GB1150522A - Hydraulic Actuator Control Valve - Google Patents

Abstract

1,150,522. Hydraulic motor control circuits. CESSNA AIRCRAFT CO. June 7, 1967 [Nov. 30, 1966], No. 26248/67. Heading F1P. [Also in Division F2] A double-acting hydraulic motor 60, Fig. 1 for moving an inertia load 65 and having cushioning orifices 68, 69 progressively restricted by the movable member 63 of the motor near each end of its stroke has its inlet chamber, say 88 connected to a return reservoir 18 through a by-pass line 87 when a normally closed spring-biased valve member 73 therein is opened to the position shown by the pressure rise in the exhaust chamber 99 being transmitted through a line 95 to the underside of a pilot piston 78 for lifting valve member 73 against its spring 75. The valve 73 comprises a hollow spool slidable within a sleeve 74 within a bore 70 of a valve casing 72 and has lateral ports 90 which when in register with ports 89 in sleeve 74 allow fluid to pass from by-pass line 87 into the centre passage 91 of spool 73 and past a ball check 107 into the return line 93. Supply is provided by a pump 15 delivering through a conventional combined inlet and outlet valve 40 and in the event valve 40 being reversed in mid-stroke, the resulting pressure rise in chamber 99 caused by the inertia of the load and by the supply pressure is relieved through a valve 100 to chamber 88 and prevents cavitation therein. Fixed restrictions 85 in lines 86, 92 serve to limit the maximum speed of the piston 63. In a modified control circuit a sudden increase in pressure, in say chamber 99, Fig. 4, is relieved through line 95, valve 100, a line 117, check valve 105 and line 96 to chamber 88 thus preventing cavitation therein. Cavitation is also prevented by connecting a return line 120 maintained under a low pressure to line 117 between relief valves 100, 102 whereby if pressure in either chambers 88, 99 becomes negative fluid will flow from line 120 across the appropriate check valve 103, 105 into chamber 88 or 99.