GB848111A - Fluid pressure braking system for railway vehicles - Google Patents

Abstract

848,111. Fluid-pressure brakes. COMPAGNIE DES FREINS ET SIGNAUX WESTINGHOUSE. Aug. 8, 1957 [Aug. 8, 1956], No. 25020/57. Class 103 (1). A fluid-pressure braking system for railway vehicles comprises an electro-pneumatic straight air brake and a pneumatic automatic brake, having a single common brake pipe, and a distributer valve supplied with fluid from the brake pipe through a reducing valve to charge its associated control and auxiliary reservoirs. Electro-pneumatic straight braking.-A magnet-valve 2, when energized, moves a piston 3 to lift a valve 9 and connect a supplementary reservoir 13, supplied from brake pipe 1 via a non-return valve 12, to chamber 11, valve 9 closing when pressure in chamber 4, connected to chamber 11 through a choke, acting on diaphragm 6 overcomes the effect of the magnetic force on piston 3. Air is transmitted from chamber 11 to chamber 16 of relay 17 to move diaphragm 19 and piston 20 upwards to raise valve 21, air from reservoir 13 then passes via chambers 22, 23 and a double check valve 26 to a pressure-limiting valve 32. When pressure in chamber 18 overcomes that in chamber 16 the piston 20 moves down to close valve 21. Valve 32 limits pressure to brake cylinder 41 to a predetermined value; when pressure in chamber 33 reaches this value, spring 36 becomes compressed and piston 37 moves to enable valve 38 to cut off supply to brake cylinder 41. Brake release.-Current to valve 2 is decreased and piston 3 moves down until balance is reached between the two thrusts on diaphragm 6, air from chamber 16 in relay 17 escapes via pipe 15, chamber 11, and hollow piston 3 to atmosphere. Piston 20 of relay 17 moves down due to pressure in chamber 18 and connects chamber 23 to atmosphere; if valve 38 is open then brake cylinder 41 exhausts to atmosphere; but if valve 38 is closed, then pressure in chamber 18 is greater than in cylinder 41, the relay 17 allows air to exhaust from chamber 18 until it equals that in cylinder 41, valve 38 then opens due to spring 36 and the cylinder 41 exhausts as before. Variations in release and application are obtained by varying the electric current to valve 2. Pneumatic automatic braking.-For normal brake pipe pressure the valve 48 of reducing valve 42 is held open by spring 46 for operation of distributer 28 to apply or release the brakes, and closes for an increase above normal pressure to control the pressure flow to distributer 28. Should a decrease in pressure occur in pipe 1 due e.g. to a coupling failure, the piston 59 of a vent valve 54 moves up due to pressure in chamber 56 against spring 58 to open valve 61 to connect pipe 1 to atmosphere through a large port 64, pressure then decreases rapidly. In reducing valve 42, spring 46 overcomes pressure in chambers 43, 50, 49 to hold valve 48 open to operate distributer 28 to apply the brakes automatically with pressure from auxiliary reservoir 30 via valves 26, 32. In arrangements in Figs. 2, 3, not shown, the magnet valve 2 is replaced by a magnet valve for braking and one for release, each valve being energized via a manually operated straight air brake valve and a pneumatic relay whose piston rod operates electric contacts.