GB927001A - Improvements in and relating to a rail vehicle braking system - Google Patents

Abstract

927,001. Fluid-pressure brakes. WESTING- HOUSE BRAKE & SIGNAL CO. Ltd. Aug. 24, 1961 [Oct. 25, 1960], No. 36622/60. Class 103 (1). In a compressed air braking system for rail vehicles the brake cylinder pressure is varied in response to changes in load carried by the vehicle and means 38 is provided for preventing the final setting and locking of the loadcontrol means 33 until the vehicle is in motion. In the embodiment illustrated in Fig. 1, the vehicle is empty and shown in its stationary position. Rollers 15 and 19 engage unsprung portions of the bogies 16 and 20 respectively and air pressure from a main reservoir pipe 39 acts against, and moves a piston 23 in a brakesetting mechanism 21 to the left, compressing the spring 25 and so forcing the rollers 15 and 19 through their respective linkages, downwardly into engagement with their respective bogies. This movement urges the piston-rod 24 into engagement with a piston-rod 29 and moves a centrally mounted piston 28 to the left against its spring 34, carrying with it the roller 31, which forms a movable fulcrum for the weigh beam 32 of the variable load-control valve 33 to vary the brake cylinder pressure according to the position of the roller 31 relative to the weight beam 32. When the vehicle moves and attains the speed of more than two or three miles an hour the standstill detector 38 cuts off the air from pipe 40 and exhausts it through pipe 41. This allows the spring 37 to move the piston 36 and pawl 35 upwardly to engage the ratchet teeth 30 on piston-rod 29 and so lock the piston-rod 29 in its extreme leftward position. Air escapes at a slower rate from behind the setting mechanism 23 due to the choke 42 and the piston towards the right under the influence of its spring 25. This causes the rollers 15 and 19 to move upwardly out of engagement with their respective bogies so that wear and vibration, due to movement of the bogies when running, do not have an adverse effect on the mechanism. If the vehicle is loaded during the period when it is stationary, the downward movement of the under frame 10 relative to the bogies 16 and 20, causes the rollers 15 and 19 to be moved upwardly to the position shown in the dotted lines in Fig. 1. This results in the linkage moving the swinging lever 18 to the position shown in the dotted lines in Fig. 1 so that the piston 23 of the setting mechanism 21 is moved to the right against the air pressure acting on its righthand side. Since the pawl 35 is withdrawn from the teeth 30 by air pressure acting on the upper side of the piston 36, the piston 28 will also move to the right under the influence of its spring 34 and so re-position the roller 31 along the weigh beam 32.