Chair

The seat (1) and the back (2) are identically shaped shells (12) having side supporting ribs (10, 11). With the exception of the portion intended for connection to the other part, the supporting ribs are in the form of channels (13) open at the bottom. The remaining portion is in the form of a hollow cylinder (15) having a partition (17). The connecting members (3, 4) disposed on both sides consist of bent-over spring material (30) in band form. The ends (33, 34) of the arms (31, 32) of the connecting members are integrally fastened in slots (35, 36) in cylindrical pegs (37, 38) by means of screws (39, 40). The pegs (37, 38) are produced with snug fit tolerance in relation to the hollow cylinders (14, 15). An O-ring (40, 41) is compressed by means of a screw (44, 45) between the partition (16, 17) and the peg (37, 38). This provides adequate fastening of the connecting member even when thin-walled moulded polypropylene is used for the shells (12). The chair legs (5-8) can then be fastened in the channels (13), likewise by means of a clamp device, similarly to the arrangement described for the pegs. This permits rational manufacture and stockkeeping.

The present invention relates to a chair having a seat and a back. 
Chairs are known in which the region of resilient pivoting of the back 
relative to the seat permits adjustable resilient pivoting, optionally 
also from a selectable normal position. 
In Swiss Patent No. A 472 198 a rocker member is accordingly held for 
pivoting about a horizontal pin mounted on the seat, against the action of 
a coil spring fastened on the seat, and a backrest carrier is mounted on 
this rocker member in such a manner as to be adjustable in height and also 
pivotable. Not only is an arrangement of this kind very extravagant in the 
use of material, but it also entails considerable expense for labour for 
the production of the component parts and also for assembly, so that the 
very comfortable chair becomes correspondingly expensive. 
In an arrangement according to Swiss Patent No. A 625 688, the seat and the 
back are joined together only in their edge portions, without a backrest 
carrier. The connection is resilient, so that the back can be pivoted 
relative to a side frame support joined to the seat. The back is provided 
with a padded portion, which is likewise mounted for pivoting relative to 
the back. Both joints have spring means, so that a force must be applied 
in order to pivot the parts in relation to one another. 
In a first embodiment the spring means comprises a coil spring which is 
supported on one part and pulls into a socket a pin provided with an 
arched head. The two parts are pivotable about a pivot axis lying outside 
this joint arrangement, so that a restoring force is provided when they 
are swivelled out of a normal position. 
In a second embodiment two resilient parts of plastics material are 
inserted into the divided frame supports and, within a limited pivoting 
range of a rotatably mounted pressure plate, apply a restoring force to 
the latter when the back is pivoted out of the normal position. The double 
joint permits the support of the user's back and neck part, with his body 
in a relaxed position. In this example also a frame consisting of a 
multiplicity of component parts is provided for fastening the seat and the 
back, so that a chair of this kind can be produced only at a high price. 
A substantial simplification is proposed in Swiss Patent No. A 611 502. 
Between the seat and the back, each of which constitutes a self-supporting 
element, is disposed a connecting member which through its shape acts as a 
spring. The connecting member, the seat and the back are integrally joined 
together. Suitable materials are wood, metal, plastics, alone or in 
combinations. A chair of this kind is naturally very inexpensive to make, 
because it can be produced by stamping, or in the case of sheet metal by 
pressing. Owing to the fact that it is possible to make the seat, the back 
and the connecting member out of the same material, unspecified means must 
be provided, on the one hand, for providing the connecting member with 
soft elasticity, and on the other hand for making the seat and the back 
rigid. 
In contrast thereto the invention seeks to provide a chair in which the 
seat and the back are each inherently stable or rigid and are resiliently 
joined together by connecting members, without an additional frame being 
required for fastening the seat and the back.

