| 摘要 |
PURPOSE:To provide a small and manipulatable hydraulic actuation device which may forcibly carry out the return movement of a piston rod by hydraulic pressure, and which may automatically and rapidly carry out this return movement. CONSTITUTION:A piston extending oil passage 42 and a piston retracting oil passage 43 communicated with a pump means 15 are formed in a body casing 13, and a supply passage for high hydraulic pressure fed from the pump means 15 is changed over into the piston retracting passage 43 from the piston extending passage 42 in response to position detection signals from position detecting means 59a, 59b for a piston rod 23. |
