Wood forming process

Abstract

The present invention relates to a method for shaping a wooden object, comprising the following steps: - obtaining a blank by cutting a piece of wood in a direction transverse to the fibres of the wood; - positioning the blank using a mould; - pressing the blank by means of a shaping press brought to bear against a free surface of the blank, by exerting pressure in a direction parallel to the fibres of the wood, characterised in that the pressure during pressing is greater than 1.5*106 N / m2, in that the pressing is carried out under cold conditions, in that the pressing is carried out under dry conditions, and in that the mould comprises a positioning flank that bears against the blank during the pressing and forms a first angle that does not exceed 5° with the fibres of the wood of the blank positioned in the mould, and / or in that the shaping press comprises a punching flank that bears against the blank during the pressing, the second punching flank forming a second angle that does not exceed 5° with the fibres of the wood of the blank positioned in the mould. The present invention also relates to a wooden object obtained by this method.

Description

technical field

[0001] The present invention relates to a wood forming process, according to the preamble of claim 1. Such a process is known from US document 987 368 A. State of the art

[0002] In general, wood pressing is a well-known technique for creating wooden objects. This technique, which involves applying significant force against the surface of a wooden blank, often placed in a mold, compresses the wood to give it a predefined shape, while simultaneously increasing the object's strength due to its increased density. This technique also has the advantage of allowing the creation of hollow shapes that cannot be milled, such as polygonal shapes with sharp angles, which is impossible to achieve by milling due to the diameter of the milling cutter.

[0003] In the vast majority of cases, compression occurs in a direction perpendicular to the wood grain. Indeed, the pressure required to compress a piece of wood in a direction transverse to the grain is much less than that required to compress the same piece of wood in a direction parallel to the grain. In other words, forcing the grain together through compression requires less energy than crushing a grain upon itself.

[0004] It has also been suggested to compress the wood in a direction parallel to the grain. However, these methods are rarely used. Indeed, the pressures exerted during compression parallel to the wood grain can be extremely high and impossible to achieve with ordinary presses or large objects.

[0005] EP1706248 describes a wooden object, such as an electronic device casing, obtained by compressing a previously machined blank (for example, by milling). In this document, the bottom of the die (or mold) in which the blank is placed is strongly curved to prevent problems with demolding and to ensure the sharpness of the final object's contours. The part requires prior machining, for example, milling, of a cavity whose depth is simply increased by pressing. Only the bottom of the cavity is subjected to compression; the upper surface of the blank, on the other hand, is not deformed by the forming press. The aesthetic appearance of the object's external and internal edges is determined primarily by the milling. Brief summary of the invention

[0006] One object of the present invention is to propose a method for forming a wooden object free from the limitations of methods known in the prior art.

[0007] Another aim of the invention is to propose a method for forming a wooden object that is ecological and economical.

[0008] Another aim of the invention is to propose a method for forming a wooden object which makes it possible to quickly obtain particularly clean lateral and front faces and sharp edges.

[0009] Another aim of the invention is to propose a method for forming a wooden object that allows for the rapid production of sides resistant to shocks and moisture.

[0010] According to the invention, these goals are achieved in particular by means of a method for forming a wooden object comprising the following steps: Obtaining a blank by cutting a piece of wood in a direction transverse to the wood grain; positioning the blank using a die; pressing the blank using a forming press placed against a free face of the blank, applying pressure in a direction parallel to the wood grain characterized in that the pressure during pressing is greater than 1.5*10 6 N / m 2 , in that the pressing is done cold, in that the pressing is done dry, and in that the die has a positioning side in support against the blank during pressing and forming a first angle not exceeding 5° with the wood fibers of the blank positioned in the die, and / or in that the form press has a punching side in support against the blank during pressing, the punching side forming a second angle not exceeding 5° with the wood fibers of the blank positioned in the die.

[0011] The pressure during pressing is preferably greater than 2*10⁶ N / m², preferably greater than 5*10⁶ N / m². The force used to press the fibers in the direction parallel to the fibers is on the order of ten to twenty times greater compared to compression perpendicular to the fibers.

[0012] The punching flange slides along the fibers of the blank during pressing.

[0013] The punching flank can slide along the fibers of the blank during pressing, without participating in their longitudinal compression, or only in a very limited way if the punching flanks are not parallel to the fibers.

