Patent ID: 8777318

Claim:
A height adjustment mechanism for armrests comprising: a tubular base whose lower part is connected to a chair seat while one side surface of an upper part thereof is disposed with a plurality positioning holes arranged vertically with a certain interval; the positioning holes are connected by a vertical long slot; an outer sleeve that is disposed around an upper part of the tubular base and having an opening arranged at an upper end thereof and an armrest pad set at a top surface thereof; a strip rack that is mounted in the outer sleeve and located inside the tubular base and having a groove formed along a length direction thereof, an opening on an upper part thereof and corresponding to the opening of the outer sleeve, and an insertion slot on a lower part thereof and corresponding to one of the positioning holes of the tubular base; a pull handle that is mounted in the groove of the strip rack and having a projective rod that is disposed on a top end thereof and is corresponding to the opening of the strip rack and the opening of the outer sleeve; a positioning member arranged at a lower end of the pull handle and being driven to be moved by the pull handle; one end of the positioning member is disposed with a locking part that is inserted through the insertion slot of the strip rack to be locked in one of the positioning holes of the tubular base; a press member that is connected to the projective rod of the pull handle and is exposed outside the opening of the outer sleeve; while the press member being moved vertically, the pull handle is driven by the press member to move synchronously and vertically in relation to the strip rack; and an alignment member having at least a pair of projecting blocks and at least a pair of long slots corresponding to each other and respectively disposed on corresponding surfaces of the strip rack and the pull handle; the projecting block is able to move along the long slot so that displacement of the pull handle in relation to the strip rack is limited by the long slot; wherein the locking part of the positioning member is released from one of the positioning holes of the tubular base and is moved vertically for adjusting height of armrests when the pull handle is moved upward; wherein the locking part of the positioning member is released from one of the positioning holes of the tubular base and then is locked into another positioning hole of the tubular base when the pull handle is moved downward.