| 摘要 |
1,160,958. Jet propulsion nozzles. PLESSEY CO. Ltd. Nov. 28, 1966 [Dec. 3, 1965], No.51405/65. Heading F1J. [Also in Division G3] A hydraulic actuator for use with a fixed displacement pump 15 comprises a differential piston 18 with its smaller area side 23 permanently connected to the delivery side of the pump, a sensoractuated ram control valve 25 selectively to connect the larger area side 27 of the piston 18 to the pump delivery line 21 or to a spill outlet 17, a further spill outlet 37 from the pump delivery line provided with a pump load control valve 34 urged by a spring 36 to a closed position, and fluidpressure means 26, 29, 35 communicating with the side 27 of the piston to urge the valve 34 to an open position. In the preferred embodiment, the piston 18 operates the nozzle flaps of a gas turbine jet engine while the valve 25 is connected to a sensor 12 responding to the ratio of outlet to inlet pressures of the turbine. When the ratio increases and the flaps have to be closed, the valve 25 is moved to the left to connect the side 27 to a return line 17 and to permit the piston 18 to be moved by pump delivery pressure acting on the side 23. During operation of the ram, a relief valve 22 determines the delivery pressure while the valve 34 permits the pump to operate at a lower pressure when the ram is stationary and holds the flap in its set position. The aerodynamic reaction of the flap to the flow in the jet produces a force on the piston 18 and a fluid pressure in the duct 35 to move the valve 34 to a position in which flow into the spill passage 37 maintains the system in equilibrium. This spill passage is closed by a land 40 on the spool 25 when both sides of the piston are connected to the delivery line 21. A delayed ram response is thus avoided when the system has been in equilibrium at a low delivery pressure. When the after burners are out of action, the piston 18 opens and valve 41 to keep the pump delivery pressure at its minimum value. |
