GB764797A - Improvements in railway vehicle compressed air braking systems - Google Patents

Abstract

764,797. Fluid pressure railway brakes. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. Feb.9, 1955 [Feb. 25, 1954], No. 3820/55. Class 103 (1). A driver's valve RM for fluid pressure railway brakes has a modified feed valve SA which in combination with a supplementary volume chamber 7 having a calibrated orifice 8 open to atmosphere avoids the danger, as with known driver's valves used on long trains, such as of 80 vehicles, that either the rear vehicle brakes may not be released or that the vehicle at the head of the train may become overcharged. When the driver's valve RM is placed in the limited overchange position, corresponding to Fig. 1, the brake pipe CG is fed via the feed valve SA, connected at 16, the regulation of which corresponds to the normal pressure (for example 5 Kgs/cm<SP>2</SP>) given by the spring 38 plus a certain overcharge controlled by the supplementary effort of the piston 41, moved upwards by the pressure in space 40, which exerts a thrust under the diaphragm 35. Under these conditions, firstly, an escape of air to atmosphere, via the hole 47 will occur, and secondly there will be a return of air from the supplementary volume 7 (if the pressure of this has been greater than the brake pipe pressure) to the brake pipe CG by the pipe 4, and the supplementary passage 2 in the rotary valve 1 until the pressure in volume 7 equalizes with that of the brake pipe CG, which will then be fed at a pressure equal to normal pressure (for example 5 Kgs/cm<SP>2</SP>) plus the overcharge (for example 300/400 grams), the high pressure in the pipe CG then allows the release of all triple valves throughout the train. In another embodiment described, the feed valve SA has been modified so as to comprise two distinct parts, one of which is a pilot valve that regulates the normal pressure in a stable and accurate manner and the other a relay valve which controls the pressure in the brake pipe CG according to the normal pressure and an overcharge of, for example, 300/400 grams, such increase in pressure being obtained in the limited overcharge position of the driver's valve RM and facilitating release of the brakes throughout the train.