[0014] In one embodiment, the entire punching flank and the positioning flank slide along the fibers of the blank during pressing.

[0015] Compression parallel to the wood fibers confers advantages to the resulting object.

[0016] In particular, the faces, edges and contours of the final object are particularly sharp because they are defined by the wood fibers which are compressed upon themselves, but retain their straightness.

[0017] In the case of punching and positioning flanks parallel to the wood fibers during pressing, the lateral faces of the object along these flanks are defined by the lateral surface of contiguous compressed fibers, without the ends of the fibers appearing on these faces.

[0018] This results in high-quality side faces with very low roughness, including particularly smooth side faces as they come out of the press.

[0019] Even an angle of less than 5° between the punching and / or positioning sides on one side and the wood fibers on the other allows limiting the number of fibers whose end ends on lateral faces of the object, and therefore obtaining clean and smooth faces.

[0020] These lateral and / or frontal faces, defined by fibers compressed in the longitudinal direction, are particularly resistant to shocks and humidity.

[0021] The roughing does not require prior machining of a cavity or concave housing.

[0022] The concave portion(s) of the part can be obtained solely by pressing, without prior machining.

[0023] Thanks to the high pressures used, it is not necessary to moisten or heat the wood to deform it.

[0024] Pressure greater than 1.5*10 6< N / m 2< , preferably greater than 2*10 6< N / m 2< , preferably greater than 5*10 6< N / m 2< , makes it possible to obtain objects having sharp faces and edges, including objects having a polygonal profile or cavity.

[0025] Tests have shown that a pressure greater than 1.5 x 10⁶ N / m² allows for compression of at least 50% of the height (along the wood grain) of the blank for wood species with a density of 0.5 kg / dm³ or less. For example, for wood with an average density of 0.5 kg / dm³, the height of the blank can be compressed by up to 50% without affecting the final object. For woods with lower densities, even greater compression can be applied without damage; for example, for wood with a density of 0.4 kg / dm³, the maximum height of the blank can be compressed by 60% without compromising the object's integrity.

[0026] The forming press and die can incorporate guide flanges that slide against each other during pressing. These guide flanges advantageously hold the die precisely during pressing, ensuring controlled deformation and accurate forming. The blank is thus immobilized at the moment of pressing.

[0027] A die guide flank can guide the forming press during pressing, thus contributing to obtaining clean flanks of the compressed parts.

[0028] The pressing stage can be carried out using a form press comprising a first side perpendicular to the wood fibers, and a second flat side, the two flat sides being joined by the punching side.

[0029] The pressing stage may include a phase of guiding the form press, with the guide flank of the die guiding the form press.

[0030] The guide flanks are advantageously parallel to the pressing direction.

[0031] The guide sides are advantageously parallel to the longitudinal direction of the wood fibers.

[0032] The wood is thus compressed longitudinally, while pressing laterally against the positioning side of the matrix.

[0033] The maximum height of the blank in the direction of the wood grain can be reduced during pressing.

[0034] The height of the die guide flank can be greater than the maximum height of the blank before pressing.

[0035] The first surface, the second surface, and / or a background of the matrix can be structured.

[0036] The minimum resolution of the relief of the structuring can be very fine, i.e. between 10 µm and 50 µm, thus allowing the creation of very fine structures on the surface of the wood.

[0037] The punching side may include a first chamfer allowing in particular to smooth the transition between the inner side and the inner bottom of the object produced.

[0038] The first chamfer can form an angle with a bottom surface of the matrix of no more than 35°.

[0039] The positioning side of the matrix may include a second chamfer allowing in particular to smooth the transition between the outer side and the outer bottom of the object produced.

[0040] The second chamfer can form an angle with a bottom surface of the matrix of no more than 55°.

[0041] The forming press may include a transverse or longitudinal stepped profile, allowing in particular the approximation of curves that are difficult to produce.

[0042] The step size can be very small, typically between 0.01mm and 0.2mm.

[0043] The process may include a blank extraction step so as to detach the blank from the die and / or the forming press after the blank pressing step.

[0044] The blank may have a density before pressing of less than 0.75 kg / dm³, preferably less than 0.5 kg / dm³.

