EP0277912B1 - Chair, especially an office chair with a seat and a composite back support - Google Patents

Abstract

To permit adjustment of back parts of the chair, spring means, preferably in form of two U-bent spring rods, couple a lower back part (19) to an upper back part (21) and the effective spring length of the springs (23) is adjustable or changeable by moving a slider (27, 29), connected to one (21) of said back parts, for example via an attachment arrangement (23) of the spring elements themselves, longitudinally of the spring elements. Preferably, a positive stop arrangement to maintain an adjusted position is provided; or the adjusted position may be infinitely variable, for example by clamping the spring element in position by means of an eccentric. The ultimate deflection of the respective back parts can be limited by a stop (36) engaging a stop rod (47') which, simultaneously, can function as a slider guide, the stop rod (47), when springy itself, providing for a stiff terminal spring constant while permitting more easily yielding deflection before its engagement.

Description

The invention relates to a chair, in particular an office chair, with a seat and a multi-part backrest, which consists of at least two segments arranged one above the other, which are connected to one another by at least one spring joint.

EP-A-0 107 627 describes a chair whose backrest consists of five superposed segments which are connected to one another by four horizontal axes of rotation. The backrest thus formed is usually slightly arched backwards. When the chair user leans back, the individual segments turn around their axis so that the curvature of the backrest increases. The rotation of the segments takes place against the force of springs, which endeavor to return the backrest to the normal position. Since the backrest is usually trough-shaped to match the body cross section, the joints that connect the individual segments to one another must always be arranged in the middle of the backrest. A lateral arrangement is only possible if care is taken to ensure that the axes of rotation run parallel to one another, as is the case, for example, with the chairs according to FIGS. 5, 6 and 9 of the cited patent. However, this requirement severely limits the design freedom of the designer. If, however, the articulated connections are arranged in the middle of the backrest, the stability of the backrest suffers.

While most of the exemplary embodiments cited separate rotary joints and return springs in the cited citation, FIGS. 40 and 41 show an embodiment in which the segments are connected to one another by spring joints in the form of a torsion spring. Two torsion springs are provided for connecting two segments. These extend from one side of the backrest to the other side of the backrest and are rotatably mounted in the middle thereof. At each end of the torsion spring there is a part bent downwards or upwards for fastening to the lower segment or to the upper segment. This embodiment has the disadvantage that no less than five fastenings are necessary for two segments, namely four for the ends of the torsion bars and one for fastening the torsion bars in the middle.

An important disadvantage of all of the embodiments described in the cited prior publication is that the spring force cannot be adjusted by the user. The backrest proves to be too stiff for a light person, while it is too flexible for a heavy person. For a light person, dividing the backrest into different segments is of no advantage. There is no difference to a one-piece backrest. A heavy person feels insecure because the backrest does not offer any support when leaning back. She therefore feels that a backrest with several segments is disadvantageous rather than advantageous.

It is therefore an object of the present invention to improve a chair of the type mentioned in the introduction in order to avoid at least some of the disadvantages mentioned.

According to the invention, this is achieved in that a device with an adjusting member for changing the spring characteristic is provided for the respective spring joint. This enables the user to adapt the curvature behavior of the backrest to his needs when leaning back.

The spring joint is advantageously formed by at least one round rod. This results in a very simple and cheap construction of the spring joint. Two or more round bars can be used regardless of the curvature of the backrest due to the body cross section, since it does not matter in which direction the respective round bar is bent when it is used as a spring element. In contrast, when using leaf springs, care should be taken that they are on the same plane on each side of the chair.

Each spring joint advantageously has two parallel round bars. This is e.g. then the case when the spring joint has a hairpin-shaped spring element. According to the backrest, the spring joints can be arranged at an acute angle to the sagittal plane. There is therefore no need to provide a different spring joint for each side of the chair or to arrange the spring joints in a common plane.

The respective spring element is advantageously attached to one of the supports in an easily detachable manner. For example, a pawl with an actuator, e.g. a push button, serve to attach the spring element. If one segment is placed on top of the other, the latches can snap into place and hold the segment in place. Conversely, to release a segment, it is sufficient to press the push buttons and lift the segment. This enables easy interchangeability of the segments. The chair can then be supplied with different backrest segments, for example, which the customer can use as required.

It is possible to form the first support with the pawl, the actuator and a pawl spring from a single piece of plastic or sheet metal. This leads to a considerable simplification of the spring joint.

An expedient embodiment provides that one end of the spring element is fastened in the first support and that a stop for the spring element can be moved by the adjusting member in this first support, with which the effective length of the spring element can be changed. This allows easy adjustment of the spring characteristics by the user of the chair.

