Patent GB-851735-A (GB)
Title: Improvements relating to fluid pressure railway braking apparatus equipped with automatic train control
IPC: B60T13/66
Filed: 1957-07-26
Abstract: 851,735. Railway braking apparatus. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd., and SIMMONS, A. W. July 23, 1958 [July 26, 1957], No. 23719/57. Class 103 (1). In a fluid pressure braking apparatus for railway vehicles equipped with automatic train control equipment 12, an isolating valve controls the connection of the equipment with a brake pipe of the brake controller. In Fig. 1 a driver's valve 13 controls the connection between supply line 14, a brake pipe 15 and a brake cylinder pipe 16, a driver's brake valve isolating valve 19 controlling pipes 14 and 16, the automatic train control equipment 12 including at least one valve operated electromagnetically through electric circuits controlled by a fluid-operated switch 20; a pilot valve 22 is provided at each driving position to bring the controls at that point into use and is key operated. With the pilot valve 22 in the " on " position, main reservoir pressure from pipe 24 acts through pipe 23 and 23a on a valve 19 to open pipes 14 and 16, and through pipe 23b, a normally open isolating cock 21 and a pipe 27 to chamber 30 of an isolating valve 28 to force piston 31 against piston 35, Fig. 2, to overcome the permanent force on piston 35 due to main reservoir pressure in chamber 36 acting on face 37 and a spring 41, to raise the piston 35 from seat 32 and connect the brake pipe chamber 34 to a chamber 33 connected via pipe 33a to the automatic train control equipment, the vent pipe 43 of chamber 33 being closed by an extension 45 of the piston 31; electric current being made available in the circuits of the automatic train control equipment by main reservoir pressure in pipe 26 operating switch 20. Hence the equipment at the driver's position is active. Should a defect occur resulting in pressure failure in chamber 30, due for example to a fracture in pipe 27, not sufficient to cause a loss of pressure in pipe 18 such that a corresponding loss in brake pipe 15 causes brake application, the brake pipe pressure in chambers 33 and 34 returns the piston 31 out of engagement with piston 35 and maintains the piston off seat 32 so maintaining communication between the brake pipe and the automatic train control equipment which remains active until the brake pipe pressure is reduced to a point where it can no longer overcome the bias. In such instance the loss in brake pipe pressure would automatically apply the brakes. The vent passage 43 is of such size that the loss of brake pipe pressure through it is easily made up by the continued supply of pressure to the brake pipe by a valve 17. On switching pilot valve 22 to the " off " position the pipe 23 is connected to the exhaust pipe 25 hence the driver's brake isolating valve 19, switch 20 and chamber 30 are vented, the valve 19 interrupts pipes 14, 15 and the supply to brake pipe 15; electric current is no longer available in the automatic train control equipment and the piston 31 is withdrawn from piston 35 which eventually returns to its seat 32 when the brake pipe pressure has been reduced substantially below the full charged value. Reduction in brake pipe pressure may be primarily caused by brake application in the closing down of the driving position. Any fluid leaking past valve seat 32 when the piston 31 is in the off position is vented via passage 43 to prevent pressure build-up in the chamber 33. The apparatus may be modified for vacuum systems. Specification 745,105 is referred to.