| 摘要 |
PROBLEM TO BE SOLVED: To maintain a working floor of a working bench constantly in a horizontal condition even when a telescopic boom is deflected. SOLUTION: A leveling device 23 is provided with a leveling cylinder 17 which is provided between a working bench and a telescopic boom to move the working bench in the vertical direction, an angle sensor 25 to detect the angle with respect to the horizontal plane of a working floor of the working bench, a memory 27 to set the allowable angular range of the angle of inclination of the working floor with respect to the horizontal plane, and operation detector 31 to detect whether or not at least telescopic or derricking operation is effected, and a controller 33 to control the operation of the leveling cylinder 17 so that the angle of inclination of the working floor is within the allowable angular range when the detected angle of the working floor by an angle sensor 25 is judged to exceed the allowable angular range while detecting the telescopic operation, etc., of the telescopic boom by the operation detector 31.
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