Chair construction

A chair comprising:

• a base including a control;
• a seat including a seat support assembly pivotally supported by the control for movement about a seat tilt axis;
• a back tilt bracket subassembly pivoted to the control for movement about a first back tilt axis, the control biasing the seat support and the back tilt bracket subassembly toward upright positions;
• a back support structure pivoted at a lower end to the back tilt bracket subassembly for movement about a second back tilt axis spaced from the first back tilt axis;
• and
• a backrest supported on the back support structure, the backrest including a flexible shell and a lumbar adjustment mechanism operably mounted on the flexible shell for adjustably changing a shape of the flexible shell.

A chair comprising:

• a base including a control;
• a seat including a seat support assembly pivotally supported by the control for movement about a seat tilt axis;
• a back tilt bracket subassembly pivoted to the control for movement about a first back tilt axis, the control biasing the seat support and the back tilt bracket subassembly toward upright positions;
• a back support structure pivoted at a lower end to the back tilt bracket subassembly for movement about a second back tilt axis spaced from the first back tilt axis;
• and
• a backrest supported on the back support structure, the backrest including a backrest frame pivoted to the back support structure, and the seat support assembly including rigid side supports pivotally supporting the backrest frame at a third back tilt axis.

A chair comprising:

• a base including a control assembly;
• a seat pivotally supported by the control assembly for movement about a seat tilt axis, the seat having a rear edge and including side supports;
• a back support pivoted to the control assembly for movement about a back tilt axis that is located rearward of the rear edge of the seat, the seat and back support being operably supported by the control assembly for synchronous movement;
• and
• a backrest assembly operably supported on the back support and the control assembly, the backrest including a backrest frame pivoted to the back support at the back tilt axis and also pivoted to the backrest frame at a location proximate a seated user's hip joint.

A chair comprising:

• a base including a control assembly;
• a seat pivotally supported by the control assembly for movement about a seat tilt axis, the seat having a rear edge;
• a back support pivoted to the control assembly for movement about a back tilt axis that is located rearward of the rear edge of the seat, the seat and back support being operably supported by the control assembly for synchronous movement;
• a backrest assembly operably supported on the back support and the control assembly, the back support including a backrest frame and further including a flexible shell operably supported on the backrest frame for flexible postural support to a seated user, and still further including an adjustable lumbar mechanism operably mounted on the flexible shell, the lumbar mechanism being configured to change a shape of the flexible shell during adjustment of the lumbar mechanism;
• and
• a back tensioner attached to a lower edge of the flexible shell, the back tensioner biasing the lower edge rearwardly and downwardly.

A chair comprising:

• a base including a control assembly;
• a seat pivotally supported by the control assembly for movement about a seat tilt axis, the seat having a rear edge;
• a back support pivoted to the control assembly for movement about a back tilt axis that is located rearward of the rear edge of the seat, the seat and back support being operably supported by the control assembly for synchronous movement;
• and
• a backrest assembly operably supported on the back support and the control assembly, the back support including a backrest frame and further including a flexible shell operably supported on the backrest frame for flexible postural support to a seated user, and further including an adjustable lumbar mechanism operably mounted on the flexible shell, the lumbar mechanism being configured to change a shape of the flexible shell during adjustment of the lumbar mechanism and including lateral support arms that are configured to press on lateral side sections of the flexible back shell to bias the lateral side sections forwardly so that the lateral side sections provide side support to a seated user.

A chair comprising:

• a base including a control assembly;
• a seat pivotally supported by the control assembly for movement about a seat tilt axis, the seat having a rear edge;
• a back support pivoted to the control assembly for movement about a back tilt axis that is located rearward of the rear edge of the seat, the seat and back support being operably supported by the control assembly for synchronous movement;
• a backrest assembly operably supported on the back support and the control assembly;
• and
• an armrest operably supported on the back support for vertical adjustment;
• wherein the back support includes a spine assembly, an armrest mount slidably supported on the spine assembly that supports the armrest, and a latch on the armrest mount releasably engaging the spine assembly for vertically adjusting the armrest;
• wherein the armrest includes a hand control operably connected to the latch for releasing the armrest mount from the spine assembly for vertical adjustment of the armrest;
• wherein the backrest assembly includes a rod extension that is pivoted to an upper end of the spine assembly and extends upwardly therefrom;
• and
• wherein the back support includes a flexible shell, and including a lumbar slide slidably supported on the vertical rod extension, the lumbar slide engaging a rear surface of the flexible shell and being vertically movable to change a shape of the flexible shell.

A chair comprising:

• a back;
• a base including a control assembly;
• a seat supported on the control assembly;
• a back spine assembly supporting the back on the control assembly, the back spine assembly extending generally vertically at a location rearward of the back;
• and
• a flexible shell operatively mounted on the back and further including an adjustable lumbar mechanism operatively mounted on the flexible shell, being configured to change a shape of the flexible shell during adjustment of the lumbar mechanism and including lateral support arms that are configured to press on lateral side sections of the flexible shell to bias the lateral side sections forwardly so that the lateral side sections provide side support to a seated user
• an armrest assembly slidably supported on the back spine assembly for vertical height adjustment.