EP0815778A1 - Improvements for systems with differential shaping of back supports of office chairs - Google Patents

Abstract

An office chair comprises a seat (A) and a back (D) made with two independently-adjustable spinal support sections, one for the thoracic and the other for the lumbar region of the spine. The back is connected by a bar (3) to a control box (B) beneath the seat equipped with two torsion bars (1,5) - one for the bar (3) and the other for columns (6) pivoted to the lumbar support section of the seat back and having different levels of elastic resistance. The seat back is made from glass fibres embedded in polyester foam, and the two torsion bars are positioned so that they act in sequence, the second coming into operation after the first.

Description

The present invention relates to office chairs with backrests adjustable, and it aims more specifically at improvements adjustable backrest systems with organs for independent adjustment of the thoracic portion and the portion lumbar of these files in order to make them more comfortable thanks to their ability to better adapt to different user back configurations.

We know that the adjustable seat backrest systems office are generally designed to fit a "average" user conformation. Because a user has relatively rarely this average conformation, we must admit that it is often the user who must adapt to his seat rather than the seat to the user. This therefore results in certain constraints, leading to user fatigue.

Recently, an attempt has been made to remedy this drawback. So the US patents 5,249,839 and 5,385,388 describe seats having independent adjustment of the thoracic portion and the portion back lumbar. According to this known construction, a first back support element, acting on said portion thoracic, is pivotally mounted on the control system adjustment, which is usually located under the seat cushion, while that a second support element of the back acts on said portion lumbar, said first and second support elements operating independently of each other in rotation towards the rear relative to the seat. The chest portion may take a lateral rotation movement to follow the torsional movements of the user's chest region, while the lumbar portion may be connected to means which by limiting lateral rotation.

Although this type of known construction leads to behavior natural and adjustable backrest, ensuring continuous back support the user, it still has some drawbacks.

Indeed, in the structure described in the aforementioned US patents, the mechanism determining the adjustable support of the lumbar portion is mounted fixed by relative to the column on which the seat rests swivel, that is to say that the seat base is fixed. Furthermore, in this same structure, the elements transmitting the action of this mechanism to said lumbar portion are relatively close to each other laterally due to the nature of this mechanism, whereas on the contrary it would be desirable for them to be located at the outer edge of the backrest.

We can therefore consider that, despite its qualities, the structure described in aforementioned US patents, does not yet sufficiently adapt to the user morphology, due to the nature of the mechanism used, namely pairs of springs housed in the fixed volume supporting the seat and resting on the column.

The present invention eliminates all of these drawbacks, thanks to a other mechanism, involving means ensuring resistance elastic of each of the support elements by elastic deformation under the action of a torsional stress.

These means can in particular be torsion springs, bars torsion or combinations of the two, but preferably according to the invention, they consist of a couple of torsion bars.

Furthermore, according to the invention, these means are associated with each other by in such a way that the second intervenes sequentially with respect to the first.

Thus, in the preferred case of two torsion bars, the second of these bars is mounted relative to the first so as to intervene after to have undergone the action of the deformation of the first.

More specifically, according to the invention, a first torsion bar determines the inclination of the thoracic portion of the backrest by tilting, around the fixed seat box, a first crew carrying a bar substantially vertical support from the high point of the backrest, and a second bar of torsion determines the inclination of the lumbar portion of the backrest, by tilting, around said first crew, of a second crew carrying columns supporting a substantially horizontal grab bar of the arched area adapting to the user's lumbar area.

The first crew consists essentially of a torsion bar horizontal constant section, working over its entire length, fixed to a end to a concentric sheath rotatably attached to the fixed housing of the seat, and serving as a reminder of the rotation of said sheath, which carries a casing tilting to which is fixed a corner bar whose top is articulated to a point on the backrest under pressure from the back of the rib cage the user, and preferably comprising at its other end means for preload allowing the hardness of the reaction to be adjusted at will of the file at said pressure.

The second crew consists essentially of a torsion bar horizontal preferably formed of four equal bars with square section, in order to allow the development of a higher degree of twist, this composite bar serving similarly to the previous one, as an organ to a pair of sleeves rotatably attached to said tilting casing and carrying at each end a vertical column, preferably at height adjustable, these columns supporting a determining horizontal grab bar, behind the backrest, the optimal degree of curvature of the lumbar region of the body of the user, ie the base of the spine and the pelvis. Of preferably also the central area of this second torsion bar includes prestressing means regulating at will the reaction of the lumbar portion of the backrest at user pressure.

