GB545585A - Lifting jacks - Google Patents

Abstract

545,585. Lifting jacks &c. JACKSON, A. Jan. 22, 1941, No. 852. [Class 78 (iii)] A lifting-jack or device comprises a base frame 1 having a raised rear portion 16, Figs. 1 and 3, a lifting member 9 having its rear end pivoted at 3 to the frame, the front end of the lifting member being adapted to raise a load, a link 14 extending between the raised portion 16 of the frame and the lifting member, one end of the link being pivoted and the other end having a sliding connection, and means to move the sliding connection so as to raise the lifting member. The link 14 may be pivoted to the member 9 and be slidably connected to the part 16 of the frame, but in the construction shown in Figs. 1 and 3 the link is pivoted at 15 to the part 16 and carries a cross-bar 12 at its front end resting on the upper surface of the arm 9. Hooks 13 on the cross-bar 12 engage under the top flanges of the arm 9 and keep the bar on the arm. The bar 12 is slid along the arm 9 to raise the latter by means of a pneumatic or other cylinder 20 having extensions 21 pivoted at 22 to the arm 9 and containing a piston 19 with a piston rod 18 fixed to a sleeve 17 on the bar 12. The piston rod is provided with a slot 23 for the pivot shaft 22. In order to prevent the arm 9 from falling down if air leaks out of the cylinder 20, a catch 26, 27 pivoted on the shaft 22 is adapted to engage notches 28 in the piston-rod. The catch is spring-loaded so as to engage the notches 28 in succession, as the piston-rod moves outwards, and may be held out of locking engagement by means of a spring catch 32. Modifications are described in which (1) the fluid-pressure cylinder is pivoted to the raised part 16 of the frame instead of to the arm 9 and its piston-rod is connected either to the end 12 of the link 14 or to an intermediate part of the link ; (2) the link is pivoted at 12 to the arm 9 and its rear end is guided vertically by a slot in the raised part 16 of the frame, this rear end being raised and lowered by a vertical cylinder fixed to the frame ; (3) an electric motor may be used instead of a fluid-pressure cylinder, this motor driving a screw shaft carrying a nut mounted on the end of the link 14 ; and (4) a pneumatic-hydraulic cylinder 76, Fig. 18, may be used carrying a closed hollow piston 77 having a cup leather 78 forming an hydraulic seal in the cylinder. A pipe 79 connects the closed end of the cylinder to the piston interior. Liquid fills the rear end of the cylinder and also the lower part of the piston. Compressed air is admitted by a pipe 81 to the interior of the piston and forces liquid into the cylinder so as to move the piston outwards.