Floorboards with decorative grooves

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. provisional Application No. 60/372,082, filed in the U.S. on Apr. 15, 2002 and is a continuation-in-part of PCT International Application No. PCT/SE02/01731 filed on Sep. 20, 2002 and which designated the U.S., the entire contents of both applications being herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to floorboards provided with decorative grooves and methods for making such floorboards. The invention is particularly suited for use in mechanical locking systems integrated with the floorboard of the type described and shown, for example, in WO9426999, WO9966151, WO9966152, SE 0100100-7 and SE0100101-5 (owned by Välinge Aluminium AB), but is also usable in optional joint systems which can be used to join floors.

More specifically, the invention relates above all to floors of the type having a core and a decorative surface layer on the upper side of the core.

The present invention is particularly suitable for use in floating floors, which are formed of floorboards which are joined mechanically with a joint system integrated with the floorboard, i.e., mounted at the factory, and are made up of one or more preferably moisture-proof upper layers of decorative laminate or decorative plastic material, an intermediate core of wood-fiber-based material or plastic material and preferably a lower balancing layer on the rear side of the core. The following description of known techniques, problems of known systems and objects and features of the invention will therefore, as non-restrictive examples, be aimed above all at this field of application and in particular laminate flooring formed as rectangular floorboards intended to be mechanically joined on both long sides and short sides. However, it should be emphasized that the invention can be used in optional floorboards with optional joint systems, where the floorboards have a core and at least one surface layer and where these two parts have different decorative properties in the form of color, pattern, structure or the like. The invention can thus also be applicable to, for instance, floors with one or more surface layers of wood.

2. Background of the Invention

Laminate flooring usually consists of a core of a 6–9 mm fiberboard, a 0.2–0.8 mm thick upper decorative surface layer of laminate and a 0.1–0.6 mm thick lower balancing layer of laminate, plastic, paper, or like material. The surface layer provides appearance and durability to the floorboards. The core provides stability, and the balancing layer keeps the board plane when the relative humidity (RH) varies during the year. The floorboards are laid floating, i.e., without gluing, on an existing subfloor which does not have to be completely smooth or plane. Any irregularities are eliminated by means of base material in the form of e.g. board or foam which is placed between the floorboards and the subfloor. Traditional hard floorboards in floating flooring of this type are usually joined by means of glued tongue-and-groove joints (i.e., joints involving a tongue on one floorboard and a tongue groove on an adjoining floorboard) on the long sides and the short sides. When laying the floor, the boards are brought together horizontally, whereby a projecting tongue along the joint edge of one board is introduced into a tongue groove along the joint edge of an adjoining board. The same method is used on the long side as well as on the short side.

In addition to such traditional floors, which are joined by means of glued tongue-and-groove joints, floorboards have recently been developed which do not require the use of glue and instead are joined mechanically by means of so-called mechanical joint systems. These mechanical joint systems lock the boards horizontally and vertically. The mechanical joint systems can be formed by machining the core of the board. Alternatively, parts of the locking system can be formed of a separate material, which is integrated with the floorboard, i.e., joined with the floorboard even in connection with the manufacture thereof.

The main advantages of floating floors with mechanical joint systems are that they can easily and quickly be laid by various combinations of inward angling and snapping-in. They can also easily be taken up again and used once more at a different location. A further advantage of the mechanical joint systems is that the edge portions of the floorboards can be made of materials which need not have good gluing properties. The most common core material is a fiberboard with high density and good stability usually called HDF—High Density Fiberboard. Sometimes also MDF—Medium Density Fiberboard—is used as core. As a rule, these core materials are of high quality and often have an attractive surface which can resist penetration of moisture.

Laminate flooring and also many other floorings with a surface layer of plastic, wood, veneer, cork and the like are made by the surface layer and the balancing layer being applied to a core material. This application may take place by gluing a previously manufactured decorative layer, for instance when the fiberboard is provided with a decorative high pressure laminate which is made in a separate operation where a plurality of impregnated sheets of paper are compressed under high pressure and at a high temperature. The currently most common method when making laminate flooring, however, is direct laminating which is based on a more modern principle where both manufacture of the decorative laminate layer and the fastening to the fiberboard take place in one and the same manufacturing step. Impregnated sheets of paper are applied directly to the board and pressed together under pressure and heat without any gluing.

