GB182323A - Improved construction of lifting jack - Google Patents

Abstract

182,323. Page, R. July 4, 1921. Jacks.-Relates to jacks of the kind described in Specification 11685/15. A rocking frame 5 which receives the handle 6 is pivotally mounted on the standard 2 and carries pawls 8, 9 normally engaging circular teeth 12 on the lifting pillar 13. Arms 19, 20 having curved edges a, b are pivoted to the standard 2 at their upper ends and normally kept apart by spring pins 26. A link 22 connects the arm 20 to the upper end of a rocking lever 21 pivoted to the other arm. A chain 27 attached to the other end of the lever 21 is passed through a hole 28 in the side 4 of the frame 5 and secured to a short tube 29, which is capable of limited rotation and has lugs 34 engaged by recesses on the end of the handle 6. Springs 17, 18 secured to the standard bear against pins 15, 16 on the pawls which are also acted on by the curved surfaces a, b. With the parts in the position shown, the pillar 13 can be removed as the pawls cannot be engaged with the teeth 12. If the handle is rotated, the chain n is wrapped round the tube 29 and the arms 19, 20 are pulled together, thus freeing the pins 15, 16 and causing the pawls to be forced into engagement with the pillar. If the handle is then rocked the pillar is raised. To lower the load the handle is first rotated to free the chain and then lowered after being slightly raised. The first action causes the arms 19, 20 to take up a position in which the surfaces a, b can act on the pins 15, 16, but the weight of the load maintains the engagement of the pawls and pillar. The second action disengages, raises and re-engages each pawl alternately.