GB1273809A - Hydraulic rotary pump unit - Google Patents

Abstract

1,273,809. Reciprocating pumps. SUNDSTRAND CORP. Sept. 16, 1969 [Oct.21, 1968], No.45681/69. Heading F1A. In a swash-plate pump unit comprising a main pump 10 supplied by a feed pump 20, a valve 28 in the feed pump output line acts to supply feed pump pressure to swash-plate-biasing piston 51 only when the inlet demand of pump 10 has been satisfied. Piston 51 biases swash-plate 17 to increase the pump displacement, and a control piston 59 and spring 56 bias the swash-plate to decrease the displacement. Piston 59 is controlled automatically by valve 12 subjected to the main pump output pressure, to maintain the output pressure constant at a level determined by the setting of spring 65. A solenoid valve 80 is actuated to reduce the pump output pressure. In its right-hand position, valve member 91 of valve 28 only connects main pump inlet 26 to the feed pump. When the inlet demand of the main pump is satisfied, the feed pump output pressure increases in valve chamber 97 and moves the valve member to the left against spring 98. Valve member land 94 then connects biasing piston 51 to feed pump pressure via port 103, and piston 51 biases swash-plate 17 to increase the main pump displacement to a level determined by control piston 59. Continued leftward movement of valve member 91 connects feed pump output via passages 109, 108 to a port 111 supplying fluid for cooling the rotating parts of the main pump, the coolant returning to reservoir 22 via heat exchanger 116. Finally valve member 91 connects chamber 97 to passage 36 to by-pass the feed pump output to the feed pump inlet, and acts to maintain the feed pressure to the main pump constant. A check valve 121 permits return flow from biasing piston 51 when port 103 is closed by land 94 during the return movement of valve member 91. Feed pump 20 draws from reservoir 22 through a filter 118.