Abstract: A back construction includes an inverted U-shaped back frame and a back shell supported on the back frame and having stiff thoracic and pelvic regions connected by a flexible lumbar region in a manner adapted to ergonomically support a seated user. The lumber section includes a plurality of vertically spaced slots to increase its flexibility. The back shell has a complex curved shape that is forwardly concave in horizontal cross section and forwardly convex in vertical cross section. A force-generating mechanism biases the lumber section forwardly for lumbar support to a seated user.

Abstract: A tiltable chair including a housing, a back support pivotally attached to the housing about a first horizontal axis and a seat support pivotally attached to the housing about a second horizontal axis. A leaf spring includes a first end engaging the housing and a second end biasing the back support and seat support in an upward direction. A fulcrum member is moveably supported in the housing and engages a bottom surface of the spring intermediate the first and second ends of the spring.

Abstract: A rocking chair has a flexible joint between a chair base and a chair component permitting rocking action. The flexible joint includes a housing with a plurality of internal surfaces. A plurality of compressible rods are disposed within the housing and a rigid member extends among the rods to engage the rods against the internal surfaces of the housing. The rigid member is attached to either the chair base or the chair component while the housing is then attached to either the chair base or the chair component whichever is not attached to the rigid member.

Abstract: A chair with backward and forward passive tilt capabilities including a seat assembly, a back assembly, a frame assembly, a wheeled base, a pedestal and a tilt mechanism. The tilt mechanism includes first, second and third links, first, second, third and fourth pivot pins, brackets and a resilient deformable block. The first link connects the back assembly with the frame assembly by way of the first pivot pin and the seat assembly by way of the second pivot pin. The second link connects to the frame assembly with the third pivot pin and to the third link with the fourth pivot pin. When a chair occupant shifts his/her weight rearwardly to tilt the back assembly, the seat assembly lifts and the block is deformed and stressed. When the chair occupant leans forwardly, the seat assembly lowers and the back assembly tilts forwardly. Again, the block deforms. Once the occupant sits upright or leaves the chair, the deformed block induces a return force to place the chair in a neutral upright position.

Abstract: A chair includes a control housing, a seat and a back support including an upwardly extending upright portion and a link portion extending forwardly from a lower portion of the upright portion. The link portion is pivotally connected to the control housing about a first pivot axis. The seat is connected to the link portion and is pivotable relative thereto. A linkage is coupled to the seat and is pivotally connected to the control housing at a second pivot axis positioned rearwardly and downwardly from the first pivot axis.

Abstract: A chair back is supported on a rigid upright coupled to a horizontal tilt shaft disposed under the front of the chair seat and supported on a control housing fixed to a pedestal. A tension mechanism urges the upright into an upright position. The chair seat is movably supported on the upright by an arrangement which permits the seat to pivot about a transverse horizontal axis positioned adjacent the upper surface of the seat. A control link is pivoted at one end to the control housing, and the other end has lost-motion pivotal connections to the seat frame and the upright. The lost-motion pivotal connection to the seat frame including a spring cooperating between the upright and the seat frame to allow the seat to move relative to the upright.

Abstract: A chair having a synchronously moving seat bottom and seat back includes a frame having a seat bottom support portion and a seatback support portion and a seat assembly having a seat bottom and a seat back interconnected by a flexible intermediate portion. The seat bottom is slidably mounted to side support members in the bottom frame providing forward and aft movement of the seat bottom. The seat back is pivotably engaged to the seat back support portion of the frame. The flexible intermediate portion provides for cooperative movement of the seat bottom and seat back between an upright seating position and a reclined position. Preferably, the seat assembly is a one piece molded plastic shell having a flexible intermediate portion interconnecting the seat bottom and seat back. In one embodiment of the invention, the chair can be provided with legs to enable stacking of the chairs.

Abstract: A seating unit includes a base, a seat, a back, and a control operably supporting the seat and the back on the base for movement between upright and recline positions. The control includes a spring providing a biasing supporting force to the back during recline, and further includes a booster mechanism for increasing the supporting force, and still further includes a stop member and a selector device for activating and deactivating the booster mechanism. The selector device is easily movable with a low effort that is independent from friction generated by internal components of the booster mechanism. The stop member is linearly slidably mounted atop a control housing for selectively engaging the booster mechanism and the link for movement between a disengaged position, a booster-engaged position, a partial-recline position, and a recline-prevented position.

