| 摘要 |
PROBLEM TO BE SOLVED: To set the entire length of a boom to a maximum length by securing brackets to the central point in the longitudinal direction of a body of a rear boom and to the front of a body of a front boom respectively, and mounting a hydraulic cylinder for bending the boom between both of the booms. SOLUTION: Brackets 26, 27 are welded to nearly the central point in the longitudinal direction of a body of a rear boom 16 and to the front of a body of a front boom 17 respectively, and a hydraulic cylinder 21 for bending the booms is mounted between both the booms 26, 27. When the cylinder 21 is in a fully extended state, a boom 15 is in a straight state, in the side view, so that the entire length of the boom 15 can be set to a maximum length. And when the cylinder 21 is contracted to the minimum, a bent angleθbetween the boom 16 and the boom 17 is made approximately right angles and the length of the boom 15 can be decreased.
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