Synchronous drive apparatus and methods

Abstract

A synchronous drive apparatus and method, wherein the apparatus comprises a plurality of rotors comprising at least a first and a second rotor. The first rotor has a plurality of teeth for engaging the engaging sections of an elongate drive structure, and the second rotor has a plurality of teeth for engaging the engaging section of the elongate drive structure. A rotary load assembly is coupled to the second rotor. The elongate drive structure engages about the first and second rotors. The first rotor is arranged to drive the elongate drive structure and the second rotor is arranged to be driven by the elongate drive structure. One of the rotors has a non-circular profile having at least two protruding portions alternating with receding portions. The rotary load assembly is such as to present a periodic fluctuating load torque when driven in rotation, in which the angular positions of the protruding and receding portions of the non-circular profile relative to the angular position of the second rotor, and the magnitude of the eccentricity of the non-circular profile, are such that the non-circular profile applies to the second rotor an opposing fluctuating corrective torque which reduces or substantially cancels the fluctuating load torque of the rotary load assembly.

1 . An improved rotor for use in a synchronous drive apparatus, said drive apparatus comprising 
 a continuous-loop elongate drive structure having a plurality of engaging sections;    a plurality of rotors comprising at least a first and a second rotor, the first rotor having a plurality of teeth for engaging the engaging sections of the elongate drive structure, and the second rotor having a plurality of teeth for engaging the engaging section of the elongate drive structure;    a rotary load assembly coupled to the second rotor; the rotary load assembly being such as to present a periodic fluctuating load torque when driven in rotation;    the elongate drive structure being engaged about the first and second rotors, the first rotor being arranged to drive the elongate drive structure and the second rotor being arranged to be driven by the elongate drive structure, and one of the rotors having a non-circular profile having at least two protruding portions alternating with receding portions;    wherein the improved non-circular profile rotor has at least two reference radii, each reference radius passing from the centre of the non-circular profile rotor and through the centre of a protruding portion of the non-circular profile,    the angular position of the non-circular profile being related to a reference direction, the reference direction being the direction of a vector that bisects an angle about which the elongate drive structure is wrapped about the rotor having the non-circular profile,    the angular position of a reference radius is within a range of 90° to 180° from the reference direction taken in the direction of rotation of the rotor on which the non-circular profile is formed.    
   
   
       2 . Apparatus according to  claim 1 , in which the angular position of the reference radius being within a range of 130° to 140° from the reference direction taken in the direction of rotation of the rotor on which the non-circular profile is formed.  
   
   
       3 . Apparatus according to  claim 1 , in which the angular position of the reference radius is substantially at 135° from the reference direction taken in the direction of rotation of the rotor on which the non-circular profile is formed.