| 摘要 |
An actuator for actuating valves and the like which comprises a pair of opposed cylinders, 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 center of the assembly which corresponds to a closed valve position. To open the valve, a fluid, such as air, is introduced between the pistons, so as to move them away from their rest (valve closed) positions. A handwheel is provided to manually open the valve by moving the pistons from their rest positions. A solenoid controlled pneumatic valve may be used to control the supply of air to the actuator. Either a failure in air pressure or an electrical failure will result in the pistons being urged to the rest positions and also result in closing the connected valve, i.e., the failure mode. |
