Chair back height adjustment mechanism

Claim 1

A chair comprising, in combination: a base portion, a seat portion mounted on said base portion, a pair of back mounting arms extending from said base portion on either side of said seat portion, a chair back including a structural chair back member completely enclosed within said chair back, a back support member extending through openings in the sides of said chair back and connected between said back mounting arms, a first C-shaped bracket secured to said back support member having a pair of vertically aligned apertures, one in each of the horizontally extending arms thereof, a second C-shaped bracket secured to the structural chair back member and facing in an opposed relationship to said first Cshaped bracket, said second C-shaped bracket also including a pair of vertically aligned apertures, one in each of the horizontally extending arms thereof, and an at least partially threaded stud including at one end thereof tool receiving means whereby rotation may be imparted to said stud, said stud extending through each of said vertically aligned apertures in both said first and said second C-shaped brackets, at least one of said apertures in one of said Cshaped brackets including threads therein constructed and arranged to coact with the threads on said stud to provide a relative linear movement between said one C-shaped bracket and said stud in response to rotation of said stud, at least one of said apertures in the other of said C-shaped brackets being loosely secured to said stud for linear movement therewith while permitting rotation of said stud with respect thereto, said first and second C-shaped brackets and said partially threaded stud being completely enclosed within said chair back and said chair back including an aperture in the bottom edge thereof to provide access to said tool receiving means on said stud.