BACK REST ARRANGEMENT

Abstract

The invention relates to a back rest arrangement, in particular for an office chair, comprising a deformable back rest extending in vertical (H) and transverse direction (Q) comprising a lordosis support region that can be adjusted in terms of height and curvature, wherein an adjustment device for adjusting the height and the curvature of the lordosis support region is arranged on the back rest support arm in an adjustable manner in terms of height and wherein the adjustment device is connected to the back rest on fastening arms protruding in the transverse direction (Q) by means of bearings comprising counter bearings on the back rest side.

Description

The invention relates to a backrest arrangement according to the features of claim 1. More particularly, the invention relates to a backrest arrangement comprising a backrest in which the height and curvature of the lordosis support region can be adapted.

The natural, forward curvature of the human spine in the region of the lumbar vertebrae, which is comprised of the five vertebrae of the lumbar segment of the spine, is referred to by doctors as the lordosis. Lumbar supports and lordosis supports are used in car seats, slatted frames of beds, and chairs. Particularly during many hours of seated office work, the muscles can relax as a result of fatigue and the spine can slump. Office chair makers therefore offer adaptable lordosis supports which allow for a relaxed posture and allow the spinal column to be relieved of pressure. The prior art mentions backrests, in a simple design, having a bulge acting as a simple support. In particular with seats such as office chairs, however, there exists the need to provide a lordosis support which is adaptable in terms of height and curvature. EP 1 566120 A1, for example, already discloses an office chair comprising a backrest, the backrest having superposed supporting ribs which extend transversely and act as a simple support. Said ribs bulge in a flexurally elastic manner and thus assume the function of a lordosis support. A pull rope mechanism is also provided for adapting the curvature of the lordosis support.

DE 10 2004 035647 B4 discloses a height-adjustable lordosis support. This document proposes an office chair comprising a backrest and a height-adjustable lordosis support arranged on a flexible guide strip, the guide strip being flexible in such a way as to yield in the direction of the pressure when loaded by a seated person or a chair user. The guide strip is biased in the process and the bias of the guide strip can be varied further. A disadvantage of this embodiment is that the backrest does not provide sufficient support in its lateral support regions by means of the lordosis support, and in addition, a load is provided in the central region of the backrest that is predominantly punctiform, thereby generating a local pressure region around the lumbar vertebrae. Furthermore, with increasing curvature the spring force is also automatically increased by the actuation of the flexible guide strip and thus the resilience is reduced, the result being that an adapted sharp curvature is always associated with high spring loading by the guide strip.

DE 20 2005 019654 U1 discloses an office chair comprising a backrest, in which the curvature of the backrest can be adapted. A drawback of this embodiment is that the curvature regions are determined depending on the arrangement of two transverse recesses. In addition, the seat user is likewise not sufficiently supported in the lateral outer regions of the backrest shell carrier. Instead, weakening in the lumbar support region occurs, and this should be avoided. The object of the invention is therefore to provide an improved backrest arrangement comprising an adaptable lordosis support region which is adaptable in as simple a manner as possible and adaptable in each individual case to the shape of the back of the seated person, it being necessary for the backrest arrangement to be formed such that the seat user is provided with an overall sturdy backrest that supports the back.

This object is achieved by a backrest arrangement according to claim 1. Here, the basic concept of the present invention is to provide a backrest arrangement, in particular for an office chair, which comprises a deformable, preferably elastically deformable, backrest which extends in the vertical direction H and transverse direction Q and is provided with a lordosis support which is adaptable in the vertical direction H and in terms of curvature. According to the invention, a backrest supporting arm is provided, on which the backrest is connected to the backrest supporting arm by an upper fastening element, and an adjustment device further being provided on the backrest supporting arm, which device is adjustable in the vertical direction H such that, when the adjustment device is adjusted, the height and curvature of the lordosis support region can be changed. The backrest advantageously has an elastically deformable backrest pad. The backrest pad is advantageously arranged inside the backrest or in part inside the backrest.

The principle of the present invention is thus that there is provided, on the one hand, a backrest which is made of a flexibly deformable material and preferably comprises a elastically deformable backrest pad, which is fastened at its upper edge to a backrest supporting arm and which bulges forwards when the lower edge of the backrest is displaced upwards, whereby the curvature and position of the front point of curvature can be adapted. The user is thus provided with a back support that they themselves can select and that is comfortable for them.

