WO1998000270A1

WO1998000270A1 - A method, a device and a use in gluing

Info

Publication number: WO1998000270A1
Application number: PCT/SE1997/001138
Authority: WO
Inventors: Lars Hammarström
Original assignee: Hammarstroem Lars
Priority date: 1996-06-28
Filing date: 1997-06-25
Publication date: 1998-01-08
Also published as: SE9602560D0; SE9602560L; SE509600C2

Abstract

In a method for gluing at least two elements (1) to each other glue is applied on surfaces (2) of the elements and these are pressed and kept in a fixed mutual position against each other during the curing of the glue. A piece (5) in the form of at least one turn of a flexible material which may be stretched while storing potential energy is applied around the elements while stretching this material, so that this material turn will try to contract and by that apply a surrounding pressure upon the elements during the curing of the glue. The invention also relates to a device for carrying out the method.

Description

A method, a device and a use in gluing

TECHNICAL FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a method for gluing at least two elements together, in which a glue is applied on surfaces of the elements, these surfaces are put against each other and a pressure is applied onto the elements so as to keep them in a fixed mutual position and pressed against each other during the curing of the glue, as well as a device according to the preamble of the appended independent device claim.

The invention and the problem according to the invention will hereinafter for illuminating but not in any way restricting the invention be discussed in the case of gluing wood elements to each other, since it is particularly well applicable to this field of use, although it may in principle be any elements whatsoever which are to be glued to each other.

When wood elements are glued to each other different types of clamps are used for keeping and pressing the glue surfaces of the wood elements against each other during a curing of the glue. These tools are comparatively expensive with respect to initial costs and operation costs, and the different wood element packages being in this way under pressure will occupy a great space and may for example not be stacked onto each other.

Another disadvantage of this type of clamp arrangements is that, when gluing several wood elements having glue-surfaces making angles with each other different from zero degrees to each other, it is difficult to keep the wood elements in a fixed and a desired position with respect to each other during the curing of the glue, and it gets almost impossible to apply a homogenous pressure on the different glue-surfaces of the wood elements without making very costly arrangements. Examples of wood units having these problems in production thereof by gluing wood elements to each other may for example be found in the Swedish patent No. 469 880 of the applicant.

Another disadvantage of the clamp arrangement already known consists in that they are all designed to take care of certain maximum and minimum dimensions of the wood element packages to be glued to each other, so that different clamp ar- rangement may be necessary for different such dimensions. The clamp arrangements already known neither manage the most different shapes of wood elements, but special components are required therefor.

An additional disadvantage of the clamp arrangements already known consists in that the pressure thereof in wet-gluing, i.e. when gluing elements having a substantial humidity, may be reduced or totally disappear when the wood is dried.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method and a device of the type defined in the introduction, which find a remedy to the disadvantage mentioned above of the methods and devices according to the prior art.

This object is according to the invention obtained by providing a method and a device according to the appended independent method and device claims. By applying said piece around the element package while stretching it in the method according the invention, so that this will tend to contract in the direction towards said rest position, a circumferential pressure will be applied substantially homoge- neously on the element package, so that a perfect alignment and centring of the elements take place in this so called, "embrace pressing". Furthermore, the pressure will be maintained as long as said piece is applied around the element package, which results in a long curing time. A piece of this type may of course also be provided to a neglectable cost with respect to the clamp arrangement already known.

According to a preferred embodiment of the invention it is a thin film that is applied as the piece forming said at least one mate- rial turn. It is pointed out that "film" here is to be given a comparatively wide meaning and also comprises such thicknesses of said piece which for instance a thicker foil or a ribbon may have, and it is by this word primarily expressed that it is a question of something having a considerably smaller thickness than width. By using such a thin film as said piece this holding and pressing member will take extremely little place, so that the element package may be stored efficiently during the curing of the glue and it will also be easy to handle the element package. It is possible that the film may be allowed to remain around the element package all the way to the use of the wood unit so formed, for example for building purposes. When the film is appropriately applied it is also possible to utilise it as protecting package in the continued handling of the unit so formed until the use thereof.

According to another preferred embodiment of the invention said material turn is applied by being wound in a web around said element package while this web is kept in a state being stretched with respect to the rest position. It will in this way be possible to handle elements having arbitrary dimensions and shapes and still always obtain a homogenous circumferential external pressure on the elements during the curing of the glue. It also gets possible to make the pressure adapted to the material, since this may easily be done by changing the tension, i.e. the stretching relationship of the piece when wound around the element package.

