GB586092A - Hydraulic lifting jack - Google Patents

Abstract

586,092. Lifting-jacks. PAGE, H. E. Nov. 21, 1944, No. 23140. [Class 78 (iii)] In a hydraulic jack the lever which actuates the pump is connected directly to the loadengaging member and raises it rapidly into contact with the load without the application of fluid pressure. Fig. 1 shows a jack body 5 provided with two cylinders 6 and 7 surrounded by a reservoir 8, vented to atmosphere by a plug 9. A work lifting piston 10 is reciprocally mounted in the cylinder 6 and a pumping piston 12 in cylinder 7. A lever 15 has one end bifurcated and is pivotally mounted to the piston 10 by a pin 16 and is pivoted to the piston 12 at 12a by a link 18. A valve member 25 comprises a body 26 having grooves for sealing rings 27. A poppet valve 30 with stems 31, 32 is mounted in a bore 33 threaded into the valve body 26, being held seated by a spring 45. The stem is of square cross section to permit fluid flow. A second poppet valve 37, with stem 38 is mounted in the valve body 26, being held seated by a spring 40. The cylinder is connected to the reservoir by passageways 50-52, controlled by the poppet 30. The cylinders 6, 7 are connected by passageways 50, 52, 55, 54, 53, controlled by poppet 37. Cylinder 6 communicates with the reservoir by passageways 53, 57 controlled by a check valve 60. In operation the piston 12 is first raised by lever 15 causing cylinder 7 to fill with fluid from the reservoir via poppet 30. Downward movement of the lever 15. raises the work piston 10 causing cylinder 6 to fill with fluid via the check valve 60. Thereafter the piston 10 is raised by the pumping of piston 12. The jack is lowered by turning the cam 70 by the handle 72, Fig. 2, the cam contacting stem 31 to unseat poppet 30, thereby releasing the pressure in cylinder 7. Further rotation of the cam causes the stem 37 to contact the stem 38 unseating poppet 37 which releases the pressure in cylinder 6. In one modification there are two pumping pistons and two work lifting pistons, and in another both the pumping and work lifting pistons are telescopic to allow a high lift to be achieved and in yet another modification the lever is arranged near the base of the pump.