WO2013044939A1

WO2013044939A1 - Splined joint for assembling components made of fibrous materials

Info

Publication number: WO2013044939A1
Application number: PCT/EP2011/066750
Authority: WO
Inventors: Benoît HARGOT
Original assignee: 3B Structure Sprl
Priority date: 2011-09-27
Filing date: 2011-09-27
Publication date: 2013-04-04
Also published as: EP2760650A1

Abstract

The present invention relates to a structural building product comprising a succession of longitudinal components formed parallel to one another end to end and made of a fibrous material essentially made up of natural fibres. The components are joined together with an adhesive agent and using multiple male and female splines that alternate on the faces of the butt ends of the components. In each of two lateral and opposing parts of the butt end face of a component, each part covering at least one quarter of the total surface of the face of the butt end of a component, the layout of the male and female splines is such that the successive male splines have ends formed in a first imaginary plane. The first imaginary plane runs at an angle to a plane perpendicular to the longitudinal direction of the component.

Description

TEST-TYPE JOINT FOR ASSEMBLING WORKPIECES

FIBER

The present invention relates to a construction product, such as beam, column, bar or panel comprising several parts made from a material consisting essentially of natural fibers, such as softwood, hardwood, exotic wood, bamboo, rattan or other material. The present invention aims to improve the known technology of the abutment of said pieces by multiple tongues and notches, called "finger joint" or "finger joint" and commonly used in the wood industry for the manufacture of glue-laminated wood Solid wood, butted, "I" beam, floor, panel, etc.

The technique "finger joint" advantageously makes it possible to produce products of theoretically infinite lengths by the abutment of boards of variable and limited lengths. Thus, products having a length greater than the length of the boards constituting the product are possible. The ends of the boards are provided with notches (or teeth) and multiple tabs, which are alternately, successive tabs being separated by a notch. The boards are then abutted and connected by gearing tabs of a board in corresponding notches of the other board and fixed by means of an adhesive material. This technique is therefore particularly interesting for products based on natural fibers whose geometric dimensions are restricted anatomically.

The connection by multiple notches may be a weak point for the transmission of forces through said blade for woods with high mechanical strengths. In general, this fitting is accepted by certification bodies up to a bending strength limit of about 36 MPa (determined by a 4-point bend test). The technique of finger jointing is validated when the break occurs in the wood. For this reason, medium performance wood types (eg C18, C20, C24 as defined in EN 338 "Structural timber, Strength classes") are used, with a characteristic bending stress of 30 MPa or less. Beyond this limit, the rupture is generally present in the abutment (the joint) thus preventing the valuation of the mechanical advantages of the high-performance woods and consequently the obtaining of structural products based on butted wood more efficient.

[0005] Nevertheless, there are significantly more efficient wood species. In addition, it is known that the mechanical performance of certain materials consisting of natural fibers such as bamboo or rattan are generally much higher (typically more than twice) to those of softwood.

For this purpose, the document US 2002/076275 proposes to offset the ends of the tongues and the bottoms of the notches along the longitudinal axis of the board in the form of a zigzag. Such an arrangement makes it possible to prevent the concentrations of tension present in the funds successive cuts can be touched. Superior seal strength is obtained.

The document FR 2038317 proposes a seal (an abutment) with tabs, where the tabs arranged in a single plane of cross section extend in an oblique direction relative to the planes of the longitudinal faces of the boards. With such an oblique orientation, the seal will have almost identical strength on both sides (considering a square section), and therefore it is no longer necessary to consider the charging orientation of the board. Despite this advantage, the strength of the seal is not significantly increased.

The present invention aims to provide alternative forms of joints tabs and multiple notches to be used to connect parts formed end-to-end in structural products of construction, and have mechanical performance significantly better than the joints of the art prior.

According to the present invention, a structural product of construction is proposed as recited in the appended claims. The product comprises a succession of longitudinal pieces arranged parallel end to end and made from a fibrous material consisting essentially of natural fibers such as for example wood, bamboo, or rattan. The pieces are secured to one another by an adhesive agent and with the aid of tabs and multiple notches present alternately in the faces of the ends (ends) of the pieces.

According to one aspect of the present invention, in each of two side and opposite sides of the face of a piece of workpiece - that is to say regions located at two opposite ends of the face of the end , - each part covering at least 1/4 and preferably at least 1/3 of the total surface of the face of 1 end piece, the arrangement of the tabs and notches is such that successive tongues have ends formed in a foreground imaginary and such that the notches located between said successive tongues have funds formed in a second imaginary plane parallel to the foreground. According to the present invention, said planes are oblique with respect to a plane perpendicular to the longitudinal direction of the part.

