708,920. Lifting jacks. METALLIFACTURE, Ltd., and PICKERELL, A. W. March 10, 1952 [Feb. 21, 1951], No. 4254/51. Class 78 (3) A lifting jack comprises a bipod support structure having downwardly diverging legs, a shank supported from the apex of the bipod, a lifting dog associated with the shank, means for causing vertical displacement of the lifting dog, and means to permit the shank and lifting dog to swing transversely to the plane of the bipod. As shown in Fig. 1 a bearing member 6 on a screw 7 is supported on a part spherical seat member 5, welded to the top of bipod legs 1, and the screw is rotatable by a handle 10 and ratchet gearing in the head 8. For rapid adjustment the ratchet gearing may be immobilized by movement of the pawl reversing arm 12, and the screw may be rotated by means of a knurled knob 13. According to a modification, this operating mechanism is located at the bottom end of screw 7. The crutch comprises a nut 14 and a pivoted bar 17 adapted to engage a socket on the load. In a modification (not shown) a ratchet bar, having a ball and socket connection with the member 5, has a crutch movable therealong by interaction of a pair of pawls which are pivoted to the crutch and are operated by a manually operable lever, to produce up or down crutch movement. In a further modification a pawl mechanism secured to the member 5 moves a ratchet bar, carrying the crutch, up and down.
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