GB664718A - Improvements in or relating to lifting devices - Google Patents

Abstract

664,718. Lazy tongs jacks. SMITH'S JACKING SYSTEMS, Ltd. May 25, 1950. [June 14, 1949; March 29, 1950] Nos. 15782/49 and 7847/50. Class 78 (iii). [Also in Group XXXI] A lazy tongs jack has its upper links 10, 11 and head 30 pivoted about one axis 14, and its lower links 12, 13 and foot 31 pivoted about another axis 15. The links 10, 11, 12, 13 consist of two similar laterally spaced sets of links joined by plates 10a, 11a, 12a, 13a and carrying blocks 18, 19 which respectively constitute a nut and a thurst bearing for the actuating screw 23. To ensure that axes 14, 15 remain in vertical alignment regardless of forces exerted on the jack through the screw, foot and head, a spring loaded telescopic strut 41 connected between the head and a link on the nut exerts a correcting force on the linkage when either extended or retracted. In a modification, Fig. 3, this strut is replaced by a pre-formed laminated leaf spring 60 secured to the load engaging number 30 by a rivet 65, and so arranged that when the axes 14, 15 are accidently misaligned during either the initial lifting stages or when the foot is being lowered onto the ground, interaction between the spring, one rod 61 or 62 secured to the links and one rod 66 or 67 secured to the head applies the correcting force. Load engaging crutches. Secured to the head 30, Fig. 1, is an inverted channel number 37 which has a slot in its upper side so that it forms a socket to support and locate the jack on a bar 33 secured to a vehicle chassis 50. The top of head 30 is bored at 36 to contain the heads of screws 35, which secure the bar 33 to the chassis, so further locating the jack on the bar. In a modification, Fig. 3, a similar slotted channel 37 is secured to head 30 but the jack is located by means of a hole in bar 30 which engages the head of rivet 65.