According to another preferred embodiment of the invention said piece is wound firstly at least one turn around the element package without tension therein and then wound at least one additional turn while stretching the material forming the turn last mentioned. It will in this way be possible to firstly obtain a securing of the elements in place in the desired position before any substantial tension is applied in said piece, since a direct winding of the piece around the elements while stretching it would lead to an application of such forces upon the elements that they are displaced with respect to each other, and it gets in such a method also comparatively difficult to get the piece to "adhere" to the elements.

According to another preferred embodiment of the invention it is a material which after stretching from a first rest position contract to a second rest position when the traction forces thereon are removed, said material being in the second rest position longer than in the first rest position, that is used for said piece, and it is then advantageous that a stretch film of plastic material is applied as said material turn. It is not at all necessary that the material in question is elastic, i.e. when traction forces therein are removed it will return to the original rest position thereof, but it is well possible to use a material having the features according to this embodiment, so that a stretch film well known within the package field may be used to keep the elements together and obtain pressure on gluing elements, such as wood elements, and this piece may by this advantageously at the same time be used as package, i.e. delivery protection, and also conventional machines for packaging with such a stretch film may be utilised, possibly with some minor modification, so as to carry out the method according to the invention.

According to a very preferred embodiment of the invention it is wood elements which are glued to each other by wet-gluing, i.e. one or several of the wood elements glued to each other have a wood with a substantial humidity when the elements are put with the glue-surfaces towards each other. By using a piece having said material features for keeping the elements and applying a glue pressure an automatic adaption of the piece to the reduced dimensions received by the element package upon drying of the wood and by that a remained homogenous pressure upon the elements is obtained, so that the method accord- ing to the invention is suited for so called wet-gluing and no complicated and cost demanding drying operations before gluing are required any longer.

By providing a device according to the appended independent device claim it will be possible by simple means to apply a piece keeping at least two elements, which are to be glued to each other, with the surfaces provided with glue of the elements under pressure towards each other while curing of said glue, while obtaining all the advantages discussed above in connec- tion with the method according to the invention.

The invention also relates to the very surprising use of a thin web of a flexible material storing potential energy when stretched as means for keeping the package of at least two elements together and press surfaces provided with glue thereof towards each other when such elements are glued together. The advantages of such a use appear very clearly from above.

Further advantages as well as preferred features of the inven- tion appear from the following description and the other dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a description of a preferred embodiment of the invention cited as an example.

In the drawings:

- Fig. 1 is a simplified perspective view illustrating a device and a method according to a preferred embodiment of the invention when gluing four wood elements to each other, and

- Fig. 2 is an enlarged view with respect to Fig. 1 illustrating how four wood elements having another cross-section than the wood elements in Fig. 1 are kept together by using the method according to the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

It is in Fig. 1 illustrated how four wood elements 1 in a device according to a preferred embodiment of the invention are provided with means 3 for holding the elements with surfaces 2 onto which glue has earlier been applied, in abutment to each other and a pressure is applied on the wood elements towards each other. This device has means for holding a supply cylinder 4 for a thin film 5, in the present case a so called stretch film of plastic. Furthermore, said means 3 are adapted to rotate through power members not shown about the wood element package 6 formed by the wood elements 1 by being arranged on a ring 8 which may be rotated with respect to a frame 7 of the device.

The device also has diverting cylinders 9, 10 for straightening and by that stretching the film 5 when it is wound about the package 6 through the rotation movement of the supply cylinder 4 about the package (in this case in the clock-wise direction as seen in Fig. 1 ). The diverting cylinder 10 is pivotably arranged with respect to the ring 8 or a member connected thereto so as to obtain an adjustment of a traction force in and stretching of the film depending upon the pressure desired in every particular case, which accordingly may be dependent upon the shape of the elements to be glued to each other or the material they are made of. The winding speed is preferably also controllable for adapting it to a desired production rhythm of a plant of which the device is a part.