[0045] The wood from which the blank is cut can be chestnut, okoume, arolla pine, linden, alder, poplar, balsa, spruce, fir, maple, walnut, ash or beech.

[0046] A mechanical machining step of the blank can be introduced before the pressing step to increase its porosity and reduce its density.

[0047] Mechanical machining may involve several micro-drillings in the direction of the wood grain.

[0048] Micro-drilling can be done using a drill bit, or by stamping, for example using needles inserted simultaneously in a direction parallel to the wood fibers.

[0049] One end of the form press in contact with the blank may include a beveled profile.

[0050] According to the invention, these goals are also achieved by the wooden object obtained by the process described above. Brief description of the figures

[0051] Examples of implementation of the invention are given in the description illustrated by the accompanying figures, in which: There figure 1 illustrates possible cuts of a rough-out from a block of wood. The figure 2 illustrates a matrix containing a wood blank. The figure 3a illustrates a pressing stage in which a form press is brought against a blank in a die. figure 3bThis illustrates a pressing stage in which the form press has compressed part of the blank. figure 4 This illustrates a cross-section of a matrix containing a wood blank, with the matrix's positioning side inclined. figure 5 illustrates a cross-section of a die containing a wood blank and a forming press, with the die's positioning side and the press's guide side inclined. figure 6 This illustrates a cross-section of a form press with a punch featuring an inclined punching face. figure 7 illustrates a cross-section of a matrix with a special housing containing a wood blank. figure 8 This illustrates a cross-section of a forming press with a particular profile and two punches. figure 9 illustrates a cross-section of a matrix with a structured base. figure 10aThis illustrates a cross-section of a form press before pressing, allowing for various pressures to be applied to the surface of a blank. figure 10b This illustrates a cross-section of a form press after pressing, allowing for various pressures on the surface of a blank. figures 11a and 11b illustrate shaped presses with a chamfer. The figure 12 illustrates a matrix whose base has a chamfer. figure 13 This illustrates two positions of a die-cutting press extraction device after pressing. figure 14a This illustrates a forming press, one side of which includes a stepped section. figure 14b This illustrates a bottom view of a forming press whose profile includes stepped sections. figures 15a and 15b illustrate form presses comprising several punches. Example(s) of an embodiment of the invention

[0052] The present invention relates to a method of forming a wooden object by compressing a blank, the compression being carried out in a direction parallel to the wood fibers.

[0053] Examples of wooden objects that can be obtained by the process of the invention include, for example, toys, cutlery handles, decorative objects, tableware, boxes, watch boxes, jewelry boxes, containers or packaging for cosmetic products, clothing or fashion items such as buttons, shoe soles, etc.

[0054] This process is particularly well-suited for containers of viscous products such as ointments, creams, and even liquids. The densification resulting from pressing reduces the wood's porosity, thus providing sufficient impermeability to contain viscous or liquid products. Consequently, the risk of molecule transfer from the wood to a contacting material, or vice versa, is low because the transport channels are sealed. Furthermore, wood is naturally a high-quality material with antibacterial properties, a pleasant feel, and often a pleasant aroma.

[0055] There figure 1This illustrates examples of possible cutting of a blank 11 from a piece of wood 10. The cutting is carried out along cutting lines 12 in a direction transverse to the wood fibers in order to allow for compression parallel to the wood fibers in a second step. The term transverse here is to be understood in the sense of "non-parallel," i.e., the angle between the cutting lines 12 and the wood fibers is non-zero.

[0056] The blank 11 obtained by cutting is then positioned in or by a die 20. This die has a positioning flange 21 bearing against the blank. As illustrated in the figure 2The blank is positioned inside the die so that one of its transverse faces, facing the wood grain, is free, and so that the positioning side and the bottom of the die surround the blank over the remainder of its surface. Positioning the blank may consist of simply placing it through the open portion of the die designed to guide the forming press, or, in some more complex embodiments, the blank may be inserted laterally into a recess in the die. Such an embodiment is illustrated in the figure 7 where the geometric constraints of the blank require it to be placed in the die 20, for example by sliding it in a direction perpendicular to the pressing direction. It is also possible to position the blank by means of an opening machined in the blank, or of clampable parts of the die.

