EP4296026A1 - Method for manufacturing a plywood item,piece of furniture and mould - Google Patents

Abstract

The invention relates to a method of manufacturing a curved shaped object (3) formed primarily from plywood, the method comprising: cutting strips (2) from a plywood panel; and the arrangement and bending of the strips (2) in two different directions. The strips (2) may have edges which have a wavy profile. The strips (2) can be arranged in a superposition of several layers where they are arranged staggered or crossed. The object (3) is at least partially ovoid in shape.

Description

Technical area

The invention relates to the field of manufacturing plywood objects and in particular curved objects.

Prior art

The manufacture of curved objects in solid wood is not recent since the manufacture of barrels or ship hulls has been known and mastered for several centuries. Solid wood has the advantage of being mechanically stable and can be sanded and maintained. It is therefore robust and durable. Solid wood, on the other hand, has the disadvantage of being expensive. Also, its bending must be done hot, which does not simplify its implementation.

Plywood is often used instead of solid wood for many applications and its main advantage is its cost. Bendable plywood is a plywood comprising an odd number (generally 3) of layers of crossed superimposed veneers, and the intermediate layer of which is thinner than the outer layers. This structure gives the bendable plywood flexibility allowing it to produce curved shapes along an axis (mathematically, these are regulated surfaces with parallel generators). The preferred bending axis is generally parallel to the grain of the wood. In addition to the fact that bendable plywood is less robust than solid wood, bendable plywood has the disadvantage of only being bendable around a single axis. The variety of shapes that can be obtained by working a plywood panel is therefore limited.

Presentation of the invention

The invention proposes a process for manufacturing curved wooden objects which is less expensive than processes involving solid wood, while ensuring good robustness of the object thus obtained.

The invention relates to a method of manufacturing a curved shaped object formed primarily from bendable plywood, the method comprising: cutting strips from a panel of bendable plywood, the strips having an edge with a wavy profile; the arrangement of a layer of strips in contact two by two, the corrugated profile of one strip engaging in the corrugated profile of a neighboring strip; pressurizing the layer of strips to bend the strips in two different directions.

By “strip” is meant a generally elongated shape having a width much less than its length, for example at least 5 times less or at least 10 times less. The strip cut allows bending in two directions. The strip is designed so that its length is parallel to the preferred axis of bending (therefore according to the grain or grain of the wood) and its width is perpendicular to the preferred axis of bending. Bending the width around the longitudinal axis of the strip is easy because it corresponds to the natural bending of the bendable plywood. Bending around another axis (for example perpendicular to the length of the strip) is made possible by the flexibility of the strip inherent in its length/width ratio.

Thus, the strip can be bent around a first axis which can be an axis parallel to the length of the strip, and (simultaneously, before or after) around a second axis which can be an axis parallel to the width of the band.

Thus, the two bending directions can be intersecting, or even perpendicular.

Once pressurized, the strip layer may be self-supporting by construction or may be held together by gluing.

The use of bendable plywood therefore has the dual benefit of facilitating flexibility while ensuring good robustness. A single layer of veneer could not ensure this rigidity because the wood would tend to tear along the grain.

By “edge with a wavy profile”, we mean that undulations are visible on the edge of the strip, seen from a direction perpendicular to the face of the strip.

The “contacting” of the bands is done “song on song”, that is to say that a song of one band is in contact with the song of the neighboring band.

According to an advantageous embodiment of the invention, several layers of strips are superimposed, the strips of one layer being arranged perpendicularly or obliquely to the strips of another layer. According to an advantageous embodiment of the invention, several layers of strips are superimposed, the strips of one layer being arranged staggered from one layer to the other. These overlays further reinforce the robustness of the construction.

According to an advantageous embodiment of the invention, the layers comprise an internal layer, an external layer and an intermediate layer, the intermediate layer having at least one gap between two adjacent strips. This gap can allow the passage of connectors (cables, pipes).

The strips can therefore be superimposed in three layers. If three is a number guaranteeing a good balance between weight/rigidity/cost, it is understood that additional layers can be provided to further reinforce the robustness of the object.

According to an advantageous embodiment of the invention, a layer of fabric is arranged between two adjacent layers. This fabric can have thermal, sound, electromagnetic insulation properties and/or can consolidate the adhesion between the layers.

According to an advantageous embodiment of the invention, the wavy profiles of the edges of the strips describe dovetails. Compared to strips with straight edges, dovetails (or equivalent “puzzle” type shapes) make it possible to reinforce the robustness of the strips once assembled.

According to an advantageous embodiment of the invention, the strips and their arrangement are such that the object describes a generally ovoid shape potentially presenting recesses. The layers may extend 360°, or less, around a longitudinal axis of an egg shape. Recesses (windows) can be provided in the ovoid shape. These recesses result from the shape of the strips provided for this purpose.

