Tower crane telescopic jib - has grab travelling on mobile section suspended below section fixed to tower

摘要

The telescopic jib for use with a tower crane has a mobile section(3) suspended below and sliding in relation to a fixed section (2), mounted on the tower(1), by means of one or more sets of rollers, so that in the retracted position its rear end is adjacent to the lower. The lifting crab(12) travels for the whole length of the mobile jib section, the movements of the two being so co-ordinated that the crab travels over the entire outreach range of the crane without leaving the mobile section. There can be a crab travel winch at the base of the tower, from which two ropes are reeved round pulleys at opposite ends of the jib sections to opposite sides of the crab.