| 摘要 |
PROBLEM TO BE SOLVED: To provide a boom device having good operability and, if necessary, making it possible to easily manually move a boom. SOLUTION: This boom device is provided with a manual boom drive- controlling device 36 which can release the hydraulic oil of a boom-driving hydraulic actuator 13 to manually drive the boom. The boom is usually driven by the power of the hydraulic actuator 13. If necessary, the device 36 for controlling the manual boom drive is operated to release the hydraulic oil of the hydraulic actuator 13, thus making it manually drive the boom.
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