EP3744492B1 - Method for manufacturing multi-layer solid wood panels - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of the production of wood panels intended in particular for wood processing industries, carpentry for example, with a view to manufacturing objects such as furniture or other fitting-out or decoration products. decoration. In its greater thicknesses, the product obtained can form a structural construction element.

An object of the invention is to allow the production of solid wood panels in a wide range of thicknesses.

STATE OF THE ART

The manufacture of multilayer panels based on wood sheets is known per se. Since the second half of the 19th century, plywood panels have been manufactured in particular, according to different compositions, offering uses mainly for the construction industry.

According to the AFNOR NF EN 313-2 standard, a plywood panel is a wood-based panel obtained by gluing adjacent layers with crossed wires, usually at right angles. More precisely, the plywood panels are an assembly of sheets of wood obtained by peeling or by slicing, these sheets being generally designated by the term of plies, said plies being glued to each other under pressure. For example, the document CN 1057723 C presents a method of manufacturing such a plywood panel.

We currently manufacture plywood panels consisting of five sheets, with a central ply, called core, surrounded on either side by two interior plies, the outer plies being designated respectively face (or facing) and backface (or backing). The interior plies or the exterior plies can be composed of several joined or juxtaposed plies.

The exterior plies may consist of one or more decorative wood veneers sliced or peeled to form decorative plywood panels.

Certain disadvantages of known plywood panels lie in their perceived low quality and in their often great thickness. Indeed, the outer layers (facing and backing) are generally a few tenths of a millimeter thick and the total thickness of the panels generally reaches 20 mm to 30 mm, up to 50 mm.

In practice, today, the actors of the first transformation of wood, from trees and rough logs to the sawn solid wood panels, are unable to provide panels with sections adapted so that the actors of the second and the third transformation of wood, namely the manufacturers of objects and furniture, planers, moulders, etc., can practice their art in good conditions. In particular, in Europe, the use of species of oaks or of North European conifers does not make it possible to have large-width slabs for carrying out these second and third transformations.

As a result, the state of the art provides, for these actors of the second and third transformations of wood, the plywood panels briefly described above, or particle boards, rich in glue, high density particle boards or so-called reconstituted wood panels.

There is therefore a need for an end-to-end manufacturing process making it possible to produce solid wood panels, in particular of great width and including of low thickness, of small or of great length, and of high aesthetic quality.

To this end, there is provided a method of manufacturing multi-layered solid wood panels, from thin veneers of solid wood glued to each other so that the wood fibers of adjacent veneers bond together.

PRESENTATION OF THE INVENTION

• l'écorçage de grumes de bois, notamment ayant un diamètre supérieur à 30 cm, de préférence ayant un diamètre compris entre 80 cm et 110 cm ;
• le premier tronçonnage des grumes de bois écorcées pour former des billons, de préférence ayant une longueur égale à un multiple entier d'une longueur comprise entre 120 cm et 135 cm ;
• l'étuvage desdites billons ;
• le déroulage des billons après étuvage, pour former des placages de bois massif ayant une épaisseur comprise entre 1 mm et 10 mm, de préférence comprise entre 1,5 mm et 4,5 mm, de façon encore préférée égale à 3,2 mm ;
• la pré-coupe de fibres de bois, dans lesdits placages de bois massif, dans des portions sur lesquelles lesdites fibres de bois sont tendues ;
• le séchage continu des placages de bois massif ;
• le tri manuel ou automatique des placages de bois massif en fonction d'au moins un critère de qualité visuelle, pour former une première catégorie de placages destinés à constituer des couches externes des panneaux de bois massif multicouche et une deuxième catégorie de placages destinés à constituer des couches internes des panneaux de bois massif multicouche ;
• la réalisation d'assemblages de placages de bois massif par :
• encollage de faces de placages à assembler, notamment par de la colle vinylique ;
• composition d'assemblages de placages comprenant une pluralité de placages de bois massif disposés l'un contre l'autre, faces encollées respectives en vis-à-vis, de façon à être collés, chaque assemblage de placages comprenant un placage de première catégorie pour chaque couche extérieure et, le cas échéant, un ou plusieurs placages de deuxième catégorie comme couches intérieures, chaque assemblage de placages comprenant de préférence entre 2 et 16 couches ;
• pressage des assemblages de placages pour former des panneaux de bois massif multicouche.

