A chair control assembly includes a base structure having first and second pivot points spaced from one another, a seat support structure coupled to the first pivot point, a back support structure coupled to the second pivot point and adapted to move between first and second positions, wherein the base structure does not move as the back support structure moves between the first and second positions, and a control link pivotably coupled to the seat support structure for rotation about a third pivot point and pivotably coupled to the back support structure for rotation about a fourth pivot point, wherein the third pivot point is rearward of the fourth pivot point when the back support structure is in the upright position, and the third pivot point moves forward relative to the fourth pivot point as the back support structure moves from the upright to reclined positions.

The adjusting mechanism serves for the setting of a restoring force acting on the backrest of a chair. A back support and a seat support are fastened on a support. A setting mechanism configured in the manner of scissors is provided for the weight setting. Said setting mechanism has two scissor arms which are connected to one another via a scissor pin. One of said scissor arms is formed by a spring element and is fastened with its front-side spring end on said support. The back spring end is fastened on said scissor pin. Said first scissor arm is connected to said back support in the manner of a connecting rod. An active lever length is defined between said scissor pin and a support pin about which said back support is mounted pivotably. A compact construction mode is achieved by the configuration of said scissor arm as a spring element.

A chair assembly includes a back support arrangement including a back support arrangement, a seat support arrangement and a four-bar arrangement that includes a rearward end and a forward end that is adjustable between a raised and lowered positions, and an arm rest assembly adapted to support the arm of a seated user thereon and supported on the forward end of the four-bar arrangement, wherein the rearward end of the four-bar arrangement is pivotably supported from an arm support structure for pivotable movement about a substantially vertical pivot axis such that the forward end of the four-bar arrangement is moveable between a first position and second position located laterally outward from the first position, and wherein the substantially vertical pivot axis is located forwardly of a rearmost edge of an upwardly-facing surface of the seat support arrangement.

An adjusting mechanism is provided for selectively setting a restoring force acting on a backrest of a chair. In a biasing unit of the adjusting mechanism, a spring segment is disposed between a head end and a follower end to bias the follower end to the remote position. The follower end is angularly movable on a cam surface between distal and proximate positions. In response to movement of a backrest of the chair from a normal position to an inclined position to permit the follower end to be forced by the cam surface to move from the remote position to a close position, two different restoring forces can be set by adjusting the follower end between the distal and proximate positions.

A chair for providing support to a user's spine to improve posture and for providing ways for the user to perform exercises. The chair may include a flexible connection that enables a back support to move side to side through a sidebending range of motion of the user. The back support, which may include a flexible chair spine, may be configured to adapt to the curvature of the user's spine when the user is seated in the chair. A seat of the chair may include channels and vents to improve air circulation within the seat.

A control assembly for a chair includes a base structure having a first pivot point and a second pivot point spaced from the first pivot point, a seat support structure having a forward portion pivotably coupled to the base structure for rotation about the first pivot point, a back support structure having a forward portion pivotably coupled to the base structure for rotation about the second pivot point, wherein the back support structure is adapted to move between upright and reclined positions, and wherein the seat support structure reclines rearwardly as the back support structure moves from the upright to reclined positions, and a control link having a first end pivotably coupled to a rearward portion of the seat support structure for rotation about a third pivot point, and a second end pivotably coupled to a rearward portion of the back support structure for rotation about a fourth pivot point.

A chair having a fixed support structure including two side uprights, a backrest having two side portions, and a pair of elastic joints connecting said side portions of the backrest to said side uprights, wherein each of said elastic joints comprises: a bushing fixed to a respective side upright, a helical spring having a longitudinal axis, the helical spring having an upper end resting against a front wall of the bushing, a compression member resting against a lower end of the spring, an upper attachment fixed to a corresponding side portion of the backrest, and a rigid connecting rod having an upper end and a lower end.

A mechanism for an office chair allows a pivoting resistance of a backrest support to be altered. The mechanism for the office chair, in which a small adjustment travel is sufficient in order to realize a large adjustment range of the pivoting resistance of the backrest, has an actuating element connected to the backrest support with a supporting and/or guide track for a functional element. The functional element brings about a change in the spring tension of a spring element during pivoting of the backrest support.

A chair assembly includes a back support arrangement that includes a back frame member and a forwardly-facing surface configured to support a user, a four-bar linkage assembly including a first linkage member, a second linkage member, a third linkage member and a fourth linkage member each pivotably coupled to one another such that the four-bar linkage assembly includes an upper end that is adjustable between raised and lowered positions, and an arm rest assembly supported on the upper end of the four-bar linkage assembly, wherein a lower end of the four-bar linkage assembly is pivotably supported from an arm support structure for pivotable movement such that the upper end of the four-bar linkage assembly is movable between a first position and second position located laterally outward from the first position, and wherein the fifth pivot point is located forwardly of the back frame member.

A chair assembly includes a base structure defining upper and lower portions, and a support structure, a seat support structure having a forward portion pivotably connected to the upper portion of the base structure for rotation about a first pivot point and a rearward portion, a back support structure having a forward portion pivotably connected to the lower portion of the base structure for rotation about a second pivot point that is located below and rearward of the first pivot point, and an upwardly extending back portion that moves rearwardly and downwardly as the back support structure pivots and the back portion moves, and a control link pivotably coupled to the seat support structure for rotation about a third pivot point and to the back support structure for rotation about a fourth pivot point each located rearward of the first and second pivot points.