Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MECHANICAL LOCKING OF FLOOR PANELS WITH VERTICAL FOLDING
Area of Invention
The invention generally relates to the field of floor
panels with mechanical locking systems with a flexible and
displaceable tongue allowing easy installation. The
invention provides new improved locking systems and
installation methods.
Background of the Invention
In particular, yet not restrictive manner, the invention
concerns a mechanical locking system for rectangular floor
panels with long and short edges. It should be emphasized
that long and short edges are only used to simplify the
description. The panels could also be square. However, the
invention is as well applicable to building panels in
general. More particularly the invention relates to the
type of mechanically locking systems which allow that all
four edges of a panel could be locked to other panels by a
single angling action preferably comprising a flexible or
partly flexible tongue and/or displaceable tongue and/or a
flexible locking strip in order to facilitate the
installation of building panels.
A floor panel of this type is presented in W02006/043893,
which discloses a floor panel with a locking system
comprising a locking element cooperating with a locking
groove, for horizontal locking, and a flexible tongue
cooperating with a tongue groove, for locking in a
vertical direction. The flexible tongue bends in the
horizontal plane during connection of the floor panels and
makes it possible to install the panels by vertical
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folding or solely by vertical movement. By "vertical
folding" is meant a connection of three panels where a
first and second panel are in a connected state and where
a single angling action of a new panel referred to as the
"folding panel", connects two perpendicular edges of the
new panel, at the same time, to the first and second
panel. Such a connection takes place for example when a
long edge of the first panel in a first row is already
connected to a long edge of a second panel in a second
row. The new folding panel is then connected by angling to
the long edge of the first panel in the first row. This
specific type of angling action, which also connects the
short edge of the new folding panel and second panel, is
referred to as "vertical folding". The short edges are
gradually folded together and locked from one edge part to
the other as scissors when the panel is angled down to the
subfloor. It is also possible to connect two panels by
lowering a whole panel solely by vertical movement against
another panel. This specific type of locking is referred
to as "vertical locking" A first row in a flooring system,
which is designed to be locked with vertical folding, is
often connected with a vertical locking where one short
edge is pressed down vertically towards an another short
edge. The other rows are connected with vertical folding.
It is also possible to install a compleate floor by
connecting a row with vertical locking. The whole row is
than connected to a previous installed row by angling.
Similar floor panels are further described in
W02003/016654, which discloses locking system comprising a
tongue with a flexible tab. The tongue is extending and
bending essentially in a vertical direction and the tip of
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the tab cooperates with a tongue groove for vertical
locking.
Vertical locking and vertical folding of this type
creates a separation pressure at the short edges when the
flexible tongue or flexible parts of the tongue are
displaced horizontally during the angling of the long
edges. The inventor has analysed several types of floor
panels and discovered that there is a considerable risk
that the short edges could be pushed away from each other
during installation and that a gap could occur between the
edge portions of the short edges. Such a gap could prevent
further installation and the floor panels will not be
possible to connect. It could also cause serious damage to
the locking system at the short edges. Pushing the
floorboards sideways towards the short edges during
installation could prevent the gap. Such an installation
method is however complicated and difficult to use since
three actions have to be combined and used simultaneously
in connection with angling down of the long edges as
described below.
a) The edges of a new floor panel has to be brought in
contact with a first floor panel laying on the floor and
the long edge of the new panel has to be pressed forward
in angled position towards the first panel
b) The new panel has to be displaced sideways, in the
pressed and angled up position, and pressed sideways
against a short edge of a second panel laying on the floor
in order to counteract the counter pressure of the tongue
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C) The new panel must finally be angled down to the floor
and the forward and sideways pressure must be maintained
during the angling action.
The inventor has discovered that separation and
installation problems often occur when the panels have a
small thickness and small compact locking systems on the
long edges or when the panel core comprise a material with
smooth surfaces such as high density fibreboard (HDF).
Such problems could also occur when the panels are short
or in connection with the installation of the first or
last panel in each row since such installation is
generally made with panels which are cut to a smaller
length in order to adapt the floor to the wall position.
Separation problems are of course extremely difficult to
handle in any type of panels using locking systems with a
strong flexible tongue that creates a substantial
horizontal separation pressure during the vertical
folding. Such strong tongues are very important in many
applications where a high quality vertical connection is
required and panels with such flexible tongues are very
difficult to install with the known installation methods.
The invention aims to solve separation problems in
flooring which is intended to be installed with vertical
folding or vertical locking.
Definition of Some Terms
In the following text, the visible surface of the
installed floor panel is called "front face", while the
opposite side of the floor panel, facing the sub floor, is
called "rear face". The edge between the front and rear
face is called "joint edge". By "horizontal plane" is
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meant a plane, which extends parallel to the outer part of
the surface layer. Immediately juxtaposed upper parts of
two adjacent joint edges of two joined floor panels
together define a "vertical plane" perpendicular to the
5 horizontal plane.
By "joint" or "locking system" are meant co acting
connecting means, which connect the floor panels
vertically and/or horizontally. By "mechanical locking
system" is meant that joining can take place without glue.
Mechanical locking systems can in many cases also be
combined with gluing. By "integrated with" means formed in
one piece with the panel or factory connected to the
panel.
By a "flexible tongue" is meant a separate tongue which
has a length direction along the joint edges and which is
forming a part of the vertical locking system and could be
displaced at least partly horizontally during locking. The
whole tongue could for example be bendable or it could
have flexible and resilient parts that can be bend to a
locked position or that could bent and spring back to its
initial position.
By "angling" is meant a connection that occurs by a
turning motion, during which an angular change occurs
between two parts that are being connected, or
disconnected. When angling relates to connection of two
floor panels, the angular motion takes place with the
upper parts of joint edges at least partly being in
contact with each other, during at least part of the
motion.
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By an "angling locking system" is meant a mechanical
locking system which could be connected vertically and
horizontally with angling comprising a tongue and a grove
that locks two adjacent edges in a vertical direction and
a locking strip with a locking element in one edge of a
panel called "strip panel" that cooperates with a locking
groove on another edge of a panel called "grove panel" and
locks the edges in a horizontal direction. The locking
element and the locking groove have generally rounded
guiding surfaces that guide the locking element into the
locking groove and locking surfaces that locks and
prevents horizontal separation between the edges.