Each side portion can have its own foreground and second imaginary plane. Preferably, the imaginary first planes of the two lateral portions are parallel. Alternatively, the imaginary first planes of the two lateral parts are oriented in reverse with respect to said perpendicular plane. Preferably, the first two planes form an angle with said perpendicular plane of the same absolute value.

According to an advantageous form of the present invention, the arrangement of all the tongues present on the face of one end piece is such that the ends of the tabs are formed in a single first imaginary plane. In this case, the first two imaginary planes coincide.

[0013] Preferably, the first (s) ima gi na ir plane (s) form (s) an angle with said perpendicular plane of absolute value between 10 ° and 80 °, preferably between 25 ° and 80 °.

Preferably, the part comprises at least one flat longitudinal face and wherein said tongue ends and said notches extend in a first direction, which is parallel to said longitudinal face of the workpiece. Preferably, the pieces are of rectangular section, thus having a width and a thickness. Preferably, the first (or) imaginary plane (s) is (are) parallel to a transverse direction along the width. Alternatively, the first (or) imaginary plane (s) is (are) parallel to a direction transverse to the thickness.

The parts may be more or less circular section, or even other non-rectangular shape.

Advantageously, the fibrous material is essentially made of bamboo fiber or rattan. The fibers are preferably oriented substantially parallel to the longitudinal direction of the workpiece, so as to have a length equal to the length of the workpiece. Thus, the fibers preferably extend continuously all along the piece, from one end of the piece to the other.

Preferably, the tabs comprise on their ribs tongues of smaller size.

Preferably, the tabs are trapezoidal or triangular and the distance between the bottoms of the notches and the ends of the tongues is between 5 mm and 150 mm, preferably between 5 mm and 100 mm.

Preferably, said succession of parts comprises parts made of fibrous materials of different mechanical performance.

Preferably, said succession of pieces constitutes a lamella in a stack of lamellae.

Preferably, the ends of a first group of said parts have hollow sections. Advantageously, the parts of the first group are secured with interlayers disposed between the parts of the first group. Preferably, the parts, and more particularly the parts of the first group, are bamboo canes.

The parts may be of variable section in the longitudinal direction of the workpiece.

According to a second aspect of the present invention, uses of the indicated product is proposed, as recited in the appended claims.

The products according to the invention are advantageously used in an application, wherein a seal comprising said tongues and said notches is sized to have a flexural strength greater than 24 MPa, preferably greater than 40 MPa.

The products according to the invention are advantageously used in a structure, to take structural loads in said structure, said succession of parts being designed to take compression forces, characterized in that in said succession at least one joint comprising said tongues and said notches are dimensioned according to the EUROCODES 5 standard using a characteristic axial compressive strength of the fibrous material.

The products according to the invention are advantageously used in a structure, to take structural loads in said structure, said succession of parts being designed to take tensile forces, characterized in that in said succession at least one seal comprising said tongues and said notches are dimensioned according to the EUROCODES 5 standard using the axial tensile strength characteristic of the fibrous material. Brief description of the figures

Figures 1 to 4 show four configurations of ends (abouts) board with tabs and multiple notches according to the present invention.

Figure 5 shows an exploded view of a subsequent seal configuration according to the present invention.

Figure 6 shows an exploded view of a seal according to the present invention, comprising a superposition of smaller tabs on larger tabs.

Figure 7 shows an exploded view of a seal according to the present invention between two tubes or hollow rods and the same diameter (circular section).

Figure 8 shows an exploded view of the assembly of two hollow rods of different outer diameters with the aid of a spacer.

Figure 9 shows the parts of Figure 8 in assembled configuration.

Figure 10 shows a view of a tab arrangement according to the present invention.

Detailed description of the invention

According to the invention, a clear increase in the resistance is obtained through the combination of an increase in the bonding surface in the joint between two parts and an oblique orientation of the plane of the tongues and notches relative to a plane perpendicular to the axial (longitudinal) direction of the parts. This oblique orientation aims to develop an area of significant axial length in which the transfer of forces through the joint takes place. In this way, the transfer of effort is distributed between fibers included in the material of the attachments over a longer length compared to the prior art.

Indeed, in the example of the document FR

2038317, the transfer of forces through the joint takes place in an axial length zone equal to the height of the tongues (axial distance between the bottoms of the notches and the ends of the tongues). In the example of US 2002/076275, this length is increased by the offset distance between the tabs, but still very low.

