| 摘要 |
<p>A hydraulic valve actuator includes at least one piston mounted for reciprocating movement in a cylinder for bidirectionally rotating a valve shaft mounted in the housing. A resilient spring member is held in compression between one side of the piston and an end wall of the cylinder for yieldably urging the piston to rotate the shaft in one direction, in the absence of a sufficient opposing hydraulic pressure. A hydraulic pump driven by an electric motor selectively drives the piston against the force of the spring member for rotating the valve shaft in the opposite direction. An electric solenoid operated valve is connected with the cylinder at either side of the piston, to provide a selectively openable path for hydraulic fluid, by-passing the pump to relieve the pressure applied thereby. Selectively operable mechanical or electronic switches are provided for energizing and deenergizing the solenoid valve and the hydraulic pump to cause the piston to move in the corresponding direction, to open or close the valve as desired. An electro-mechanical control system is connected with the valve shaft and the switches to actuate and maintain the valve in its fully opened, fully closed, or some desired intermediate condition. In one embodiment the electro-mechanical system includes a gear and cam arrangement driven by the valve shaft for actuating mechanical switches, and in another embodiment the system includes a potentiometer driven by the valve shaft and an electronic control system responsive thereto for actuating electronic switches.</p> |
