Patent GB-557822-A (GB)
Title: Improvements in or relating to fluid pressure generating devices
IPC: F04B1/18
Filed: 1942-06-04
Abstract: 557,822. Swash-plate pumps. WAHLMARK, G. A. June 4, 1942, No. 7642. Convention date, Sept. 15, 1941. [Class 102 (i)] A swash-plate pump comprises a non- rotatable block 9, Fig. 1, with an annular series of parallel cylinders 14 for pistons 16, and a stepped opening 18, 19 for an annular cam 77 controlling the angularity of a swashplate 17, and a hydraulic cylinder 105 for reversing the inclination of the swash-plate. Ports 15 lead from the cylinders 14 to a chamber 13 in an end closure 11 containing a spoked valve 42, of the kind described in Specification 516,721, [Group XXIX], eccentrically mounted on the driving shaft 26. The swash-plate 17 comprises an inner member 70 pivoted at 71 to the shaft 26, and a relatively rotatable outer member 72 to engage the pistons 16. The closure 11 has a port 35, Fig. 4, communicating with the outer portion of the chamber 13 by an arcuate recess 37, and a port 36 communicating with the chamber 13 between its centre and its periphery by an annular recess 40, these communicating passages being fitted with adjustable spring-controlled high pressure relief valves 50, 51 for relieving fluid from the high pressure passage to the low pressure passage. The cam 77 is moved longitudinally to adjust the swash-plate towards no-stroke position by a hydraulic cylinder 80 containing a piston 84 which operates a pivoted lever 93 moving in an elongated slot 99 in the cam. The reversing cylinder 105 moves over a piston 103 fixed to the shaft 26 and has a guided extension 106 carrying an arm 108 to engage the inner member 70 of the swash-plate. Operating fluid is supplied to the two ends of the cylinder 105 by radial passages 114, 115 connected to grooves 117, 120 fed by the means described in Specification 557,821. Make-up and control fluid is supplied by a gear pump 125 of the kind described in Specification 516,565, [Group XXIX], and is delivered by a passage 134 to the upper end of a bore 136 containing a pressure-governing relief valve 142 controlling a port 146 leading by a passage 147 to the interior of the pump casing, and thence by a port 148 to a reservoir. The valve 142 is also acted upon by a differential plunger 151 subjected to the working pressure of the main pump in both of its directions of rotation by means of passages 156, 157 leading to the periphery of the chamber 13 and to the recess 40. Make-up fluid, and fluid for pre-loading the cam 77 is supplied at a constant pressure, regardless of the variations produced by the valve 142, by means of a valve 164 operating in a bore 161 which is continuously supplied by the pump 125 by means of the annular space around the boss 141 of the valve 142, a passage 172, and a port 171. The upper end of the bore 161 communicates by passages 174, 175, 176, Fig. 5, with bores 177, 178 containing strainers 179 and non-return valves 180 connected to the recesses 37, 40 of the valve 42. This constant pressure fluid is supplied to the bore 136 to move valve 142 to close port 146, and thence by a passage 186 to a piston portion 78 of the cam 77 to preload it.