The joints according to the present invention are used to join parallel abutting parts, preferably in their longitudinal directions. The abutting pieces in such a way can be used as such as beam or column. Alternatively, they can be used as a stratum, called "lamella" in the art of wood. Thus, several slats can be stacked to obtain structures such as a beam, column, bar or panels of larger section relative to the section of abutting parts.

We will now describe, by way of example and non-limiting, a number of embodiments of joints according to the present invention with reference to the accompanying figures. In said figures, parts of rectangular section, such as planks, are considered to have a length much greater than the width and thickness and having a greater width than the thickness. In the figures, the orientation of the parts to be joined is indicated by the longitudinal axes (1), transverse to the width (w) and transverse to the thickness (h).

It should be noted that the present invention is not limited to this kind of parts, but it can be applied to section parts of any other form. A first embodiment of a seal according to the present invention is shown in Figure 1, wherein the ends 11 of the board 10 are cut by a plane parallel to the transverse direction along the thickness (h), and oblique to the transverse direction along the width (w).

A succession of tongues (or grooves) 111 is milled according to this plane 11. Each pair of successive tongues 111 is separated by a notch 112. For the realization of the tongues 111 and notches 112, the milling is carried out in the plane 11 in the direction defined by the intersection of this plane with a plane perpendicular to the transverse direction along the width (w) of the plate 10. That is to say that the median planes of the tongues 111 and notches 112 are perpendicular to the transverse direction along the width (w) of the board 10. Such a geometry can be obtained using a conical milling tool.

We will now define some terms relating to the tongues (or fingerings) according to the invention with the aid of Figure 10. Figure 10 shows an end view or about 1000 parts. The longitudinal direction of the part is indicated by the reference "1". The references "h" and "w" denote the transverse directions respectively following the thickness and the width of the part. As seen in FIG. 10, the ends 1000 of the pieces are provided with an alternating succession of tongues 1010 and notches 1020. The notches 1020 which open on the face of the end 1000 shrink as one enters the room in the longitudinal direction (1), while the tabs 1010 widen in correspondence. The tongues 1010 are delimited by their ends 1011. On one side and the other of the end 1011, the tongue 1010 is delimited by a coast 1012 (right side) and 1013 (left side), which are advantageously oblique. The ribs 1012 and 1013 extend between the end 1011 of the tongue 1010 and the bottom 1021 of the notch 1020. In this way, the section of the tongues 1010 will preferably be of triangular or trapezoidal shape.

An extension direction of the tongues 1010 and notches 1020 will be defined as being the direction of extension of the end 1011 of the tongue 1010, respectively the extension direction of the bottom 1021 of the notch 1020. 1010 and the notches 1020 therefore extend in a direction indicated by the reference "e" in Figure 10. This extension direction e may be parallel to the direction h, parallel to the direction w, or oblique to the h and w directions. It will therefore be noted that, in the case of FIG. 10, the two directions h and w are interchangeable.

We define a median plane Π of the tongues as being the plane parallel to the extension direction e of the tongues, which is positioned midway between the two right ribs 1012 and 1013 of the left tabs 1010. The orientation of Tongues according to the present invention will preferably be such that the median plane is parallel to the longitudinal direction 1 of the workpiece.

The height or length of the tongues 1010 will be defined as being the distance L (measured along the median plane Π) between the notch bottom 1021 and the tongue end 1011. The pitch P is defined as the distance between the median planes Π of two successive tongues.

Referring to Figure 1, the tongues 111 and the notches 112 therefore extend in 1 'end (the end) of the board and in the transverse direction following the thickness (h) of a longitudinal face 12 of the board 10 to the opposite face 13.

The tongues 111 and the notches 112 preferably have a cross section of trapezoidal or triangular shape. The ends 113 of the tongues 111 and the bottoms 114 of the notches 112 may be flat as is known from the prior art.

The cross section of the tongues 111 and notches 112 is preferably constant throughout their extension. Preferably, all the tongues 111 and all the notches have sections of the same size.

It will be noted that the tongues 111 and the notches 112 are offset along the longitudinal direction (1) by a constant distance. In this way, the ends 113 of the tongues 111 are formed in an imaginary plane 115 parallel to the transverse direction along the thickness (h), and oblique to the transverse direction along the width (w). Therefore, the imaginary plane 115 is oblique with respect to a plane 117 perpendicular to the longitudinal axis of the board (parallel to the longitudinal direction 1). This plane 117 is commonly called a plane of cross section. The angle between these two planes 115 and 117 is preferably between 10 ° and 80 °. The angle a is preferably at least 15 °, preferably at least 20 °, preferably at least 25 ° and preferably at least about 30 °. Preferably, the angle α is defined by seeking to achieve an optimum between the resistance of the seal and the strength of the material of the part to be assembled in order to limit the losses of raw material. For this reason the angle a is advantageously less than or equal to 75 °, advantageously less than or equal to 70 °, advantageously less than or equal to 65 °, advantageously less than or equal to about 60 °. In the same way, the bottoms 114 of the notches 112 are formed in an imaginary plane 116 parallel to the imaginary plane 115 of the ends 113 of the tongues 112.