The extent to which the backrest is deformed and thus the lordosis support is curved depends on how far the lower edge of the backrest is actuated upwards by means of an adjustment device. The selection of an elastically deformable material for the backrest makes it possible to adapt said backrest to the overall contour of the back. Inside, the backrest preferably comprises an elastically deformable backrest pad. The resilience of the backrest pad thus makes it possible to adapt the backrest, which is overall resilient, to the natural shape of the spine. As soon as a seat user leans against the bulging lordosis support region when seated on the chair, the backrest and the backrest pad adapt to the natural shape of the spine as a result of the resilience. This provides another advantage of the backrest arrangement according to the invention, since even people having differently shaped spines can use the chair in the same way, without it being necessary to adapt said chair in each individual case to the respective spine curvature of the seat user.

The degree of convexity and the resilience (ability to adapt) of the deformable backrest can be manipulated even further by recesses, in particular horizontal slots in the backrest pad. By arranging slots in different regions and in different shapes, it is also possible to adapt the resilience of the backrest to the demands in the different backrest regions.

Preferably, the adjustment device has lateral fastening arms which project in the transverse direction Q and are connected to the backrest by means of bearings which are provided thereon and which comprise counter-bearings on the backrest side (also referred to hereinafter as bearings), so that, when the adjustment device is displaced in the vertical direction H (i.e. vertically), the position and thus also the height of the lordosis support region can be varied therewith, and the curvature of the lordosis support region can also be adapted at the same time.

By fastening the backrest to the outwardly protruding fastening arms of the adjustment device, the backrest overall is given lateral support, in which the pressure from the upper body of the seat user can be transmitted to the entire backrest and the backrest adequately stabilises the back. Consequently, a stabilising transverse bar fulfils a particularly good support function in the lordosis support region. As a result, this ensures the seat user sits in a comfortable and fatigue-free manner, in which the loads that occur are distributed uniformly over a wide region in the transverse direction of the backrest, while the lumbar vertebrae are supported effectively at the same time.

Advantageously, the upper corner regions of the backrest pad and thus the upper corners of the backrest are not fastened to the backrest supporting arm or to a transverse arm. As a result, when the upper body is rotated, for example when the seat user reaches for an object behind the chair, the corner regions of the backrest and backrest pad are elastically twisted so as to thus adapt to the twisting angle of the upper body.

Preferably, the fastening arms of the adjustment device extend transversely over the entire width of the backrest, and are most preferably fastened to the outer edge region of the backrest. As a result of the lateral suspension of the backrest in the edge region on the adjustment device, a cantilever principle is used, in which a particularly preferable deformation of the backrest is provided so that, when loaded, the backrest behaves according to the above-mentioned cantilever principle.

In an advantageous embodiment of the present invention, the adjustment device comprises a catch device which is movable back and forth from a catch position into an adjustment position. The movable catch device is actuable from the catch position into the adjustment position by means of an actuating arm, whereby the height of the adjustment device can be adapted. The actuation can take place along sliding bearings provided therefor. This ensures that the desired height and curvature of the lordosis support region is adapted by displacing the adjustment device and that this position can be fixed for the seat user by means of the actuating arm, in that the catch device is released and locked in this position.

In a preferred embodiment, the adjustment device comprises a bearing bracket having a slide bearing, the bearing bracket being connected to the holder arms with the formation of an opening. The backrest supporting arm is guided, by its slide bearing portion, through the opening. This achieves a backrest arrangement which is particularly rotation-resistant, since a large contact surface and, at the same time, a surface acting as a bearing are provided between the components involved. Advantageously, the bearing bracket, the backrest supporting arm and an inner surface of the holder arms each form a part of the slide bearing, on which the adjustment device is actuable back and forth and on which the adjustment device can be locked by locking means.

It is advantageously further provided for the fastening arms to each form, at the ends thereof, a bearing portion for fastening the backrest-side bearing to the backrest. By means of a bearing attached to the end, it is possible to achieve as great a distance as possible for the deformation curve of the backrest from the suspension points in the transverse direction.

