Patent ID: 7367622

Claim:
A tension adjustment mechanism for controlling tilting resistance of a seat-back assembly in a chair, said tension adjustment mechanism comprising: a control body; a pivot member pivotally connected to said control body so as to pivot during tilting of said seat-back assembly; a biasing member acting on said pivot member to resist pivoting of said pivot member and resist tilting of said seat-back assembly, said biasing member including at least one movable biasing element which is displaceable in opposite first and second directions to vary the tilting resistance generated by said biasing member; a cam member which supports said biasing element and is movable in said first and second directions to displace said biasing element wherein said cam member includes a cam surface which is tapered in a sideward direction on opposite sides of said cam member; and a drive arrangement having a rotatable adjustment shaft which extends sidewardly within said control body and is manually rotatable, said drive arrangement further including drive members mounted on said adjustment shaft so as to be sidewardly movable toward or away from each other depending upon the direction of rotation of said adjustment shaft, said drive members including cam surfaces which are sidewardly tapered and cooperate with said opposite sides of said tapered cam surface on said cam member wherein movement of said drive members toward each other effects displacement of said cam member in said second direction to counteract said biasing element and movement of said drive members away from each other permits displacement of said cam member in said first direction corresponding to the direction which said biasing element acts on said cam member.