The device also comprises an arrangement 11 , which here is schematically illustrated through different cylinders 12, adapted to keep the wood elements 1 in a substantially desired mutual position before the winding operation is started. The arrangement may comprise such cylinders or similar members adapted to hold one end of the wood element package each, but it may also be enough to have such cylinders for other holding mem- bers arranged in one single position. The opposite end of the wood element package may then simply rest upon the conveyor or another support member during the very gluing. Thus, the device has any type of means supporting the element package, so that the supply cylinder may rotate therearound. It would of course also be possible to arrange the cylinder fixed and hold the element package in members adapted to carry out a rotation movement around the cylinder or rotate the element package around itself so as to wind the film around the element package in this way. The function of the device is as follows. When a package of wood elements are to be glued glue is firstly applied on the glue surfaces 2 of each element and the wood elements 1 are after that brought together to substantially the mutual position they are intended to get in the final wood unit. The arrangement 11 may through the bringing of the cylinders 12 against the elements be brought to hold at least one end of the wood elements substantially in the desired position. The gluing operation is after that started by making the supply cylinder 4 to rotate around the element package firstly at least a turn or round without tension in the film, so that the film safely adheres around the element package, and the film is after that wound at least one additional turn under tension in the film and by that stretching thereof, in which a conventional stretch film preferably is brought to a length increase of 100-200% with respect to the starting length thereof. It is then possible to displace the supply cylinder 4 and the wood element package in the longitudinal direction in the very winding procedure, i.e. in the direction substantially in parallel with the axis of the cylinder, with respect to each other, so that a helical path is wound around the element package and it is then quite possible to firstly wind one ore two turns without tension in the film and then wind so many turns or rounds with tension in the film that such a stretched film will be applied on the wood element package 6 along substantially the entire length thereof. As an alternative an helically shaped path may of course also firstly be wound without tension in the film over the entire length of the element package and a corresponding winding may then take place while stretching the film. Numerous alternatives to this winding procedure with respect to turns and the like are of course conceivable within the scope of the invention.

By using a film of the type according to the invention as means for holding the wood elements 1 in place during the curing of the glue a gluing pressure evenly distributed around the wood element package will in this way be applied thanks to the tendency of the film 5 to contract in the direction towards the rest position thereof. This means in turn that, even if the wood elements 1 shrink slightly as a consequence of the escape of moisture, the film will by the contraction ensure that a homogenous gluing pressure is present around the wood element package. An advantage of using a conventional so called stretch film is that this is of a material with an ability to adhere to the elements and itself for keeping the different turns to- gether. By the so called embracing or hug pressing a directing effect upon the elements 1 is obtained and by the fact that such an influence towards straightness and the glue pressure may be maintained also when the wood elements 1 shrink the method according to the invention gets very suitable for wet gluing with a subsequent drying process.

It is illustrated in Fig. 2 how the method according to the invention is used in gluing four wood elements 1 to each other, which have another cross-section design than the wood elements ac- cording to Fig. 1. These wood elements 1 are obtained by carrying out the method described in the Swedish patent mentioned above, and it gets extremely difficult to obtain an efficient holding and a homogenous glue pressure on the glue surfaces 2 existing here and extending at an angle with respect to each other by conventional clamp arrangements. However, this is no problem for the method according to the invention, which achieve a safe holding of the wood elements in place while applying a homogenous glue pressure on the wood elements, which in this case gets particularly well directed through the tendency of the film 5 to direct forces from the outer corners of the element package 6 and inwardly towards the centre of the element package, which is substantially perpendicular to the glue surfaces of the elements. Another advantage of the method according to the invention is that an individual handling of each glue object may take place, since the film 5 is automatically adapted to each single such glue object.

By gluing wood elements to each other in this way may primarily small dimension lumber be used for obtaining improved wood products, such as the wood units illustrated in the figures, having an elongated inner hollow space, but the method according to the invention is also well applicable to other types of wood elements.

The invention is of course not in any way restricted to the preferred embodiment described above, but many possibilities to modifications thereof would be apparent to a man skilled in the art without departing from the basic idea of the invention.

The method according to the invention comprises for example also the case in which the elements are already before the very gluing method provided with a glue layer, maybe by being provided with a solid layer at the glue surfaces thereof, which is dissolved in a certain environment for subsequent curing.

It is of course also possible to glue an arbitrary number of ele- ments to each other by utilising the method according to the invention, and the method according to the invention has more exactly more particular advantages with respect to the prior art when a greater number of elements, for example six or twelve pieces, are glued to each other.