More specifically, the invention relates to a process for producing multi-layered solid wood panels comprising the following steps:

• debarking of wooden logs, in particular having a diameter greater than 30 cm, preferably having a diameter of between 80 cm and 110 cm;
• the first cutting of the debarked logs to form logs, preferably having a length equal to a whole multiple of a length between 120 cm and 135 cm;
• steaming of said logs;
• the unwinding of the logs after steaming, to form solid wood veneers having a thickness between 1 mm and 10 mm, preferably between 1.5 mm and 4.5 mm, more preferably equal to 3.2 mm;
• pre-cutting wood fibers, in said solid wood veneers, in portions over which said wood fibers are stretched;
• continuous drying of solid wood veneers;
• manual or automatic sorting of solid wood veneers as a function of at least one visual quality criterion, to form a first category of veneers intended to constitute outer layers of multi-layered solid wood panels and a second category of veneers intended to constitute internal layers of multi-layered solid wood panels;
• the production of solid wood veneer assemblies by:
• gluing of veneer faces to be assembled, in particular using vinyl glue;
• composition of veneer assemblies comprising a plurality of solid wood veneers arranged one against the other, respective glued faces facing each other, so as to be glued, each veneer assembly comprising a first category veneer for each exterior layer and, optionally, one or more second class veneers as interior layers, each veneer assembly preferably comprising between 2 and 16 layers;
• pressing veneer assemblies to form multi-layered solid wood panels.

According to one embodiment, the wood fibers of each solid wood veneer having a direction, in other words an average orientation, the solid wood veneers are glued to each other two by two so that the directions of the fibers of each of said veneers are parallel throughout the veneer assembly.

Advantageously, the method also comprises a second cutting step, after the steaming step, to form logs having a final length of between 120 cm and 135 cm, the first cutting resulting in forming logs having a length equal to an integer multiple greater than or equal to 2 of said final length of said logs.

Advantageously, the method further comprises, at the end of the pressing step making it possible to form solid multilayer wood panels, a step of edging the multilayer solid wood panels to give them a substantially parallelepipedal shape.

Advantageously, the method comprises, after the edging step, a sanding step to improve the surface quality of said multi-layered solid wood panels.

Advantageously, the method comprises, after the sanding step, a cutting step to form multi-layered solid wood panels having the desired final dimensions.

Advantageously, the method further comprises, before the continuous drying step, a trimming step, to form veneers having the desired dimensions.

Advantageously, the method further comprises a step of painting the multilayer solid wood panels and / or a varnishing step of the wood panels. multi-layered solid wood and / or a custom cutting stage on the multi-layered solid wood panels.

An advantage of the process according to the invention lies in the fact that the multi-layered solid wood panels thus produced have a solid wood appearance: strata are not seen because the wood fibers of adjacent veneers glued together are connected.

The process according to the invention allows the production of semi-finished multilayer solid wood panels from raw wood, in particular in size ranges ranging from 6 mm to 48 mm in thickness for approximately 1.2 m in width and approximately 2 m. , 3 m in length.

PRESENTATION OF FIGURES

The invention will be better understood on reading the description which will follow, given solely by way of example, and referring to the appended drawing, given by way of non-limiting illustration, and which represents:
Fig. 1 : the figure 1 shows a block diagram of the steps of the method according to one embodiment of the invention.

It should be noted that the figure shows the invention in detail to allow its implementation.

DETAILED DESCRIPTION OF THE INVENTION

The method according to the invention allows the manufacture of multi-layered solid wood panels, comprising a plurality of solid wood veneers glued to each other, preferably parallel to the direction of the wood fibers.