In addition to these two methods, a number of other methods are used to provide the core with a surface layer. A decorative pattern can be printed on the surface of the core, which is then, for example, coated with a wear layer. The core can also be provided with a surface layer of wood, veneer, decorative paper or plastic sheeting, and these materials can then be coated with a wear layer.

As a rule, the above methods result in a floor element in the form of a large board which is then sawn into, for instance, ten floor panels, which are then machined to floorboards. The above methods can in some cases result in completed floor panels and sawing is then not necessary before the machining to completed floorboards is carried out. Manufacture of individual floor panels usually takes place when the panels have a surface layer of wood or veneer.

In all cases, the above floor panels are individually machined along their edges to floorboards. The machining of the edges is carried out in advanced milling machines where the floor panel is exactly positioned between one or more chains and bands mounted, so that the floor panel can be moved at high speed and with great accuracy past a number of milling motors, which are provided with diamond cutting tools or metal cutting tools, which machine the edge of the floor panel. By using several milling motors operating at different angles, advanced joint geometries can be formed at speeds exceeding 100 m/min and with an accuracy of ±0.02 mm.

Definition of Some Terms

In the following text, the top visible surface of the installed floorboard is called “front side”, while the opposite side of the floorboard, facing the subfloor, is called “rear side”. The sheet-shaped starting material that is used is called “core”. When the core is coated with a surface layer closest to the front side and preferably also a balancing layer closest to the rear side, it forms a semimanufacture which is called a “floor element”. In the case where the “floor element” in a subsequent operation is divided into a plurality of panels, each of the panels are called a “floor panel”. When the floor panels are machined along their edges so as to obtain their final shape with the locking system, they are called “floorboards”. By “surface layer” are meant all layers applied to the core closest to the front side and covering preferably the entire front side of the floorboard. By “decorative surface layer” is meant a layer which is mainly intended to give the floor its decorative appearance. “Wear layer” relates to a layer which is mainly adapted to improve the durability of the front side. In laminate flooring, this layer includes a transparent sheet of paper with an admixture of aluminum oxide which is impregnated with melamine resin. By “reinforcement layer” is meant a layer which is mainly intended to improve the capability of the surface layer of resisting impact and pressure and, in some cases, compensating for the irregularities of the core so that these will not be visible at the surface. In high pressure laminates, this reinforcement layer usually includes brown kraft paper which is impregnated with phenol resin. By “horizontal plane” is meant a plane which extends parallel with the outer part of the surface layer. Immediately juxtaposed upper parts of two neighboring joint edges of two joined floorboards together define a “vertical plane” perpendicular to the horizontal plane.

The outer parts of the floorboard at the edge of the floorboard between the front side and the rear side are called “joint edge”. As a rule, the joint edge has several “joint surfaces” which can be vertical, horizontal, angled, rounded, beveled etc. These joint surfaces exist on different materials, for instance laminate, fiberboard, wood, plastic, metal (especially aluminum) or sealing material. By “joint edge portion” are meant the joint edge of the floorboard and part of the floorboard portions closest to the joint edge. By “decorative joint portion” is generally meant part of the top surface which is intended to resemble a visible joint between, for instance, stone or wood material.

By “joint” or “joint system” are meant coacting connecting means which connect the floorboards vertically and/or horizontally.

The above techniques can be used to manufacture laminate floorings which are highly natural copies of wooden flooring. In recent years, imitations of stones, tiles and the like have become more and more common. In this context, it is tried to manufacture decorative joint portions between stones and tiles which should be as natural as possible. They should have decoration and structure other than those of the stone material and should also be somewhat lower with respect to the horizontal plane to resemble an embedded joint between two stones or tiles. The techniques used to manufacture these decorative joint portions are expensive and do not provide a natural appearance. It should be possible to increase the market for these types of flooring significantly if decorative joint edge portions could be made in a simpler and less expensive manner and with a more natural appearance.

Conventional Techniques and Problems Thereof

When making laminate flooring with decorative and embedded joint portions, the starting material is a decorative paper with printed joint edge portions. This paper is usually impregnated with melamine resin. Uncontrolled swelling takes place in this operation. In the subsequent lamination, the decorative impregnated paper is placed on a core. A transparent wear layer is preferably placed over this decorative paper and then lamination takes place against an embossed metal sheet, in which joint portions are formed which usually have a structure different from that of the remaining part of the metal sheet and where joint portions are designed so that a depression of 0.2 mm can be provided in connection with laminating. The result is a floor element whose front side has an embedded joint pattern corresponding to the intended joint portions between the tiles.

