| 摘要 |
PROBLEM TO BE SOLVED: To protect a crusher, a hydraulic shovel or the like from breaking by turning a body frame by a hydraulic motor using pressure oil produced in the case of the generation of excessive torsion in the crusher used being fitted to the tip of an arm of the hydraulic shovel or the like. SOLUTION: In crushing work, a crushing arm is first placed orthogonally to a crushed object by hydraulic shovel operation, and its tip is thrusted into a crushed part. A changeover control valve 86 is then operated to open/close the crushing arm by a hydraulic cylinder 36 to crush the object part. At this time, if torsional action is applied to a crusher, a hydraulic motor 51 receives torque through a pinion 44 engaged with a rack 43 of a spring bearing 4, and a pilot selector valve 55 is shifted by produced pressure oil. When the pressure oil becomes excessive, a relief valve 56 is opened, and the hydraulic motor 51 is rotated by the operating oil flowing in a by-pass passage 52, to turn the crusher, In the case of the operating oil being insufficient at this time, the operating oil is supplied from an oil sump 54.
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