[0057] Once the blank 11 is positioned against the die 20, it is pressed by a forming press 30. The direction of the pressing is parallel to the wood grain of the blank. The forming press is placed against the free face of the blank, and pressure is applied to the forming press to deform the blank until all or part of the volume of the forming press and / or the die is reproduced in negative within the blank.

[0058] A key feature of this process is that the pressing is carried out cold and dry. Hot pressing reduces the pressure force required to deform the wood. However, increasing the wood's temperature contributes to its drying out, resulting in greater susceptibility to deformation, particularly shrinkage, which must then be compensated for, or cracking. Such compensation can be facilitated by steaming the wood before pressing or by using a shrink-shrink die in certain directions. However, these steps complicate the process and thus make it more expensive.

[0059] Dry pressing also means that the wood blank does not require any soaking before pressing, typically no soaking in a hardening resin or any steaming.

[0060] The form press has a punching flank 303 in support against the blank during pressing.

[0061] There figure 3a illustrates a first step of this process in which the blank 11 has been positioned in the die 20 against the positioning side 21 and a forming press 30 is moved towards the free surface of the blank. figure 3b illustrates a second stage in which a central part of the form press 30 compressed the blank 20 until a recess was obtained relative to the lateral part of the blank.

[0062] During the pressing step, the forming press 30 is mechanically brought against the free surface of the blank 11. To minimize lateral displacement of the forming press during its movement toward the blank, the die can be provided with a first guide flange 24 to guide the forming press. In a preferred embodiment, this first guide flange can consist of a portion of the positioning flange 21. In another, unshown, embodiment, the guide flange 24 of the die can be a modular element fixed to the die so as to increase the surface area used to guide the forming press. One function of this first guide flange 24 is to ensure precise guidance of the forming press relative to the die and the blank during pressing.

[0063] As illustrated on the figures 3a and 3bThe forming press may also include a second guide flange 32 which slides against the first guide flange 24 and / or against the positioning flange of the die during the movement of the forming press 30. In order to optimize the guidance of the press, the diameter of the forming press at the level of the second guide flange is slightly smaller than the internal diameter of the die at the level of the first guide flange of the die so as to leave a clearance of between 0.01mm and 0.5mm necessary for the extraction of the object after pressing.

[0064] To ensure optimal support of the blank 11 during pressing, the positioning flange 21 of the die is ideally parallel to the direction of the wood grain. However, to facilitate demolding of the wooden object after pressing, at least one positioning flange of the die can be slightly inclined at a first angle α to the wood grain, forming a truncated cone whose widest diameter is located at the free face of the blank. Such an embodiment is illustrated in the figure 4 . This first angle α can reach a maximum of 5° relative to the pressing direction, i.e. the direction of the wood fibers of the blank when it is positioned in the die.

[0065] In one embodiment, the die includes an inclined positioning flank as described above to facilitate demolding and an essentially vertical guide flank in line with the positioning flank to ensure guidance of the press during pressing.

[0066] The gap between the first positioning flange 21 and the blank is preferably very small before pressing, in order to allow the blank to be inserted into the die but to ensure its immobilization during pressing while preventing lateral deformation. In a preferred embodiment, this gap is preferably less than 0.5 mm.

[0067] The 30-form press illustrated on the figure 5includes a second guide flange 32 which, similarly to the positioning flange 21, is inclined at a third angle β relative to the compression direction so as to adapt to the inclination of the positioning flange. The third angle β can reach a maximum of 1° relative to the pressing direction. figure 5 illustrates an embodiment in which the guide flank of the form press 32 forms an angle β so as to correspond to the inclination of the positioning flank 21.

[0068] It is possible to have a die, or a forming press, with one or more positioning, or guiding, sides that are inclined, and at least one other positioning, or guiding, side parallel to the wood fibers, thus effectively guiding the forming press against the die throughout its movement.

[0069] The inclination of the second guide flange 32 of the forming press at an angle β relative to the wood fibers makes it easier, for example, to demold the blank after the pressing step. However, this inclination prevents the forming press from being guided within the die because as soon as the second guide flange of the forming press comes into contact with the first guide flange 24 of the die, the vertical movement of the forming press towards the blank is prohibited.

