| 摘要 |
PURPOSE:To prevent a pump from seizing by providing a detecting means which detects that the pressure of the pump exceeds a specified value, thereby draining discharged working oil to a reservoir upon receiving of the output from the detecting means. CONSTITUTION:A hydraulic controller unit 7 which is connected to the oil chamber 6 of a cylinder unit 4, includes a hydraulic pump 8, the inlet side of which is communicated with a reservoir 11. On the other hand, a pressure switch 42 which outputs a signal when the discharge pressure of the hydraulic pump 8 is found to exceed a specified value, is provided in a main line 12 on the discharging side of the hydraulic pump 8. The output of the signal from the pressure switch 42 allows the controller unit to open an unloader valve 38 so as to drain working oil in the hydraulic pump 8 to the reservoir 11. This constitution can prevent the hydraulic pump 8 from seizing because of an over- load operation. |
