Tension control mechanism for a chair

Abstract

The chair includes seat and back assemblies interconnected in a four-bar linkage. The chair further includes a tension mechanism comprising a coil spring projecting forwardly from a base and an adjustment linkage which is connected to said coil spring and to a front link of said four-bar linkage. A back linkage end of said adjustment linkage being axially movable along an axis of said coil spring and a front linkage end being vertically movable along said front link to adjust displacement of said adjustment linkage during rearward pivoting of said front link.

What is claimed is:  
     
         1 . A chair having a seat assembly and a back assembly which are interconnected in a four-bar linkage arrangement, the chair including a base wherein the four-bar linkage arrangement includes a base link fixed to the base and a front link pivotally interconnected to the base link and the seat assembly so as to pivot rearwardly upon tilting of said seat and back assemblies, said tension control mechanism including a spring arrangement comprising a coil spring affixed to the base link and an adjustment linkage having a back linkage end connected to a front end of said coil spring and a front linkage end connected to said front link, said back linkage end being slidable axially along the longitudinal axis of said spring and said front linkage end being slidable vertically along said front link wherein the vertical position of said front linkage end on said front link defines the axial displacement of said back end of said adjustment linkage during rearward pivoting of said front link.