Needle boom rotary tower crane - is constructed in different cross-sectional sizes for increasing height demand

摘要

The rotary tower crane has a tower constructed from uniformly sized sections which can be arranged to provide a tower of small or large cross section, as required. The tower sections can be aligned in a single, vertical column to provide a tower having a narrow cross section, or a number of sections can be joined horizontally to form sections of enlarged cross section, which are then vertically aligned to provide a tower having an enlarged cross section. Four rectangular framework sections are attached at their adjacent vertical edges to form a section of enlarged cross section, having a rectangular central opening for receiving the tower head of the crane, which opening is approximately equal in size to the cross section of the original smaller sections.