This manufacturing method suffers from a number of problems which are above all related to difficulties in positioning the decorative paper and metal sheets in connection with laminating and the difficulty in positioning floor element and floor panels in the subsequent sawing and machining of the joint edges.

The metal sheet must be positioned with great accuracy relative to the decorative paper. Even if this is carried out with extremely great accuracy, it is not possible to eliminate the uncontrolled swelling in connection with impregnating. This swelling also causes problems in the sawing operation and machining of joint edges. The result of these swelling and positioning problems is that decoration and embossing do not agree with each other and that the decorative embedded joint portions vary between different floorboards, which results in an unnatural appearance.

To counteract these problems, different methods have been used. One method is to limit the format of the floor element so as to thus reduce the maximum deviation in connection with swelling. Special marks are made on the decorative paper which can then be read optically in connection with pressing and sawing. Then the boards are aligned as accurately as possible and individual adjustment of the sawblades can be made for each floor element.

The main disadvantage of this method is high cost, low capacity and extremely great remaining deviation between decoration, embossing and joint edge in the completed floorboard.

It is also difficult to provide a deep depression in high pressure laminate without damaging the decorative paper. Depressing of joint portions in connection with direct lamination results in fibers of the core being compressed. The compressed fibers can later, if moisture penetrates, swell more than normal and cause damage to the joint edge.

OBJECTS AND SUMMARY

An object of the present invention is to eliminate or significantly reduce one or more of the problems occurring in connection with manufacture and use of floorboards with decorative embedded joint portions. A further object of the invention is to provide a rational and cost-efficient manufacturing method for manufacturing floor elements, floor panels and floor boards.

According to one embodiment of the invention, the decorative joint portions are made in connection with the machining of the joint edges of the floor panel. Laminating and sawing can then take place without any specific requirements as to alignment, and swelling problems do not occur. The decorative and embedded joint portion can be provided by part of the decorative surface layer being removed so that the reinforcing layer of the laminate becomes visible. With suitable working machines and diamond cutting tools, it is possible to make a partial removal of the surface layer with an accuracy of 0.01 mm. The decorative layer can thus be removed partially and the reinforcing layer can be uncovered. This reinforcing layer can be given an appearance and structure that deviate from the remaining surface of the floorboard and can thus constitute an embedded decorative joint portion.

That embodiment is particularly suited for use in the joint edge portions of the floorboards, but one or more decorative embedded grooves can also be arranged at an optional location between the joint edge portions of the floorboards.

Thus the floorboard can have a surface that includes a plurality of surface portions with decorative embedded grooves between these portions, thereby forming a surface pattern with a plurality of tiles or elongate blocks or the like.

The invention is also particularly suited for use with floorboards having mechanical joint systems which allow exact positioning of the floorboards relative to each other without visible joint gaps in the decorative joint portion. Such locking systems give the decorative joint portion a natural appearance.

According to a first aspect of the invention, a system is provided for making a decorative joint edge portion between two adjoining edges of floorboards which have a core and a surface layer which is arranged on the upper side of the core and consists of at least one decorative layer and, under the decorative surface layer, a reinforcing layer is arranged. The floorboards have at their adjoining joint edge portions connectors for connecting the floorboards with each other in the vertical direction. The joint edge portions, adjoining each other, of the floorboards have a surface that includes the reinforcing layer and that is essentially parallel to the front side.

According to this aspect of the invention, the decorative visible reinforcing layer can be made in a number of different ways. The kraft paper which constitutes the reinforcing layer can be wholly or partly stained in the parts that will later constitute the decorative joint portions. The partial staining can take place with overmeasure so as not to cause positioning problems in the rest of the production process. Phenol or melamine resin that is used in impregnation can be stained. Decorative reinforcing layers can be arranged both in manufacture of floorboards with surface layers of high pressure laminate and direct laminate. Surface layers of plastic or several layers of decorative veneer layers can in the same way be machined for the purpose of providing decorative joint portions.

The machining extends preferably to a depth which is at least 0.1 times the thickness of the surface layer, from the upper side of the surface layer. The extent of the machining starting at the joint plane and inwards to the floorboard is preferably also at least 0.1 times the thickness of the floorboard. Still more preferably, the uncovered reinforcing layer extends, starting at the joint plane, a distance corresponding to at least 0.25 times the thickness of the floorboard.

