GB903526A - Improvements relating to variable load vehicle braking apparatus operable by compressed fluid - Google Patents

Abstract

903,526. Variable load vehicle-braking apparatus. WESTINGHOUSE BREMSEN G.m.b.H. May 5, 1960 [May 8, 1959], No. 15878/60. Class 103 (1). In a load variable fluid-pressure braking system, operable by compressed fluid, there is provided a valve arrangement having, on the one hand, a control valve device 3 in which the valve control members 14 and 21 are adjusted relatively towards and away from each other respectively in dependence upon the vehicle load, and in dependence upon the magnitude of a brake application controlling pressure so as to provide a load modified pressure and, on the other hand, a relay valve device 6 for admitting compressed fluid to and releasing it from a brake cylinder 8, which relay valve device is responsive to the load modified pressure acting together with the brake application controlling pressure in opposition to the brake cylinder pressure. If the vehicle is unloaded, and the foot valve 9 is depressed, compressed air is supplied to the pipe 5b from the reservoir 10. The air flows through port 30b, chamber 28 and port 30a of the relay valve device 6 (Fig. 5), and through pipe 5a of the control valve device 3 (Fig. 4). Since the control piston 14 of the valve device 6 is not moved sufficiently by adjusting screw 47 acting through pivoted lever 12, when the vehicle is unloaded, to cause the valve 21 to be lifted, the chamber 19 and pipe 4 remain vented through ports 17, 18 and 42. As the pressure in the brake cylinder 8 and in the pipe 7 builds up in the relay valve device 6, a counter-acting force builds up through the throttle opening 7a in the ring chamber 43, until the force on ring area b is equal to the force on area c whereby the piston 29 and its sleeve 31 move to a lap position, in which the surface 34 of sleeve 31 meets the valve disc 35 and shuts off the chamber 28 from chamber 39. The brakes are now applied according to the " EMPTY " line of the graph shown in Fig. 2. When the vehicle is fully loaded, the control piston 14 of device 3 is moved to its upper position by the levers 2, 44, the crank 13, and the follower member 12, its valve seat 20 thus engaging the valve head 21a. When the foot pedal valve 9 is now depressed, air is conducted into brake cylinder pipe 7, and due to the increased pressure now acting in space 41 at the top of the relay valve device 6, the brakes are applied according to the " FULL LOAD " line shown in Fig. 2.