Two sprocket tooth trimming methods and the structure thereof for the

Abstract

A multiple sprocket assembly for use in a bicycle comprising: (1) at least a large sprocket wheel and a small sprocket wheel, each of the large and small sprocket wheels having a plurality of teeth on an outer edge thereof, and the large sprocket wheel having more teeth than the small sprocket wheel; (2) each of the sprocket wheels being adapted to engage with a chain guided by a derailleur; the chain comprising a plurality of rollers connected in series by link plates. The multiple sprocket assembly is characterized in that the small sprocket wheel has at least two consecutive teeth, each with a portion of its side surface trimmed off, and the large sprocket wheel has at least three consecutive teeth each also with a portion of its side surface trimmed off, so as to avoid interference between the link plates and the large sprocket when the chain is being shifted from the small sprocket to the large sprocket. In a preferred embodiment, at least two of the trimmed portions on the small sprocket are formed on the first distal side surface, and the trimmed portions on the large sprocket contain at least two trimmed portions on the second distal side surface and at least one trimmed portion on the second proximal side surface. The side surfaces of the teeth of the small sprocket are trimmed in such a manner such that the escape roller will not be immediately lifted up, but will be pushed laterally as a result of the trimmed portions of the small sprocket. The side surfaces of the teeth of the large sprocket are trimmed in such a manner such that one of the surfaces contains an axially extending portion, which serves as a fulcrum for the engage roller to be pivotally engaged with the large sprocket.