Abstract: A tooth contour structure for large sprocket set of bicycle having at least three characteristic teeth arranged on a larger sprocket of two adjacent sprockets, wherein the right side of a first characteristic tooth has a curve surface and a cut portion. Between the first characteristic tooth and a second characteristic tooth a tooth valley bottom edge has a projection surface biased toward the smaller sprocket. The arc of a top edge of the projecting surface is formed according to the path and curvature of the upper chain. The top edge has a slant angle. A recession is formed below the first characteristic tooth.

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: A tooth contour structure for large sprocket set of bicycle, at least three characteristic teeth are arranged on the larger sprocket of two adjacent sprockets for the large sprocket set, wherein the right side of the first characteristic tooth has a curve surface and a cutting portion fulfilled with a moving path for a chain, and between the first characteristic tooth and second characteristic tooth a tooth valley bottom edge is a projection butting surface formed by stamping and biased toward the smaller sprocket, and the arc of the top edge for the butting surface is formed according to the path and curvature of the upper chain, and the top edge is also formed into a slant angle, and a recession is arranged below the first characteristic tooth, not only the process is easy; the manufacturing cost is low; the chaining-up path is steady and smooth; the fixed-point shifting can be proceeded; but also the shifting efficiency is raised; the reliability is increased; the usage life is prolonged; and the running n

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.