GB1375756A - - Google Patents

Abstract

1375756 Accurately positioning suspended loads CONRAD STORK BV 19 Jan 1972 [29 Jan 1971] 2555/72 Heading B8B As shown in Fig. 1 a container 9 to be accurately positioned is suspended on hoisting cables 5 from a trolley 2 on a bridge crane 1. The cables 5 pass from a hoisting drum 4 over sheaves 6 to attachment points 8 on the trolley 2. Positioning wires 11 pass from lifting frame 7 over sheaves 12 to a drum 10 driven by a constant couple to maintain the wires 11 continuously tensioned. Eccentric loading due to wind forces or off-centre centre of gravity cause different stresses to occur in the cables 5 and in the wires 11. These differences cause differential elongation of the various lengths of wire and cable. The different stresses in the cables 5 are sensed by measuring systems incorporated in the attachment points 8 and result in movement of these points to compensate for the differential elongation they cause. Differential stresses in the positioning wires 11 are sensed by measuring devices 15 which provide a signal to a control device 16, this acts to move rod 14 carrying pivoted rods 13 with sheaves 12 in such a direction as to compensate for the differential elongation caused by the stresses. The response of the measuring devices at 8 and 15 may be modified to allow for the varying distance of the load 9 from the trolley 2, rotation of the hoisting drum 4 and of the drum 10 may be used for this purpose. Fig. 3 shows an embodiment wherein separate positioning wires are not required: two cables 24 from each of four coupled drums 23 pass over respective sheaves 25 on trolley 22 and sheaves 28 on lifting frame 27 to attachment points 29 on the trolley 22 where differing loads causing differences in elongation in the various cables 24 are sensed by a load measuring box (30), Fig. 4 (not shown), and are compensated by a stepping motor (31) driving a mechanism to tilt a lever (33) carrying the box (30).