Construction element with pre-pressed boards

Abstract

A construction element includes superposed wooden structural boards that are provided with grooved patterns at the contact interface between the boards in order to prevent the first board and the second board from sliding relative to each other along at least one axis. The construction element further includes a retention system for retaining the boards against each other at the contact interface. The grooved patterns are pre-pressed against each other and the retention system includes at least one metal threaded rod component at least partially passing through at least two of the wooden structural boards at the contact interface.

Claims

1. A method for manufacturing a construction element comprising the following steps: superimposing a first structural board having a first set of grooved patterns on an upper face and a second structural board having a second set of grooved patterns on a lower face so that the first set of grooved patterns on the upper face of the first structural board and the second set of grooved patterns on the lower face of the second structural board are in contact with each other at a contact interface, wherein the second set of grooved patterns are at least substantially complementary with the first set of grooved patterns; before holding the first structural board and the second structural board together, putting the first structural board and the second structural board under pressure against each other with a pressure of at least 75 kPa such that the grooved patterns are at least partially warped; and holding the first structural board and the second structural board together by a holding system comprising at least one metal threaded-rod member at least partially passing through the first structural board and the second structural board at the contact interface so as to form an obstacle to the sliding of the first board and of the second board with respect to one another along at least one axis.

2. The manufacturing method according to claim 1, wherein the grooved patterns are arranged so as to form an obstacle to the sliding of the first board and the second board with respect to one another along at least two non-parallel axes.

3. The manufacturing method according to claim 2, wherein the grooved patterns comprise a first series of grooves parallel to each other, and a second series of grooves parallel to each other but not parallel to the grooves in the first series.

4. The manufacturing method according to claim 3, wherein at least some of the grooved patterns are in the form of a matrix of barbs, the shapes of which are substantially those of a pyramid with a quadrilateral base.

5. The manufacturing method according to claim 1, wherein the metal threaded-rod member comprises a threaded rod provided with a head and a spike disposed at opposite ends of the rod.

6. The manufacturing method according to claim 1, wherein the metal threaded-rod member has a roughly cylindrical shape.

7. The manufacturing method according to claim 1, wherein the metal threaded-rod member comprises at least two threads interleaved and with different diameters.

8. The manufacturing method according to claim 1, wherein the holding system comprises four metal threaded-rod members distributed over the whole of the contact interface and at least partially passing through the first structural board and the second structural board at the contact interface.

9. The manufacturing method according to claim 8, wherein the distance that separates at least one of the members from the edge of the contact interface is between 1.5 and 4 centimeters.

10. The manufacturing method according to claim 1, wherein the construction element comprises at least three wooden structural boards, at least some of the faces of which are in pairs superimposed at respective contact interfaces, wherein the holding system comprises a first set of metal threaded-rod members at least partially passing through a first part of the boards and a second set of metal threaded-rod members at least partially passing through a second part of the boards, the first and second board parts having at least one board in common, the members being offset with respect to each other in the planes of the contact interfaces of the boards.

11. The manufacturing method according to claim 10, wherein the length of at least one of the metal threaded-rod members is substantially equal to a total thickness of either the first part of the boards or the second part of the boards.

12. The manufacturing method according to claim 1, wherein at least one of the members is positioned in a hollow of the grooved patterns.

13. The manufacturing method according to claim 10, wherein a diameter of at least one of the members is configured so as to cover no more than four grooved patterns.

14. The manufacturing method according to claim 1, wherein the first structural board and the second structural board are put under pressure against each other with a pressure of at approximately 150 kPa.

15. The manufacturing method according to claim 1, further comprising: at least partially providing the upper face of the first structural board with the first set of grooved patterns; and at least partially providing the lower face of the second structural board with the second set of grooved patterns.

Description

(1) Other features and advantages of the invention will emerge from a reading of the following description of embodiments of the invention, given by way of example and with reference to the accompanying drawings.

(2) FIG. 1 is a perspective view of an example of a construction system according to the present invention.

(3) FIG. 2 is a perspective view of one of the elements constituting the construction system of FIG. 1, according to the present invention.

(4) FIGS. 3 and 4 are perspective views of two structural boards of a construction element, according to a first embodiment of the present invention.

