GB574148A - Improvements in fluid-pressure-operated means for controlling apparatus at a distance - Google Patents

Abstract

574,148. Fluid-pressure servomotorcontrol systems ; valves. DODSON, E. Jan. 6, 1944, No. 252. [Class 135] In a sender unit 13 for a hydraulic remote control system of the kind comprising a selflapping piston valve 31 operable in a cylinder 24 having inlet, outlet and exhaust ports 32, 34, 33 respectively, by means of an operating member such as the pilot's lever 15 through a balancing spring 45, a reducing valve is interposed between a high-pressure inlet 12 and the inlet port 32 so as to maintain the pressure at the inlet port 32 a predetermined amount above that at the outlet port 34. As shown, the reducing valve comprises a spring-loaded non- return valve 26 adapted to be moved off its seat by a spigot 51 on a spring-loaded piston 29 exposed at its spring-loaded end to the pressure in the outlet through a channel 39 and at its opposite end to the pressure in a conduit 41 connecting the non-return valve with inlet port 32. Passages 43, 44 enable fluid in the conduit 41 to pass to the exhaust 33 following a movement of the lever 15 to reduce the pressure in the outlet. A spring 53 of the same strength as the spring 30 loading the piston 29, is located in the same chamber 54 as the balancing spring 45 and acts in the opposite direction for the purpose of balancing the excess pressure which a plunger 49 exposed to the pressure in the conduit 41 and linked to the hand lever exerts on the latter above that exerted in a contrary sense by the loading spring 45. The pilot's lever 15 is thus balanced in all positions. The balancing spring 45 abuts a plunger 46 of the same effective cross-section as the valve 31, both being subject to exhaust pressure at their adjacent ends. Pressure liquid is supplied to the non-return valve from a pump 11 and return to a tank 10 by the pipe 20. The outlet port 34 leads through a duplicate signal line 14 to a receiver unit 16 as described in Specification 574,147. The unit 16 controls a jack 19 operating the control surface of an aircraft through an arm 22. Valves similar to those described in Specification 482,935 are provided at both ends of the pipes 14 to cut off one of the pipes in case of breakage or leakage. As shown, one pair of valves are built into the unit 13 and comprise valve members 38 carried by a common diaphragm 36 and normally held open by springs 37. Specification 551,257 also is referred to. According to the Provisional .Specification the pilot's lever may control an engine throttle.