The invention relates to a chair, where a seat with two seat sides comprises a plate body connected to a base.

The invention is based on the known chair type where the chair's seat and back are composed of a preferably laminated plate body made of wood or moulded from plastic and supported by a base preferably composed of four legs, but not limited to such a specific type of chair.

Chairs of this type are simple, but nevertheless offer a relatively good degree of seating comfort, with the possibility of a certain degree of flexing in the back. A need exists, however, for improvement in the seating comfort, with the possibility of tilting the chair body forwards and backwards from the normal position. There is therefore a need to be able to lean forward while depressing the chair seat's front portion in a supportive manner or to lean slightly backwards against the backrest, thus causing the chair seat to tilt backwards about a transverse axis. It is an object of the invention to provide a chair with a flexible/resilient plate body which permits the material of the actual plate body or chair seat to flex, thus permitting tilting movements to be implemented in a simple manner, without the use of additional means such as pivotal axes, bearings, compression bodies, springs, torsion bars and the like, which are known from more expensive chairs, such as sophisticated office chairs and other seating units. According to the invention, therefore, a chair is proposed as indicated in claim 1. Further features of the chair are indicated in the dependent claim.

According to the invention it is proposed to employ the actual plate body as a torsion body, more specifically by having a part of the plate body between the connection with the base and the rest of the plate body designed in the form of a torsion body.

A chair is thereby provided in a strikingly simple manner where the user can perform the requisite, desired tilting movements forwards and backwards from a backward-leaning position of rest to a forwardly angled seated position, all the time with full support, in the same way as in more complicated chairs with tilt mechanisms. In a chair where the plate body is connected to the base at each of the two seat sides, the torsion body may be advantageously designed so that from each side in the plate body, inwardly directed from the edge of the seat, there is provided a weakened portion on each side of the connection with the base. In such a chair the torsion body may advantageously be designed by a cut-out being made in the plate body from each edge of the seat, on each side of the connection with the base.

In a chair where the plate body is connected to the base centrally between the edges of the seat, the torsion body is advantageously designed by providing a weakened portion in the plate body or removing a transversally limited cut-out on each side of the connection with the base. In an advantageous embodiment a single plate body forms the seat and a backrest.

A torsion body may advantageously be provided in such a backrest, where the plate body has weakened points or cut-outs in the back portion as described for the seat, preferably approximately halfway up the backrest. These weakened points/cut-outs will provide flexibility with torsional capability for the plate body. This provides flexibility in an otherwise well-designed back support, but also permits the back plate to be flat in the starting position, and to conform to the user's back when under a load.

The invention will now be explained in more detail, with reference to the drawing, in which Figure 1 is a perspective view of a chair according to the invention,

Figure 2 is a perspective view of a second chair according to the invention, Figure 3 is a perspective view of yet another chair according to the invention and

Figures 4a, b and c are schematic side views of a chair like that in figure 1 , indicating tilting movements. Figures 5a-d are illustrations corresponding to figures 4a-c, but of a second embodiment.

In figure 1 a chair 1 is illustrated composed of a laminated plate body 2, which is connected 5 and 6 at the two seat edges 3 and 4 with a base, consisting here of two legs 8 and 9 positioned at an angle to each other from the seat 7. On each side of the connections 5, 6, a cut-out 10, 11, 12 and 13 is made in the plate body 2, thereby forming a torsion body 14 from the intermediate part of the plate body 2. The chair illustrated in figure 2 is like that in figure 1, but the backrest is provided with cut-outs 15-19, thus making the plate body 2 flexible and capable of being twisted in this back area. The chair 20 in figure 3 is composed of a plate body 21 as in figures 1 and 2, but here the plate body 21 is connected with the base's legs 22-25 in a central seat area 26. In order to fashion the desired torsion body, two transversal cut-outs 27 and 28 are made in the plate body 21.

Figures 4a, b and c illustrate the tilting movements a seated person 29 can perform while sitting on a chair like that in figure 1. Figure 4a depicts a "normal" seated position. In figure 4b the person 29 is leaning backwards and in figure 4c he is leaning forwards. It can be seen that the seat 7 will tilt and be "tailored" to the person's 29 thighs and seat, thanks to the torsion body 14.

A similar illustration can be seen in figures 5a-d. Here the chair is designed with straight and flat seat and back parts. The figures clearly illustrate how the chair adapts to the user's sitting positions.

It will be appreciated that the cut-outs may be in the form of weakened points in the plate, thereby permitting a limited amount of twisting. These weakened portions may also be in the form of bellows or accordion-like connections between the otherwise fixed plate portions.

By means of the invention a kind of "dynamic sitting" is achieved, where one moves with the chair about a fixed pivotal or balance area, which is preferably located in the user's balance point (the body's centre of gravity).