1 The present invention relates to a chair structure provided with a framework consisting of two mutually, parallel, substantially triangular U-shaped bow members and two or more transverse bracing members, where the legs of the U-shape converge towards each other from each end of the web portion of the U-shape, and where the web portion of the U- shape, at least at the outer ends, formsa support against the floor, while the legs of the U-shape form a fastening for a chair seat member and a back member respectively which members are spaced apart vertically and horizontally from each other, with the chair seat member (11) having a length which is short relative to its breadth. In current designs of chairs and other seating devices great weight is placed on arranging the con¬ ditions so as to obtain a correct sitting position. Correct support for the lumbar portion and the seat portion of the user is aimed for and besides the possibility for movement of leg portions, thigh portions and hip portions. Especially has the impor¬ tance been realised of being able to permit the move¬ ment of the hip portion of the user.

Hitherto those kinds of chairs which have been designed have been especially adapted to give a

"static" support for the user, that is to say in a sitting position there is a minimum basis for move¬ ment of .the seat portion and the hip portion. The result is that even if the chair provides an anatomi- cally and physiologically correct support for the user in a certain sitting position the chair can nevertheless feel hard and unpleasant to sit in over an extended period of use, as it can be problematic all the time to sit in such a certain sitting position. Practical experience has shown that the user of a chair has a need for a certain possibility for move¬ ment in the back, seat and thigh portions including

OMPI "

continuous small movements for altering the sitting position and for changing the pressure points, especially on using the chair over an extended period. With the present invention the aim is a chair which gives the user the possibility of being able to adjust and alter the sitting position acccrding to desire and need during use of the chair in a manner better than with previously known chairs. At the same time the aim is to give the user an intentionally effective support in the small of the back and seat portion in the various positions of use by automati¬ cally accomodating portions of the user's body to support members,of the chair.

According to the invention there is proposed a chair structure which is characterized in that the bow members are made of an elastically yielding material, for example of a strip-shaped material with a breadth of 15-20 times the thickness of the strip, enabling certain, mutual movements of the bow portions in the main plane of the bow member, the bow members being mutually locally reinforced in relation to each other in a direction transversely of the chaix in regions between the chair seat and the back, prefer¬ ably just below the chair seat and just below the back and approximately at the centre of the web portion, and that the seat-supporting leg of the U-shape together with the web portion of the U-shape have an S- shaped form, the central axis of the chair seat member being arranged substantially vertically above and at least not substantially in front of a forwar ly curved chair support portion at the transitior_. between the seat-supporting leg and the web portion of the U- shape, the central axis of the back member being in a manner known per se arranged at a substantial distance in front of a rearward chair support member at the transition between the back-supporting leg and the web portion- of the U-shape.

OMPI

By designing according to the invention the bow members of elastically yielding material, and by simultaneously reinforcing the bow members mutually locally in relation to each other transversely of the chair, one has achieved a chair structure having a considerable rigidity in the lateral direction and simultaneously giving a desired movability in the longitudinal direction between the chair seat and the back. By this there is the possibility of limiting different large, free-lying openings between the back and the chair seat in order that the user can accommodate his body portions in said opening, while the chair seat and the back are removed horizontally in relation to each other in an elastically yielding way. This accommodation of portions of the body of the user to the opening between chair seat and back is in practice adjusted according to -the weight and body dimensions of the individual user and the degree of force exerted in the sitting position. It is a special advantage that the user in voluntary sitting positions automatically obtainsa desired support of the small of the back at the back, as the user naturally accommodates his body portions in a cooperating support member towards the chair seat and the back ^• in the user's different sitting positions. In this connection it is of great importance that the seat-supporting legs of the U- shape together with the web portion of-the U-shape have an S-shaped form, so that the central axis of the chair seat member can be arranged substanti- ally vertically above a forwardly curved chair support portion. By this it can be built in a considerable elasticity in the rounded transition portion of the U- shape. Simultaneously -it can be made a desired controlled tilting of the chair in the forward direc- tion around its forward, curved chair support por¬ tions. By simultaneously arranging the central axis of the back member in a substantial distance in front

_OMPi_

of a rearward chair support portion one can in a known manner avoid an undesired rearward tilting of the chair, simultaneously as one ensures an effective support of the user's small of the back. By the chair seat - in a manner known per se .- having a short extension in the longitudinal direction of the chair, in combination with the above-mentioned longitudi¬ nally elastic chair, it has been made possible to make an easy, controlled tilting of the chair in a desired way. A considerable advantage by such a relatively short chair seat in combination with the longitudi¬ nally elastic chair is that it is provided a limited support surface for the user's seat portion in different sitting positions or tilting positions. At the outset this can be considered unfavourable purely from a loading point of view, since the loading on the seat portion of the user is limited to a smaller pressure area, but in practice it has been found that the muscles in the seat portion of the user have a tendency to be pressed to the side, while the user can consequently remain sitting on the sitting nodes themselves in the seat portion and can thereby transfer the load to the chair seat in a favourable manner. A greatest advantage with the short seat in combination with the longitudinally elastic chair is, however, that the user's chair can easily have diffe¬ rent tilting positions with effective support for the user's seat portion in the seat portion of the chair with a stable support of the user's small of the back in the back of the chair. Such tilting positions can be utilised especially for different accommodation of portions of the body of the user in the intermediate space between the chair seat and the back in the sitting position. In other words the user can, while he sits, effect considerable changes in the sitting position in a ready manner by slight tilting movements or other minor movements on the defined sitting area

