Abstract: The present invention relates to an extended tooth contact harmonic drive gearing apparatus for transmitting rotary motion from an input drive to an output drive through mating contact between the gear teeth of a flexspline and a rigid circular spline, the flexspline being rotated into non-circular shape by a wave generator. The profile of the flexspline teeth are generated to cause the teeth of the flexspline to contact more than one tooth of the circular spline by forming a face profile on the flexspline teeth in accordance with a predetermined equation while the flank tooth profile of the circular spline is formed of a known arc segment, such as, a circle, ellipse or parabola.

Abstract: The present invention comprises an extended tooth contact harmonic drive gearing apparatus for transmitting rotary motion from an input drive to an output drive through mating contact between a flexspline and a rigid circular spline, the flexspline being swept into a non-circular shape by a wave generator. The wave generator causes the teeth of the flexspline to precess from a normal to an inclined orientation and back to a normal orientation again. The teeth on both the flexspline and the circular spline have a profile which accomodates that tooth inclination, and thus avoids interference therebetween.