GB1007597A - Improvements relating to automatic train control for automatic braking apparatus - Google Patents

Abstract

1,007,597. Fluid-pressure brakes. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. Feb. 20, 1963 [March 5, 1962], No. 8404/62. Heading F2F. An automatic train control system for use with deadman automatic brake apparatus has a vent valve 8 which is the deadman's application valve, means 32 for operating the latter after a time delay, a holding circuit 30 for energizing this means, and a pneumatic switch 18 allowing re-energization 1 of the holding circuit up to the point of operation of the valve 8 but not afterwards. Normally, wire 28 is energized, switch 29 made, and holding circuit 30 and magnet valve 32 energized. The latter holds an exhaust valve 33 closed and an inlet valve 34 open which allows a compressed air supply at 35 to charge a timing reservoir 37. The pressure of the reservoir acts on top of piston 11, which overcoming its spring loading, holds the valve 8 on its seat to close off connection 7 from outlet 13. Thus brake pipe 2 is normally charged with air. The piston 19 is held up against the effort of spring 17 by brake pipe pressure thus closing switch contacts 20. Upon an adverse signal being received from the track, wire 28 becomes de-energized to cause relay 30 to break contacts 29. Magnet valve 32 is de-energized which causes inlet valve 34 to close and exhaust valve 33 to open. Timing reservoir 37 drops in pressure via choke 36, which pressure registers above piston 11. After a predetermined time, when this pressure has been reduced sufficiently, the spring loading will lift the piston 11 and allow brake pipe 2 vent to atmosphere causing a brake application. The brake pipe pressure drop will cause the spring 17 to move the piston 19 downwards to break the contacts 20. Prior to the operation of piston 11 the driver could cancel the signal by energizing the wire 28, which in turn would energize the holding relay 30 and magnet valve 32 via contacts 20 to return the valves 33, 34 to their normal positions allowing reservoir 37 to be recharged. After the operation of the piston 11 the signal cannot be cancelled, since the switch contacts 20 are broken, until pneumatic switches 22 or 24, which are alternatives, connect contacts 23 or 25. Switch 22 operates to close contact 23 after a predetermined drop in brake pipe pressure and switch 24 operates to close contacts 25 after a predetermined time which is determined by the reservoir 1 venting through choke 4 to the brake pipe. In modifications, the switch 18 is arranged to operate on the difference of pressure across the valve 8 and the pressure in pipe 2 is used to operate a further deadman's valve. In a modified switch 18 the pipe 6 is connected to the upper chamber and the lower chamber is connected to a reservoir which is charged by a feed groove in the piston that is closed on operation of the switch. An alternative to the feed groove is to place a choke between the reservoir and pipe 6, or across the piston, or through the stem of the piston, which choke can be adjusted so that contacts 20 are closed after the predetermined time.