Abstract: A backrest for use with a chair that has a seat and a base. The backrest includes a lower member having a proximal end and a distal end, and upper member attached to the chair at the proximal end. A spring-hinge mechanism pivotally connects the lower member in the vicinity of the distal end to the upper member. A lumbar support is attached to the upper member and the lower member and spans the spring-hinge mechanism. In use a user sitting on the seat may, by anterior flexing of the user's upper back cause the upper member to pivot relative to the lower member from an unflexed position to a flexed position.

Abstract: A rack structure for a chair includes a chair back member having a frame and a mounting support. The frame includes a support cushion disposed on the front side thereof for supporting a user's waist correspondingly. The frame further includes two first connecting tabs fixed on the back sides of the top ends of two sides thereof individually and two second connecting tabs formed on and extending from the two sides thereof respectively. The mounting support is fixed onto a base and extends upwardly therefrom. The mounting support includes two coupling segments and two connecting projections arranged on the top ends and the intermediate sections of two sides thereof respectively. Between each coupling segment and each connecting projection is couplingly attached a resilient member. The first and second connecting tabs of the frame are connected with the coupling segments and the connecting projections of the mounting support individually.

Abstract: A support member configured for attachment to a back assembly and a chair component is disclosed. One disclosed embodiment of the support member may be included in a chair that includes a base, a back assembly and the support member. The back assembly includes an extension attached to a back frame. The extension is attached to the base such that the back assembly is moveable relative to the base. The support member is attached to the extension and the base. The support member is more rigid than the extension. Preferably, the extension is composed of elastomeric material.

Abstract: A chair comprising, a base structure including two rear tubular elements open at the top, a backrest having two tubular portions open at the bottom and aligned to said tubular elements of the base structure, and two elastic devices, each of which has a top support inserted in a tubular portion of the backrest, a bottom support inserted in the corresponding tubular element of the base structure, and an elastic element flexurally deformable to enable tilting between the top support and the bottom support, wherein each of said elastic devices comprises a plurality of sectors stacked on top of one another and arranged between the top support and the bottom support, and wherein, in a resting position of the elastic element, a plurality of slits are formed on the rear side of each elastic device between each pair of adjacent sectors.

Abstract: There is provided a link mechanism for a chair that is a link mechanism that is used at a chair, the link mechanism for a chair having: a first link whose one end is connected to a bottom surface of a link that supports a seat surface portion of the chair; a second link whose one end is connected to another end of the first link; a first joint portion rotatably connecting the first link and the second link; a second joint portion provided at another end of the second link; and a first elastic resistance unit imparting elasticity in a rotating direction to the second joint portion.

Abstract: A chair comprising a supporting structure having a seat and a backrest, in which the backrest comprises a deformable resting portion made of plastic material which has a non-planar resting surface provided with at least one weakened area which enables an elastic deformation of the resting portion so that the resting portion assumes a configuration bent backwards under the action of a thrust applied backwards by the user, two uprights formed integrally on the lateral sides of the resting portion, and two side connection elements, which connect the backrest to the supporting structure, formed integrally at the bottom ends of the uprights. The backrest is provided with elastic stiffening elements made of a material different from the material constituting the resting portion and arranged only in an area corresponding to the uprights so as to bestow upon said uprights a rigidity to bending higher than that of the resting portion.

Abstract: A vehicle seat comprises a cushion plate mounted on upper and lower seat springs, a seat cushion provided on a front side of the cushion plate, an auxiliary plate provided between the seat cushion and the cushion plate for pushing out the seat cushion forward. The cushion plate includes an upper plate located higher than the lower seat spring and a lower plate located lower than the lower seat spring. The lower plate has such elastic force that when the lower plate receives, through the seat back cushion, pressure from a person properly seated on the seat, the lower plate can move backward by a greater distance than the distance of rearward movement of the lower seat spring.

