading railroads in the United States and
foreign countries, wherever and by whomsoever installed, throughout
the world.
1870. Received four United States patents on this system; applications
filed earlier.
1870. Exhibited an elaborate working model of the system at the
American Institute in New York, showing the automatic signal system in
operation under control of passing cars.
1871-2. Original inventor and patentee of the closed track circuit
system of signaling. Received basic United States and French patents
covering same, in 1872. Applications filed, 1871.
1870-71. Original inventor and patentee of the automatic
electro-pneumatic signal systems for railroads in use for many years
past. Received basic British patent covering this system in 1871. So
far as I have been able to ascertain on careful investigation, this
patent appears to be the first ever issued anywhere on this subject.
The following brief historical excerpt is taken from a United States
patent granted to me on October 20, 1908, No. 901,383, on an electric
railway system. This patent is one of a bunch of eight taken out by me
on the same date, on the same subject. The excerpt relates to my work
in signaling.
"The block signal system herein disclosed is an embodiment of the
Robinson electro-pneumatic system now in extensive operation on
the Pennsylvania railroad and many other leading railroads in this
and other countries, embodying the closed circuit rail system for
which a basic U.S. patent was granted to me on August 20, 1872,
No. 130,661 (reissued July 7, 1874), the electro-pneumatic signal
system disclosed in my British patent of August 30, 1871, No.
2280, the subject matter of both of which patents is disclosed
in my French patent of February 29, 1872, No. 94,393. The
electro-pneumatic signal system disclosed in the above named
patents is also disclosed in my United States patent dated
November 7, 1882, No. 267,259. As above indicated the block signal
system herein described comprises the system described in my above
named patents and now in general use on leading steam railroads,
but modified and improved in a way adapting it for reliable and
efficient use in connection with electric railroads of the
sectional third rail type."
The admission of the above brief history in the above described, and
substantially in two other patents of the same date, is, of course, a
complete verification of its historical accuracy by the Patent Office.
1872. In 1872 I put the closed track circuit system of signaling in
practical and successful operation at several points on different
divisions of the Philadelphia and Erie railroad, and on other roads.
1872-79. In 1872 to '79 I installed the closed circuit rail system of
automatic signaling on various railroads in Pennsylvania, New England
and elsewhere. I perfected the system and put it in as perfect and
efficient and durable operation at that time as it is in today,
including all its functions of block, switch, road-crossing,
overlapping, rear and front, tell-tale and broken rail detector.
1878. Organized and owned the Union Electric Signal Company, based
solely on my signal patents, at that time nine in number. Some time
afterwards George Westinghouse and his associates bought the
controlling interest in the Union Electric Signal Company and
reorganized the company under the name of the Union Switch and Signal
Company. Thus, the automatic signal system of the Union Switch and
Signal Co. consists, in every essential particular, of the Robinson
system, pure and simple.
It may be here pointed out that all the railway signal companies now
in operation, installing automatic signals under whatever name, are
using the Robinson system bodily, and have been since the expiration
of Robinson's basic patents. There is no other system, as a system, in
use.
HISTORY: Several years ago I published a "History of Automatic
Electric and Electrically Controlled Fluid Pressure Signal Systems for
Railroads," the only authentic history ever published on the subject.
This was written and published at the instance of engineering friends,
in the interest of indisputable historical accuracy.
Telephone Experiments
1876. As a matter of more or less interest I may here state that I
carried on a conversation by telephone, in 1876, through a railroad
track, the circuit consisting of the two rail lines constituting a
closed circuit signal block.
1877-8. Delivered numerous illustrated lectures on the telephone, and
at this time discovered the principle of the wireless telephone and
actually transmitted speech clearly back and forth across an open
space of several inches to and from a telephone having but one
terminal grounded and the other free in the air. The free, uninsulated
wire (except at supports) extended several hundred feet through the
air. The instruments used were large magneto telephones of my own
special designing, and made by me for the special purpose of
illustrating lectures. No battery was used.
Electric Railway Systems
Outside of automatic signaling I have done considerable work along
original electrical lines.
In addition to other work of importance I have for more than fifteen
years devoted much time to developing a radically new departure in
electric railroading.
On this system I have applied for more than twenty patents, extending
over a series of years, fourteen of which patents have already been
issued.
What This System Accomplishes
1. The third rail or contact conductor is made in sections or blocks
of any desired length, which sections are normally dead but become
automatically alive when a train enters thereupon, and dead when the
train leaves the section.
2. When a train enters upon a section or block it prevents the section
back of it from receiving working current. Thus any number of trains
following each other will each be deprived of working current when the
length of a block back of the train ahead of it, whether that train be
running or standing still, thus preventing collisions.
3. A train approaching a switch or drawbridge is automatically
arrested the length of a block away from the block containing the
switch or draw before a bolt can be withdrawn or a lock released in
the latter.
4. No possibility of interference between a possible wandering
propulsion current and the functions of any other current.
5. All currents used may be of the same or have any combination of
different characteristics.
The system is elaborate, providing for safety on and off the trains,
economy of current, simplicity and certainty in action, dispenses
largely with electrolytic action, and when alternating propulsion
current is used the return is confined to the length of the block. It
is believed that the system will prevent all danger to passengers and
trains from the direct action of the propulsion current.
President Roosevelt called the attention of the Interstate Commerce
Commission to my electrical and mechanical inventions for making
railroading safe.
Mechanical Engineering
I have done considerable original work in mechanical engineering.
In this connection I may mention the well known Robinson Radial Car
Truck, which is in quite extensive operation on electric railways.
This is the only car truck, I believe, ever designed and constructed
on correct mechanical principles. It is so constructed that every axle
in the car or train becomes exactly radial to any curve around which
it passes, all the axles becoming parallel on straight lines only.
This prevents wear and tear and grinding and derailment on curves. It
also greatly economizes current.
One of these radial cars, in St. Louis, having a 28-ft. body,
exclusive of platforms, equipped with a radial truck having a 15-ft.
wheel-base and two motors, stopped in the middle of a street corner
curve and started with the same power as on a straight line, as shown
by careful tests with volt and ammeters. The test was made by
officials of the company without my knowledge at the time. I believe
this is the coming truck for electric locomotives.
(I forward by same mail a catalogue of the Robinson Radial Car Truck,
fully illustrated, for the information of the Board.)
Coaster Hub
I am also the inventor of the back pedal braking and coasting bicycle
hub, which has been in general use for many years. My application for
a basic patent covering this hub has been pending in the Patent Office
for twelve years, held back nine years by interference litigation in
the Patent Office, owing to an effete interference system which has no
apology to offer to justify its existence.
Turbine Engines
In turbine engines I have made some important improvements.
In one the engine is reversible by the movement of a single lever in
either direction.
In a second the steam is utilized a second time under conditions
doubling the original efficiency, and balancing the end thrust
perfectly.
In a third improvement the engine develops more than three times as
much power as any other turbine of its class occupying the same floor
space. Patents allowed but not yet issued.
I figure that ocean steamers should furnish a large field for these
machines.
Respectfully submitted,
(Signed) WILLIAM ROBINSON.
