AU2007264236A1

AU2007264236A1 - Back rest for a stool or a chair, and stool or chair provided with such a back rest

Info

Publication number: AU2007264236A1
Application number: AU2007264236A
Authority: AU
Inventors: Martin Ballendat
Original assignee: Rohde and Grahl GmbH
Current assignee: Rohde and Grahl GmbH
Priority date: 2006-06-29
Filing date: 2007-05-26
Publication date: 2008-01-03
Also published as: RU2009102813A; EP2040582B1; WO2008000207A1; CN101478895A; CA2724761A1; DE202007007524U1; CA2653912A1; ES2367869T3; JP2009540970A; US20100301652A1; EP2040582A1; ATE516726T1; DE102006030018A1; KR20090034352A; CN101478895B

Abstract

The invention relates to a back rest for a stool or a chair, comprising two adjacent, spring-mounted back supports (3.1), each of which is fixed to a separate carrier part (4.1). Said back rest is characterised in that each carrier part (4.1) forms the first limb of an essentially L-shaped carrier (4), and the second limb (4.2) of each carrier (4) is fixed beneath the stool or chair seat in such a way that it can be pivoted about a horizontal axis against an elastic force.

Description

CERTIFICATE OF VERIFICATION Gudrun E. Draudt Of Schubertstr. 15a, 42289 Wuppertal, Germany state that the attached document Is a true and complete translation to the best of my knowledge of International Patent Application No. PCTI DE 2007 / 000954 Dated this 24th day of November 2008 Signature of Translator: Back Rest for a Stool or a Chair, and Stool or Chair Provided with such a Back Rest The invention concerns a backrest for a stool or chair with two back supports that are 5 positioned laterally adjacent to one another and are supported in a springy fashion, wherein each one is connected to a separate carrier part. In such a backrest, disclosed in DE 90 06 316 U1, each back support is provided on a separate carrier part. The carrier parts are positioned relative to one another in a V 10 shape and the lower ends of these carrier parts are attached to the rear of the seat on the chair frame. Even though the back supports, as a result of the springy properties of their two carrier parts, provide movability to some degree in order to adjust to the different seated positions of a seated person, it has been found that this construction is unable to relieve the backbone of a seated person for extended periods of time of being 15 seated in changing seated positions as well as of individual persons having greatly varying physical build. It is an object of the present invention to design a backrest for a seat or a chair in such a way that the seated person in different seated positions is supported optimally in the 20 area of the back or backbone. As a solution to this object, it is provided according to claim 1 that each carrier part forms the first leg of a substantially L-shaped support member and that the second leg of each support member is pivotable underneath the stool or chair seat against a spring 25 force about a horizontal axis. In this way, it is ensured that each back support optimally follows the back movement as a function of the different movements or seated positions of a seated person without losing their support function. In order to achieve that a seated person is optimally supported even for a lateral 30 movement or a lateral as well as rearwardly oriented movement, according to further invention it is provided that the support members are connected to one another by a - 1 Lit TRL of PCT/DE2007/000954 - First Named Inventor: Ballendat - Assignee: Grahl. working well. GmbH guide bar that is oriented in the rest position substantially perpendicularly to the support members, wherein the guide bar is supported in or on the seat understructure and connected to the support member in such a way that upon displacement of one back support to the front or to the rear the other back support is moved in the opposite 5 direction, respectively, wherein, for preventing a "jump" between the two back supports, they are preferably connected in a springy fashion to the support members in such a way that a substantially uniform continuous backrest is present. The guide bar is preferably pivotably connected with its ends to the support members 10 and, moreover, is pivotably supported on the seat or seat understructure between its pivot points on the support members. Further preferred embodiments of the invention are disclosed in the dependant claims. 