With "installation angle" is meant the generally used
angel between two panels which are in the initial stage of
an angling installation when one panel is in an upwardly
angled position and pressed with its upper edge against
the upper edge of another panel laying flat on the sub
floor. The installation angle is generally about 25
degrees and in this position there is only two contact
points between the strip panel and the grove panel. In
very special cases, where there may be more than two
contact points between the connectors, the installation
angle is higher then 25 degrees.
With "three point contact angle" is meant the angle
between two floor panels during angling when there are at
least three contact points between parts of the locking
system.
With "contact angle" is meant the angle of the folding
panel when the short edge of one panel is brought in the
initial contact with the part of the flexible tongue which
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is intended to be displaced horizontally and which is
active in the vertical locking at the short edges.
With "guiding angle" is meant the angle between two floor
panels during angling when guiding surfaces of the locking
element on the locking strip and/or on the locking groove
are in contact with each other or with the upper part of
the locking element or the lower part of the locking
groove respectivelly . Guiding surfaces are often rounded
or bevelled parts that during angling press the upper
edges of the panels towards each other and facilitate the
insertion of the locking element into the locking groove.
Most locking systems on the market have a guiding angle of
about 5 degrees
With "locking angle" is meant the angle between two floor
panels at a final stage of an angling action when the
active locking surfaces on the locking element and the
locking groove are in an initial contact with each other.
Most locking systems have locking angles of about 3
degrees or lover.
With "friction angle" is meant the angle when a friction
along long edges increase considerably during angling from
an installation angle due to the fact that more than two
contact points are active in an angling locking system and
counteracts displacement along the long edges.
With "tongue pressure" is meant the pressure in N when a
tongue is in a predetermined position. With "maximum
tongue pressure" is meant the pressure of the tongue when
it is in the inner position during vertical folding and
with " tongue pre tension" is meant the tongue pressure in
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locked position when the tongue presses against a part of the
tongue grove.
Summary of the Invention
According to an embodiment, there is provided a set
of essentially identical floor panels each comprising long and
short edges provided with first and second connectors, the
connectors are integrated with the floor panels and configured
to connect adjacent edges, the first connector comprises a
locking strip with an upwardly directed locking element at an
edge of one floor panel and a downwardly open locking groove at
an adjacent edge of another floor panel for connecting the
adjacent edges horizontally in a direction perpendicular to the
adjacent edges, the second connector comprises a tongue at an
edge of one floor panel, extending horizontally perpendicular
to the edge and a horizontally open tongue groove in an
adjacent edge of another floor panel for connecting the
adjacent edges in vertical direction, the connectors at the
long edges are configured to be locked with angling and the
connectors at the short edge are configured to be locked with
vertical folding, whereby a long edge of a new panel in a
second row is configured to be connected to a long edge of a
first panel in a first row by angling, whereby a short edge of
the new panel and a short edge of a second panel in a second
row are configured to be connected with the same angle motion,
and wherein the connectors of the long edges have at least
three separate contact points or contact surfaces between
adjacent parts of the connectors when the new panel is pressed
with its upper edge against the upper edge of the first panel
at an angle against the principal plane of at least about 10
degrees, and wherein the tongue at the short edges comprise a
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separate material and is provided with a flexible part which is
configured to be displaced horizontally during the folding and
to cooperate with the tongue groove in the adjacent short edge
for locking the floor panels together in a vertical direction
parallel to the vertical plane.
According to another embodiment, there is provided a
set of essentially identical floor panels each comprising long
and short edges provided with first and second connectors, the
connectors are integrated with the floor panels and configured
to connect adjacent edges vertically and horizontally whereby
the long edges are configured to be locked with angling and the
short edges with vertical folding, and wherein the connectors
of the long edges have at least three separate contact points
or contact surfaces between adjacent parts of the connectors
when one panel is pressed with its upper edge against the upper
edge of another panel at an angle against the principal plane
of at least about 10 degrees, and wherein a tongue at the short
edges comprise a separate material and is provided with a
flexible part which is configured to be displaced horizontally
during the folding and to cooperate with a tongue groove in the
adjacent short edge for locking the floor panels together in a
vertical direction parallel to the vertical plane.
The present invention aims at a set of floor panels
or a floating flooring with a mechanical locking system which
will improve installation of floor panel installed with
vertical folding and which will counteract or prevent
separation of the short edges during installation.
The invention is based on a first basic understanding
that such separation problems are mainly related to the locking
system at the long edges. All known locking systems, that are
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used to lock panels with angling, are very easy to displace
along the joint when the floor panels are in an initial angled
position in relation to each other. The friction increases
considerably at a low angle, when the floor panels are almost
in a locked position. This means that the friction between the
long edges is not sufficient to prevent displacement of the
short edges during the initial stage of the vertical folding
when the angle is high and when a part of the flexible tongue
has to be pressed horizontally in order to allow the vertical
folding. The friction between long edges will in most locking
systems increase at a low angle but this is a disadvantage
since the short edges could already have been separated and the
locking system on the short edge is not capable to overcome the
friction in a low angle and to pull together the short edges.
The separation makes installation more complicated since panels
have to be angled and pressed sideway during installation and
there is a considerable risk that the locking system on the
short edge will be damaged.
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The main objective of some embodiments of the invention is to
solve the separation problem between the short edges by, contrary to
the present technology, increasing the friction between
the long edges, when the long edges are in an angled
position and prior to their final locked position. The
increased friction between the long edges could counteract
or even prevent displacement along the joint of the long
edges during the vertical folding when the flexible tongue
is pressing the floor panels away from each other and it
could counteract or even completely prevent separation of
the short edges during such installation.
The invention is based on a second understanding that the
combined function of the long edge locking system and the
short edge locking system is essential in a floor, which
is designed to be installed with vertical folding. Long
and short edge locking systems should be adapted to each
other in order to provide a simple, easy and reliable
installation.
The invention provides for new embodiments of locking
systems at long and short edges according to different
aspects offering respective advantages. Useful areas for
the invention are floor panels of any shape and material
e.g. laminate; especially panels with surface materials
contain thermosetting resins, wood, HDF, veneer or stone.
The invention comprises according a first principle floor
panels with long edges having a locking system that at an
angle, larger than used by the present known technology,
counteracts displacement along the joint when panels are
connected with vertical folding.