The stop is advantageously designed as a slide that runs in a guide in the first support. A detent spring can be provided to hold the slide in the desired position can snap into rest points arranged along the guide. This ensures that the stop remains in the set position. It is advantageously provided that the detent spring is attached to the slide, and that the adjusting member for the slide is attached to the detent spring and protrudes outwards through a slot on the support, the slot as a means for limiting the movement of the slide downwards and upwards serves.

It is also possible for at least one clamping element, e.g. an eccentric is provided. This version also enables easy manipulation of the slide.

The guide for the slide is particularly advantageously formed by a resilient rod or better two resilient rods. This has the advantage that it also contributes to the bending behavior of the spring joint.

The guide can also be formed as a hairpin-shaped spring element made of spring steel, preferably with a round cross section. This results in a cheap and aesthetically pleasing construction.

As a rule, it is expedient to use two spring joints, which are arranged at a lateral distance from one another, to connect two segments. This ensures high backrest stability. As already mentioned, the arrangement of the spring joints is not critical when using round bars as spring elements. It does not matter whether the backrest has a more or less curved horizontal cross-section.

• Fig. 1 einen Stuhl von hinten gesehen
• Fig. 2 eine Seitenansicht des Stuhls von Fig. 1
• Fig. 3 einen horizontalen Schnitt durch die Rückenlehne, wobei die Lage der Rundstäbe der beiden Federgelenke bei einer gewölbten Rückenlehne ersichtlich ist,
• Fig. 4 und 8 ein erstes Ausführungsbeispiel eines Federgelenkes mit einem ersten und einem zweiten Support,
• Fig. 5 einen Schnitt entlang der Linie V-V durch den ersten Support mit dem Federgelenk von Figur 4,
• Fig. 6 einen Schnitt entlang der Linie VI-VI von Figur 4,
• Fig. 7 den ersten Support mit dem Federgelenk und der Befestigungsbride für das Federgelenk, von hinten gesehen,
• Fig. 8 den zweiten Support,
• Fig. 9 einen Schnitt entlang der Linie IX-IX von Figur 8,
• Fig. 10 ein zweites Ausführungsbeispiel eines Federgelenkes,
• Fig. 11 einen Schnitt entlang der Linie XI-XI von Figur 10,
• Fig. 12 einen Schnitt entlang der Linie XII-XII von Figur 10,
• Fig. 13 einen Schnitt entlang der Linie XIII-XIII von Figur 11,
• Fig. 14 eine Ansicht von hinten des oberen Teils des Federgelenkes von Figur 10
• Fig. 15 einen Schnitt entlang der Linie XV-XV von Figur 14,
• Fig. 16 einen Stuhl wie in Fig. 1, aber teilweise im Schnitt und von vorn gesehen, wobei die Federgelenke vorn angeordnet sind,
• Fig. 17 eine Seitenansicht des Stuhles von Figur 16,
• Fig. 18 einen horizontalen Schnitt durch die Rückenlehne.

Embodiments of the invention will now be described with reference to the drawing. It shows:

• Fig. 1 seen a chair from behind
• FIG. 2 is a side view of the chair of FIG. 1
• 3 shows a horizontal section through the backrest, the position of the round bars of the two spring joints being apparent in the case of a curved backrest,
• 4 and 8 a first embodiment of a spring joint with a first and a second support,
• 5 shows a section along the line VV through the first support with the spring joint from FIG. 4,
• 6 shows a section along the line VI-VI of FIG. 4,
• 7 the first support with the spring joint and the mounting bracket for the spring joint, seen from behind,
• 8 the second support,
• 9 shows a section along the line IX-IX of FIG. 8,
• 10 shows a second exemplary embodiment of a spring joint,
• 11 shows a section along the line XI-XI of FIG. 10,
• 12 shows a section along the line XII-XII of FIG. 10,
• 13 shows a section along the line XIII-XIII of FIG. 11,
• 14 is a rear view of the upper part of the spring joint of FIG. 10
• 15 shows a section along the line XV-XV of FIG. 14,
• 16 shows a chair as in FIG. 1, but partially in section and seen from the front, the spring joints being arranged at the front,
• 17 is a side view of the chair of FIG. 16,
• Fig. 18 shows a horizontal section through the backrest.

The work chair shown in Figures 1 and 2 consists essentially of the base 11, the standpipe 13, the seat 15 and the backrest 17. Seat 15 and backrest 17 can have the usual upholstery. The chair can be a so-called synchronous chair, in which the seat 15 also tilts when the backrest 17 is inclined, about half as much as the backrest 17. However, the invention is not restricted to synchronous chairs.