15 The invention will be disclosed in the following with reference to the attached drawings. Figure 1 shows a view of a backrest that is fastened to a post of a chair or stool that is not shown otherwise. Figure 2 shows a view of a modified embodiment of a backrest. 20 Figure 3 shows a view of a further modified embodiment of a backrest. Figure 4 shows an embodiment of the type of attachment of a backrest on its carrier part. Figure 5 shows an exploded view of the embodiment according to Figure 4. Figure 6 shows an embodiment of the type of attachment of the support member of the 25 back support on the post of a chair or stool. Figure 7 shows an isometric illustration of a chair. Figure 8 shows a detail in isometric illustration of the column of the chair with attached seat frame on which the support members for the back supports are pivotably attached. Figure 9 shows in isometric illustration a plan view onto the seat understructure 30 connected to the seat frame. Figure 10 shows for illustration of the inventive principle a schematic partial view of the -2 UL TRL of PCT/DE2007/000954 - First Named inventor. Ballendat - Assignee: Grahl. workIng well. GmbH backrest construction in correlation to the seat understructure. Figure 7 shows an isometric view of a chair, comprised of a five star base 1.1 provided with coasters, a column 1 supported on the five star base, a seat 100, and a backrest 3 5 with two back supports 3.1 arranged laterally at a spacing from one another and connected to L-shaped support members 4 that are each comprised of a substantially vertically arranged carrier part 4.1 and a carrier part 4.2 that is substantially horizontally arranged. Each back support 3.1 is attached to a securing member 7 that is adjustable along the correlated carrier part 4.1 so as to assume different height-adjusted positions. 10 Each securing member 7 comprises rubber elements such that the individual back supports are movable relative to the carrier part 4.1. The carrier parts 4.1 are connected to one another by an elastically deformable transverse stay 9 having a spring stiffness that is designed such that free movability of the individual back support relative to the other back support is maintained to a limited extent. 15 According to Figures 1 to 3, the carrier parts 4.2 are pivotably supported by means of a support unit 2 about a horizontal pivot axis 5. The carrier parts 4.2 of the support member 4 are embodied as two-part levers, wherein a substantially vertically oriented spring element 6 acts on the free lever end 4.3 of the lever and wherein the force of the 20 spring element acting on the support member is changeable. This spring element 6 can be a tension spring, a pneumatic or hydraulic spring element or the like. Catch openings 8 provided in the area of the carrier parts 4.1 make apparent that the securing members 7 are height-adjustably mounted on the carrier parts 4.1. 25 According to Figure 2, the back supports 3.1 are connected approximately at their center by an elastically deformable transverse stay 3.2 whose strength is designed such that the back supports 3.1 maintain their function as individual supports wherein the free movability of one back support relative to the other back support is maintained to a limited extent. 30 According to Figure 3 the two back supports 3.1 each are also attached on their own -3 Lit. TRL of PCT/DE2007/000954 -First Named inventor Balendat - Assignee: Grahl. working well. GmbH carrier parts 4.1 of the support members 4 so as to be springy individually. In this embodiment of the backrest the securing members 7 are designed such that the upper ends of the carrier parts 4.1 project upwardly past the securing member 7. The free ends of the carrier parts 4.1 are connected to one another by an elastically deformable 5 transverse stay 9. Figure 6 shows a modified embodiment of the support member that Is pivotable about a horizontal axis. In or on the support unit 2 a horizontal shaft 20 is provided that has opposite threads; on It, the second legs 4.2 of the support member 4 are pivotably 10 supported. Each leg 4.2 is embodied as a two-arm lever whose free lever end 4.4 is bent upwardly and has a substantially horizontally oriented tension spring 22 attached thereto. For changing the force acting on the support members, the tension springs 22 are attached with their ends on an adjusting member 23 that is adjustable relative to a horizontal axis at different spacings; It supports, for example, a nut 24 that is engaged by 15 a threaded pin 25 that Is turnable by means of a knurled wheel 26. Each leg 4.2 supports in the area of its bearing location on the shaft 20 a threaded bushing 27 in such a way that upon rotation of the shaft 20 as a result of the opposite threaded sections of this shaft the two legs 4.2 will be adjusted relative to one another laterally so that the spacing between the back supports 3.1 according to Figures 1 and 3 can be adjusted. 