In a particularly advantageous embodiment, the backrest supporting arm has a substantially curvate shape in its vertical direction and particularly advantageously has an S-shaped curvate shape. A slide bearing portion of the backrest supporting arm is thus likewise S-shaped, whereby the distance and thus the curvature of the backrest can be particularly advantageously adapted to the natural shape of the spine.

According to a preferred variant of the present invention, the bearings are fastened laterally to surfaces extending in the vertical direction, i.e. to vertically extending lateral surfaces of the backrest. Also advantageous in this case is a configuration in which the fastening arms engage laterally (in the manner of wings), with their end bearing portions, around the backrest at least in part. The backrest arrangement can also thus be designed such that the actuating arm extends substantially in parallel with one of the fastening arms, an actuating portion that is accessible to the seat user preferably being located on the end of the actuating arm, and specifically between the fastening arm and the backrest, so as to be able to release the actuating arm from its catch position. This arrangement allows the adjustment device to be operated in a particularly comfortable manner, since it is possible to simultaneously engage around the actuating portion and the two end bearing portions and to adapt the height of the adjustment device.

Owing to the arrangement according to the invention and the configuration of the adjustment device of the fastening and bearing points of the backrest, a backrest arrangement can be provided which can be adapted in a particularly ergonomic manner. Owing to an embodiment of this type, the material of the backrest, when sufficiently resilient, can absorb and uniformly distribute the compressive force exerted by a seat user supporting themselves against the backrest, yet without the shape of the backrest undergoing undesirable deformation, in particular in the edge region.

According to the present invention, a backrest arrangement is further provided, which has a deformable backrest and a spring-loaded backrest supporting arm. In this case, according to a preferred variant of the present invention, the lower fastening end of the backrest supporting arm is preferably formed by means of a connecting plate having a spring device, and specifically for fastening the backrest arrangement to a preferably central chair support in a spring-loaded manner. A central chair support can thus protrude through a part of the connecting plate of the backrest supporting arm, whereas the spring device is mounted in a spring-loaded manner. In this way, in addition to the resilience of the backrest provided by the deformability, the entire backrest arrangement can be moved back and forth and in a spring-loaded manner so as to provide the seated person with sufficient counterforce as soon as said person leans back on the chair. Overall, optimum coordination between stability and flexibility can be achieved by the suitable combination of the resilience of the deformable backrest and by the selection of the spring constant of the spring device.

The backrest arrangement is characterised in that the lower fastening end of the backrest supporting arm is connected to a spring device, preferably by means of a connecting plate, for fastening the backrest arrangement to a chair in a spring-loaded manner. The use of an adaptable helical spring in the spring device is particularly advantageous.

Advantageously, the helical spring extends from the connecting plate, together with a threaded rod, in the vertical direction in such a way that the connecting plate can be clamped, by the helical spring, against a top side, forming a bearing surface, of a seat carrier provided on the chair.

It is also advantageously provided for the lower fastening end of the backrest supporting arm to comprise a projecting fastening portion having openings for fastening to the connecting plate.

In an advantageous embodiment, the spring device comprises an axial threaded rod which is arranged inside the helical spring. Preferably, the spring device further comprises a journal bearing for the threaded rod, which journal bearing is vertically movable. The threaded rod is guided through a preferably cylindrical opening by means of the journal bearing. As a result, the helical spring is guided in its spring axis by the threaded rod.

Advantageously, an oblique stop is further provided on the underside of the fastening portion of the backrest supporting arm and is intended to rest on a corresponding opposite surface of a seat carrier attached to a chair. The seat carrier thus acts as a bearing surface for the connecting plate and/or for a fastening portion of the backrest supporting arm. When in its starting position, the helical spring presses the connecting plate of the backrest arrangement onto the bearing surface of the seat carrier and is fixed in this position. If the backrest is deflected backwards by a chair user, the connecting plate raises up from the bearing surface until a force equilibrium has been set between the force exerted onto the backrest and the restoring force of the helical spring on the connecting plate. In this position, the seat user can rock back and forth and their back is supported.

If the spring force of the helical spring can be adapted, an amount of support preferred in each individual case can be adapted for each seat user.

