GB1328633A - Fluid pressure control systems - Google Patents

Abstract

1328633 Fluid-pressure servo-control AUTOMOTIVE PRODUCTS CO Ltd 13 Oct 1970 [15 Oct 1969] 50675/69 Heading G3P In a multi-channel control system for aircraft wing flaps, interconnected duplicate control linkages (34, 35) are connected to duplicate floating levers 23, 24 by respective connections 25, 27, 29, 32 and 26, 28, 31, 33, and in normal operation levers 23, 24 operate control spool 17 to provide follow-up control of the cylinder 51 of a servo-motor 10 having a fixed piston 52. If one of levers 23, 24 e.g. lever 23 should seize, the remaining lever 24 pivots about its connection to the temporarily locked spool 17 and displaces rod 39 by a distance corresponding to the clearance between plunger 121, 123 and slot 122, pilot spool 49 thereby being raised by ball 45 and lever 46 to dcpressurize chamber 124 above plunger 121, 123 and chamber 74 of a fluid clutch 18. End 73 of spool 17 is thereby decoupled from seized lever 23, and plunger 121, 123 retracted by spring 125 allows springs 43 to return rod 39 and lever 24 to the position shown. If lever 24 seized instead of lever 23, the above sequence would be repeated, except that rod 38 would operate pilot spool 47 to depressurize clutch 19 and left-hand chamber 124. If the control spool 17 should seize, with one or both of levers 23, 24 free, the resulting displacement of rod 38 and/or 39 raises pilot spool 48 via lever 46 to depressurize chamber 83 in bypass spool 76, allowing spring 93 to shift the spool leftwards to disconnect the source 95 and reservoir 102 from the supply and exhaust ports of housing 11 of control spool 17. Spool 76 also interconnects opposite sides of servo-motor piston 52 via 62, 64, 66, 81, 67, 65, 63, allowing cylinder 51 to be moved by the aerodynamic forces on the wingflap. Pilot spools 47-49, when raised, are held in that position by fluidpressure acting on their lower ends. Snub valves 137, 138 as disclosed in Specification 1327393 control outflow from chambers 55, 56 when contacted by piston 52 to dampen cylinder movement at the ends of the working stroke. Microswitch 92 indicates seizure of control spool 17. In systems using a single-acting servo-motor, bypass spool 76 would be replaced by a vent valve for the working chamber.