Abstract: It is a subject to provide a chair capable of realizing a condition in which movements of a seating person are preferably followed and a condition in which a back of the seating person can be preferably supported. For this purpose, a chair C comprising a lower frame portion that is supported to be rockable between a standing position and a rearward tilting position of a back frame with respect to the base and an upper frame portion that is supported to be rockable between a normal position and a rear end position, wherein the chair is further comprised with a movement range setting mechanism with which a movement range through the rocking movement of the upper frame portion with respect to the lower frame portion is made changeable in accordance with the position of the lower frame portion with respect to the base during the rocking movement.

Abstract: A therapeutic back support device including a back support portion that automatically and repeatedly moves forward to maintain engagement with a user's back as the user moves forward with respect to a chair seat. The back support portion substantially resists backward motion and provides substantially continuous therapeutic support to the user's spine pending a release signal.

Abstract: A chair has a coupling mechanism between a seat and a back, which includes a joining member, and a coupling member; the seat has two opposite front and two opposite rear ears on a bottom; the joining member is secured on a supporting tube for the seat, and has two opposite sloping slots on each end, and intermediate adjustment slots; the connecting member has a front fixing hole, and a rear sloping slot; the joining member, the connecting member, and the seat are joined together with a first shaft passed through the front ears and the front sloping slots, with a second shaft passed through the rear ears and all of the rear sloping slots; a third shaft is passed through the adjustment slots and the fixing hole; the connecting member is further pivoted to the joining member at a middle portion; the back is joined to the connecting member.

Abstract: A mechanism for an office chair having a backrest support which may be pivoted rearwardly. Adjustment of the backrest pivotal motion is accomplished by the mechanism having a base support which may be positioned on a chair column, a seat support, the backrest support which may be pivoted to the rear, and a pre-tensioned spring arrangement for enabling the mechanism to counter or oppose the movement of the backrest support. The seat support and the base support form a movable unit, which may be moved relative to the chair column depending on the weight of a user applying a load to the seat support. Movement of the movable unit causes an adjustment of the pre-tension of the spring arrangement and/or an adjustment of the spring constant of the spring arrangement.

Abstract: A seat back assembly (16) for a seat (10), comprising an upper seat back portion (24) for supporting an upper portion of a user's back and a lower seat back portion (22) for supporting a user's pelvis and pelvic region. The lower seat back portion (22) and the upper seat back portion (24) are independently adjustable. The upper seat back portion (24) can be reclined to one of a number of fixed angular positions and it is arranged and configured for dynamic angular movement under a load over a range of positions. The dynamic movement of the upper seat back portion (24) is controlled by a shock absorber (44) having adjustable damping means for providing a required level of tension and rebound in relation to the dynamic back action of the upper seat back portion (24).

Abstract: An adjustment mechanism for use with a chair. The adjustment mechanism is for use on a chair that has a base assembly with an extending pedestal, a seat, a chassis, and a back. Specifically the adjustment mechanism is for use on a chair that utilizes a J-back bar that couples the chassis to the back. The J-back adjustment mechanism allows the angle of the J-back bar and thus, the back to be changed throughout a range of motion. The J-back adjustment assembly includes a casing and an adjustment portion, wherein rotation of the adjustment portion changes the inclination of the J-back bar and, thus, the back with respect to the seat.

Abstract: A chair includes a supporting frame and a seat portion which is foldable about a transverse fold to define a rearward portion behind the transverse fold and a forward portion, forward of the transverse fold. The seat portion is supported above the supporting frame by its rearward portion. The chair also includes a reclinable back portion and a recline mechanism with which the back portion is connected for reclining action of the back portion. The recline mechanism is operably linked to the rearward portion of the seat portion such that on reclining action of the back portion, the rearward portion is moved to increase in rearward tilt angle and to obtain a net increase in height above the supporting frame, with a consequent folding of the seat portion about the transverse fold line under the weight of the occupant.

