A FURNITURE CHASSIS

Abstract: In a furniture chassis having a holding part such as a chair seat element (2) and one or more elongate con­ struction parts such as legs (6, 10) the construction parts are joined to the holding part (2) by means of conical end tenon portions (8) forced into correspond­ ingly conical holes (4) in the holding part (2). The tenon portions (8) are of pronounced non-circular cross sec­ tion, and they are conical from the full cross sectional contour of the construction parts (6, 10), thus without showing any shoulder portion abutting the outside of the holding part (2).

Description: A furniture chassis. This invention relates to a furniture chassis and particularly, though not exclusively, to a lightweight chair, stool or table. Such types of furniture normally have a central holding body, viz. a seat or a table plate element, to which a number of structural parts, first of all legs, are secured. As far as chairs are concerned even upstanding backrest members or backrest support members- should be considered as structural main parts, which should be very rigidly joined with the seat member. Up through the furniture history a wide variety of joining means and methods has been used and suggested, including sophisticated auxiliary means for providing reliable joints. Ideally, however, the joints should incluse nothing but the two parts to be joined, perhaps with the exception of some glue between them, and it is the purpose of the present invention to provide an improved joint of this ideal type. The invention is built on the old idea that a good joint is achievable when the structural element or construction part such as a chair leg is connected to the holding body by means of a simple tenon joint, whereby a protruding pin or tenon on the end of the construction part is forced into a receiving hole in the said holding body until the end or shoulder surface portion of the construction part around the root of the tenon engages the surface of the holding body around the tenon hole. This type of joint can be further improved by adding an amount of glue and/or by shaping the tenon and the tenon hole as conical elements. The known tenon joints, however, are not fully satisfactory, because they are after all sensible to rotary forces tending to twist the construction part relative the core portion thereof which is extended into the tenon, whereby the material may split longitudinally, and to rocking forces giving rise to a crowbar effect, whereby the joint is affected by a separation momentum about the outer edge of the said shoulder surface portion of the construction part. The latter effect is particularly actual when the construction part is joined to the holding body at a visible surface portion thereof, because the shoulder surface portion should then fit accurately against the surface of the holding body in order to avoid any visible gap of the joint. Besides, this requirement may complicate the shaping of the shoulder portion when the relevant surface portion of the holding body is non-planar. According to the invention the tenon joint is made as specified in the characterizing clause of claim 1, i.e. the tenon is constituted by the entire end portion of the construction part, without the same being abruptly reduced in thickness except that it is shaped slightly conically from its full thickness and is pronounced noncircular in cross section. By this construction the tenon will show maximum strength, and no crowbar effect can occur. The tenon and the tenon hole, of course, should be machined with good precision in order to define a desired entrance depth of the tenon, when no shoulder surface is present on the construction part. On the other hand, when the tenon fits snugly in the tenon hole there will be no visible groove in the joint irrespectively of the shape of the surface of the holding part. When made with a suitable small conicity the tenon will be to a high degree self locking in the hole, but the joint is well suited to be stabilized by means of glue. Because the cooperating surface portions are conical the insertion of the tenon will not result in any pronounced scraper action on the preapplied glue, i.e. the glue will remain effective and will not be liable to get displaced and collected as a collar about the visible root portion of the tenon. A joint according to the invention may show a remarkable strength and is particularly well suited for use in high quality furniture. It is a special advantage that the joint is usable on visible surfaces without special precautions or extra difficulties even when the relevant surface portion of the holding part is nonplanar, and the joint, therefore, is highly advantageous for use on the outer cylindrical surface of a chair seat or a table plate for the fastening of upper leg ends as provided with a laterally projecting tenon end. Such a peripheral mounting of the legs is normally a condition for the production of stackable chairs or tables. In the following the invention is described in more detail with reference to the drawing, in which: Fig 1 is a lateral view, partly in section, of a joint according to the invention, Fig. 2 is a plan view of the joint seen from below, Fig. 3 is a plan view thereof as seen from the left of Fig. 1, Fig. 4 is a perspective, partly exploded view of a chair showing joints according to Figs. 1-3, Fig. 5 is a perspective view of a number of stacked stools showing similar joints, and Fig. 6 is a sectional view of a modified joint. The joint illustrated in Figs. 1-3 refers to the chair shown in Fig. 4, this chair. having a seat with an outer annular seat frame 2, in which is'provided holes 4 for receiving the upper ends of a pair of front legs 6. As clearly shown in Figs. 1-3 each hole 4 is horizontally oblong and is slightly conical, while the upper 0 end of the leg 6 is bent through 90 and has an outer tenon portion 8 which is correspondingly conical and horizontally oblong so as to fit into the hole 4. The conical tenon portion 8 is made as a direct continuation of the leg 6, without any stepwise or abrupt reduction of the cross section thereof, i.e. without any shoulder being formed between the leg 6 and the tenon portion 8. Preparatory to the insertion of the tenon portion 8 into the hole 4 a suitable glue such as a so-called PVAC-glue is applied to the surfaces of both the hole and the tenon. As far as the binding between the surfaces is concerned it would be sufficient to apply the glue to one of the surfaces only, but the application of glue to both surfaces is extremely advantageous in connection with wooden surfaces, partly because a possible surface dust layer as resulting from the preparatory machining of the surfaces is hereby broken or caused to be effectively penetrated by the glue and partly because the wooden surfaces are caused to swell, whereby the mechanical self locking action between the conical surfaces is increased. In order to ascertain a rigid joint the tenon portion 8 should of course be forced into the hole 4 with a considerable pressure, and even in this connection the use of glue is advantageous, because it shows a lubricating effect which facilitates the intrusion of the tenon portion 8 into its final position in the hole 4. The chair shown in Fig. 4 has two rear legs 10 having upper extensions 12 which hold a backerest mem -ber 14. The upper ends of the extensions 12 are shaped as flat conical tenon portions 8 which are received in corresponding tenon holes 16, these holes being non throughgoing in the backrest member 14, whereby the holes should be made with a depth slightly larger than the final intrusion depth of the tenon portions 8. Even in Figs. 1 and 2 it is shown by a double dot and dash line that the hole 4 in the seat frame 2 may be non-throughgoing when the end of the tenon 8 is slightly spaced from the bottom of the hole. Ideally the tenon end should be forced at least lightly against the hole bottom, but this would require the conical surfaces to be prepared with an unrealistic high degree of accuracy. The accuracy shall be rather high anyway when or as it is a condition that the conical portions themselves define the entrance depth of construction part. The chair shown in Fig. 4 is made generally of laminated wood, which is particularly well suited, and the rear legs 10 are provided with a generally triangular middle block 18 serving as a core for a branched off portion 20 of the laminated wood, this portion being shaped endwise as a flat tenon portion 8 which is mounted in a conical hole 4 similar to the mounting of the front legs 6. Fig. 5 shows a pile of stools or tables 22 each having four legs corresponding to the legs 6 of Fig. 4. It has been emphasized that the tenon end portions of the construction parts should not be of any abruptly reduced cross section, but of course this applies to the more or less visible root portion of the tenon, while in some construction it could well be desirable to provide the free tenon end with one or more portions of reduced cross section as illustrated in Fig. 6. The invention primarily relates to wooden constructions, though other materials are in ho way excluded. Experiments have shown that a conicity of some 1:10 or generally between 1:5 and 1:15 should be preferred. By way of example, in a laminated beech construction a conicity of 1:10 and an insertion pressure of 250 kp have proved to result in a very strong and satisfactory joint. Many furniture constructions include parts or elements which are merely filler elements as distinguished from primary construction parts. Such filler elements, of course, may also be fastened in accordance with the invention, though the remarkable features and results of the invention are primarily related to the fastening of the said primary construction parts.

