| 摘要 |
<p>The valve actuator (10) has a movable control element (12) which is typically connected to the valve to be opened/closed and a propulsion device (16) which may be a hydraulically operated piston (16) for moving the movable control element. A resilient element (22) which may be in the form of a spring arrangement has a stroke extending from a first relatively unloaded position to a second relatively loaded position and a transmission mechanism (18) is also provided, where the resilient element is loaded under the action of the propulsion device via the transmission mechanism and is configured to urge the moveable portion of the propulsion device towards the first position via the transmission mechanism when loaded. The transmission mechanism provides a gearing ratio reduction between the moveable portion of the propulsion device and the resilient element.</p> |