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According to one embodiment of the first principle, the
invention provides for a set of essentially identical
floor panels each comprising long and short edges and
provided with first and second connectors integrated with
5 the floor panels. The connectors are configured to connect
adjacent edges. The first connector comprises a locking
strip with an upwardly directed locking element at an edge
of one floor panel and a downwardly open locking groove at
an adjacent edge of another floor panel for connecting the
10 adjacent edges horizontally in a direction perpendicular
to the adjacent edges. The second connector comprises a
tongue at an edge of one floor panel, extending
horizontally perpendicular to the edge and a horizontally
open tongue groove in an adjacent edge of another floor
panel for connecting the adjacent edges in vertical
direction. The connectors at the long edges are configured
to be locked with angling and the connectors at the short
edge are configured to be locked with vertical folding. A
long edge of a new panel in a second row is configured to
be connected to a long edge of a first panel in a first
row by angling. A short edge of the new panel and a short
edge of a second panel in a second row are configured to
be connected with the same angle motion. The connectors of
the long edges have at least three separate contact points
or contact surfaces between adjacent parts of the
connectors when the new panel is pressed with its upper
edge against the upper edge of the first panel at an angle
against the principal plane of at least 10 degrees.
As the floor panel according to the first principle of
the invention is provided with long edges which at an
angling angle of 10 degrees have three contact points, a
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considerable friction between long edges will be created and
this friction will counteract or prevent displacement of the
short edges caused by the pressure of the tongue during the
vertical folding. The advantage is that the flexible tongue
could be formed and positioned on the short edge with an
initial contact point which is located close to the long edge,
for example at a distance of about 15 mm from the long edge,
and this will allow a vertical locking over a substantial
length of the short edge.
Improved installation function could be obtained in some
embodiments if the three point contact angle is greater than
10 degrees, preferably 15 degrees or higher. In other
embodiments, more than 18 or even more than 20 degrees are
required to obtain an easy installation.
According to a second principle of the invention, the
position and shape of a preferably flexible tongue at the short
edge and the locking system on the long edges are such that the
friction along the long edges will increase when the panel is
angled downwards from an installation angle to a contact angle
when the flexible tongue due to the vertical folding action
will come into initial contact with the adjacent short edge and
when further angling will cause a first flexible edge of the
flexible tongue to be displaced horizontally and to create a
horizontal separation pressure of the short edges.
According to an embodiment of this second principle, the
invention provides for a set of essentially identical floor
panels each comprising long and short edges and provided with
first and second connectors integrated with the floor panels.
The connectors are configured to connect
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adjacent edges. The first connector comprises a locking
strip with an upwardly directed locking element at an edge
of one floor panel and a downwardly open locking groove at
an adjacent edge of another floor panel for connecting the
adjacent edges horizontally in a direction perpendicular
to the adjacent edges. The second connector comprises a
tongue at an edge of one floor panel, extending
horizontally perpendicular to the edge and a horizontally
open tongue groove in an adjacent edge of another floor
panel for connecting the adjacent edges in vertical
direction. The connectors at the long edges are configured
to be locked with angling and the connectors at the short
edge are configured to be locked with vertical folding. A
long edge of a new panel in a second row is configured to
be connected to a long edge of a first panel in a first
row by angling. A short edge of the new panel and a short
edge of a second panel in a second row are configured to
be connected with the same angle motion. The tongue at the
short edges is made of a separate material, connected to a
connection groove and has a flexible part with an edge
section located closest to the long edge of the first
panel. The edge section is configured to be displaced
horizontally during the folding and to cooperate with the
tongue groove of an adjacent short edge for locking the
floor panels together in a vertical direction. The first
and second connectors on the long edges are configured
such that a friction force along the long edges is lower
in an installation angle than in a contact angle when the
panels are pressed against each other with the same
pressure force and with the upper joint edges in contact.
The installation angle is 25 degrees and the contact angle
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is a lower angle corresponding to an initial contact
between the edge section and the adjacent short edge.
The increased friction between the long edges at the
contact angle could be obtained in many alternative ways
for example by increasing the pressure between contact
points and/or by increasing the size of contact surfaces
at the contact points between the first and second
connections and/or by increasing the contact points from 2
to 3 or from 3 to 4.
According to a third principle of the invention a locking
system is provided on the long edges with friction means
such that the friction will be high along the long edges
in an angled position when there are only two contact
points between the connectors on the long edges.
According an embodiment of this third principle the
invention provides for a set of essentially identical
floor panels each comprising long and short edges and
provided with first and second connectors integrated with
the floor panels. The connectors are configured to connect
adjacent edges. The first connector comprises a locking
strip with an upwardly directed locking element at an edge
of one floor panel and a downwardly open locking groove at
an adjacent edge of another floor panel for connecting the
adjacent edges horizontally in a direction perpendicular
to the adjacent edges. The second connector comprises a
tongue at an edge of one floor panel, extending
horizontally perpendicular to the edge and a horizontally
open tongue groove in an adjacent edge of another floor
panel for connecting the adjacent edges in vertical
direction. The connectors at the long edges are configured
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to be locked with angling and the connectors at the short
edge are configured to be locked with vertical folding. A
long edge of a new panel in a second row is configured to
be connected to a long edge of a first panel in a first
row by angling. A short edge of the new panel and a short
edge of a second panel in a second row are configured to
be connected with the same angle motion. The tongue at the
short edges is made of a separate material, connected to a
connection groove and has a flexible part which is
configured to be displaced horizontally during the folding
and to cooperate with the tongue groove of an adjacent
short edge for locking the floor panels together in a
vertical direction. The first and second connectors on the
long edges comprise friction means configured to increase
friction along the long edges when the panels are in an
angle where there are only two contact points between the
first and second connectors.
The friction means could or could not be active at lower
angles when there are three or more contact points in the
locking system.
The third principle offer the advantages that friction
along the long edges could be high even at a high angle
for example at the installation angle and this could be
used in connection with an installation method where an
edge of the flexible tongue is compressed by the
displacement of the long edge during an initial stage of
the vertical folding as shown in figures 4b and 4c. The
friction means will prevent or counteract displacement
along the long edges and separation of the short edges
during vertical folding.
