GB842361A - Improvements in or relating to automatic self-regulating swash-plate pumps - Google Patents

Abstract

842,361. Swash-plate pumps. RECHERCHES ETUDES PRODUCTION R. E. P. Sept. 4, 1956 [Sept. 5, 1955], No. 27062/56. Class 102(1). A swash-plate pump, of the type described in Specification 842,360, comprises pistons 9, Fig. 1, reciprocating in cylinders 7, each cylinder being provided with inlet ports 8 and an outlet valve 10 whereby liquid is delivered through conduits 11 to a chamber 12 and the pump outlet 6. Each cylinder is surrounded by a sleeve 33 which is movable axially by a spider member 31 in accordance with the delivery pressure in the chamber 12 acting on a piston member 29. Each cylinder 7 is provided with at least one set of ports 34, Fig. 2, arranged on a spiral while the sleeve 33 is provided with a helical groove 35, for each set of ports 34, the pitch of which is close to that of the ports, the arrangement being such that at a low delivery pressure of the pump the groove 35 does not communicate with the ports 34 but as the delivery pressure increases the sleeves 33 are moved axially and the groove 35 registers successively with each of the ports 34, thus at a predetermined pressure the groove 35 is in communication with all the posts 34. Such an arrangement provides a regulation of the pump delivery in that the pistons 9 are provided with an axial bore communicating with a groove 37 which successively register with the ports 34 during the delivery stroke, thus as the sleeve 33 moves to register the groove 35 and the ports 34 part of the liquid in cylinder 7 is by-passed during the delivery stroke, the groove 35 being open by ports to the pump inlet. When the delivery pressure is such that the sleeves 35 are moved to by-pass the whole of the liquid in the cylinders a small amount of liquid is still required to be pumped to allow for leakages, thus delivery is achieved by one pump piston 9S, shown in the lower half of Fig. 2. The piston 9S is provided with a groove 37S, which is narrower than the groove 37 of the remaining pistons, and the cylinder housing this piston is provided with an extra port 34 offset from the spiral and this provides for wire-drawing, which would normally occur on the last port 34 of each cylinder, to be confined to a single cylinder. Reference has been directed by the Comptroller to Specification 738,906.