To enhance the safety of work after releasing an interlock function while keeping satisfactory workability to continue operation of a boom even when several of jacks separate from the ground surface during work.
A controller 60 allows operation of the boom 30 only when detecting that all the jacks 50 are in a ground contact condition by a jack ground contact detector 83 while a storage condition of the boom 30 is detected by a boom storage detector 84 and allows operation of the boom 30 only when detecting that at least one of four jacks 50 is in a ground contact condition by a jack ground contact detector 83 while the boom 30 operates from a storage condition and a non-storage condition of the boom 30 is detected by the boom storage detector 84.
MIZUGUCHI HIROAKI
YAGISAWA YUICHI
| JP2003128393A | 2003-05-08 |
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