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Such friction means could comprise mechanically formed
devices as for example small protrusions formed by
rotating tools or pressure wheels on parts of the locking
system for example on the tongue and/or on the locking
5 strip. They could also comprise chemicals or small
particles, which are applied in the locking system in
order to increase friction along the long edges.
According to a fourth principle of the invention a
flooring system with a locking system on the long and
10 short edges is provided where the floor panels could be
locked with vertical folding and where the position, shape
and material properties of a preferably flexible tongue on
the short edge is combined with a long edge locking system
comprising connectors which allow that a floor panel cut
15 to a length of 20 cm could be connected to an other panel
in the same row with vertical folding and that the
friction between the long edges will prevent separation of
the short edges.
According to one embodiment of this fourth principle a
set of essentially identical floor panels each comprising
long and short edges and provided with first and second
connectors integrated with the floor panels. The
connectors are configured to connect adjacent edges. The
first connector comprises a locking strip with an upwardly
directed locking element at an edge of one floor panel and
a downwardly open locking groove at an adjacent edge of
another floor panel for connecting the adjacent edges
horizontally in a direction perpendicular to the adjacent
edges. The second connector comprises a tongue at an edge
of one floor panel, extending horizontally perpendicular
to the edge and a horizontally open tongue groove in an
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adjacent edge of another floor panel for connecting the
adjacent edges in vertical direction. The connectors at
the long edges are configured to be locked with angling
and the connectors at the short edge are configured to be
locked with vertical folding. A long edge of a new panel
in a second row is configured to be connected to a long
edge of a first panel in a first row by angling. A short
edge of the new panel and a short edge of a second panel
in a second row are configured to be connected with the
same angle motion. The tongue at the short edges is made
of a separate material, connected to a connection groove
and has a flexible part which is configured to be
displaced horizontally during the folding and to cooperate
with the tongue groove of an adjacent short edge for
locking the floor panels together in a vertical direction.
The connectors on long and short edges are configured such
that the second and new panel, whereby one of said panels,
cut to a length of about 20 cm, is not displaced away from
the other panel when said panels are in a contact position
at an installation angle and during the vertical folding.
The fourth principle offer the advantages that floor
panels with such a locking system could be installed with
high precision and that separation of short edges will not
take place even when panels are cut to small pieces and
installed as a first or a last panels in a row. A
separation of some 0,01 mm could be sufficient to create
problems and undesired gaps, which could be visible in a
floor surface or where moisture could penetrate into the
joint.
The second object of some embodiments of the invention is to
provide an installation method to connect floor panels with vertical
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folding. The panels have an angling locking system on the
long edges and a vertical folding system on the short
edges for locking the panels vertically and horizontally,
whereby a first and a second panel are laying flat on a
sub floor with the long edges connected to each other,
characterized in that the method comprises the steps of
a) bringing a long edge of an angled new panel in
contact with the upper part of a long edge of the
first panel and
b) bringing a short edge of the new panel in contact
with a short edge of the second panel, whereby the
new panel is maintained in this position by the
locking system on the long and/or short edges,
c) pressing a short edge section of the new panel
downwards towards the sub floor and thereby
connecting the first, second and third panel to each
other with vertical folding
This installation method allows that floor panels will be
maintained in an angled up position by for example the
upper part of a locking element and the lower part of a
locking groove. This will facilitate installation since
the installer could change hand position from bring a
panel into an installation angle and than to a position
suitable to press down the short edge section of this
panel towards the sub floor. The advantage is that the
combined actions of pressing together upper edges in an
angle, pressing the panel sideways to avoid separation of
short edges and folding down the panel to the floor, could
be avoided and replaced by three separate and independent
actions.
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A third objective of some embodiments of the invention is to
provide new locking system or combinations of locking systems that
could be used on long and/or short edges and that are
especially designed to reduce separation problems. These
locking systems could of course be used separately to
connect any type of floorboards or building panels on
short and/or long edges.
According to a first aspect of this third objective a
flexible tongue is provided that comprises two flexible
parts, an inner flexible part which is located in an inner
part of a displacement groove and an outer flexible part
located at the outer part of the displacement groove and
that locks into a tongue groove of an adjacent edge of
another panel. The inner part is preferably more flexible
than the outer part and could preferably be displaced to a
grater extent than the outer more rigid part that locks
the panels vertically. The invention makes it possible to
combine strength and low displacement resistance.
According to a second aspect of this third objective a
short edge locking system with a preferably flexible
tongue is combined with a compact tongue lock system that
could be locked with angling. Such a locking system is
cost effective and the geometry is favourable and could be
used to design a locking system that creates considerable
friction along the long edge during angling. Such a tongue
lock could replace the long edge locking system with a
protruding strip in all principles and methods described
above. This embodiment of the invention has a first
connector which comprises a tongue with an upwardly
directed locking element at an upper part of the tongue at
an edge of one floor panel and a second connector
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comprising a downwardly extending locking groove located
in an undercut tongue groove at an adjacent edge of
another floor panel for connecting the adjacent edges
horizontally and vertically. The connectors at the long
edges are even in this embodiment configured to be locked
with angling and the connectors at the short edge are
configured to be locked with vertical folding. As an
example it could be mentioned that according to the first
principle, the connectors of the long edges have at least
three separate contact points or contact surfaces between
adjacent parts of the connectors when the new panel is
pressed with its upper edge against the upper edge of the
first panel at an angle against the principal plane of at
least 10 degrees.
According to a third aspect of this third objective a
short edge locking system with a preferably flexible
tongue is provided which counteracts or prevents
displacement of the long edges during vertical folding.
The locking system comprises, as described before, a strip
with a locking element and a separate flexible tongue in a
strip panel, a tongue groove and a locking groove in the
folding panel. The locking surface of the locking groove
is essential vertical and parallel with the vertical plane
VP and has preferably a height, which is at least 0,1 time
the floor thickness. The locking system is preferably
designed such that the locking element with its upper part
of the locking surface is in contact with the lower part
of the locking surface of the locking groove in a locking
angle when there are no contacts between the fold panel
and the flexible tongue. The essentially vertical locking
surface will prevent separation when the tongue during
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further angling is in contact with the fold panel. A part
of the locking surfaces are in a preferred embodiment
located on a protrusion and in a cavity.