Abstract: A chair according to embodiments of the present invention includes a base; a first linkage pivotably coupled to the base, a seat pivotably coupled to the first linkage, a second linkage pivotably coupled to the seat and pivotably coupled to the base, a back comprising a substantially upright portion and an attachment portion, the attachment portion pivotably coupled to the base at a first pivot point, and a third linkage pivotably coupled to the back at a second pivot point and pivotably coupled to the second linkage, wherein the second pivot point is on the attachment portion between the first pivot point and the substantially upright portion.

Abstract: A vehicle seat includes a pivotable backrest including a counterbalance electric and/or pneumatic drive, a locking/unlocking mechanism and an adjustment mechanism.

Abstract: A seating furniture (1) including a frame (5, 6, 7); at least one support member (2, 3) adapted to provide support to a user in use; recline mechanism (4) connecting the support member (2, 3) to the frame (5, 6, 7), the recline mechanism (4) including; a housing positioned on one of either the support member (2, 3) or the frame (5, 6, 7) and an extending portion (11) of the frame (5, 6, 7) and an extending portion (11) of the frame (5, 6, 7) positioned on the other of either the support member (2, 3) or the frame (5, 6, 7) said housing receiving the extending portion (11) within a cavity (10) bounded by a cavity wall; and biasing means (12) located inside the cavity (10) between at least a portion of the cavity wall and the extending portion (11), wherein tilting movement of the support member (2, 3) causes a rotation between the cavity (10) and the extending portion (11) thereby engaging the extending portion with the biasing means (12), causing said biasing means (12) to generate a restorative reaction bias

Abstract: A tiltable chair including a base, a fulcrum member having a curved support surface, a back support pivotally connected to the base at a pivot axis and pivotable between at least an upright position and a rearward tilt position, and at least one leaf spring having first and second ends, with the first end being restrained by the base. The at least one leaf spring engages the curved support surface of the fulcrum member at a first contact point when the back support is in the upright position and at a second contact point when the back support is in the rearward tilt position, wherein the second contact point is positioned rearwardly on the at least one leaf spring relative to the first contact point. A link member is pivotally connected to the back support at a first pivot location and is pivotally connected to the at least one leaf spring at a second pivot location. The link member defines a vector between the first and second pivot locations and the first pivot location and the pivot axis define a plane.

Abstract: A backpost for use in wooden dining chair. The backpost unit provides reclining movements for a wooden chair of the type having a stationary frame section within which the backpost unit is secured. The backpost unit consists of an interlocking mechanism with minimum components and requires minimum maintenance and provides a solid and reliable reclining mechanism. The chair enables the user to secure an accurate posture of sitting during eating and also enables the user to enjoy a relaxing posture while sitting on the same dining chair.

Abstract: Cushioning device to cushion a backrest with respect to the seat of a chair or suchlike. The device comprises a first supporting element connected to the backrest, a second supporting element connected to the seat and pinned to the first supporting element, and a spring connected both to the first supporting element and to the second supporting element, to allow a reciprocal elastic oscillation, of a determined amplitude, between the backrest, which can oscillate, and the seat, which remain still. In a wall of the first supporting element a lodging seat is provided to lodge, at least partially, the spring in such a manner that the longitudinal axis of the spring is substantially aligned with respect to the first supporting element.

Abstract: A seat assembly (21) including a seat (22), a backrest (23) and a mounting assembly (24) mounting the seat (22) in a near horizontal orientation for movement along an upwardly concaved arcuate seat path having a center of curvature (37) proximate the center of mass (39) of a person seated on the seat, and the mounting assembly (24) further mounting the backrest (23) in a near vertical orientation for movement independently of the seat along a forwardly concaved arcuate path having a center curvature (37) proximate the center of mass (39) of the person. An adjustment assembly (61) is provided for adjusting the radius of curvature of the path of motion of the backrest (23). Also provided are a backrest tilt adjustment assembly (71), an armrest adjustment assembly (90), a seat biasing assembly (110) and a seat motion latching assembly (111). A method of self-adjusting support and alignment of a backrest also is disclosed.