Advantageous embodiments of the invention are provided in the dependent claims and are described in more detail below on the basis of an embodiment by means of the drawings, in which:

FIG. 1 is a sectional side view of a first embodiment of an office chair comprising a backrest arrangement,

FIG. 2 is a side view, by way of example, of a backrest arrangement in a first and second adaptation position,

FIG. 3 is a perspective view of the backrest arrangement without a backrest,

FIG. 4 is a perspective view of a detail of the adjustment device of FIG. 3,

FIG. 5 is a sectional view along the sectional line AA according to FIG. 3,

FIG. 6 is a sectional side view of a backrest arrangement comprising a spring device,

FIG. 7 is a sectional side view through a backrest arrangement according to FIG. 6 interacting with a seat,

FIG. 8 shows a detail of FIG. 7.

FIG. 1 is a sectional view through an office chair 2 comprising a backrest arrangement 1 according to the invention. The office chair 2 comprises a central chair support 60 which is used as a chair leg. A seat 61 having a seat surface 62 is arranged on the chair support 60. A first embodiment of a backrest arrangement 1 according to the invention is further fastened to the chair support 60 on a seat carrier 63. The seat carrier 63 is thus attached to the chair support 60 by an annular portion 64. The annular portion 64 has a cylindrical opening for receiving a portion of the chair support 60. The top side of the seat carrier 63 forms a bearing surface 68 for the backrest arrangement 1.

As can be seen in FIGS. 1 and 3, the backrest arrangement 1 comprises a backrest supporting arm 10, a backrest 3 having an elastically deformable backrest pad 5 and an adjustment device 20. A fastening element 11 is located at the upper end 16 of the backrest supporting arm 10, to which fastening element the backrest 3 is fastened, and specifically in an upper region of the backrest 3. The backrest pad 5 comprises a plurality of transverse recesses 5a. As can be seen in particular in FIGS. 1 and 6, the backrest supporting arm 10 has a substantially S-shaped curvature and thus follows the natural shape of the spine. The backrest 3 is a deformable backrest fastened to opposite lateral surfaces 31, 32 of the backrest 3 by means of bearings, and specifically by means of counter-bearings 30 (bearings 30 in short) on the backrest side.

As shown in FIG. 2, the backrest-side bearings 30 are preferably formed as rotatable bearings. When the adjustment device 20 is displaced in the vertical direction H along the arrow shown in FIG. 2, the curvature and position, and thus also the height, of the lordosis support region 4 can be adapted. FIG. 2 shows two different views and thus two different adaptations of the backrest arrangement 1. In the left-hand view, a first, lower adaptation has taken place, whereas in the right-hand view, the adjustment device 20 has be actuated into a higher position. The adjustment device is displaced along slide bearings 13, 27, which will be described in more detail later. In the right-hand view, a sharper curvature of the backrest 3 has been produced. In an embodiment of this type, a biaxial cantilever principle is applied, which can be illustrated by means of FIG. 2. A first cantilever is produced in the vertical direction H between the upper and lower suspension point of the backrest, while a second cantilever is produced between the two lateral bearings 30 in the transverse direction Q.

FIG. 3 is a perspective view of an embodiment of a backrest arrangement 1. The backrest supporting arm 10 comprises a slide bearing portion 14. Slide bearings 13 in the form of elongate grooves are formed in the slide bearing portion 14. At the upper end 16 of the backrest supporting arm 10, there is a fastening element 11 for attaching the backrest 3. It is also possible to see an adjustment device 20 which is movable up and down in the vertical direction H and forms two fastening arms 22, which project laterally from the backrest supporting arm 10 in the transverse direction Q. In this case, the fastening arms 22 extend over the entire width of a backrest 3 (not shown in FIG. 3). The fastening arms 22 each further comprise bearing portions 23 at their ends. Bearings 21, which can be seen for example in FIG. 4, are located on the end bearing portions 23. The bearings 21 are used for fastening to counter-bearings. Backrest-side bearings 30 are provided on the backrest 3 as counter-bearings. The adjustment device 20 further comprises a preferably bridge-like bearing bracket 26, as can be seen in section in FIG. 5. Said bearing bracket is releasably connected to each fastening arm 22 by means of fastening means 33, with the formation of an opening 28.