Abstract: A chair, in particular an office chair, comprising: a base structure, a seat support structure, articulated to the base structure around a transverse axis, an adjustable elastic device to apply an elastic force between the base structure and the seat support structure, a manually operated adjustment device for varying the distance between said adjustable elastic device and said transverse axis.

Abstract: The chair, particularly an office chair, has a backrest articulated to a seat support by way of a rest support. A seat surface is movable synchronously with the backrest. A front region of the seat surface is connected to the seat support via a sliding guide and a rear region is connected to the seat support via a seat link. A distance from an upper pivot point, which connects the seat link to the seat surface, to the backrest is shorter than the distance from a lower pivot point, which connects the seat link to the seat support, to the backrest. The movements of the backrest and of the seat surface are synchronized by a sliding guide provided between the seat link and the rest support.

Abstract: A synchronizing mechanism for correlated seat/backrest motion of an office chair is provided with a base carrier to be placed on a chair column; a seat carrier, which is pivotable about a transverse axis and, at its front end, articulated to the base carrier; and a backrest carrier, which is also pivotable about a transverse axis and articulated to the base carrier. It is coupled with the seat carrier such that a backward pivoting motion of the backrest induces a lowering motion of the rear end of the seat carrier. The joint between the base carrier and the seat carrier is a turning and sliding joint so that the lowering motion of the seat carrier is combined with a horizontal sliding motion.

Abstract: This object is attained in a chair comprising a pedestal; a seat support supported thereon via a chair column, said seat support comprising a front and a rear seat support element being connected with one another via a pivot axis extending substantially horizontally; a seat supported on said seat support elements; a backrest secured on said rear seat support element; a longitudinally adjustable energy storing means for mutually adjusting said backrest and said seat, said energy storing means being joined with said seat support elements at a distance from their pivot axis; a spring abutment being arranged pivotably around said pivot axis for adjustably dampening a pivoting movement of said seat support elements relative to one another; an adjusting element extending substantially tangentially relative to said pivot axis and being pivotable around an adjusting element pivot axis for modifying the bias between said spring abutment and one seat support element; and an actuating twist handle connected with said ad

Abstract: A chair has a seat connected to a support leg in an up and down angularly displaceable manner, elastic elements for propping up a rear end of the seat to a higher position, and a mechanism for limiting position of the seat when the seat seats people; the mechanism has an adjustment rod, a gear turnable together with the adjustment rod, an elastic plate for engaging the gear so as to prevent rotation of the gear when the adjustment rod isn't operated, and eccentric cams for holding the seat at desired position when the chair seats people; the cams can turn together with the adjustment rod, and are each formed with a stopping edge having several sections; thus, the depressed position of the seat, i.e. the position when the seat seats people, is decided by the position of the cams, and the seat can move accordingly when the sitter leans forwards.

Abstract: A seating unit includes a base, a seat, a back, and a control operably supporting the seat and the back on the base for movement between upright and recline positions. The control includes a spring providing a biasing supporting force to the back during recline, and further includes a booster mechanism capable of increasing the supporting force, and still further includes a selector device for activating and deactivating the booster mechanism. The selector device is easily moveable with a low effort that is separated from and independent from any friction generated by internal components of the booster mechanism. In a narrower aspect, the control is powered, such as by an electrical or electromechanical device from a remote location. A back stop is attached to the selector device, for movement between a disengaged position, a partial-recline position, and a recline-prevented position.

Abstract: An office-type chair which provides for synchronous differential tilting of the seat and back assemblies, with the seat assembly being constructed such that the front lip thereof does not significantly lift upon rearward tilting. The chair incorporates a tilt control mechanism formed by a control body which secures to the upper end of the chair pedestal and an upright which pivotally connects to the control body about an axis disposed forwardly of the pedestal. A pivot assembly connects the upright and control body together.