It is obvious that two or more or even all of the
5 principles described above could be combined and that all
embodiments of locking systems described in this
application could be used in combinations or independently
to connect long and/or short edges. The figures are only
used to show examples of different embodiments, which
10 could be used in various combinations on long and short
edges in a same panel type or in different panel types
intended to be connected to each other. All locking
systems on long and/or short edges of a panel could be
formed in one piece with the core or they could comprise
15 separate materials, for example a separate tongue and/or
strip, which could be integrated with the floor panel or
connected during installation. Even the locking groove
and/or the tongue groove could be made of separate
materials. This means that the invention also comprises
20 one piece locking systems on the short edges where parts
of the locking system, such as for example the tongue
and/or the strip and/or the locking element, are flexible
and preferably comprise wood fibre based material, for
example HDF, and which could be locked by vertical
folding, provided that such locking systems create a
separation force during locking. A separate wood fibre
based material could also be fixed connected to the panel
edge by for example gluing, and it could be machined to a
locking system in the same way as the one piece system
described above.
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The invention is useful in all types of floorings. It is
however especially suitable for short panels for example
40 - 120 cm where the friction along the long edges is
low, for wide panels with a width of more than 20 cm since
the flexible tongue is long and will create an extensive
tongue pressure, and for panels with for example a core of
HDF, compact laminate or plastic materials and similar
where the friction is low due to very smooth and low
friction surfaces in the locking system. The invention is
also useful in thin panels, for example with a thickness
of 6-9 mm, more preferably thinner 8 mm and thinner and
especially is such panels with compact locking systems on
long edges, for example with locking strips shorter than 6
mm, since such floor panels and such locking system will
have small contact surfaces with low friction.
Several advantages could be reached with a flooring
system configured according to one or several of the
principles described above. A first advantage consists in
that installation could be made in a simple way and no
sideway pressure has to be applied during installation in
order to prevent floorboards to separate at the short
edges. A second advantage is that the risk of edge
separation, which could cause cracks in the locking system
during folding, is reduced considerably. A third advantage
is that locking systems could be formed with more rigid
and stronger tongues that could lock the panels vertically
with higher strength and a substantial tongue pre tension.
Such tongues with substantial maximal tongue pressure and
pre tension pressure in locked position will create high
separation forces during the vertical folding. A fourth
advantage is that the flexible tongue could be positioned
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close to the long edge and a reliable locking function
could be obtained in spite of the fact that such flexible
tongue will create a separation pressure at a rather high
contact angle.
A measurement of the initial contact friction and the
installation friction should be made according to the
following principles. The contact angle of a new floor
board and a first floor board should be measured when a
first edge section of the flexible tongue, which is active
in the vertical locking, is in a first contact with the
short edge during the initial stage of the vertical
folding action. The contact friction along the long edge
of a 200 mm sample should be measured at this contact
angle when the panels are pressed against each other with
a normal installation pressure of 10 N. The installation
friction should be measured according to the same method
at an installation angle of 25 degrees. The contact
friction should be at least about 50% higher than the
installation pressure.
Friction means comprising mechanical devices such as
protrusions, brushed fibres, scraped edge and similar in a
locking system are easy to detect. Chemicals are more
difficult.
Another method should be used to measure increased
friction due to friction means if it is not clear and
obvious that mechanical devices, chemicals, impregnation,
coating, separate materials etc have been used in order to
increase friction between floorboards in an installation
angle. A new locking system with essentially the same
design as the original sample should be produced from the
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same original floor panels and core material. The friction
should be measured at the same installation angle and
pressure and the friction between the two samples, the
original sample and the new sample, should be compared.
This testing method assumes of course that the whole core
does not contain friction-increasing materials.
A lot of HDF based floor panels on the market have been
tested and the result is that a sample with a 200 mm long
edge which is pressed against an other long edge with a
pressure of 10 N at an angle of 25 degrees generally have
a friction of about 10 N or lower. This is too low to
prevent displacement of the short edges during vertical
folding. Friction means could increase the friction
considerably.
The contact angle is defined as the angle of the new
panel when an edge is in initial contact with the part of
the flexible tongue, which is intended to be displaced,
and is active in the vertical locking. There could be for
example protrusions at the edge of the tongue that are not
causing any major horizontal pressure during vertical
folding. Such protrusions and similar devices should not
be considered to be a part of the flexible tongue.
All references to "a/an/the [element, device, component,
means, step, etc]" are to be interpreted openly as
referring to at least one instance of said element,
device, component, means, step, etc., unless explicitly
stated otherwise.
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Brief Description of the Drawings
Figs la-d illustrate a prior art locking system
Figs 2a-b show a prior art flexible tongue during
the locking action.
Figs 3a-b show a floor panels with a prior art
mechanical locking system on a short
edge.
Figs 4a-d show how short edges of two floor panels
could be locked with vertical folding
according to prior art.
Figs 5a-e show embodiments of short edge locking
systems which could be used in
connection with the invention.
Figs 6 a-c shows displaceable tongues in
embodiments according to the invention.
Figs 7a-d shows in a 3D view separation between
panels during vertical folding
Figs 8a-d show separation pressure of the
tongue on the short edge, during
installation.
Figs 9a-o show locking systems used in large
volumes on the market and contact points
between surfaces in such systems at
various angles during installation with
angling.
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Figs 10a-c show embodiments of the long edge
locking systems with a friction angle of
10 degrees according to the invention.
Figs ha-c show embodiments of the long edge
5 locking systems with a friction angle of
15 degrees according to the invention.
Figs 12a-c show long and short edge locking systems
and the position of a flexible tongue
according to embodiments of the
10 invention
Figs 13a-d show embodiments of the panel position
at the contact angle.
Figs 14a-d show the position of the flexible tongue
in relation to the long edge according
15 to embodiments of the invention.
Figs 15a-c show an embodiment with friction means
according to the invention.
Figs 16a-d show a method to measure friction forces
at various angles according to
20 embodiments of the invention.
Figs 17a-c show alternative embodiments with three
contact points according to the
invention.
Figs 18a-c show further alternative embodiments
25 with three contact points according to
the invention.
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Figs 19a-c show further alternative embodiments
with two and three contact points which
creates friction according to the
invention.
Figs 20a-c show alternative embodiments with four
contact points at an angle of 20 degrees
according to the invention.