The cross-sectional shape of the opening 28 substantially corresponds to the cross-sectional shape of the backrest supporting arm 10 in the region of the slide bearing portion 14. The backrest supporting arm 10 protrudes, with its slide bearing portion 14, through the opening 28. The adjustment device 20 can be displaced up and down along the slide bearing portion 14. FIG. 5, which is a sectional view along the section line A-A of FIG. 3, also shows that the slide bearing 27 formed by the bearing bracket 26 comprises two slide bearing cams 27a, 27b, which engage in the elongate slide bearings 13 of the backrest supporting arm 10.

The adjustment device 20 further comprises a catch device 24 which is connected to an actuating arm 25. The catch device 24 is formed as a catch device 24 which is movable back and forth and is actuable from a catch position into an adjustment position (according to FIG. 3) by means of the actuating arm 25. In the catch position, a catch means 24a engages in a mating catch means 24b, which is formed in a corresponding manner on the backrest supporting arm 10. By actuating an actuating portion 29, preferably at the end of the actuating arm 25, the catch means 24a of the catch device 24 can be released from the mating catch means 24b, whereby the adjustment device 20 can be moved up and down in the vertical direction H along the slide bearings 13, 27. As soon as the adjustment device 20 has been moved into the desired position and thus the lordosis support region has been adapted in terms of height and curvature, by releasing the actuating arm 25 said actuating arm can be moved back into the catch position by means of return springs 34, so that the catch means 24a engages in the mating catch means 24b. In this catch position, the adjustment device 20 is fixed at the adapted height. Suitable catch means 24a and 24b are, for example, toothed arrangements or racks or rack portions having corresponding teeth which can interlock.

FIG. 6 shows another embodiment of a backrest arrangement 1 according to the invention. Like reference numerals indicate like components, as already described above. A spring device 50 is arranged on the lower fastening end 15 by means of a connecting plate 58. The spring device 50 is connected to the connecting plate 58 on a spring suspension 51. The spring device 50 further has a helical spring 52 having an upper bearing means 53. The helical spring 52 is mounted in a spring-loaded manner about a threaded rod 54. The threaded rod 54 is arranged inside the helical spring 52.

FIGS. 7 and 8 allow the operation of the spring device 50 to be explained in more detail. FIG. 8 is a superposed view of a detail of FIG. 7, one view showing the starting position and one showing the compressed position of the helical spring 52. As can also be seen in FIG. 7, the backrest 3 can be deflected in a spring-loaded manner in a backward direction shown by the arrow (arrow at the upper end of the backrest) when a force is exerted, whereby the force is transmitted to the helical spring 52 via the connecting plate 58 and said spring is compressed accordingly. As soon as the helical spring 52 is tensioned, the resultant restoring force of the spring 52 is transmitted to the backrest supporting arm 10, the seat user experiencing a balancing counterforce as a result. Preferably, the desired deflection and thus the spring properties of the backrest arrangement 1 can be adapted by adapting the spring force of the helical spring 52 by means of an adaptation device 55.

In the following, reference is made to FIGS. 3, 7 and 8 to explain the design of the spring-loaded suspension of the backrest arrangement 1. As can be seen in FIG. 3, the lower end of the backrest supporting arm 10 is provided with a projecting fastening portion 56 having fastening openings. A seat carrier 63 having an annular portion 64 is also provided. As shown for example in FIG. 1, the seat carrier 63 is fastened to the chair support 60 by means of the annular portion 64. As can be seen in FIGS. 3 and 6, the fastening portion 56 is inserted into a fastening cartridge 57 and connected thereto. The fastening cartridge 57 comprises a connecting plate 58, on which the spring device 50 is arranged. An underside of the connecting plate 58 and of the fastening cartridge 57 rests on the surface of the seat carrier 63, which surface thus forms a bearing surface 68 for the backrest arrangement 1. In the present embodiment, the fastening portion 56 comprises an oblique stop 59, as can be seen in FIGS. 1 and 3. The oblique stop 59 acts as a stop for a corresponding surface of the seat carrier 63. As soon as a seat user leans back, the backrest arrangement 1 is deflected in a spring-loaded manner by means of the backrest supporting arm 10, in such a way that the connecting plate 58 is actuated upwards from the bearing surface 68 and is transferred into a deflected (upper) position as shown in FIG. 8. In this position, the helical spring 52 is compressed and generates, by means of the connecting plate 58, a restoring force onto the backrest supporting arm 10 and thus onto the backrest 3. As a result, the seat user experiences a balancing force and thus particularly good back support.

