Note: Descriptions are shown in the official language in which they were submitted.
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BUILDING PANEL WITH COMPRESSED EDGES
Technical field
The present invention generally relates to building
panels, especially floorboards, which have a wood fibre
based core, a surface layer and compressed curved edge
portions. More particularly, the present invention
relates to interlocked building panels with compressed
edge portions located below the panel surface. The
invention relates to panels with such edge portions and
to a method to produce such panels.
Field of Application of the Invention
The present invention is particularly suitable for use
in floating floors, which are formed of floorboards
comprising a wood fibre based core with a surface layer
and which are preferably joined mechanically with a
locking system integrated with the floorboard. A
floorboard with a mechanical locking system has a rather
advanced edge profile and curved edge portion are more
difficult produce than traditional furniture components.
The following description of prior-art technique,
problems of known systems and objects and features of the
invention will therefore, as a non-restrictive example,
be aimed above all at this field and in particular to
laminate flooring with mechanical locking systems.
However, it should be emphasized that the invention can
be used in optional floorboards with optional locking
systems, where the floorboards have a core and at least
one surface layer and where these two parts are possible
to be formed with a pressure force applied to the surface
layer. The invention can thus also be applicable to, for
instance, floors with one or more surface layers of wood
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applied on a wood fibre core. The present invention
could also be used in building panels i.e. wall panels,
ceilings and floor strips such as dilatation profiles,
transition profiles or finishing profiles.
Definition of Some Terms
In the following text, the visible surface of the
installed floorboard is called "front side", while the
opposite side is called "rear side". "Horizontal plane"
relates to a plane, which extends along the outer flat
parts of the surface layer at the front side. "Vertical
plane" relates to a plane, which is perpendicular to the
horizontal plane and at an outer edge of the surface
layer. By "up" is meant towards front side, by "down"
towards rear side, by "vertical" parallel with the
vertical plane and by "horizontal" parallel with the
horizontal plane.
By "edge portion" is meant a part of the edge, which is
below the horizontal plane. By "floor surface" is meant
the outer flat parts of the surface layer along the
horizontal plane. By "edge surface" is meant the surface
of the edge portion. By "locking system" is meant
cooperating connecting means, which interconnect the
floorboards vertically and/or horizontally. By
"mechanical locking system" is meant that joining can
take place without glue.
Background of the Invention, Prior-Art Technique and
Problems thereof
Laminate floors and other similar floorboards are made
up of one or more upper layers of decorative laminate,
decorative plastic material or wood veneer, an
intermediate core of wood fibre based material or plastic
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material and preferably a lower balancing layer on the
rear side of the core.
Laminate flooring usually consists of a core of a
6-9 mm fibreboard, 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 mate-
rial. Thicker laminate flooring with a thickness of 12-
16 mm or more could be produced. Such floors will have
favourable sound properties. Extremely thin floorings
with thicknesses of 3-6 mm could also be produced. Such
thin floorings could be used in installations with floor
heating and the thin floor panel will transfer heat to
the surface more efficiently than traditional floor
panels. 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. Traditional hard floorboards in
floating flooring of this type are usually joined by
means of glued tongue-and-groove joints.
In addition to such traditional floors, floorboards
have been developed which do not require the use of glue
and instead are joined mechanically by means of so-called
mechanical locking systems. These systems comprise
locking means, which lock the boards horizontally and
vertically. The mechanical locking systems can be formed
by machining of the core. 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 in connection with the manufacture
thereof.
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The most common core material is fibreboard with high
density and good stability, usually called HDF - High
Density Fibreboard. Sometimes also MDF - Medium Density
Fibreboard - is used as core. MDF and HDF contain ground
Laminate flooring and also many other floorings with a
surface layer of plastic, wood, veneer, cork and the like
are produced in several steps. As shown in figure la -
decorative layer and balancing layer to a fibreboard.
