GB1328204A - Fluid pressure control systems - Google Patents

Abstract

1328204 Fluid pressure servocontrol systems AUTOMOTIVE PRODUCTS CO Ltd 13 Oct 1970 [15 Oct 1969] 50674/69 Heading G3P A multi-channel control system for aircraft wing flaps comprises, in each channel, a first floating lever 38 connected at 53 to one end of control spool 23 and a second floating lever 37 connected at 53 to a sleeve 56 on the other end of spool 23. Levers 37, of each channel connect via 42, 44 and respective spring boxes (46) to a first control linkage (47, 49), whilst levers 38 connect via 43, 45 and further spring boxes to a second control linkage (48, 51) coupled to the first linkage via spring box (52). During normal operation, each spool 23 connects the control liner 29, 31 of a corresponding servomotor 12 defined by fixed piston 15 and moving cylinder 13 to supply 32 and exhaust 36 which connect with source 10 and reservoir 11 via release valve 33 whose spool 69 is held as shown against bias 101 by pressure in chamber 74 connected to source 10 via 32, 89, passages 94, 95 in pilot spool 64 and 92, 75, 105. If a control spool 2B or one of the levers 37, 38 should seize, the relative movement of spool 23 and sleeve 56 causes ball 58 to raise pilot spool 64 thereby connecting line 92 to exhaust line 97 to depressurize chamber 74, allowing spring 101 to move release spool 69 leftwards to interconnect opposite sides of piston 15 via 84, 82, 78, 77, 83, 85. The supply pressure is effective in chamber 91 to maintain the pilot spool raised. Accumulator 86 is connected to the by-pass circuit of piston 15 to prevent cavitation such as might be caused by restrictor 84, 85. Snub valves 104 as disclosed in Specification 1327393 cushion servomotor movement at the ends of the working stroke. Micro-switch 103 provides an indication of channel failure. Relief valves 99 relieve excess control pressure. In a system employing a single-acting servomotor, the release valve simply allows free flow into and out of the servomotor upon channel failure. The common control linkage may alternatively comprise a cable or telemotor.