The invention relates to a chair which has a springy frame which swings when a sitting person leans forwards or backwards. More specifically, the invention re- lates to a chair which comprises a seat part provided with a seat and a back, as well as a springy frame part to which the seat part is attached pivotally such that the seat part is able to move forwards and backwards in a horizontal direction ac- cording to whether the sitting person leans on the back of the chair or whether the sitting person leans forwards, in which connection the chair is provided with a stopper for limiting motion.

In prior art there is known DE patent 369 907 which discloses a springy chair structure the frame of which swings such that the seat part moves in a horizontal direction when the sitting person leans forwards and, in a corresponding manner, said seat part moves in the opposite direction when the sitting person leans on the back. Limitation of the swinging motion has taken place in the arrangement ac- cording to the DE patent by using a separate spring element extending diagonally under the seat structure.

Close prior art is also disclosed in the application publication EP 0 775 457, which describes a chair the seat part of which tilts and moves forwards or back- wards, respectively, according to whether the sitting person leans on the back or whether the sitting person leans forwards on the chair. The frame of the chair is formed of parts attached pivotally to one another, and the frame is not springy in itself but it is provided with a separate spring element.

Further, prior art is represented by the application publication DE 44 28 244 which discloses a chair provided with a frame which is made of a tubular or rod- like material and which has a special articulation arrangement. The frame is fur-

ther provided with separate spring elements. The seat is attached to the frame di- rectly and rigidly.

With respect to the prior art closely related to the invention, reference is also made to the application publication EP 0 772 986 disclosing a chair which comprises a rigid and non-springy frame, which forms the legs of the chair. A spring mecha- nism has been fitted onto the frame, and a seat has been attached to the spring mechanism. The spring mechanism allows tilting of the seat according to how the sitting person sits in the chair.

Finally, with respect to the prior art, reference is made to the application publica- tion EP 0 906 738 disclosing a chair which is provided with rigid and non-springy legs, to which a seat has been attached by means of a pivot and spring mechanism.

Said mechanism allows tilting of the seat.

Our application discloses a novel type of chair design in which the chair also comprises a springy frame part. The frame part is advantageously made of a wire- like pliable material.

The frame is springy in a such way that, when leaning over a table, the chair swings such that the seat of the seat part moves backwards and, when the person sitting on the chair leans on the back of the chair, the frame of the chair swings such that the seat of the seat part moves forwards.

The seat part is attached by means of articulated joints to the springy frame part at two different pivot lines. When the chair is in a rest state, i. e. when no one is sit- ting on the chair, the articulated joints are advantageously situated in a plane which is slightly inclined relative to the horizontal, i. e. slightly obliquely. The front articulated joint/pivot line is situated lower in the vertical plane than the rear pivot line closest to the back.

A bottom plate is connected to the seat part by means of screws. The screws are passed through the articulation halves of the articulated joint, in which connec- tion, by tightening the screw, the articulation halves are connected to each other and the bottom plate of the chair, the articulation halves and the seat part are con- nected to one another. The articulation parts are situated between the seat of the seat part and the bottom plate, and each articulation half comprises cavity spaces which fit together and are placed around the crossbar of the frame part. Thus, the articulated joint is situated between the seat part and the crossbar of the frame part. The articulated joint is formed by means of two sleeve-like articulation halves. In accordance with the invention, one of the crossbars of the frame part, i. e. the rear crossbar, comprises a flat plate as a stopper of the swing of the frame, which flat plate projects forwards in a direction away from the vicinity of the back of the chair. The flat plate projects from the rear crossbar into a free space be- tween the bottom plate and the seat of the seat part and forms a stopper for limit- ing the swing of the frame.

The chair according to the invention is characterized in that the frame part of the chair comprises leg parts connected to each other at their lower end by means of horizontal connecting parts extending in the depth direction of the chair, which leg parts are connected to each other at their upper end by means of horizontal crossbars extending in the cross direction of the chair and forming two cross di- rection pivot lines which are parallel in the depth direction of the chair, the frame part being pivotally connected to the seat part through articulated joints disposed on said pivot lines with a stopper being arranged to limit the swing of the frame part and the pivot motion of the seat part relative to the pivot lines.

