Patent ID: 8042507

Claim:
A synchronous drive apparatus including a rotary component, the synchronous drive apparatus comprising: a plurality of rotors comprising a first rotor and a second rotor, each of the plurality of rotors having a rotational axis and a plurality of teeth arranged about a perimeter; a continuous loop drive structure having a plurality of engaging sections that are engaged with the teeth of the rotors to transmit rotary power through the continuous loop drive structure to drive the first rotor; a rotary load assembly driven by the first rotor, the rotary load assembly generating a first periodic fluctuating torque when driven by the first rotor; wherein at least one of the plurality of rotors is configured such that each of its plurality of teeth have a crown that is disposed between a pair of valleys, each of the valleys has a profile and each of the profiles is identical, and a distance between a midpoint of each of the crowns and the rotational axis of the at least one of the rotors varies around its perimeter to produce a non-circular rotor profile that is configured to produce a second periodic fluctuating torque that is out of phase with the first periodic fluctuating torque to reduce variation in a newt torque applied to the first rotor by the continuous loop drive structure and the rotary load assembly.