The spring device 50 comprises a helical spring 52, which is tensioned against an upper bearing means 53. The actuating direction of the spring device 50 is defined by the threaded rod 54. A threaded rod 54 is arranged inside the helical spring 52 and is connected to the upper bearing means 53.

At the lower end of the threaded rod 54 there is a wing screw 55. By actuating the wing screw 55 in a rotary manner, said wing screw is moved on the threaded rod in such a way that the spring is tensioned to a greater or lesser extent, depending on the direction of rotation, whereby the spring force of the spring device 50 can be adapted. The connecting plate 58 is connected to a journal bearing 65 which is movable up and down around the threaded rod 54. The journal bearing 65 comprises an opening 67 for the threaded rod 64. As can be seen in FIG. 8, the threaded rod 54 penetrates the opening 67 in the journal bearing 65 such that the end, connected thereto, of the connecting plate 58 can be moved up and down together with the journal bearing 65.

The journal bearing 65 is formed of a cylindrical annular element having a spring plate 66 fastened thereto, on which the lower end of the helical spring 52 is mounted. If the backrest is not deflected, the helical spring 52 presses the connecting plate 58 into a lower position (starting position) onto the seat carrier 63. By deflecting the backrest 3, the connecting plate 58 and the journal bearing 65 fastened thereto is transferred into the upper position shown in FIG. 8. In this case, a wobble clearance is provided between the inner casing of the journal bearing 65 and the outer casing of the threaded rod 54. This means that, in the lower position (starting position), the centre line of the journal bearing 65 extends so as to be offset transversely to the axial direction by a defined distance d with respect to the centre line of the threaded rod 54. In the upper position shown in FIG. 8, i.e. in the deflected position (deflection position), the centre line of the journal bearing 65 and the centre line of the threaded rod 54 are in an approximately corresponding position. The inner diameter of the journal bearing 65 is formed so as to be larger than the outer diameter of the threaded rod 54 by the size of the wobble clearance.

A chair user can rock back and forth between a starting position and a deflected position (deflection position) by means of the backrest 3. At the same time, a corresponding upwards and downwards movement of the connecting plate 58 is produced as a result. As can be seen in FIG. 1, the position of the spring device 50 is arranged with a slight forward offset (in the direction of the front seat region) with respect to the central chair support 60. Such a configuration allows a relatively long spring arm to be used in conjunction with the connecting plate 58 of the backrest arrangement 1.

Advantageously, the connecting plate 58 is provided with an opening in the region of the annular portion 64, which opening is formed such as to allow a deflection movement of the connecting plate 58 about an angle α. It is therefore preferable to form the inner diameter of the opening in the region of the annular portion 64 to be larger than the outer diameter of the annular portion 64, as is the case in the present embodiment.

As can further be seen in FIG. 6, the fastening cartridge 57 comprises a lateral stop 70, which abuts a lateral surface of the annular portion 60 when the backrest arrangement 1 is in the starting position.

In an alternative embodiment of the above-described design of the connection between the spring device 50 and the backrest supporting arm 10, this connection can also be established by means of a plurality of connecting plates 58 or comparable connecting devices.

LIST OF REFERENCE NUMERALS

• 1 backrest arrangement
• 2 office chair
• 3 backrest
• 4 lordosis support region
• 5 backrest pad
• 5a recesses
• 10 backrest supporting arm
• 11 fastening element
• 13 slide bearing
• 14 slide bearing portion
• 15 lower fastening end
• 16 upper fastening end
• 20 adjustment device
• 21 bearing
• 22 fastening arms
• 23 bearing portion
• 24 catch device
• 24a catch means
• 24b mating catch means
• 25 actuating arm
• 26 bearing bracket
• 27 slide bearing
• 27a slide bearing cam
• 27b slide bearing cam
• 28 opening
• 29 actuating portion
• 30 backrest-side bearing
• 31 lateral surface
• 32 lateral surface
• 33 fastening means
• 34 return spring
• 50 spring device
• 51 spring suspension
• 52 helical spring
• 53 bearing means
• 54 threaded rod
• 55 adaptation device (wing screw)
• 56 fastening portion
• 57 fastening cartridge
• 58 connecting plate
• 59 oblique stop
• 60 chair support
• 61 seat
• 62 seat surface
• 63 seat carrier
• 64 annular portion
• 65 journal bearing
• 66 spring plate
• 67 opening
• 68 bearing surface
• 70 stop

