GB910542A - Improvements in or relating to power operated hydraulic jacks - Google Patents

Abstract

910,542. Hydraulic jacks. CASTROL EQUIPMENT Ltd., and EARLY, K. C. Oct. 13, 1960, No. 35176/60. Class 78 (3). An hydraulic jack comprising a motor-driven pump for delivering fluid to the jack cylinder is characterized in that independent handoperated valves are provided for controlling the inlet and outlet of the jack cylinder, and the pump motor is of such a type that it can be stopped without harm by an overload when both valves are closed, whereby the jack may be locked hydraulically in any position regardless of failure of the pump motor. As shown, the piston 13 of a reciprocating compressed air motor 10, such as that described in Specification 718, 532 is connected to the pump piston 17. Downward movement of the piston 17 closes outlet ball valve 42 and sucks fluid from the reservoir 18 through pipe 38, ports 36, 35, ball valve 34 and pump inlet port 31 into the pump cylinder 16. If lever 52 is not operated to engage a plunger 50 to open a ball valve 43, upward movement of the piston 17 will cause the pressure in the pump cylinder to close ball valves 43 and 34 and the load on the compressed air motor will cause it to stop. When the valve 43 is opened by the lever 52, the fluid in the pump cylinder passes through valves 42, 43 and port 45 to the jack cylinder 22. When the lever 52 is released, pressure in the pump cylinder closes valve 43 and the pump stops again, the pressure in the jack cylinder 22 closing ball valves 59, 65 and preventing fluid from returning from the jack cylinder to the reservoir 18 through the jack cylinder outlet port 53 and passages 56, 61, 67. When hand lever 70 is operated to open ball valves 59, 65, fluid can flow back to the reservoir from the jack cylinder through a bore 39 and ram outlet port 53. The tubular piston-rod 24 is provided with an internally threaded nut portion 28 which adjustably supports a lifting pad 30. The jack cylinder is provided with a support flange 27 which may be secured to a plate 78, Fig. 4, mounted on legs 81 which are provided with wheels 85. Alternatively, the flange 27 may be secured to a wheeled platform 86 which runs on a carriage 89 provided with wheels 95 running on tracks 96 fixed to the sides of a pit 97.