| 摘要 |
An electric actuator for varying the position of a valve stem comprises an output shaft adapted to be coupled to the valve stem. The output shaft is selectively rotated, between limit positions defined by a pair of electrical limit switches cooperating with cams carried by the output shaft, through the agency of a motor module comprising one or more electric motors and an associated gear box having an output pinion in drive engagement with an output gear coupled to the output shaft. The output gear includes two sets of concentric teeth disposed in spaced relation to one another, and adapted to be engaged individually by the motor module pinion, for driving the output shaft at different torques and speeds in dependence upon which set of output gear teeth is engaged by the pinion. The motor module can be mounted in either of two different positions to cause its pinion to engage one or the other of the output gear teeth sets. The output pinion is preferably located at an eccentric position relative to the motor module so that pinion engagement can be shifted from one to the other of the gear teeth sets by a 180 DEG reversal in the motor module mounting position. |