Abstract: An articulated seating mechanism including a rocker base, a seat plate, and a pair of side rails, each having an arcuate side. The side rails may be disposed downwardly from the seat plate or upwardly from the rocker base. First and second arcuate gear portions are disposed on the arcuate side of each of the side rails and a first and second substantially flat or linear gear racks are affixed either to the underside of the seat plate or the upper side of the rocker base, so as to bring the linear gears and the arcuate gears into intermeshing relationship. A back support is pivotally connected to the seat plate and to first and second back links, and the back links are pivotally connected to the rocker base to provide a rocking motion of the seat plate and a dynamic synchronous adjustment of the angular variation between the seat plate and the back support. The linear gear racks move in a tangent to the arcuate gear portions to provide a moving fulcrum during rocking movements.

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 chair includes a control housing, a seat and a back support including an upwardly extending upright portion and a link portion extending forwardly from a lower portion of the upright portion. The link portion is pivotally connected to the control housing about a first pivot axis. The seat is connected to the link portion and is pivotable relative thereto. A linkage is coupled to the seat and is pivotally connected to the control housing at a second pivot axis positioned rearwardly and downwardly from the first pivot axis.

Abstract: An adjustable armrest for a chair includes a housing having a cavity defined by a wall and a latch member slideably mounted in the cavity. The latch member includes a wedge shaped portion having a first and second surface forming a oblique angle between them. One of the first and second surfaces engages the wall of the housing at least when the latch is in the engaged position.

Abstract: The invention relates to seat and backrest arrangements in seat furniture, in particular office chairs, which comprise a seat plate, a seat-plate support and a backrest support and in which the seat plate (1), in the region of its front, knee-side edge (2), is connected moveably to the seat-plate support (3) and, in the region of its rear edge (5), is connected moveably to the backrest support (6), the backrest support (6) being coupled displaceably to the seat-plate support (3). The seat and backrest arrangements according to the invention are characterized in that a spring means (4) for cushioning the seat plate (1) and the backrest support (6) is arranged in the region of the front, knee-side edge (2) of the seat plate (1)—between the seat plate (1) and seat-plate support (3).

Abstract: A seating structure includes a support structure, a seat supported by the support structure and a backrest pivotally connected to the support structure. The seat includes a front and rear. The backrest is positioned adjacent the rear of the seat. The backrest includes a frame having a pair of bow-shaped side members. Each of the side members has a lower section and an upper section. The upper sections extend from the lower sections so as to form a pair of first bowed sections at substantially a lumbar region of the backrest. A flexible membrane is attached to and extends between the side members. The flexible membrane has a second bowed section corresponding to the first bowed sections of the side members. A method of using the seating structure is also provided.

Abstract: A chair having a synchronously moving seat bottom and seat back includes a frame having a seat bottom support portion and a seatback support portion and a seat assembly having a seat bottom and a seat back interconnected by a flexible intermediate portion. The seat bottom is slidably mounted to side support members in the bottom frame providing forward and aft movement of the seat bottom. The seat back is pivotably engaged to the seat back support portion of the frame. The flexible intermediate portion provides for cooperative movement of the seat bottom and seat back between an upright seating position and a reclined position. Preferably, the seat assembly is a one piece molded plastic shell having a flexible intermediate portion interconnecting the seat bottom and seat back. In one embodiment of the invention, the chair can be provided with legs to enable stacking of the chairs.

Abstract: A chair, in particular an office chair, is described. The chair has a backrest that is inclinable with regards to a seat carrier via a backrest carrier. The chair has a seat surface that can be moved synchronously with the backrest and is supported on the seat carrier via at least one seat link. A coupling link is provided for synchronization between the movement of the backrest and the movement of the seat surface. The coupling link is connected rotatably, on one side to the seat surface and, on another side, to the backrest link.

Abstract: A chair of the tilting type which includes a base, a seat and back, with the base pivotally supporting the seat with two parallel links of a four-bar parallel linkage, with one of the links extending to support the back. The four-bar linkage is duplicated on each side of the chair by forming the two opposite parallel links or cranks from the upturned ends of the tubes which pass through the base in parallel but vertically offset fashion, the base thus forming the fixed bar of the linkage with its opposite bar or coupler being formed by the seat. A spring within the base is operative on one (of both) of the tubes to urge the chair to an upright position. The tubes are pivotally connected to the seat and one of the tubes extends and is fixedly connected to the back. As the back tilts, the four-bar mechanism is engaged and lifts the seat which thereby uses the occupant's weight to counteract the reclining.