Note that in the case where the extremities

113 of the tongues 112, and / or the funds 114 of the notches 112 have a certain width (do not terminate in point), consider the intersection of the ends 113 and funds 114 with the median planes of the corresponding tongues and notches for the construction of imaginary planes 115 and 116.

To assemble two boards according to the invention, is executed on a second board 10 an end (a bit) 11 of the same shape, but an opposite orientation angle. Of course, the tongues and notches are arranged in the two ends facing each other, such that when the planks are placed end to end, the tongues of one plank penetrate the notches of the other plank at the time of the assembly of the two boards.

The ends (abouts) of the boards are secured by bonding with an adhesive material that is available in the notches, which method is known from the prior art.

A second embodiment of a seal according to the present invention is shown in Figure 2, in which the ends 21 of the board 20 are cut by a plane parallel to the transverse direction along the width (w), and oblique with respect to the transverse direction according to the thickness (h).

The tongues 211 and the notches 212, are milled along this plane of the end 21. For the production of the tongues 211 and notches 212, which may be of the same shape as described for the first mode, the milling is carried out in said plane, in the direction defined by the intersection of this plane with a plane perpendicular to the transverse direction along the width (w) of the board 20. That is to say, the median planes of the tongues 211 and notches 212 are perpendicular to the transverse direction along the width (w) of the board 20. Such a geometry can be obtained by moving a milling tool in the direction of the intersection indicated here. -above.

The tongues 211 and the notches 212 therefore extend in a direction defined by the intersection of a plane parallel to the transverse direction along the width (w) and oblique with respect to the transverse direction according to the thickness ( h) at an angle β, with a plane perpendicular to the transverse direction along the width (w) of the board 20, and from one side face of the board 20 to the opposite face.

In this way, we obtain that the ends 213 of the tongues 211 are formed in an imaginary plane 215 parallel to the transverse direction along the width (w), and oblique with respect to the transverse direction according to the thickness (h) . Therefore, the imaginary plane 215 is oblique with respect to a plane 217 perpendicular to the longitudinal axis of the board (axis parallel to the longitudinal direction 1 - plane of cross section). The angle β between these two planes 215 and 217 has a value which is advantageously between the limits defined for the angle a above.

Similarly, the funds 214 of the notches

212 are formed in an imaginary plane (216) parallel to the imaginary plane 215 of the ends 213 of the tongues 212. A third embodiment of a seal according to the present invention is shown in Figure 3, in which the ends 31 of the board 30 are cut on a same plane as in Figure 1, so a plane parallel to the transverse direction according to the thickness (h), and oblique to the transverse direction along the width (w).

Unlike FIG. 1, the tabs

311 and the notches 312 are now milled in the plane of the end 31 in the direction defined by the intersection of this plane with a plane perpendicular to the transverse direction along the thickness (h) of the board 30. It is that is, the median planes of the tabs 311 and notches 312 are perpendicular to the transverse direction along the thickness (h) of the board 30. Such a geometry can be obtained by using existing milling tools, by movement of these tools according to the direction indicated above.

The tongues 311 and the notches 312, which may be of the same shape as described for the first embodiment, therefore extend in a direction defined by the intersection of a plane parallel to the transverse direction according to the invention. thickness (h) and oblique with respect to the transverse direction along the width (w) with a plane perpendicular to the transverse direction along the thickness (h) of the board 30, and a side face of the board 30 until 'on the opposite side.

In this way, the ends 313 of the tongues 311 are formed in an imaginary plane 315 parallel to the transverse direction along the thickness (h), and oblique to the transverse direction along the width (w). Therefore, the imaginary plane 315 is oblique with respect to a plane of cross-section 317. The imaginary plane 315 is preferably oriented at an angle α relative to in the plane 317, a value as described in relation to Figure 1 above. The bottoms 314 of the notches 312 are formed in an imaginary plane 316 parallel to the imaginary plane 315.

A fourth embodiment of a seal according to the present invention is shown in Figure 4, in which the ends 41 of the board 40 are cut by a plane parallel to the transverse direction along the width (w), and oblique with respect to the transverse direction according to the thickness (h), similarly to the case shown in FIG.