(5) FIGS. 5 and 6 are perspective views of two structural boards of the construction element according to a second embodiment of the present invention.

(6) FIGS. 7 and 8 are views in cross section of three structural boards of a construction element, according to a third embodiment of the present invention.

(7) FIG. 9 is a plan view of a contact interface between two boards.

(8) FIGS. 10A and 10B are close views of the interface of FIG. 9.

(9) FIGS. 11A and 11B are respectively a side view and a plan view of a member of a holding system according to one embodiment of the invention.

(10) FIG. 12 is a detailed view in cross section of a construction element according to an embodiment of the present invention.

(11) With reference to FIG. 1, a construction system 1 according to the present invention may be in the form of a timber dwelling, although any other form of edifice can be envisaged. This dwelling comprises in particular a floor, walls and a roof rake. They may for example be formed from wood. Openings may be formed in a plurality of these elements, for example on one of the walls, in order to place a window thereon.

(12) In this example, a first wall comprises a set of construction elements including the construction element 10. A second wall itself comprises a set of construction elements including the element 20. This division into construction elements relates to the limits of sizing of standard transports, of the lifting means in construction and the industrial tools for manufacturing these elements.

(13) The construction element 10 is shown in more detail in FIG. 2. The first construction element 10 in FIG. 2 comprises a set of eight superimposed plies, the first four of which are the plies 100, 110, 120 and 130. The configuration of the plies is said to be “crossed boards”. A different number of plies may be provided, for example greater than three, preferably between five and fifteen, preferably between seven and twelve. The determination of the optimum number of plies is an arbitration between the thermal performance of the construction element 10, its strength (which is better, the more plies there are), its total thickness (which, usually, must not exceed a certain limit), its cost and its application (interior or exterior walls, floors or roofs, etc.).

(14) Each of the plies 100, 110, 120 and 130 comprises wooden structural boards. The first ply 100 comprises four boards 101, 103, 105 and 107 parallel and oriented along the axis (Ox), The second ply 110 comprises four boards 111, 113, 115 and 117 parallel and oriented along the axis (Oy). The third ply 120 comprises four boards parallel and oriented along the axis (Ox). The fourth ply 130 comprises four boards parallel and oriented along the axis (Oy). In this “crossed boards” configuration, the plies 100, 110, 120 and 130 consist alternately of parallel boards along the axis (Ox) and parallel boards along the axis (Oy). The structural boards of two adjacent plies are orthogonal to each other and form together a grid covering the whole of the construction element 10.

(15) The boards of the same ply may be oriented in the same direction and are spaced apart from one another so as to cover the whole of the construction element 10 substantially uniformly. These boards are oriented so that the boards of one ply are orthogonal to the boards of an adjacent ply, but a different angle between these boards could also be provided. Moreover, the number of structural boards for each ply results from an arbitration between economy of wood on the one hand and the strength and size of the construction element on the other hand.

(16) A functional board (not shown) may be interposed between two structural boards of the same ply. This functional board is intended to fulfil a specific function, different from that of the structural boards, in other words it does not serve to support the construction element and is not formed from solid wood (but it may be formed from certain types of insulator, such as wood wool, which are not recognised as having load-bearing properties). The choice of its constituent material depends on the function that it is wished to confer on it. This function may relate to thermal and/or sound insulation, to thermal inertia, to fire resistance or to any function considered to be appropriate. In addition, economy of wood requires supplementing the absence of the material in structural boards with functional boards and improving the associated capacity all the more.

(17) As can be seen more precisely in FIG. 3, the structural board 101 has in particular two faces 101A and 101B. The structural board 111 also has in particular two faces, one of which is referenced 111B. When the plies 100 and 110 are placed one on top of the other, the structural boards 101 (depicted in white) and 111 (grooved) come into contact at their respective faces 101A and 111B, which form a contact interface situated in the plane (Oxy).

(18) FIGS. 3 and 4 depict more precisely the contact between two structural boards 101 and 111 of two adjacent plies 100 and 110, according to a first embodiment of the present invention.

