Image Number 5 for United States Patent #5448117.
A stepper motor includes a stator with magnetic poles extending radially outward from a central core to form segments of an outer stator surface, an armature ring fitting loosely over the stator, and a rotor with a drive plate rotationally driven by rollers extending from the armature ring into apertures in the drive plate. Current is supplied, according to a sequence, through coils surrounding each magnetic pole, so that the armature ring, being sequentially attracted to adjacent magnetic poles, moves around the stator with a modified orbital motion including an orbital motion, in which the ring is translated around a circular path, and a rotational motion. The stepper motor may also include a stationary cam plate with a number of peripheral notches, into which the rollers are moved individually by the orbital motion.
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