276 Stuyvesant Ave., Brooklyn, N.Y.
Part II
WILLIAM ASHBRIDGE BALDWIN
The progressive ideas of William Ashbridge Baldwin were responsible
for the first tests of the closed track circuit under actual operating
conditions. It was through his confidence in this invention of Dr.
William Robinson that the possibilities of the application of the
closed track circuit to the safety of train operation was proved. Mr.
Baldwin, at the time the first signal installations were made at
Kinzua, Pa., and Irvineton, was general superintendent of the
Philadelphia and Erie, now part of the Northern Grand division,
Central region, Pennsylvania System, and because he made possible the
development of signaling to its present standard by his interest and
active co-operation in the 70's in making train movements safer, it is
but fitting that he should be given a place in the memorial to Dr.
William Robinson.
[Illustration: _Tracks and Location of Electric Signals Dr.
Robinson's Patent Kinzua Pa. 1872-1873._]
[Illustration: _Tracks and Location of Electric Signals Dr.
Robinson's Patent Irvineton 1872-1873._]
Before stating Mr. Baldwin's railroad activities it will be well to
describe briefly the way in which he became interested in Dr. Robinson
and his work. Dr. Robinson shortly after being graduated from college
began work on a signal system to prevent train accidents which were of
numerous occurrence, and made a model of his open wire system which
was exhibited at the fair held by the American Institute of Electrical
Engineers in New York in 1870. At the close of the fair, he sent out
circulars to officers of various railroad companies explaining his
system. The one received by Mr. Baldwin interested him to such an
extent that he arranged for Dr. Robinson to make an installation at
Kinzua, Pa., in 1870. This installation was of the normally open wire
circuit controlled by track levers. After the installation, Dr.
Robinson seeing that it had many serious defects began studying how to
correct them. This was accomplished by the invention of the closed
track circuit. He then exhibited his closed track circuit system of
signaling at the State Fair held at Erie, Pa., in 1872, where he had
his track circuits operating under water in a long tank. Dr. Robinson
had previously explained the principles of the closed track circuit to
Mr. Baldwin who requested him to make such an installation at Kinzua,
Pa., in place of the open wire circuit. After this was in service, Mr.
Baldwin ordered another installation to be made at Irvineton, Pa., and
because of the good service rendered, this signal soon came to be
called the "Old Reliable" by the locomotive enginemen. (A picture of
this signal appears in Part I.)
Old Employees Describe First Installations
Through the courtesy of A. J. Whitney, general superintendent,
Northern Grand division, Central region, Pennsylvania System, and A.
H. Rudd, chief signal engineer of the Pennsylvania System, the
following information was developed from interviews with Wm. Metzger,
88 years old, of Irvineton, Pa., once an engineer on the Philadelphia
& Erie; Associate Judge J. W. Hughes, of Warren, Pa., formerly yard
master at Irvineton; John Christie, car inspector at Irvineton, and J.
C. Curtis, formerly a train dispatcher on the Renovo division. "About
1872, Dr. Robinson, who probably came from Altoona, erected a signal
governing westward movements, near Irvineton. This signal was located
just west of Irvine Run bridge, on the north side of the main track
(this track is now an eastward track), in a small frame building
adjacent to the track and was electrically operated back of a circular
opening about two feet in diameter, by display of a red flag during
the day and a light in the rear of the flag by night. A bell was also
located in the signal shanty and another bell in the telegraph office
of the station, located at the junction of the two railroads (see
sketch). A trip device, operated by the wheel flange, forced contact
with wires carried on the telegraph poles and operated the signal and
bell in the signal shanty as well as bell in the telegraph office. The
signal was known as the "Old Reliable" and the words "Dr. Robinson's
Patent" were painted around the circular opening.
"Another pair of signals was installed by Dr. Robinson at Kinzua, now
Ludlow, for protection of trains stopping at Kinzua (Ludlow) station.
These signals were operated by overhead wires as at Irvineton. When a
train was opposite one of the signals, it set both signals to red
indication by operating a red flag within a circular opening in the
daytime and a light in the rear of the flag at night. A loud gong was
also installed in each shanty which rang coincident with the signal
going to the red indication. When the rear of the train passed the
signal in advance both signals returned to clear and the bells stopped
ringing. This system was operated with batteries and was removed in
less than a year on account of the difficulty of maintaining the
batteries."
Biographical Sketch of W. A. Baldwin
The biographical sketch of Mr. Baldwin, as given below is taken from
the Biographical Directory of the Railway Officials of
America--Edition of 1906.
BALDWIN, WILLIAM ASHBRIDGE, president, Cleveland & Marietta Ry.
Office, Pittsburgh, Pa.
Born June 28, 1835, at Philadelphia, Pa. Entered railway service
November, 1851, as chainman, engineer corps, Coal Run Road, in
Schuylkill county, Pennsylvania, since which he has been
consecutively, March, 1852 to 1854, assistant engineer on the same
road; 1854 to March, 1857, leveler and topographer, Lackawanna &
Bloomsburg Road; March, 1857, to December, 1858, assistant engineer,
leveler and topographer, Honduras Inter-Oceanic Road, at Honduras,
Central America; December, 1858, to November, 1859, clerk to
superintendent, Western division, Pennsylvania; January, 1860, to
February, 1862, assistant engineer, Pennsylvania; February 7, 1862, to
March 13, 1868, superintendent, Western division, Philadelphia & Erie
(Pennsylvania, lessee); March 13, 1868, to May 7, 1870, assistant
general superintendent, same road; May 7, 1870, to October 1, 1873,
general superintendent, Philadelphia & Erie division, Pennsylvania;
October 1, 1873, to September 1, 1881, general superintendent, same
division, same road, and S. & S. divisions, Northern Central Ry.;
September 1, 1881, to May 1, 1882, manager, Pennsylvania Co., and
Pittsburgh, Cincinnati & St. Louis Railway Lines; May 1, 1882, to
March 31, 1888, manager, Pennsylvania Co.'s lines; April 1, 1888, to
April, 1892, vice-president and general manager, Buffalo, Rochester &
Pittsburgh; November, 1893, to date, president, Cleveland & Marietta
Ry.; November, 1893, to December 31, 1899, also general manager same
road. Retired from that road on April 30, 1906, at the age of 70
years, under the pension rules of the Pennsylvania Lines West of
Pittsburgh, of which the Cleveland & Marietta was a part.
Mr. Baldwin died on February 17, 1911, at Sewickley, Pa., at the age
of 75. His obituary, as appearing in the _Railway Age_ for February
24, 1911, appears below.
"WILLIAM ASHBRIDGE BALDWIN, former president of the Cleveland &
Marietta, which is now a part of the Pennsylvania System, died in
Sewickley, Pa., February 17. Mr. Baldwin was born on June 28,
1835, at Philadelphia, and began railway work in November, 1851,
with a party of engineers making surveys in Schuylkill County, Pa.
