GB909616A - Improvements relating to compressed fluid braking apparatus - Google Patents

Abstract

909,616. Fluid-pressure brakes. WESTING- HOUSE BRAKE & SIGNAL CO. Ltd. Feb. 22, 1961 [Feb. 22, 1960], No. 6096/60. Class 103 (1). In a triple valve where communication of a brake cylinder with a source of compressed fluid provided by an auxiliary reservoir is controlled by an application valve 20 operable by a diaphragm 12 subject on one side 15 to auxiliary reservoir pressure and on the other side 13 to brake pipe pressure, the effective area of the diaphragm subject to auxiliary reservoir pressure is less than that subject to brake pipe pressure by an amount which, in the released condition, is exposed to atmospheric pressure but which is exposed to a pressure more nearly equal the auxiliary reservoir pressure by valve means actuated by the diaphragm in its travel between the release and commencement of application positions. With the diaphragm 12 and follower 17 in the normal release position to which they are biased by the greater area of side 13, subject to brake pipe pressure from duct 14, and the lesser area of side 15, subject to auxiliary reservoir pressure from duct 16, due to the area of the thick-walled stem 28 subject to atmospheric pressure in chamber 30 through duct 34, the follower holds the reservoir charging valve 18 and brake cylinder release valve 22 open and application valve 20 shut. A bleed passage 25 between the brake pipe and the auxiliary reservoir is also open in this condition. On reduction in brake pipe pressure to apply the brakes, the diaphragm moves upwards closing first valve 18 then valve 22. A closure member 35, mounted on spring- biased diaphragm 36, seals off the chamber 30, connected to the quick service volume 31, from atmosphere and the end of the hollow stem 28 leaves the member 35 to allow connection between the quick-service volume 31 and brake pipe pressure in chamber 14, thus subjecting the area of the thick stem 28 to brake pipe pressure. With upward movement of the follower 17 the application valve 20 is opened. As pressure in the auxiliary reservoir approaches brake pipe pressure the diaphragm begins to move downwards to the lap position until the valve 20 is closed. Since the underside of the diaphragm 36 is subject to quick service pressure through passage 32a, and is opposed only by atmospheric pressure over its major top area, there is a pressure differential maintaining the closure member 35 against the outer annular seat, forming a quick service exhaust valve. Since this exhaust valve has to be opened by movement of the diaphragm 17 from lap to release position, a resistance is thus provided to this movement to provide lap stability. Specification 846,314 is referred to.