Figs 21a-d show a flexible tongue with two flexible
parts
Figs 22a-c show installation of panels with a
flexible tongue according to the
invention
Figs 23a-b show a tongue lock system
Figs 24a-e show locking system that could be used
in the invention
Figs 25a-c show methods to measure contact poins
Figs 26a-d show embodiments of the invention with
vertical locking surfaces
Figs 27a-c show locking systems on long and short
edges according to the invention
Description of Embodiments of the Invention
Figures 1 - 6 and the related description below describe
published embodiments and are used to explain the major
principles of the invention and to show examples of
embodiments that could be used in the invention. The
showed embodiments are only examples. It should be
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emphasized that all types of flexible tongues and one
piece tongues which could be used in a locking system
allowing vertical folding and/or vertical locking, could
be used and applicable part of this description form a
part of the present invention.
A prior art floor panel 1, l' provided with a mechanical
locking system and a displaceable tongue is described with
reference to Figs la-id.
Figure la illustrates schematically a cross-section of a
joint between a short edge joint edge 4a of a panel 1 and
an opposite short edge joint edge 4b of a second panel 1'.
The front faces of the panels are essentially positioned
in a common horizontal plane HP, and the upper parts 21,
41 of the joint edges 4a, 4b abut against each other in a
vertical plane VP. The mechanical locking system provides
locking of the panels relative to each other in the
vertical direction D1 as well as the horizontal direction
D2.
To provide joining of the two joint edges in the D1 and
D2 directions, the edges of the floor panel have in a
manner known per se a locking strip 6 with a locking
element 8 in one joint edge, hereafter referred to as the
"strip panel" which cooperates with a locking groove 14 in
the other joint edge, hereafter referred to as the "fold
panel", and provides the horizontal locking.
The prior art mechanical locking system comprises a
separate flexible tongue 30 fixed into a displacement
groove 40 formed in one of the joint edges. The flexible
tongue 30 has a groove portion Pl, which is located in the
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displacement groove 40 and a projecting portion P2
projecting outside the displacement groove 40. The
projecting portion P2 of the flexible tongue 30 in one of
the joint edges cooperates with a tongue groove 20 formed
in the other joint edge.
The flexible tongue 30 has a protruding part P2 with a
rounded outer part 31 and a sliding surface 32, which in
this embodiment if formed like a bevel. It has upper 33
and lower 35 tongue displacement surfaces and an inner
part 34.
The displacement groove 40 has an upper 42 and a lower 46
opening, which in this embodiment are rounded, a bottom 44
and upper 43 and lower 45 groove displacement surfaces,
which preferably are essentially parallel with the
horizontal plane HP.
The tongue groove 20 has a tongue-locking surface 22,
which cooperates with the flexible tongue 30 and locks the
joint edges in a vertical direction Dl. The fold panel 1'
has a vertical locking surface 24, which is closer to the
rear face 62 than the tongue groove 20. The vertical
locking surface 24 cooperates with the strip 6 and locks
the joint edges in another vertical direction. The fold
panel has in this embodiment a sliding surface 23 which
cooperated during locking with the sliding surface 32 of
the flexible tongue 30.
The flexible tongue could be wedge shaped and could be
locked in the tongue grove with pre tension which will
press the folding panel l'against the strip panel. Such an
embodiment will give a very strong high quality joint.
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Figure 3a shows a cross section A-A of a panel according
to figure 3b seen from above. The flexible tongue 30 has a
length L along the joint edge, a width W parallel to the
horizontal plane and perpendicular to the length L and a
thickness T in the vertical direction Dl. The sum of the
largest groove portion P1 and the largest protruding part
P2 is the total width TW. The flexible tongue has also in
this embodiment a middle section MS and two edge sections
ES adjacent to the middle section. The size of the
protruding part P2 and the groove portion P1 varies in
this embodiment along the length L and the tongue is
spaced from the two corner sections 9a and 9b. The
flexible tongue 30 has on one of the edge sections a
friction connection 36 which could be shaped for instance
as a local small vertical protrusion. This friction
connection keeps the flexible tongue in the displacement
groove 40 during installation, or during production,
packaging and transport, if the flexible tongue is
integrated with the floor panel at the factory.
Figure 2a and 2b shows the position of the flexible
tongue 30 after the first displacement towards the bottom
44 of the displacement groove 40. The displacement is
caused essentially by bending of the flexible tongue 30 in
its length direction L parallel to the width W. This
feature is essential for this prior art. Embodiments that
are on the market have a maximum tongue pressure of about
20 N.
The fold panel could be disconnected with a needle shaped
tool, which could be inserted from the corner section 9b
into the tongue grove 20 and press the flexible tongue
back into the displacement groove 40. The fold panel could
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than be angled up while the strip panel is still on the
sub floor. Of course the panels could also be disconnected
in the traditional way.
Figure 4a shows one embodiment of a vertical folding. A
5 first panel 1" in a first row R1 is connected to a second
1 panel in a second row R2. A new panel 1' is moved with
its long edge 5a towards the long edge 5b of first panel
1"at a normal installation angle of about 25-30 degrees,
pressed to the adjacent edge and connected with its long
10 edge 5a to the long edge 5b of the first panel with
angling. This angling action also connects the short edge
4b of the new pane 1' with the short edge 4a of the second
panel 1. The fold panel 1' is locked to the strip panel 1
with a combined vertical and turning motion along the
15 vertical plane VP. The protruding part P2 has a rounded
and or angled folding part P2'which during folding
cooperates with the sliding surface 23 of the folding
panel 1'. The combined effect of a folding part P2', and a
sliding surface 32 of the tongue which during the folding
20 cooperates with the sliding surface 23 of the fold panel
1' facilitates the first displacement of the flexible
tongue 30. An essential feature of this embodiment is the
position of the projecting portion P2, which is spaced
from the corner section 9a and 9b. The spacing is at least
25 10 % of the length of the joint edge, in this case the
visible short edge 4a.