In March, 1857, he went to Honduras, Central America, as assistant
engineer, leveler and topographer on the Honduras Inter-Oceanic
Railway. In December of the following year he returned to this
country and entered the employ of the Pennsylvania Railroad. In
1862 he was appointed superintendent of the Western division of
the Philadelphia & Erie. By May, 1870, he had become general
superintendent of the Philadelphia & Erie division, and in
September, 1881 he was appointed manager of the Pennsylvania
Lines West of Pittsburgh. In 1888 he went to Buffalo, Rochester
& Pittsburgh as vice-president and general manager, but five
years later he returned to the Pennsylvania System and was made
president of the Cleveland & Marietta."
Part III
THE TRACK CIRCUIT
"Perhaps no single invention in the history of the development of
railway transportation has contributed more towards safety and
despatch in that field than the track circuit. By this invention,
simple in itself, the foundation was obtained for the development of
practically every one of the intricate systems of railway block
signaling in use today wherein the train is, under all conditions,
_continuously active_ in maintaining its own protection.
"In other words, the track circuit is today the only medium recognized
as fundamentally safe by experts in railway signaling whereby _a
train or any part thereof may retain continuous and direct control of
a block signal while occupying any portion of the track guarded by the
signal_."
"To Mr. William Robinson the Patent Office records concede the honor
of having devised the first practical track or 'Rail circuit'. This
comprised what is termed the _closed_ track circuit. * * * Closed
track circuits are very reliable, wholly safe in principle, and simple
of application and maintenance."
The above paragraphs, quoted from the third annual report of the Block
Signal and Train Control Board to the Interstate Commerce Commission
under date of November 22, 1910, ably express in a few words what the
invention of the track circuit has meant to the railroads of this and
other countries. In order, however, that those who are not familiar
with the principles of the track circuit may have some general
knowledge of them, a simple, non-technical description is given, as
prepared some years ago by Mr. J. P. Coleman, of the Union Switch &
Signal Company.
Historical information on the development and use of direct current
and alternating current track circuits for roads using electricity for
propulsion purposes and those using steam will be found in a report on
this subject made by Committee X to the Railway Signal Association in
1910.
The Rail Circuit Principle
By J. P. Coleman.
Assuming that it is clearly understood that the current is generated
at the battery; that it flows from thence through the conductors (of
which the coils of the magnet form part) and back again to the
battery, and that the magnet is simply a device interposed in the
circuit for the purpose of transforming electrical energy into
mechanical (magnetic) energy, and that the latter can exist in an
electro-magnet only with the presence of the former, we are now
prepared to make clear the principle of an electric track section.
To assist in this, let us state an invariable law governing the flow
of currents: _If two or more paths be presented an electric current,
it immediately becomes divided, and flows in each in quantities
directly in proportion to the conductivity of each._
The unit of electrical resistance, whereby the comparative merits of
various materials and sizes of materials as conductors are designated,
is called an _ohm_, (just as the unit of lineal measurement whereby
the comparative lengths and sizes of various objects are designated,
is termed a _foot_) and we will therefore use that term in reference
to the resistance of a conductor.
[Illustration: Fig. 1]
Figure 1 represents an ordinary gravity battery, the conductors from
it, and the electro-magnet to which they connect; also the armature as
attracted by the magnet and overcoming the spring which tends to
withdraw it from the magnet.
Now, as long as the current flows through the magnet, this condition
of things remains unaltered; but let a second path be presented to the
current several hundred times less in resistance than the original
one, and the result is that several hundred parts of the current will
leave the magnet for the "short circuit," and consequently leave so
little remaining in the original one that the effect will be
practically to demagnetize the magnets.
[Illustration: Fig. 2]
Figure 2 will render this very apparent if we will assume the wire of
the magnet R to possess a resistance of 10 ohms, and the conductors
themselves a resistance so low as to be inappreciable and unworthy of
consideration.
[Illustration: Fig. 3]
[Illustration: Fig. 4]
Now, assume the current to be flowing and the magnet to be charged,
and let us take a piece of metal which has an electrical resistance of
1/100 of an ohm, and lay it across the conductors at any point between
the battery and the magnet. The result is, that instead of flowing
through 10 ohms resistance _via_ the magnet, it follows the invariable
rule, and takes that offering but 1/100 of an ohm; or, more to the
point, if we assume the conductors referred to to be one mile of steel
rails each (Fig. 3), and again leave their resistance (which would be
about one ohm each) out of consideration entirely, leaving that of the
magnet as first stated, and assume the bar of 1/100 of an ohm to be an
axle and pair of wheels (_a_) of a train (Fig. 4), which possess the
same resistance, we can readily see that the result would be exactly
the same, _i.e._, instead of all the current passing through the
magnets, as when the rails were unoccupied, the presence of the wheels
upon them would cause 999/1000 of the current to leave the magnet and
pass through _them_; they offering but 999/1000 of the resistance of
the magnets, and thus leaving but 1/1000 of the whole current passing
through them, which being so small a part of so feeble a current is
imperceptible and without sufficient influence to hold the magnet
charged. Therefore, it follows that the instant that a pair of wheels
enters upon a pair of rails which thus form part of the conductors of
an electrical current holding charged a magnet, that magnet becomes
practically demagnetized, and consequently loses all power to overcome
any opposing force in its armature.
When the armature of a magnet is arranged upon a small lever, by
motion of which a second circuit is closed or opened, or two or more
circuits are otherwise controlled, the entire device is termed a
relay. In all forms of this instrument, as is the case with almost
every other electrical instrument, the armature is so arranged as to
fall by gravity, or by tension of a small spring suitably arranged,
away from the cores of the magnets when they become demagnetized.
[Illustration: Fig. 5]
When switches are included in a track section (Fig. 5), it becomes
necessary for safety to have them control the track section in such a
way that unless they are properly set (and locked, if desired) for the
main track, the continuity of the rail circuit is interrupted and the
signal is thereby held at danger. To render more certain this result,
the circuit controller (switch box) at the switch is arranged in such
a way that the track circuit is not only interrupted beyond the
switch, but is also short-circuited by it when the switch is not
properly set. It is also necessary for safety that the side track from
the switch points back to the fouling point (Fig. 5) be included in
the track section: thus insuring that all trains on these tracks are
out of danger of collision with the main track when a "clear" signal
is displayed on it.
In dividing tracks into distinct electrical sections, it becomes
necessary to insulate the rail ends at the terminal of each, from
those of the adjacent sections. If this were not done the current of
each section would traverse the next, and continue on indefinitely,
influencing each other so as to interfere with or totally prevent the
operation of all.
In order that we may fully comprehend the nature of an insulation, let
us make clear a few facts concerning conductors in general. All
materials conduct electricity to a certain extent; but some with much
more freedom than others. Thus, silver, copper, gold, zinc, platinum,
iron, steel, mercury, and other pure metals permit the passage of an
electric current through them with but slight resistance, (although
all offer a certain amount,) and are therefore termed _conductors_.
The following liquids are classed as conductors: concentrated and
diluted acids, saline liquids and water, although they are much less
efficient as such than the metals.
To this list might be added the earth itself and the various
ingredients forming it, the nature of which ingredients determines
very much its efficiency as a conductor. Thus at points abounding in
mineral deposits the earth would be far superior as a conductor to
those parts in which none exist, but at best should be regarded as a
poor conductor.