20 Figures 8 and 9 show details of the seat fame 38 attached to the upper end of the column 1 on which the two support members 4 in the area of the free ends of the carrier parts 4.2 are attached so as to be pivotable about the schematically illustrated pivot axis 39. On the seat frame 38 a substantially box-shaped seat understructure 40 is fastened, 25 for example, by screws 41 that are guided In slotted holes 42 in such a way that the seat understructure 40, relative to the seat frame 38, can be moved forward and backward. The inventive principle of this construction will be explained in the following with the aid of the schematic illustration of Figure 9. 30 The principal Idea of the teaching of the present invention resides substantially in that .4 Lit. TRL of PCT/DE2007/000954 - First Named Inventor: Sallendat - Assignee: Grahl. working well. GmbH the two back supports 3.1 are coupled to one another such that upon change of the seated position of the person seated on the chair (stool) a movement of one back support, for example, to the rear causes a forced movement of the other back support to the front. As a result of the springy suspension of the back supports on the support 5 members 4 the two back supports 3.1 are able to assume a position such that a substantially uniform continuous backrest is provided when the user of the stool or chair upon laterally reclining will rest more strongly or push more strongly against one back support 3.1, in Figure 9 the one to the right, than against the other back support 3.1. The forced coupling of the two back supports 3.1 to perform oppositely oriented 10 movements is effected by means of a guide bar 43 that, in the rest position, is substantially perpendicularly oriented relative to the support members 4; the guide bar is supported in or on the seat understructure 40 and connected to the support parts 4.2 in such a way that upon rearward movement of one back support 3.1 the other back support is moved in the opposite direction, i.e., to the front. In Figure 9 the deflection 15 angle of the guide bar 43 relative to the central position is illustrated in an exaggerated way for explaining the action principle. In reality, the deflection angle is only minimal so that upon pivoting the ends of the guide bar 43 carry out only very minimal movements that are in the range of tenth of millimeters and, in this way, are compensated by the tolerances of the construction. 20 The ends of the guide bar 43 are connected to the respective carrier parts 4.2, for example, by means of ball joints 44 schematically illustrated in Figure 8b which are preferably supported in elastically deformable sleeves 44.1. The guide bar 43 is also preferably pivotably supported by means of ball joints 45 illustrated in Figure 9a in or on 25 the longitudinal support 40.2 of the seat understructure 50 in the central area between its connecting points on the carrier parts 4.2. The carrier parts 4.2 are supported by means of coil springs 46 arranged on the seat understructure 40 such that the two back supports 3.1 in the unloaded rest position have 30 the same spacing from the seat understructure 40 and the guide bar 43 is in a rest or middle position. -5 Ut TRL of PCT/DE2007/000954 - First Named Inventor: Ballendat - Assignee: Grahl. working well. GmbH According to Figure 8, the carrier parts 4.2 have upwardly oriented projections 47 on which the guide bar 43 Is connected pivotably. Pressure plates 48 adjoin the projections 47 that by means of plungers 49 passing through the frame 40.1 of the box-shaped seat 5 understructure 40 are supported on the coil springs 46 that are arranged perpendicularly to the pivot axis 39 in the seat understructure 40. The coil springs 46 are supported on blocks 50 that are slidable in the longitudinal direction of the springs and, in turn, are seated on cams 52 of a camshaft 51 that is turnable by means of a handle 53 In order to change by rotation of the cams 52 the pretension of the springs 46. 