Chair back height adjustment mechanism

摘要

A chair back height adjustment mechanism for a chair having a chair back supporting standard and a chair back bracket with a chair back or backrest mounted thereon includes a rack gear on the chair back standard, a pinion gear supported in a bearing on the chair back bracket, a worm gear coaxial with the pinion gear, and worm threads on a dial shaft supported on the bracket. Rotation of the dial causes the worm member to rotate the worm gear and the pinion gear whereby the bracket supporting the pinion gear is translated in relation to the chair back standard. The chair back can only be adjusted by operation of the dial due to the nature of the worm and worm gear combination, thus preventing changes in the adjusted position of the chair back by contact with the chair back.