GB778331A - Improvements in or relating to hydraulic remote control devices - Google Patents

Abstract

778,331. Fluid-pressure servo motor-control systems. CENTRE DE RECHERCHES HYDRAULIQUES ET ELECTRIQUES. April 28, 1955 [May 15, 1954], No. 12285/55. Class 135. An hydraulic servomotor control system for controlling the displacement of an output member in correspondence with the movement of a remote control valve, comprises a motor simultaneously driving three constant output, volumetric pumps, two of which, 4-5, 6-7, supply pressure liquid to opposite ends 17, 18 of a servomotor cylinder 15 having a piston 14 connected to an output member 3 and the third supplying pressure liquid to the chamber 10 of a cylinder 9 slidable on an extension 8 of the motor shaft. The cylinder 9 which is loaded by a spring 11 disposed between the cylinder and a collar on the piston-rod 13 is connected by a line 34 to a remote control leak-off valve 35 and is formed with arms 28, 33 which engage spring-loaded sleeve valves 25, 30 slidable on extensions of the rotary shafts of the pumps 4-5, 6-7. The sleeves 25, 30 are formed with ports 26, 31, respectively, which permit leakoff from one or other side of the piston 14 depending upon the direction of movement of the valve 35. On, for example, movement of the valve 35 to decrease the leak-off therethrough, pressure in the chamber 10 increases to move the cylinder 9 leftwardly against its spring 11 and at the same time allow leftward movement of the sleeve valves 25, 30 to uncover the port 26. Pressure liquid then leaks out of the end 17 of the cylinder 15 to unbalance the pressures acting on the piston 14 so that it moves to the right to displace the output member. At the same time the spring loading is increased which returns the cylinder 9 and the sleeve valves 25, 30 to their initial equilibrium positions. The continuous rotation of the extension 8 and the extensions of the shafts of the pumps 4-5, 6-7 prevents sticking and reduces friction between 'these parts, the cylinder 9 and the sleeve valves 25, 30. The cylinder 9 and sleeve valves 25, 30 may be replaced by plungers slidable in hollow extensions of the motor and pump shafts and the double-acting, servomotor may be replaced by a rotary motor which through a screw mechanism reciprocates the output member. Several output members having the same or different displacements may be controlled simultaneously. Their displacements being dependent upon the areas of their respective pistons.