| 摘要 |
<p>An actuator for fluid control valves with a reversible power module having a stationary inner member (50) and a coaxially aligned movable outer member (48) coupled to the valve flow control element and slidably movable on the inner member. A chamber (90) formed between respective ends of the members includes a preformed bladder (93). Pneumatic pressure applied to the bladder drives the movable member to actuate the valve in a first direction. A spring (112) returns the movable member in the second direction. The preformed bladder is formed with two pieces including an interconnecting perimeter portion (94). During bladder actuation the bladder perimeter portion is displaced from the bladder inner diameter to the bladder outer diameter with the bladder material in tension to thereby prolong bladder life.</p> |