The backrest 17 consists of at least two segments 19, 21 arranged one above the other, which are articulated to one another by means of two spring joints 23 arranged at a distance from one another. It would also be possible to provide only one spring joint 23, which would then be arranged in the center of the backrest in a known manner. But it is also possible to arrange more than two spring joints 23 side by side.

As FIG. 3 shows schematically, backrests generally have a curvature that is adapted to the body cross section. As mentioned in the introduction, problems arise from this because the axis of rotation must run perpendicular to the so-called sagittal plane 25. The usual swivel joints could therefore not be mounted at an acute angle to the sagittal plane 25, as is the case with the spring joints 23 according to FIG. 3.

A first embodiment of a spring joint 23 will now be described with reference to FIGS. 4 to 9. It is particularly important with this spring joint 23 that a device 27 with an adjusting member 29 is provided for changing the spring characteristic of the spring joint. The user of the chair has it in his hand to choose a harder or softer suspension.

The spring joint 23 has a first support 31 (FIGS. 4 to 6) and a second support 33 (FIGS. 8 and 9). These are used for attachment to the segments 19, 21 of the backrest 17.

Each spring joint 23 has at least one round rod 35 made of a spring material, e.g. Spring steel, on. These round rods 35 can be legs of a hairpin-shaped spring element 37 (FIG. 7).

One end of the spring element 37 is fastened in the support 31. For this purpose, a bracket 38 is used, which is screwed down with screws 39. The other end of the spring element 37 is screwed to the support 33 with the nut 41 and the bracket 43.

The device 27 for changing the spring characteristic of the spring element 37 essentially consists of a slide 45 which can be moved in a guide 47 in the support 31. The round rods 35 of the spring element 37 rest on this slide 45 or are located in the immediate vicinity thereof. Depending on whether the slide 45 is located a little further down or higher, the effective spring length is thus greater or smaller. The path by which the slide 45 can be adjusted is limited by the slot 49. The slider 45 is connected to the adjusting member 29 by means of a detent spring 53 which can snap into detent points 55 (FIGS. 5 and 7) arranged along the guide 47.

According to the second exemplary embodiment according to FIGS. 10 to 15, the spring joint 23 in turn has a first support 31 and a second support 33 for attachment to the segments 19 and 21 of the backrest. There are also two round rods 35 made of a spring material, e.g. Spring steel, provided in the form of legs of a hairpin-shaped spring element 37. One end of the spring element 37 is fastened in the support 31, which is formed, for example, by a block 30 made of plastic. Screws 32 are cast into this block 30. These screws 32 allow the support 31 to be fastened to the segment 19 by means of the nuts 34.

The other end of the spring element 37 is fastened to the segment 21 of the backrest by means of the bracket 43 and the support 33. For this purpose, the bracket 43 has four threaded connectors 44 which protrude through bores 46 of the segment 21, so that nuts 48 can be attached. The dimensions of the arms 43 'of the bracket are such that the legs 35 of the spring element 37 are not clamped, but can slide. This allows the segment 21 to be placed on or removed from the segment 19 with ease.

The support 33 is designed as a plastic part and has at the top a resilient part 50 with a pawl 52 and an actuator, e.g. a push button 54. If the segment 21 is thus placed on the segment 19, the respective pawl 52 snaps onto the uppermost part of the corresponding spring element 37 and holds it in the position shown. To remove the segment 21, it is sufficient to press the push buttons 54 on both sides of the segment 21, so that the pawls 52 release the spring elements 37 and the segment 21 can be lifted away. Instead of plastic, the support 33 could also e.g. be made as a stamped part from sheet metal.

As can be seen from FIGS. 10 and 14, the support 33 has a stop 36 with a U-shaped cross section, the ends of the U being bent outwards to form flanges 40. This design enables the support 33 to be inserted into a slot 22 in the segment 21. The support 33 is held in this slot 22 because the flange 40 is pressed against the wall of the segment 21 by clamping the bracket 43.

The device 27 for changing the spring characteristic of the spring element 37 essentially consists of a slide 45 which can be moved on a guide 47 of the support 31. If no force acts on the segment 21 in the direction of the arrow 60, the spring element 37 bears against this slide 45 or is located in the immediate vicinity thereof. Depending on whether the slider 45 is located a little further down or up, the effective length of the spring element 37 is thus smaller or larger. This enables the user to adapt the curvature behavior of the backrest to his needs when leaning back. On the slide 45 there is the adjusting member 29, with which the slide can be held in the desired position. For this purpose, the adjusting member 29 is rotatably mounted with the pin 54 and has two eccentrics 56 which can be actuated with the handle 58 in order to clamp or release the slide 45 on the guide 47.

