Adjustable chair having roller cam adjustment mechanism

Claim 1

An adjustment mechanism for a chair or the like to permit horizontal and swiveling movement of the chair, comprising: a base, having a top plate member with an opening; a seat structure having a bottom member with an opening formed therein; bearing means interposed between the bottom of said seat structure and the top of said top plate member to permit free movement between said seat structure and said base; a chair post connected to said seat structure and extending downwardly through said opening in said seat structure and said top plate member, said chair post being cylindrical and having a center opening, said chair post being smaller in lateral dimension than said top plate member opening to permit lateral movement of said chair post in any direction; a shaft extending through said center opening in said chair post; brake means supported on a lower end of said shaft for tightly frictionally engaging said top plate of said base for locking said seat in its adjusted position, said brake means comprising a lower brake plate and an upper brake plate disposed between said lower brake plate and said top plate, said upper brake plate having a central opening which is smaller than said lower brake plate such that said upper brake plate overlaps said lower brake plate, said upper brake plate having an outer dimension which is greater than said opening in said top plate member; and means for releasing said brake means to permit horizontal and swiveling movement of said chair.