GB797839A - Improvements in and relating to load lowering and lifting - Google Patents

Abstract

797,839. Load-lifting devices with automatic control; grabs. BRAITHWAITE & CO. ENGINEERS, Ltd. June 26, 1956 [July 9, 1955], No. 19912/55. Class 78 (4). Equipment for load-lowering and lifting, comprising means for suspending the load, as for example a winch and cable, and wherein, on conclusion of lowering, a supplementary operation on the load is effected automatically under the influence of a controlling condition which thereupon arises, namely slackening of the means of suspension on being relieved of the load, is characterized by means for automatically requiring repetition at least once of the controlling condition before the supplementary operation actually takes place. As shown, the equipment is suspended from a cable attached to a slide 1, Fig. 1, having limited movement between stops 9, 10 relatively to a cage 4 carrying pivoted members 3 gravity-biased by lugs 6 which support the load 2 when teeth 12 are engaged by a crossbar 11 on the slide 1, as shown in the left-hand side of Fig. 1. When the cable slackens the cage is supported on the load by a flange 7 and the stop 9 engages the teeth 12, as shown in the right-hand side of Fig. 1. Each time the cable becomes taut after slackening, the members 3 take up the successive positions b, c, d, Fig. 1, the load being released only when position d is reached. In an embodiment for closing the jaws of a grab, the ends 28, Figs. 4a, 4b, of catches 29 act as bearing blocks between a tubular fair lead 21 fixed between side plates 20 on the grab body, and a button 27 on the end of a rod 25 carried by the supporting cable, the blocks being gradually withdrawn under the control of an escapement device, finally allowing the button 27 to pass through the fair lead, taking with it the cable extension 26 for closing the grab jaws. The catches 29 are pivoted on shafts 30 engaging slots 31 in the plates 20 and slots 38 in T-shaped plates 35 guided for vertical movement and carrying racks engaging pinions 39, Fig. 4b, mounted on brackets fixed to the plates 20. As the plates 35 descend, the ends 28 of the catches move outwards and downwards after the heavier ends 32 meet stops 24. The pinions 39 are rotated one tooth at a time, on each slackening and re-tightening of the cable, by a bobbin 41 slidable between a shoulder 42 and a top flange 43 on the rod 25, and urged upwards if necessary by a'spring (not shown). The pinions have cylindrical recesses 46, 47 to allow the passage of the flange 45 and button 27. In a modification, Fig. 7, the fair lead 21b is movable vertically and carries the racks on its inner surface, the catches 29 being in the form of bell-cranks having fixed pivots, their horizontal arms being engaged by the fair lead at the lower end of its travel, and extensions on their vertical arms releasing the button 27. In this embodiment the bobbin 41 is fixed to the shaft 25.