GB935232A - Improvements in lifting tongs - Google Patents

Abstract

935,232. Lifting tongs. HEPPENSTALL CO. June 23, 1961 [July 21, 1960], No. 22807/61. Class 78 (4). The jaws 11, 12 of lifting tongs are movable together in two stages, namely an initial load - engaging movement effected by a rotary drive prior to lifting and a further movement effective to grip the load firmly during actual lifting. The illustrated embodiment has one jaw 11 rigidly attached to a horizontal base member 14 and the other jaw 12 carried by a bracket 20 which is slidable along the base member. To engage the jaws with a load such as the coil 13, the electric motor 43 is driven to rotate the screw-threaded rod 30 in such sense that it tends to move to the left. This movement to the left is arrested by the abutment of end collar 36 on the rod with the fixed surface 38 and thereafter a nut 27 on the rod is pulled to the right and takes the bracket 20 with it to move jaw 12 towards the load. When contact is made, a torque-limiting device in the motor drive prevents excessive pressure on the coil before lifting. When crane hook 50 is raised to lift the load, lever 76 swings clockwise about its pivot 77, which it subsequently raises to move the lower end 58 of lever 62 to the right and at the same time cause lever 82 to turn and lift a T-headed bolt 84 from a retaining recess 86, the bolt and recess forming a latch which, except during lifting, maintains the lever mechanism in the position shown. The right-ward movement of lever end 58 engages clutch members 53, 55 to prevent further rotation of rod 30 in either direction and at the same time move it axially so that jaw 12 moves further in to grip the coil. When the coil is subsequently deposited, the clutch automatically releases and the latch re-engages and further rotation of the motor this time in the opposite sense, returns the apparatus to its original condition. In one modified form the motor is replaced by a hand wheel and the toothed clutch by a conical friction clutch. In another motor-driven form (Fig. 4, not shown), the lever 62 is duplicated to form two elements of a " lazy-tongs " type linkage, the means for engaging the clutch, releasing the latch and applying the load-lifting gripping pressure all being carried by the elements of the linkage. Specification 897,639 is referred to.