Abstract: With the research into the mechanism of changeable-structure and changeable degree of freedom, the novel conception of mechanism stransforming factor is proposed and its function is explored in the light of the seven kindes of mechanism transforming factors. Thus the rationale of the mechanism conformation change based on transforming factor control is developed. With the research of reduction-overrun- ning clutch, this rationale has proved to be theoretical guidelines for the creativity in designing mechanical devices.

Key words: Active gear transmission, Change restriction kinematic pairs, Conformation change, Over-runing clutch, Transforming factor