Extensible chainwheel for a bicycle powertrain assembly
First Claim
Patent Images
1. A drive sprocket for a bicycle crankset, said drive sprocket comprising:
- a toothed ring, the ring comprising teeth having one pitch in correspondence with one chain pitch, the ring being divided into a plurality of segments, the segments being borne by a frame, the frame being rotationally movable about a crankset axle, each said segment being movable with respect to the frame in a plane perpendicular to the crankset axle between a low position and a high position in which each said segment is further distant from the crankset axle, thereby defining a small diameter state and a large diameter state of the sprocket, a system for transferring each said segment from one of said low and high positions to another of said low and high positions, and an indexing mechanism to control the system for transferring said segments, wherein each said segment is floatingly mounted with respect to the frame, and wherein said system for transferring each said segment between said low and high positions transfers each said segment in guided movement along a trajectory with respect to the frame, said trajectory of movement having a radial component and a tangent component, said tangent component being greater than zero.
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Abstract
A driving sprocket, or chainwheel, for a bicycle crankset having a toothed ring whose ring is divided into a plurality of segments, the segments being borne by a frame that is rotationally movable about a crankset axle, each sprocket segment being movable between a low position and a high position, a system for transferring each segment to transfer said segment from one position to another, and an indexing mechanism to control the system for shifting the segments. Each segment of the driving sprocket is floating mounted with respect to the frame and is guided in its transfer movement along a trajectory having a radial component and a tangent component.
24 Citations
25 Claims
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1. A drive sprocket for a bicycle crankset, said drive sprocket comprising:
a toothed ring, the ring comprising teeth having one pitch in correspondence with one chain pitch, the ring being divided into a plurality of segments, the segments being borne by a frame, the frame being rotationally movable about a crankset axle, each said segment being movable with respect to the frame in a plane perpendicular to the crankset axle between a low position and a high position in which each said segment is further distant from the crankset axle, thereby defining a small diameter state and a large diameter state of the sprocket, a system for transferring each said segment from one of said low and high positions to another of said low and high positions, and an indexing mechanism to control the system for transferring said segments, wherein each said segment is floatingly mounted with respect to the frame, and wherein said system for transferring each said segment between said low and high positions transfers each said segment in guided movement along a trajectory with respect to the frame, said trajectory of movement having a radial component and a tangent component, said tangent component being greater than zero. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A drive sprocket for a bicycle crankset, said drive sprocket comprising:
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a ring comprising a plurality of teeth having a pitch corresponding with a pitch of a chain adapted to mesh with said drive sprocket for comprising a component of a bicycle transmission assembly; said toothed ring comprising plurality of segments, each of said plurality of segments having a plurality of said plurality of teeth of said ring; a frame supporting said segments, said frame adapted to be rotationally movable about a crankset axle of a bicycle; a transfer system for movement of said plurality of segments relative to said frame between a small diameter position of said drive sprocket and a large diameter position of said drive sprocket, each said sprocket segment being spaced farther apart from an axis of rotation of said drive sprocket in said large diameter position than in said small diameter position, said transfer system moving each said segment successively, one after another, during an extent of rotation of each said segment about said axis of rotation corresponding to a non-engagement phase between said teeth of each said segment and said chain; said transfer system comprising an arrangement of parts to guide each of said sprocket segments successively along a predeterminate path of movement, said predeterminate path of movement comprising a combination of radial movement and tangential movement greater than zero, said radial movement being radial with respect to said axis of rotation and said tangential movement being tangential with respect to a circle centered on said axis of rotation; an indexing mechanism to control said transfer system for movement of said drive sprocket between said small and large diameter positions. - View Dependent Claims (22, 23)
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24. A drive sprocket for a bicycle crankset, said drive sprocket comprising:
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a ring comprising a plurality of teeth having a pitch corresponding with a pitch of a chain adapted to mesh with said drive sprocket for comprising a component of a bicycle transmission assembly; said toothed ring comprising plurality of segments, each of said plurality of segments having a plurality of said plurality of teeth of said ring; a frame supporting said segments, said frame adapted to be rotationally movable about a crankset axle of a bicycle; a transfer system for movement of said plurality of segments relative to said frame between a small diameter position of said drive sprocket and a large diameter position of said drive sprocket, each said sprocket segment being spaced farther apart from an axis of rotation of said drive sprocket in said large diameter position than in said small diameter position, said transfer system moving each said segment successively, one after another, during an extent of rotation of each said segment about said axis of rotation corresponding to a non-engagement phase between said teeth of each said segment and said chain; said transfer system comprising an arrangement of parts to guide each of said sprocket segments successively along a predeterminate path of movement, said predeterminate path of movement comprising a combination of radial movement and tangential movement, said radial movement being radial with respect to said axis of rotation and said tangential movement being tangential with respect to a circle centered on said axis of rotation; an indexing mechanism to control said transfer system for movement of said drive sprocket between said small and large diameter positions; wherein; said plurality of segments consists of four segments, each of said four segments having an identical number of teeth for meshing with the chain, each of said segments following, in a direction of rotation about said axis of rotation, a preceding one of said segments, each of said segments having a forwardmost tooth and a rearwardmost tooth; in said small diameter position of said drive sprocket, said segments are adjacent each other, whereby the forwardmost tooth of one of said segments is spaced behind the rearwardmost tooth of a preceding segment by a distance corresponding to one pitch, or a whole number multiple of said pitch, of the chain; in moving along said predeterminate path of movement from the small diameter position of said drive sprocket to the large diameter position of said drive sprocket, each of said segments is moved substantially tangentially so that said forwardmost tooth of one of said segments is spaced behind said rearwardmost tooth of said preceding segment by an additional distance corresponding to one additional pitch of said chain, or a whole number multiple of said pitch of said chain. - View Dependent Claims (25)
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Specification