Such a production process is used when a floor panel has
20 The currently most common method when making laminate
flooring, however, is the direct pressure laminate (DPL)
method which is based on a more modern principle where
both manufacture of the decorative laminate layer and the
fastening to the fibreboard take place in one and the
30 Figures la - id shows how laminate flooring is produced
according to known technology. As a rule, the above
methods result in a floor element (3 in fig lb) in the
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form of a large laminated board, which is then sawn into
several individual floor panels (2 in fig 1c), which are
then machined to floorboards (1 in fig 1d). The floor
panels are individually machined along their edges to
floorboards with mechanical locking systems on the edges.
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 belts or
similar, 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 profiles can be formed at
speeds exceeding 100 m/min and with an accuracy of
0.02 mm.
The upper edges of the floorboards are in most cases
very sharp and perpendicular to the floor surface and in
the same plane as the floor surface.
Recently laminate floors have been developed with
decorative grooves or bevels at the edges, which looks
like a real gap or a bevel between solid wood floor such
as planks or parquet strips.
It is known that such edges cold be made in several
different ways.
In recent years, laminate floors, which are imitations
of stones, tiles and the like, have become more and more
common. It is known that the method that is used to
manufacture decorative edge portions of such floors could
also be used to produce edge portions, which look like a
gap in solid wood floors. This is shown in figure 2a and
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2b. The starting material is a decorative paper with
printed edge portions, which is impregnated with melamine
resin. Uncontrolled swelling takes place in this
operation. In the subsequent lamination, the decorative
impregnated paper is placed on a core and lamination
takes place against an embossed metal sheet, which forms
a depression (20) in those parts of the floor element (3)
where edge portions are to be formed. This is shown in
figure 2a. The result is a floor element (1,1') whose
front side has an embedded or embossed edge pattern
corresponding to the intended edge portions between
floorboards, as shown in figure 2b.
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 con-
nection with laminating and the difficulty in positioning
floor element and floor panels in the subsequent sawing
and machining of the edges. The result is a floor panel
with edge portions, which show considerable and undesired
variations in structure and design as shown in figure 2b.
Another problem is that this method is only suitable for
embossed textures which are less than about 0,2 mm deep
and which cannot be made deeper than the thickness of the
surface layer. Further disadvantages are that although
the edge is below the floor surface, it is sharp and
parallel with the surface. The inventor has analyzed and
evaluated the possibilities to use this traditional
technology and to produce compressed edge portions in DPL
floor panels with a shape of for example a bevel or a
convex curved edge. Some of the main conclusions are
shown in figure 2e and described below.
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A decorative paper with only a wood design could be
used and this will give the advantage that the problem of
positioning the press plate and a printed decorative edge
portion could be avoided. This method has however several
disadvantages. It is very difficult to form an edge with
an edge depth ED of more than about 0,2 mm, which is in
the same magnitude as the surface thickness ST. The
maximum angle AN, which could be accomplished is less
than 10 degrees. The production would be inefficient
since the press cycle time and the pressing pressure must
be increased. Higher angles and deeper embossing will
considerably increase the risks that the paper breaks
during production. It would also be very difficult to
position the laminated floor element with the depressions
in the subsequent sawing and milling operation. There
would be considerable undesirable tolerances in the edge
widths EW1, EW2 in the magnitude of 0,3 - 0,5mm. The
adjacent edge and depressions 20,20' intended to be in
contact with each other would not meet at the same height
position. Furthermore the laminate surface layer will be
compressed, especially the transparent overlay wear layer
33, which is located over the printed decorative paper
34. All these problems will increase if the traditional
width of the floorboard of 200 mm is decreased to for
example 150 mm or 120mm or below 100 mm, since the number
of depression will increase. In most application this
would require that the pressing pressure must be
increased from 300N/cm2 to 600N/cm2 or even 800 N/cm2.
Considerable investments in new and more expensive
pressing equipment and embossed metal sheets would be
required, especially if floorboards of different widths
or lengths are to be produced.