10 The guide bar 43 is guided in the frame 40.1 of the seat understructure 40 in an arc shaped guide groove 54 whose imaginary axes are parallel to the pivot axis 39 of the support members 4 and relative to the front of the chair are curved from top toward the bottom and toward the rear. 15 The guide groove 54 enables a pivoting or a tilting movement of the guide bar 43 in the area of the ball joints 45 in such a way that, when pivoting of the carrier part 4.2 to the rear, this carrier part is also pivoted downwardly while at the same time the opposite support part 4.2 is pivoted with opposite movements. 20 Figure 8 shows a position of the two carrier parts 4.2 in a central position in which they are substantially parallel to one another when the two back supports 3.1 are either not loaded or uniformly loaded. 25 When a user with uniform loading of both back supports 3.1 reclines backwardly, the guide bar 43 follows this rearward movement so that as a result of the pivotable support action of the guide bar 43 in or on the longitudinal support 40.2 the entire seat understructure 40 is pulled, on the one hand, to the rear and, on the other hand, its rear area is pivoted downward or lowered simultaneously; this is done in accordance with a 30 partial seat support action disclosed in DE 299 08 599 U1 with synchronizing mechanism and, as this structure Is known, is not the object of the present invention. -6 Lit. TRL of PCT/DE2007/000954 - First Named Inventor Ballendat - Assignee: Grahl. working well. GmbH Such a synchronizing mechanism serves for pivoting the seat in accordance with a predetermined angle ratio when pivoting the backrest to the front or to the rear. The rearwardly oriented movement of the seat understructure 40 is realized against the 5 force of pressure springs 60 that are supported between a support plate 61 that is stationary and forms part of the seat frame 38 and a support surface that is part of the movable seat understructure 40. The Figures 4 and 5 show how the securing member 7 Is attached to a back support in 10 order to enable pivot movements of this back support 3.1 relative to the securing member 7 about a vertical axis as well as a horizontal axis. A main body 10 that is box shaped and open in the upward and downward direction is provided at the end facing the securing member 7 with two wall sections 10.1 that are positioned at a spacing to one another and are preferably triangular in shape; they have opposed bearing 15 openings 10.11. On the securing member 7 a horizontally oriented bearing bushing 11 is mounted so that after passing the axle pin 12 through the bearing bushings 11 aligned with the bearing openings 10.11 the main body 10 is pivotably connected to the securing member 7. According to Fig. 5, in the space between the main body 10 and the securing member 7 a rubber stop 14 is positioned that is provided with a recess 14.1 20 that is matched to the shape of the bearing bushing 11. The spring stiffness of the rubber stop is designed such that a controlled pivot movement of the main body 10 about the horizontal axis 2 that is defined by the axle pin 12 is possible. The main body 10 is provided on the side facing away from the securing member 7 with 25 an opening that is delimited upwardly and downwardly by wall sections 10.2. The wall sections 10.2 are provided with bearing openings 10.21. A fastening element 13 that can be screwed fixedly to the back of each back support 3.1 has a vertically oriented bearing bushing 13.1 that supports a radially outwardly projecting partition 13.2. When the bearing bushing 13.1 is aligned with the bearing openings 10.21, an axle pin 14.2 can 30 be passed through these bearing openings 10.21 and the bearing bushing 13.1 so that the main body 10 is attached so as to be pivotable about a vertical axis on the fastening -7 Lit. TRL of PCTDE2007/000954 - First Named inventor: Ballendat - Assignee: Grahl. working well. GmbH element 13. The partition 13.2 limits within the sleeve-shaped main body 10 two receiving spaces for spring elements 15, preferably cylindrical rubber stops, whose dimensions and spring stiffness are selected such that a limited relative movement between the fastening element 13 and the main body 10 about a defined vertical axis 5 defined by the axle pin 11 is provided. Lit. TRL of PCT/DE2007/000954 - First Named Inventor: Ballendat - Assignee: Grahl. working well. GmbH

