WO2004080674A1

WO2004080674A1 - A method and arrangement to glue and deform wooden boards and the product

Info

Publication number: WO2004080674A1
Application number: PCT/SE2004/000346
Authority: WO
Inventors: Per Hobro
Original assignee: Per Hobro
Priority date: 2003-03-10
Filing date: 2004-03-09
Publication date: 2004-09-23
Also published as: SE0300616L; SE0300616D0

Abstract

A method for gluing together two or more wooden bodies with each other, the bodies comprising at least one gluable surface each, the method comprising the steps: - applying glue on at least one of the gluable surfaces which are to be glued, - bringing the gluable surfaces which are to be glued into contact with each other, and - applying a pressure on the bodies such that said gluable surfaces which are to be glued are pressed against together, wherein the method.

Description

A METHOD AND ARRANGEMENT TO GLUE AND DEFORM WOODEN BOARDS

AND THE PRODUCT

FIELD OF THE INVENTION

The invention relates to a method for gluing together two or more wooden bodies, the bodies comprising at least one gluable surface each. The method comprises the steps applying glue on at least one of the gluable surfaces to be glued, bringing the gluable surfaces, which are to be glued, into contact with each other and applying a pressure on the bodies such that said glu- able surfaces, which are to be glued, are pressed together. The invention also relates to a device for gluing together two or more wooden bodies and a product composed by two or more wooden bodies glued together.

BACKGROUND OF THE INVENTION AND PRIOR ART

When producing for example boards or other forms of wooden elements a piece of wood is usually sawn out from a log, which piece of wood resembles the shape of the desired wooden ele- ment. The piece wood is dried, at which the piece of wood due to for instance the annular rings in the wood, is bent and changes shape when the water evaporates. In order to obtain the desired shape from the element of wood the dried piece of wood is planed such that the desired element of wood is ob- tained. For example during production of boards a piece of wood is sawn out having a substantially rectangular cross section. During the drying the piece of wood is bent such that the cross section becomes slightly curved. The piece of wood is then planed such that the cross section once again becomes non- bent and rectangular, which gives the desired board. During such planing a lot of material is lost, usually between 5-15% and sometimes as much as 20% of the material.

For other applications too, for example when a bent shape of a wooden element is desired, material is removed from a larger piece of material in order to obtain the desired shape. This is done for example when bowl-shaped elements are to be produced, at which material is removed from a substantially rectangular piece of wood such that the rounded shape is obtained. This also leads to great waste of material causing high costs, in particular when large volumes of wood are processed.

In some applications it is suitable to glue together several wooden bodies in order to obtain a composite glued together product of wood. One example of such a glued together product of wood is wooden beams for example for roof frames in houses or other applications. Such beams comprise several elongate wooden elements having a substantially rectangular cross section and being glued together with each other. By gluing several wooden elements into a beam the beam receives a greater strength and tenacity than if the beam would be produced in one homogenous piece. There are also other such applications in which several wooden bodies are glued together into a composite glued wooden body in order to obtain improved characteris- tics.

SUMMARY OF THE INVENTION

The object of the present invention is to decrease the total cost during production of a glues composite product of wood.

This object is achieved with the method according to the introduction of claim 1 and being characterised in that the pressure applied is greater than or equal to a pressure implying that at least one wooden body is deformed and that the deformation is substantially retained even after the gluing process and removal of the pressure.

It has now been realised that when a high pressure is applied towards a wooden body, the wooden body enters a plastic state in which the wooden body may be deformed and changed in shape substantially permanently, which previously has been considered as unfeasible. This is particularly suitable to use during gluing together of wooden bodies to each other, wherein the glue joint between the wooden bodies also facilitate the retention of the wooden bodies in their new shape. Thus another shape may be achieved for a product comprising several wooden bodies glued together without need for removal of material from an originally larger piece of wood, which would lead to waste of material. Thus a saving of material is obtained, which lowers the total cost for production of the product. Further a second processing step, namely the processing step planing or some other step for removal of material, may be partly or fully eliminated. Thus the cost for producing the product may be de- creased further. Preferably a wooden body is deformed through bending the shape of the wooden body. Thus the change in shape achieved by the method may be used to counteract the bending of the wooden elements arising when drying of the wood. This gives a further decrease of the use of material and thus gives a saving of costs.

