WOOD CONNECTION AND A LAMINATED WOOD TOWER COMPRISING A PLURALITY OF SUCH WOOD CONNECTIONS

Abstract

Wood connection for large wooden constructions comprising a first wood module, a second wood module and a perforated steel plate comprising a plurality of holes, where the first wood module and the second wood module comprises a plurality of laminated wood layers, where each wood layer comprises a plurality of laminated veneer plies, where a first part of the perforated steel plate is mounted in the first wood module with glue, and where a second part of the perforated steel plate is mounted in the second wood module with glue, with a centreline of the perforated steel plate aligned with a split line between the first wood module and the second wood module, and where the perforated steel plate has a tensile strength exceeding 700 MPa and that a wood module is at least 6 cm thick and has a tensile strength exceeding 20 MPa.

Claims

1. A wood connection for large wooden constructions comprising: a first wood module, a second wood module and a perforated steel plate comprising a plurality of holes, where the first wood module and the second wood module comprises a plurality of laminated wood layers, where each wood layer comprises a plurality of laminated veneer plies, where a first part of the perforated steel plate is mounted in the first wood module with glue, and where a second part of the perforated steel plate is mounted in the second wood module with glue, with a center line of the perforated steel plate aligned with a split line between the first wood module and the second wood module, wherein the perforated steel plate has a tensile strength exceeding 700 MPa and that a wood module is at least 6 cm thick and has a tensile strength exceeding 20 MPa.

2. The wood connection according to claim 1, wherein the perforated steel plate is arranged perpendicular to an inner surface and an outer surface of the laminated wood modules.

3. The wood connection according to claim 1, wherein a wood module is flat.

4. The wood connection according to claim 1, wherein a wood module is curved in a longitudinal direction of the wood module.

5. The wood connection according to claim 4, wherein a laminated wood layer comprises a first set of plies comprising a plurality of veneer plies and where the wood grain is directed in a first direction, and a second set of plies comprising one or more veneer plies arranged adjacent each other and where the wood grain is directed in a second direction, where the first direction is perpendicular to the second direction.

6. The wood connection according to claim 1, wherein the first part and the second part of the perforated steel plate are symmetrical with respect to the center line of the perforated steel plate, and where the width of the perforated steel plate is at least 60 mm, and the length of the perforated steel plate is at least 500 mm.

7. The wood connection according to claim 1, wherein the holes of the perforated steel plate are circular, where the diameter of each hole is 10 mm.

8. The wood connection according to claim 1, wherein the hole density of the perforated steel plate is reduced adjacent the center line of the perforated steel plate.

9. The wood connection according to claim 1, wherein each side edge of the perforated steel plate comprises at least one protrusion which extends 1 mm over the surface of the perforated steel plate.

10. The wood connection according to claim 1, wherein the distance from the center line to a hole closest to the center line is at least 20 mm.

11. The wood connection according to claim 1, wherein a perforated steel plate comprises at least 6 holes.

12. The wood connection according to claim 1, wherein the perforated steel plate is at least 2 mm thick.

13. The wood connection according to claim 1, wherein the thickness of a ply is between 1-5 mm.

14. The wood connection according to claim 1, wherein a laminated wood layer comprises between 5-15 plies.

15. A laminated wood tower, wherein the laminated wood tower comprises a plurality of wood connections according to claim 4.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0023] The invention will be described in greater detail in the following, with reference to the embodiments that are shown in the attached drawings, in which

[0024] FIG. 1 shows an example of a wood connection according to the invention in a curved wood module,

[0025] FIG. 2 shows an example of a wood layer to be used in a wood module,

[0026] FIG. 3 shows an example of a perforated steel plate used in a wood connection according to the invention,

[0027] FIG. 4 shows a further example of a perforated steel plate used in a wood connection according to the invention,

[0028] FIG. 5 shows an example of a laminated wood tower comprising a plurality of wood connections according to the invention, and

[0029] FIG. 6 shows an example of a wind power tower according to the invention.

MODES FOR CARRYING OUT THE INVENTION

[0030] The embodiments of the invention with further developments described in the following are to be regarded only as examples and are in no way to limit the scope of the protection provided by the patent claims. The directional references used refer to directions of a curved wood module when used in a laminated wood tower.

