GB925060A - Improved servo controlled constant-pressure pump - Google Patents

Abstract

925,060. Fluid-pressure servomotor systems. BENDIX CORPORATION. Aug. 28, 1961 Aug. 30, 1960], No. 30980/61. Class 135. A constant pressure pump of the type having an inclined plate rotated by a drive shaft and acting to reciprocate a plurality of pistons in the cylinders cavities formed in the pump casing is provided with a pressureactuated piston acting on the plate to vary the inclination angle of the plate to a plane normal to the drive shaft axis thereby varying the amplitude of piston reciprocation and hence the pump delivery rate. The pressure acting on the piston is controlled by a valve member automatically displaceable to control the communication between a piston on the one hand and the pump output and a drain passage on the other hand, the valve member being positioned in accordance with the pump output pressure in such a way that a decrease in pump output pressure displaces a valve member in a direction to cause said piston to increase said plate inclination angle and hence increase the pump delivery rate and vice versa. The swash plate is adjusted by movements of a piston 52, the swash plate being loaded into contact with this piston by a spring. The control valve 66 is loaded by a spring 68 against the pump output pressure acting on the end of 70 and the land 72 controls the flow of output pressure to a passage 80 and the flow from this pressure through a groove 76, passage 74 to the drain passage 82. A permanent restricted leakage from passage 80 is provided by a restricted bleed passage 94 communicating with passage 74. In one modification this bleed passage is replaced by a chamfer or groove on the left-hand side of the land 72 and in a further modification by two open recesses on either side of a groove 78 communicating with passage 80. In a still further modification, the leakage is provided by a restricted passage through the piston 52.