| 摘要 |
A valve actuator is provided for use in conjunction with a valve having an actuating member movable between a first position in which the valve is closed and a second position in which the valve is open. The valve actuator comprises a reversible motor having its output mechanically connected to the actuating member. The actuation of the motor is controlled by a circuit having a microprocessor. An optical sensor on the valve actuating member provides an input signal to the microprocessor indicative of the position of the valve and the position of the valve corresponding to both the open and closed position are stored in a memory accessible to the microprocessor. When the actuating member attains a desired position, the microprocessor is programmed to generate a stop signal which deactivates the motor. Strain gages connected to either the actuating member or the motor output shaft generate an output signal to deactivate the motor when the torque exceeds a predetermined amount while an override circuit permits an increased torque to be applied to the actuating member following the initial activation of the motor in order to break the valve free.
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