GB768985A - Driver's brake valve for fluid pressure braking apparatus for railway and like vehicles - Google Patents

Abstract

768,985. Fluid pressure railway brakes. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. May 6, 1955 [May 7, 1954], No. 13174/55. Addition to 739,785. Class 103 (1). A driver's brake valve for railway fluidpressure braking systems of the kind described in the parent Specification, is modified to take account of the fact that, with very long trains of 80 vehicles or more, although the control handle may have been moved to the " running position " in which the main reservoir feeds the brake pipe through the relay valve part, the release of the brakes on the vehicles at the rear of the train depends on the time the driver had left the brake valve in the first position. The new arrangement provides for two further positions of the valve, a limited overcharge position as shown in Fig. 2, and an overcharge reduction position as shown in Fig. 3. In the limited overcharge position, Fig. 2, the pressure in the main reservoir RT acting below a supplementary piston 72 increases the force acting on the piston 39 and therefore produces in the brake pipe CG a pressure which is greater than that which is given by the pilot valve portion 2 in the chamber under piston 39. In the overcharge reduction position, Fig. 3, air under pressure below piston 72 is allowed to escape to atmosphere through exhaust choke 90 so that ultimately only pressure in chamber 3 below acts on piston 39 and pressure on the brake pipe CG becomes equal to normal.