| 摘要 |
A valve operator utilizes a disconnectable worm gear arrangement to drive a valve spindle. An hand crank may be used to disengage the power-driven worm gear arrangement and to manually drive the valve spindle, if necessary, by pivoting a bracket holding the end of the worm shaft. The worm gear is self-locking so that reaction forces from the valve cannot move the worm gear. A torque-sensing lever, responsive to axial movement of a highly torqued drive shaft, pivots against the force of a biasing spring to operate a microswitch to cut off electrical power to the drive motor for the valve operator should the torque exceed a predetermined amount. Additional protection against torque overload is provided by an adjustable mechanical clutch which operates in the event of control element failure or misadjustments. One or more microswitches, adjustable in position, are engaged by a traveler which moves along a lead screw driven by a gear arrangement coupled to the valve spindle to control operation of the actuator. The worm shaft is pivotable away from its normal axis of operation by means of a splined universal coupling. |