(19) In FIG. 3, the structural board 101 has a bottom face 101A (not visible) and a top face 101B. Likewise, the structural board 111 has a bottom face 111A (not visible) and a top face 111B. When the plies 100 and 110 are superimposed, the structural boards 101 and 111 come into contact at a contact interface I.sub.101-111 situated in the plane (Oxy).

(20) As can be seen in FIG. 4, the bottom face 111B of the board 111 is provided with a set of grooved patterns R.sub.111B, over the entire longitudinal extent thereof, that is to say along the axis (Oy). The top face 101A of the board 101 is also provided with a set of grooved patterns R.sub.101A, but only over part of the longitudinal extent thereof, along the axis (Oy). On the faces 101A and 111B, the grooved patterns R.sub.101A and R.sub.111B are complementary and form a series of rectilinear grooves parallel to each other. These patterns are disposed on the faces of the boards so as to cover the contact interface I.sub.101-111. Their forms and dimensions are substantially identical, so that these grooved patterns are substantially complementary to each other.

(21) Thus, when the boards 101 and 111 are placed one on top of the other, the grooved patterns R.sub.101A and R.sub.111B at least partially fit in each other, which makes it possible to form an obstacle to the sliding of the two boards 101 and 111 with respect to one another along a first locking axis B.sub.1, parallel to the axis (Oy), orthogonal to the axis of the grooves (Ox), in the plane (Oxy) of the contact interface I.sub.101-111. This obstacle is obtained without disposing any glue at the contact interface I.sub.101-111, thus avoiding the drawbacks of glue, in particular from the ecological, mechanical and industrial point of view. Moreover, these grooved patterns can serve as references for the fitting together of the boards, in particular in the context of automated assembly.

(22) In this example, the grooved patterns have a cross section with a triangular shape, but other shapes of grooved patterns are possible, in particular shapes with a non-triangular cross section. For example, a square, rectangular or semicircular cross section may be provided.

(23) For the grooved patterns R.sub.101A and R.sub.111B to remain at least partially fitted in one another, at least one holding system is provided for holding the boards against one another at the contact interface. In the example in FIGS. 3 and 4, the holding system comprises two members 30.1 and 30.2, distributed at the contact interface I.sub.101-111, in the form of a metal threaded rod that will be described in more detail below. The holding system thus does not comprise any glue, still in order to avoid—or at least limit—the quantity of glue present in the construction element 10. This holding system provides a holding of the boards 101 and 111 against one another along the axis (Oz) orthogonal to the plane (Oxy) of the contact interface I.sub.101-111. The metal threaded rods have several advantages, including the speed of penetration and the resistance to pulling away in the wood. Holding can therefore be provided more easily, with greater reliability and minimising the risk of splitting the wood.

(24) FIGS. 5 and 6 depict more precisely the contact between two structural boards 101 and 111 of two adjacent plies 100 and 110, according to a second embodiment of the present invention.

(25) In FIG. 5, it can be seen that the general structure and the superimposition of the structural boards 101 and 111 are similar to those in FIG. 3.

(26) In FIG. 6, it can be seen more precisely that the face 111B of the board 111 is provided firstly with grooved patterns R.sub.111B″, in the form of parallel grooves disposed over the entire longitudinal extent of the board, along the axis (Ox), and secondly supplementary grooved patterns R.sub.111B′, in the form of parallel grooves disposed only over part of the transverse and longitudinal extent of the board 111, along the axis (Oy), that is to say orthogonal to the grooves R.sub.111B″. Conversely, the face 101A of the board 101 is provided firstly with the grooved patterns R.sub.101A′, in the form of parallel grooves disposed solely over part of the longitudinal extent of the board 101, along the axis (Ox), and secondly supplementary grooved patterns R.sub.101A″, in the form of parallel grooves disposed over the entire longitudinal extent of the board, along the axis (Oy), that is to say orthogonal to the grooves R.sub.101A′.