Claims

1. Backrest for a stool or a chair with two back supports (3.1) that are arranged laterally adjacent to one another and secured in a springy fashion, each of which 5 is connected to a separate carrier part (4.1), characterized in that each carrier part (4.1) forms the first leg of a substantially L-shaped support member (4) and in that the second leg (4.2) of each support member (4) is attached below the stool or chair seat so as to be pivotable against a spring force about a horizontal axis (5 or 39). 10

2. Backrest according to claim 1, characterized in that the support members (4) are connected by a guide bar (43) that Is oriented substantially perpendicularly to the support members (4) in the rest position, which guide bar is supported in or on a seat understructure (40) and connected to the support member (4) in such a way 15 that upon movement of one back support (3.1) to the front or to the rear the other back support (3.1) is moved in the opposite direction, respectively.

3. Backrest according to claim 2, characterized in that the ends of the guide bar (43) are pivotably connected to the support members (4) preferably by means of a ball 20 joint(44) that is supported in an elastically deformable sleeve (44.1).

4. Backrest according to claim 2 or 3, characterized in that the guide bar (43) is supported between its connecting points on the support members (4) In a pivotable way on the seat or a seat understructure (40). 25

5. Backrest according to claim 4, characterized in that the guide bar (43) is supported by means of a ball joint (45).

6. Backrest according to one of claims 2 to 5, characterized in that the guide bar 30 (43) is guided In arc-shaped guide grooves (44, 54) that are provided in or on the seat understructure (40) and whose imaginary axes extend parallel to the pivot -9 Ut. TRL of PcTIDE2007/000954 - First Named Inventor: Ballendat - Assignee: Grahl. working well. GmbH axis (39) of the support members (4) and, relative to the front end of the chair, are curved from the top to the rear and to the bottom.

7. Backrest according to one of the claims 2 to 6, characterized in that the guide bar 5 (43) is connected pivotably to the second legs (4.2) of the L-shaped support members (4).

8. Backrest according to claim 7, characterized in that the second legs (4.2) each have an upwardly oriented projection (47) and in that the projections (47) are 10 supported by springs (46) that, in the rest position of the L-shaped-support member (4), are uniformly pressure-loaded.

9. Backrest according to claim 8, characterized in that the springs (46) are coil springs whose longitudinal axis are perpendicular to the pivot axis (39) of the 15 support members (4) and are arranged in the area of the seat understructure (40).

10. Backrest according to claim 9, characterized in that on the projections (47) pressure plates (48) are mounted that are supported by means of plungers (46) 20 on the springs (46).

11. Backrest according to one of the claims 8 to 10, characterized in that the pretension of the springs (46) is changeable. 25

12. Backrest according to claim 11, characterized in that the springs (46) with their ends opposite the pressure plates (48) rest against blocks (50) movable in the longitudinal direction of the springs which blocks are supported on cams (52) of a camshaft (51) that is turnable from the exterior. 30

13. Backrest according to one of the claims 2 to 12, characterized in that the guide bar (43) is attached to the seat understructure (40) supported by means of - 10 Lit. TRL of PCT/DE2007/000954 - First Named Inventor: Ballendat - Assignee: Grahl. working wel. GmbH springs (60) in such a way that this seat understructure (40) upon pivoting of the support members (4) is movable to the front or to the rear relative to the seat frame (48). 5

14. Backrest according to one of the claims 1 to 13, characterized in that the back support (3.1) is attached in a springy fashion on the carrier parts (4.1).

15. Backrest according to one of the claims 1 to 14, characterized in that the back support (3.1) is attached to the carrier parts (4.1) so as to be pivotable about 10 substantially vertically oriented axis lines.

16. Backrest according to one of the claims 1 to 15, characterized in that the back supports (3.1) are positionable along the carrier parts (4.1) at different height positions. 15

17. Backrest according to one of the claims 1 to 16, characterized in that the back supports (3.1) are attached to securing members (7) slidable along the carrier parts (4.1). 20

18. Backrest according to one of the claims 1 to 17, characterized in that the two back supports (3.1) are connected to one another by means of an elastically deformable transverse stay (9) whose strength is selected such that the two back supports (3.1) maintain their function as individual supports and the movability of one back support relative to the other back support is maintained to a limited 25 extent.