Abstract: A forward end part of an arm part (53) of a seatback frame is connected to a forward end part of a main frame (3) such that the forward end part of said arm part (53) can turn about a horizontal axis (61) extending leftward and rightward. A cam hole (71) is formed in a forward end part of the arm part (53). A shaft part (72) movably engageable with the cam hole (71) through a roller (73) is disposed at a forward end part of a seat frame (41). The cam hole (71), the shaft part (72) and the roller (73) constitute a positive motion mechanism (70) for causing a seat frame (41) to be tilted in accordance with the turning motion of the arm part (53).

Abstract: A chair, in particular a work or office chair, having a seat mounted onto a chair frame. The front region of the seat can be inclined about a horizontal, pivoting shaft which is displaced upwards and downwards, following a spatial guide curve in relation to the chair frame. The seat is also connected in an articulated manner to a rocker which is directed upwards and extends backwards from an articulated rocker bearing fixed to the chair frame and which is connected at a distance from the rear edge of the seat, or at the side of said seat. The chair also includes a backrest which is attached to the section of the rocker that is directed upwards, the inclination of the backrest being disproportionately altered, in a forced manner, with the alteration of the inclination of the seat.

Abstract: A chair, in particular an office chair, has a backrest that is articulated on a seat carrier via a backrest carrier, and has a seat surface that can be moved synchronously with the backrest. The front region of the seat surface is connected to the seat carrier via a sliding guide. The rear region of the seat surface is connected to the seat carrier via a seat link. A top point of rotation connects the seat link to the seat surface. A bottom point of rotation connects the seat link to the seat carrier. The distance between the top point of rotation and the backrest is smaller than the distance between the bottom point of rotation and the backrest. A sliding guide for the seat surface is provided in the backrest carrier for synchronizing the movement of the backrest and the movement of the seat surface.

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 chair includes a base having an adjustable column, a seat, and a back. An underseat assembly operably supports the seat and the back on the base. The underseat assembly includes a metal bottom support with a tapered socket shaped to engage the column, and includes a seat-supporting yoke constructed with a center section shaped to vertically engage the bottom support. Opposing side support sections include inwardly facing mounting sections that mateably engage a top of the center section. A retainer plate clamps the bottom support, yoke, and side support sections together. A link is operably attached to the side support sections and the back for supporting the back. The seat, the back, and underseat components are constructed for top down assembly without requiring that the chair be inverted during assembly, and they form a four-bar linkage with the link that supports synchronous movement of the seat and back.

Abstract: An ergonomic chair includes a four-bar linkage arrangement wherein a lower frame member is provided with a rigid front support and a rigid rear support with a seat member pivotably connected to the front support. A back rest has an upper support pivotably connected at an upper end of the rear support of the lower frame member. A link member pivotably connects at a first end to a rear support of the seat member and at second end to a lower support of the back rest. This novel arrangement permits tilting movement of the backrest rearwardly relative to the lower frame member causing elevation of a rear portion of the seat member, permitting the feet to remain on the floor and alleviating pressure on the user's thighs, while rotation occurs closely coincident with the pivot axis of the user's hips and while maintaining a generally uniform gaze line.

Abstract: A synchrotilt mechanism for a chair to provide improved control over the relative but synchronized tilting of the back and seat during tilting. The chair back is supported on a rigid upright assembly including lower lever arms which project under the chair seat and are coupled at forward ends to a horizontal tilt shaft which is disposed under the front of the chair seat and is supported on a control housing fixed to the upper end of the base pedestal. A tension control mechanism is coupled between the tilt shaft and the control housing for normally urging the upright arrangement, and the chair back, into an upright position. The chair seat is movably supported on the lower lever arms by a support arrangement which permits the chair seat to pivot relative to the upright assembly about a generally transverse horizontal axis which is preferably slightly below the upper surface of the seat when the latter is in a nondeformed condition, i.e., the seat is not occupied.