(27) In this configuration, the grooved patterns R.sub.101A′, R.sub.101A″, R.sub.111B′, R.sub.111B″ are arranged so as to form an obstacle to the sliding of the first board and the second board with respect to one another along two locking axes B.sub.1 and B.sub.2 non-parallel and situated in the plane (Oxy) of the contact interface I.sub.101-111: the first locking axis B.sub.1, parallel to the axis (Ox), orthogonal to the grooves R.sub.111A′ and R.sub.111B″, and the second locking axis B.sub.2, parallel to the axis (Oy), orthogonal to the grooves R.sub.111A″ and R.sub.111B′. The obstacle to the sliding of the boards 101 and 111 with respect to one another is thus obtained in the whole of the plane of the contact interface I.sub.101-111, without requiring any glue.

(28) In this configuration, the part of the contact interface I.sub.101-111 that comprises the grooved patterns R.sub.101A′, R.sub.101A″, R.sub.111B′ and R.sub.111B″ is in the form of spikes P.sub.101A and P.sub.111B, the ends of which may or may not be sharp according to circumstances, in particular according to the production conditions. In FIG. 6, it can be observed that these spikes form a matrix of barbs, the shape of which is substantially that of a pyramid with a quadrilateral base, in particular with a square base. This form of barb proves easier to machine. It will be understood that other forms of pattern can be envisaged, for example with a triangular base, or with a parallelogram base, in particular in the case where the axes of the grooves are not orthogonal.

(29) In FIG. 5, it can be seen that the boards are held together along the axis (Oz) by a holding system comprising four members 30.1, 30.2, 30.3 and 30.4, all in the form of metal threaded rods. A different number and distribution of these members can nevertheless be envisaged.

(30) It will be understood that, in order to ensure locking of the boards 101 and 111, it suffices for the grooved patterns R.sub.101A′, R.sub.101A″, R.sub.111B′ and R.sub.111B″ to be disposed over at least part of the contact interface I.sub.101-111. Nevertheless, from the mechanical point of view, the locking of the boards will be all the better if the faces are provided with grooved patterns over the entire contact interface I.sub.101-111. Furthermore, from the industrial point of view, the grooved patterns can be produced by machining of the faces 101A and 111B. In this case, the machining can be carried out more easily, cleanly and rapidly over the entire length of the boards, rather than over only part thereof.

(31) In the above examples, the boards 101 and 111 are orthogonal to one another and the locking axes B.sub.1 and B.sub.2 are themselves orthogonal. Other examples may be provided in which the boards 101 and 111 are not orthogonal but inclined with respect to one another, for example by an angle of around 45°. The invention covers more generally any possible inclination between two structural boards.

(32) In order to reinforce the mechanical connection between the grooved patterns of the boards 101 and 111, these are formed from wood from broad-leafed trees. This type of wood has greater density, which makes the grooved patterns—of small dimensions and therefore potentially fragile—stronger and less liable to be pulled away under the effect of mechanical forces. Furthermore, the strength of the assembly having been improved, the invention makes it possible to use wood from broad-leafed trees with smaller cross sections and lower quality, which affords not only savings when the raw material is purchased, but also re-use of this wood usually intended to be burnt in order to produce energy.

(33) According to the present invention, before being held together by the members 30.1 to 30.4, the grooved patterns R.sub.101A′, R.sub.101A″, R.sub.111B′ and R.sub.111B″ are first of all pressed against each other. This prior pressing may be provided by various means within the capability of a person skilled in the art, for example by applying a weight to the top board. In the particular context of boards with grooved patterns, this makes it possible to make the grooved patterns fit in one another more precisely before the members are applied, which improves the precision of assembly. The transmission of the forces and the mechanical strength of the assembly are also improved because of this prior pressing. A suitable pressure for achieving this pressurisation of the boards may be greater than 75 kPa. By way of example, with a contact interface with a square shape of 12 centimetres by 12 centimetres, a pressure of 75 kPa amounts to applying a mass of around 110 kilograms to this interface.

(34) If this pressure increases, in particular if it exceeds a threshold, which may for example be around 150 kPa, the grooved patterns may be slightly deformed. This deformation assists contact and cooperation of the grooved patterns with each other, which improves accordingly the transmission of forces between the boards. With a contact interface with a square shape of 12 centimetres by 12 centimetres, a pressure of 150 kPa amounts to applying to this interface a mass of around 220 kilograms.

