Expandible sprocket

Claim 1

A variable sprocket comprising in combination: an axle, a drive flange mounted on said axle, an indexing flange rotatably mounted on said axle opposite of said drive flange and having a plurality of spiral-wavy-cams, two sprocket-segment-planets, said sprocket-segment-planet having leading teeth which provide initial contact with a chain and additional chain engaging teeth for subsequent engagement with said chain, at least a portion of said leading teeth is removed such that their profile is reduced relative to the profile of said chain engaging teeth, at least two idler-planets sandwiched between said flanges, coupling means for transmitting tangential forces between said spiral-wavy-cams and said drive flange, cam follower attached to said planets for engaging with and following said spiral-wavy-cams, said spiral-wavy-cams comprising a series of alternating depressions and hills which move the planets closer and further to and from said axle, respectively, as said planets slides along said spiral-wavy-cams, said chain made of links and having a pitch equalling the length of said chain divided by the number of said links, said chain wrapping approximately one half of the periphery of said variable-sprocket, tension in said chain generating tangential loads on said sprocket-segment-planets which are transmitted through said coupling means to said drive flange, tension in said chain also generating radial loads on said planets which are transmitted by said cam follower to said spiral-wavy-cams forcing and securing the cam follower in said depression, the location of said planets when their cam follower are seated in said depressions and when both sprocket-segment-planets are engaged with said chain is such that the length of chain which is trapped between said sprocket-segment-planets is a whole number of pitches.