| 摘要 |
PROBLEM TO BE SOLVED: To make it impossible to operate a power shovel toward dangerous sides such as an arm and a boom when actual load reaches allowable hanging load in a load hanging work safety device of the power shovel. SOLUTION: Shut-off circuits 26 and 29 making it impossible to operate a power shovel toward rising sides of arm and boom hydraulic control valves 16 and 17 when actual load reaches allowable hanging load are provided to the power shovel capable of executing load hanging work equipped with a safety device setting the allowable hanging load and actual load in a relation between anglesθ1 andθ2 of the boom and arm. The boom rising is stopped when the actual load reaches pressure adding specific incremental value to hydraulic fluid pressure in the case it reaches the allowable hanging load. When the actual load reaches the allowable hanging load, the arm rising is locked, as for the boom rising, since a lock is operated with pressure increased by pressure equivalent to packing resistance of a boom cylinder, the boom is raised after the safety device is operated, and the hanging load is approached to the body and can be unloaded.
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