Electrode positioning mechanism

摘要

The electrode positioning mechanism includes a reversible electric motor. The motor rotates a worm gear which drives a spur gear. The spur gear is connected to an internally threaded collar which is adapted to receive an externally threaded sleeve. The sleeve can move axially lengthwise with respect to the collar. The sleeve acts as a housing for the electrode. Means are provided to retain the sleeve within the collar such that mechanical movement is restricted. The restriction in mechanical movement causes the torque applied by the worm gear to increase. The worm gear is allowed to move axially along the length of the motor shaft. The worm gear is biased into a longitudinally central position by at least one spring. As torque increases, the worm gear is moved from its central position against the urging of the spring. The worm gear is also connected to a washer with a diameter greater than that of the worm gear. The washer moves with the worm gear and is in communication with a switching means that will reverse the direction of the motor when one washer is so moved.