According to one embodiment of the invention said pressure is applied substantially perpendicularly relative to said gluable surfaces of the bodies and distributed across the bodies such that at least one body obtains a new desired shape after the gluing. That the pressure is applied substantially perpendicular means that it is the same pressure that presses the gluable surfaces of the bodies towards each other that achieves the change in shape. That is it is the pressure being perpendicular relative to the gluable surfaces that achieves said change in shape. That the force is distributed across the bodies means that the bodies obtain a smooth shape. Further it is demanded that the pressure is distributed across substantially the entire bodies such that substantially all parts of the bodies enters said plastic state. Preferably the pressure is also distributed across the bodies such that the bodies remain intact after the gluing such that no damages are inflicted on the bodies and such that the bodies are not cracked, broken or receives any marks. Preferably the pressure is also distributed substantially equally across the bodies with respect to a plane substantially in parallel with the glu- able surfaces. That the pressure is distributed perpendicular in this way does not mean that the body may not be subjected to other forces also. For example lateral forces may be applied for holding the bodies, which forces preferably do not change the shape of the bodies in any substantial degree.

According to a further embodiment of the invention the body is deformed such that the shape of the cross section of the body is changed for at least a major part of the body. Thus the bending obtained from drying the wood is counteracted such that the bodies receive a more planar shape. Preferably the bodies are elongate and preferably the cross section perpendicular to the length direction is changed for at least a major part of the body. If the bodies are elongate and are taken from the outer part of a log the annular rings are arranged such that the body becomes curved in its cross section. It is thus advantageous to deform the cross section of the bodies, which counteracts the bending from the drying. Further it is especially advantageous to change the shape of the cross section of the wooden bodies since the material, which previously would have been planed off from such a cross section, is as thin as it could not have been used for any other purpose.

According to a further embodiment of the invention said pressure is applied at least for a time corresponding to a substantial part of a curing time of the glue. Thus the pressure is applied sufficiently long for the glue to contribute to maintain the bodies in their new attained shape after the deformation.

According to a further embodiment of the invention said pres- sure is larger than or equal to 30 bar. Different types of wood receive a permanent change in shape at different applied pressures. With a pressure larger than or equal to 30 bar substantially all types of wood may be changed in shape. Preferably said pressure is larger than or equal to 50 bar. Thus at least the types of wood most important for usage may be changed in shape. For example a pressure between 50 and 75 bar is suitable for changing the shape of fir. According to a further advantageous embodiment the pressure is larger than or equal to 75 bar. A pressure between 75 and 100 bar is the most suitable pressure for changing the shape of harder types of wood, for example birch. According to a further advantageous embodiment the pressure is larger than or equal to 100 bar. Such a high pressure is suitable for changing the shape of very hard types of wood. Further a larger pressure may also improve the retention of the new shape of the bodies.

According to one embodiment of the invention the applied pressure is less than 300 bar. Preferably the applied pressure is less than 200 bar. Most preferably the applied pressure is less than 150 bar. The optimum pressure range for achieving a plastic state suitable for changing the shape of a wooden body is for pressures beneath this pressure. Aditionally, cells in the wood are pressed together at high pressures, which decrease the size of the wooden body. This is also called compression. Compres- sion increases the hardness and strength of the wooden body as seen per unit of volume, which is used in some applications to increase the carrying capacity of wood. The pressure thus used is usually larger than 850 bar. But the carrying capacity of wood also depends on the size of the bodies, thus a compression of a particular wooden body does not increase the total carrying capacity of that wooden body. Thus it is more material saving to minimise the compression of the wooden bodies. A certain compression of the wooden bodies is however difficult to avoid with the method according to the invention. According to an alternative embodiment of the invention the applied pressure is less than 125 bar, preferably less than 100 bar. Thus both the size of the compression and the risk for damages to occur on the wooden bodies is decreased.

According to a further embodiment of the invention said pres- sure is larger than 300 bar. Thus the permanent change in shape of said wooden bodies is combined with compression of the wooden bodies. This is advantageous in applications where a very high strength is necessary.

According to a further embodiment of the invention said wooden bodies are dried and non-planed elongate wooden elements having a substantially rectangular cross section, wherein the wooden elements are glued together into one or more beams of wood. This is an area of application in which the invention is very well suited for saving material. During drying of the elongate wooden elements the cross section of the wooden elements are bent such that the cross section only is substantially rectangular. By using the method the wooden elements are changed in shape such that the cross section in principal becomes straight rectangular after the gluing with exception for natural variations. Thus a shape of the wooden elements is obtained which is well suited to be glued together into beams of wood. Further the cost for manufacturing the beam decreases since the refuse from a planing step is markedly reduced.

A further object of the present invention is to indicate a device arranged to decrease the total cost during gluing of two pieces of wood into a composite product.

