Crane crab with rope slack compensation - has rope anchor points and pulley mountings supported by hydraulic rams

摘要

The crab has suspended from it lifting tackle supported on three or more ropes or rope falls converging in a pyramid pattern, the rope winches being mechanically coupled so as to run in synchronism. The anchorage points for the rope ends or the mountings for the pulleys around which they are reeved are supported on hydraulic rams, which lift them clear of stops to take up any rope slack. The rams are supplied at a predetermined pressure from a hydraulic accumulator, so that the force they exert is greater than that caused by the rope weight, but less than the sum of the rope weights and that of the lifting tackle acting on the anchorage points or pulley mountings.