GB1428438A - Relay valve - Google Patents

Abstract

1428438 Brake relay valves MIDLANDROSS CORP 27 Aug 1974 [12 Oct 1973] 37468/74 Heading F2F An air-brake relay valve comprises a housing 22 with supply and delivery ports 28, 30 which can be connected to a source of pressure 24 and the brake 34 respectively, valve members movable between first and second positions to apply and release the brakes, a valve actuator movable in the housing and provided with first and second pressure responsive surfaces formed by piston portions 44, 50, a passage, formed by a loose fit between piston portion 50 and its cylinder wall 52, to connect a chamber 54 with a chamber 56 but restrict free passage between the chambers and a control port 20 connecting with the chamber 56, adjacent the piston portion 44, the actuating means being initially subject to control pressure acting on the part 44 so that the motion of the parts is damped and hunting of the components is prevented. When pressure is applied to port 20 piston 44 moves downwardly and at the same time air is metered through the annular passage between piston 50 and cylinder 52 so that a valve element 60 moves to engage a seat 70 on a tubular member 72 and isolate the delivery port 30 from the exhaust port 78, further movement causing the tubular member 72 to move so that a valve element 86 disengages from a seat 94 to place a cavity 96 below piston 44 in communication with the inlet port 28 and isolate it from the exhaust port so that air can pass to the brake via a passage 98 and port 30.