Abstract: A synchrotilt chair mechanism and a chair are provided. The synchrotilt chair mechanism is for use on a chair that has a base assembly with an extending pedestal, a seat and a back. The mechanism includes a chassis that is coupled to the pedestal and a seat plate that is coupled to the chassis and to the chair seat. The seat plate can slide relative to the chassis. The mechanism further includes a back support bar that is coupled on one end to the chassis. The support bar extends upwardly from the chassis. A pair of arm supports are further included that can be coupled to the chair. Each arm support extends upwardly adjacent one side of the chair seat. The mechanism further includes a back bracket having a pair of ends that extend adjacent a side of the chair. Each end is pivotally coupled to the adjacent arm support. The back bracket further includes a guide plate that mounts to the chair back and that has at least one guide slot.

Abstract: A versatile chair having a back assembly, a seat assembly and a leg assembly. Two brackets are formed on the leg assembly and create an axis of rotation for the back assembly and for the seat assembly independent of the back assembly. The back assembly rotates due to a user's weight. The seat assembly is rotated manually. The chair is stackable and nestable with identically structured chairs. A tension system is aligned on an oblique axis to bias the back assembly to an upright position. The tension system is mounted within front legs of the leg assembly.

Abstract: A reclining apparatus is provided between a post and a seat of a chair. The reclining apparatus includes a first joint for attachment to the post, a second joint pivotally connected with the first joint for supporting the seat and a locking device for locking the second joint in one of several reclined positions relative to the casing.

Abstract: The backrest of a chair comprises a frame, a backrest support and a neck support. A membrane is clipped into the frame, and the backrest support is articulated on a tilting mechanism. The frame comprises two side parts and two cross-pieces, the lower cross-piece lying at the height of the user's lumbar vertebra. The frame and the backrest support are interconnected in one piece. The component created as a result is advantageously a plastic injection molding produced by the gas injection technique (GIT) and the plastic is a glass-fiber-reinforced polyarylamide. This overall structure of the backrest provides a high level of sitting comfort by elastic support of the back in all major regions and directions of movement, but at the same time also considerably reduces production, transport and assembly complexity and has an aesthetically impressive, distinctive form.

Abstract: A simple arrangement of a chair allows transformation of the shape of a backrest. The chair has a transformable backrest and a backrest receiving member that supports a bottom end portion of the backrest in a slidable manner toward a certain direction and an operating lever to select and fix a position at which the backrest is slid and the backrest can be transformed in compliance with the position fixed by the operating lever.

Abstract: A chair comprising a support structure bearing a seat and a backrest, in which the backrest comprises a bearing portion and a connecting portion for connection to the support structure, in which the backrest is tiltable rearwards relative to a resting position under a rearwards thrust applied by the user and elastically returns to the resting position when the rearwards thrust ceases. The rearwards tilting of the backrest is formed in part by an elastic detonation of the bearing portion and in part by a displacement of at least a part of the connecting portion relative to the support structure.

Abstract: A chair with a flexible resilient back support structure includes a hollow tubular seat frame, a hollow tubular backrest frame pivotally connected to the seat frame, and a limit stop affixed to the backrest frame or the seat frame adjacent to the pivot points. The limit stop is configured to limit a degree of rotation of the backrest frame between an upright position and a maximum backwardly rotated position. An elongate spring element extends from within the backrest frame into the seat frame, and is configured to bias the backrest frame in the upright position, and to resiliently resist backward rotation. In various embodiments, a cam surface is associated with the spring element, providing an effective fulcrum point which moves rearwardly as the backrest frame reclines, thereby increasing the effective flexural resistance of the spring element during reclining.

