| 摘要 |
PROBLEM TO BE SOLVED: To overcome disadvantages of the prior art and to safely fold or extend a tower crane by replacing a manual operation which brings about risk with an automatic sequence for eliminating it. SOLUTION: In a tower crane provided with a folding mast and a folding jib, an expansion or folding operation is driven by an actuator like a pump. The device of this invention is driven from a folding transportation position to an expansion work position, or it can operate automatically reversely. If expansion or a folding procedure is selected by a switch and a command manipulator, a plurality of pumps are sequentially actuated by a preset automatic sequence corresponding to the selected procedure. Execution of the sequence is controlled by a set of sensors detecting a mast and/or jib element of a crane arrived at the intermediate position and the final position. COPYRIGHT: (C)2003,JPO
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