Patent GB-191003637-A (GB)
Title: Electric Cab Controlling System for Railways.
Inventor: PATTERSON HAROLD DUNCAN
IPC: B61L3/12
Filed: 1910-02-14
Granted: 1910-09-15
Abstract: 3637. Patterson, H. D. Feb. 14. Electrical s y st e m s, automatic; track apparatus actuating signals on trains and other than o n trains.-The train carries a half 3 of the iron circuit of a transformer, upon which is wound the primary coil 6 receiving alternating current of high frequency from a generator 1 on the train. Suitably situated in the track is a corresponding half-transformer 7 with a secondary winding 8. When a danger signal is to be given on the engine, the secondary circuit is open, or so arranged that no substantial current is induced in it. The result of the half-transformer 3 passing over the half-transformer 7 then is to decrease momentarily the reluctance of the magnetic circuit and therefore to diminish the primary or exciting current in the circuit 11. The parts are proportioned so that the reduced primary current is unable to hold the relav 14 closed, and a visual signal 18 goes to ' danger ' and the train-pipe is opened. When the track is clear, the secondary circuit is so arranged that a substantial current is induced in it when a train passes over it, and in this case the current in the primary circuit on the train is not materially reduced and the signal 18 is maintained in the 'safety' position. The apparatus may be duplicated for home and distance signalling; two half-transformers 3<H>, 3D, Fig. 2, being placed side by side on the engine to cooperate with similarly-placed parts on the track. The home-signal primary circuit is made through contacts 64, 65. When the armature 50 falls, on the current being reduced to give a danger signal, these contacts are separated, and the circuit of a red light R is completed by contacts 78, 69, and the circuit of green light G is broken at 70. The relay armature 13 can be re-set by closing the switch 85. The distant signal circuit similarly cuts out the green light G and puts in a yellow light Y, when the current is reduced, and may be re-set by a switch 81. This circuit is also broken at 59 if the home signal apparatus receives a danger signal. The secondary circuit of a track half-transformer can be closed or opened by a track-relay, energized when the block is clear and short-circuited by a train entering the block. The secondary circuit may, by suitable condensers and choking-coils, be rendered resonant to the frequency employed. In place of using track relays and batteries, the secondary circuit of a track half - transformer is closed through portions of the track rails and cross-bonds, and includes choking-coils or condensers which are designed to produce a resonant secondary cir cuit. The presence of a train in a block destroys the resonance and prevents the induction of a sufficiently large secondary current to maintain the primary current on the train at an operative strength. According to this plan, the track may be divided into blocks by dividing one of the track rails. In this case, the transformer secondary circuit is connected to the rails near to one insulation and the crossbond near to the other insulation. Or, the track may be divided up by the presence of crossbonds, either inductive or non-inductive, only. In this case, each transformer secondary circuit, as 8 in Fig. 8, is connected to the track rails at points midway between adjacent cross-bonds 28. In all cases. the track transformer itself is situated in front of the commencement of its block. The use of high-tension currents in the track can be avoided by a step-down transformer in the secondary circuit. Fig. 8 shows a continuous rail system for home-signalling only, in which the current produced in the track secondary 8 when the track is clear is used to operate a relay 36 which causes a semaphore signal 40 to move to ' safety ' while the train is passing it. Fig. 9 shows a modification in which inductive cross-bonds 28 are used and a step-down transformer 44 unites the transformer secondary circuit and the track rails. The secondary current in this case is used to operate an induction motor relay 42 for controlling a semaphore 40.