GB1461021A - Hydraulic lifting devices - Google Patents

Abstract

1461021 Fluid-pressure actuators; reciprocating pumps JUNGHEINRICH UNTERNEHMENSVERWALTUNG KG 9 June 1975 [27 June 1974] 24688/75 Headings F1A and F1D In a pallet truck, reciprocation of a handle 20, Fig. 1, operates pumps 5, 6, Fig. 2, of different capacity, which can be controlled to deliver fluid to a lift cylinder 1 either together or individually, any fluid which does not pass to the lift cylinder being returned to a reservoir. As described, the pumps are controlled by a manually shifted rod 53 with detents 55 engaged by a spring 56. This moves a slide 37, Fig. 4, with grooves 49, 50, 51 which accommodate tappets 45, 46. When the latter are raised by bands between the grooves, ball-valves 33, 41 are opened to connect the output of either one or both pumps 5, 6, to the reservoir. In a second embodiment, Fig. 5, the slide 37 is moved against a return spring 62 by the pressure in the lifting cylinder 2. Thus, the output of pressurized fluid is varied in steps in dependence on the load being lifted. The slide 37 may be replaced by a rotatable member with cams.