| 摘要 |
A hydraulic actuator for a hydraulic servomotor 4 is disclosed. The hydraulic servomotor 4 has a first chamber 5 and a second chamber 6 associated therewith. The hydraulic actuator is connected to a fluid source 2 and a fluid drain 3 , and it comprises a valve assembly arranged between the fluid source 2 and the fluid drain 3 to control fluid pressures in the chambers 5, 6 . At least one auxiliary valve 11 is fluidly connected between the valve assembly and the fluid drain 3, said auxiliary valve(s) 11 being of a kind which is normally closed in a de-energized state. In the case of a power cut off the auxiliary valve(s) 11 will close, thereby preventing fluid flow from the valve assembly towards the fluid drain 3 . This causes a servomotor piston member 12 to be hydraulically locked in its instantaneous position, thereby locking the hydraulic servomotor 4 . The valve assembly may be designed without taking the locking function into consideration.
|