[0070] In another embodiment, the mold 20 is removable to facilitate the removal of the wooden object from the mold after pressing. Alternatively or additionally, the mold can be equipped with extractors to further facilitate the removal of the object from the mold.

[0071] Two distinct problems can arise during demolding. First, the form press 30 and the blank may remain attached to each other, and second, the die and the blank may also remain attached to each other.

[0072] To separate the mold from the blank after pressing, a demolding support can be placed above the die, as illustrated in the figure 13 The demolding support may include rods movable relative to the die and parallel to the pressing axis, allowing pressure to be applied to an upper lateral portion of the die so as to mechanically move the die containing the pressed blank away from the forming press.

[0073] In another embodiment, the movable rods are replaced by a retaining ring which allows pressure to be applied to the blank when the form press is removed so as to extract the form press from the blank.

[0074] The punching flank 303 on the form press 30 forms a second angle γ with the wood fibers. To allow for a wider variety of shapes to be pressed into the blank, and to facilitate the removal of the object and the press after pressing, this angle can vary between 0° and 5° according to the invention. Thus, the profile of the form press at its punching flank can be slightly conical, as illustrated in the figure. figure 6 . This second angle γ also allows for a superior quality of the internal surface of the wooden object.

[0075] Alternatively, extractors can be used to remove the object from the die after pressing. These extractors consist, for example, of modular elements of the die or the forming press. Typically, if the punching face of the forming press is vertical, i.e., if the angle γ is equal to 0°, it is preferable to add extractors.

[0076] In an embodiment according to the invention illustrated on the figure 6 The forming press 30 comprises a first flat surface 301 perpendicular to the wood grain when the blank 11 is positioned in the die 20, and a second flat surface 302 connected by the punching flange 303 of the forming press. The first flat surface and the punching flange together form a punch that determines the shape and / or compression volume of the blank. During the pressing step, the first flat surface 301 is the first part of the forming press to come into contact with the blank and then penetrates it under pressure.

[0077] In another embodiment illustrated on the figure 8The form press 30 includes several punches allowing several distinct impressions to be made in the blank 11. Each punch includes a first flat surface 301 perpendicular to the wood fibers when the blank is positioned in the die, a second flat surface 302 and a punching flank 303 connecting the first flat surface to the second flat surface.

[0078] The term punch is used here to designate the protruding portion(s) of the forming press at its end closest to the blank during pressing. figures 15a and 15b They illustrate form presses equipped with several punches, for example three punches, whose width can vary. The punches are thus delimited either laterally by the punching flank 303 of the form press, or by recesses 305 of the form press.

[0079] The minimum wood resolution for pressing with a multi-punch form press, that is, the minimum distance between the nearest ends of two consecutive punches, is between 0.1 mm and 10 mm, preferably between 0.5 mm and 8 mm, typically between 1 mm and 5 mm. This resolution depends on several parameters, such as the wood species and / or the pressing depth. figure 15a This illustrates a form press with a resolution of approximately 3 mm, meaning that the width of the 305 recesses is approximately 3 mm. figure 15b illustrates an embodiment in which the resolution is approximately 2mm and in which the recesses are particularly eccentric with respect to the center of the forming press.

[0080] The geometry of the lower portion of the punching flank 303 of the form press 30, i.e. the portion which first comes into contact with the blank during pressing, is particularly important with regard to the sharpness of the flanks and the bottom / flank transition of the wood piece resulting from pressing.

[0081] In one embodiment, the punching side forms a sharp angle with the portion of the forming press perpendicular to the wood fibers.

[0082] As illustrated on the figures 11a and 11b The punching flange 303 can also be provided with a chamfer 304 to obtain a corresponding chamfer on the blank after pressing. Such a chamfer is typically used to smooth the flange / bottom transition of the part obtained after pressing the blank.

[0083] For an internal shape, the transition between the vertical sides and the bottom surface of the matrix 23 typically has a sharp angle with a chamfer of at most 35°, preferably of at most 30°.

[0084] Alternatively or complementarily, the punching flank 303 can also be provided with a rounded edge, the angle of which with the bottom surface of the die does not exceed 35°, preferably 30°.

[0085] In an embodiment not shown, the guide flange 303 may also include a chamfer on an upper portion, so as to create a chamfer on an external shape of the blank during pressing. For such chamfers on external shapes, the chamfer angle can typically be up to 50°.