Unlike the case of Figure 2, the tongues 411 and the notches 412 are milled in the plane of the end 41 in the direction defined by the intersection of this plane with a plane perpendicular to the transverse direction following the thickness (h) of the board 40. That is to say, the median planes of the tongues 411 and notches 412 are perpendicular to the transverse direction according to the thickness (h) of the board 40. Such a geometry can be obtained by using tapered milling tools, as in the case of Figure 1.

The tongues 411 and the notches 412, which may be of the same shape as described for the first embodiment, extend in a direction defined by the intersection of a plane parallel to the transverse direction along the width. (w) and oblique with respect to the transverse direction according to the thickness (h) with a plane perpendicular to the transverse direction according to the thickness (h) of the board 40, and a lateral face of the board 40 up to on the opposite side.

Thus, the ends of the tongues 411 are formed in an imaginary plane 415 parallel to the transverse direction along the width (w) and oblique relative to the transverse direction according to the thickness (h). Therefore, the imaginary plane 415 is oblique with respect to a plane of cross section 417. The imaginary plane 415 is preferably oriented at an angle β with respect to the plane 417, of a value as described for the angle α in relation in Figure 1 above. The bottoms 414 of the notches 312 are arranged in an imaginary plane 416 parallel to the imaginary plane 415.

It will be noted that the fourth embodiment (FIG. 4) can be obtained from the first embodiment (FIG. 1), by inverting the directions of width (w) and thickness (h). Similarly, the third embodiment (FIG. 3) can be obtained from the second mode (FIG. 2), by inverting the directions of width (w) and thickness (h).

It is of course possible to combine the previous embodiments, so as to spare the ends of the tongues and notch bottoms in oblique imaginary planes relative to a cross section, in the transverse direction according to the thickness and in the transverse direction along the width. By way of example, it is possible to combine the first and second embodiments in order to obtain that the tongues are arranged in an imaginary plane obliquely with respect to the transverse direction according to the thickness (angle β) and obliquely relative to the transverse direction along the width (angle a). Such arrangements are obtained by cutting the ends of the board by a plane neither parallel nor perpendicular to the transverse directions following the width (w) and the thickness (h). It will be advantageous in this case to mill the notches in this plane along the direction defined by the intersection of this plane with a plane perpendicular to the transverse direction according to the thickness of the board (h) or with a plane perpendicular to the transverse direction along the width (w) of the board, so that the median planes of the tongues remain parallel to one of the side faces of the pieces.

The abutting shapes according to the invention develop bonding surfaces up to more than twice as much (depending on a and β) with respect to tabs arranged in a straight section. They therefore allow a greater transfer of the forces directly through the connection of 1 abutment, before rupture.

In addition, it is obtained with a provision of the tongues and notches in an oblique plane that the transfer of forces is not concentrated in a single cross section (plane perpendicular to the longitudinal axis of the board). The arrangement according to an oblique plane also allows a regular transfer of constraints. Such an embodiment can increase sharply the breaking strength of the joint.

In order to prove the effectiveness of the seal according to the present invention, tests were carried out with a class C30 wood cut boards of section w = 150 mm xh = 40 mm. A seal of the type according to Figure 3, with angle α = 60 ° has been assembled. The tongues were milled with a ZL 10/10 (Leitz) milling cutter, with a pitch of 3.8 mm, resulting in 10 mm pitch tongues (notch bottom distance - tongue end). A number of 40 mm / 3.8 mm = 10.5 tongues were thus obtained. For joint assembly, a single-component polyurethane glue and a pressure of about 25 bar were used. The bar thus obtained is cut to a length of 1 m, the seal being in the middle. Six identical bars were assembled in this way. Each bar has been individually tested on a device 4-point bending test: distance between the two supports 900 mm, two symmetrical loads at

1 'interdistance of 200 mm, 350 mm distance from the support points and symmetrically with respect to the joint. A force is applied at both points at a constant speed of 0.003xh mm / s until breaking. Table 1 shows the results.

Three bars were tested with the direction along the width (w) oriented vertically (case 1-3 in Table 1). In these first three cases, the rupture occurred in the wood (and not in the joint) because of the achievement of the limit of resistance of the wood in shear. The value f _m thus takes up the state of maximum stress in bending in the wood at the time of breaking of the bar due to shear.

Three bars were tested with the direction following the thickness (h) oriented vertically (case 4-6 in Table 1). In these last three cases, the break was made in the wood (and not in the joint), because of the achievement of the limit of resistance of the wood in bending. The value f _m thus takes up the limit of stress in bending of the wood. The strength of the joint was therefore greater than the strength of the wood.