This object is achieved with the device described in the introduction of claim 13 and being characterised in that the member is arranged to apply a pressure being larger than or equal to a pressure implying that at least one wooden body is deformed and that the deformation substantially is retained even after the gluing process and removal of the pressure. This device shows the advantages as indicated in the description of the method shown above. The device can also be arranged or shaped to achieve or carry out any of the steps or variations of the embodiments of the method according to the invention according to any of the claims 2 to 12. In particular, the device is preferably shaped to apply a pressure variable between 30 and 150 bar, or between any other pressures as indicated.

A further object of the present invention is to indicate a product being produced such that it decreases the total cost during pro- duction of the product.

This object is achieved with the product as described in the introduction of claim 14 and being characterised in that at least one of the bodies is deformed by an applied pressure during the gluing of the bodies according to the method in claim 1 .

SHORT DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a device according to the invention.

Figs. 2a-b show a product composed by two elongate wooden bodies having substantially rectangular cross sections in two different steps of the invention.

Figs. 3a-d show a product composed by wooden bodies having a substantially cylindrical shape in two different steps of the invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In Fig. 1 a device 1 is shown being arranged to carry out the method according to the invention. The device 1 is only de- scribed schematically and may thus be provided with a number of improvements described within the prior art for pressure or pressing devices. The device 1 comprises a mounting 3 comprising a work surface 5 on which a number of wooden bodies 7 that are to be glued together may be positioned. The device 1 also comprises a stopping member 9 being arranged in connection with the working surface 5 and being arranged to prevent displacement of the bodies 7 on the working surface 5. The device 1 further comprises a force generating member of any type, for example a hydraulic force generating member or an electric engine, being contained in a force generator house 11 . The device further comprises a member 13 being connected with the force generator and being arranged to apply a pressure on the bodies 7 on the working surface 5. In this example the force generator is a hydraulic cylinder and the member 13 is con- nected with the force generator by a cylinder piston 15.

The bodies 7 of wood are in this example dried and non-planed elongate wooden elements 7. The wooden elements 7 thus have a substantially rectangular cross section, except for a slight bending of the cross section due to drying of the wooden elements 7. The cross section of the wooden elements 7 is thus slightly arched or U-shaped. Further the bodies 7 comprise at least one gluable surface 8 each. In this example the bodies 7 comprise two gluable surfaces 8 each.

In this example the bodies 7 are intended to be glued together into one or more beams of wood. At the carrying out of the method glue is applied on at least some of the gluable surfaces 8 which are to be glued. The bodies 7 are then positioned in parallel with each other on the working surface 5 and the gluable surfaces of the bodies 7 are brought into contact with each other in pairs. It is sufficient that glue has been applied on one gluable surface 8 for each pair of surfaces, since the glue is then transferred to the second surface of the pair. Some pairs of gluable surfaces can also be left without glue, wherein several thinner beams of wood may be manufactured at the same time.

The pressing member 13 is then induced to apply a pressure against the bodies 7 such that said gluable surfaces that are to be glued are pressed together. The pressure is then applied substantially perpendicular relative to said gluable surfaces of the bodies 7. The pressure is achieved by the force generator and is transmitted to the pressing member 13 by the cylinder piston 15. The pressure applied is larger than or equal to a pressure implying that at least one of the wooden bodies 7 is deformed and that the deformation is substantially retained even after the gluing process and removal of the pressure.

Because of the pressure the bodies 7 change shape, wherein the bodies substantially are shaped according to the shapes of the pressing member 13 and the stopping member 9. In this example the pressing member 13 and the stopping member 9 are substantially planar, wherein the previously slightly curved rectangular cross sections of the bodies 7 are straightened during the gluing process and become substantially straight rectangu- lar. Depending on the shape of the stopping member 9 and the pressing member 13 the pressure is thus distributed across the bodies 7 such that the bodies 7 obtains a new shape. In this example the pressure is thus distributed substantially equally across the bodies with respect to a plane parallel to the gluable surfaces 8, such that the pressure is also distributed equally across the bodies 7. Thus the risk of breaking the bodies 7 is decreased. Further the pressing member 13 and the stopping member 9 have such a size and shape such that the shape of the cross section of the bodies 7 is changed for at least a major part of each respective body 7. Thus the cross section perpen- dicular to the length direction is changed for at least a major part of the bodies 7.

Further the device 1 is shaped to apply said pressure for at least a time corresponding to a substantial time of a curing time of the glue. Thus it is secured that the mutual positions of the bodies is maintained. Further the pressure applied by the pressing member 13 is less than a pressure at which the wooden bodies 7 permanently are compressed. Further the pressure is less than a pressure at which the wooden bodies 7 run the risk of breaking.