Next comes a class of materials which offer a great resistance to the
current, and which from that reason are termed non-conductors, or
insulators; of this class, rubber, glass, leather, resin, wood,
brimstone and dry air are the most common.
Wood being a non-conductor, it is very evident that the cross-ties
under the steel rails form an insulation between them and the ground;
also, that if a piece of the same or similar material be placed
between the rail ends, and that if two other pieces of sufficient
strength be substituted for the iron fish-plates at that point, a
secure insulation will be formed between the rails.
It is precisely in this way that the insulation of one rail from
another is effected (Fig. 6) and the long, practical use of many
hundred joints of this sort, has proved it to be a method both
economical and thoroughly efficient.
[Illustration: Fig. 6]
A much more secure _joint_, however, is obtained by insulating the
existing iron fish-plates from the rails by means of heavy fiber
plates, and their bolts from the rails by fiber bushings (Fig. 7).
While this method is superior to the first mentioned one in that it
makes a more secure rail joint, it is no more efficient as an
insulation.
[Illustration: Fig. 7]
One would naturally suppose that owing to the large surface of contact
existing between the rails and their connecting or fish-plates, and
from the apparent security of that contact obtained by the bolts
through them, no trouble would be experienced by the current in
passing from one rail to the other. This, however, is not the case, as
the bolts and even the plates themselves frequently become loose, even
when provided with the best of nut locks, and the rust and dirt
settling between them and the rails oftentimes increase the resistance
of a track section to a serious extent. Again, even when tightly
bolted and locked, these plates form but an imperfect contact, owing
to the scale or rust upon them. Therefore, to insure that the
resistance of a track section may be as low and as constant as
possible, we have found it absolutely necessary to connect each two
adjacent rail ends together by means of a short piece of very strong
wire (Fig. 8).
[Illustration: Fig. 8]
These wires are termed "track wires" (bond wires) and are provided
with a button-head rivet at each end, which is securely soldered
thereto, for the purpose of securing them to the rails. (Bond wires
are now attached to the rails by channel pins or are welded on.) The
connections from the rails to the battery and relay of a track section
are secured to the rails in the same manner. The battery is usually
located in a chute or well sunk in the ground at the terminal of each
section, which is provided with an elevator in which the battery is
placed and by which it may be raised and lowered at will. All wires
when placed underground are run in grooved lumber in order that they
may be secure from injury.
Even in very wet or snowy weather a single jar of gravity battery is
generally found to furnish sufficient current to properly work the
relay at the other end of any section less than three-quarters of a
mile in length; although it frequently happens on longer sections and
occasionally on those of ordinary length that two jars are necessary.
A greater number of jars is never advisable since by increasing the
intensity of the current, the liability of its leaking from one rail
to the other during wet weather is correspondingly increased, and as
this is attended with some uncertainty in the working of the relay of
the section--due to the varying intensity of the current--it should be
carefully guarded against. As two jars of gravity battery are not
sufficient to operate a signal, lock, bell or any similar instrument
with any degree of certainty, it becomes necessary to have a second
set of batteries of a greater number of jars for that purpose. The
armature of the magnet controlled by the track section is therefore
made to control a second circuit using a battery of this sort (Figs.
3, 4 and 5) and which includes the magnet of the signal mechanism. The
use of a relay on a track section is therefore necessary; and when it
becomes necessary to control two or more devices, each requiring
independent circuits, by one track, the use of a relay is
indispensable.
Track Circuit Characteristics
While the fundamental principles of the track circuit are the same
today as they were when it was originally invented by Dr. Robinson in
1872, it has been found that it is not as simple a device as was
formerly supposed to be the case and many problems have arisen which
have required and is requiring the careful study of the signal
engineers. Accordingly, it is well to present briefly some of the
track circuit characteristics as they are known today. In the
following presentation, information has been collected from many
different sources, including abstracts from papers presented on the
track circuit by Mr. A. R. Fugina, signal engineer, and Mr. J. B.
Weigle, signal inspector on the Louisville & Nashville.
There are two general classes of track circuits, direct current and
alternating current, which may be further subdivided between single or
double rail circuits. The essential feature of the track circuit is
the insulation of each section of track from the adjoining sections.
Each rail in the section is connected to the one adjoining by bond
wires, for the purpose of making a continuous conductor from one end
of the section to the other.
Rail Bonding
Under the present methods of bonding, the angle bar carries the
greater part of the current, and bond wires frequently carry as little
as 20 per cent. of it and sometimes even less. The rail resistance is
lowest with new rails, but it gradually gets higher, due to rust and
dirt formations between the angle bar and the rail. But even with new
rail, the rail resistance varies greatly at different periods and even
at different times during any twenty-four hours. This variation is
entirely due to the fact that the angle bars carry more of the current
than the bond wires, and that the bond wires under any condition are
only large enough to carry the smaller part of the current from the
battery. The lower the resistance of the bonds the less variable will
be the rail resistance.
The resistance of the angle bars increases greatly as rail resistance
increases, as a result of which the angle bars rapidly carry less of
the current.
It is not infrequent to find the rail resistance to be as high as 0.20
ohms per 1,000 ft. of track, and we have known it to run as high as
0.264 in new rail, where especial attention had been given to
obtaining as good bonding as possible. Under such conditions the angle
bar carries very little of the current, the capacity of the bond is
not sufficient to carry the current, and the net result is a failing
track circuit, which is probably attributed to bad ballast, zinc
treated ties or other causes.
The principal defect in the track circuit is that of improper bonding.
The only explanation as to why No. 8 iron wires became standard for
bonding appears to be that the bond wires were cut from this size iron
telegraph wire which was in general use at the time rails began to be
bonded. It is important to obtain better bonding to obtain a minimum
constant rail resistance.
It has been recommended that:
First--The use of galvanized wire bonds should be eliminated.
Second--Forty per cent. copper clad bond wires should be used as a
temporary expedient to replace galvanized bond wires.
Third--Except for theft and crystallization, copper bond wires would
be much more advisable.
Fourth--Larger bond wires should be used, these bonds to be at least
equal in carrying capacity to two 46-in. No. 6 solid copper or to two
No. 2, 40 per cent. copper clad wires.
Until recently it has been the general opinion of all experts on the
track circuit that the rail resistance was rather an unimportant
factor and that, as a general rule, the change in rail resistance
could be disregarded in making track circuit investigations and
calculations.
Many bad track circuit conditions have been laid to bad ballast
conditions, zinc treated ties, wet track, etc., which, if carefully
analyzed, would have shown the trouble to be due to extremely high
rail resistance. These faulty conclusions are being drawn nearly every
day.
Single rail track circuits, so called from the fact that but one rail
is insulated, are also used. Installations of this kind are made to
avoid the expense of two insulated joints or where one rail is needed
for another circuit. Such track circuits are more liable to failure
than those having both rails insulated for the reason that the
break-down of one insulated joint will extend the circuit beyond the
proper limit and cause interference of neighboring circuits or
extended shunting of the relay, due to the presence of a train beyond
the insulated joint.
A track circuit may be made to perform two separate functions in which
the direction or polarity as well as the presence of current is made
use of in the relay, provided the first or principal function actuated
by the presence or absence of current does not interfere with the
secondary function, actuated both by the presence of current and its
polarity.
