| 摘要 |
<p>A fail-safe-open actuator for actuating valves and the like which comprises a pair of opposed cylinders joined to define piston chambers, the axes of which are generally perpendicular to a valve stem. Pistons in the cylinders are connected to the valve stem by toggle links, the pistons being resiliently urged toward the ends of the assembly which corresponds to an open-valve position. To close the valve, a pressurized fluid, such as air, is introduced into the piston chambers and to the pistons at sufficient pressure to counter the resilient means so as to move the pistons away from their rest, valve-open positions, and thus move the valve stem perpendicularly to the axis of the piston chamber. A handwheel is provided to manually close the valve by moving the pistons from their rest positions. A solenoid controlled pneumatic valve may be used to control the supply of pressurized fluid, such as air, to the actuator. Either a failure in fluid pressure or an electrical failure will result in the pistons being urged to the rest positions and also result in opening the connected valve, i.e., the failure mode.</p> |
