Abstract: A tiltable chair including a base member (44), a seat (32), a back (34), and a linkage assembly (40) adapted to allow the seat and back to tilt downwardly and rearwardly and to allow pivotal movement of the seat about a pivot axis (52) in substantial alignment with the hip joints of a user. Other aspects of the invention are to provide a vertically adjustable column (42) for supporting the seat of the chair, a support assembly including a frame member (33) having a central opening therethrough and a receptacle formed around the perimeter thereof, a carrier member adapted to fit inside the receptacle, and a membrane of elastic material (210) covering the central opening, and a pair of armrests (36) adapted to be mounted to the chair to allow pivotal movement thereof.

Abstract: An apparatus for controlling the tilt range of a chair and the resistance to tilting of the chair including a torsion spring mounted to an axle, a tilt rate adjustment mechanism, a forward tilt limiter and a rearward tilt limiter. The tilt rate adjustment mechanism includes an outer sleeve member mounted to the spring. An arm extends radially outward from the sleeve and operably engages a block member threadably attached to a screw. A first and second gear member are actuated to rotate the screw so as to move the block member which thereby moves the arm a desired amount to adjust the initial return torque of the spring. The forward tilt limiter includes an arm extending outwardly from the axle. The arm operably engages a pivot member pivotally attached to a tilt control housing. The rearward tilt limiter also includes an arm extending outwardly from the axle. The arm operably engages a cam member pivotally attached to the tilt control housing.

Abstract: A low profile knee-tilt chair control for controlling biased tilting between a chair seat plate and a chair base plate of a pedestal base chair wherein the chair base plate is supported by a single vertical spindle at the rear of the base plate, and the chair seat plate pivots about a horizontal axis at the front of the base plate. The chair seat is biased to an at-rest position by a low profile, conical helical compression spring operable between the base plate and chair seat and located between the spindle and the horizontal pivot axis of the base plate. The low profile, conical helical compression spring is so mounted relative to the base plate and chair seat plate that the small coils of the compression spring may pass through the large coils during compression of the spring. The control is further characterized by a lockout for securing the chair seat plate against tilting relative to the base plate in either of two different, selectable, at-rest positions.