Where switches occur in a track circuit, special means must be
employed to prevent short-circuiting through the switch rods and
leakage of current to the turn-out rail. The usual method is the use
of insulated switch rods with insulated joints in the leads of the
turnout and at the fouling point of the turnout. The switch points are
bonded to the stock rails to insure shunting by a pair of wheels on
any part of the track.
None of the methods employed in running track circuits through
switches show any protection against an open switch. In order to
obtain this protection a switch instrument or switch box is used. This
consists of a device with electrical contacts, the whole mounted on a
switch timber and connected to the switch point by means of a rod so
arranged that when a switch slips open or is thrown open the movement
of the rod actuates contacts which, on being closed, form a closed
path from one rail to the other through wires connecting the rails to
the contacts, thus when the contacts are closed by a switch being
opened, the same effect is produced as if a train was on the circuit,
shunting it out.
On electrically operated roads where tracks are bonded for the return
propulsion current with heavy copper bonds, no additional bond wires
are necessary.
The Track Battery
The usual form of track circuit has a primary battery at one end of
the insulated track section, with the positive terminal of the battery
connected to one rail and the negative terminal to the other, while a
relay at the other end of the section is connected to the rails in a
similar manner. Current flows from the positive side of the battery
through the one rail, the relay and the other rail back to the
battery, thus keeping the relay energized.
For d.c. track circuits, four types of cells have been used to a
greater or less extent, the gravity cell; Lalande (soda) cell; storage
cell and dry cell. The gravity cell has a voltage of about 0.8 or 0.9
volts, the resistance varying with the manner in which the cell is
maintained and averaging about 3 ohms. It will remain active for long
periods on closed circuits without appreciable polarization. Because
of this high internal resistance usually no external resistance is
necessary to be connected between it and the rail of the track. The
e.m.f. of the Lalande (soda) cell may vary from about 0.67 volts to
0.88 volts while the internal resistance will range between 0.019
ohm to 0.4 ohm. Because of the low internal resistance of these cells
it is necessary to use an external resistance of the proper value
between the cell and the rail. The storage cell is made in various
capacities and a fully charged cell on open circuit has a voltage of
approximately 2.1 volts which, when placed on discharge, becomes
approximately 2 volts and drops to about 1.8 volts when completely
discharged. The voltage in this type of cell varies with the density
of the electrolyte and to a certain extent with temperature. It has
practically a negligible internal resistance and it is also necessary
to use an external resistance in the leads between the cell and the
track to prevent a flow of excessive current when a train occupies the
track. The dry cell is used only in emergency cases or occasionally
for open circuit track circuits of 2 or 3 rail lengths, which are
sometimes used as annunciator starts to announce the approach of a
train to a tower-man. It is designed primarily for open circuit work
and will polarize when current beyond a certain figure is drawn
continuously from it.
The Track Relay
The track relay is a development of the instrument of the same name
used in telegraph service. It consists of an electro-magnet of the
horseshoe type with a pivoted armature, carrying one or more fingers
for making or breaking electric circuits for the control of signal
apparatus.
Track relays with resistances of 2 and 4 ohms are usually employed.
From experience with two-ohm relays on the L. & N., covering a great
many of them on all kinds of circuits, the following conclusions are
reached:
The two-ohm relay is more suitable for general use on track
circuits than the four-ohm, provided not less than the R.S.A.
recommended limiting resistance is used between the battery and
track.
The two-ohm relay will operate satisfactorily where the four-ohm
will not on bad track circuits, and with considerably less current
consumption.
The two-ohm relay will operate equally as well on good track
circuits of average length as the four-ohm, there being little
difference in current consumption on this class of circuit. Under
the same conditions longer track circuits may be operated with the
two-ohm relay.
The two-ohm relay is at least as safe as the four ohm. It should be
thoroughly understood that it is as important with the four-ohm relay
as it is with the two-ohm relay to have not less than the R.S.A.
recommended limiting resistance between the battery and track. This is
important with any kind of low internal resistance battery, and under
certain conditions with gravity battery also.
In one case assume a train to be passing from the relay end to the
battery end of a track section and in the other case from the battery
end to the relay end. The effect accomplished is the same except that
the relay will not release so quickly when the train passes from the
battery end towards the relay end, and this is in part due to the
self-induction of the circuit through the relay coils, the rails and
the axles of the train. It is due more, however, to small current
leakage from the adjacent section and the effects of stray currents
which are always present to a greater or less degree. A broken rail
will also generally open the circuit and de-energize the relay.
Circuits for the control of the various signal devices are broken
through the contact points of the track relay.
Track Circuit Maintenance
Cross ties have a relatively high resistance to the passage of
electric current, but when a large number connect the rails many
multiple paths are introduced into the circuit through which the
current may flow from one rail to the other, and, considering them as
a whole, the resistance they offer to the passage of the current
reaches a relatively low value. Consequently there is always a current
leakage from rail to rail through the cross ties and ballast. Every
effort should be made to secure and maintain the best ballast and
drainage possible on d.c. as well as a.c. track circuits. Cinders,
dirty sand, soft water-logged ties and ballast not well cleaned away
from the base of the rail will produce track circuit trouble,
particularly during wet weather, while good rock ballast, sound ties
and clean track give the greatest efficiency.
The use of ties freshly treated with zinc chloride also reduces the
ballast resistance. If too many such ties are used in a track circuit
the current leakage between rails becomes so great that not enough
current reaches the relay to hold it closed, the effect being the same
as if a train is on the track circuit shunting out the relay. For good
results, the number of zinc-treated ties installed per year in any
track circuit should not be greater than 15 per cent. of the total
number of ties in that circuit.
Track Circuit Troubles
Some of the common track circuit ailments are relay and track battery
troubles, defective track connections, poor bonding and broken rails,
short circuits or shunts, excessive leakage and defective insulated
joints, all of which will cause the signals to be set in the danger
position, while defective relays, foreign current and poor wheel
contact may result in a false proceed signal indication with a train
in the block section.
It was the quite general practice to operate bad track circuits by
piling on gravity battery, either in multiple or multiple-series
arrangements to obtain operating results without any regard to the
safety of the circuit and, no doubt, many false proceed failures were
caused thereby.
The effect of temperature changes on track circuit operation are of
considerable importance. The track relay, which is generally housed in
a cast or sheet iron box, probably is affected more by changes in
temperature than any other part of the track circuit. The resistance
of a 2-ohm relay, which is 2 ohm at 70 degrees F., will be 2.22 ohm at
120 degrees F., and 1.69 ohm at 0 degrees F., a variation of .53 ohm.
The pick up and release of the relay, .2 and .1 volt, respectively, at
70 degrees F., will be .22 and .11 volt at 120 degrees F., and .17 and
.085 volt at 0 degrees F. A relay, with a normal resistance of 4 ohm
at 70 degrees F., will be 4.45 ohm at 120 degrees F. and 3.38 ohm at 0
degrees F., a variation of 1.07 ohm. The pick up and release, .3 and
.14 volt, respectively, at 70 degrees F., will be .33 and .16 volt at
120 degrees F. and .25 and .12 volt at zero.