According to one embodiment, each veneer has a thickness of approximately 3.2 mm, or in any event a thickness of between 1 mm and 10 mm, preferably between 1.5 mm and 4.5 mm, preferably still between 3.0 mm and 3.4 mm. This reduced thickness is important because it makes it possible in particular to obtain a finished product that differs from a material such as reconstituted solid wood. Indeed, in a reconstituted solid wood plate, the join between layers of wood is clearly visible, in particular by the edge, because each layer has a thickness of at least 2 cm.

Still preferably, the panel comprises between 2 and 20 veneers, preferably between 2 and 16 veneers, for a total thickness of between 6 mm and 48 mm.

With reference to the figure 1 , the successive steps of the method according to the invention are described.

Step 1 is a debarking step. From stored logs, we remove the bark. Continuity of this debarking step 1 is also provided for a first partial cutting 2 of the logs into logs, the size of which is a multiple of the desired final length of the logs with a view to unwinding (step 5). In other words, the logs obtained after this first cutting have a length equal to an integer multiple of the length of the final logs, which is preferably between 1.2 m and 1.35 m and can reach approximately 2 m.

Step 3 consists of steaming by immersion in hot water tanks. During this steaming step, during which the logs are subjected to a significant rise in humidity and temperature, a softening of the said logs is observed.

When exposed to humidity and high temperature, the wood undergoes a chemical transformation process during this stage 3. This makes it possible, for most types of wood, to reduce the necessary cutting forces, to limit tool wear and the appearance of cracks in the wood, while improving the surface condition of the veneers obtained after peeling ( step 5), by thinning the pockets of abrasive resins, if necessary, and by softening the knots of the wood.

At the end of stage 3 of drying, the logs have a homogeneous humidity, which will also make it possible to accelerate their continuous drying (stage 6).

For each type of wood, the optimum temperature and the duration of the steaming by immersion in hot water basins are chosen according to production needs. In practice, the temperature and the duration of the steaming provided for in step 3 vary between 50 ° C and 90 ° C and between 24 h and 48 h respectively, depending on the wood species and the diameter of the logs.

After baking step 3, comes a second step 4 of second cutting. Step 4 corresponds to cutting the logs from the first cutting in step 2, to form logs of a size suitable for feeding an unwinding line (see step 5). Preferably, according to the invention, at the end of this step 4, logs are produced having a length of approximately 1.2 m to 1.35 m and a diameter of at least 30 cm. In principle, it is possible to deviate from the minimum diameter of 30 cm; however, it is preferable that the diameter of the logs is sufficient for the unwinding step to be effective. In practice, logs with a diameter of at least 80 cm and up to 110 cm can be used.

The reduced length of the logs, 1.2 m to 1.35 m in particular, makes it easy to have sufficiently straight sections of logs, including from trunks that could have been considered unsuitable for industrial use in the processes. traditional production, where the logs have a length that must be greater than at least 2.6 m, or even much greater than 4 m.

It is specified that the existence of two distinct stages of first and second cutting 2, 4 is described here by way of illustration. Where appropriate, in an alternative embodiment of the invention, there may be only one sectioning, before steaming 3, to directly produce logs having the desired final size, typically between 1.2 m and 1. , 35 m. To improve the industrial rate, however, a first sectioning 2 is preferably envisaged, after debarking 1 and before steaming 3, to form ridges having a length equal to an integer multiple greater than or equal to 2 of the length of. final ridge desired. In the latter case, a second sectioning 4 is provided, after steaming 3, to produce the logs having the desired final length.

Step 5 of unwinding is of major interest in the process according to the invention.