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Figure 2c and 2d show another method. Decorative edge
portions could be made in connection with the machining
of the edges of the floor panel 1, 1'. Laminating and
sawing of the floor element (3) can then take place
without any specific requirements as to alignment, and
swelling problems do not occur. The decorative and
embedded edge portion can be provided by part of the
decorative surface layer being removed so that the
reinforcing layer of the laminate becomes visible (figure
2d). Alternatively, the core (30) itself can be used to
create the decorative embedded edge portion. This is
shown in figure 3a. The surface layer has been removed
and the core (30) is uncovered within areas that are to
constitute the decorative edge portion (20). A decorative
grove could be made on only one edge as shown in figure
3a. The main disadvantage is that it is impossible to
create a design and structure, which is the same as the
surface layer. Therefore it is not possible to form an
edge portion that looks like a bevel in a solid wood
surface layer.
The most common method is shown in figure 3b. A part of
the edge portion of a floorboard (1, 1') has been formed
as a bevel 20 and this bevel is then in a separate
operation covered with a separate material such as a
tape, a plastic strip or it could be coloured, printed
etc. Separate materials are complicated and costly to
apply and it is not possible to make an_edge portion with
the same design and structure as the floor surface. Such
edge portion has considerable lower abrasion resistance
and inferior moisture properties than the floor surface.
The production method is rather slow and several
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application unites are needed to meet the speed of a
modern production line for laminate floorings.
Another method is shown in figure 3c. The edge portion
(20) is formed in a separate material, which has been
inserted or extruded into a groove. This method has the
same disadvantages as the method described above.
Fig 3d show that a rounded edge portion (20) could be
produced with the well-known post forming method used for
components. A post forming laminate surface
(31) of HPL, which is so flexible that it can be formed
after the production of the laminated sheet, could be
glued to an already machined floorboard (1). In a second
production step the edge could be heated and the laminate
could be bent and glued around the edge portion. This
method would be very complicated and costly, since
individual floor panels have to be laminated, and is not
used in laminate floorings. In theory it is of course
possible to use the DPL technology and to make a direct
pressing of a decorative paper and overlay on a floor
panel with curved edge portions. Even in this case
individual floor panels have to be handled separately in
the press and'this will result in a very inefficient
production
The principles of the present invention are directed to
edge portions in building panels, which overcome one or
more of the limitations and disadvantages of the prior
art.
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Summary of the invention
Some embodiments of this invention may provide
building panels, especially floorboards, with curved edge
portions made in one piece with t'le surface layer, which
could be produced more efficient.y than present products
on the market.
Some embodiments of this invention may provide
such panels with edge portions, which have improved
design and abrasion properties.
According to a first
principle of the invention, a floorboard is provided,
with locking system, a wood fibre based core and a
surface layer arranged on the upper side of the core. The
outer flat parts of the surface layer constituting a
floor surface and a horizontal plane. A plane,
perpendicular to the horizontal plane and at the edge of
the surface layer, constitutes a vertical plane. The
floorboard has an edge portion with an edge surface,
which is located under the horizontal plane. The edge
surface at the vertical plane is at a distance from the
horizontal plane which constitutes an edge depth and
which exceeds the thickness of the surface layer.
The floor surface and the edge surface are made in one
piece of the same material. A part of the core in the
edge portion under the edge surface adjacent to the
vertical plane and at a vertical distance from the edge
surface has a higher density than a part of the core
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under the floor surface adjacent to the edge portion and
at the same vertical distance from the floor surface.
The curved edge portion could be formed on only one
edge, on two opposite edges or on two pairs of opposite
edges. Alternative the edge portion could be formed in
panels comprising more than 4 edges.
The most efficient production is obtained if the panels
have curved edges according to the first principle of the
invention on two opposite edges, preferably the long
edges, if the floorboards are rectangular. The short
edges could have traditional straight edges. The short
edges could also have at least one edge portion which is
located below the surface and which is formed by any
other method for example as shown and described in
connection to the figures 2a - 2e, 3a - 3d, 6a -6b or 8.
Floorboards with a wood surface have often bevels or
curved edges, which are different in shape and surface
structure on the long edges compared to the short edges.