According to an advantageous embodiment of the invention, at least one of the strips is flared at one of its ends, or at its two ends. The flared (or tapered) ends are brought together to form a “pole” of an ovoid or spherical shape.

According to an advantageous embodiment of the invention, the strips can be glued together (and/or between their layers), under vacuum or by pressing the layers together. An ecological glue is preferably used.

In combination or as an alternative to the above, the invention may also relate to a method of manufacturing a curved shaped object formed mainly from plywood, the method comprising: cutting strips from a plywood panel; the arrangement of the strips in several layers. The robustness of the structure can thus be obtained by the superposition of layers as an alternative to the corrugated profile of the edges.

The invention also relates to a piece of furniture, remarkable in that it comprises a curved element made of strips of bendable plywood and obtained using the manufacturing process mentioned above. This piece of furniture can be an alcove designed to accommodate a seated person wishing to isolate themselves from their environment.

According to an advantageous embodiment of the invention, the piece of furniture comprises two elements obtained using said method, the elements being of general ovoid shape and one of the elements being encapsulated in the other. The invention also has as its object a mold for the manufacture of a naval part, an aeronautical part or a boilermaking part, the mold being manufactured using the process mentioned above.

The invention provides a certain number of advantages. First, it allows the manufacture of objects with complex shapes at reduced cost without compromising their robustness. Then, the process can be easily applied for prototypes or small series, as well as for large series.

Brief description of the drawings

• There figure 1 is an isometric view of a plywood panel;
• There figure 2 represents a strip cut from the panel of the figure 1 and curved along two axes;
• There Figure 3 shows an example of an object obtained by assembling strips;
• There figure 4 illustrates a partial sectional view of the object;
• There Figure 5 represents an example of band song profiles;
• There Figure 6 shows some examples of strip layout;
• There Figure 7 illustrates another example of band shapes;
• There figure 8 shows an additional example of band shapes;
• There Figure 9 represents yet another example of band shapes;
• There Figure 10 describes a piece of furniture.

detailed description

The figures are represented schematically. Some dimensions may be exaggerated to make them easier to understand.

There figure 1 shows a bendable plywood panel 1. The direction of the grain of the wood is noted X and Y is referenced perpendicular to X.

Strips 2 are cut from panel 1. The strips are generally elongated in shape having a width perpendicular to the grain and a length in the direction of the grain. The length can be at least 5, at least 10, at least 20 or at least 30 times greater than the width.

Like the examples given below, each strip 2 has a particular shape, designed to form part of an object.

There figure 2 shows a strip 2 having been bent around the two axes X and Y. In this example, the two bending axes are perpendicular, but other bends are possible along two intersecting non-perpendicular axes. The form factor of the strip and its cutting in the direction of the grain are advantageous in this ability to be bent in both directions.

The right part of the figure 2 shows the AA section labeled on the left side.

There Figure 3 illustrates the example of an object 3 obtained by the assembly of strips 2. This object can be of generally axisymmetric shape, around an axis which is here illustrated as the longitudinal axis X of the strips. The object 3 may include recesses or windows 4.

There figure 4 shows a partial BB cut as identified on the Figure 3 . The wall of the object 3 can in fact be formed of several layers of strips 2, for example here the three layers 5, 6, 7. An intermediate layer 6 can be arranged between an internal layer 5 and an external layer 7. The strips 2 are arranged staggered from one layer to another.

On the intermediate layer 6, gaps 8 can be provided to carry out certain functions linked to the object 3. For example, electrical conductors can be "hidden" in these gaps so that they are not visible from the outside. Other functions, cables or pipes may occupy these gaps.

In certain places, fabrics 9 can be inserted between two layers. These fabrics can have well-defined functions, such as reinforcing sound, thermal or electro-magnetic insulation, a waterproofing function or reinforcing mechanical robustness. When the fabric 9 does not extend over the entirety of a layer 5, 6, 7, the strips 2 on which the fabric 9 is applied may be of lesser thickness.

Strips 2 can be butted together, edge to edge. The edges of the strips can be straight or substantially rectilinear.

A decorative veneer layer (not shown) can also be superimposed on the structural layers 5, 6, 7.

There Figure 5 shows an embodiment in which the edges 10 have more complex profiles than a simple straight or line with a curvature. The edges 10 may have a wavy profile. By “wavy” we mean the generality of a repetition of waves, niches, or as illustrated here dovetails or “puzzle” shapes. The profile of a band is complementary to that of the neighboring band.

