GB728456A - Improvements in or relating to reciprocating pumps - Google Patents

Abstract

728,456. Reciprocating pumps. NEW YORK AIR BRAKE CO. May 8, 1952 [May 21, 1951], No. 11631/52. Class 102 (1). A hydraulic pump comprises a stationary block 21 having cylinders whose plungers 24 are actuated by a swash-plate 51 driven by a shaft 27 Oil enters the pump at 19 and passes around the pump reciprocating mechanism through passages 32, chamber 31 and a passage 29 to inlet chambers 28 in the cylinders, oil being delivered through spring- loaded discharge valves 41 to a common outlet 13. Towards the end of the delivery stroke, ports 58 in the plungers communicate with the sump through ducts 34, an annular recess 35 and a common by-pass outlet 14. A ring non-return'check valve 37 housed in the recess 35 and pressed inwardly by a garter spring 38 may be fitted when high back pressures in the sump line are encountered to inhibit back flow. Each plunger also has a series of spill ports 59 which co-operate with sleeve valves 61 the axial positions of which are varied automatically as described in Specification 626,218 for varying the effective strokes of the plungers. The pump preferably has nine plungers and the sleeve valve associated with one of the plungers is lengthened so that when the pump is in its "no delivery" position, i.e. when the pump discharge pressure acting on the differential piston 65, 66 against the springs 74, 75 moves the sleeve valves through the spider 63 to their extreme right positions, the spill ports 59 in this plunger are covered. This plunger will hence continue to pump a small quantity of liquid at each stroke whilst the other eight cylinders have ceased'delivery. Thus losses in the system to which the oil is being delivered are made up, power consumption at or near delivery is minimised and a circulation of oil is maintained around the pump reciprocating mechanism to ensure adequate lubrication and cooling. Specification 728,493 also is referred to.