Double jib tower crane - has jibs on two vertically spaced slewing platforms operating independently

摘要

The double-jib tower crane has a main supporting structure on which there slews a first platform (30) forming the mounting for a first jib (42). There is also a second platform (50) on the structure, on which a second jib (62) is mounted. The two jibs and platforms operate entirely independently of each other. The main structure can be stationary and on a fixed base (12), so as to form a rigid non-slewing support for the two platforms. The first of the latter can have bearings to absorb both the transverse forces and also the axial loads, thus allowing easy slewing. Each jib can have a travelling crab with hoist winch, also a tailweight mounted on an auxiliary jib extending rearwards and supported by tie ropes.