GB680532A - Improvements in or relating to an hydraulic apparatus - Google Patents

Abstract

680,532. Reciprocating pumps. ALLISCHALMERS MANUFACTURING CO. April 14, 1949 [May 12, 1948], No. 10154/49. [A Specification was laid open to inspection under Sect. 91 of the Acts, Nov. 13, 1949]. Class 102 (i) [Also in Group XXIX] A hydraulic system comprises a pump 17-20 inclusive which supplies liquid from a reservoir to a control valve chamber 34, Fig. 7 a return passage 47 communicating with the valve chamber, a delivery passage communicating with the valve. chamber and with the return passage and including valves 44, 64 which establish a pressure space 37 therebetween, a control valve 102 in the valve chamber for selectively connecting the pump delivery to either the delivery passage or the return passage or both, and a relief and unloading device 81 operatively connected to the control valve and responsive to the delivery pressure for both controlling the flow of liquid from the pressure space to the return passage and for moving the control valve to a position whereby less liquid is passed to the delivery passage. The pump comprises a plurality of parallel cylinders 17, 18, 19, 20 whose pistons 23 are actuated from a cam shaft 2 through rocker arms 28. The cylinders receive liquid through a manifold 29 and conduits 31 and deliver it through conduits 36 to the valve chamber where the valve 102 distributes it selectively to either the pressure space 37, through passages 96 and delivery valves 39, or to the return passage 47 through passages 48, 49 or both. The control valve, Fig. 2, comprises a series of separable cylindrical elements 103-106 inclusive in abutting relationship which operate in separable liner members 89-92 inclusive. The valve is biased by a spring 112 into engagement with a roller 119 carried by a lever 121 pivoted on a link 122 and its movement to the left is adjustably limited by a screw 116. The spacing of the valve elements and/or the passages in the liners is such that the delivery from the pump cylinders 17, 18, 19 is first by-passed to the return passage whilst the delivery from the cylinder 20, which is of smaller bore, is allowed to pass to the pressure space. The spacing may also be arranged to connect one or more of the cylinders to the pressure space and the others to the return passage. The pressure space 37 communicates through the check valve 44 with a pipe 12 leading to a ram cylinder 11 and also through a passage 52 with the check valve 64 which is normally held closed on its seat by a plunger valve 66 secured to an element 67 loaded by a spring 69. When the pressure in the space 37 exceeds a predetermined value the valve 64 is unseated and pressure liquid passes into a cylinder 50 and acts through a bore 57 to move a spring-loaded piston 81 to the right to uncover a relief passage 53. The piston is connected through rods 82, 83 with the lever 121 which is rocked about its pivot to allow the control valve 102 to move to the left and thereby reduce the flow to the pressure space. A screw 134 limits the movement of the lever and a manual control lever 133 is used to adjust the control valve and to move the latter to release the liquid from the ram cylinder, through passages 45, 99, 49 to the return passage 47.