The point which is intended to be brought out by these figures is that
when the temperature of the relay increases, a correspondingly higher
voltage is required to pick up the armature, and when the temperature
decreases the armature will hold up with lower voltage across the
coils. This indicates that a track relay is more liable to fail to
release due to an imperfect train shunt in cold weather than at any
other time.
Some of the best preventatives that may be provided to guard against
false proceed signals due to track relays failing to release with a
train in the circuit, are:
1. Use as much resistance as practicable between battery and
track.
2. Use low resistance bond wires, and maintain bonding in good
shape.
3. Keep ballast well cleared from contact with rails.
4. Maintain insulation in insulated track joints in good condition.
Aside from these simple remedies no definite rule can be given to
combat foreign current. If it is so troublesome that these methods do
not overcome it, the circuit affected must be carefully studied to
determine the source of the foreign current and its path to the rails,
then special means can usually be provided to overcome it.
Ballast Resistance and Leakage
The importance of ballast resistance has long been recognized, and
this always has been considered the great variable, whereas,
investigations show that the ballast resistance is at least no more
variable than the rail resistance, and that of the two it is more
important to reduce the rail resistance to a minimum, and especially
to establish it as a constant.
When the ballast leakage problem was first taken up (on the L. & N.),
various kinds of ballast were measured in both wet and dry weather,
the intention being to determine the lowest possible resistance per
1000 ft. for each kind of ballast. It was proposed in this way to
establish a standard minimum resistance per 1000 ft. for each kind of
ballast. For instance, if a number of measurements in wet weather
showed 8 ohms per 1000 ft. as a minimum for track circuits with
crushed rock ballast, it was the intention to adopt 8 ohms as the
standard minimum ballast resistance per 1000 ft. for all track
circuits where crushed rock ballast was in use. If a number of wet
weather measurements showed 4 ohms per 1000 ft. as a minimum for
cinder ballast, it was the intention to adopt 4 ohms as the standard
minimum ballast resistance per 1000 ft. for all track circuits where
cinder ballast was used. It was the intention to follow out the same
process and establish a standard for all kinds of ballast in use. This
was soon found to be impracticable.
After making many ballast resistance measurements, it was noticed that
the variation of the resistance on any track circuit, as between wet
and dry weather, generally followed quite a definite rule. For
instance: If the resistance per 1000 ft. of dry ballast was found to
be 28 ohms or more, it would be not less than 8 ohms per 1000 ft. when
wet; or if resistance of dry ballast was found to be between 22 and 28
ohms per 1000 ft., it would be not less than 6 ohms per 1000 ft. when
wet.
Once a relay is picked up or energized, but a small amount of current
is required to maintain it in that condition. This is one reason why
it is important to keep the ballast clear of the rails and it is
because of the condition which may cause a relay to remain energized
that rules are in force requiring the signalmen to disconnect a track
relay when track forces are changing out rails.
Combined Rail and Bond Wire Resistance
On circuits newly bonded with two 46-in. galvanized iron wires a
joint, the combined rail and bond wire resistance was found (on the L.
& N.) to vary from .02 ohm per 1000 ft. of track on some circuits to
.265 ohm on others, a difference of over 1300 per cent. This was
rather puzzling. After a great many measurements had been made on
different circuits it was found that no two measurements gave the same
results, notwithstanding the fact that in many circuits the size of
rail, length of bond wires, and age of bonding were exactly the same.
On account of the bonding being new and the channel pins well driven,
the contact between the bond wire and rail was above suspicion. The
only other part of a track circuit that could possibly be the cause of
this difference was in the contact between the angle bars and rails,
and this later proved to be the case. Actual measurements made in the
field proved that when the rail is new and the joint bolts tight,
nearly all of the current flowing from rail to rail passes through the
angle bars, whereas when the rails get old a coating of rust and dirt
forms between the rail and angle bars, forcing practically all of the
current through the bond wires. On most of the circuits measured on
the L. & N. the combined rail and bond wire resistance was found to be
less than .1 ohm per 1000 ft. of track, although many were found to be
between .10 and .30 ohm per 1000 ft. It is interesting to note that
two circuits were found bonded with two 52-in. iron wires, for which
the combined rail and bond wire resistance measured .410 ohm, and that
by adding two 40 per cent. copper clad bond wires to each joint the
combined resistance was reduced to .144 ohm.
The Growth of the Track Circuit
Unfortunately there exists little or no data regarding the mileage of
track circuits installed from the time the first installation was made
by Dr. Robinson at Kinzua, Pa., and Irvineton up to about 1905. During
the period between January 1, 1905, and September 30, 1906, the total
automatic block signal mileage installed was 1,710.6, which brought
the total up to 6,826.9 for the United States. Between September 30,
1906, and January 1, 1908, 3,976.1 miles of automatic signals were
installed, which increased the above total to 10,803.0 miles.
The Block Signal and Train Control Board, seeing the need for accurate
data in the signal field, started the tabulation of such statistics
when it compiled and issued Block Signal Statistics as of January 1,
1908. After this board went out of existence, the Bureau of Safety of
the Interstate Commerce Commission continued the collection and
publication of these data yearly. Perhaps no better word picture can
be given of what Dr. Robinson's invention has meant to the railroads
than to present the story in the form of a table showing the miles of
road and the track equipped with the track circuit since January 1,
1908. In addition to the table, the accompanying chart presents the
information in a graphical form.
[Illustration: Progress Chart of Automatic Signal Installations
Since January 1, 1908.]
Track Circuit Mileage for Automatic and Controlled Manual Signals
in the United States as Taken from I.C.C. Reports
----------+-------------------+---------------------------------------
| Automatic | Controlled Manual
+---------+---------+-------------------+-------------------
| | | Miles of Road | Miles of Track
| Miles | Miles +--------+----------+--------+----------
| of | of | Track |Continuous| Track |Continuous
| Road | Track |Circuits| Track |Circuits| Track
| | | at | Circuits | at | Circuits
| | |Station | |Station |
----------+---------+---------+--------+----------+--------+----------
January 1,|
1908 | 10,819.3| 18,534.1| 726.7 | 212.0 | 2118.0 | 410.8
1909 | 12,174.3| 20,590.9| 407.6 | 572.2 | 978.0 | 1413.0
1910 | 14,238.9| 23,771.3| 385.8 | 491.5 | 953.5 | 1371.3
1911 | 17,709.8| 29,151.6| 483.9 | 439.4 | 1119.3 | 739.9
1912 | 20,300.0| 33,343.8| 402.0 | 295.9 | 955.6 | 496.0
1913 | 22,196.6| 36,873.0| 370.2 | 228.3 | 868.9 | 380.3
1914 | 26,569.3| 44,461.2| 275.7 | 180.3 | 625.3 | 281.6
1915 | 29,863.5| 49,442.1| 250.5 | 145.1 | 549.3 | 185.7
1916 | 30,942.5| 51,119.7| 255.1 | 125.1 | 549.6 | 179.3
1917 | 32,954.6| 53,799.8| 230.3 | 132.0 | 524.8 | 155.5
1918 | 35,193.1| 57,083.6| 208.1 | 131.2 | 451.6 | 154.8
1919 | 36,989.4| 59,458.2| 221.2 | 256.9 | 483.8 | 441.2
1920 | 37,968.8| 60,992.3| 196.3 | 129.2 | 413.3 | 151.4
1921 | 38,543.9| 61,744.5| 206.8 | 125.7 | 422.6 | 166.4
----------+---------+---------+--------+----------+--------+----------
The first yearly report of the Bureau of Safety, I.C.C., on block
signals to contain information as to the miles of road and miles of
track on which alternating current track circuits were installed, was
that issued as of January 1, 1914. Data taken from that report up to
the last one issued is presented in the table below.