[0086] As illustrated on the figure 12, the positioning flank 21 of the matrix may also include a chamfer 211 at the transition positioning flank / bottom surface of the matrix.

[0087] Such a chamfer 211 makes it easier to remove the blank from the die after pressing. It also provides a clean transition between the outer flanks of the blank and the outer surface of the blank's bottom. The chamfer 211 typically forms an angle with a bottom surface of the die of no more than 55°, preferably 45°.

[0088] To improve the appearance of the part obtained from the pressed blank, the punching flange 303 of the form press 30 can include a stepped profile with a relatively small pitch compared to the size of the blank. Such a stepped profile makes it possible to approximate a curve, the creation of which by pressing can be complex, without altering the visual appearance. It also improves the sharpness of certain flange / bottom transitions of the blank.

[0089] In an embodiment illustrated on the figure 14a The profile of the transition between the punching side and the lower part of the form press includes a step whose pitch, i.e. the width of a step, is between 0.01mm and 0.2mm. The steps are thus perpendicular to the wood fibers of the blank when it is in the die.

[0090] In another embodiment, the guide side comprises a stepped profile whose steps are parallel to the wood grain of the blank. figure 14b This illustrates a stepped profile of the form press obtained by cutting the blank in the die along a plane orthogonal to the wood grain. As explained above, pressing curved sections, especially when their curvature is parallel to the wood grain during pressing, can be problematic in terms of the sharpness of the sides when the angle of the curve is significant. Approximating such a curve with a stepped section whose straight segments are sharp during pressing solves this problem.

[0091] The sharpness of the edges can depend on the pressing speed. Generally, a higher pressing speed results in sharper edges. This speed is typically between 4 mm / s and 180 mm / s.

[0092] During the pressing stage, the blank 11 can be compressed over its entire free surface or over one or more predefined areas corresponding to the geometry of the forming press. Thus, the maximum height H of the blank along the wood grain may be reduced after pressing if the entire blank is compressed. Conversely, the maximum height H of the blank along the wood grain may remain the same after pressing if only a specific area of ​​the blank is compressed.

[0093] On the figure 3a The blank has a maximum height H before pressing, while, as illustrated on the figure 3b The blank has a maximum height after pressing H' and a minimum height after pressing H". In all cases, the following relationships are always verified: H ≥ H ′ ≥ H " . If only part of the blank is pressed, then H = H' > H", while if the entire blank is pressed, then H > H' ≥ H".

[0094] The pressing stage can be carried out by applying continuous pressure from the forming press 30 to the free surface of the blank so as to compress the entire desired height in one go. Alternatively, the pressing stage can be carried out by hammering, that is, a series of pressures from the forming press against the free surface of the blank.

[0095] Hammering allows for a reduction in the pressure force required to press a similar height, and / or a densification of the wood over a greater depth.

[0096] Alternatively, or additionally, the blank, die, or forming press can be subjected to vibrations, for example, vibrations along the wood fibers at a frequency between 1 Hz and 1 MHz, to set it in motion and facilitate compression of the blank by the forming press. These vibrations facilitate the penetration of the forming press into the wood, promote the sliding of the fibers against each other, and can help soften the wood by slightly heating it during pressing. Thus, as with hammering, subjecting the blank to these vibrations allows for a reduction in the pressing force required to compress a similar height, and / or densification of the wood to a greater depth.

[0097] Structuring involves creating a relief by pressing on a portion of the blank; this relief is comparatively small relative to the size of the blank. Reliefs obtained through structuring typically have a minimum resolution on the order of the size of the water channels in the wood, i.e., between 10 µm and 50 µm.

[0098] The depth of the structuring relief in the pressing direction is less than the distance the forming press travels in the blank. The depth of the structures in the pressing direction can be less than 2 mm.

[0099] In one embodiment, the forming press is structured so as to imprint the pattern in negative onto the blank during pressing. Alternatively or complementaryly, the base surface of the die is also structured so as to imprint the pattern in negative onto the outer surface of the blank in contact with the base of the die.

[0100] Structuring allows, among other things, the creation of logos, brands, texts, patterns as well as particular textures that can have a physical or aesthetic function.

