The present invention relates to a joint for use in the assembly of furniture, transport containers, cupboards, wall structures, ductworks, etc., the joint comprising a projection provided with joint means, and a recess having grooves corresponding to the joint means.

Prior art includes dovetail-joint type groove joints having a single "pair of flanges" or the like, which are used e.g. in the furniture industry. Other joint types used in furniture or for joining struc¬ tural members are disclosed e.g. in FI 49 450, GB 2 180 741 A, GB 1 550 404, DE 2 436 439, DE 3 405 862, CH 634 372, and US 4 261 148. These patent documents disclose a variety of joint pieces and joint systems used in assembling furniture, walls or structural members. These differ from the solution of the present invention, being very complicated, difficult and ex- pensive to use and realize or suitable for one spe¬ cific use only, in addition to which they withstand no high loads relative to the material used.

The object of the present invention is to avoid the drawbacks of the prior art and to provide a new simple solution easy to realize.

The invention is based on the idea that the joint has to be easy to use, durable, simple to manu¬ facture, and as versatile as possible in use.

More specifically, the joint according to the invention is mainly characterized in that the projec¬ tion of the first piece of the joint comprises at least two pairs of joint means arranged on its opposite sides, the joint means being fitted in the grooves provided in the recess of the second piece. In the joint of the invention the joint means

are positioned symmetrically on both sides of the central axis of the projection. Preferably, the joint means are flanges having outer edges bevelled in parallel with the edges of the projection. It can be shown through calculation that the angle between the edge line and central line of the projection preferably varies in the range from 0 to 45°.

In certain cases, it is important in a struc- tural unit assembled by using the joint that the members or walls can be turned relative to each other. For instance, if desired, the transport box bodies of lorries can be made foldable by the joint, or their size can be varied as required when a flexible joint is used. In such a case, the joint is made of an elastic material or provided with a hinge mechanism to allow it to be bent.

The joint piece can be made very versatile by placing one or more projections and/or recesses with joint means in one and the same piece. The shape of the joint piece may also be varied, thus obtaining a variety of pieces having a fixed angle of installa¬ tion.

The joint is provided with a sealing tape when the joint solution is used in structures which should be dust, gas or liquid tight.

Other embodiments of the invention are described in the attached claims.

The invention offers a number of major advant- ages. The joint allows a structure or structural unit of almost any kind, shape and size to be formed, where the joint is used as a structural member. The joint withstands considerable perpendicular forces and torques. The joint can be of different materials. It can

be made of metal, plastic, wood, mineral, or the like, e.g. by milling, casting into a mould, die-casting, such as slip casting or extrusion, or simply by press¬ ing the material into a desired shape. The joint can be used to join materials dif¬ ferent from each other, such as plastic and wood or laminated sheet urethane and steel, in a rigid or hinged manner. When e.g. chairs and tables or trans¬ port containers are produced, the joint is rigid and firm. The joint is easy to disassemble and assemble frequently. If required, however, it can be e.g glued, which makes it permanent.

The joint can be used to manufacture e.g. furni¬ ture for homes, offices and industry, or thermally insulated transport containers and box bodies for lorries and delivery vans. It can also be used in In situ building of a prefabricated insulated garage and in the construction of insulated ducts and pipes where insulation material itself is made self-supporting at by joint so that no further support is needed.

As compared with the joining techniques present¬ ly in use, the joint offers clear advantages. It can be made by a method best suited for the existing equipment of the factory, such as milling or extru- sion. The joint production method is also advantageous in costs. Finished products can be stored and trans¬ ported in parts, which reduces the storage and transport costs considerably. A product assembled by using the joint can also be frequently disassembled and assembled without any special tools.

Pieces can be installed in very small spaces. By notching the grooves in the recess of the counterpart, the joint piece having a projection can be installed in the recess with a very short installation distance. If required for secure attachment, several joint

pieces can be provided in the recess.

