| 摘要 |
<P>PROBLEM TO BE SOLVED: To keep a bending angle of a second boom against a first boom proper, by using a single positioning cylinder. Ž<P>SOLUTION: The second boom 18 is provided with: a front-side cylinder fitting portion 21; and a rear-side cylinder fitting portion 22 interposing a connection part with the first boom 12. A rod-side end 31B of the positioning cylinder 31 is attached selectively to either of the front-side cylinder fitting portion 21 or the rear-side cylinder fitting portion 22. This allows the positioning cylinder 31 to certainly receive a maximum load either in case the maximum load acts on the second boom 18 in the direction of increasing a bending angle, or in case the maximum load acts in the direction of decreasing the bending angle. Hence the bending angle of the second boom 18 is constantly kept proper by using the single positioning cylinder 31, regardless of the work such as excavation, load lifting, or the like. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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