Ship yard crane crab travel mechanism - uses forces generated by load variations to move crab along jib

摘要

The mechanism moves the crap or a shipyard crane along the jib, without using any forces other than those generated by the variations in the loads lifted. There may be specially reeved ropes and pulleys moving the crab towards the jib head when under load, the crab (3) being pulled back towards the tower (10) by a counterweight (9) previously raised by the crab travelling outwards. There may be a drum with brake controlling the crab movement in both directions. The hoist rope (1) is reeved round the pulleys on crab and hoist block (4), and them round a further pulley (2) at the jib head to the anchor point, to effect the crab travel movement.