(35) FIGS. 7 and 8 show the detail of an arrangement of the members in the case where it is a question of holding three superimposed plies together. The three boards in question are designated by the references 101, 111 and 121, are superimposed in pairs, that is to say the boards 101 and 111 are superimposed at the contact interface I.sub.101-111 and the boards 111 and 121 are superimposed at the contact interface I.sub.111-121. This arrangement may be combined with the previous embodiments. It may in particular be adapted to a greater number of plies and superimposed boards.

(36) In FIG. 7, the holding system comprises a first set of members—or threaded rods—30.1 and 30.2 passing through the boards 101 and 111 at the contact interface I.sub.101-111 and a second set of members—or threaded rods—30.5 and 30.6 passing through the boards 111 and 121 at the contact interface I.sub.111-121. In this way, the two sets of members pass through the intermediate board 111, which ensures continuity in the assembly and holding of the boards together. For the board 111 thus to be doubly passed through, the members 30.1 (and respectively 30.2) are offset with respect to the members 30.5 (and respectively 30.5) in the plane (Oxy) of the two contact interfaces.

(37) This configuration makes it possible to avoid a single member (for example the member 30.1) passing through all the boards 101, 111 and 121. It will be understood that, if this is still possible in a configuration with three plies, the use of the same threaded rod for passing through a configuration for example with seven or eight plies would require a longer rod, and thicker, which would be more expensive and less precise for assembling the boards. On the other hand, with members thus offset, these can be short and the multitude of members locally increases the interactions with the grooved patterns, which improves the transmission of forces.

(38) In FIG. 8, the construction element 10 comprises a number of plies greater than three. Then additional members 30.9 and 30.10 (as well as two other members not shown in the figures) are perforated, in order to hold the board 121 with the boards of the plies situated above it. As can be seen, the members 30.1 (and respectively 30.2) are aligned with the members 30.9 (and respectively 30.10).

(39) The members depicted in FIGS. 7 and 8 are intended to pass through two plies and therefore two boards. In this case, their respective lengths L.sub.30 are substantially equal to the total thickness of the two boards E.sub.101 and E.sub.111 (depicted in FIG. 12) that they pass through and hold together. This has the effect of allowing penetration of the members over the entire thickness of the boards, which increases the proportion of material acted on and in fact improves the resistance to pulling away of the member in the wood.

(40) Alternatively, provision could be made for these members to pass through a larger number of plies and boards. In this case, it remains preferable, according to the invention, that at least one first member passes through a first part of the plies and that a second member passes through a second part of the plies, the first and second parts of the plies having at least one ply in common, the first and second members being at least slightly offset.

(41) FIG. 9 depicts an example of distribution of the various members of the holding system on the contact interface between a plurality of structural boards.

(42) In this configuration, the construction element 10 is formed by at least three superimposed plies, the boards 101 and 111 of which can be seen (the board 121 not being depicted for reasons of clarity). The holding system 30 is provided with a plurality of sets of members, including a first set of four members 30.1, 30.2, 30.3 and 30.4 and a second set of four members 30.5, 30.6, 30.7 and 30.8. The four members 30.1 to 30.4 are provided for holding the boards 101 and 111 against one another at the contact interface I.sub.101-111. The four members 30.5 to 30.8 are provided for holding the boards 111 and 121 (not shown) against one another at the contact interface I.sub.111-121. This configuration therefore repeats the principle of a holding of two boards by four members (as shown in FIG. 5) and the principle of providing members for holding together only some of the boards (as illustrated by FIGS. 7 and 8). The members 30.1 to 30.8 are therefore in the form of metal threaded rods. As can be seen in FIG. 9, the members of the first set and those of the second set are slightly offset, to enable these members to pass through a common board, in this case the board 111, without forming an obstacle.

(43) In order to achieve optimal holding, for each contact interface, the four members of the same set are distributed in the vicinity of the edges of the interface, while ensuring that a separation from the edge is complied with in order to avoid splitting the wood. Thus it is preferred to dispose the members 30.1 to 30.4 depicted in FIG. 9 at a distance D.sub.10-30 from the edge of the interface I.sub.101-111 (depicted in FIG. 12) that lies between 1.5 and 4 centimetres.

