| 摘要 |
PROBLEM TO BE SOLVED: To solve such problems that, since a level control device for a conventional prevention boom is folded into the prevention working unit hung on the rear part of the machine body, it becomes difficult to confirm the operation of the level control device by looking back as the speeding-up traveling motion progresses, and the safety ensuring during traveling becomes impossible because of the danger of touching a side boom with a driver or some thin, or the like, in the case where the level control is actuated during traveling under folding the both ends of the control boom. SOLUTION: Following means are employed for solving the problems: a central prevention boom 2 is fixed in a freely swingable manner in the right and left direction on the front part of a moving vehicle 1; the base ends of right and left side prevention boom 4, 5 are fixed respectively on the right and left end of the central prevention boom 2 centering the rotational shafts 6, 6 in a freely rotatable manner; and when the whole body of the boom is spread in a straight line, the level control of the boom is automatically performed, and when the side booms are folded and the width of the boom is narrowed, the command for level control is not issued, or the folded boom is controlled in a parallel state to the machine body.
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