Abstract: In order to provide a chair that can support near a pelvis or a lumbar portion of a person who sits on the chair irrespective of a body proportion the person or a way to sit, a boundary portion K between a back and a seat is arranged to be transformable or movable and the boundary portion K can be fixed at a position where the boundary K pushes against near the pelvis of the person with an operation from outside

Abstract: A chair having a chair seat and a chair back includes a means for controlling the tilt of the chair back relative to the chair seat, the tilt means comprising a control body mounted beneath the chair seat and a pivot body pivotably mounted beneath the control body. A spring is operatively disposed between the control body and the pivot body. The control means comprises means for limiting the range of angular motion of the pivot body. Further, the locations of the control body, the pivot body, and the rod about which the pivot body pivots are each optimized to reduce the shear force that is applied to the user's back when the user exerts a force against the chair back.

Abstract: A chair comprises a seat support assembly including a seat support, the seat support assembly being adapted to stand on a surface so as to provide the seat support at a suitable height for a person to sit on, and a back support assembly, including a back frame member and a back support. In one embodiment, the back frame member has a curved middle portion substantially in the plane of the back support, and first and second end portions substantially in the plane of the seat support. The back frame member is flexibly interconnected to the seat support assembly by a first spring flexibly interconnecting the first end portion of the back frame member and the seat support assembly; and a second spring flexibly interconnecting the second end portion of the back frame and the seat support assembly.

Abstract: A tiltable chair including a base, a fulcrum member having a curved support surface, a back support pivotally connected to the base at a pivot axis and pivotable between at least an upright position and a rearward tilt position, and at least one leaf spring having first and second ends, with the first end being restrained by the base. The at least one leaf spring engages the curved support surface of the fulcrum member at a first contact point when the back support is in the upright position and at a second contact point when the back support is in the rearward tilt position, wherein the second contact point is positioned rearwardly on the at least one leaf spring relative to the first contact point. A link member is pivotally connected to the back support at a first pivot location and is pivotally connected to the at least one leaf spring at a second pivot location. The link member defines a vector between the first and second pivot locations and the first pivot location and the pivot axis define a plane.

Abstract: The stylish task chair includes a base with casters, a mounting plate, a seat frame, a back frame, a pair of springs and a seat and backrest. The frames are formed of steel wire of seven-sixteenth inch diameter. The chair is formed by welding the springs to the seat frame and the mounting plate and by welding the back frame to the mounting plate, the back frame being contiguous with the springs. A seat panel is fastener to the seat frame and a backrest panel is mounted to the back frame. Two horizontally disposed steel wires are welded to the back frame and support armrests. The spring allows the rearward portion of the seat to pivot and the cantilevered back frame allows the backrest to flex, these pivoting and flexing movements being independent of each other. The steel wire offers comfort and an airy open look. Seat and backrest cushions may be connected to the panels.

Abstract: A chair with a flexible resilient back support structure includes a hollow tubular seat frame, a hollow tubular backrest frame pivotally connected to the seat frame, and a limit stop affixed to the backrest frame or the seat frame adjacent to the pivot points. The limit stop is configured to limit a degree of rotation of the backrest frame between an upright position and a maximum backwardly rotated position. An elongate spring element extends from within the backrest frame into the seat frame, and is configured to bias the backrest frame in the upright position, and to resiliently resist backward rotation. In various embodiments, a cam surface is associated with the spring element, providing an effective fulcrum point which moves rearwardly as the backrest frame reclines, thereby increasing the effective flexural resistance of the spring element during reclining.

Abstract: A stackable chair includes a base with a pair of inverted U-shaped leg members. Each of the leg members includes a front leg portion, a rear leg portion, and a generally horizontal portion interconnecting the front and rear leg portions. The base also has a generally horizontal seat cushion frame extending between the U-shaped leg members with the transverse front spring reinforcement bar extending side-to-side. A back support frame has a generally vertical portion with an upper and lower end and a generally horizontal end portion that extends from the lower end. The generally horizontal portion includes a transverse rear spring reinforcement bar. A spring member has one end interconnected with the front spring reinforcement bar and another end interconnected with the rear spring reinforcement bar. The spring member supports the back support frame such that the back support frame has an unstressed position and a reclined position.