Alternating Current Track Circuit Mileage
----------------+---------------+----------------
| Miles of Road | Miles of Track
----------------+---------------+----------------
January 1, 1914 | 3,289.2 | 4,144.6
January 1, 1915 | 2,728.2 | 5,814.9
January 1, 1916 | 3,186.7 | 6,679.0
January 1, 1917 | 3,336.2 | 6,823.6
January 1, 1918 | 3,748.0 | 7,530.1
January 1, 1919 | 4,496.6 | 8,620.2
January 1, 1920 | 4,676.5 | 9,026.0
January 1, 1921 | 4,786.1 | 9,120.2
----------------+---------------+----------------
Alternating current track circuits have certain advantages over direct
current track circuits, particularly in respect to their immunity to
the dangerous effects of foreign direct current to which d.c. track
circuits in some communities are subjected. The above table is
therefore of interest as it shows the application of alternating
current as made to Dr. Robinson's invention of the closed track
circuit.
Part IV
THE TRACK CIRCUIT IN GREAT BRITAIN AND ON THE CONTINENT
By T. S. Lascelles
No satisfactory records appear to have been kept as to the origin and
development of track circuiting outside the United States, which
renders it very difficult to arrive at any conclusions that could
serve as a basis for a real historical sketch upon this interesting
subject. In view of the fact that the Signal Section of the American
Railway Association proposes to publish a memorial to the late Dr.
William Robinson, generally regarded as the inventor of the closed
track circuit and certainly the first to utilize it in the control of
an automatic block system, the following brief remarks may prove of
interest to the writer's fellow members of the Signal Section. It is
not suggested that they are in any sense complete, as to make a
complete survey would require considerable investigation. They really
represent the writer's present general understanding of the subject
and are open to such criticism and correction as anyone may be able to
offer to them, in England or elsewhere.
There is no doubt but that track circuits were thought of and actually
experimented with in England a great many years ago--probably as far
back as the earliest American attempts--but the want of satisfactory
records make it very difficult to decide on what actually took place.
However, it is certain that the late W. R. Sykes, well-known
throughout the railway world for his controlled manual block and other
inventions, endeavored to use the track circuit in the sixties and
that Bull, the inventor of the bull-headed rail employed in England
for the chaired track universally found there, clearly had the idea of
a track circuit in his mind, for he refers to it in a patent obtained
in 1860. It was apparently in the early part of the sixties that W. R.
Sykes fixed a track circuit experimentally at Briseton on the old
London, Chatham and Dover Railway, and shortly after also at the
Crystal Palace Station on the same line. The apparatus employed must
necessarily have been rather primitive. In the seventies, track
circuit was installed by him at St. Paul's station, also on the
Chatham Railway. At that time very little was known about the track
circuit theoretically and the construction of the relay was very
different from our modern types. Sykes' relay completed the control
circuit by the insertion of a contact point into a mercury trough. It
was also, the writer believes, built on the solenoid principle. So far
as is known it was not suggested at this time and at all events not
attempted to make an automatic block system controlled by track
circuits, such schemes for signaling of this type as were put forward
being always based on the intermittent or track instrument control
plan.
It must be remembered that the conditions obtaining in England, widely
different from those seen in the United States, were not such as to
give much encouragement to the development of automatic signaling,
while over and above this, the English conservative nature always
looked askance at automaticity in railway apparatus. Automatic
signals, worked on a track instrument plan, were put into regular work
on the Liverpool Overhead Railway in 1893, but it was not till 1902
that automatic signals controlled by continuous closed track circuits
were to be seen in operation on an English main line railway. Before
this, however, track circuits had made some progress, though not very
much; the most important instance of its application was in the Kings
Cross tunnels, just outside the London terminal of the Great Northern
Railway, in the early nineties. This installation, which was used
under none too favorable circumstances from the point of view of
successful operation, proved to the English what the track circuit
could do and heralded the day when its place in the safe working of
railways should be better appreciated. By this time in the United
States, largely under the influence of the pioneer work of Dr.
Robinson, automatic signaling had made quite considerable progress and
the potentialities of the track circuit had been fairly realized.
It may occur to Americans to ask why it was that progress in England
was so slow and this is a question which cannot be answered by a
single reason since a combination of circumstances was the cause. In
the first place the older type of English signal officer was
extraordinarily conservative regarding signaling practice of other
countries as he had that peculiar type of contempt which generally
comes from want of knowledge. Anyone who, like the writer, listened
for instance to the objections brought forward by some of these men to
controlled manual block, will know to what absurd lengths they could
go in resisting improvements in working. Although this spirit, which
has markedly diminished during the last 15 years, must have accounted
to some extent for the slow development of the track circuit in
England, there were yet some reasons of a more sensible kind which
must be borne in mind. The English light weight four-wheeled freight
car without air brakes was and still is a bother to the track circuit
engineer because of the difficulty of getting a satisfactorily low
shunt under all circumstances. Then again the Mansell disc wheel made
it necessary to resort to bonding between the tire and the hub before
a vehicle would shunt the track circuit at all and this was an expense
to which the companies were loath to go, especially if they had or
contemplated very few track circuits, though the use of even one
circuit really necessitated the whole of these wheels being so
treated. There was no great demand for automatic signaling, as the
manual system was giving good results and was also cheap at that time,
owing to the low wages paid to railway men. This and the other reasons
just given combined to render the progress in England extremely slow.
Some of the First Installations
Nevertheless, in 1902 the British Pneumatic Railway Signal Company,
who had in the previous year installed its first low pressure
pneumatic interlocking at Grateley, on the London and South Western
Railway, brought into use between that station and Andover an
automatic block system controlled by continuous track circuits, the
distance being about six miles. The signals were worked by low
pressure air. The success of these systems led to the adoption of them
shortly afterwards on the widened four-track main line between Woking
and Basingstoke on the South Western, a distance of 24 miles. The
Grateley-Andover installation has now been removed, not because it was
at all unsatisfactory, but because it was felt traffic and other
circumstances did not warrant its further employment. In 1905, Hall
electro-gas automatic signals were brought into use on the North
Eastern main line between Alne and Thirsk, a distance of 11 miles. In
1907, semi-automatic signals were installed between Pangbourne and
Goring, a distance of 2-3/4 miles, four track, by the Great Western
Railway to divide up a long manual block section and a few similar
installations have been made on the Midland, the Great Central, the
Belfast and County Down and other roads.
