Patent GB-569658-A (GB)
Title: Improvements in hydraulic power-transmission or remote-control systems
IPC: B64C25/22
Filed: 1941-11-17
Abstract: 569,658. Hydraulic power transmission. DEXTER, G. Nov. 17, 1941, No. 14766. [Class 69 (ii)] [Also in Group XXVIII] A hydraulic control system for the remote control of a series of parts on aircraft which are operable at different pressures, such as retractable undercarriages, wing-flaps and gun-turrets, is constructed with a pump, the output of which is automatically adjusted to develop the necessary pressures required for the operation of the desired part, and a selector device is provided to cause the pump to deliver its output to the required circuit. As applied to a pump, Fig. 1, in which radially reciprocating pistons 14 are controlled by a guide track 15 of variable eccentricity relative to the rotor of the pump, the position of the track is controlled by pistons in cylinders 17, 18 which respectively tend to move the track to concentric and eccentric positions so as to cut-out or cut-in the pump delivery. The cylinder 17 is supplied with liquid at delivery pressure and moves the track 15 first by the combined action of a floating piston 22 and a piston 20, and finally by the action of piston 20 only. The cylinder 18 is fitted with a plunger 21 which is acted upon by a spring 31 and is also acted upon by liquid pressure supplied at a pressure depending upon the setting of a selective device for controlling which of the parts is to be operative. As shown in Fig. 2, the selective device comprises a lever 32 with a wedge 42 adapted to operate valves 33, 34, 35, 36 for controlling circuits 38, 39, 40, 41 adapted to work at increasily high pressures, the pump delivery pipe 37 being shown as connected by valve 33 to a low pressure or idling circuit, the cut-in cylinder 18 in this case being connected via connections 43, 47 to the tank of the pump. When the lever 32 is operated to connect one of the high-pressure circuits to the pump, it depresses a piston valve 70 having a grooved part 79, and reduced end part 69, and in addition to connecting the pump delivery to the required circuit, this delivery is also connected to the cut-in cylinder 18 via ports 81, 84, the groove 79, a port 65, a valve 53, port 58, and connection 30. The eccentricity of the track 15 is thus increased and the pump output increases to produce the desired pressure. Depression of the plunger 70 in the first place depresses the valve 53 by the action of plungers 51, 52 connected by a spring 50, but when the pressure in cylinder 49, which is connected to the pump delivery, increases to the desired extent, the valve 53 cuts the connection of the cylinder 18 to the pump delivery. If the pressure rises still higher, the valve 53 connects the cylinder 18 to exhaust and thus cuts down the pump pressure. Any leakage past the valve 70 returns to tank. In a modification, Fig. 3, an arrangement of valves effects an automatic selection when the circuits to the required part are established by opening delivery valves connected to screw-connections at the bottom of valve chambers 91, 92, 93 fitted with non- return valves 99, 115, 129. The pump delivery is connected to a through-way passage 88, and when no pressure circuit is in operation the output passes via connection 90 to a lowpressure circuit, the cut-in connection 30 being connected via a valve 149 to tank. On opening one of the high-power circuits, the valve (say) 115 of the chamber 92 of this circuit opens, and by the action of intermediate valve chambers 94, 95, 96 and the depression of a valve 118 in chamber 92 pressure is built up to depress a piston 151 and so to disconnect the cut-in cylinder from the tank and finally connect it to the high-pressure circuit and so increase the pump outlet and control it as described in connection with the first modification. Other forms of pump may be employed, such as pumps with variable swashplates, or pumps with fixed radial cylinders and rotating crank-shaft fitted with a crank sleeve which is displaceable from an eccentric to concentric position. The invention may be applied to hoisting gear.