19. Chair or stool, characterized in that it is furnished with a backrest according to one of the claims I to 18. 30

20. Backrest according to claim 1, characterized in that each carrier part (4.2) is substantially vertically oriented. - 11 Lit. TRL of PcT/DE2007/000954 - First Named inventor. Bailendat -Assignee: Grahi. working well. GmbH

21. Backrest according to claim 20, characterized in that the spring force acting on the support members (4) is changeable together. 5

22. Backrest according to one of the claims 20 to 21, characterized in that the two support members (4) are fixedly securable at different spacings from one another on their common horizontal pivot axis.

23. Backrest according to one of the claims 20 to 22, characterized in that each back 10 support (3.1) is pivotable about a horizontal axis relative to its carrier part (4.1).

24. Backrest according to claim 23, characterized in that each back support (3) is attached to a securing member (7) that is securable along the correlated carrier part (4.1) at different height positions. 15

25. Backrest according to claim 24, characterized in that each back support (3) is attached by intermediate positioning of at least on elastically deformable spring element on its securing member (7). 20

26. Backrest according to claim 24, characterized in that on each securing member (7) a body (10) is attached that is pivotable against a spring force about a horizontal axis (12), wherein the body, in turn, is attached to a back support (3) so as to be pivotably against a spring force about a vertical axis (14). 25

27. Backrest according to one of claims 20 to 26, characterized in that the two back supports (3) are connected to one another by means of an elastically deformable transverse stay (3.2) whose strength is selected such that the two back supports (3) maintain their function as individual supports and the movability of one back support relative to the other back support is maintained to a limited extent. 30

28. Seating furniture in the form of a stool, a chair or the like, furnished with a -12 Lit. TRL of PCTIDE2007/000954 - First Named Inventor: Ballendat - Assignee: Grah. working well. GmbH backrest (3) according to one of the claims 20 to 27, whose seat Is attached by means of a support unit (2) on a column (1), characterized in that the second leg (4.2) of each support member (4) that is pivotably connectable about a horizontal axis is configured as a two-arm lever, wherein the spring force acts on the free 5 lever end (4.3 or 4.4) of the lever.