By this year, track circuiting had begun to be extensively used in
England. The British Pneumatic Signal Company had installed a series
of low-pressure plants near Manchester on the Great Central and track
circuits were used throughout while the same thing had been done at
Clapham Junction on the South Western. The Westinghouse Company had
supplied the District Railway, London, with automatic signals and were
actively engaged in fitting similar apparatus to the tube lines; they
soon afterwards commenced work on the Metropolitan Railway.
The main steam lines began to apply track circuits at various places
in conjunction with ordinary manual signaling and this process
received an added impetus from the terrible disaster which befell the
Midland Company's Scotch Express near a station called Hawes Junction,
when, in emerging from a tunnel it crashed into two light engines that
had been forgotten and had entered the block under the signals set for
the express. Several other bad accidents, notably one at Pontypridd,
on the Taff Vale Railway, due to trains and engines being overlooked
by signalmen while standing at adverse signals, emphasized the
necessity for paying serious attention to the question of track
circuiting and for undertaking a really earnest study of the matter to
see whether the difficulties due to the light freight car, etc., could
not be overcome or at least considerably minimized.
Considerable progress had been made by the time the war broke out and
quite a number of track circuits had come into existence on all the
principal roads, although no extension work worth noticing was made to
purely automatic block systems on steam roads, this class of work
being confined to the suburban electric lines. Unfortunately, in this
as in so many things the war had a retarding effect and caused the
postponement of many plans. The increased price of wages and materials
has hampered progress a great deal and it will be some time yet before
any great improvement is noticeable. On the other hand, the great
increase in wages has caused a demand on the railways for a reduction
of operating costs with the result that signal engineers are
endeavoring to produce schemes which will enable signal towers to be
abolished or closed at intervals where they were formerly kept
continuously in service and in this and other ways to dispense with
unnecessary staff. It is in this that the track circuit will help very
considerably. Its further extension on English lines is a certainty
and simply a question of time and money. Since the inception of the
Institution of Railway Signal Engineers a great amount of work has
been done in discussing and studying requisites and so on for track
circuit work, both of the direct current and alternating current
types. All this has resulted in increased confidence on the part of
the traffic officers in track circuit and allied apparatus and caused
them to look more and more to the signal engineer to help them in
their work and to accord him the respect and credit he deserves.
The writer is aware that these lines can only convey a very imperfect
idea of the actual state of affairs, but he prefers to write them now
as a preliminary account, not yet being in a position to furnish the
figures which the Signal Section desires.
Track Circuits on the Continent
Turning to the continent, the writer must necessarily speak in very
general terms since there is less published on this subject by
continental journals than by English and, of course, the field is
rather a wide one, embracing so many lands and tongues. The track
circuit is, of course, known there fairly well, but there are no very
great installations of automatic block to be found. In the case of
France, the Paris, Lyons & Mediterranean had, before the war, an
installation between Larsche and Auperre, 24 miles, and some
semi-automatic sections in various places. The Midi Railway had also
the Hall disc system from Bordeaux to Langon, 26 miles, and the writer
believes extensions to this have since been made. The Est Railway
began trials before the war and during the war, owing to shortage of
staff and having greatness of traffic to the eastern military area,
installed automatic signaling on the Paris-Nugent line. The writer has
been told that it is under consideration to equip the whole line to
Avricourt, where it connects with the Alsace-Lorraine system. The
writer is not aware whether the other companies in France have any
automatic blocks, but he believes not. They all have, however, track
circuits installed at various places in connection with the ordinary
signaling. Owing to the lower standard of living and the employment of
women operators at many points, there is not so great an incentive to
the adoption of automatic devices, as in some other countries. French
engineers, however, know what Americans have done in this way and some
very complete accounts of American systems have appeared in "La Revue
generale des chemins de fer." The Paris Metropolitan line is
automatically signaled by an intermittent contact system without track
circuit.
In Germany, the track circuit for steam lines is not looked on with
much favor, as owing to the extensive employment of the Siemen's
controlled manual and the peculiar station masters' system of control,
called "Station Block," always used in that country (with, it must be
admitted, a very high record for safety,) the Germans think they would
not gain much by any great use of track circuit or automatic signals.
The writer has just had this view confirmed by a friend returned from
visiting the important works of the German Railway Signal Company at
Bruchsal, Baden. Automatic signaling is used on certain important
sections of the Berlin Elevated and Underground Road, installed before
the war by the Westinghouse Company, of London, with a.c. double rail
track circuits and this will be extended eventually to cover the
remaining sections still worked by the Siemen's controlled manual. Dr.
Kemmann, a member of the General Railway Direction, Berlin, published
last year a very interesting book describing his work with accounts
also of the London Underground and New York Subway installations,
showing that foreign systems are studied in Germany. But for steam
roads the writer believes from what he has studied of German methods
and ideas on the subject that the manual system will remain in use and
that the track circuit will not be much adopted.
The same remarks apply generally to Austria, Holland and Scandinavia,
though in the latter case English ideas are more in evidence and it is
probable that the track circuit, already in use to some extent, will
be developed as time goes on. In Austria automatic signaling was
certainly tried on a small scale on the Southern Railway, but with
what results the writer cannot say. In Switzerland the extended use of
iron ties is against the track circuit. In Belgium the Hall system was
at one time in use between Ghent and Wondelgem, but as the course of
the line was changed, these signals were removed. The section was
about 3-1/4 miles long. Automatic signals do not exist there now but
the track circuit is used at certain stations, notably throughout the
all-electric power installation at and close to Brussles Nord. The
writer does not believe it likely that automatic signaling will be
used on the steam roads in Belgium, at all events for some time yet.
With regard to Italy, Spain and Portugal, the writer does not possess
details, but believes it likely that the track circuit is only in use,
if at all, at a few important stations. The new Metropolitan line in
Madrid is equipped with an intermittent contact system, probably
copied from the Paris Metropolitan.
Although a little outside the scope of these notes, the writer would
emphasize that in the English colonies and in South America
(especially, however, the former) the track circuit is being much used
and its value appreciated. Automatic signaling is in use in Victoria,
Queensland, South Australia and New South Wales. The operating
conditions in these countries no doubt much resemble American
circumstances and the adoption of automatic signals is a natural
development.
Summing up, the writer would say, that the earliest experiments of W.
R. Sykes in England are probably as old as those of Dr. Robinson, but
owing to the different circumstances in which the former inventor was
placed, he had little encouragement to continue them and thus American
development at first went on far ahead of English, while owing to the
vastness of the American continent it must always present a larger
field to the signal engineers' ingenuity and activity. In later years,
however, the English signalmen awoke to the importance of the question
and installations were constructed which, if smaller, showed as great
a degree of technical perfection as any in America. The future will
doubtless see more such installations.
It is not known to the writer whether anyone on the continent had the
idea of a track circuit as far back as Sykes' or Robinson's
experiments or when the first attempts were made. It would require
much investigation to find this out. Track circuit possibilities are
now well known there and no doubt its use will extend, but in certain
countries, notably Germany and Switzerland, there are local
circumstances which act rather strongly against it at present. The
writer cannot give statistics on the subject now. There are some
figures which he possesses, but they should be verified and amplified
before being used by the Signal Section for publication. The preceding
notes are, he is too fully aware, very incomplete and general, but he
hopes they may be of some present use.
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