The device 1 further comprises a second pressing member 17, which, in this example, is arranged to press against the bodies 7 from above. The second pressing member 17 thus presses on the long sides of the bodies 7. The second pressing member 17 is arranged to secure that the bodies 7 are kept in position during the gluing process and are not displaced or come off from the device 1 . In another example the device may also comprise a third and a fourth pressing member for pressing sideways on the short sides of the bodies 7. Alternatively, the pressing members mentioned here may instead be constituted by members corresponding to the stopping member 9 described above.

The first pressing member 13 and the power generator are arranged to be able to apply a pressure between 50 and 150 bar on the bodies 7. Within this range of pressure lies the optimum pressure for changing the shape of most types of woods, and thus the device may be used to change the shape of most types of wood. For example a beneficial pressure for changing the shape of fir wood is between 50 and 75 bar and a beneficial pressure range for birch wood is between 75 and 100 bar.

In Fig. 2a, two wooden bodies 22a, 22b are shown, which com- prise one gluable surface 24 each. Only the gluable surface 24 of the lower body 22b is shown in Fig. 2a while the gluable sur- face of the upper body 22a is hidden, but it is in all essentials similar in nature. The bodies 22a, 22b are shown in Fig. 2a in one step according to the method according to the invention, in which the bodies 22a, 22b are not yet glued together. In Fig. 2b the bodies 22a, 22b are shown glued together according to the method according to the invention into a product 20, which in this example is a beam of wood. The bodies 22a, 22b are thus deformed by an applied pressure during the gluing of the bodies 22a, 22b.

In Fig. 2a it is seen that the cross sections of the bodies 22a, 22b, before the gluing, are substantially rectangular but slightly curved due to a previous drying of the bodies 22a, 22b. The curvature is obtained during the drying because of the annular rings in the wood. During the gluing of the bodies 22a, 22b into the product 20 in the form of a beam of wood according to the method according to the invention, firstly, in the step in Fig. 2a, glue is applied on the gluable surfaces 24. Then the two gluable surfaces 24 are brought into contact with each other. In one ex- ample of the invention glue is only applied on one of the two gluable surfaces. When the gluable surfaces 24 later are brought into contact with each other glue is transferred from the surface 24 provided with the glue to the surface without glue.

A pressure is then applied on the bodies such that said gluable surfaces 24 are pressed against each other. The pressure applied is larger than or equal to a pressure implying that at least one of the wooden bodies 22a, 22b is deformed and that the deformation is substantially retained even after the gluing process and removal of the pressure. In this example both bodies 22a, 22b are deformed such that the bodies 22a, 22b obtain a more planar form with a straighter rectangular cross section.

In this example the pressure is distributed substantially equally across the bodies with respect to a plane parallel to the gluable surfaces 24. Thus it is provided that substantially all parts of the bodies are subject to a sufficiently high pressure in order for them to enter a plastic state allowing substantially permanent deformation. Further the pressure is distributed across the bodies 22a, 22b with a higher pressure against the parts shown by the arrows in Fig. 1 a, at least in an initial phase of the gluing. In the figure it is seen that the pressure against the topmost body 22a is higher along the middle of the body 22a, wherein the body is thus deformed such that the middle part is pressed downwardly. Further the pressure against the lowermost body 22b is higher along the sides of the body 22b, wherein the lower body 22b is deformed such that the sides are pressed upwardly. Thus the bodies are deformed such that the bodies 22a, 22b obtain a more planar shape during the gluing. In this example it is the cross section perpendicular to the length direction of the bodies 22a, 22b which is changed in shape such that the cross section of the bodies 22a, 22b obtains a more planar and substantially straight rectangular shape. Thus the beam of wood 20 becomes straight even though the bodies 22a, 22b have not been planed before the gluing of the beam of wood 20. It is real- ised by a man skill in the art that since both the bodies 22a, 22b bear on each other a pressure applied towards one body is transmitted through that body such that the pressure also influences the second body in the same way as the first.

In Fig. 3a two additional wooden bodies 32a, 32b are shown before the gluing together of the wooden bodies 32a, 32b. In this example the bodies 22a, 32b are substantially planar cylindrical discs of wood, the end surfaces 34 of which are gluable. In Fig. 3b the wooden bodies 32a, 32b are shown glued together ac- cording to the method according to the invention into a product 30, which is substantially bowl-shaped.

