| 摘要 |
PROBLEM TO BE SOLVED: To provide a low cost and highly reliable hydraulic drive device for a breaker having a device capable of preventing a pumping action. SOLUTION: This hydraulic drive device for the breaker comprises a cylinder 4 having fluid sealed therein, a piston 5 slidably disposed in the cylinder, a control valve and a circuit opening pilot valve 37 and a circuit closing pilot valve 39 operated so as to open or close the circuits of the cylinder and the piston. In addition, it comprises a check valve 41 and an anti-pumping piston 42 operated so as to close the check valve 41. When the circuit closing pilot valve 39 is open, an abnormality can be detected by oil leakage from a restriction 48. When a circuit open instruction is given with the circuit closing pilot valve open, the anti-pumping piston 42 closes the check valve 41 so that the pumping action is not performed after the circuit opening operation is performed.
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