Chair seat tilt control

Claim 1

A support mechanism for a tiltable chair with separate adjustments for front tilt and rear tilt including a base member adapted to be supported on a chair post, a first tube connected to said base member, said tube having a central axis, a seat support assembly including a pair of side plates, a second tube connected between and toward the rear of said side plates, a first sleeve member connected to one of said side plates toward the front end thereof, a second sleeve member concentric with said first sleeve member connected to said other of said side plates toward the front end thereof, said first and second sleeve members rotatably supported over ends of said first tube, and a pair of brackets, each bracket associated with one of said side plates and angularly tiltable with respect thereto, each bracket adapted to be connected to support a seat of said chair, a first torsion bar extending through and non-rotatably connected to one end of said first tube, said first torsion bar including an arm disposed external to said first tube, a second torsion bar extending through and rotatably supported within said second tube, said second torsion bar including an arm disposed external to said second tube and adapted to engage said arm of said first torsion bar, said first and second torsion bars operative to resist counterclockwise rotation of said seat support assembly about said first tube thereby resisting rear tilt of said seat, rear tilt torque adjustment means connected to one of said torsion bars to vary the torque exerted by said torsion bars to resist rearward tilt of said seat about said first tube, a torsion member pivotally supporting said brackets and non-rotatably connected at one end to one of said side plates and, at said other end, engageable with one of said brackets to exert a force resisting clockwise rotation of said seat about said torsion member thereby resisting front tilt of said seat and front tilt torque adjustment means connected between said torsion member and one of said brackets, said adjustment means operable to vary the torque to resist forward tilt of said seat about said torsion member.