US Patent 7896440 Chair armrest having a height adjustable function

An armrest for a chair includes an armrest support, a sleeve movably mounted on the armrest support, a support arm mounted on the sleeve, a locking member secured in the armrest support, and a lifting device mounted between the armrest support and the sleeve. Thus, when the drive lever of the lifting device is pressed upward, the movable shaft of the lifting device is unlocked from the locking member so that the movable shaft is movable in the locking member and the armrest support freely, and the sleeve is movable relative to the armrest support to adjust the height of the support arm.