Abstract: An improved crank structure for bicycle, wherein, a gear plate connector and a pedal connector are installed on two ends of a crank, and there are a first side and a second side extended between the gear plate connector and the pedal connector; there are two pairs of thickness and width perpendicularly and crosswise installed on each of the first side and the second side, and the thicknesses and widths can be measured; the feature is the crank is a non-symmetrical structure. Further, at least one cavity is positioned between the first side and the second side of crank for loosing weight and decreasing cost.

Abstract: In a combination structure of sprocket set and rivet, the rivet includes a head part and a drum bolt part. Two sprockets are connected and secured into one body by arranging the bolt part into a penetration-through hole between adjacent sprockets and by applying methods of stamping and riveting on the bolt part. The head part of the rivet is also arranged with a recessed internal hexagonal hole seat to make its outline resemble as an internal hexagonal screw. On the outline, by comparison with a prior rivet that only has a monotonous flat head part, the internal hexagonal hole seat of the head part of the rivet of the present invention not only further has a sense of beauty and a feeling of high added-value, but also it can have an auxiliary positioning function during the processes of stamping and riveting to make the processes of stamping and riveting be more solid and its connection strength more strong.

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.