[0031] FIG. 1 shows a first example of a wood connection. The wood connection 1 comprises a first wood module 2, a second wood module 3 and a perforated steel plate 4. The first wood module 2 and the second wood module 3 both comprise a plurality of laminated layers 17. The first wood module 2 and the second wood module 3 preferably have the same layout with the same amount of laminated layers of the same type. In one example, a module comprises five layers. The layers are press glued to each other such that a solid wood module 2, 3 is obtained. A wood module is provided with an upper edge, a lower edge, a first side surface, a second side surface, an inner surface 21 and an outer surface 22. In the shown example, the wood modules are curved in one direction, but the wood modules may also be flat. A layer 17 comprises a plurality of laminated veneer plies 18. In a flat layer, the direction of the fibres of the veneer plies may be selected freely, and may e.g. be directed in the same direction. Some plies may also be arranged with the direction of the fibres directed in a perpendicular direction when compared to the other plies. In one example, every second ply is arranged in one direction, and the other plies are directed perpendicular those plies.

[0032] A wood layer for a curved module is shown in FIG. 2. In the shown wood layer 17, the direction of the fibres of the veneer plies 18 of a first set of plies are directed in the same direction. The first set of plies 19 contain most of the plies, and preferably at least 80% of the number of plies. A layer further comprises a second set of plies 20 comprising one or more plies with the direction of the fibres directed in a perpendicular direction when compared to the first set of plies. Preferably, the second set of plies comprise one ply, but may comprise two veneer plies arranged adjacent each other.

[0033] The second set of plies 20, i.e. the set of plies having a grain direction perpendicular to the first set of plies 19 of a layer, may be arranged at any position of the layer, but is preferably arranged close to one side of the layer. In one example, the second set of plies is arranged as the outermost set of plies of a layer. In another example, the second set of plies is arranged within the first set of plies. A first part of the first set of plies is now arranged on one side of the second set of plies, and a second part of the first set of plies is arranged on the other side of the second set of plies. The use of a single set of plies arranged in a crosswise manner will strengthen the layer and will still allow the layer to be bent to a curved shape.

[0034] The wood modules are connected to each other by the use of a perforated steel plate 4. A first example of perforated steel plate is shown in FIG. 3. Each wood module is provided with a slit 11 for each perforated steel plate. In the shown example, a slit 11 runs in a cross direction of a wood module, i.e. from the outer surface to the inner surface of the wood module, perpendicular to the inner surface 21 and the outer surface 22 of a wood module. In other applications, especially for flat modules, a slit may also run parallel to the outer surface. The slit may be cut by e.g. a circular saw or a router. One advantage of using a router is that the slit must not continue through the complete wood module. With a router, a thin wall can be left at the outer surface of the wood module. In this way, the outer surface of the wood module will be closed. This will allow the wood module to have a smooth outer surface that does not have to be patched to cover the slit in the outer surface.

[0035] The width of the slit is wider than the perforated steel plate. Preferably, a nominal gap of 1 mm between the perforated steel plate and each side wall of the slit is provided. The perforated steel plate 4 is preferably provided with one or more protrusions 16 that will provide a distance means for the perforated steel plate, such that a desired gap is created when the steel plate is positioned in a gap. A protrusion preferably extends 1 mm from the surface of the perforated steel plate in each direction, corresponding to the nominal gap of the slit. This will allow the perforated steel plate to be centralized in the slit during mounting, such that the glue can spread evenly on both sides of the perforated steel plate. The protrusions are preferably embossed into the perforated steel plate during manufacture.

[0036] A perforated steel plate may have different shapes, but a rectangular shape is preferred. The perforated steel plate comprises a first part 14 and a second part 15 divided by a centre line 13. The perforated steel plate is symmetrical with respect to the centre line, such that the first part and the second part are identical. The first part is adapted to be mounted in a first wood module, and the second part is adapted to be mounted in a second wood module, with the centre line 13 arranged at the split line of the connection, aligned with the upper edge of a first wood module 2 and the lower edge of a second wood module 3. The width of the perforated steel plate will depend on the thickness of the wood module, but is at least 60 mm, and the length is at least 500 mm. The thickness of the perforated steel plate is preferably between 2-4 mm.

