GB1436390A - Hydraulic swash plate pump - Google Patents

Abstract

1436390 Fluid-pressure servomotor systems G LEDUC and M LEDUC 14 June 1973 [16 June 1972 27 Oct 1972] 28448/73 Heading G3P [Also in Division F1] A hydraulic swash-plate pump is provided with a slide valve controlling the swash-plate adjusting jack in dependence upon the delivery pressure, the valve being subject to the pressure existing at the back of the jack and also to an opposing spring force. In one arrangement, the pump has at least two delivery flows and the jack is controlled in dependance upon the highest of the delivery pressures. In this arrangement, Figs. 2, 4, the swash-plate 6 is pivotally mounted on a pin (5), Figs. 1, 5 &c. (not shown) attached to drive-shaft 4 and includes bores 14 each provided with a non- return valve 15 and spaced such that in the delivery phase of pistons 3 any one stud 12 of a group corresponding to a respective flow always has its central orifice communicating with a bore 14. Each of the latter connects with a common chamber 16, the pressure therein thus always being the highest of the various delivery flows. Chamber 16 is enclosed by stud 18 against which bears the head of jack piston 8. The latter is extended by a rod 24 passing through a bore 25 to define a calibrated orifice separating chambers 23, 26. A spring-biased slide valve 29 is mounted in a bore 28 within rod 24 and piston 8 and, according to its position, connects chamber 23 and conduit 31 either via conduit 32 to the high-pressure within chamber 16 or via conduit 33 to the low inlet pressure in chamber 13. Thus any change in the highest delivery pressure causes a change in pressure in chamber 26 resulting in movement of slide valve 29 and jack piston 8 until equilibrium is restored. Liquid from chamber 16 is also supplied through a passage (35) in swash-plate 6 to a duct (34), Figs. 5 to 8, (not shown), within the mounting pin (5) and thence through asymmetrically disposed ports (36, 37) to lubricate the pin bearings (38) and at least partially balance the torsional force to which the pin is subjected. In a modification Figs. 11, 12, the pump comprises twelve pistons arranged in four groups 3a, b, c, d the cylinders of which are connected to separate deliveries via non-return valves such as 42c. Each cylinder is connected to a common conduit 43 via non-return valves 40a, b, c, d such that the conduit is at the highest of the delivery pressures. This pressure is communicated to slide valve 29 via passages (44, 45) Fig. 9 (not shown), in the pump housing and a seal ring (46) surrounding the pump drive-shaft 4. In a further modification, Fig. 10, (not shown) only one non-return valve 40a, b, c, or d is provided for each group of cylinders, the latter in each group being inter-connected by a conduit (e.g. 41a). The non-return valves 40a &c. may be disposed downstream of the delivery non- return valves 42a &c. The pump includes, Figs. 2, 4, a centrally disposed inlet duct 17 aligned with a blind hole 9 in swash-plate'6 connecting via passage 10 and arcuate port 11 with pistons 3 during their suction stroke.