In the embodiment shown, the guide 47 also consists of a hairpin-shaped spring element made of spring steel with a round cross-section or another suitable spring material. The spring element 47 used as a guide is expediently somewhat stiffer than the spring element 37. This resilient design of the guide 47 has the advantage that it also contributes to the bending behavior of the spring joint 23.

If we now consider the mode of action of the spring joints, it can be seen that when the user leans back, a force is exerted on the backrest 17 in the direction of the arrow 60 (FIG. 11). As a result, the upper part of the spring element 37, that is to say the part which is located above the slide 45, is bent out (to the right in FIG. 11). The lower the slide 45 has been set, the less force is required. The deflection of the spring element 37 is limited after a certain distance by the stop 36, on which the guide 47 abuts. The user of the chair finds support when moving backwards and therefore does not have the uncomfortable feeling of falling backwards practically unhindered. Since the guide 47 is also designed as a spring element, the user of the chair can still make a further movement to the rear. With this further movement, however, the combined forces of the spring elements 37, 47 become effective. This is perceived by the user as pleasant because it gives them a feeling of security.

Various changes are possible without departing from the spirit of the invention. Thus, the spring joints 23 can be arranged on the back (FIGS. 1 to 3) or, if the construction is correspondingly changed, on the front (FIGS. 16 to 18) of the backrest 17. The arrangement on the rear has the advantage of better accessibility. The arrangement on the front has the advantage that the fastening means 31, 33 and the adjusting member 29 are hidden under the back cushion, so that the chair has a more pleasing appearance to the eye.

Claims (20)

1. Chair, especially office chair, having a seat (15) and a multisectional back (17) comprising at least two segments (19, 21) located one above the other, said segments (19 being 21) connected by at least one spring link (23), characterised in that a device (27) having an adjusting member (29) to change the spring characteristic is provided for each spring link (23).

2. Chair as in claim 1, characterised in that the spring link (23) comprises at least one round rod.

3. Chair as in claim 2, characterised in that each spring link (23) comprises two parallel round rods (35).

4. Chair as in claim 3, characterised in that, according to the curvature of the back, the spring links (23) are arranged at an acute angle to the sagittal plane (25).

5. Chair as in one of the claims 1 to 4, characterised in that the spring link (23) comprises a hairpin- like spring element (37).

6. Chair as in one of the claims 1 to 5, characterised in that the spring link (23) comprises a first and a second support (31, 33) serving to secure the spring link (23) to the segments (19, 21) of the back (17).

7. Chair as in claim 6, characterised in that the spring element (37) is removably secured in one (33) of the supports.

8. Chair as in claim 7, characterised in that a latch (52) with an actuating member (54), e.g. a push button, serves to secure the spring element (37).

9. Chair as in claim 8, characterised in that the first support (33) together with the latch (52), the actuating member (54) and a latch spring (50) consist of an integral part.

10. Chair as in claim 9, characterised in that one end of the spring element (37) is secured in the first support (31), and in that a stop element (45) for the spring element (35, 37) is shiftable by the adjusting member (29) to thereby change the effective length of the spring element (35, 37).

11. Chair as in claim 10, characterised in that the stop element (45) is a slider, which is movable in guide means (47) of the first support (31).

12. Chair as in claim 11, characterised in that for securing the slider (45) in the desired position a ratchet spring (53) is provided which is capable to engage in ratchet positions (55) located along the guide means (47).

13. Chair as in claim 12, characterised in that the ratchet spring (53) is mounted on the slider (45) and in that the adjusting member (29) for the slider (45) is mounted on the ratchet spring (53) and protrudes outward through a slot (49) in the support (31), said slot (49) being a means to limit the upward and downward movement of the slider (45).

14. Chair as in claim 11, characterised in that for arresting the slider (45) in the desired position a clamping member, e.g. a excenter (56), is provided, which can-be actuated by a handle (58).

15. Chair as in one of the claims 11 to 14, characterised in that the guide means (47) for the slider (45) are provided by at least one resilient rod of the first support (31).

16. Chair as in claim 15, characterised in that the guide means (47) are provided by a second hairpin- like spring element of preferably round cross-section.

17. Chair as in one of the claims 1 to 16, characterised in that two segments (19, 21) are connected together by two spring links (23) being laterally spaced from each other.

18. Chair as in one of the claims 15 to 17, characterised in that an abutment (36) for the second spring element (47) is provided.

19. Chair as in one of the claims 1 to 18, characterised in that the spring link (23) is located at the rear side of the back (17).

20. Chair as in one of the claims 1 to 18, characterised in that the spring link (23) is located at the front side of the back (17).

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