1 OMPI

by movement of the hip portion (the hip joint) , without thereby changing the support from the chair seat and from the back to a significant degree. In this way the user can distribute the pressure loading according to desire and need between the small of the back and the seat portion by a simple movement of leg portions and/ or back portion of the user. Practical tests have shown that relatively short and slight as well as large or tall and heavy persons can easily accommodate their sitting positions as required by contracting and stretching legs and thigh portions respectively by the corresponding bending forwards and leaning backwards of the back portion of the user.

The chair according to the invention has proved to be well suited as a chair for everyday use and sitting device, at the office, in factories, in meeting places as well as in the home and well suited for relatively sedentary activities as well as for more "moveable" activities in connection with different work situations and the like.

A particular advantage of the solution according to the invention is that the chair can be designed in a simple and robust fashion with stable use properties, but nevertheless with an- aesthetically attractive shape.

Even if the chair according to the invention can be adjusted to a large extent during use with different distances between chair seat and back, all according to what degree the members are pressed from each other by the user either by the influence of force or by the influence of weight, and even if the chair accor¬ ding to the invention can compensate for considerable deviations in the body dimensions of the user, there are instances where a further pre-regulation can be appropriate. In this case it is ensured according to the invention that the chair seat member is horizon¬ tally regulatable relative to the back member, and

OMPI

that the back member is vertically regulatable relative to the chair seat member. It is preferred in this connection that the back member and the chair seat member are dismantleably fastened to the bow members and are fixed between the bow members with the aid of easily dismantleable fastening members, such as srews, which connect bracing members of the bow to the bow members.

A favourable practical solution is achieved by connecting the back member and the chair seat member respectively to the bow members by means of one or more pins which project endways outwards from the back member and the chair seat member and corresponding holes in the internal side edge of the bow member, the bow members preferably being provided with a row of consecutive" holes for regulatable adjustment of the back support member in the height direction and the chair seat member in the horizontal direction relative to the back support member. Further features of the solution according to the invention will be evident from the following de¬ scription having regard to the accompanying drawings, in which:

Figs. 1 and 2 show a chair according to the invention illustrated in perspective, viewed respec¬ tively from the rear and obliquely from above and from the front and obliquely from above.

Fig. 3 shows the chair according to Fig. 1 in cross-section along the line 3-3 of Fig. 1. Fig. 4 shows a bow member of the chair frame re¬ presented schematically in an unloaded, in a partially loaded and in a heavily loaded position, illustrated respectively in full, broken and chain lines.

Fig. 5 shows the same as in Fig. 4 in three diffe- rent positions, indicating the user in the one, most forwardly tilted position.

Fig. 6 shows in perspective and partly in section

a part of the joint between a back and a bow member.

The chair as shown in Figs . 1 and 2 is con¬ structed of a framework 10 made of aluminium profiles and a seat member 11 with padding 12 and cover 13 and a back member with padding 15 and cover 16.

The framework is constructed of two substanti¬ ally U-shaped, mutually parallel bow member 17, 18 which are mutually connected by means of three trans¬ verse bracing members 19, 20, 21. A first bracing member 19 is fastened between the bow members 17, 18 just up under the seat member 11, and a second bracing member 20 is fastened between the bow members 1.7, 18 approximately at the centre of the middle portion of the U-shape, while a third bracing member 21 is fastened between the bow members 17, 18 just up under the back member 14. Each bracing member is secured to its respective bow member by means of a single fastening screw 22.

The bow members 17, 18 are designed with an approximately triangular shape. More particularly the U-shape has a lower web portion 2-3 which runs sub¬ stantially parallel to the floor. If necessary the bow members can form a supporting abutment against the floor only at the ends of the portion 23, since the portion 23 between the ends can run for example in an upwardly curved arc. From the one end of the web portion 23 the U-shape extends with a first, forward leg 24 obliquely upwards and backwards towards a second, rear leg 25 which extends correspondingly from the opposite end of the web portion 23 obliquely up¬ wards and forwards towards the leg 24. The leg 25 is somewhat longer than the leg 24 and projects a distance above the upper end of the leg 24. There is defined a considerable opening 26 between the legs 24 and 25, in a horizontal as well as in a vertical direction. The first, forward leg 24 is provided upper-- most with a horizontal, forwardly projecting seat-

