GB423141A - Improvements in or relating to hydraulic lifting apparatus - Google Patents

Abstract

423,141. Pump valves ; relief devices. ALLEN & HANBURY'S, Ltd., and GAMBLE, G. T., 37, Lombard Street, London. March 29, 1934, No. 9911. [Class 102 (i)] [See also Groups XXX and XXIX] In hydraulic lifting-apparatus of the kind in which a hand or foot operated pump withdraws fluid from a reservoir through a non-return valve and forces it through a second non-return valve into a ram cylinder, a valve unit is provided which dispenses with the employment of a separate release valve for permitting fluid to escape from the ram cylinder. The unit comprises a plug 13 screwed into the bottom of the ram cylinder 1 and furnished with two ball &c., valves 11, 12, of different diameters, in line. The balls have seatings 13<b>, 13c, and are preferably pressed down by springs 14, 15, the spring 14 abutting against a perforated cap 13f. A groove 13e runs round the plug 13, and is connected to the valve bore 13<a> by inclined passages 13<d> which preferably communicate with the bore near the lower ball 11 to minimize noise in operation. The groove 13<e> is connected to the pump cylinder 4 by a port 2b. The balls 11, 12 are adapted to be raised simultaneously to release fluid from the cylinder 1 and allow it to flow back into a reservoir 17 by a projection 16b mounted on an extension 16<a> of an arm 16 which can be raised and lowered by rotating a cam 18 by a handle 19<a>. The cam spindle 19 is screwed to allow further turning of the handle 19<a> to press a brake block 20 against the ram 7 and hold it in any required position. The pump operated handle is pivoted at 2<a> and engages a yoke 9<b> at the upper end of the spring-pressed pump piston rod 9. A port 1<a> determines the upper limit of the ram travel.