Variable diameter gear device with diameter changer for constant pitch gear tooth sequence

A variable diameter gear device for use in a variable ratio transmission system, the variable diameter gear device comprising:

• (a) an axle defining an axis of rotation;
• (b) a displaceable gear tooth sequence comprising a plurality of interconnected gear teeth lying on a virtual cylinder coaxial with said axle, said gear teeth being spaced at a uniform pitch;
• (c) a torque linkage mechanically linked to said axle and to said gear tooth sequence so as to transfer a turning moment between said axle and said gear tooth sequence;
• and
• (d) a diameter changer including at least one disc having a spiral track, and wherein each of said gear teeth is mechanically linked to said spiral track such that rotation of said at least one disc relative to said axle causes variation of an effective diameter of said virtual cylinder while maintaining said virtual cylinder centered on said axis of rotation and while said uniform pitch remains constant.