GB261339A - Improvements relating to feed valve devices for fluid pressure braking apparatus - Google Patents

Abstract

261,339. Westinghouse Brake & Saxby Signal Co., Ltd., (Assignees of Dean, W. E.). Nov. 13, 1925, [Convention date]. Addition to 236,161. Pressure-regulating valves.-A pressure-regulating device particularly applicable as a feed valve on fluid pressure braking systems and of the kind comprising a main valve controlled by an auxiliary valve and in which a Venturi tube is inserted in the main conduit'for reducing the pressure on the regulating diaphragm to accelerate the action of the device, is provided with further means for limiting the action of the Venturi device. In the form shown in the Fig. the main valve 14 has ports 15, 16 adapted to co-operate with ports 17, 18 to control the flow from a reservoir pipe 13 to the train pipe 7 and is actuated by a piston subject to conduit pressure. Pressure is admitted to the back of the piston through a restricted orifice 23 and is exhausted through an auxiliary valve 8 actuated by train pipe pressure acting on a spring loaded diaphragm 3. The connection to the train pipe is made through a Venturi device 19 so that when the main valve is open the pressure acting on the diaphragm is reduced below that in the train pipe. As, however, the main piston moves to open the main valve it uncovers side ports 21 in the cylinder leading to a bye-pass passage whereby further inlet pressure is admitted to the back of the piston to more or less counteract the accelerating action of the Venturi device. The ports 21 may be of uniform area or increase in area in the direction of outward movement or a single tapering port may be provided. In a modification the ports 21 are dispensed with and a bye-pass passage provided so that only part of the main flow passes through the Venturi device. In a further modification the main actuating piston is fitted with a second loading spring adapted to come into operation when the main valve is partly open.