The main reason is that the fibre orientation on the long
and short edges is different. Different production
methods are also used and this gives different
appearance. The inventor has discovered that laminate
floorboards could be produced more efficiently and with
designs features, which are very similar to wood if the
edge surface on long edges is different to the edge
surface on one both short edges.
According to a second principle of the invention a
rectangular floorboard is provided comprising pairs of
opposite long and short edges, a mechanical locking
system on at least one pair of edges, a wood fibre based
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core and a laminate surface layer arranged on the upper
side of the core. The outer flat parts of the surface
layer constituting a floor surface and a horizontal
plane. The floorboard has on the long edges and on at
least on one of the short edges edge portions with edge
surfaces, which are located under the horizontal plane.
An edge surface on the long edge comprises a different
material than an edge surface on the short edge.
According to one preferable embodiment of this second
principle, the floorboard has one pair of long edges with
an edge portion according to the first principle. On one
short edge the floorboard has an edge portion where the
laminate surface layer has been removed and the wood
fibre based core, preferable HDF, is painted or
impregnated with for example an oil based chemical.
According to a third principle of the invention, a
method is provided to make a floorboard, with a locking
system, a wood fibre based core and a surface layer
arranged on the upper side of the core. The outer flat
parts of the surface layer constituting a floor surface
and a horizontal plane. The floorboard has an edge
portion with an edge surface, which is located under the
horizontal plane. The method comprises the steps of:
= Applying the surface layer on the core to form a
floor element.
= Cutting the floor element into floor panels.
= Applying a pressure on the surface of an edge
portion of the floor panel such that the core under
the surface layer is compressed and the surface
layer is permanently bended towards the rear side.
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According to another aspect of the second principle
of the invention, a method is provided to make a building
panel, with a wood fibre based core and a surface layer
arranged on the upper side of the core. The outer flat parts
of the surface layer constituting a panel surface and a
horizontal plane. The panel has an edge portion with an edge
surface, which is located under the horizontal plane. The
method comprises the steps of:
= Applying the surface layer on the core to form a
building element.
= Cutting the building element into building panels.
= Applying a pressure on the surface of an edge
portion of the building panel such that the core under the
surface layer is compressed and the surface layer is
permanently bended towards the rear side of the core.
According to another aspect of the invention, there
is provided a method to make a floorboard, with a mechanical
locking system, a wood fibre based core and a surface layer
arranged on the upper side of the core, the outer flat parts of
the surface layer constituting a floor surface and a horizontal
plane, the floorboard has an edge portion with an edge surface
which is located under the horizontal plane the method
comprising: applying the surface layer on the core to form a
floor element, cutting the floor element into floor panels,
applying a pressure on the surface of the edge portion of the
floor panel and compressing the core under the surface layer
and bending the surface layer permanently towards the rear
side, forming an edge groove at the edge of the floor panel
before applying the pressure, and forming the mechanical
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locking system at the edge of the floor panel after applying
the pressure.
Some embodiments of the invention may be very
suitable to produce curved or bevelled edge portions in panels
with different widths, especially narrow panels, and also in
very thick (12-16 mm) and thin (3-5 mm) laminate panels as
described in the introduction. Such thin and thick panels are
=
not produced today. The production equipment and method
according to the invention may be much easier to adjust to
panels of different sizes and thickness than the traditional
pressing and post forming technology.
Brief Description of the Drawings
Figs la-d illustrate in different steps manufacture
of a floorboard according to known technology.
13a
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Figs 2a-e illustrate production methods to form edge
portions according to known technology.
Figs 3a-d illustrate examples of different ways of
manufacture of edge portions according to prior art.
Figs 4a-b illustrate press forming of an edge portion
according to the invention.
Figs 5a-c illustrate different properties of a convex
curved edge portion according the invention.
Figs 6a-b illustrate alternative methods to form
embodiments of the invention.
Fig. 7 illustrates a dilatation profile according to
the invention.
Fig. 8 illustrates an edge portion with a curved edge
surface.