Considerable savings in the cost of labour and materials are achieved by the prefabrication of ele¬ ments provided with the joint, and the building can be speeded up. Particularly renovation requires products the production and installation of which provides suf¬ ficient dimensional flexibility. The joint according to the invention can be produced at any desired angle, such as 90°. It may also be machined in situ directly in elements or materials to be joined by hand-operated tools.

When the joint according to the invention is used in the assembly of structures, no joint pieces made of other materials, no glues and no tools are required in installation.

In the following the invention will be described more fully with reference to the attached drawings, where

Figure 1 is an axonometric view of a groove joint before installation;

Figure 2 is a sectional view of a male joint piece;

Figure 3 is a sectional view of a female joint piece; Figure 4 is an end view of a structural member formed by a joint piece of 90°;

Figure 5 is an end view of a structural member formed by a joint piece of 45°;

Figure 6 is an end view of a joint piece with installation angles of 180° and 45°;

Figure 7 shows a joint piece allowing angles varying steplessly between 180° and 0°;

Figure 8 shows a joint piece made of a soft elastic material and allowing angles varying stepless- ly in the range 0° - 180° - 0°.

In the embodiment shown in Figures 1 to 4, the joint is shown before installation; the male or female piece is pushed on the other joint piece from the end. In Figure 1, the male joint piece is inserted into the female joint piece. The joint shown in the figure can be used in this way e.g. in assembling ventilation ducts from polyurethane sheets. Even with a material as fragile as polyurethane, the joint will have a suf¬ ficient breaking strength without any accessories. Figure 2 shows a male joint piece where three pairs of joint means 2, 3 and 4 are formed in a pro¬ jection or tongue 1. The outer edges of the joint means or flanges are bevelled so as to follow the trapezoidal shape of a line A defined by the outer edge of the projection. The possible inclination of the edge line A of the projection relative to its central line B is determined by a material used. The thickness and height of the flanges 2, 3 and 4 as well as the width or position and shape of grooves 5, 6 and 7 between the flanges are determined on the basis of strength calculations.

Figure 3 shows a female joint piece where a recess 9 with grooves 10, 11 and 12 is machined so as to correspond to the joint means of the male tongue. Figure 4 is an end view of a structural member achieved by a joint piece of 90°. The joint piece is used in the manufacture of e.g. pipes, ducts, furni¬ ture, containers, and a variety of other structures. Figure 5 in turn shows an end view of a structural member for the same use; this member is achieved by a joint piece of 45°.

Figure 6 is an end view of a joint piece that can be installed at an angle of 180°, 90° and 45°. The joint piece is used e.g. as a corner column for walls. The angles of 180° and 45° are installed in the joint

piece.

Figure 7 shows a joint piece made of e.g. plastic which allows stepless variation of instal¬ lation angles in the range between 180° and 0°. The joint piece is hinged at its edge. It is used in exposition structures or other structures that require movability and certain kind of flexibility.

Figure 8 shows a joint piece made of a soft elastic material which allows stepless variation of angles in the range 0° - 180° - 0° to allow folding of the containers of lorries without impairing thermal insulation.

The invention is not limited to the disclosed embodiment nor to the use described above, but a wide variety of modifications are possible within the inventive idea defined in the attached claims. Accord¬ ingly, the joint means of the joint may be positioned stepwise or otherwise asymmetrically on both sides of the central axis of the projection. The joint means may be of some other shape than the flange shape.

Joint surfaces or separate joint pieces used in the joint can be made of a material having a higher strength than the structure to be joined. For in¬ stance, a joint piece may be made by die-casting from aluminium and provided with an urethane filling. Such a joint piece can be used e.g. in the manufacture of box bodies and containers for lorries.

Joint pieces can be hinged or articulated in different ways. By varying the position of the hinge point and the shape or state of being of the bodies to be joined, the joint can be turned steplessly through 360°. Such different joint pieces and embodiments can be used e.g. in the industry to replace glues, pop rivets, rivets, nails, screws, partially welding, and hinges and other articulations; a soft joint piece,

for instance, allows the hinge to move and gives it rigidity, being nevertheless thermally insulated.