GB1511428A - Heave compensating cranes - Google Patents

Abstract

1511428 Heave compensating crane BRITISH COLUMBIA RESEARCH COUNCIL 21 July 1976 30373/76 Heading B8E A crane 10 mounted on the deck 11 of a ship 12 has jacks 26, 27 to compensate for the movement caused to a pulley 70 at the end of its boom 22 by the heaving of the ship so that a load suspended at the end 76 of its cable 75 can be kept stationary. An accelerometer at the end of the boom remote from its pivot to a base 18 on pins 48, 49 detects a tendency to upwards or downwards movement and by a passive control which includes a gas bladder accumulator directs fluid to or from the jacks 26, 27 to cause compensation for any movement to the end of the boom. An active control which can pump fluid to or from the jacks may be provided in parallel to the passive control and is also controlled by the accelerometer. The cable 75 is operated by upper and lower traction drums 81, 82 synchronously driven and interconnected by successive loops 84 before passing to a take-up drum 88. The two drum arrangement allows relief of the compressive loads in the winch by the upward load exerted by the boom as it tends to move. The boom 22 may be telescopic, Figs. 1, 6 its outer end 36 having a rack 104 in engagement with a gear 105 mounted on the shaft 93 of the drum 81 to which it can be clutched to move the end section 39 while correspondingly paying out or taking in the cable 75. Alternatively, the pulley 70a, Fig. 8, may be mounted on a carriage 115, movable by a screw and nut mechanism 121, 120 along a non-extensible boom 22a.