Fig. 9 illustrates a floorboard with edge surfaces on
long and short edges comprising different materials.
Description of Preferred Embodiments
Figs 4a-4c show in four steps manufacture of floor-
boards according to one embodiment of the invention. Fig.
4a shows two opposite edges of two essentially similar
floor panels 2, 2'that are intended to be joined together
with a mechanical locking system. The floorboards have a
surface layer 31 of for example HPL, DPL or wood veneer,
a core 30 of HDF and balancing layer 32. As show in fig.
4b an edge groove 16, 16' is formed at the upper side of
the edge and a part of the surface layer 31 is removed.
This could be done in a separate operation or in
connection with the sawing of the floor element 3 into
floor panels 2. If the surface layer 31 is laminate, at
least a part of the edge groove 16,16' and the surface
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layer 31 adjacent to the edge groove 16,16' should
preferably be heated with a suitable heating device H,
such as for example heating nozzles which blow an even
current of hot air, with infra red radiation, micro
waves, high frequency, contact heating, laser or similar
known technology. The temperature should exceed 100
degree C. A preferable temperature is about 150 - 200
degree C. In many applications a temperature of about 170
degree C gives the best result. Normal laminate quality
could be used as a surface layer 31 and no special post
forming quality is needed. A modification of the
thermosetting resins similar to the modification, which
are used in post forming laminates, could however
increase the production efficiency. If the surface layer
31 is a wood veneer, heating is preferably not required.
The floor panel should preferably have a reference
surface 17, 17'that could be used to position the floor
panel correctly when edge portions and locking systems
are formed. As shown in figure 4c the edge portions 20,
20' are then compressed with a compression tool TO which
preferably is heated to similar temperatures as described
above. The compression tool TO could be a wheel and/or a
pressure shoe or similar with a profile which preferably
corresponds to the desired edge profile. Several tools
could be used to form the edge portion in several steps
on for example one long edge, both long edges or on long
and thereafter on short edges. Of course short edges
could be formed before long edges and several floorboards
could be formed in the same equipment. Wheels could have
different structures and this will make it possible to
form an embossed edge portion. Such an edge portion could
also have a random or synchronized structure. The
pressing of the edges could be a continuous operation
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were in the floorboard for example is displaced in
relation to a fixed tool. Of course the board could be in
a fixed position and a tool could be displaced in
relation to the board. Other alternatives are also
possible. The edge could also be formed with a
traditionally pressing operation. Such a method is
especially easeful for the short edges and corner
sections could be formed with great accuracy. During the
compression, the fibres in the core will be permanently
compressed, the fibre orientations will in most cases
change and the density in the edge portion 20 will
increase. If the surface layer is laminate, generally in
most applications no major compression of the surface
layer will occur. A change in the fibre orientation might
be difficult to detect in some core materials. Increased
density could however be measured with grate accuracy.
The edge portion 20 will be much stronger than
traditional bevelled edges in laminate flooring. The
abrasion resistance will be similar as in the floor
surface and the visible edge portion will have the same
design and structure as the floor surface. The upper
parts of the core 30 under the surface layer 31, which in
a DPL flooring is impregnated with melamine and in a HPL
flooring with glue, supports the laminate surface layer
31 during the bending and increases the flexibility of
the laminate layer. The advantage is that ordinary
qualities of thermosetting decorative laminates, which
are rather brittle, could be used. HDF is particularly
suitable for this kind of press forming with permanent
compression according to the invention since the fibre
structure and the binders, which are used in HDF, are
ideal for this application.
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As shown in figure 4d a mechanical locking system with
a tongue 10 and grove 9 for vertical locking and a strip
6 with a locking element 8 and a locking grove 12 for
horizontal locking could easily be formed and positioned
with high precision in relation to the compressed edge
portions 20,20'. In this embodiment the press forming of
the edge portions 20, 20' is made on the floor panel 2,
which thereafter is machined to a floorboard 1. The
advantage is that the forming of the mechanical locking
system can be made with great accuracy and the press
forming will not change the dimensions of the profile,
which in this embodiment is mainly the tongue 10 and the
groove 9. Test production show that tolerances of 0,1 mm
or lower could be obtained and this is considerably lower
than what could be accomplished with the known technology
Of course it is possible to form the edge portions 20,
20' on the floorboard after the machining of the edges,
but this is more complicated and the compression
possibilities are more limited. In most cases further
machining is then required to form the upper outer edge.