Abstract: A seating unit is provided having a base, a back frame pivoted to the base for movement between upright and reclined positions, and a seat slidably supported on the base assembly and pivoted to the back frame so that the seat moves forwardly and its rear moves forwardly and downwardly with the back frame upon recline. A flexible back shell is connected to the back frame at top and bottom locations for controlled flexure when a seated user reclines and/or flexes his/her back, and is provided with lumbar adjustment for improved lumbar force/support and shape.

Abstract: An ergonomic chair includes a four-bar linkage arrangement wherein a lower frame member is provided with a rigid front support and a rigid rear support with a seat member pivotably connected to the front support. A back rest has an upper support pivotably connected at an upper end of the rear support of the lower frame member. A link member pivotably connects at a first end to a rear support of the seat member and at second end to a lower support of the back rest. This novel arrangement permits tilting movement of the backrest rearwardly relative to the lower frame member causing elevation of a rear portion of the seat member, permitting the feet to remain on the floor and alleviating pressure on the user's thighs.

Abstract: A reclining leisure chair includes a base frame, a seat frame, a backrest frame, a hassock frame, a driving device, and a link rod. The driving device enables the seat frame and the backrest frame to be adjusted for reclining at the same time. The link rod is pivotally fastened at one end to the backrest frame, and at the other end with a pivoting portion of the seat frame. In conjunction with a control rod of the seat frame, the link rod enables the backrest frame to be adjusted for reclining independently. The hassock frame is pivoted with the link rod.

Abstract: The chair includes seat and back assemblies interconnected in a four-bar linkage. The chair further includes a tension mechanism comprising a coil spring projecting forwardly from a base and an adjustment linkage which is connected to said coil spring and to a front link of said four-bar linkage. A back linkage end of said adjustment linkage being axially movable along an axis of said coil spring and a front linkage end being vertically movable along said front link to adjust displacement of said adjustment linkage during rearward pivoting of said front link.

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: An office-type chair which provides for synchronous differential tilting of the seat and back assemblies, with the seat assembly being constructed such that the front lip thereof does not significantly lift upon rearward tilting. The chair incorporates a tilt control mechanism formed by a control body which secures to the upper end of the chair pedestal and an upright which pivotally connects to the control body about an axis disposed forwardly of the pedestal. A pivot assembly connects the upright and control body together.

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 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: The adjustment mechanism contains a pneumatic spring that is placed vertically in the underframe, for adjusting height, and a pneumatic spring that is linked to the seat support at one end and the back-rest at the other, for synchronized adjustment of the angle. The pivotable back-rest and the fixed seat support are coupled with each other on the main rotational axis in two hinge connections. The main rotational axis runs above and crosswise over the seat plate. The seat plate has guide cranks on its underside, the supporting arms of the seat support engaging is said guide cranks in such a way that they can slide crosswise to the main rotational axis. The front bearing pegs of the supporting arms engage in the guide cranks. The seat plate is coupled together with the inclination spring on the moving rotational axis on the back-rest. The invention also relates to a back cover with a variably positionable lumbar reinforcement insert and height-adjustable armrests.

Abstract: A chair is provided having a seat with a resiliently deflectable shell defining a front portion thereof. The front shell is deflectable downwardly in response to the user. An adjustment mechanism is provided which controls the deflected position of the front shell section to provide for controlled deflection of the seat which adjusts the effected length of the seat while also providing for user responsive deflection of the seat.

Abstract: The invention relates to seat and backrest arrangements in seat furniture, in particular office chairs, which comprise a seat plate, a seat-plate support and a backrest support and in which the seat plate (1), in the region of its front, knee-side edge (2), is connected moveably to the seat-plate support (3) and, in the region of its rear edge (5), is connected moveably to the backrest support (6), the backrest support (6) being coupled displaceably to the seat-plate support (3). The seat and backrest arrangements according to the invention are characterized in that a spring means (4) for cushioning the seat plate (1) and the backrest support (6) is arranged in the region of the front, knee-side edge (2) of the seat plate (1)—between the seat plate (1) and seat-plate support (3).

