Rotating tower crane whose height is extended step by step - has guiding and enclosing sections for supporting tower sections

摘要

The tower height can be extended or reduced without using additional cranes. The tower has at the top a turntable ring about which rotates the overhanging arm and its counterweight. The tower sections consist of two detachable extension lengths, and the tower height is extended by making use of connecting overlapping guide members. The lower tower section is extended first and after that the adjacent tower section. In order to extend the tower by one extension length the connection, between the upper section of the lower tower section and between the extension piece, is released and then the lower guide member is pushed upwards by the length of one extension length by means of a hydraulic jacking system.