During step 5 of peeling, each log of wood is fixed at its ends on a rotary axis using claws. As the axis turns, a knife uninterruptedly unwinds the wood to the core. The product obtained is an unwound veneer. In general, the first meters of unrolled veneer (phase also referred to as "rounding") constitute rebuses. In order to form the multi-layered solid wood, in accordance with the invention, whole and uniform sheets are in fact desired. The unwinding 5, in the method according to the invention, makes it possible to obtain layers formed in the same continuity of the tree, the rendering being faithful to the continuity of material of the tree as it has grown, unlike processes in which pieces of wood, small slabs, are glued together laterally to form larger slabs, the latter then being stacked. The unwinding thus makes it possible to produce long veneers of reduced thickness, between 1 mm and 10 mm, preferably equal to 3.2 mm, and of width equal to the width of the bales, i.e. between 1.2 m and 1, 35 m preferably.

It should be noted that the logs must be properly steamed in step 3, so that they can be unrolled satisfactorily. In particular, step 5 of unwinding must be carried out shortly after the end of step 3 by steaming by immersion in pools of hot water, in particular within 2 hours to 12 hours following said end of the step. 3 parboiling.

The quality of the wood of the logs sent to stage 5 of peeling is important; it is specified in particular that the main species of softwood can be unrolled, at namely fir, spruce, larch, douglas and various pines: Austrian black, sylvan, laricio, etc.

The qualities of compatible softwoods are referenced in particular in the European standard for classification of round softwood timber NF EN 1927. It is specified that other types of wood species can also be used, in particular hardwood tree species. .

According to the invention, the logs coming out of the steaming carried out in step 3 can be placed directly on the unwinder, that is to say on the machine performing step 5 of unwinding, in the case where only one cutting is planned. If a first sectioning 2 is provided, before steaming 3, and a second sectioning 4, after steaming 3 and before unwinding 5, then said second sectioning 4 is carried out very shortly after steaming 3 so as to respect the time period of 2h to 12h between steaming 3 and unwinding 5.

According to one embodiment, at the end of the unwinding of each log, the core (or residual core) is recovered to be used for another purpose, for example and depending on the species unrolled, table legs, handrails, interior railing supports. , decorative objects, grinding to make wafers, etc.

Another important step of the process according to the invention lies in step 6 of pre-cutting the fibers, which consists in cutting, in order to break them, without however creating a structural break in the unwinding, the wood fibers in so-called stretched portions. , where the peeled wood veneer tends to bend.

Step 7, trimming, consists in cutting the unrolled wood veneer, which forms a thin solid wood ribbon, to the required dimensions, step during which the unwanted singularities are also eliminated. It should be noted that the trimming step 7 can be carried out before or after the continuous drying step 8, described below.

Step 8 is the continuous drying of the peeled solid wood veneers. Continuous drying is carried out using a dryer of suitable dimensions. The unrolled solid wood veneers are introduced through an inlet of the dryer and, by means of a circulation of hot air inside, emerge dry from the dryer, having dried continuously inside the dryer.

On leaving the dryer, the dried unrolled solid wood veneers are sorted during a step 9, which is very important in the context of the process according to the invention.

The veneers of unrolled and dried solid wood are thus sorted according to their quality, mainly aesthetic, between a first category corresponding to veneers intended to form the external layers (in other words of the faces and counterfaces) of the solid multi-layered wood panels and a second category corresponding to veneers intended to form internal layers (in other words internal folds) of solid multi-layered wood panels.

For example, veneers of unrolled solid wood, dried and sorted, are stored temporarily by forming stacks comprising veneers belonging exclusively to one of said first and second categories.

According to one embodiment, the sorting of the solid wood veneers is carried out automatically by machines having optical sensors and configured in a suitable manner. The sorting can alternatively be carried out by human operators.

During step 10, the unrolled solid wood veneers, dried and sorted, are glued, then placed against each other, preferably parallel to the direction of the wood fibers, during a composition step 11, respecting the categories of veneers, and pressed (step 12).