Abstract: A chair includes an actuator having an actuator button disposed on top, a base secured on the actuator, a spring engaged in the base and having an actuator arm engaged on the actuator button for actuating the actuator button to release the actuator. A barrel is rotatably secured to the base. A bar is pivotally and adjustably secured to the base and adjustable relative to the base at any selected angular position. A latch is slidably engaged in the base and selectively engaged with the bar for adjustably securing the bar and the seat cushion to the base.

Abstract: A seating structure having a fabric with a weave pattern for supporting the body of a user. The fabric includes a plurality of strands of multifilament yarn and a plurality of monofilaments running generally perpendicular to the strands. At least some of the monofilaments are arranged in pairs. The monofilaments in each pair weaving alternatively above and below some adjacent strands and crossing over each other between other adjacent strands.

Abstract: A seating structure includes a backrest having a top and bottom and includes a frame. The frame includes a pair of spaced apart side members defining an opening therebetween. Each of the side members has a length. A flexible membrane extends between and is attached to the side members across the opening. An armrest is moveably mounted to each of the side members. Each of the armrests is adjustably moveable along at least a portion of the length of the side members between at least a first position and a second position. The first position is closer to the bottom of the backrest than the second position. A method of adjusting the seating structure is also provided.

Abstract: A chair (1, 1′), in particular an office chair, having a backrest (6) which is arranged such that it can be rotated about a first point of rotation (8) in relation to a seat carrier (2) and which can be inclined from a rest position, and having a seat surface (10) which is connected to the backrest (6) such that it can be rotated about a second point of rotation (12) and which can be inclined synchronously with the backrest, is intended, in particular in terms of its tendency to tilt, also to be suitable for a particularly pronounced inclination movement of the backrest (6) with an inclination of, for example, up to 40° in relation to the starting position of the same. For this purpose, according to the invention, in the rest position, the first point of rotation (8) is positioned at approximately the same height as, or higher than, the second point of rotation (12).

Abstract: An ergonomic chair includes a four-bar linkage arrangement wherein a lower frame member is provided with a rigid front support and a rigid rear support with a seat member pivotably connected to the front support. A back rest has an upper support pivotably connected at an upper end of the rear support of the lower frame member. A link member pivotably connects at a first end to a rear support of the seat member and at second end to a lower support of the back rest. This novel arrangement permits tilting movement of the backrest rearwardly relative to the lower frame member causing elevation of a rear portion of the seat member, permitting the feet to remain on the floor and alleviating pressure on the user's thighs.

Abstract: A chair with variable pitch having a frame set to rest on the floor, at least one central element that creates a substantially horizontal longitudinal axis supported by the frame, a seat supported by the central element, one pair of first stiles parallel to each other and set at the ends of the central element, and a backrest that has its top connected to the first stiles through first flexible couplings and its bottom connected to the seat through a second flexible coupling. The seat is connected to the central element through swivel means that allow the planar rotary-transverse movement of the seat, combined with a rotary rocking movement of the backrest around a longitudinal axis created by the flexible couplings.

Abstract: A preloaded spring arrangement, in particular for spring loading office chair synchronizing mechanisms, comprises a pair of leg springs, which are coaxially positioned on a common axis, each having a supporting leg and a positioning leg; and a preferably manually operated adjusting unit of the type of an eccentric, which the two positioning legs are coupled with and by which they are displaceable for adjustment of the preload of the spring arrangement; wherein, for stepwise locked spring load adjustment, the adjusting unit of the type of an eccentric comprises a pair of eccentric cams sitting axially side by side, the cam surfaces of which, related to the direction of rotation of the eccentric arrangement, successively comprise plane locking sections, eccentric cam control sections and holding sections that are concentric of the axis of rotation of the eccentric arrangement; and wherein the respective locking, cam control and holding sections of the two eccentric cams are offset in the direction of rotation o

Abstract: The chair, particularly an office chair, has a backrest articulated to a seat support by way of a rest support. A seat surface is movable synchronously with the backrest. A front region of the seat surface is connected to the seat support via a sliding guide and a rear region is connected to the seat support via a seat link. A distance from an upper pivot point, which connects the seat link to the seat surface, to the backrest is shorter than the distance from a lower pivot point, which connects the seat link to the seat support, to the backrest. The movements of the backrest and of the seat surface are synchronized by a sliding guide provided between the seat link and the rest support.