| 摘要 |
PROBLEM TO BE SOLVED: To provide a power shovel having a hook mounted on the tip of an arm for lifting a load, ensuring a higher safety in the load lifting work. SOLUTION: This power shovel is provided with a safety device for giving an alarm and stopping the upward movement of a jib when the actual load of a hook provided on the tip of an arm reaches an allowable lifting load. When the absolute angleθ3 of the arm calculated by the angleθ1 of a boom and the angleθ2 of the arm exceeds a set angle, control hydraulic circuits 26, 29 between a pressure control valve connected to the operation lever of a driver's seat and control valves 16, 17 operated by the secondary pressure of the pressure control valve are interrupted to stop the upward movement of the jib. In a power shovel capable of load lifting having a side-ditch digging boom for laterally movably supporting an arm 3, when the angleθ4 of an offset boom exceeds a set angle, an alarm is given or the operation in the direction of increasing the offset is stopped.
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