Continuous-torque variable-speed transmission

A variable speed transmission apparatus for changing the speed of a driven member relative to the speed of a driving member, comprising:

• a plurality of driven gears;
• a plurality of annular cam gears each in continuous driving engagement with a corresponding one of said driven gears, each of said cam gears having an inner cam surface with at least one peak and at least one valley;
• a hollow drum mounted for rotation about an axis and having a plurality of apertures extending from an inner drum surface to an outer drum surface, at least one of said apertures corresponding to each of said cam gears, and said cam gears being mounted for rotation about said outer drum surface with said inner cam surface opposite to said at least one corresponding aperture;
• a plurality of detents, one corresponding to each of said drum apertures and each arranged for reciprocating radial movement within its corresponding drum aperture;
• a shift member mounted within said drum for axial rotation about said drum axis, said shift member comprising one or more cam surfaces disposed radially around the rotational axis of the shift member for respectively engaging said detents to hold the engaged detent in a first position at which it engages the valley of the corresponding cam gear, and a second position at which the detent is in a disengaged position;
• positioning means for selectively rotating said shift member in either axial direction relative to said drum so as to cause a selected detent to engage the valley of its corresponding cam gear such that a driving connection is made between said driving member and said driven member through said engaged cam gear, the inner cam surface of said cam gears and the outer cam surface of said shift member being contoured relative to each other to time the axial rotation of said shift member such that said axial movement may commence only about when the peak of the cam gear to be disengaged from its corresponding detent is substantially aligned with the valley of an adjacent cam gear to be engaged by its corresponding detent, and said axial movement may cease only about when the valley of the cam gear to be disengaged is substantially aligned with the peak of the adjacent cam gear to be engaged;
• and
• reconciling means for matching the relative speed of the driving member with that of the driven member during disengagement and engagement between selected cam gears.