METHOD AND STRUCTURE FOR EXTENDING AND RETRACTING TELESCOPIC BOOM FOR CONSTRUCTION CRANE FOR TOWER-LIKE STRUCTURE

摘要

A structure and a method for extending and retracting a telescopic boom, for lifting up to a required height a crane used to construct a tower-like structure such as a high rise support or a tower. A main cylinder (18) is housed on the inner side of telescopically combined booms (11-17), and a piston rod (19) reciprocated by operation of the main cylinder (18) is mounted directing downward.  The front end of the piston rod (19) is connected to the boom (11) on the outer side, and the lower end of the main cylinder (18) is connected to the boom (12) directly adjacent and on the inner side of the boom (11).  When the main cylinder (18) is operated to advance the piston rod (19), the main cylinder (18) ascends, causing the boom (12) to extend relative to the boom (11).  Fixing the lower end section of the ascended boom (12) and the upper end section of the boom (11) to each other enables the boom (12) to be maintained extended relative to the boom (11).  The telescopic boom (10) is extended by repeating the above procedure.  Also, the main cylinder (18) ascends as the telescopic boom (10) is extended.