Claims

1. A backrest arrangement comprising a deformable backrest which extends in the vertical direction (H) and transverse direction (Q) and comprises a lordosis support region, the height and curvature of which can be adapted, a backrest supporting arm, wherein the backrest is connected to the backrest supporting arm on an upper fastening element, and an adjustment device for adapting the height and curvature of the lordosis support region, which adjustment device is arranged on the backrest supporting arm so as to be adjustable in height and wherein the adjustment device is connected to the backrest, by means of bearings having backrest-side counter-bearings, on fastening arms projecting in the transverse direction (Q).

2. The backrest arrangement according to claim 1, wherein the adjustment device comprises a catch device which is movable up and down from a catch position into an adjustment position and is actuable from the catch position into the adjustment position by means of an actuating arm, whereby the height of the adjustment device can be adapted along slide bearings in such a way that the height and curvature of the lordosis support region can be changed automatically by displacing the adjustment device.

3. The backrest arrangement according to claim 2, wherein the adjustment device comprises a preferably bridge-like bearing bracket which comprises the slide bearing and the bearing bracket is connected to the fastening arms, with the formation of an opening, and the backrest supporting arm being guided, by a slide bearing portion, through the opening.

4. The backrest arrangement according to claim 1, wherein the fastening arms each form a bearing portion at the ends thereof for fastening the backrest-side bearing to the backrest.

5. The backrest arrangement according to claim 1, wherein the backrest supporting arm is formed substantially in an S-shape.

6. The backrest arrangement according to claim 1, wherein the bearings are fastened laterally to lateral surfaces of the backrest.

7. The backrest arrangement according to at least one claim 4, wherein the end bearing portions of the fastening arms engage laterally around the backrest at least in part.

8. The backrest arrangement according to claim 2, wherein the actuating arm extends substantially in parallel with one of the fastening arms and an actuating portion that is accessible to the chair user between the fastening arm and the backrest is located at the end of the actuating arm for releasing the actuating arm from its catch position.

9. The backrest arrangement according to claim 1, wherein the backrest supporting arm is connected to a spring device by means of a connecting plate for fastening the backrest arrangement to a seat carrier in a spring-loaded manner.

10. The backrest arrangement according to claim 9, wherein the spring device comprises a helical spring, the spring force of which can be adapted.

11. The backrest arrangement according to claim 10, wherein the helical spring extends from the connecting plate in the vertical direction (H) around a threaded rod and an adaptation device is attached to the lower end of the threaded rod in order to be able to adapt the spring force of the helical spring.

12. The backrest arrangement according to at least one claim 10, wherein the connecting plate is clamped against a top side, which forms a bearing surface, of the seat carrier by the helical spring.

13. The backrest arrangement according to at least one claim 9, wherein the spring device comprises a vertically movable journal bearing having a cylindrical opening around the threaded rod, and said journal bearing is connected to the connecting plate.

14. A backrest arrangement comprising a deformable backrest and a backrest supporting arm, wherein the backrest is connected to the backrest supporting arm on an upper fastening element and wherein the lower fastening end of the backrest supporting arm is formed with a spring device by means of a connecting plate for arranging the backrest arrangement in a spring-loaded manner against the top side of a seat carrier attached to the chair.

15. The backrest arrangement according to claim 1, wherein the backrest comprises an elastically deformable backrest pad.

16. The backrest arrangement according to claim 1, wherein said backrest arrangement is for an office chair.

17. The backrest arrangement according to claim 14, wherein said backrest arrangement is for an office chair.

18. The backrest arrangement according to claim 14, wherein the backrest comprises an elastically deformable backrest pad.