[0101] Alternatively or additionally, a structured element can be placed between the forming press and the blank, or between the blank and the base surface of the die, so that during pressing, the pattern of the structured element is reproduced in negative on the blank. The structured element can be, for example, a piece of fabric, a piece of leather, a piece of paper, a leaf, etc. In one embodiment, a first pressing step forms the blank, particularly the blank sides, and then a second pressing step structures portions of the formed blank.

[0102] The part of the forming press that contacts the blank during pressing can be structured to produce a negative or positive image on the blank. The first and / or second flat surface of the forming press can be structured.

[0103] Similarly, the figure 9 illustrates an embodiment in which the matrix, in this case a background surface of the matrix 23 opposite the free surface of the blank, can also be structured to obtain a pattern in positive or negative on the face of the blank opposite its free face.

[0104] This structuring of the form press and / or matrix makes it possible to combine the pressing of a blank in order to form a wooden object and the printing in negative or positive of a pattern.

[0105] The structures may include, for example, an image, a pattern, a logo, text, ribs, grooves, etc., on the surface of the forming press in order to be printed in negative in the draft.

[0106] Clearly, the type of wood chosen for the blank significantly influences the pressing parameters and the variety of objects that can be made. Indeed, the denser the wood, the greater the pressing force required to compress it by a given height. Therefore, the lower the density of the wood, the greater the compression that can be achieved, and thus the larger the compressed volume.

[0107] Thus, in one embodiment, the blank is cut from wood having a density of less than 0.75 kg / dm³, preferably from wood having a density of less than 0.5 kg / dm³. Suitable wood species include, for example, poplar or linden (approximately 0.5 kg / dm³), spruce (approximately 0.45 kg / dm³), and balsa (approximately 0.14 kg / dm³). Other species such as chestnut, maple, beech, fir, okoumé, Swiss pine, or alder are also particularly suitable for the purposes of the present invention. The list of these species is in no way exhaustive, the present pressing process works with wood species having a density of up to 0.75 kg / dm 3<, or even up to 0.85 kg / dm 3<.

[0108] To increase the porosity of the wood and thus facilitate the pressing stage, a preliminary machining step of the blank can be carried out. In one embodiment, a series of micro-drillings are performed using a drill bit, or by stamping with needles, so as to reduce the density of the blank before pressing. The holes thus created by micro-drilling are filled during compression. The resulting object can be made sufficiently airtight to contain viscous products (creams, pastes, etc.) or even liquids.

[0109] The process of the invention can also be used to manufacture objects that do not have concave portions on their upper surface, but only convex portions. In one embodiment, the process is used to manufacture wooden toy pieces, for example, interlocking building blocks.

[0110] In one embodiment, the end of the forming press that first comes into contact with the blank during pressing has a beveled and / or sharp profile to facilitate its penetration into the wood. Such a profile also results in clean sides of the wooden object after pressing and eliminates the need for subsequent sanding.

[0111] In an embodiment illustrated on the figures 10a and 10b Different pressures can be applied to different areas of the blank during a single pressing step using the form press. As illustrated in the figures 10a and 10bA pressure force F2 is applied to a first lateral zone of the blank, while another pressure force F1 is applied to the central part of the blank. In this way, different compression heights and densities can be achieved with a single pressing step, while ensuring optimal retention of the blank in the die during pressing.

[0112] The ability to obtain different pressure forces using a single forming press is achieved, for example, by placing a spring above the lateral area of ​​the forming press (i.e., above the area corresponding to pressure force F2). Thus, when the same pressure force is applied to the top of the forming press, the spring absorbs part of the pressure force on the lateral area of ​​the workpiece, while the pressure on the central area is at its maximum.

[0113] This method can also be applied to join a second wooden blank to the first blank by pressing. In an embodiment not shown, a second blank is placed between the first blank and the forming press. The two blanks are then joined together during the pressing step under the pressure exerted by the forming press. The joining of the two blanks can be facilitated by pre-pressing two corresponding profiles onto each face of the blanks intended to be in contact with the other.

[0114] While the grain direction of the first blank is always parallel to the pressing direction, the grain direction of the second blank can be parallel, perpendicular, or oblique to the pressing direction. This flexibility allows for the creation of interesting patterns on the final object, as well as facilitating pressing by reducing the pressure required to compress the two blanks, or resulting in a particularly strong final object. It is also possible to combine wood species with different densities and compressive strengths.