29. Seating furniture according to claim 28, characterized in that the spring force is effected by means of a spring element (22) that is substantially oriented vertically. 10 30. Seating furniture according to claim 28, characterized in that the second leg (4.2) in the area of its free lever end has a bent section (4.4) oriented upwardly or downwardly, wherein an essentially horizontally oriented spring element (22) acts on the bent section. 15 31. Seating furniture according to claim 28, characterized in that the bent section (4.4) is oriented upwardly and in that the spring element is a tension spring (22) and in that the ends of the tension springs (22) of both support members are attached to an adjusting member (23) that is securable relative to the horizontal axis at different spacings for changing the force acting on the support members. -13 Lit. TRL of PCT/DE2007/000954 - First Named Inventor Ballendat - Assignee: Grahl. working well. GmbH Received in the International Bureau on 29 October 2007 (10129/2007) 1. Backrest for a stool or a chair with two back supports (3.1) that are arranged 5 laterally adjacent to one another and secured in a springy fashion, each of which is connected to a separate carrier part (4.1), wherein each carrier part (4.1) forms the first leg of a substantially L-shaped support member (4), whose second leg (4.2) is attached below the stool or chair seat so as to be pivotable against a spring force about a horizontal axis (5 or 39), characterized in that the support 10 members (4) are connected by a guide bar (43) that is oriented substantially perpendicularly to the support members (4) In the rest position, which guide bar is supported in or on a seat understructure (40) and connected to the support member (4) in such a way that upon movement of one back support (3.1) to the front or to the rear the other back support (3.1) is moved in the opposite direction, 15 respectively. 2. Backrest according to claim 1, characterized in that the ends of the guide bar (43) are pivotably connected to the support members (4) preferably by means of a ball joint(44) that is supported in an elastically deformable sleeve (44.1). 20 3. Backrest according to claim 1 or 2, characterzed in that the guide bar (43) is supported between Its connecting points on the support members (4) In a pivotable way on the seat or a seat understructure (40). 25 4. Backrest according to claim 3, characterized in that the guide bar (43) is supported by means of a ball joint (45). 5. Backrest according to one of claims 2 to 4, characterized in that the guide bar (43) is guided in arc-shaped guide grooves (44, 54) provided in or on the seat 30 understructure (40) whose imaginary axes extend parallel to the pivot axis (39) of Amended Sheet (Article 19) - 1 Lit. TRL of Amended Claims - PCT/DE2007/000954 - First Named Inventor: Ballendat - Assignee: Grahl. working well. GmbH the support members (4) and, relative to the front end of the chair, are curved from the top to the rear and to the bottom. 6. Backrest according to one of the claims 2 to 5, characterized in that the guide bar 5 (43) is connected pivotably to the second legs (4.2) of the L-shaped support members (4). 7. Backrest according to claim 6, characterized in that the second legs (4.2) each have an upwardly oriented projection (47) and in that the projections (47) are 10 supported by springs (46) that, in the rest position of the L-shaped support member (4), are uniformly pressure-loaded. 8. Backrest according to claim 7, characterized in that the springs (46) are coil springs whose longitudinal axis are perpendicular to the pivot axis (39) of the 15 support members (4) and are arranged in the area of the seat understructure (40). 9. Backrest according to claim 8, characterized in that on the projections (47) pressure plates (48) are mounted that are supported by means of plungers (46) 20 on the springs (46). 10. Backrest according to one of the claims 7 to 9, characterized in that the pretension of the springs (46) is changeable. 25 11. Backrest according to claim 10, characterized in that the springs (46) with their ends opposite the pressure plates (48) rest against blocks (50) movable in the longitudinal direction of the springs which blocks are supported on cams (52) of a camshaft (51) that is turnable from the exterior. 30 12. Backrest according to one of the claims 2 to 11, characterized in that the guide Amended Sheet (Article 19) -2 Ut. TRL of Amended Claims - PCTIDE2007/000954 - First Named Inventor Ballendat - Assignee: Grahl. working well. GmbH bar (43) is attached to the seat understructure (40) supported by means of springs (60) in such a way that this seat understructure (40) upon pivoting of the support members (4) is movable to the front or to the rear relative to the seat frame (48). 5 13. Backrest according to one of the claims 1 to 12, characterized in that the backrest (3.1) is attached in a springy fashion on the carrier parts (4.1). 14. Backrest according to one of the claims 1 to 13, characterized in that the backrest 10 (3.1) is attached to the carrier parts (4.1) so as to be pivotable about substantially vertically oriented axis lines. 15. Backrest according to one of the claims 1 to 14, characterized in that the back supports (3.1) are positionable along the carrier parts (4.1) at different height 15 positions. 