• La figure 1 est un schéma cinématique des éléments essentiels du mécanisme selon l'invention, vu de côté ;
• La figure 2 représente schématiquement le principe du rôle fonctionnel de la première barre de torsion, vue de l'arrière ;
• La figure 3 représente schématiquement le principe du rôle fonctionnel de la seconde barre de torsion, vue de l'arrière ; et
• La figure 3a est une coupe verticale suivant X-X de la figure 3.

Other characteristics and details of the present invention will appear on reading the following description, corresponding to the attached drawing, in which:

• Figure 1 is a kinematic diagram of the essential elements of the mechanism according to the invention, seen from the side;
• FIG. 2 schematically represents the principle of the functional role of the first torsion bar, seen from the rear;
• FIG. 3 schematically represents the principle of the functional role of the second torsion bar, seen from the rear; and
• FIG. 3a is a vertical section along XX of FIG. 3.

In FIG. 1, the mobile elements are shown in solid lines in rest position, and in broken line in deformed position under the effect of user body.

In known manner, the seat according to the invention comprises a fixed casing B based on a pivoting column system P.

On the fixed box B is mounted the seat A of the seat, having preferably certain features which will be explained below.

In the housing B is mounted the first torsion bar 1 (Figure 2) carrying a first crew consisting of a tilting casing 2 integral a sleeve 11 concentric with the bar 1, to which it is fixed at one end 1a, this sleeve being rotatably attached to the housing B, and carrying a bar 3, having a first section 3a, oriented towards the rear substantially in the horizontal extension of the housing 2, and a second section 3b, at right angles with section 3a, extending upwards behind the backrest D which is attached to it hooked by a system of links 4 ensuring its maintenance whatever the height, preferably with the interposition of a silent block.

On the casing 2 is in turn mounted the second torsion bar 5 (figures 3 and 3a), mounted in a pair of rotary sleeves 12 and 13 welded to ends 5a and 5b of the bar, and carrying at their two external ends columns 6 substantially vertical, or slightly inclined backwards at rest, which are located on either side of the backrest, and which are joined to their upper part by a horizontal grab bar 7 in front of which is arch the lower portion of the backrest. Preferably, the height of the columns 6 can be adjusted, for example by means of racks, with which cooperate with detachable elastic pawls or fingers or analogues (as shown schematically in 14). As one can see in FIG. 3a, preferably the bar 5 is made up of four bars 5a, 5b, 5c, 5d of identical square sections, but each equal to a quarter of the section of the bar 5. When twisting, the contact surfaces of the small bars 5a, 5b, 5c, 5d slide against each other, facilitating the overall deformation by twisting the bar 5.

The operation of the device according to the invention is as follows:

When the user installs himself on the seat, leaning against the folder D, the pressure of the upper part of his back, corresponding to the back of his rib cage, acting on the high point 4 of the backrest and tube 3, will tilt the entire backrest by rotating the sleeve 11. Due to the welding of the sleeve 11 on the end 1a of the torsion bar 1, the latter will determine the resistance to this tilting, in degree and hardness.

Simultaneously, the user's lumbar portion will exert pressure on the lower arched part of the backrest D and the grab bar 7, with the same elastic holding effect, in degree and hardness. Moving in tilting forward of this lower portion is limited by stopper adjustable tabs fixed to the sheath against stops 16 fixed to the seat.

From the above illustration, it is clear that, for the user, thanks to the couple of torsion bars 1 and 5, dynamic support is obtained which adapts completely to the user's morphology, while in the structure known above recalled, the lumbar support was fixed.

From this new structure can be developed adjustments aimed at adapting the possibilities of the mechanism to the different user categories.

Thus, as illustrated in FIG. 2, the torsion bar 1 may include a prestressing system to adapt the hardness. To this end, on the end 1b of the bar 1 opposite the end 1a which is integral with the sheath 11, can be mounted a member 8 actuated by a button 9 located under the seat, and which tends to subject the bar 1 to a beginning of torsion, by support on the fixed base B even before the user exerts his weight on the folder. This beginning of torsion makes it harder to continue the user action.

