Patent ID: 7661763

Claim:
An armrest for a chair, comprising: an armrest support; a sleeve movably mounted on the armrest support; a support arm mounted on the sleeve to move with the sleeve; a locking member mounted between the armrest support and the sleeve; a lifting device mounted between the armrest support and the sleeve and operable between a first position where the lifting device is locked by the locking member to lock the sleeve onto the armrest support and a second position where the lifting device is unlocked from the locking member to unlock the sleeve from the armrest support so that the sleeve is movable relative to the armrest support freely; wherein the armrest support includes a connecting member and an upright support post having a lower end mounted on the connecting member and having an inside provided with a receiving chamber to receive the lifting device; the locking member is mounted on an upper end of the support post of the armrest support and provided with a semi-circular locking hole which has a planar locking side: the lifting device includes: a mounting plate mounted on an upper end of the sleeve to move with the sleeve; a positioning member mounted on the mounting plate to move with the mounting plate; a movable shaft rotatably mounted on the positioning member and provided with an elongate toothed portion having a plurality of locking teeth that are rotatable with the movable shaft between a first position where each of the locking teeth of the movable shaft aligns with and is locked by the locking side of the locking hole of the locking member to lock the movable shaft onto the locking member and a second position where a planar side of each of the locking teeth aligns with and is unlocked from the locking side of the locking hole of the locking member to unlock the movable shaft from the locking member so that the movable shaft is movable in the support post of the armrest support freely; a slide slidably mounted on the positioning member and connected with the movable shaft to rotate the movable shaft relative to the positioning member; a control knob movably mounted on the positioning member and connected with the slide to move the slide relative to the positioning member; the slide of the lifting device is provided with an oblique guide slot and a driving hole; the control knob of the lifting device has a top provided with a driving rod slidable in the oblique guide slot of the slide to drive the slide to move relative to the positioning member when the control knob is movable relative to the positioning member; the positioning member of the lifting device has a top provided with a through hole; the movable shaft of the lifting device has an upper end provided with a rotation rod rotatably mounted in the through hole of the positioning member and a driven rod mounted in and driven by the driving hole of the slide.