GB549455A - Improvements in and relating to master cylinders for liquid pressure control systems - Google Patents

Abstract

549,455. Hydraulic apparatus ;fluid-pressure brakes. SCHNELL, S. May 19, 1941, No. 6425. [Class 69 (ii)] [Also in Group XXXIV] In a hydraulic system in which slave units such as motors for applying brakes are operated by a master cylinder 3, the cylinder 3 is mounted so as to have a limited sliding movement in the casing of the liquid reservoir 2. In the inoperative position of the piston 7 liquid can pass to the cylinder 3 from the reservoir past a valve 16, 17 and a loosely fitting valve 24 normally pressed on its seat by a light spring 25. On operation of the piston rod 11 to the left the cylinder 3 moves with it owing to the friction between the cylinder and the skirt 9 of the piston 7 and the friction due to liquid pressure on the packing 10 of the piston. The valve member 16 on the cylinder 3 closes on the seat 17 and pressure then builds up the pipe line 20 by the passing of liquid through an aperture 19 and past a spring-controlled valve member 27 which moves off its seat under fluid pressure and thereby permits fluid to pass via a small aperture 28 and via cut-away portions 32 in the periphery. When the pressure on the piston is released the valve member 27 restricts the return flow from the slave units, but the valve member 24 permits easy flow to the cylinder when the valve member 16 opens. Sub-atmospheric pressures are thus prevented in the cylinder 2. The valve 27 may be omitted, in which case the opening of the valve 24 is assisted by injector-like action. In a modification the valve members 24, 27 are connected by a rod so that the closing of one valve automatically opens the other, and vice-versa.