(44) FIGS. 10A and 10B show more precisely the positioning of a holding system at the contact interface. As can be seen, the grooved patterns form a set of barbs P. The member 30.1 that is depicted therein is positioned in a hollow of the grooved patterns, designated here by the reference C.sub.1234, at the intersection of the grooves R.sub.T12, R.sub.T34, R.sub.L14 and R.sub.L23. In this case, the diameter of the rod 31.1 of the member 30.1 is such that the extent of the member 30.1 on the contact interface I.sub.101-111 is limited to the four patterns P.sub.1, P.sub.2, P.sub.3 and P.sub.4. The member 30.1 therefore covers only two grooved patterns in each axis, namely the patterns R.sub.L23 and R.sub.L14 in the axis (Ox) and the pattern R.sub.T12 and R.sub.T34 in the axis (Oy). It therefore covers no more than four grooved patterns.

(45) FIGS. 11A and 11B show an example of a metal threaded-rod member 30.1 of the holding system 30, which can be applied to all the members 30.1, 30.2 et seq. that have already been described.

(46) The member 30.1 of length L.sub.30 comprises a metal threaded rod 31 with a roughly cylindrical shape. This rod comprises at the opposite ends thereof a head 32 and a spike 33. The head 32 is formed by two subparts 32′ and 32″ with different diameters. The top part 32′ is provided with a recess complementary to a screwing tool. The rod 31 is provided with a thread, which may be a single or double thread.

(47) In the configuration in FIG. 11A, the thread on the rod 31 comprises two threads 34′ and 34″, interleaved and with different diameters. The advantage of this thread relates to the fact that the performance of a thread depends on its pitch and its diameter. The larger the pitch of the thread, the more quickly the rod penetrates the wood. The larger the thread diameter, the more it works the wood in shearing. The configuration with two interleaved threads with different diameters ensures the local working of the wood in two different shear planes, which increases the mechanical strength of the assembly and reduces the penetration time of the screw.

(48) It is nevertheless important that the thread should remain sufficiently narrow, in particular for boards made from wood from broad-leafed trees. Thus the ratio between the largest diameter of the thread and the diameter of the rod is preferentially between 1.5 and 1.7.

(49) The invention also proposes a method for manufacturing a construction element 10 as described above. This method involves starting from structural boards already provided with grooved patterns on their respective contact interfaces. Alternatively, provision may be made for providing these boards with grooved patterns, for example by machining their faces intended to be superimposed.

(50) According to the invention, the boards 101 and 111 already provided with grooved patterns R.sub.101A and R.sub.111B are superimposed so that these grooved patterns come into contact with one another at the contact interface I.sub.101-111. In this regard, advantage can be taken of the complementary shape of the grooved patterns R.sub.101A and R.sub.111B in order to bring them together until they fit together at least partly, which makes it possible to perform this superimposition step with high precision.

(51) Subsequently, the boards 101 and 111 are put under pressure, that is to say pressed against one another, at the contact interface I.sub.101-111. The grooved patterns R.sub.101A and R.sub.111B are thus pre-pressed before actually being held together. This pressurisation step can be achieved by various means within the capability of a person skilled in the art, for example by applying a weight on the top board. Suitable pressure may be greater than 75 kPa, as already indicated above. According to the pressure level, the grooved patterns will be fitted together (which is not, most of the time, allowed by a simple superimposition) or even crushed and thus slightly deformed, which improves the transmission of forces between the boards thus superimposed and the mechanical strength of the assembly.

(52) Finally, the boards 101 and 111 thus superimposed and put under pressure can be held against one another by means of a holding system 30 according to the invention, in particular one or more threaded metal rods disposed at the contact interface I.sub.101-111 and passing through the thickness of the boards. The boards are then held against one another, not only with high positioning precision but also with better transmission of forces between them.

(53) This method may be repeated in order to assemble all the boards and all the plies of the same construction element 10, thus allowing complete fabrication.

(54) Naturally, the present invention is not limited to the examples and embodiments described and depicted, but is capable of numerous variants accessible to a person skilled in the art. In particular the various forms of connectors that have been described above—as well as other forms within the capability of a person skilled in the art on reading the present description—may be combined within the same construction system, according to the advantages of each and the specific requirements of the construction system.