Importance

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Abstract

An improvement of multi-stage sprocket assembly for bicycle includes at least a small sprocket and a large sprocket. The large sprocket includes at least two different sets of teeth. The large sprocket defines a radial second center line across the thickness thereof while the first set of teeth each defines a first center line across the teeth crest and parallel to the second center line. The first center line is moved away from the second center line in an opposite direction of the small sprocket. The second set of teeth includes at least two consecutive special teeth. The first special tooth has a recess formed under the root in a lateral side facing the small sprocket to avoid interference with the chain during shifting movement. The second special tooth has its first center line moving away from the second center line of the large sprocket toward the small sprocket for engaging with the chain at a small rotation angle without raising the chain or changing the tension of the chain during shifting movement. An additional third special tooth with a truncated top portion may be provided next to he second special tooth to smooth shifting movement either for shifting up or down or at any shifting angle. Shifting movement may therefore be accomplished at the second special tooth without interference with the chain.

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First Claim