Patent ID: 7434887

Claim:
A steplessly height-adjustable armrest structure, comprising a base securely joined to a seat; a fixed tube securely joined to the base, the fixed tube having a rack on an inner side thereof; and an armrest body inserted in the fixed tube; the armrest body having a movable gear fitted thereon, which engages the rack on the inner side of the fixed tube; the armrest body having an immovable gear fitted thereon, which is near to the movable gear, and fixed so as not to rotate; the armrest body including an immobilizing component arranged above both the movable gear and the immovable gear; the immobilizing component having a slot thereon; the immobilizing component being fitted on the armrest body by means of a fixed element, which is passed through the slot and fixed to the armrest body; the immobilizing component having an engaging toothed portion on a lower end thereof; the immobilizing component being movable to a lower position so as to engage both the movable gear and the immovable gear; the immobilizing component being movable to a higher position to be away from the movable gear and the immovable gear; the armrest body having a position-limiting protrusion thereon; the immobilizing component having an upper inserted rod portion; the immobilizing being biased to said lower position by means of an elastic element, which is positioned around the inserted upper inserted rod portion with lower and upper ends thereof contacting the component immobilizing component and a lower side of the position-limiting protrusion respectively; the armrest body including a control member, which is joined to an upper end of the upper inserted rod portion of the immobilizing component; the immobilizing component having a connecting piece joined to the lower end thereof; a co-moving rod being positioned under the movable gear and the immovable gear; the co-moving rod being pivoted to the armrest body at a middle portion thereof; the co-moving rod being pivoted to a second end of the connecting piece at one end thereof; the co-moving rod having a position-keeping tooth on other end thereof to engage the movable gear.