Patent ID: 7445287

Claim:
A seat device for a chair comprising: an angle-adjustable lumbar support, with a lower portion of the lumbar support formed as a shaft for positioning pin lugs of a base and fixed blocks on the shaft, wherein the shaft has an external teeth portion at one end; a movable block having an internal teeth portion matching with the external teeth portion and joined with one of the fixed blocks by sliding; an elastic member positioned between inner holes of the external teeth portion of the shaft and the internal teeth portion of the movable block; two outer covers securing the fixed blocks; and a lifter pivoted to one of the two outer covers and secured with the movable block; whereby the movable block is forced outwards by the elastic member and the internal teeth portion is moved away from the external teeth portion when the lifter is pressed from an original position so as to adjust an angle of the lumbar support; and the movable block is forced inwards by the lifter and the internal teeth portion engages with the external teeth portion again under resistive force when the lifter is returned to the original position so that the lumbar support has a stable position.