Tower crane with rigid jib - cam derrick jib up in order to clear adjacent crane

摘要

The crane has a rigid main jib along which a crab travels, and a tailweight jib, both being supported from the tower top by a tie rope. By derricking the tailweight jib down the main, one is derricked up to an angle at which it can be locked and where it extends above the tower top of a similar crane, when the two cranes are set up to work at the same height and are closer to each other than their main jib lengths. The tower top can be derricked together with main and tailweight jibs, until it comes up against a stop, and it can be locked in the working position - by means of a wedge - and also the derricked one.