[0115] The joining of two pieces obtained by the pressing process can also be achieved after each piece has been pressed, for example using tenons and / or mortises. The piece intended to be inserted into the other can be dried before insertion; by absorbing moisture from the ambient air, it will tend to expand to strengthen the tenon-mortise joint.

[0116] Alternatively or complementarily, the pressing method of the present invention can also be applied to a blank made by gluing two or more pieces of wood together to allow for the pressing of larger blanks. The gluing can typically be carried out along the grain of the wood in both pieces. The pressing strength of a glued blank is essentially identical to that of an unglued blank. Furthermore, the glue lines are practically invisible after pressing. Reference numbers used in the figures

[0117] 10 Piece of wood 11 Roughing 12 Cutting line 20 Die 21 Positioning flange 211 Second chamfer 22 Housing 23 Die bottom surface 24 First guide flange 30 Forming press 31 Punch 32 Second guide flange 301 First flat surface 302 Second flat surface 303 Punching flange 304 First chamfer 305 Recess 40 Moving rod αFirst angle γSecond angle βThird angle HHMaximum height before pressing H'Maximum height after pressing H"Minimum height after pressing

Claims

1. Method for shaping a wooden object comprising the following steps: - obtaining a blank (11) by cutting a piece of wood (10) in a direction transverse to the wood fibres; - positioning the blank using a die (20); - pressing the blank by means of a moulding press (30) applied against a free face of the blank, exerting pressure in a direction parallel to the wood fibres, characterised in that the pressure during pressing is greater than 1.5*106N / m2 in that the pressing is carried out cold, in that the pressing is carried out dry, and in that the moulding press has a punching flank (303) resting against the blank during pressing, the punching flank forming a second angle (γ) not exceeding 5° with the wood fibres of the blank positioned in the die, the contact surface between the moulding press (30) and the blank comprising a first flat surface (301) perpendicular to the wood fibres and a second flat surface (302), the punching flank (303) of the moulding press joining the first flat surface and the second flat surface, so that during the pressing step, the first flat surface (301) is the first part of the moulding press to come into contact with the blank and then penetrates inside it under the effect of the pressure.

2. Method according to claim 1, wherein the die (20) has a first, guide flank (24) which is essentially vertical, and / or wherein the moulding press (30) has a second guide flank (32) which is essentially vertical, the second guide flank being able to slide against the first guide flank during pressing.

3. Method according to one of the preceding claims, wherein a maximum height (H) of the blank (11) in the direction of the wood fibres is reduced during pressing.

4. Method according to one of the preceding claims, wherein the pressure during the pressing step is preferably greater than 2*106N / m2, preferably greater than 5*106N / m2.

5. Method according to one of the preceding claims, wherein the punching flank (303) comprises a first chamfer (304).

6. Method according to the preceding claim, wherein the first chamfer (304) forms an angle with a bottom surface of the die of at most 35°.

7. Method according to one of the preceding claims, wherein the die (20) has a positioning flank (21) that bears against the blank during pressing and forms a first angle (α) not exceeding 5° with the wood fibres of the blank positioned in the die.

8. Method according to the previous claim, wherein the positioning flank (21) comprises a second chamfer (211).

9. Method according to the previous claim, wherein the second chamfer (211) forms an angle with a bottom surface of the die (23) of at most 55°.

10. Method according to one of the preceding claims, wherein the moulding press (30) comprises a stepped profile.

11. Method according to one of the preceding claims, wherein the moulding press (30) and / or a bottom surface of the die (23) are structured so as to form a relief on the blank by pressing.

12. Method according to one of the preceding claims, characterised in that the blank (11) has a density before pressing of less than 0.75 kg / dm3, preferably less than 0.5 kg / dm3.

13. Method according to one of the preceding claims, characterised by a step of mechanically machining the blank (11) before pressing to increase its porosity and reduce its density.

14. Method according to the preceding claim, the mechanical machining comprising several micro-drillings or needle stampings in the direction of the wood fibres.

15. Method according to one of the preceding claims, one end of said moulding press (30) in contact with the blank comprising a bevelled profile.

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