Figure 4b-c show an embodiment of the set of floor panels
with a displaceable tongue and an alternative installation
method. In this embodiment the length of the tongue is of
30 more than 90% of the width WS of front face of the panel,
in other preferred embodiments the length of the tongue is
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preferably in the range from 75% to substantially the same
as the width WS of front face. Preferably, the length of
the tongue is about the total width of the panel minus the
width of the locking system of the adjacent edges of the
panel. A small bevel may be provided at the ends of the
outer edge, but the straight part of the tongue at the
outer edge has preferably a length substantially equal to
the length of the tongue or desirable more than 90%. The
new panel l' is in angled position with an upper part of
the joint edge in contact with the first panel 1" in the
first row. The short edges 4a and 4b are spaced from each
other. The new panel l', is then displaced sideways
towards the second panel 1 until the short edges 4a, 4b
are essentially in contact and a part of the flexible
tongue 15 is pressed into the displacement groove 40 as
can be seen in the figure 4b. The new panel l' is then
folded down towards the second panel 1. Since the
displacement of the new panel l' presses only an edge
section of the flexible tongue 30 into the displacement
groove 40, vertical folding will be possible to make with
less resistance. Installation could be made with a
displaceable tongue that has a straight outer edge. When
panels with the known bow shaped tongue 30 (see figure 2-
4) are installed the whole tongue has to be pressed into
the displacement groove. When comparing the known bow
shaped tongue with a tongue according to the invention
less force is needed for a tongue with the same spring
constant per length unit of the tongue. It is therefore
possible, to use a tongue with higher spring constant per
length unit and higher spring back force, resulting in
more reliable final position of the tongue. With this
installation method, the bevelled sliding surface of the
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fold panel is not necessary, or may be smaller, which is
an advantage for thin panel. The disadvantage of this
method is that the new panel has to be angled and pressed
sideways during the vertical folding. Figure 4c show that
all embodiments of a tongue could be on the folding panel.
Of course some adjustments are required.
It is generally an advantage to have the tongue on the
strip panel since rounded or bevelled parts on the folding
panel could be used to facilitate displacement of flexible
parts of the tongue. An embodiment with a tongue, which is
on the folding panel, as shown in figure 4d, will have the
disadvantage that the tongue must slide against a sharp
edge of the panel surface.
A tongue could comprise of plastic material and could be
produced with for example injection moulding. With this
production method a wide variety of complex three-
dimensional shapes could be produced at low cost and the
flexible tongues may easily be connected to each other to
form tongue blanks. A tongue could also be made of an
extruded or machined plastic or metal section, which could
be further shaped with for example punching to form a
flexible tongue. The drawback with extrusion, besides the
additional productions steps, is that it is hard to
reinforce the tongue, e.g. by fibres.
Any type of polymer materials could be used such as PA
(nylon), POM, PC, PP, PET or PE or similar having the
properties described above in the different embodiments.
These plastic materials could, when injection moulding is
used, be reinforced with for instance glass fibre, Kevlar
fibre, carbon fibre or talk or chalk. A preferred material
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is glass fibre, preferably extra long, reinforced PP or
POM.
Figures 5a - 5e shows embodiments of flexible tongues 30,
which could be used to lock short edges according to the
invention. Figure 5a shows a separate tongue 30 on the
folding panel with a flexible snap tab extending upwards.
Figure 5b shows a separate tongue 30 on the strip panel
with a flexible snap tab extending downwards. Figure 5c
shows a separate tongue with a flexible snap tab inside a
displacement grove 40. The snap tab could extend upwards
or downwards and could be on the strip panel or on the
folding panel according to the same principles as shown in
figures 5a and b. Figure 5 d shows a flexible tongue
comprising protrusions, as shown in figure 6a and these
protrusions could be located in the displacement groove 40
or extend from the vertical plane into the tongue grove
20. Figure 5e shows that the tongue 30 could be formed in
one piece with the panel and locking could be obtained due
to compression of fibres or parts of the panel material
and/or bending of the strip 6.
Figure 6a-c shows embodiments of the tongue 30 which
could be used according to the invention. They are all
configured to be inserted in a groove in a floor panel.
Figure 6a shows a flexible tongue 30 with flexible
protrusions 16. Figure 6b shows a bow shaped tongue 30 and
figure 6c shows a tongue 30 with a flexible snap tab 17.
A flexible tongue similar to the embodiment shown in
figures 1-4, 5d 6a and 6b could for example also be
produced from a wood fibre based material, for example
HDF, solid wood or plywood with several layers. Extremely
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strong and flexible tongues could be made of HDF
especially if the design is such that flexibility is
obtained essentially parallel with the fibre orientations
of the HDF fibres.
Figure 7a-d shows in 4 steps installation with vertical
folding and problems related to such installation. In
order to simplify the description, an embodiment is shown
with the flexible tongue 30 on the strip panel. As
explained before the tongue could be on the folding panel.
A new panel 1' is moved in an installation angle with its
long edge 5a towards the long edge of a first panel 1"
until the upper edges are in contact. The new panel is
thereafter displaced sideway until the short edge 4b is in
contact with a short edge of an adjacent second panel in
the same row, as shown in figure 7a. The new panel 1' is
than angled down to a contact angle when an edge part 30'
of the flexible tongue 30 is in a first initial contact
with the short edge of the new panel as shown in figure
7b. Further angling, which for optimal function should be
made with contact between the short edges, will gradually
push a larger part of the flexible tongue horizontally and
the flexibility of the tongue will create an increasing
pressure that could push the short edges 4a and 4b away
from each other. Un undesired gap G will be created as
shown in figure 7c. The locking element 8 will in many
cases not be able to pull back the short edges of the
panels since the friction between the long edges could be
substantial when the panels are at a low angle and the gap
G will be maintained in the connected stage as shown in
figure 7d. This could cause cracks or other damages in the
locking system. Even very small remaining gaps of 0,01 -
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0,1 mm could cause major problems since moisture could
easily penetrate into the joint.
Figures 8a-8d show in detail the separation problems
caused by the flexible tongue 30. The panels 1, 1' are
5 according to figure 8a in a contact angle with the sliding
surfaces 23, 32 of the folding panel 1' and the flexible
tongue in contact. Figure 8b and 8c shows that the
flexibility of the tongue will create a separation
pressure SP which could separate the panels 1, 1' from
10 each other and create a gap G if the panels are not
pressed together by the installer. Figure 8d shows the
panels in locked position with a permanent gap G. In this
case the locking strip 6 is bended and the locking element
8 is only partly in the locking groove 14. In the worst
15 case there will be cracks in the locking element 8 and the
panels will not be locked horizontally at the short edges.