To this end, the veneers are introduced into a machine called a gluing machine, which applies glue, for example a vinyl glue, in particular about 200 g of glue per m ² of veneer, on the faces of the solid wood veneers, then the faces Two glued veneers to be assembled are placed opposite each other and the veneers are applied against each other until the adhesive has hardened in order to ensure cohesive continuity between said veneers. The glue used, in particular a vinyl glue, is chosen as having the quality of becoming transparent on drying.

During step 11, a plurality of solid wood veneers are thus superimposed and glued to form a veneer assembly comprising a plurality of layers, as needed, in particular between 2 and 16 layers, each layer corresponding to a wood veneer. solid, with the Grade 1 veneers forming the outer layers of the assembly and the Grade II veneers forming the interior layers of the assembly.

The veneer assemblies thus formed are then pressed, the characteristics of the pressing (step 12) varying according to the type of glue used. The polymerization of the adhesive sometimes requires concomitant heating. The pressing time is also adapted according to the glue and the wood species used.

Finishes can then be implemented: edging (step 13) consists in giving the veneer assemblies a substantially parallelepipedal shape and sanding (step 14) makes it possible to improve the surface condition thereof.

Step 15 consists in cutting the assemblies thus finished, to form multi-layered solid wood panels to the desired dimensions.

Optionally, multi-layered solid wood panels can be painted, varnished, have moldings made, and, more generally, can undergo any custom cutting operation (sawing, drilling, routing, etc.).

The multi-layered solid wood panels can then be labeled and stored for sale.

Claims (8)

1. A method for producing multilayer solid wood panels comprising the following steps of:

   - barking (1) wood logs;

   - first slashing (2) the barked wood logs to form bolts;

   - steaming (3) said bolts;

   - rotary cutting (5) the bolts after steaming, to form solid wood veneers having a thickness of between 1mm and 10mm;

   - pre-cutting (6) wood fibres, in said solid wood veneers, into portions on which said wood fibres are stretched;

   - continuously drying (8) the solid wood veneers;

   - manually or automatically sorting (9) the solid wood veneers depending on at least one visual quality criterion, to form a first grade of veneers for making up outer layers of the multilayer solid wood panels and a second grade of veneers for making up inner layers of the multilayer solid wood panels;

   - performing assemblies of solid wood veneers by:

   i) glue-spreading (10) of the veneer faces to be assembled;

   ii) composing (11) veneer assemblies comprising a plurality of solid wood veneers disposed against one another, with respective glue-spread faces facing each other, so as to be bonded, each veneer assembly comprising a first grade of veneer for each external layer and, if necessary, one or more second grade veneers as internal layers;

   iii) pressing (12) the veneer assemblies to form multilayer solid wood panels.
2. The method according to claim 1, wherein, the wood fibres of each solid wood veneer having a direction, in other words an average orientation, the solid wood veneers are bonded to each other in twos so that the directions of the wood fibres of each of said veneers are parallel in the whole veneer assembly.
3. The method according to claim 1 or 2, additionally comprising a second slashing step (4), after the steaming step (3), to form bolts having a final length of between 120cm and 135cm, the first slashing resulting in forming bolts having a length equal to an integer multiple greater than or equal to 2 of said final length of said bolts.
4. The method according to one of claims 1 to 3, additionally comprising, at the end of the pressing step (12) for forming multilayer solid wood panels, a step (13) of trimming the multilayer solid wood panels to impart a substantially parallelepipedal shape to them.
5. The method according to claim 3, comprising, after the trimming step (13), a sanding step (14) to improve surface quality of said multilayer solid wood panels.
6. The method according to claim 4, comprising, after the sanding step (14), a cutting step (15) to form multilayer solid wood panels having desired final dimensions.
7. The method according to one of the preceding claims, additionally comprising, before the continuous drying step (8), a clipping step (7), to form veneers having desired dimensions.
8. The method according to one of the preceding claims, additionally comprising a step of painting the multilayer solid wood panels and/or a step of varnishing the multilayer solid wood panels and/or a step of performing custom cutting of the multilayer solid wood panels.

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