The invention will be described in the following with reference to some advanta- geous embodiments of the invention illustrated in the figures in the accompanying drawings, to which embodiments the invention is, however, not intended to be exclusively confined.

Figure 1A shows a chair from the front.

Figure 1B is a side view of the chair according to the invention as a sectional view taken along the line I-I in Fig. 1A.

Figure 1 C shows a detail from Fig. 1B.

Figure 2 shows the frame part and the seat part of the chair according to the in- vention separated from each other. The illustration is one of principle and sche- matic.

Figure 3 shows the frame part of the chair as a separate illustration.

Figure 4 is a sectional view taken along the line II-II in Fig. 3.

Fig. 1A shows a chair 10 having a springy frame according to the invention, seen from the front. Fig. 1B is a sectional view taken along the line I-I in Fig. 1A, and Fig. 1C shows a detail from Fig. 1B in the region of the frame 11 of the chair 10 and a rear pivot line X2 of a seat part 12. As shown in the figures, the chair 10 comprises a seat part 12 and a frame part 11 situated underneath the seat part and preferably made of a wire-like material. The frame part 11 is an integral whole which functions as a spring of the chair 10 owing to its structural springiness. The frame part 11 is mainly composed of upwardly extending leg parts flat, llal ("front legs"), lla2, lla2 ("rear legs"), horizontal crossbars lla3, lla3 connecting the leg parts at their upper end, and connecting parts 1 la5 1 la5 by means of which the leg parts lla], lla2 and flat, lla2 are connected to each other at the lower end. As shown in the figures, the horizontal crossbars l la3, lla3 extending in the cross direction of the chair connect the front legs 1 lal, 1 lal and the rear legs 1 la2, 1 la2 to each other, respectively, while the connecting parts 1 la5 1 la5 extending in the depth direction of the chair 10 connect the respective left and right front and rear legs 1 lai, lla)'and 1 la2, 1 la2'of the chair to each other, respectively.

Armrest frames l la4, l la4 are advantageously connected to the rear upwardly ex- tending leg parts 1 la2 and 1 la2', i. e. the rear legs, to which armrest frames separate armrests 11 c, 11 c"can be attached or are attached. However, the chair 10 can also be accomplished without said armrests and armrest frames.

The seat part 12 comprises the seat 12a proper and an associated back 12b. The seat part 12 is advantageously a continuous form-pressed veneer part made of one piece.

Figs. 1B and 1C show that the chair includes a separate bottom plate 13, which is attached to the seat 12a of the seat part by means of screws R under the seat part 12. Further, the structure of the chair includes articulated joints 14, of which each is composed of two articulation halves 14al, 14a2. Said articulation halves 14at, 14a2 are coupled to the frame part 11 of the seat around the horizontal crossbars l la3 and l la3', in which connection by passing the screws R through the articula- tion halves 14al, 14a2, through the seat 12a and the bottom plate 13, the bottom plate 13 and the seat part 12 attached thereto are connected to the frame 11 of the chair 10. In that connection, the horizontal crossbars 1 la3 and 1 la3 form two cross direction pivot lines Xi, X2 in parallel relationship in the depth direction of the chair 10, the frame part 11 being pivotally and in a spring-like manner connected to the seat part 12 through the articulated joints 14 disposed on said pivot lines.

As Figs. 1B and 1C show, a free space D remains between the bottom plate 13 and the seat 12a of the seat part 12. A stopper 15 for limiting motion, formed of a visor-like and plate-shaped structural part, is attached to the rear horizontal cross- bar 1 la3 of the frame part 11, which stopper will be situated in said free space D between the bottom plate 13 and the seat 12a of the seat part 12. The stopper 15 is most preferably welded to the crossbar 11 a3'such that said attachment is rigid.

