Improvements in or relating to hydraulic lifting mechanisms for movable apparatuses actuated manually by an operating handle, such as hand pallet trucks, lifting trucks and the like

摘要

988,600. Pallet trucks. A. RATEAU. June 4, 1962 [June 12, 1961], No. 21405/62. Heading B8H. In Fig. 1, an hydraulic unit for raising the platform 30 of a hand pallet truck is operated by a pivoted lever 7 which, after operation, is returned to a vertical position by a spring 20 of a pump 1. The piston 2 of the pump is connected to the lever 7 by a rod 6 and the pump body is mounted beneath a ram 4 for raising the platform 30. A bag 11 contains a reserve of oil for the unit. In Fig. 2, a ball valve 21 is provided in the body of the ram 4 but the ball may be unseated by the piston 5 of the ram engaging a rod 22. A pressure limiting device 24 is provided. With the piston 5 of the ram 4 in its lower position, upon moving the pump piston 2 inwardly, oil flows past a valve 14 to move the piston 5 upwards. When this piston engages the lower end of the rod 22, i.e. after a spring 23 has been sufficiently compressed, the valve 21 is opened and pressure is released through pipe 16. Thus, after the platform 30 has been raised, an operator may move the lever 7, which is used also for steering the truck, without having to overcome resistance due to pumping. The operator may actuate a valve 29 to allow the piston 5 and platform 30 to be lowered.