16. Backrest according to one of the claims 1 to 15, characterized in that the back supports (3.1) are attached to securing members (7) slidable along the carrier parts (4.1). 20 17. Backrest according to one of the claims 1 to 16, characterized in that the two back supports (3.1) are connected to one another by means of an elastically deformable transverse stay (9) whose strength is selected such that the two back supports (3.1) maintain their function as individual supports and the movability of 25 one back support relative to the other back support is maintained to a limited extent. 18. Backrest according to claim 17, characterized in that on each securing member (7) a body (10) is attached that Is pivotable against a spring force about a 30 horizontal axis (12), wherein the body, in turn, is attached to a back support (3) so Amended Sheet (Article 19) -3 Ut. TRL of Amended Claims - PcT/DE2007/000954 - First Named Inventor: Ballendat - Assignee: Grahl. working well. GmbH as to be pivotably against a spring force about a vertical axis (14). 19. Chair or stool, characterized in that it is furnished with a backrest according to one of the claims 1 to 18. 5 20. Seating furniture in the form of a stool, a chair or the like, whose seat is attached by means of a support unit (2) on a column (1), and comprising a backrest (3) that has two back supports (3.1) that are arranged laterally adjacent to one another and secured in a springy fashion, each of which is connected to a substantially vertically extending carrier part (4.1), wherein each carrier part (4.1) forms the 10 first leg of a substantially L-shaped support member (4), whose second leg (4.2) is attached below the seat so as to be pivotable against a spring force about a horizontal axis, characterized in that each support member (4) has correlated therewith a separate spring element (6, 22). 15 21. Seating furniture according to claim 20, characterized In that the force of the spring elements (6, 22) acting on the support members (4) is changeable together. 22. Seating furniture according to claim 21, characterized in that the second leg (4.2) 20 of each support member (4) which second leg is pivotably connectable about a horizontal axis is configured as a two-arm lever, wherein the spring force acts on the free lever end (4.3) of the lever. 23. Seating furniture according to claim 22, characterized in that the spring force is 25 effected by means of a spring element (6) that is substantially oriented vertically. 24. Seating furniture according to claim 22, characterized in that the second leg (4.2) in the area of its free lever end has a bent section (4.4) oriented upwardly or downwardly, wherein an essentially horizontally oriented spring element (22) acts 30 on the bent section. Amended Sheet (Article 19) -4 Ut. TRL of Amended Claims - PCT/DE2007/000954 - First Named Inventor Ballendat - Assignee: Grahl. working well. GmbH 25. Seating furniture according to claim 24, characterized in that the bent section (4.4) is oriented upwardly and in that the spring element is a tension spring (22) and in that the ends of the tension springs (22) of both support members are attached to an adjusting member (23) that is securable relative to the horizontal 5 axis at different spacings for changing the force acting on the support members. 26. Seating furniture according to one of the claims 20 to 25, characterized in that each back support (3) is attached height-adjustably on its carrier part (4.1). 10 27. Seating furniture according to one of the claims 20 to 26, characterized in that each back support (3) is attached in a springy fashion on its carrier part (4.1). 28. Seating furniture according to 27, characterized in that each backrest (3) is pivotable relative to its carrier part (4.1) about a horizontal axis. 15 29. Seating furniture according to claim 27 or 28, characterized in that each back support (3) is pivotable about a vertical axis relative to its carrier part (4.1).

30. Seating furniture according to one of the claims 26 to 29, characterized in that 20 each back support (3) is attached to a securing member (7) that is fixedly securable along the corresponding carrier part (4.1) at different height positions.

31. Seating furniture according to claim 30, characterized in that each back support (3) is attached by intermediate positioning of at least on elastically deformable 25 spring element on its securing member (7).

32. Seating furniture according to claim 31, characterized in that on each securing member (7) a body (10) is attached that is pivotable against a spring force about a horizontal axis (12), wherein the body, in turn, is attached to a back support (3) 30 so as to be pivotably against a spring force about a vertical axis (14). Amended Sheet (Article 19) -5 Ut. TRL of Amended Claims - PCTIDE2007/000954 - First Named Inventor: Ballendat - Assignee: Grahl. wordng well. GmbH

33. Backrest according to one of claims 20 to 29, characterized in that the two support members (4) are fixedly securable at different spacings from one another along their common horizontal pivot axis. 5 Amended Sheet (Article 19) -6 Lit. TRL of Amended Clakns - PCT/DE2007/000954 - First Named Inventor Ballendat - Assignee: Grahl. working well. GmbH