GB645383A - Improvements relating to compressed air braking apparatus - Google Patents

Abstract

645,383. Fluid pressure brakes. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. March 16, 1948, No. 7830. Convention date, March 17, 1947. [Class 103 (i)] A compressed air braking system for vehicles of the kind in which the degree of braking effected is arranged to be automatically varied in accordance with the load on the vehicle, is characterized in that a load responsive pressure control device 11 is provided for each axle of the vehicle, the pressure of air supplied to the brake cylinder 4 being controlled by the device 11 for the axle carrying the lesser load. As shown in Fig. 1, the system comprises the usual auxiliary reservoir 2 and triple valve 3, the air supply 8 from which is connected to the brake cylinder 4 through a relay valve device 5 instead of directly as is usual. The relay valve 5 includes a valve member controlling the supply of fluid pressure from pipe 8 on through pipe 46 connected to the brake cylinder 4. The valve member is governed by the movement of a diaphragm assembly subject to the pressures in chambers connected by pipe 9 to the supply pressure and by pipe 10 to one or other of the devices 11 and in a third chamber open to atmosphere. The device 5 thus passes on to the brake cylinder 4 a pressure dependent on the control pressure transmitted by pipes 22, 23, member 26 and pipe 10, the devices 11 operating in accordance with the load on each wheel transmitted by levers 14, 18, 19 pivotally connected to the spring mountings. The valve member 26, as shown in Fig. 2, includes a double check-valve element 27, 28, 29, which ensures that the relay valve 5 is connected only to that control device 11 associated with the less loaded axle. The air supply to the control devices 11 passes through pipes 39, 41 and 21 branched off the connection 46 to the brake cylinder 4. A regulating device 33 is interposed between pipes 39 and 41, which as shown in Fig. 3, comprises a valve element 34, which opens at a certain minimum pressure in the chamber 38, dependent on the setting of the spring 35, so as to provide a large flow connection between pipes 39 and 41 by passage 40. The device 33 ensures that a certain minimum pressure is rapidly built up in the cylinder 4, sufficient to move the brake shoes into contact with the wheels on each brake operation, before the load-sensitive devices 11 become operative to influence the working of the relay valve device 5.