Abstract: A chair having a swingable chair back with a top pivot includes a frame having laterally spaced first and second uprights. A back having upper and lower ends is attached to the frame. Also attached to the frame adjacent the lower end of the back is a seat. A pivot assembly couples the first and second uprights to the back and permits pivoting of the back about a substantially horizontal pivot axis. The pivot axis projects laterally of the back and is positioned in the vicinity of the upper end of the back. A biasing device cooperates with the back and normally urges the lower portion of the back forwardly away from a rearward position.

Abstract: A chair wherein a backrest frame 5 located rearwardly of a seat frame 4 is divided into a backrest upper frame 55 and a backrest lower frame 50, at least the backrest upper frame 55 being capable of inclining rearwardly, is of a construction that shafts 8 and 71 for rearwardly inclining the backrest upper frame 55 are provided to allow the backrest upper frame 55 to incline rearwardly about one of the shafts 8 and 71. The chair of this construction is made more comfortable to sit.

Abstract: A seat assembly (21) including a seat (22), a backrest (23) and a mounting assembly (24) mounting the seat (22) in a near horizontal orientation for movement along an upwardly concaved arcuate seat path having a center of curvature (37) proximate the center of mass (39) of a person seated on the seat, and the mounting assembly (24) further mounting the backrest (23) in a near vertical orientation for movement independently of the seat along a forwardly concaved arcuate path having a center curvature (37) proximate the center of mass (39) of the person. An adjustment assembly (61) is provided for adjusting the radius of curvature of the path of motion of the backrest (23). Also provided are a backrest tilt adjustment assembly (71), an armrest adjustment assembly (90), a seat biasing assembly (110) and a seat motion latching assembly (111). A method of self-adjusting support and alignment of a backrest also is disclosed.

Abstract: A seating unit includes a seating unit having a base, a seat and a back operably pivoted to the base for synchronous movement including recline of the back and forward movement of the seat, an adjustable variable back stop adjustably engaging the seat for adjustably limiting a rearward tilt of the back, and a handle. The handle and the back stop are supported for independent movement, but are interconnected by a connecting mechanism including a pair of links so that the back stop is selectively adjusted upon rotation of the handle.

Abstract: A theater seat assembly includes a pair of opposed stanchions for attachment to a support surface, a generally horizontal seat portion disposed between and operatively connected to the stanchions, and a generally upright back portion disposed between and operatively connected to the stanchions. The theater seat assembly may include a lounge mechanism operatively connected to the back portion and the stanchions to allow the back portion to lounge rearward relative to the stanchion. The theater seat assembly may also include a cushion suspension system operatively connected to the seat portion and the stanchions to allow the seat portion to deflect downwardly relative to the stanchions. The theater seat assembly may further include each one of the seat portion and the back portion having a frame, a cushion disposed adjacent the frame and a trim cover covering the cushion and attached to the frame.

Abstract: A chair that can transform a shape of a backrest with a simple arrangement is provided.

Abstract: A task chair including a seat support structure, a backrest frame attached to the seat support structure, and a backrest supported by the backrest frame. The backrest includes a back support surface which may ergonomically conform to a seated user when the user shifts positions while sitting in the chair. The back support surface includes rigid and flexible portions connected to one another, the flexible portions allowing resilient flexing of the back support surface to create conformance zones which dynamically support the back of a seated user in an ergonomic manner.

Abstract: A chair control providing both articulating tilt motion and dual-ratio, adjustable, synchronized tilt motion. In a first aspect, the control can be configured as either an articulating tilt control or a synchronized tilt control. In a second aspect, the angle between the seat and the backrest may be selected by the user when the control is configured for either the articulating mode or the synchronized mode. In a third aspect, when in the synchronized mode, the angle between the seat and the backrest increases during forward tilt action to avoid “clam shelling.” In a fourth aspect, a forward tilt selector enables or prohibits forward tilting of the control.