Thus, the springiness of the frame part 11 and the attachment accomplished by means of articulated joints between the frame part and the seat part 12 enable a mainly horizontal and tilting motion of the seat part 12. When the seat part 12

moves in a horizontal direction when the frame part 11 swings while the sitting person tilts the frame part 11, the stopper 15 comes into contact with the struc- tures beneath the seat part 12 and limits the swing motion of the frame part 11.

Thus, the visor-like and plate-shaped stopper 15 functions as a stop part and as a backing part in extreme swing situations, whereby the swinging of the frame part 11 is controlled and limited.

The chair structure according to the invention operates such that, when the person sitting on the chair leans forwards, for example, at a table, the seat 12a of the seat part 12 moves backwards and when the person sitting on the chair leans on the back 12b, the seat 12a of the seat part 12 moves forwards, respectively. The for- ward movement is denoted with arrows Ll and the backward movement with ar- rows L2. The stopper 15, advantageously a visor-like and plate-shaped structural part extending into the free space D between the seat 12a of the seat part 12 and the bottom plate 13, functions as a means for limiting the forward and backward movement of the seat 12a of the seat part 12 of the chair and thereby the swing of the frame part 11. In one stop position, the stopper 15 comes into contact with the bottom surface of the seat 12a of the seat part 12 and, in the other stop position, the stopper 15 comes into contact with the bottom plate 13. The stopper 15 is fixed to the rear crossbar 1 la3'.

In Fig. 1B, the chair is in its rest position. In the rest position, the stopper 15 is not in contact with anything (Fig. 1C illustrates the rest position). In the rear position, i. e. when leaning backwards, the stopper 15 comes into contact with the bottom plate 13. In the forward position, i. e. when leaning forwards, the stopper 15 comes into contact with the seat 12a of the seat part 12, advantageously, the seat veneer.

The rocking motion forwards is preferably smaller than the rocking motion back- wards.

Fig. 2 shows an exploded view of the seat part 12 and its bottom plate 13 as well as of the articulated joints 14. The illustration is schematic. There may be one or more articulated joints 14 in one pivot line Xi, X2. In the embodiment of the fig-

ures, there are four articulated joints 14, i. e. there are two articulated joints 14 in each pivot line Xi and X2.

Fig. 3 is a separate illustration of the frame part 11 of the chair. The frame part 11 comprises the leg parts I I a I and 11 as well as lla2 and lla2 extending mainly upwards, i. e. the front legs l lal and l lal and the rear legs l la2 and l la2, the hori- zontal crossbars lla3, lla3 connecting these leg parts on top, as well as the con- necting parts lla5, lla5'extending in the depth direction of the chair and connect- ing the leg parts l lai and 1 la2 as well as l lai'and 1 la2'to each other at the bottom.

Armrest frames l la4, l la4 are advantageously connected to the rear upwardly ex- tending leg parts l la2 and 1la2', i. e. the rear legs l la2 and l la2, to which armrest frames separate armrests 11 c, 11 c'can be attached or are attached. However, as already previously stated, the chair 10 can also be accomplished without the arm- rests and armrest frames.

The entire frame part 11 is an integral whole, which, made of a wire-like material, is manufactured such that one"half'of the frame is first bent out of a wire, which half comprises an armrest frame 1 la4, a rear leg part 1 la2, a connecting part 1 la5, a front leg part l lal, and half of a front crossbar l la3. In a similar manner, the other "half'of the frame is made of an armrest frame l la4, a rear leg part l la2, a con- necting part l la5, a front leg part l lal, and half of the front crossbar l la3. The armrest frames are advantageous, but not necessary from the point of view of the invention. After that, the halves of the frame are welded to each other at the halves of the front crossbar l la3 and, further, the rear horizontal crossbar l la3 is welded between the rear leg parts lla2 and lla2. In that connection, the entire frame 11 functions as the spring of the chair owing to the springiness of its structure.

Fig. 4 is a sectional view along the line 11-11 in Fig. 3. The stopper 15 for limiting motion is a visor-like and plate-shaped structural part, which is joined to the crossbar l la3 most advantageously by welding.