Figure 5a shows a cross section of a panel edge
according to the invention. In this preferred embodiment
the floor panel 1 has a surface layer 31 of DPL with a
surface thickness ST and an outer edge 51. The upper flat
part of the surface layer 31 constitutes a horizontal
plane HP and a floor surface 33. A plane perpendicular to
the horizontal plane and at the outer edge 51 of the
surface layer 31 constitutes a vertical plane VP. The
convex curved edge portion 20, which is located under the
horizontal plane HP and which extends to the vertical
plane VP has an edge width EW, measured parallel with the
horizontal plane HP and an edge surface 50. An edge
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portion 20 is considered to be convex curved if at least
some parts are convex and the remaining parts are
straight as shown in figure 5a. The edge portion 20 has
an edge depth ED measured vertically from the horizontal
plane HP, which is equal to the distance SD from the
horizontal plane HP to the outer edge 51 at the vertical
plane VP. As shown I figure 5a the fibres in the edge
portion 20 have been compressed and the fibre orientation
have been changed such that the fibres are curved in the
same direction as the edge surface 50 of the edge portion
20. The tangent line TL1, TL2 of the curved edge portion
has a larger angle AN2 to the horizontal plane at the
vertical plane VP than at a distance from the vertical
plane, for example at a distance which is 0,5*EW. The
15 invention makes it possible to form edge portions with
tangent lines TL having angles exceeding 10 degrees. It
is even possible to produce edge portions with angles AN
exceeding for example 15, 20,30 or even 45 degrees.
Several relationships are favourable in order to
20 produce an edge portion (20) according to the invention.
= Edge depth ED should preferably be larger than
the surface layer thickness ST. In the most
preferable embodiment edge depth ED should be larger
than 2 or even 3 times the surface thickness ST. The
method allows forming of edge portions 20 with edge
depths ED exceeding 10 times the surface thickness
ST.
= The edge width EW should preferably be larger
than the edge depth ED. In the most preferable
embodiment edge width EW should be larger than 2
times the edge depth ED
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= The edge depth ED should preferably be larger
than 0,1 times the floorboard thickness T.
= The thickness ST of the surface layer 31 should
be 0,1 - 0,01 times the floor thickness T.
= The tangent line TL at the edge portion which is
located at the vertical plane VP should have an
angle AN to the horizontal plane exceeding 10
degrees
These relationships could be used independently or in
combination on one edge or on for example long and short
edges. The long edges could for example be formed with a
more curved edge portions than the short edges. A
preferable combination is that the edge depth ED is
larger than the surface layer thickness ST and that the
tangent line TL of a part of the edge portion 20 has an
angle exceeding 10 degrees.
Figure 5b shows the densities D profile in a part (A-A)
of a floorboard 1, which has not been compressed and
figure 5c shows the density profile D in a compressed
edge portion (B-B) of the same floorboard. Density
profiles could be measured extremely accurately with a
gamma beam. The distance between measuring points could
be as small as 0,04 mm. In this example the surface layer
31 of laminate, which is about 0,2 mm thick, has a
density of about 1300 kg/m3. Below the surface layer 31
there is a core portion 52 which in connection with the
direct pressure lamination has been impregnated with
melamine and where the density varies between about 1209
- 1000 kg/m3. Under this core portion 52 there is another
portion 53 where the density is slightly higher than in
the middle parts of the core 30. The average density is
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shown by the line AD. It should be emphasized that
compression in wood fibre based board material always
gives an increased density.