[0037] The perforated steel plate 4 comprises a plurality of holes 12. The holes are in the shown example circular, but other shapes are also possible, such as elliptic or oval holes. A circular hole preferably has a diameter of 10 mm, but other sizes are possible. The holes are positioned with a predefined distance to the other holes, and have a predefined distance to the sides of the perforated steel plate. There is further a predefined distance between the centre line of the perforated steel plate and the closest holes. The holes may be placed in rows and columns, or may be positioned with an offset arrangement. It is also possible to vary the hole density of the perforated steel plate. FIG. 4 shows an example of a perforated steel plate where the hole density closest to the centre line is reduced.

[0038] The perforated steel plate is mounted to a wood module by the use of glue. The glue is preferably injected into the slit after the perforated steel plate has been positioned in the slit. It is also possible to fill the slit with a predefined amount of glue and to insert the perforated steel plate thereafter. In this case, it is of advantage to vibrate the perforated steel plate such that air can escape.

[0039] When a perforated steel plate is positioned in a slit, glue is injected into the slit such that half of a perforated steel plate is glued to a wood module. An open side of the slit is preferably covered before glue is inserted, such that the slit is completely filled and that the glue does not escape during hardening. Tape or the like may be used to cover the slit of the wood module.

[0040] Preferably, the perforated steel plates are mounted to the wood modules during assembly of the end product. The number of perforated steel plates used for a module is defined by calculation of the required forces that the joint must withstand. Different types of glue may be used. A suitable glue is a two-component glue, e.g. based on an epoxy resin, but other types may also be used, such as moisture cured polyurethanes. The glue is preferably injected from the lowest part of the slit, such that the glue will be able to spread evenly and such that no air bubbles are enclosed. The glue may be injected through a drilled injection hole that is plugged after the injection.

[0041] The wood connection 1 may be used to connect laminated veneer lumber wood modules of different sizes and shapes. In one example, the wood connection is used for mounting a laminated wood tower 30, where curved modules 2, 3 are mounted to each other to form circular sections 31, where each circular section comprises a plurality of curved modules 2, 3. An example of a laminated wood tower is shown in FIG. 5. The circular sections are then mounted to each other to form the laminated wood tower by the use of wood connections 1. The mounting of the curved modules to form a circular section may be made with a specific joint, which could comprise e.g. rabbets of a curved module that cooperates with rabbets of an adjacent curved module, where the curved modules may lock to each other. It is also possible to use overlapping joints, where some layers of a curved module overlap some layers of an adjacent curved module. The curved modules are preferably mounted to each other in a sideway direction with glue and screws. It is also possible to use perforated steel plates to mount the curved modules to a circular section.

[0042] The circular sections are mounted to each other by using the inventive wood connection 1. The wood connection can withstand the tensile forces that arise when the wind turbine is subjected to air forces. One side of the tower will be subjected to compression forces, which will be handled by the wood modules, and the other side will be subjected to tensile forces which will be handled by the curved wood modules and the wood connections. The wood connection is thus designed to correspond to the same tensile load capacity as the curved modules. Bending and torsional forces will be handled by the cross lamination of the curved modules.

[0043] FIG. 6 shows an example of a wind power tower 40 comprising a laminated wood tower 30. The shown wind power tower may be up to 100 meters and more, and is in the shown example tapered somewhat towards the top of the tower. The tower is fixed to a foundation 41, e.g. comprising steel bars extending up in the tower, to which the lower wooden section is attached with e.g. screws. A door may be provided in one of the lower curved modules. On top of the tower, a nacelle 42 comprising a rotor 43 and a generator is provided. Depending on the type of generator used, a transmission may also be installed.

[0044] The invention is not to be regarded as being limited to the embodiments described above, a number of additional variants and modifications being possible within the scope of the subsequent patent claims. A curved module may be used for other circular objects, such as wooden tubes, and may have various sizes. Straight wood sections may be used e.g. for larger walls in wooden housings.

REFERENCE SIGNS

[0045] 1: Wood connection [0046] 2: First curved module [0047] 3: Second curved module [0048] 4: Perforated steel plate [0049] 11: Slit [0050] 12: Hole [0051] 13: Centre line [0052] 14: First part [0053] 15: Second part [0054] 16: Protrusion [0055] 17: Wood layer [0056] 18: Veneer ply [0057] 19: First set of plies [0058] 20: Second set of plies [0059] 21: Inner surface [0060] 22: Outer surface [0061] 30: Laminated wood tower [0062] 31: Circular section [0063] 40: Wind power tower [0064] 41: Foundation [0065] 42: Nacelle [0066] 43: Rotor