GB600029A - Lifting jack - Google Patents

Abstract

600,029. Lifting-jacks. PAGE, H. E. May 15, 1945, No. 12205. Convention date, May 22, 1944. [Class 78 (iii)] A lifting-jack comprises a base on which is slidably mounted a housing in which is formed a hydraulic cylinder provided with a piston having its rod pivotally attached to a lever which is mounted on the base and connected to a load arm pivotally mounted at one end on the housing and at its other end carrying a load-engaging saddle, the lengths of the lever and load arm being such that when hydraulic pressure is admitted to the cylinder to operate the jack, the saddle moves in a path substantially perpendicular to the base. In the embodiment shown, the jack comprises pairs of lifting arms 25, 26 supporting a load-engaging saddle 45 and pivotally mounted by pins 27, 28 on a carriage 15 which is slidably mounted on a base 5 by flanges 14 engaging grooves 12 in the walls 6 of the base. A body 20, mounted within the carriage 15 on the pin 28, is formed with a cylinder 35 having a piston 40 and a piston-rod 39 which is connected to a lever 30 pivotally mounted at 31 on the base 5 and connected to the lifting arms 26 at 32. The upper cylinder 35 forms a reservoir for fluid which is pumped into a chamber 42 formed between the piston 39 and the lower end of the cylinder via passageways 61, 60 and 75. The pump comprises a cylinder 50 connected to the reservoir by a channel 70, and a piston 51 which is reciprocated by a handoperated lever 55, a rack-portion 52 on the piston engaging a pinion 53 on one of the bifurcations 54 on the lever. A release valve 83 is moved off its seat to permit fluid to return from the chamber 42 to the reservoir by a threaded-actuating member 87 rotated through links 88 connected to a rotatable operating rod in the handle 56. The base 5 is supported by resilient arms 9 on the axle 8 of rollers 7, whereby when the jack is under load, the base rests on the ground and resumes its normal position when unloaded.