The chair shown in FIG. 1 consists of the seat 1 and the back 2, which are 
in the form of shells of identical shape, and of two connecting members 3, 
4 for the elastically resilient connection of the seat 1 and the back 2. 
In addition, the legs 5-8 are fastened on the seat 1. The two identically 
shaped shells for the seat 1 and back 2 are provided at the sides with two 
supporting ribs 10, 11 and a plate 12 situated between these supporting 
ribs 10, 11. The plate 12 is depressed in the centre as a shaped seat, and 
the portion 13 projecting beyond the supporting ribs 10, 11 is convexly 
curved, so that in the case of the seat the edge lies under the seat 
surface and in the case of the back the edge lies behind the support 
surface. The chair legs 5-8 are inserted into and fastened to the 
supporting ribs 10, 11, as will be described further later on. The 
connecting members 3, 4 are also inserted into the supporting ribs 10, 11. 
The construction of the supporting members 3, 4 and their fastening in the 
supporting ribs are illustrated on a larger scale in FIG. 2. With this 
type of fastening it has been taken into account that the shells consist 
of polypropylene, which has only limited mechanical strength and in which 
therefore screw connections clamping a wall part of polypropylene between 
a screw head and a plate-like part of another rigid material, such as for 
example the chair legs, would break up unless wall thicknesses 
corresponding to the forces involved were used, thus entailing additional 
material. 
The connecting members 3, 4 consist mainly of a spring member 30 in band 
form, which is bent so that the two arms 31, 32 of approximately equal 
length form an obtuse angle of at least approximately 100.degree.. The 
ends 33, 34 of these arms 31, 32 are inserted into axial slots 35, 36 in 
cylindrical pegs 37, 38 and rigidly fastened by means of screws 39, 39', 
which pass through the arms and are screwed into the opposite side of the 
slot 35, 36. The portion 41 between the two pegs 37, 38 is integrally 
foamed polyurethane for protecting the user and the spring member 30 and 
in an esthetically attractive manner may be identified as a spring member 
by beads extending around it. 
On the other hand, the channels 12, 13 of the supporting ribs 10, 11 are 
formed in the end portions as cylinders 14, 15 closed at one end. In the 
closure wall 16, 17 of the cylinders 14, 15 respective holes 18, 19 are 
provided. 
The inside diameter of the cylinders 14, 15 and the diameter of the pegs 
37, 38 are dimensioned for a snug fit, so that the pegs 37, 38 can be 
pushed into the cylinders 14, 15. The pegs 37, 38 are fastened in the 
cylinders 14, 15 by means of O-rings 40, 41 of resilient material which, 
as shown in FIG. 2, are laid around a cylindrical guide 42, 43. With the 
aid of a screw 44, 45 screwed axially into the pins 37, 38, the pins 37, 
38 are pulled against the closure wall 16, 17, so that the O-ring 40, 41 
is compressed and thus pressed against the wall of the cylinder. This 
fastening is sufficient to join the two parts of the chair, the seat 1 and 
the back 2, rigidly together. 
Experiments have shown that wall thicknesses of 4 mm are sufficient for the 
cylinders, in order to take the forces occurring when polypropylene is the 
material used for the shells of the seat and back. In the dimensioning of 
the spring members 30 it was assumed that the spring members, loaded with 
a force of up to 15 kilograms at a point 30 cm above the seat, are rigid 
and that in the range between 20 and 25 kg they are resilient, and further 
that they have a strength under continuous load of 35 kilograms. 
FIGS. 3 and 4 show two modifications of the type of fastening described 
above for securing the pegs 37, 38 in the cylinders 14, 15. In each case 
only the fastening on the seat 1 is shown, the fastening on the back 2 
being identical, as is also clear from FIG. 2. 
On the end surface of the peg 38 lies a disc 49 of resilient material, 
which has a central hole. The outside surface of this disc 49 is covered 
by a washer 48, and a screw 47 serves to compress the resilient disc 49, 
which thus serves the same function as the O-rings 40, 41. The head of 
this screw 47 is accessible through an opening 19 formed in the partition 
17 and closed by a stopper 46. 
The arrangement shown in FIG. 4 differs from that just described only in 
that the disc 49 is replaced by a ring 50 of rectangular cross-section, 
and also in that the peg 38 is provided, similarly to the arrangement 
shown in FIG. 3, with a cylindrical guide, which at the same time also 
limits the depth to which the screw 47 can be screwed in. 
FIGS. 5 to 7 show a first application of the seat-back arrangement 
described to a chair and to an armchair provided with armrests. Here again 
the problem described above of the strength of polypropylene arises, and 
neither chair legs nor armrests can be screwed in the usual manner to the 
shells by screw connections. In FIG. 7 the channel 13 in the rib 11 of the 
shell 12 is shown clearly and to a larger scale, while FIG. 6 shows the 
rib 11 and the shell 12 in side view. As can be seen from these Figures, 
the two front chair legs 60, 61 have bent-over supporting parts 62 
engaging in the channel 13. In this channel there are provided, for 
example, two eyes 63, 64, of which the rear eye 64 is clearly shown in 
FIG. 7. At the side of the eyes 63, 64 there is just sufficient room for 
the supporting part 62, so that the latter is pressed by means of a 
resilient disc 65 and a screw 66 against the outer wall of the channel 13, 
and is thus fastened. Here again one of the three arrangements shown in 
FIGS. 2 to 4 may be used. 
The rear chair legs 67, 68 are joined together by means of a cross bearer 
69. This cross bearer 69 is welded on the one hand to these rear chair 
legs 67, 68 and on the other hand to the supporting parts 62 of the front 
chair legs 60, 61. 
The armrests 70 are pushed by means of an inserted part 71 into the rear 
chair legs 67, 18 and are fixed by means of a screw 72. Without these 
armrests, the opening in the rear chair legs can be blanked off by means 
of a plug of plastics material. As FIG. 5 shows, the rear chair legs 67, 
68 are offset in the outward direction. This serves the purpose of 
enabling the chairs or armchairs to be stacked one on the other, as all 
specialists in the art will readily realise. 
Another application, namely to an office chair, is illustrated in FIGS. 8 
to 10. For the purpose of fastening the pillar 80 with the star-shaped 
arrangement of radiating arms and with the adjusting device 82, screws 84 
are provided in the usual manner on a rigid underframe 83. As FIG. 10 
shows, this underframe is in the form of a bearer construction suspended 
on both sides and comprising band-like bearers 85 fastened on retaining 
rails 86. The retaining rails engage in the side ribs 10, 11 of the shell 
12 and are secured by clamp means, such as a washer, on an eye 88, the 
washer being compressed by a screw 89. The dimensions of the retaining 
rails 86 are so selected that between their outer face and the wall of the 
channel a space is left. A cover hood 90 can be inserted into this space 
of 3 to 4 mm, in order to protect the adjusting device 82 against dirt. 
Armrests 91 may be constructed with a cantilever arm 92 and can be screwed 
from the outside to the retaining rails 86 by means of two screws 93, 94. 
Through the abovedescribed construction of identically shaped shells for 
the seat and the back, it is possible to manufacture chairs, armchairs, 
and office chairs as mass produced articles, so that manufacture is 
substantially less expensive than was possible hitherto. The combination 
of seat and back can in addition be kept in stock as prefabricated 
products and the desired type of chair leg, with or without armrests, can 
then be screwed on by a simple operation in accordance with the 
purchaser's wishes.