According to a second aspect of the invention, the core can be used to create the decorative embedded joint edge portion, either by the core having suitable properties, or by part of or the entire core before laminating, or after machining, being machined in a convenient manner so as to provide a decorative appearance or better properties in order to counteract moisture or wear.

Mechanical joint systems as a rule require the use of relatively qualified core materials to provide a mechanical joint system with sufficient strength and a good function. Such high quality core materials, however, are not used for decoration purposes since they are concealed by the surface layer.

According to the second aspect of the invention, the decorative joint portion is formed by the surface layer being removed and the core being uncovered within areas that are to constitute the decorative joint portion.

HDF and plastic materials are particularly convenient in this context. HDF boards can, for instance, be stained using different colorants even in manufacture, and portions of the core can be reinforced by impregnating before or after laminating, using chemicals such as melamine, phenol, polyurethane and the like. With suitable machining, the visible core surface can be machined with high precision. The visible joint edges can be machined to a number of varying shapes, such as rounded, beveled at different angles and the like. Grooves can be made in the core before or after laminating, which are filled with suitable filling materials which have more suitable properties than does the core as regards, for instance, moisture and decoration. These filling materials can be placed in the core in the areas which will then constitute visible portions when the surface layer is removed or when the joint edge is given its final shape.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a–d illustrate conventional steps of manufacture of a floorboard.

FIGS. 2a–e illustrate the composition of known laminate flooring with a surface of high pressure laminate and direct laminate.

FIGS. 3a–b illustrate examples of conventional ways of manufacture of a decorative joint portion.

FIGS. 4a–b illustrate a decorative joint portion according to an embodiment of the invention.

FIGS. 5a–c show an alternative embodiment of the decorative joint portion according to an embodiment of the invention.

FIGS. 6a–c show different embodiments of the invention.

FIGS. 7a–c show an embodiment of a floorboard according to the invention.

FIG. 8 illustrates a manufacturing method for making decorative grooves.

FIG. 9 illustrates an alternative embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1a–d show in four steps manufacture of a floorboard. FIG. 1a shows the three basic components: surface layer 31, core 30 and balancing layer 32. FIG. 1b shows a floor element 3, where surface layer and balancing layer have been applied to the core. FIG. 1c shows how floor panels 2 are made by dividing the floor element. FIG. 1d shows how the floor panel 2 after machining of its edges obtains its final shape and becomes a completed floorboard 1 with a joint system 7, 7′, which in this case is mechanical, on the long sides 4a, 4b.

FIG. 2a shows manufacture of high pressure laminate. A wear layer 34 of a transparent material with great wearing strength is impregnated with melamine with aluminum oxide added. A decorative layer 35 of paper impregnated with melamine is placed under this layer 34. One or more reinforcing layers 36a, 36b of core paper impregnated with phenol are placed under the decorative layer 35 and the entire packet is placed in a press where it cures under pressure and heat to an about 0.5–0.8 mm thick surface layer 31 of high pressure laminate. FIG. 2c shows this surface layer 31 glued together with a balancing layer 32 to a core 30 to constitute a floor element 3.

FIGS. 2d and 2e illustrate direct lamination. A wear layer 34 in the form of an overlay and a decorative layer 35 of decoration paper is placed directly on a core 30, after which all three parts and, optionally, also a rear balancing layer 32 are placed in the press where they cure under heat and pressure to form a floor element 3 with a decorative surface layer 31 having a thickness of about 0.2 mm.

FIGS. 3a–c show manufacture of a conventional decorative joint portion 20, 21. FIG. 3a shows the floor element 3 before sawing. Owing to uncontrolled swelling of the decoration paper, the embossing of the surface has not occurred with sufficient precision. FIG. 3b shows the edges of the floorboard after sawing and machining. Decoration and embossing deviate significantly from the intended position.

FIGS. 4a–b show manufacture of a decorative joint portion 20, 21 according to an embodiment of the invention. FIG. 4a shows a floor panel after laminating, but before sawing. The decorative joint portion 20, 21 has been made by machining of the joint edge portions. The decorative surface layer 35 has been removed and the reinforcing layer 36a is visible and constitutes the decorative joint edge portion 20, 21 in a plane substantially parallel to the surface layer 31. The edges of the floorboard are provided with a mechanical locking system comprising a groove 9 and a tongue 10 which lock vertically and a locking groove 12 and a locking element 8 which lock horizontally. However, alternative locking mechanisms can be used.