Other tests under the same conditions were carried out on planks made of laminated bamboo-collar (direction of the fibers parallel to the longitudinal axis). A seal according to the type shown in Figure 3 has been shaped to assemble these boards with angles a = 45 ° and 60 ° and for different board thicknesses. The results obtained are shown in the table

2. Table 1: Results of C30 wood flexural tests (f _m : maximum value of bending stress at the moment of rupture)

sample; Nbr. sample: number of samples tested; f _m , mo _y : average flexural strength).

These results show a seal strength significantly higher than the values of 36 MPa, as known from the prior art (notches in a single plane of cross section). In this way a building element can be obtained by assembling several end-to-end parts according to the present invention. The construction element thus produced can be considered as having a mechanical strength at least equal to the mechanical resistance of the material of the constituent parts, like reconstituted wood beams for which the technique "finger joint" according to the prior art is fully effective.

The construction element mentioned above can be used as a unit (stratum or lamella) in the manufacture of structures of larger sections (by stacking slats), such as beams, columns, bars, panels. In addition, products having different cross-sectional cutting shapes can be made, for example beams with a cross section of Form I or T.

Thus, the present invention is advantageously used with high performance raw material. The material constituting the assembled parts is preferably a high performance wood, for example a high-performance wood of resinous, hardwood, exotic or any other type of wood.

By high performance is meant a material having mechanical performance greater than or equal to type C35 woods as defined in EN 338 "Structural wood, strength classes". The materials to which the present invention refers are fibrous materials, essentially consisting of natural fibers.

The present invention is also advantageously used with a material other than wood, such as bamboo or rattan. In the case of bamboo, preferably pieces made of bamboo fibers arranged parallel to the longitudinal direction of the piece are used. Preferably, therefore, the axial orientation of the fibers substantially coincides with the longitudinal axis of the part used in products of the invention. The fibers preferably (all) have a length equal to length of the room. This allows to better exploit the mechanical performance of bamboo.

[0081] Said bamboo pieces preferably have a density of between 600 kg / m ³ and 1300 kg / m ³ , preferably between 1000 kg / m ³ and 1300 kg / m ³ , preferably between 1050 kg / m ^3. and 1300 kg / m ³ .

The material used in the products according to the present invention preferably has an axial tensile limit (according to EN 338) greater than or equal to 25 MPa, preferably greater than or equal to 30 MPa, preferably greater than or equal to 35 MPa. preferably greater than or equal to 40 MPa, preferably greater than or equal to 45 MPa, preferably greater than or equal to 50 MPa.

When the material is bamboo, the bamboo pieces preferably have a limit in axial tension (according to EN 338) greater than or equal to 55 MPa, preferably greater than or equal to 65 MPa, preferably greater than or equal to 75 MPa.

The present invention advantageously allows to assemble several pieces end to end with joints of high tensile strength and thus, to obtain a construction assembly product, such as a beam, column, slab, or sign. The construction products thus obtained are used more in structural applications.

The joints or connections obtained according to the present invention are connections between pieces arranged in parallel, end to end.

In the present invention, the term "part" refers to a material that has essentially uniform and continuous mechanical characteristics all along the part.

[0087] Preferably, the fastening of the tongues and notches in the joints is practiced with means having a greater resistance than the shear strength of the workpiece material. For this purpose, the bonding is preferably carried out with an adhesive agent, such as a urea-formaldehyde, for example melamine-urea-formaldehyde. Alternatively, the adhesive agent may be a polyurethane, for example a mono- or bi-component polyurethane. The adhesive agent may be of the resin type, for example an epoxy resin, for example a mono- or bi-component epoxy resin.

In the embodiments described below, in relation to FIGS. 1 to 4, the ends of the tongues and the bottoms of the notches are formed respectively in single planes extending over the entire face of the end of the workpiece. . It will be noted that in accordance with the strength of the materials and in the case of a part loaded with forces perpendicular to the longitudinal axis of the part, the bending stresses are of high value in the fibers furthest away from the neutral fiber. Therefore, the distribution effect of the transfer of forces along a longer area as obtained according to a seal of the present invention is in these cases only important in the outermost parts of the joint section (the zones). extremes of section versus neutral fibers).

The embodiment shown in FIG.

