FR2520068A1 - Fixing together wooden components of furniture without glue - by cementing with polyurethane foam injected between wood and removable former - Google Patents

Abstract

The components to be assembled are located against the internal surface of a supporting cavity. A central core piece is placed in the cavity to leave an empty space between the core piece and the wooden components. A plastic foam, pref. polyurethane is injected into the space to fill it before polymerisation. The expansion of the foam is powerful enough to key the foam microscopically into pores of the wood. The supporting cavity is pref. profiled to mat the contours of the located components.

Description

 For the manufacture of a wooden part, piece of furniture, panel or similar, it is necessary to use wood of considerable thickness to allow the realization of assemblies, tenons and mortises - grooves and tongues swirling - added tongue - gluing, fixing by points or staples. The rigidity of the part is related to the thickness of the elements used.

 The assembly produced is likely to undergo relatively large deformations as a function of hygrometric and climatic variations.

 On the other hand, shocks can cause relatively large deformations on the assemblies, this during handling and transport.

 The present invention relates to a glue-free, non-deformable, waterproof gluing process.

 This assembly system eliminates tenons, mortises, grooves, tongues, trunnions, added tabs, gluing, fixing with spikes or staples as well as all traditional assembly systems.

 It essentially consists in placing the pieces of wood to be assembled in a counterform matching their external outline and in introducing a mold leaving an empty space between mold and pieces to be assembled, then injecting into this space a cellular foam, polyurethane foam by example until polymerization.

 The rigidity of the assembly is provided by the injection of cellular foam which is distributed homogeneously in the volume which is reserved for it.

 The assembly is therefore carried out by an expansion of the foam inside a volume which is constituted by the elements to be assembled and a counter-form.

 On the surface of the pieces of wood in contact with the foam, the microscopic migration in the pores of the wood will allow a fixation on the whole surface in contact thus realizing a monobloc assembly between the different pieces of wood and the foam.

Cellular foam has two functions - a rigidity due to its composition which is likely to
vary according to the desired resistances, - a "bonding" thanks to its expansion and its migration microphones
copic.

 The assembly thus produced will therefore be in one piece. The addition of stable and insensitive material to hygrometric and climatic variations makes it non-deformable and waterproof.

 The assemblies thus produced will have better impact resistance.

 An advantage of this process is that it allows the use of materials, such as wood, which are thinner than that required by conventional processes.

 The shape of the pieces of wood is arbitrary and it suffices to adapt the counter-forms to it.

 We can thus inexpensively carry out the most diverse assemblies, such as for example chests, furniture, panels etc.

The production of trunk panels will be described below by way of an indicative and in no way limitative example, with reference to the appended drawing in which
Figure 1 is a front view of the trunk.

 Figures 2 and 3 are sectional views along the line IILII and Figure 1 of the panel running and finished.

 The trunk taken here by way of example comprises molded panels 1 with corner crosspieces 2 and top and bottom plates 3, the latter resting on the feet 4.

 The panels 1 with their moldings 5 and the crosspieces 2 are applied against the internal face 6 of the counterform 7 and the mold 8 is placed inside (fig. 2): cellular foam 11 is introduced by the filling orifice 9 in the empty space 10 formed between mold and counter-form.

This is distributed homogeneously with microscopic migration in the pores of the wood (fig. 3), ensuring after polymerization a rigid monobloc assembly.

 It is understood that this assembly process is applicable to all kinds of wood pieces, of any shape and size, and removes tenons, mortises, points, nails, staples etc.

Claims (3)

- CLAIMS  1. A method of assembling pieces of wood for the manufacture of furniture, panels and the like, characterized in that the pieces are applied to the internal surfaces of counterforms (7) while a central mold (8) is put in place so as to reserve an empty space (10) between mold and counterforms, and in that a cellular foam (11) is injected into this space until filling it before polymerization.  2. Method according to claim 1, characterized in that the internal face of the counter-forms (7) is homothetic to the external contour of the pieces of wood.  3. Method according to claim 1, characterized in that the foam expansion is pushed to microscopic migration in the pores of the wood.