It is understood that the profiles can be of the same type for all the strips or of different types, in particular depending on the shape of the object and the mechanical constraints which must be supported at the interface between two neighboring strips. The corrugated profiles have the double effect of facilitating the assembly of the strips to each other by holding them together during the manufacture of the object, and the effect of robustness once the assembly is completed.

There Figure 6 shows four examples (a, b, c, d) of strip assemblies with corrugated profiles. Depending on the grain direction of the panel chosen and the final shape to be obtained, the strips are cut in one direction or the other.

The strips can be placed on a support frame and with such an arrangement, simple longitudinal pressure (e.g. compression from the right and left of the Figure 6 ) allows you to shape the whole thing into conformity with the desired final form. This compression direction can correspond to the X direction on the Figure 3 .

The curved shape in two directions of space can then be self-maintained by wedging or be maintained by gluing.

When several layers are superimposed, they can cross the direction of the strips (for example a layer a is superimposed on a layer b or d). Alternatively, or in addition to achieve the same object, two layers a or two layers b can be superimposed, the strips being positioned staggered to avoid the superposition of two strip joints one on the other.

THE figures 7 and 8 represent other examples of strip shapes, intended to be assembled to produce object 3 with an ovoid shape of the Figure 3 with recesses 4. These figures show the strips 2 already cut (they are arranged differently on the plywood panel 1 where their lengths are according to the direction of the grain).

There Figure 9 shows an example where the strips are joined by a central part during their cutting. This type of cutting can facilitate the handling of the strips, without hindering their flexibility in the two bending directions (horizontal and vertical on the Figure 9 ).

There Figure 10 shows a possible application of the method according to the invention. A piece of furniture 11 is composed (see section CC to the right of the figure) of two ovoid elements 3 nested one inside the other. Room 11 may be of sufficient size to accommodate an adult. It can include a chair and possibly a desk. One of the two elements 3 pivots around the X axis.

As the two elements have recesses, by pivoting one of the two elements 3, the recesses can be placed opposite each other to allow the piece of furniture to be opened and allow access to it. Conversely, when the recesses are not facing each other, a person can be isolated inside the egg.

The piece of furniture 11 may correspond to the registered model EM 002585505.

The method for designing the shape of the strips is as follows: a given object is first modeled in CAD software; parameters are given to divide the virtual object into strips (for example criteria for maximum strip width, number of strips or width/length ratio); cut strips virtually are then flattened (developed on a plane) to obtain a pattern of each strip; the patterns can then be reproduced/printed on a plywood panel, or directly transmitted to a machining machine; the strips thus materialized on the panel can finally be cut.

In addition to the applications mentioned above, the manufacturing process of the invention can be used to manufacture molds for the manufacture of parts curved along several axes (in particular to obtain an ovoid shape as described above). Other applications are possible, for example for molds for ship hulls, blades, blades, or other aeronautical parts, fiberglass objects, sporting goods, boilermaking items, etc.

Claims (10)

Method of manufacturing an object (3) of curved shape formed mainly of bendable plywood, the method comprising: - cutting strips (2) from a bendable plywood panel (1), the strips having an edge (10) with a corrugated profile; - the arrangement of a layer of strips (2) in contact two by two, the corrugated profile of a strip (2) engaging in the corrugated profile of a neighboring strip (2); - putting the layer of strips (2) under pressure to bend the strips (2) in two different directions (X, Y). Method according to claim 1, characterized in that several layers (5, 6, 7) of strips (2) are superimposed, the strips (2) of a layer (5, 6, 7) being arranged perpendicularly or obliquely to to the strips of another layer. Method according to claim 1, characterized in that several layers (5, 6, 7) of strips (2) are superimposed, the strips (2) of a layer (5, 6, 7) being arranged in a staggered manner of one layer to another. Method according to claim 2 or 3, the layers comprising an internal layer (5), an external layer (7) and an intermediate layer (6), the intermediate layer (6) having at least one gap (8) between two strips ( 2) adjacent. Method according to one of Claims 2 to 4, characterized in that a layer of fabric (9) is arranged between two adjacent layers (5, 6, 7). Method according to one of the preceding claims, characterized in that the undulating profiles of the edges (10) of the strips describe dovetails. Method according to one of the preceding claims, characterized in that the strips and their arrangement is such that the object (3) describes a generally ovoid shape, potentially presenting recesses (4). Piece of furniture (11), characterized in that it comprises a curved element (3) made of strips of bendable plywood and obtained using the method according to one of the preceding claims. Piece of furniture (11) according to claim 8, characterized in that it comprises two elements (3) obtained using the method according to one of claims 1 to 7, the elements (3) being of general ovoid shape and one of the elements (3) being encapsulated in the other. Mold for manufacturing a naval part, an aeronautical part or a boilermaking part, the mold being manufactured using the process according to one of claims 1 to 7.

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