GB792905A - Improvements relating to hydraulic pressure control systems - Google Patents

Abstract

792,905. Hydraulic control systems; fluidactuated valves. FAIREY AVIATION CO., Ltd. March 21, 1956 [March 21, 1955], No. 8205/55. Classes 69 (2) and 135. [Also in Group XXXIII] In an hydraulic system in which a single operating member is actuated by two motors each having its own pressure supply A, B, and pressure reducing valves 21A, 21B, each valve reduces the pressure from its own supply by approximately one-half but will supply full pressure if the other supply fails. The system, as applied to an aircraft control surface 10 operated by a tandem hydraulic jack unit 11 comprises tanks 15A, 15B, pumps 16A, 16B, accumulators 19A, 19B, the reducing valves 21A, 21B, and non-return valves and filters. Each accumulator is connected to both valves 21A, 21B. Each reducing valve (Fig. 2) comprises a piston 53 movable in a liner 42 in a casing 40. The casing (and liner) have an inlet 47 and an outlet 48 and a drainage connection 49. The piston is moved to the left by a spring 54 and as the fluid pressure increases the fluid exerts a pressure in a chamber 56, via channels 61, 55, and moves the piston 53 against the spring 54, partly closing the inlet 47 until an equilibrium position is reached. The supply B is connected to a port 51 and acts on a piston 71 against the pressure of supply A which is connected to a port 50. If the supply B fails, a plunger 73 moves the piston 71 and a piston-rod 75 thereon engages and moves the piston 53 opening fully the inlet 47 and full pressure is supplied via system A.