GB551527A - Improvements in or relating to distant control gear for hydraulic apparatus - Google Patents

Abstract

551,527. Hydraulic control systems MESSIER, Ltd., R. O., and CONWAY, H. G. July 24, 1941, No. 9416. [Class 69 (ii)] An electrically controlled hydraulic control sys'em which is especially applicable for operating jacks or aircraft to control the undercarriages &c. is constructed with a control valve box 12, Fig. 1, for directing the liquid delivered by a pump 14 to the required end of the jack so as to move the carriage up or down. The valve 20 which may be a piston or other valve is actuated by energizing one or other of two electromagnets 25, 26 by actuating a lever 36 with push-buttons 34, 35 for closing contacts 38, 39 or 41, 42, and at the same time other contacts are closed to energize an electromagnet 48 which opens a normally closed valve 46 to permit pneumatic pressure from a pipe 43 to be directed to a clutch which drives the pump 14 from the aircraft engine. The valve 46 is held open by a spring- controlled latch 66 which is released by energization of an electromagnet 65 when the carriage has completed its movement in either direction and pressure builds up and operates a piston 59 causing closing of contacts 62, 63. When the latch 66 is released the magnet 65 is automatically de-energized by the breaking of contacts 72 by the motion of the core 70. For control in emergencies a hand-pump 73 supplied by a reservoir 74 can be used to direct liquid under pressure to a pipe 78 which is directed by a shuttle valve 81 to the jack and thus lowers the undercarriage, the pressure fluid passage from the pump being cut off and a by-pass valve 84 opened to connect the lower end of the jack cylinder to exhaust. In a modification the clutch for driving the pump 14 is controlled by a spring toggle device actuated by electromagnets energized similarly to the magnet 65 by pressure-actuated contacts 62, 63. In a further modification, Fig. 3, the pump 14 is driven continuously but is normally by-passed to exhaust via an outlet 109 of a chamber 100 fitted with a piston valve 103 held by a spring-plunger 107 against the action of a spring 104. The plunger can be withdrawn by energize ion of a magnet 110 and the spring then raises the piston 103 so as to cut off the by-pass. The magnet 110 is de-energized automatically, and the plunger 107 then engages a groove in the piston 103, and holds it raised until the rise in pressure at the end of the movement of the jack overcomes the action of spring 108 on the plunger 107 and the piston valve is forced down to the position shown in Fig. 3, thus again by-pasing the pump. Specifications 492,300 and 544,493, [Group XXXIII], are referred to.