Patent ID: 8398104

Claim:
A bicycle seat adjustable device comprising: an outer tube ( 10 ) being a hollow tube and a bottom cap ( 11 ) sealing a lower end of the outer tube ( 10 ); an inner tube ( 20 ) being a hollow tube and a piston ( 21 ) sealing a lower end of the inner tube ( 20 ), the piston ( 21 ) located in the outer tube and an outer air room ( 22 ) defined in the outer tube ( 10 ) and located between the piston ( 21 ) and the bottom cap ( 11 ), a clamp unit ( 40 ) connected to a top end of the inner tube ( 20 ), and a valve control device ( 30 ) comprising an outer path tube ( 31 ) located in the inner tube ( 20 ), a lower end of the outer path tube ( 31 ) connected to the piston ( 21 ) and a top end of the outer path tube ( 31 ) extending toward the clamp unit ( 40 ), a movable piston ( 32 ) movably mounted to the outer path tube ( 31 ), an outer oil room ( 33 ) and an inner air room ( 34 ) defined between the inner tube ( 20 ) and the outer path tube ( 31 ), the bottom cap ( 11 ) connected to an inner path tube ( 35 ) which has a top end extending into the outer path tube ( 31 ), a valve unit ( 36 ) connected to an upper end of the inner path tube ( 35 ) so as to form a path ( 38 ) and an inner oil room ( 37 ) in the outer path tube ( 31 ), the path ( 38 ) communicating with the outer oil room ( 33 ) and the inner oil room ( 37 ), the valve unit ( 36 ) controlling communication of the path ( 38 ).