5 gets this effect. On one side 501 and on the other side 502 with respect to the longitudinal central axis 500 of boards 50 and 51 to be assembled, tabs 511 and notches 512 are arranged according to the first embodiment (see FIG. , all extending in the same direction following the thickness h. The tabs and notches on one side 501 are sequentially offset in the longitudinal direction in one direction, while on the other side 502, the offset is in the opposite direction. We obtain as well as the ends of the tongues and the bottoms of the cuts are formed on one side 501 in parallel imaginary planes 515 which have a first orientation, while the ends of the tongues and the bottoms of the notches on the other side 502 are formed in parallel imaginary planes 516 of opposite orientation with respect to the planes of the side 501. The board end thus obtains a V shape. Such a shape also allows a large increase in the bonding surface compared to the case of FIG. 1. , but reduces the loss of material during the cutting of the ends of the boards, for example compared to the case according to Figure 1.

Other forms of board end are of course possible. The important aspect is to provide in a lateral part of one end piece of the tongues and notches whose ends are formed in oblique planes relative to the plane of cross section.

Each of these side portions preferably extends over at least a quarter of the total surface of the face of the end, preferably at least 35%, preferably at least 40% of said total area.

The area of the surface can be calculated on the basis of the projection of the end face (1 'end) of a workpiece on a plane perpendicular to the longitudinal direction.

There is no limitation on the orientation of the tabs. For example, in an alternative form to FIG. 5, the ends of the tongues could be oriented in the same plane and perpendicular to the orientation of the tongues 511 of FIG. 5.

Of course, a seal of the type according to Figure 5 develops a transfer of less favorable efforts in the central part, which makes this option less applicable for very high performance materials. But for less powerful materials, this joint offers a more economical solution and at the same time of sufficient resistance.

In order to subsequently increase the bonding surface, the present invention aims to graft smaller tabs to larger tabs. An exemplary embodiment is shown in Figure 6, which shows a seal between two boards 60 and 60 'formed of tongues 611 and notches 612 formed according to the example described in Figure 2. On the ribs 618 of the tabs 611 are superimposed tabs 621 smaller in size, extending in the same direction as the tabs 611. Note that tabs 621 are present in the two ends 61 and 62 of boards that are opposed. They are arranged so that a gear of the "large" 611 and "small" tongues 621 of the two boards takes place at the time of assembly.

Said superimposition of smaller tabs on the ribs of the "large" tabs can be applied to any type of multiple tab and slot joint, and in particular to the types referred to in the present invention.

The present invention is not limited to tabs of predetermined dimensions. Generally, the dimensions of the tabs depend on the dimensions of the parts that are assembled and the dimensioned load. These tongues may have a height (axial dimension between notch bottom and tongue end) of between 5 mm and 150 mm, preferably between 5 mm and 100 mm, preferably between 5 mm and 70 mm. The tongues may have a pitch (distance between the median planes of two successive tongues measured in a direction perpendicular to the longitudinal axis) of at least 1.5 mm, preferably at least 2 mm, preferably at least 2.5 mm and less than or equal to 50 mm, preferably less than or equal to 25 mm, preferably less than or equal to 15 mm.

The application of the seals according to the present invention is not limited to rectangular section pieces. Pieces of any other section, such as circular, polygonal, etc. can be connected according to the present invention. A joint between two hollow tubes of about equal diameter is shown in FIG. 7. The connection between the tubes 70 and 71 is performed with a parallel tab joint 711 and multiple parallel cuts 712, which extend in an oblique direction by report to a straight section. The tubes 70, 71 may for example be bamboo canes.

In case we want to assemble parts

(possibly hollow) of different dimensions, such as for example bamboo rods of too different diameter, the present invention proposes to use a spacer. This aspect is represented by way of example in FIG. 8. Tabs 811 and notches 812 are made at the ends of the two rods 80 and 81 according to one of the types previously described. The intermediate piece 82, provided with corresponding tongues and notches, is used to assemble the two rods 80 and 81. FIG. 9 represents the result obtained. The insert 82 advantageously has dimensions (of the cross section) equal to or larger than the dimensions of the widest piece 80, 81.

The length of the insert 82 (in the longitudinal direction or the longitudinal axis of the parts 80, 81 to be assembled) is preferably at least three times and preferably at least four times the length, in projection. on said longitudinal axis, (ends of) tongues made at one end of the insert. Such a length allows a more uniform transfer of efforts. It is preferable to manufacture the intermediate part of a material having at least the same mechanical performance (for example in terms of breaking strength) as the parts 80, 81 to be assembled. Said material is advantageously a fibrous material consisting essentially of natural fibers.

In use for parts subjected to bending stresses, it will be advantageous to arrange the product in such a way that the tongues extend (always in an oblique plane according to the present invention) in a direction, which is such that that a plane defined by said direction and the longitudinal direction (the longitudinal axis) of the pieces is perpendicular to the plane of the neutral fibers.

