Patent ID: 8083289

Claim:
An adjusting structure for a seat tube of a bicycle comprising: a seat tube including a cylinder-shaped positioning seat integrally formed on an upper side thereof, the positioning seat including two annular toothed disks integrally formed on two sides thereof respectively, and each annular toothed disk including a first through hole laterally arranged at a central portion thereof; two cylinder-shaped engaging blocks symmetrically provided on two sides of the positioning seat, and each engaging block including an internal side surface and an external side surface, on the internal side surface being integrally formed an annular toothed member in response to corresponding to the annular toothed disk, and each engaging block including a second through hole horizontally mounted laterally formed at a central portion thereof; two cover members symmetrically fixed on outer sides of the two engaging blocks, and each cover member including an inner surface and an outer surface, between the inner surface of the cover member and the external side surface of the engaging block being defined with a fixing bore, at two sides of which is formed an opening, to receive a fixed rod under a saddle, each cover member further including a third through hole laterally formed at a central portion thereof; a locking unit laterally passing through the first, the second, and the third through holes and allowing to be alternatively rotated tightly or loosely; wherein as the locking unit is in a tightly rotated state, the relative positions among the positioning seat, the two engaging blocks, and the two cover members are fixed, and the fixed rod of the saddle allows to be secured in the fixing bore; wherein as the locking unit is in a loosely rotated state, the engaging blocks are rotated along about the locking unit, and a distance of the engaging block in response to corresponding to the cover member is increased so that the fixed rod of the saddle can obtain an have enough space to slide straightly along the fixing bore; wherein between the engaging block and the cover member in response to corresponding to the engaging block is defined with a positioning structure to prevent the engaging block from rotation relative to the cover member, the positioning structure includes a projection and a recessed portion in response to corresponding to the projection.