Patent GB-998506-A (GB)
Title: Variable output reciprocation pump
Inventor: STEWART PHILLIP GORDON
IPC: F04B49/24
Filed: 1961-07-20
Abstract: 998,506. Reciprocating pumps. APPLIED POWER INDUSTRIES Inc. July 20, 1961, No. 26269/61. Heading F1A. A fluid, for example hydraulic, pump comprises pistons with valve means therein which are in communication with a fluid supply inlet chamber to admit fluid through the pistons to the pumping chambers during suction, each of which pumping chambers are in communication with an outlet port through which pressure fluid is discharged during a piston discharge stroke, fluid by-pass means between at least some of the pumping chambers and the inlet chamber for diverting fluid pumped by the pistons into the inlet chamber, and means connected and synchronized with piston reciprocating means to actuate the by-pass means. A drive shaft 25, Fig. 1, is keyed at 31 to a swash plate 30 behind which is a thrust bearing assembly 34 and which carries a thrust plate 32 on a bearing assembly 33. The swash plate 30 reciprocates pistons 42 in cylinders 40 secured by pins 41. Each piston contains ports 49 and a valve 46 through which liquid passes from an inlet chamber 19, fed by inlet 20, to a pumping chamber 48, during the suction stroke of the piston. On the discharge stroke of a piston 42, the liquid is delivered through a valve 50 to a common annular discharge passage 21 connected with an outlet 22. Any one of plugs 23 in bores coaxial with cylinders 40, may be removed for connection of means to divert the delivery from the associated cylinder to a separate use. Cross bores 77 connect with annular grooves 76 which communicate with valves 75 actuated by a cam 55 to control the output of the pump during the discharge strokes of the pistons by by-passing some of the liquid into a chamber 52 and through ports 53 back into the inlet chamber 19. The cam 55 opens the valves 75 approximately 15 degrees after the valves 46, whereby liquid is admitted to the pumping chambers 48 by way of valves 75 in addition to the valves 46. The cam 55 is slidable in a bore 37 in the drive shaft 25 and is secured against rotation relative thereto by a key 56; a spring 58 continuously urges the cam to the right. Axial movement of the cam 55 may be performed automatically, particularly hydraulically, or by manual control as by rotating knob 67, in which is keyed at 73 a shaft 71 so as to be axially slidable therein, the shaft 71 being threaded to a nut 68 which is fixed against rotation by a pin 69. The construction of the cam 55 (see also Fig. 6) is such that movement of the cam axially alters the output of the pump by altering the positions, during discharge, at which the by-pass valves 75 close. A modification of the by-pass valve control mechanism is shown in Fig. 14 in which a control shaft 90 comprises an eccentric 96 and a cylinder 91 having, in its outer periphery, a spiral groove 94 in which rests a ball 95 located in the drive shaft 25. A multi-faced collar 98 is mounted on bearings 97 around the eccentric 96. Faces 99 of the collar 98 engage shoes 100 of by-pass valves 84a which are thereby opened in succession on rotation of the eccentric. Axial adjustment of the control shaft 90 is performed by rotation of knob 67a which in turn, by the action of the ball 95 riding in the spiral groove 94, rotates the shaft 90 relative to the swash plate 44, thereby altering the position at which the by-pass valves 84a will be opened.