GB875550A - Device for balancing forces, and uses for such a device - Google Patents

Abstract

875,550. Fluid-pressure servomotor-control systems; valves. SOC. NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. Jan. 19, 1960 [Jan. 23, 1959], No. 1942/60. Class 135. [Also in Group XXXII] The movements of a fuel-flow control valve 23, Fig. 2, are influenced by a balancing system having the characteristics of a spring and comprising an hydraulic chamber 5 to which pressure fluid is supplied from a pump 17 to compartments 6, 7 on opposite sides of a sealing piston 1, flow from the compartments being regulated by variable constriction valves 3a, 4a which are operatively associated with the piston 1 to produce a pressure differential in the compartments 6, 7 according to the equivalent spring force characteristics required. In the example, the device is used in combination with a helical spring 22 and the valves 3a, 4a are so arranged that the changes in pressure differential assist the forces on the valve 23 resulting from fuel pressure to give an overall constant force characteristic so that the valve 23 opens suddenly after a predetermined pressure has been reached in the line 25. In another example, the restriction valves 3a, 4a are arranged in reverse so that a gradual buildup of resistance to movement of the valve 23 is obtained. In another example, the device is arranged in combination with a spring 49, Fig. 3, to produce a constant force characteristic in a fuel delivery quantity regulator. The spring 49 and piston 1 react on a piston 46 to which the pressure differential across a fuel-flow control valve 28 is applied. The opening of the valve 28 is influenced by engine speed through a cam 29, but in the event of a drop in pressure in the fuel supply line 37, the change in pressure differential across the valve 28 causes the piston 46 to move against the constant force to open or close a by-pass constriction valve 41 until the predetermined pressure drop across the valve 28 is restored.