Claims

1. Structural product of construction, comprising a succession of longitudinal pieces (10, 20, 30, 40, 50, 60, 70, 80) arranged end to end and made from a fibrous material consisting essentially of natural fibers, said pieces being secured to one another by an adhesive agent and by means of tongues (111, 211, 311, 411, 511) and multiple cuts (112, 212, 312, 412, 512) present alternately in the faces (11, 21, 31, 41) of the ends of the pieces,

characterized in that

in each of two side and opposite parts (501, 502) of the face of a piece-end, each part covering at least a quarter of the total surface of the face of the piece-piece, the arrangement of the tabs (111 , 211, 311, 411, 511, 611, 711) and notches (112, 212, 312, 412, 512, 612, 712) is such that the ends (113, 213, 313, 413) of the successive tongues are arranged in a first imaginary plane (115, 215, 315, 415, 515, 516) and such that the bottoms (114, 214, 314, 414, 514) of the notches, located between said successive tongues, are formed in a second imaginary plane (116, 216,

316, 416) parallel to the foreground, said planes being oblique with respect to a perpendicular plane (117, 217,

317, 417) to the longitudinal direction (1) of the workpiece.

2. Product according to claim 1, wherein the first imaginary planes of the two lateral parts are parallel.

3. Product according to claim 2, wherein the arrangement of all the tongues present on the face of the piece end is such that the ends (113, 213, 313, 413) of the tongues are arranged in a single first imaginary plane (115, 215, 315, 415).

4. The product according to claim 1, wherein the imaginary first planes (515, 516) of the two lateral portions (501, 502) are oriented inversely with respect to said perpendicular plane, forming an angle with said perpendicular plane likewise absolute value.

5. Product according to any one of the preceding claims, wherein the first (or) imaginary plane (s) form (s) an angle with said perpendicular plane of absolute value between 10 ° and 80 °.

The product of claim 5, wherein said angle has an absolute value between 25 ° and 80 °.

7. Product according to any one of the preceding claims, wherein the part comprises at least one flat longitudinal face and wherein said tongues ends and said notches extend in a first direction, which is parallel to said face. longitudinal of the room.

8. Product according to any one of the preceding claims, wherein the parts (10, 20, 30, 40) are of rectangular section having a width (w) and a thickness (h).

9. The product of claim 8, wherein the first (or) imaginary plane (s) (215, 415) is (are) parallel to a transverse direction along the width (w).

10. The product of claim 8, wherein the first (or) imaginary plane (s) (115, 315) is (are) parallel to a direction transverse to the thickness (h).

11. Product according to any one of claims 1 to 6, wherein the parts (70, 80, 81) are of circular section.

A product according to any one of the preceding claims, wherein the fibrous material is essentially bamboo or rattan fibers, said fibers being oriented substantially parallel to the longitudinal direction of the workpiece and continuously extending from one to the other. about from room to room.

13. A product according to any one of the preceding claims, wherein said tongues (611) comprise on their ribs (618) tongues (621) of smaller size.

14. Product according to any one of the preceding claims, wherein the tabs are trapezoidal or triangular and the distance (L) between the bottoms of the notches and the ends of the tongues is between 5 mm and 150 mm, preferably between 5 mm and 100 mm.

15. Product according to any one of the preceding claims, wherein said succession of parts comprises parts made of fibrous materials of different mechanical performance.

16. Product according to any one of the preceding claims, wherein said succession of pieces constitutes a lamella in a stack of lamellae.

17. Product according to any one of the preceding claims, wherein the ends of a first group of parts (80, 81) have hollow sections, the parts of the first group being secured by means of insert parts (82). arranged between the pieces of the first group.

18. Product according to claim 17, wherein the parts (80, 81) of the first group are bamboo canes.

19. Product according to any one of the preceding claims, wherein the pieces are of variable section in the longitudinal direction of the workpiece.

20. Use of the product according to any one of the preceding claims for an application, wherein a seal comprising said tongues and said notches is sized to have a flexural strength greater than 24 MPa, preferably greater than 40 MPa.

21. Use of the product according to any one of claims 1 to 19 in a structure, to take structural loads in said structure, said succession of parts being designed to take compression forces, characterized in that in said succession at least a seal comprising said tongues and said notches is dimensioned according to EUROCODES 5 using a characteristic axial compressive strength of the fibrous material.

22. Use of the product according to any one of claims 1 to 19 in a structure, to take structural loads in said structure, said succession of parts being designed to take tensile forces, characterized in that in said succession at least a seal comprising said tongues and said notches is dimensioned according to the EUROCODES 5 standard using the axial tensile strength characteristic of the fibrous material.