Patent GB-674095-A (GB)
Title: Control for fluid pressure system incorporating a variable displacement pump
IPC: F04B1/04
Filed: 1949-12-13
Abstract: 674,095. Fluid-pressure servomotor and hydraulic control systems. SORENSEN, C. S. Dec. 13, 1949, No. 32007/49. Classes 69 (ii) and 135 [Also in Group XXVIII] A fluid-pressure control system for a variable displacement pump comprises first and second regulators subject to the outlet pressure of the pump and varying the displacement of the pump according to predetermined high and low output pressures, respectively, and a cut-off valve interposed between the pump outlet and the low pressure regulator to enable control of the pump to be transferred from this regulator to the high pressure regulator. The pump comprises two banks of cylinders and pistons 28, Fig. 2, radially arranged around, and rotated by, a hollow shaft 6. The outer ends of the pistons carry freely rotatable balls bearing against the inside surface of anti-friction bearing rings 26, the latter being urged by spring-loaded pistons 43 into an eccentric position giving maximum delivery. The spring loading of pistons 43 is supplemented by the output pressure of the pump applied through a passage 64. Squared-off plates 27 ensure that the bearing rings can slide in one direction only in the pump casing. Fluid enters the hollow shaft 6, and flows into ports in the cylinders through lateral ports in the shaft and passages in a block which is held up against the side. face of the cylinders and which is prevented from rotating by means of pins projecting from the pump casing. The delivery from the cylinders takes place through ports in cylinders and further passages in the blocks. The pump casing carries two relief valves 70, 48 set to blow at low and high pressures, respectively, and, when either valve is opened, the escaping pressure fluid flows to and actuates a piston 47 which overcomes the piston 43 and moves the bearing 26 towards neutral position to reduce pump delivery. Each valve comprises a passage 51, Fig. 4, through which the pressure fluid is led to act on a piston 53, the latter being loaded by a spring 59. Before the valve is actuated, fluid at the back of piston 47 exhausts through passages 60, 67, chamber 55 ; and port 68, but when the piston is lifted it first closes off port 68 and then admits the pressure fluid through passage 60 to the back of piston 47. The invention is shown applied to the actuation of various aircraft services 78, 82, Fig. 6, for which two separate hydraulic supplies (high and low pressure, respectively) are required. Normally, the pressure fluid delivered by the pump flows through line 74, a cut-off valve 73, and a line 72 to the lowpressure relief valve 70, the services 82 being supplied at the low pressure set by valve 70. A pressure regulating valve 86 is included in the line 95 leading to services 82, this valve consisting of an auxiliary valve, similar to valve 70, wherein the discharge flows to and actuates a piston controlling a main valve in the line 95. On actuation of a reversing valve 76 to apply fluid at a high pressure for actuation of services 78, a mechanical connection 91 cuts off valve 73 from the pump delivery line so that the pump delivery acts on valve 48 which allows the pump to deliver at a high pressure before it blows. Low- and high-pressure safety valves 84, 85, respectively, are inserted in the appropriate lines and lead back to a supply tank 80.