GB721645A - Improvements in or relating to pressure-governing apparatus for hydraulic circuits - Google Patents

Abstract

721,645. Fluid-pressure servomotor control systems. SOC. D'INVENTIONS AERONAUTIQUES ET MECANIQUES S.I.A.M. Oct. 15, 1952 [Oct. 15, 1951], No. 25896/52. Class 135. In a pressure-regulating valve for a hydraulic system supplied with pressure fluid by a pump 2 and of the type in which a pump unloading valve A is actuated by a piston Y under the control of a spring-loaded pilot valve B, and in which the two sides of the piston are interconnected by a restricted passage A<SP>2</SP> and the pilot valve, subject to the pressure in the chamber a at the back of the piston, opens towards the exhaust connection on a predetermined pump output pressure being attained and so exhausts the chamber a, a movable member P responsive to the pressure in the hydraulic system (e.g. in accumulator 4) serves, after the pilot valve has opened, to hold, or assist in holding, the pilot valve open until the system pressure falls below a predetermined value. The pump 2 receives liquid from a tank 1 and supplies it under pressure past a non- return valve 3 to the accumulator 4 and a hydraulic circuit 5. When pressure is released in the chamber a due to the opening of pilot valve B, the pump outlet pressure acting on the front face of piston Y forces the latter to the left and so opens the valve A which by-passes the pump outlet to tank 1 through conduit h. An intermediate annular chamber d communicates with passage A through a restriction f and so acts as a dashpot to prevent sudden movements of valve A.