These wooden bodies 32a, 32b are also glued together according to the method according to the invention while applying a pressure on the bodies 32a, 32b such that the wooden bodies 32a, 32b are deformed and change shape. In this example the applied pressure is distributed across one body 32a such that the pressure is higher along the periphery of the body 32a, and on the second body 32b the pressure is distributed such that the pressure is higher substantially in the middle of the end surface of the second body 32b. Thus the bodies 32a, 32b are deformed such that the product 30 becomes substantially bowl-shaped. A device adapted to achieve such a bowl-shape preferably comprises a pressing member, which is bowl-shaped and a stopping member, which is ball-shaped, but naturally it can also be the other way round.

This example shows that the device and method according to the invention thus not only can be used to counteract bending of curved wooden bodies, but can also be used to bend plane wooden bodies. In order to obtain such a bent shape it would otherwise have been necessary to use a very large piece of wood as original material, after which the piece of wood would have been machined and material removed from the piece of wood in order to obtain the bent shape. By the method accord- ing to the invention large amounts of material may thus be saved.

Preferably the gluing is carried out during dry conditions, wherein no further drying of the finished product is necessary. Preferably the humidity during the gluing is below 70%.

The embodiments described herein shall only be seen as examples of the invention, which can be varied freely within the framework of the following claims.

Claims

1. Method for gluing together two or more wooden bodies (7, 22a-b, 32a-b) with each other, the bodies (7, 22a-b, 32a-b) comprising at least one gluable surface (8, 24, 34) each, the method comprising the steps: applying glue on at least one of the gluable surfaces (8, 24, 34) which are to be glued, bringing the gluable surfaces (8, 24, 34) which are to be glued into contact with each other, and applying a pressure on the bodies (7, 22a-b, 32a-b) such that said gluable surfaces (8, 24, 34) which are to be glued are pressed together, the method being characterised in that the pressure applied is larger than or equal to 30 bar and is larger than or equal to a pressure implying that at least one of the wooden bodies (7, 22a-b, 32a-b) is deformed and that the deformation substantially is retained even after the gluing process and removal of the pressure.

2. A method according to claim 1 , characterised in that said pressure is applied substantially perpendicular in relation to said gluable surfaces (8, 24, 34) of the bodies (7, 22a-b, 32a-b), and is distributed across the bodies such that at least one body (7, 22a-b, 32a-b) obtains a new desired shape after the gluing.

3. Method according to claim 1 or 2, characterised in that the pressure is distributed substantially equally across the bodies (7, 22a-b, 22a-b) with respect to a plane substantially parallel with the gluable surfaces (8, 24, 34).

4. Method according to any of the previous claims, characterised in that the body (7, 22a-b, 32a-b) is deformed such that the shape of the cross section of the body (7, 22a-b, 32a-b) is changed for at least a major part of the body (7, 22a-b, 32a-b).

5. A method according to claim 4, characterised in that the bodies (7, 22a-b) are elongate and that the cross section perpendicular to the length direction is changed for at least a major part of the body (7, 22a-b).

6. Method according to any of the previous claims, characterised in that said pressure is applied at least during a time corresponding to a substantial part of a curing time for the glue,

7. A method according to any of the previous claims, charar- terised in that said pressure is larger than or equal to 50 bar.

8. A method according to any of the previous claims, charar- terised in that the applied pressure is less than 200 bar.

9. A method according to any of the previous claims, characterised in that the applied pressure is less than 150 bar.

10. A method according to any of the previous claims, charar- terised in that said wooden bodies (7, 22a-b) comprise dried and rough sawn wooden elongate elements (7, 22a-b) having a substantially rectangular cross section, wherein the wooden elements (7, 22a-b) are glued together into one or more beams of wood (20).

1 1 . A device for gluing together two or more wooden bodies (7, 22a-b, 32a-b), the bodies (7, 22a-b, 32a-b) comprising at least one gluable surface (8, 24, 34) each, the device comprising a member (15) arranged to apply a pressure on the bodies (7, 22a-b, 32a-b) for pressing together the gluable surfaces (8, 24, 34) during the gluing of the bodies (7, 22a-b, 32a-b), characterised in that the member is arranged to apply a pressure being larger than or equal to 30 bar and being larger than or equal to a pressure implying that at least one wooden body (7, 22a-b, 32a-b) is deformed and that the deformation substantially is re- tained even after the gluing process and removal of the pressure.

12. A product (20, 30) composed of two or more wooden bodies (7, 22a-b, 32a-b) glued together, characterised in that at least one of the bodies (7, 22a-b, 32a-b) is deformed by a pressure applied during the gluing of the bodies (7, 22a-b, 32a-b) according to the method in claim 1 .