GB346684A - Improvements in or relating to lifting jacks - Google Patents

Abstract

346,684. Lifting-jacks. P 0 W E L L, A. D., The Limes. New Street, and BRADBURY & SONS., Ltd., J., New Street Works, both in Braintree, Essex. Nov. 5, 1929, No. 33590. [Class 78 (iii).] A hydraulic jack has means for supplying compressed air to the jack reservoir to cause the pressure fluid therein to raise the plunger to the load-engaging position and has a compressed air pump for supplying pressure fluid to the plunger for lifting the load. The casing A carries a tubular extension F fitted with a nipple F<1> and the operating spindle E of a valve C, the spindle being provided with a handle D. A compressed air supply pipe is attached to the nipple and the air passes to a recess C<6> in the valve. The valve is set so that air passes from the valve through ports C2, A<5> into the reservoir A<1> and forces the pressure fluid therein through a non-return valve I into the plunger cylinder A<8> to raise the plunger to the loadengaging position. By partially rotating the valve C air passes through a lateral port C<3> to the distributing valve L, Fig. 6, of an air-operated piston J having a plunger K in tandem therewith, the plunger causing pressure fluid to pass through a port K<2> to the plunger cylinder A<8> to raise the jack. By further rotating the valve C a cam C<1> on the valve depresses a valve pin H<1> and opens the release valve H so that pressure fluid returns into the reservoir and the jack is lowered.