Abstract: A structural support shell for a tilt-back chair has a back portion, a seat portion, and a flexible compression zone extending between the back and seat portions in an integrally molded, one-piece unit. The chair has a base with a recline control pivoting recline control lever. The seat portion of the shell is fixed to the base and the back portion of the shell is fixed to the recline control lever. The flexible compression zone provides a simplified construction for an ergonomic chair design having an effective axis of rotation between the back portion and seat portion which is located above the seat portion, forward of the back portion, and generally adjacent to the hip joints of a seated user.

Abstract: A chair, with independent control of a lumbar portion of a seat back and a thoracic portion of the seat back, has a seat connected with a base and a control connected with the base, generally under the seat. A first support, pivotally connected with the control, extends from the control to the thoracic portion of the seat back. A second support extends to the lumbar portion of the seat back. The two supports operate independently and the thoracic and lumbar portions of the seat back rotate independently rearward with respect to the seat, providing sympathetic back support for a user. The thoracic portion may rotate laterally to follow twisting movements of a user's thoracic region. The lumbar portion may be connected with the second support to limit lateral rotation of the lumbar portion.

Abstract: A structural support shell for a tilt-back chair has a back portion, a seat portion, and a flexible compression zone extending between the back and seat portions in an integrally molded, one-piece unit. The chair has a base with a recline control and pivoting recline control lever. The seat portion of the shell is fixed to the base and the back portion of the shell is fixed to the recline control lever. The flexible compression zone provides a simplified construction for an ergonomic chair design having an effective axis of rotation between the back portion and seat portion which is located above the seat portion, forward of the back portion, and generally adjacent to the hip joints of a seated user.

Abstract: A chair, with independent control of a lumbar portion of a seat back and a thoracic portion of the seat back, has a seat connected with a base and a control connected with the base, generally under the seat. A first support, pivotally connected with the control, extends from the control to the thoracic portion of the seat back. A second support, pivotally connected with the control, extends from the control, to the lumbar portion of the seat back. The two supports operate independently and the thoracic and lumbar portions of the seat back rotate independently rearward with respect to the seat, providing sympathetic back support for a user. The thoracic portion may rotate laterally to follow twisting movements of a user's thoracic region. The lumbar portion may be connected with the second support to limit lateral rotation of the lumbar portion.

Abstract: A chair particularly suited for institutional multipurpose rooms, and the like, includes a base and a shell with a back and a seat which are constructed for generally contemporaneous movement. A first support connects the base with a medial portion of the seat to support the same in a cantilevered fashion, and is resiliently flexible to permit the shell to rock in response to fore-to-aft movement of a seated user. A second support connects the base with the back, and is also resiliently flexible to permit and control the rocking motion of the shell in a manner that provides improved comfort, and reduces sitting fatigue. Preferably, the support also permits the shell to move in a controlled manner from side to side in response to lateral movement of a seated user.