ES348631A1 - Improved Hydraulic Lifting Jack - Google Patents

Abstract

An hydraulic lifting jack comprises a base 2 with a hollow cover 1, a mounting plate 4 fixed on the base 2 with two spaced bores 4A, 4B respectively mounting an upstanding cylinder 5 and a housing 6. A ram 5A is movably mounted in the cylinder 5 and carries an extension screw 5C in a threaded bore 5B. An operating plunger 6A is slidably mounted in the housing 6. Space 8E below the ram 5A is in communication with the interior of the housing 6 through passage 4C in the plate 4, slots 9A, 9B respectively in the cylinder 5 and housing 6 being provided for this purpose. The cover 1 forms a reservoir for hydraulic fluid, the normal level being indicated by the dot-dash line in Fig. 5. Fluid is drawn from the reservoir through a suction valve body 13A when the plunger 6A is raised by raising a handle 19 inserted into a handle socket 16 pivoted on a pin 16B in a bracket 17 pivoted on a pin 16D on the cover 1. The handle 19 has a cut-out flat 22 normally arranged over the top of the plunger 6A so that the latter clears a spring-loaded ball 11 at the bottom of its normal stroke. On reciprocation of the plunger 6A fluid is forced past the ball 11 under the ram 5A to raise the latter. To release pressure and lower the jack the handle 19 in the down position shown is rotated axially when the full diameter of the handle 19 engages the top of the plunger 6A. This produces over-riding of the non-return action of the ball 11 allowing fluid to flow from under the ram 5A via slot 9A, passage 4C, slot 9B past the ball 11 and through a slot 14 in the plunger 6A and a part 12A back into the reservoir.