Patent GB-621759-A (GB)
Title: Improvements in and relating to hydraulic jacks
IPC: B66F5/04
Filed: 1946-08-30
Abstract: 621,759. Lifting-jacks. GILLETT, STEPHEN, & CO., Ltd., and CROUCHER, A. H. Aug. 30, 1946, No. 26193. [Class 78 (iii)] An hydraulic jack used in raising the axles of motor vehicles of the type in which an hydraulic cylinder is arranged length-wise upon a carriage and operates a lever having an abutment which is brought into position against the axle and is displaced about its fulcrum by the ram of the hydraulic cylinder to which liquid under pressure is supplied in the lifting operation by a hand lever which actuates the pump the handle also being used for manipulating the jack, the ram and pump being constructed as a unit that is detachable from the carriage. The two ends of the hydraulic unit 8 are formed, as shown in Fig. 1, with arcuate surfaces 38, 41 which engage correspondingly shaped surfaces 39, 42 formed on the end of a lever 10 pivoted on a pin 11 and on the mobile carriage 1. The surface 42 is formed in members engaging against transverse cross members 44 and 44a. By raising the lever 10 and releasing the pressure liquid the ram and cylinder may be removed from the carriage. The lever 10 carries an abutment member 12. A spring 13 connects between the carriage and the outer end of the lever 10 and a link 19 provides a linkage parallel with the lever 10. The hydraulic unit incorporates outer and inner sliding tubular members. A tubular member with a nut 51 is provided through which oil or the like can be introduced to the inner member. To prevent overloading the piston rod 21 has a bore with an admission port to the reservoir and with a spring seating against one end of an overload valve in which a tubular member contacts a ball to force it against a seating on a member having an axial passage to the face of the piston. On excessive pressure the ball is displaced and displaces the seating so that the piston is inoperative to force the liquid from the reservoir into the cylinder of the ram. At the outer end of the pump cylinder is a spring loaded ball valve which functions as a non-return valve. When pressure exceeds a predetermined limit the pump operates to return the liquid to the reservoir. The piston of the pump is formed with an axial passage communicating with a reservoir in which a ball valve is located which functions as a bleed valve associated with a needle valve so that the rate of flow of liquid from the cylinder may be controlled. The valve is actuated by a handle pivoted to the main handle 84. The piston rod 21 is connected by a link 22 and pin 23 with an extension from a boss 25 rotatably mounted on a spindle 26 and having a secondary handle 27 and main lever 28. The two levers 27 and 28 are used to operate the pump. The lever 27 is used to bring the crutch 12 into its initial position beneath the axle. The levers are arranged to be secured to bosses mounted on the spindle. When the two bosses are engaged by a pin the main lever is actuated, when they are separated by moving the pin into one of the holes 31 the lever 27 can be actuated and the lever 28 secured from movement. The pin is moved by a rod 32 passing through a guide 33.