OMPI

supporting portion 24a, while the second, rear leg 25 is provided uppermost with a back-supporting portion 25a directed obliquely upwards and backwards. The leg 24 forms together with the web portion 23 an S-shaped forward chair frame portion, while the leg 25 together with the web portion 23 forms a corresponding S- shaped rear frame portion. By means of the lower, rounded-off transition portions 24b, 25b and partly by means of the upper, rounded-off transition portions 24c, 25c together with the curved middle portion 23a of the web portion 23 there can be obtained an intended elasticity in the bow members 17, 18. In Fig. 4 there is illustrated in full, broken and chain lines the bow member 17 in an unloaded position, in a normally loaded position and in a heavily loaded position. By means of the rounded-off lower, forward transition portions 24b there can be achieved a controlled tilting to the different positions, as is shown by the broken and chain lines respectively in Fig. 5. In the illustrated embodiment the bow members 17, 18 are made of extruded aluminium profile with a strip- shaped, compact cross-section and with a breadth which can be for example approximately 15-20 times greater than the thickness. The application of other aluminium profiles, other metal profiles or plastic profiles or combinations of such can also be considered. Instead of a strip profile there can be considered for example a tubular profile. It is also possible to employ for example two profiles arranged by the side of each other. In the illustrated embodiment the profile has smooth outer surfaces, but there can also be considered pro¬ files with patterned outer and/or inner surfaces, in¬ cluding longitudinal projections and/or hollow sur¬ faces. The design of the bow members can confer diffe- rent rigidity and elasticity to the bow member and can in addition provide different design effects. The bow member fashioned of wood can also be considered and then

OMPI

especially laminated wood.

In Fig. 6 there is shown an embodiment for the fastening of the back member 14 to the bow member 17 and for securing the bracing member 21 to the bow member 17. The back member 14 can for example be made of aluminium, wood or another rigid material. On opposite sides the back member 14 is provided with two parallel- extending pins 27, 28 which are received in respective holes 29 of the inwardly facing edge portion of the bow member 17. There are shown a series (for example six items) of such- holes 29 in the bow member, and it is consequently possible to adjust the back member 14 in a number of different height positions relative to the floor and relative to the chair seat. The back member 14 is locked in position at a desired height position on the bow members 17, 18 by means of accompanying bracing member 21 and its associated fastening screws 22 (one at each end) . In the illu¬ strated embodiment there are fastened in two parallel-extending pins 30, 31 at each end of t ^' he bracing member 21, and the pins are adapted to be received in their respective associated holes 32 in the inwardly facing side of the bow member 17. Instead of the pins and holes illustrated there can be em- ployed if necessary other known guide and support means, and for example end edges of the bracing member can be designed reversely rounded-off to the side edge portion of the bow member or in another self-centering manner, so that unintentional movement of the bracing member and bow member is prevented after the fastening screw is fastened in position.

Correspondingly the possibility for regulation and correspondingly the possibility for fastening as shown for the back member can also be used for the seat member, so that the seat member can be adjusted into different horizontal distances from the back member, according to desire and need.

In the present case there are illustrated a back and a chair seat with a correspondingly narrow rein¬ forcing portion which is enclosed by a moderate padding and associated tight-sitting outer cover. The main object of said design is to obtain an accurately de¬ fined localisation of the seat-supporting portion and the back rest portion relative to each other. This design is determined first and foremost by the use characteristics of the chair. It is apparent that within the scope of the invention the design of the padding and the outer cover can be changed, so that one will get somewhat altered use characteristics and/ or changed characteristics of shape.

With the chair according to the invention the aim is to be able to permit a certain tilting of the chair in a forward direction and at the same time to provide for a lesser possibility for tilting of the chair in a backward direction. The chair is designed so that in a normal sitting position one sits in a relatively stable position with effective support for the seat portion and at the same time support for the lumbar portion of the user. The chair is, however, balanced so that by a displacement of the legs of the user and at the same time a leaning forwards of the upper part of the body of the user there can be effected a controlled tilting of the chair about the forward support portion of the under portion of the chair. In other words there can be effected in a relatively simple manner and without substantial exertion of force a controlled tilting of the chair in a direction forwards from the usual use position. During this tilting the same effective support of the seat portion and lumbar portion of the user has been retained the whole time. As a result there is the possibility of being able to use the chair as a work chair in various use positions with the upper part of the body of the user disposed at diffe¬ rent distances from a specific working area, for

OMPI

example a work table, at the same time as one obtains correct support for the lumbar and seat portions of the user in such different working positions. As a consequence of the intended balance position which is obtained with the construction of the chair illu¬ strated there will be required a considerably greater application of force in order to tilt the chair in a direction backwards from the usual use position.

As a consequence of the relatively large distance between the seat and back of the chair and the re¬ maining dimensions and fashioning of the chair, it is possible to place the chair in a somewhat tilted con¬ dition located in an inactive position on a table top, with the back rest placed on top of the table top and with the seat placed on the under side of the table top, so that easy cleaning of the floor space under and around the table can be effected.