| 摘要 |
PROBLEM TO BE SOLVED: To more speedily, safely, and adequately perform automatic storage of an expansion boom, by turning the expansion boom to a storage-time turning position when a present boom hoisting angle is larger than a turning tolerance angle, and by turning the expansion boom after raising it to the turning tolerance angle when the present boom hoisting angle is smaller than the turning tolerance angle. SOLUTION: A normal boom hoisting angle 'θx' corresponding to a present turning angle of an expansion boom is read out from a memory (S5). It is determined whether a present boom hoisting angle of the expansion boom is larger than the normal hoisting angle 'θx' selected in S5 (S6). When it is larger than the normal hoisting angle 'θx', the process directly proceeds to a turning control of S10. When it is smaller than the normal hoisting angle 'θx', raising of the expansion boom is performed so as to prevent interference between the expansion boom and a control box in the case where the expansion boom is turned (S7). At the time when the boom hoisting angle becomes larger than the normal hoisting angle 'θx', the raising of the expansion boom is stopped (S8, S9), and the process proceeds to S10.
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