Patent ID: 8191964

Claim:
An adjustment device for bicycle seat, comprising: a seat tube; a seat post having a connection portion located close to a top of the seat post and a lower end of the seat post movably inserted into the seat tube, at least one through hole defined through a wall of the connection portion; a seat connector connected to the top of the seat post and adapted to be connected with a seat; an adjustment device located between the seat connector and the seat post so as to control movement between the seat post relative to the seat tube, the adjustment device including an adjustment path which is controlled to be in communication with the at least one through hole or to be isolated from the at least one through hole, and a balance unit connected to the connection portion and including a cylinder and a piston ring movably received in the cylinder, the piston ring defining an inner space of the cylinder into a liquid space and an air space, the cylinder including a supply path which communicates with the liquid space and the at least one through hole.