Variable ratio traction drive

Claim 1

A traction drive of steplessly-variable drive ratio comprising an input member, an output member, first and second coaxial torus discs, the first disc having a driving connection with one of the members, a number of first rollers mounted between the discs, means to apply a force to urge the toroidal surfaces on said discs into engagement with the first rollers, means to vary the angles of inclination of the rotary axes of the first rollers relative to planes perpendicular to the rotary axis of the discs to vary the relative speeds of the discs, and a combined thrust bearing and differential mechanism comprising two races rigidly connected respectively to the first and second torus discs and presenting opposed raceways, a plurality of second rollers between and engaging the raceways so as to transmit said force and arranged with their rotary axes lying in an imaginary conical surface of which the axis is the rotary axis of the discs, the raceways having bearing surfaces which are surfaces of revolution about the rotary axis of the discs, each bearing surface being formed by rotating about said axis either a straight line inclined to said axis or a circular arc which is concave towards said imaginary conical surface, and whose chord is inclined to said axis, the radius of the arc being greater than the perpendicular distance between the arc and said imaginary conical surface, a carrier for said second rollers, a driving connection between the carrier and the other of said members, and rotary bearing means for the second rollers and located on the carrier in mutually spaced relation, each said bearing means comprising a pin supported by said carrier and an anti-friction bearing between the pin and the second roller supported by the pin, the second torus disc deriving its rotational movement solely from the first and second rollers.