FIGS. 5a–c show in detail the different steps of manufacture for providing a decorative joint edge portion which in this embodiment comprises a wood-fiber-based core 30 which is impregnated and stained before lamination. According to FIG. 5a, the stained impregnating material 24 is applied to the core surface 33 in the portions which in the completed floorboard will constitute the decorative joint edge portions 20, 21. A considerable part of the upper part of the intended joint edge is impregnated, so that a stained and preferably moisture-proof core portion is formed. Vacuum 46 can be used to facilitate penetration of impregnating material.

FIG. 5b shows the floor element 3 with a surface layer 31, a balancing layer 32 and the intended saw cut 45. FIG. 5c shows the edges of the floor panel 1, 1′ after sawing and machining. The surface layer 31 has been partially removed so that the stained and uncovered core is visible and constitutes a decorative joint edge portion 20, 21 in a plane substantially parallel to the surface layer 31.

FIGS. 6a–c illustrate preferred embodiments.

The machining of the decorative joint edge portion should according to FIG. 6a extend preferably to a depth P2, starting at the horizontal plane HP, which is at least 0.1 times the thickness of the surface layer 31. The extent P1 of the machining starting at the vertical plane VP and inwards to the floorboard is preferably also at least 0.1 times the thickness T of the floorboard. More preferably, the uncovered reinforcing layer or the uncovered core surface extends, FIG. 6b, starting at the vertical plane VP, a distance corresponding to at least 0.25 times the thickness T of the floorboard. FIG. 6c shows how beveled and reinforced joint portions 80, 81 can be formed by grooves being made in the core before lamination and where these grooves are then filled with a decorative filling material 80, 81 which then, after lamination, is formed by machining to decorative and preferably moisture-proof portions.

By selecting a filling material 80, 81 which in terms of color corresponds to the decoration of the surface, it is possible to provide beveled joint edges which as to appearance resemble, for instance, homogeneous wooden flooring with beveled joint edge portions. Similar grooves can also be made between the joint edge portions.

FIGS. 7a–c show how decorative joint portions 20a, 20b according to the invention can be manufactured and positioned optionally on the surface of the floorboard between the decorative joint edge portions 20. Preferably, such decorative joint portions 20a and 20b should have a width which is 2 times the width of the joint edge portion 20, so that all decorative joint portions will have the same appearance when the floorboards are joined.

FIG. 8 shows how the decorative joint portions according to FIG. 7 can be manufactured. The outer joint edge portions 20 of the floorboard are manufactured by the floorboard being passed through milling machines fixed between chains 50, 51 and bands 60, 61, as a rule first through a first machine that machines the long sides, and then through a second machine that machines the short sides. The tools with their respective milling motors 70, 72 are located outside the chains and machine the joint edges. As a rule, use is made of up to five tools on each side, which at different angles machine the joint edges. To manufacture a floorboard efficiently according to the invention with decorative grooves between the joint edges, it must also be possible to perform machining of the surface of the floorboard also between the chains 50, 51. According to an embodiment of the invention, this is most conveniently made by one or more milling motors being provided with extended tool shafts so that the milling motors can be positioned outside the chain while at the same time the tool 71 performs machining between the chains. This is advantageous in particular when manufacture is to be performed of decorative grooves which are close to the joint edges. For efficient manufacture of a floorboard with a mechanical locking system and with decorative joint portions at the joint edges and/or between the joint edges, it is preferable for the number of machining motors and tools on each side to be increased to six. Manufacture can be still more efficient if the number of tools is increased to between six and eight on each side.

Manufacture of floorboards, especially laminate flooring, according to these preferred methods is not known and does not exist today. The decorative grooves can also be made in a separate operation, but this causes a higher cost and considerably greater variation than in the case where all parallel decorative grooves are made in the same machine in one operation. The accuracy of the grooves in depth and side can with the preferred manufacturing method according to FIG. 8 be made with a tolerance of a few hundredths of a millimeter.

FIG. 9 illustrates another embodiment of the present invention, wherein the long side 4a has in this embodiments a decorative groove 133 which only appears in one joint edge. The advantage is that the joint edge will be less visible than in the case when both joint edges of the boards 1, 1′ have decorative grooves. Moreover, manufacture will be simplified. If the locking system on the short side, for instance, has no tongue 10, the floorboards are locked only in the horizontal direction.

The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims be embraced thereby.