Similar means can be used with torsion bar 5, such as illustrated in Figure 3. However, in this second case, the prestressing is exerted, not at the free end of the bar, as in the previous case, but at the center 10 of the bar, which then works twice as much on each side to reach the same inclination of the columns 6. For this purpose, the bar 5 carries a housing 15 (FIG. 3a), the tilting of which, controlled by the rod 10 'screwed into the housing 2, modifies the torsion of the bar 5. This structure ensures symmetry of operation, the bar serving at the same rotation axis time.

As also illustrated in Figure 1, the tilt point 1 of the housing 2 is located at the front of the pivoting column P. This results in a very low inclination of the rear portion of the seat A, (the front portion resting on the case B) even for a relatively large tilting of the backrest D, this which is sometimes sought after today. For example, for a report of distances of 2.5, backrest tilting up to 24 ° angle will cause an inclination of the seat only about 9 °. This contributes to overall seat comfort.

Similarly, according to the invention, the top of the seat A is convex, as shown in C, unlike the usual geometry in this type of seat.

Such an original geometry allows the rotation of the pelvis, which ensures a good lumbar support, especially since the femur is also convex.

Finally, according to the invention, the backrest D must be flexible enough to allow independent bending of its upper portion and its portion lower. For this purpose, a composite material may be used, for example formed of glass fibers embedded in polyether foam; so the seat comfort is formed by the curve and not by the thickness of the foam.

Claims (12)

Adjustable backrest system for an office chair, comprising an independent adjustment of the thoracic portion and of the lumbar portion of said backrest, of the type in which a first support element, acting elastically on said thoracic portion is pivotally mounted on the fixed control unit of said adjustment system, while a second support element acts elastically on said lumbar portion, said first and second support elements operating independently of one another in rotation towards the rear relative to the seat,
characterized in that the mechanical means ensuring the elastic resistance of each of the two support elements each consist of a member capable of undergoing elastic deformation under the action of a torsional stress, the two members being associated one with the 'other so that the second intervenes sequentially with respect to the first. System according to claim 1, characterized in that at least one of said members is a torsion bar, the other being a spring torsion. System according to claims 1 and 2, characterized in that the two members are torsion bars, the second of these bars being ascent from the first so as to intervene after having suffered the action of the deformation of the first. System according to claims 1 and 3, characterized in that a first torsion bar determines the inclination of the portion thoracic backrest by tilting, around said fixed control unit, of a first crew carrying a bar to the substantially vertical support of the high point of the backrest, while a second torsion bar determines the inclination and the camber of the lumbar portion of the backrest, by tilting, around said first crew, of a second crew carrying substantially vertical columns arranged on either side of the backrest, and supporting a substantially horizontal grab bar for the arched area adapting to the user's lumbar area. System according to claims 1, 3 and 4, characterized in that the first crew consists essentially of a torsion bar horizontal constant section, working over its entire length, fixed to a end to a concentric sheath rotatably attached to the fixed housing of the seat, and serving as a reminder of the rotation of said sheath, which carries a casing tilting to which is fixed a corner bar whose top is articulated to a point on the backrest under pressure from the back of the rib cage the user, and preferably comprising at its other end means for preload allowing the hardness of the reaction to be adjusted at will of the file at said pressure System according to claims 1, 3 and 4, characterized in that the second crew consists essentially of a torsion bar horizontal serving as a reminder for a pair of rotatable fixed sleeves said tilting casing and carrying at each end a vertical column, preferably height adjustable, these columns supporting a grab bar horizontal determining, behind the backrest, the optimal degree of curvature of the lumbar area of the user's body, i.e. the base of the spine vertebral and pelvis. System according to claim 6, characterized in that said bar is composite, formed by the association of four bars of sections squares equal to each other and each equal to a quarter of the cross-section of the bar composite, in order to allow the development of a degree of torsion higher. System according to claims 1 and 5, characterized in that on the end 1b of the bar 1 opposite the end 1a which is integral with the sheath 11, can be mounted a member 8 actuated by a button 9 located under the seat, and which tends to subject the bar 1 to a beginning of torsion, even before the user exerts his weight on the backrest. System according to Claims 1 and 6, characterized in that that a prestress is exerted at the center 10 of the bar, which works then twice more on each side to reach the same inclination of the columns 6. System according to any of the claims previous, characterized in that the upper surface of the seat is convex. System according to one of the preceding claims, characterized in that the backrest is made of a composite material flexible enough to allow bending independent of its portion upper and its lower portion. System according to claim 11, characterized in that the backrest is made of glass fibers embedded in polyether foam.

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