Patent GB-1487542-A (GB)
Title: Axial-piston variable-delivery pump and hydraulic drive
IPC: B30B15/24
Filed: 1976-03-30
Abstract: 1487542 Reciprocating pumps; hydraulic control circuits VSES NI I PROEKTNO - KONSTRUKT INST PROMYSHLEN GIDROPRIVODOV I GIDROAVTOMATIKI 30 March 1976 12804/76 Headings F1A and F1P A variable-delivery swash-plate pump, e.g. for supplying actuating liquid to the hydraulic actuators of a sheet-bending press Fig. 8, comprises a plurality of pumping chambers 8 with pairs of opposed pistons 6 reciprocated by swashplates 9 on a shaft 7, each chamber 8 communicating with inlet and outlet manifolds 2, 3 via spring-loaded inlet and outlet valves 18, 19, a plunger assembly 22, 25 acting on the inlet valve stem 24 being hydraulically controlled by a sleeve valve 28 rotating with shaft 7 and axially movable by a control rod 31 to effect opening of the inlet valve for the intake stroke, and also during the delivery stroke to vary the pump delivery. Axial movement of valve 28 varies the opening time of the inlet valve during delivery due to a tapered land arrangement on valve 28, Figs. 2 and 3 (not shown). Control pressure is supplied to valve 28 via passage 4. The effect of valve 28 may be over-ridden by supplying control pressure between plungers 22, 25 via passages 27, 26 to hold the inlet valve open. In Fig. 4 (not shown), plungers 22, 25 are replaced by a plunger (56) having a stem (57) on which an annular plunger (58) is slidable. In Fig. 5 (not shown), plungers 22, 25 are replaced by a plunger (59) having an annular groove (60) engageable by a stem (62) of a hydraulically-actuated piston (61) which acts to lock the inlet valve in its open position. Half of the pumping chambers may be arranged to supply a different outlet conduit from the other half, the two sets of inlet valves also being independently controlled to independently vary the two deliveries, Figs. 6 and 7 (not shown). The press actuating system, Fig. 8, comprises double-acting, piston-cylinder units 68, 69 connected to the press crown 72 and supplied with actuating liquid by the twin delivery pump 1, the two deliveries 66, 67 being connected to the respective units 68, 69 and independently controlled through connections 27, 65. A solenoid-actuated valve 80 determines the direction of movement of the crown 72 by controlling reversing valves 84, 91 in the respective delivery circuits, check valves 88, 95 acting to hold crown 72 in position if the pump 1 stops. Pump 77 supplies control liquid pressure for adjusting the pump deliveries. Valves 130, 133 are actuated towards the end of the downward stroke of crown 72 to connect control pressure to set pump 1 to zero delivery. Lack of synchronism between units 68, 69 is detected by valve 74 actuated by a roller 106 on crown 72 moving a lever pivoted on a stationary housing, valve 74 acting to reduce the pump delivery to the advanced cylinder. Valves 76 respond to excessive pump delivery pressures to reduce the delivery on the affected delivery side of the pump. Pump 77 has a pressure relief valve 81. In an alternative system, Fig. 9 (not shown), control liquid supply pump 77 communicates with the main pump control connections 27, 65 via throttles (140, 142), and the valves responsive to excess delivery pressure, lack of synchronism and end of stroke of crown 72 are normally open to vent connections 27, 65, and when operated are closed so that control pressure is applied to connections 27, 65.