Patent GB-315805-A (GB)
Title: Improvements in or relating to train control systems
IPC: B61L3/22
Filed: 1929-07-18
Abstract: 315,805. General Railway Signal Co., (Assignees of Bushnell, C. S.). July 18, 1928, [Convention date]. Track apparatus for stopping trains.-In a continuous or intermittent system of train control a governor brings into operation according to the direction of movement of the train alternative train-carried devices co-operating inductively or otherwise with the rails or track inductors and cuts out the devices when the train is moving below a predetermined slow speed. The governor consists of a gear-wheel pump 8, operated by movement of the train, which transfers mercury, or other conducting liquid from one to the other of chambers 2, 3 according to the direction of running and thereby breaks contact between one of the terminals 11, 12 and the liquid. In the stationary condition both terminals may be out of contact with the liquid. In the arrangement shown both terminals are in contact when the train is stationary; the circuits of relays BR, FR are thereby closed and a resetting circuit for a brake-controlling device EPV<1> is closed through the relay contacts 19, 17, and contact 43 and contact arm SA of a speedresponsive switch, and the train is free to start. A second circuit through EPV<1> includes a stick contact 40, contact 43 and arm SA. When the train moves forwardly the circuit of relay FR is broken at contact 11, the resetting circuit is broken at 17 and a circuit through a main relay MR<1> is made by armature 18. This circuit includes forward train carried coils RC which inductively receive current from the track rails for the relay circuit. When the train moves rearwardly the circuit of BR is broken at 12, the re-setting circuit is broken at 19 and a main relay circuit including rear train coils RC<1> is completed. With main relay MR<1> energized a circuit for EPV<1> is completed through armature 49, contact 42 and the arm SA. The train can proceed at speeds below 15 m.p.h. under any track conditions because the arm SA remains on contact 43 and the main relay circuit, is not in control. At speeds greater than 15 m.p.h. the stick circuit is broken as the arm leaves contact 43 and the main relay circuit becomes the controlling circuit. If now the current to the coils RC fails, as under danger conditions, the armature 49 falls, EPV<1> is de-energized and the brakes are applied. The circuit of EPV<1> is broken at contact. 42 without regard to track conditions if a speed of 60 m.p.h. is exceeded. After a brake application it is neecssary to stop the train in order to close contact 11 or 12, pick up contact 17 or 19 and so establish the re-setting circuits for EPV<1>. The train is free to proceed against the normal direction of the traffic since the coils RC or RC<1> which are cut into operation are in the rear and are ineffective, the track currents not passing beyond the forward axle 23, and the relay MR<1> is accordingly not energized. Since however the only remaining circuit for EPV<1> includes contact 43 the train cannot proceed at more than 15 m.p.h. For intermittent control the front and rear coils RC, RC<1> are replaced by receivers comprising magnetic cores with primary and secondary windings which co-operate with track inductors placed on the side of the track. The inductors may consist of cores wound with choking coils. When a train-carried coil passes over an inductor a back EMF is generated in the secondary coil of the receiver, if the choking coil is open, which de-energizes the main relay. The consequent de-energization of EPV<1> is avoided if the driver operates an acknowledgment contactor which momentarily provides the alternative circuit for the main relay. By means of the governor and the relays FR, BR in this arrangement, that receiver which will pass over the track inductors is put into circuit when the train is proceeding in the direction of traffic and the other receiver, when the train is proceeding against the traffic. In the latter case the automatic control is inoperative.