An alternative method is shown in figure 4d. Two test
samples Si and S2 with the same thickness ST are taken
from the edge and the weight is measured. If the weight
per mm is essentially the same, it is a strong indication
that no materials has been removed and that the edges
have been compressed. The sample thickness could be for
example 2,44 mm and the sample length 20 mm along the
joint. Si could have a sample width SW of 3,46 mm and S2
of 3,04 mm. The weight of Si is 0,167 gram and of S2
0,143 gram. Si has a weight per mm of 0,167/3,46 = 0,048
gram and S2 0,143/3,04 = 0,47 gram. The reason for this
small difference is mainly the fact that Si contains
slightly more surface layer with higher density than HDF,
due to the curved shape. Similar tests in a panel where
the surface layer has been laminated on a machined curved
edge show that 51 has a weight of 0,062 gr/mm and S2
0,071 g/mm. This is a strong indication that core
material has been removed before pressing and not
compressed according to the principles of the invention
Figure 5c shows the density profile in a compressed
part B-B of the edge portion 20. A part of the core 30 in
the edge portion adjacent to the vertical plane VP and at
a vertical distance SD from the surface layer 31, has a
higher density D than a part of the core which is under
the floor surface adjacent to the edge portion 20 and at
the same vertical distance SD from the surface layer 31.
This is as explained above contrary to traditional post
forming where the edge portion is machined and the
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surface layer is glued to the part of the core, which
have the same or lower density.
Figure 6a shows an alternative method to form an edge
portion 20 in a DPL flooring. A floorboard 1 is produced
with an edge groove 19 under the surface layer 31. The
upper part of the edge grove 19 consist of the surface
layer 31 and a part of the core 30. This upper part of
the edge grove 19 is folded against the lower part of the
edge grove 19 and both parts are pressed and glued
together. Figure 6b shows that this method could be used
to form an edge portion of a floor panel, which is then
machined to a floorboard. Both these methods are more
complicated than the press forming since glue and
separate machining is required. This method could be
partly combined with the press forming and the core could
be compressed in connection with the gluing.
Figure 7 shows a dilatation profile 4 with press formed
edge portions 20, 20', according to the invention.
Figure 8 shows a floorboard with edge portions 20 at
opposite edges which are curved and where the outer
adjacent parts of the edge surfaces 50 are essential
parallel with the horizontal plane HP.
Figure 9 shows a floorboard where the edge surface of
the edge portions 20 on the long edges 4a, 4b comprise
different material than the edge surface of the edge
portion 20' of one of the short edges 5a. The long edges
could preferably be formed according to the method shown
in figure 5a. In this embodiment one of the short edges
5a has an edge portion 20' in the form of a decorative
grove essentially parallel with the horizontal plane HP
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as shown in figure 3a. The edge surface on the long edges
is a laminate made of a melamine-impregnated paper and on
one short edge the edge surface is HDF fibres, which
could be painted. Several combinations such as
laminate/tape, laminate/printing, tape/printing,
laminate/impregnation laminate/tape etc are possible to
use in order to improve appearance and production cost.
Of course long and short edges could be formed according
to the first aspect of the invention:
The invention is especially suitable to produce
laminate floorings that look like solid wood floor strips
with a width of about 5-10 cm and where compressed edge
portions are only formed on the long sides. Such
floorboards could also easily be made in random lengths
since long press formed floor panels could be produced
which are thereafter machined and cut to floorboards in
different lengths. Of course a machined edge portion on
one short edge could also be formed. The visible wood
fibres could be painted. The invention is also very
suitable for laminated panels with a width of 10-12 cm or
12-15 cm where traditional methods are difficult to use.
A floor which consist of such narrow floorboards will
have many curved edge portions 20 and only very cost
efficient production methods such as press forming could
be used in order to obtain production costs which are
competitive and lower than similar solid wood floors.
Press forming is very efficient and can easily meet the
speed of modern profiling lines.
The method to compress the core with a surface layer of
a laminate floor element, floor panel or floorboard or a
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similar building element panel according to the invention
could be used to form embossed portions on other parts
than the edges.
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