An elastic material, such as fabric of rubber or the like, may very well be used as said stretchable piece instead of a stretch film. It is also conceivable to apply a piece being present in a closed loop, such as a stocking-like member, around the ele- ment package while stretching it for keeping the element pack- age together, even if this of course makes this piece restricted to certain particular dimensions of such element packages. A plurality of such pieces could then be arranged around one and the same element package.

It is of course possible to apply glue on only some of the surfaces, and the patent claim definition with respect to the application of glue also comprises the case in which glue is applied on a glue-surface of one element and this is then put against a glue surface lacking glue of another element.

Claims

1. A method for gluing at least two elements (1 ) together, in which a glue is applied on surfaces (2) of the elements, these surfaces are put against each other and a pressure is applied onto the elements so as to keep them in a fixed mutual position and pressed against each other during the curing of the glue, characterized in that said pressure and the keeping together is obtained by, after applying the glue-surfaces of the elements against each other, applying a piece (5) in the form of at least one turn of a flexible material that may be stretched while storing potential energy around an element package (6) formed by putting the elements against each other while stretching this material out in the running direction of said turn with respect to a rest position, so that the material turn will bear externally against the elements while striving to contract itself in the direction towards the rest position and the material turn by that applies a circumferential pressure upon the elements and keep them together as a package during the curing of the glue.

2. A method according to claim 1 , characterized in that it is a thin film (5) which is applied as said piece forming at least one material turn.

3. A method according to claim 1 or 2, characterized in that said material turn is applied by being wound in a web around said element package (6) while keeping this web in a stretched state in which it is expanded with respect to the rest position.

4. A method according to claim 3, characterized in that said piece (5) is firstly wound at least one turn around the element package (6) without any tension therein and it is then wound at least one additional turn while stretching the material forming the turn last mentioned.

5. A method according to any of claims 1-4, characterized in that it is a material which after stretching from a first rest position contract to a second rest position when the traction forces thereon are removed, said material being in the second rest position longer than in the first rest position, that is used for said piece (5).

6. A method according to claim 5, characterized in that it is a stretch film (5) of plastic material which is applied as said ma- terial turn.

7. A method according to claim 1 or 2, characterized in that it is a closed loop that is applied as said piece (5) around the element package (6) by stretching this closed loop as of a rest position having a shorter circumference than the element package.

8. A method according to any of claims 1 -7, characterized in that it is elongated elements (1 ) that are glued to each other.

9. A method according to any of claims 1-8, characterized in that it is wood elements (1 ) that are glued to each other.

10. A method according to claim 9, characterized in that it is a wet-gluing that takes place, i.e. one or more of the wood elements glued to each other has a wood with a substantial humidity when the elements are put with the glue-surfaces against each other.

11 . A device for obtaining holding of at least two elements (1 ) which shall be glued to each other, with surfaces (2) of the elements provided with glue under pressure against each other, during the curing of said glue, characterized in that it comprises means (4) for providing a web of a film (5) of a flexible material, which may be stretched from a rest position and has a tendency to contract in the direction towards this rest position when traction forces therein are removed, as well as an arrangement (3, 8) for winding the film while applying a traction force thereon prolonging it from said rest position at least one turn around said elements, so that this film will then thanks to the striving thereof in the direction towards said rest position apply a circumferential pressure upon the element package (6) so formed.

12. A device according to claim 1 1 , characterized in that said means is adapted to hold a supply cylinder of said film, and that said arrangement also comprises members (3, 8 ) for creating a relative rotation movement of the supply cylinder (4) and said element package (6) for winding the film (5) around the pack- age.

13. A device according to claim 11 or 12, characterized in that said means is adapted to receive a supply cylinder (4) of stretch film of plastic.

14. A device according to any of claims 1 1-13, characterized in that the arrangement is adapted to accomplish winding of the film firstly at least one turn around the elements (1 ) without any tension therein and then at least one additional turn while stretching the film (5) forming the turn last mentioned.

15. A device according to any of claims 11 -14, characterized in that it comprises members (1 1 ) adapted to hold the elements in a mutually substantially fixed position when the winding opera- tion is started.

16. A use of a thin web of a flexible material that may be stretched while storing potential energy as means for keeping a package (6) of at least two elements (1 ) together and press- ing surfaces (2) of these elements provided with glue against each other for gluing such elements to each other.

17. A use according to claim 16 in gluing wood elements to each other into a wood unit.