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 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 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 back assembly includes a substantially rigid back frame assembly, a back shell member operably supported by the back frame assembly and including a laterally extending top portion, a laterally extending bottom portion and a pair of longitudinally extending side portion extending between the top portion and the bottom portion and cooperating therewith to define an open space therebetween, wherein the pair of side portions are substantially rigid in a lateral direction, and wherein the back shell member is substantially rigid in a lateral direction and substantially flexibly resilient in a fore-to-aft direction, and a cover having a first surface adapted to support a seated user and a second surface opposite the first surface, wherein the cover is positioned over the back shell member to cover at least a portion of the open space.

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.

A spring actuated rocking mechanism can be attached to the legs of a collapsible chair to allow for the user to rock in the collapsible chair. The mechanism may be attached at the factory or retrofitted to the chair. The rocking mechanism can be attached to the end of a leg or disposed within a leg, having a leg portion above and below the mechanism.

A chair includes a support base body portion; a backrest rotatably supported with respect to the support base body portion on an axis in a width direction of the support base body portion and being displaceable from an initial state to an inclined state of being inclined rearward; a biasing member configured to bias the backrest in the inclined state, in a direction of returning to the initial state; an adjuster configured to adjust a biasing force of the biasing member; and an operating member joined to the adjuster and configured to operate the adjuster, wherein the biasing member is provided in the backrest or the support base body portion, the adjuster is provided in the backrest, and the operating member is disposed behind the axis and on one side of the backrest in the width direction.

A body support assembly includes a seat assembly and backrest assembly supported by a tilt control assembly. Methods of using and assembling the body support assembly are provided.