Robinson’s Description of His Invention
DR. WILLIAM ROBINSON2
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.
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.
Notes
2 Reprinted from a circular published by Dr. Robinson in 1913.