Claims: CLAIMS: 1. A furniture chassis having a holding body such as a chair seat frame (2) and elongate construction parts such as legs (6,10) projecting therefrom, said construction parts being endwise tenon joined with the holding body by means of an end pin (8) received in a tenon hole (4) in the holding body (2), characterized in that the end portion (8) of the construction part (6,10) is shaped with a non-circular cross section and is slightly conical from the full thickness or outer surface contour of the construction part.(6,10), said end portion (8) being held in a correspondingly large and conical hole (4) in the holding body (2). 2. A furniture chassis according to claim 1, in which the construction part (6) is of generally flat cross section and the end portion (8) thereof is planar conical on the opposed broad sides and semi circularly conical on the opposed narrow sides. 3. A chassis according to claim 1, in which the starting area of the conical end portion (8) of the construction part (6) is located substantially exactly flush with the front edge of the receiving hole (4) of the holding part (2). 4. A chassis according to claim 1, 2 or 3, in which the joint is additionally secured by means of glue between the conical surfaces. 5. A chassis according to any of the preceding claims, in which the construction parts (6,10) are made of laminated wood and are bent through ca. 900 immediately outside the joining area. 6. A chassis according to claim 5, in which the construction part (10) is extended beyond the bent end portion such that the said end portion constitutes a lateral protrusion (29) on a throughgoing construction ele ment (10,12). 7. A chassis according to claim 6, in which the construction element is a leg member of which the said lateral protrusion (20) is joined with a chair seat (2) or a table plate member, while the top end thereof is correspondingly joined to a backrest member (14) or another table plate member, respectively.

Inventors: OLESEN, FLEMMING
Applicants: MAGNUS OLESEN A/S
Application year: 1981
Main classification: F16B12
IPC codes: A47C7, A47C3, A47G9, F16B12