Abstract: A chair has both a tiltable seat and a tiltable backrest mounted on a backrest support. The chair includes a pedestal mounted on a bottom of the tiltable seat. An eccentric disk is seated in the pedestal so as to be movable therein. A rod eccentrically penetrates the eccentric disk via a prismatically-shaped cross-section recess through the eccentric disk so that the rod is not movable with respect to the eccentric disk. A handle is connected on an outer end of the rod for use in turning the rod together with the eccentric disk. An arm is mounted on the backrest support of the tiltable backrest, wherein the rod is seated in the arm in a movable manner.

Abstract: In a chair 1 having an upholstery member 7 fitted on a backrest portion or seat plate 4 serving as a portion adapted to contact a human body, upright portions 41 and elastic pieces 8 allowing their deflection in the direction in which the load of a human body contacting the chair works are provided and the upholstery member 7 is placed over the upright portions 41 and elastic pieces 8 so that the contacting portion of the seat portion or backrest portion is imparted with elasticity to ensure a better sitting comfort even if the upholstery member 7 lacks elasticity.

Abstract: A chair of modular construction having modules that form the basic chair with additional modules that can be added to the chair without changing the basic construction thereof.

Abstract: An upper back support in a vehicle seat, with the vehicle seat having a base assembly including a seat support. The seat member is supported on the base assembly and a back frame is pivoted to the base assembly for movement. A back shell is connected to the back frame and an upper back support is coupled to the back shell. The upper back support comprises a panel having a lower portion and an upper portion, with the lower portion flexibly coupled to the back shell of the vehicle seat. A resilient member is coupled to the panel proximate the upper portion and to the back shell of the vehicle seat. An additional resilient member can be coupled to the panel proximate the upper portion and to the back shell of the vehicle seat in a spaced apart relationship to the other resilient member.

Abstract: A stackable chair includes a base with a pair of inverted U-shaped leg members. Each of the leg members includes a front leg portion, a rear leg portion, and a generally horizontal portion interconnecting the front and rear leg portions. The base also has a generally horizontal seat cushion frame extending between the U-shaped leg members with the transverse front spring reinforcement bar extending side-to-side. A back support frame has a generally vertical portion with an upper and lower end and a generally horizontal end portion that extends from the lower end. The generally horizontal portion includes a transverse rear spring reinforcement bar. A spring member has one end interconnected with the front spring reinforcement bar and another end interconnected with the rear spring reinforcement bar. The spring member supports the back support frame such that the back support frame has an unstressed position and a reclined position.

Abstract: A chair has a seat (4) and a backrest (5) which are independently pivotable within limits at extremities. The seat is biassed upwardly at the front and the backrest is biassed forwardly. The seat and the backrest have a common pivot joint (8), under the center of gravity of the occupant. There are no occupant-operated controls as the chair responds automatically to the posture of the occupant, providing full support at all relative positions of the seat and the backrest in a balanced manner for occupants of a wide range of weights.

Abstract: A stackable chair includes a base with a pair of inverted U-shaped leg members. Each of the leg members includes a front leg portion, a rear leg portion, and a generally horizontal portion interconnecting the front and rear leg portions. The base also has a generally horizontal seat cushion frame extending between the U-shaped leg members with the transverse front spring reinforcement bar extending side-to-side. A back support frame has a generally vertical portion with an upper and lower end and a generally horizontal portion that extends from the lower end. The generally horizontal portion includes a transverse rear spring reinforcement bar. A spring member has one end interconnected with the front spring reinforcement bar and another end interconnected with the rear spring reinforcement bar. The spring member supports the back support frame such that the back support frame has an unstressed position and a reclined position.