Figures 9a - 90 shows 3 types of angling locking systems
which are used in large quantities in traditional
floorings locked with angling. Figures 9a-c show the floor
20 panels in an installation angle A of 25 degrees. In this
position there are only two contact points CP3 and CP2 or
CP3, CP4 between the first and second connectors. There is
always an upper contact point CP3 or contact surface at
the upper joint edges and a second lower contact point or
25 contact surface CP4, CP2 on the lower part of the tongue
or somewhere between the inner lower part of the tongue 10
and the locking groove 14. The displacement friction along
the joint edges is in this position very low especially in
HDF based floorings with smooth surfaces. Figures 9d-f
30 shows further angling to an angle of 15 degrees and
figures 9g-I shows an angle of 10 degrees. In these
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positions there are still only two contact points and the
friction remains low. Figures 9j-1 shows the position at
an angle of 5 degrees, which in these embodiments is the
friction angle. Figures 9j and 9k show that the locking
systems are in a locking angle where the locking surfaces
51,52 are partly in contact. Figure 9 1 shows a locking
system in a guiding angle with the guiding surfaces 11,12
in contact. Figure 9j shows that this locking system has 4
contact points, two upper contact points at the upper
joint edges CP3 and at the upper part of the tongue CP1
and two lower contact points at the lower part of the
tongue CP2 and between the locking surfaces CP4. Figure 9k
shows two upper CP1, CP3 and one lower contact point CP4.
Figure 91 is similar to figure 9j but one lower contact
point is between the guiding surfaces 11, 12. The
displacement friction along the joint edges will in these
positions increase considerably especially if there is a
tight fit between the contact points or contact surfaces
and/or if the contact surfaces are of a considerable size.
Pre tension could increase the friction further and a
displacement along the long edges in connection with
vertical folding could be counteracted and in most cases
completely eliminated even in small pieces of floor
panels. Such locking systems are however not suitable on
the long side in a vertical folding system where the
contact angle is higher than 5- 8 degrees, especially if
they are produced with a normal fit between the
connectors, since they will not prevent displacement along
the long edges and separation of the short edges.
Figure 10a shows an embodiment according to the first
object of the invention. Such a locking system could
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preferably be used on the long edges in a vertical folding
system with a contact angle A of about 10 degrees and
lower. It will also be possible to use such a system in
locking systems with a higher contact angle since such
system will prevent displacement already at 10 degrees
when most fold down locking systems create the highest
displacement pressure. Figure 10a show the position of
panel 1' at an angle of 15 degrees when only two points
CP3, CP2 are in contact. Panel l'a is in a friction angle
position of 12 degrees with three contact points CP3, CP2,
CP4'. This position is characterized by the fact that
there is only one contact point CP2 on the tongue and that
the guiding surfaces 11,12 are in contact. This is an
advantage since the guiding surfaces will press the tongue
into the groove during further angling which is shown in
figure 10b. The friction has increased further and is
caused by vertical contacts and cooperation between the
tongue 10 and the tongue groove 9 (CP1,CP2), the
horizontal contacts between the upper edges CP3 and the
guiding surfaces 11, 12 which form the second lower
contact point CP4. The ideal position is preferably an
embodiment with a contact angle equal or lower than the
friction angle and the guiding angle. Such embodiment
could for example have a friction and guiding angle of
about 10 degrees and a contact angle of about 8-9 degrees.
The locking could be made in an extremely simple way and
only a downward pressure on the new panel has to be
applied when the panel is positioned at a guiding angle.
Figure 10c show that the locking system is configured with
a high angle between the locking surfaces and that fibres
during the final stage of angling, shown by the position
l'a, must be compressed at top edges CP4 and at locking
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surfaces CP4 in order to allow locking. This
configuration gives several advantages. The friction will
increase and be at a high level when the separation force
is at the highest level. The floor panels will be
maintained in an angled up position by the locking element
and the locking groove, as shown in figure 10b
independently or in combination with a contact between the
short edge of the folding panel and an edge section of the
flexible tongue. The friction will prevent the short edge
to slide away from the flexible tongue. This will
facilitate installation since the installer could change
the hand position from bringing the panel into the
installation angle to a vertical pressing action at the
short edge. The invention therefore provides a vertical
locking system with a long edge angling system that allows
one panel to stay in an angled position against another
panel with upper joint edges in contact. It also provides
a locking system where there is an increasing pressure
between the upper joint edges and the locking element
and/or between the tongue and the grove in an final stage
of angling when the a part of the locking groove 14 is in
contact with the locking element 8.
Figures 11a-11c show that the same principles could be
used to form a locking system with an even higher friction
angle A of for example 15 degrees as shown in figure ha.
The locking element 8 has been made higher and it extends
in this preferred embodiment vertically LH from the lowest
point of the locking strip 6 about 0,2 times the floor
thickness T. The tongue has a lower part 54, which is
essentially parallel with the horizontal plane HP and
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which extends from the vertical plane VP preferably along
a distance TD of about 0,1 times the floor thickness T.
The importance of the contact angle and the combined
function of the long and short edges during vertical
folding and vertical locking will now be explained with
reference to figures 12a- 13d
Figure 12a shows a long edge locking system 1", l' and a
short edge locking system 1,1' in an installed flooring
system which is intended to be locked with vertical
folding or vertical locking. The long edges have a locking
system that is possible to lock with angling. The short
edges have a locking system that is possible to lock with
vertical locking or vertical folding
Figure 12 b shows the position of the sliding surface 23
of for example a new panel l' seen from a second panel 1
towards the new panel l' when the new panel l' is moved
vertically downwards. This locking could be used to for
example connect the first row. The sliding surface 23 is
in a plane which is located in the lower part of the panel
l'
Figure 12c shows the position of sliding surface 32, the
tip 31 of the flexible tongue and the sliding surface 23
when the first 1", and the second panel 1 are laying flat
on the floor.
Figures 12b and 12 c show that position of the flexible
tongue in the length direction of the short edge is not
important in a vertical locking where the whole panel is
moved vertically downwards.
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Figure 13a shows an embodiment of the same locking system
as in figures 12 during vertical folding The edge of a
flexible tongue 30 is in this embodiment positioned at a
distance FD from the long edge of the first panel 1"
5 Figure 13 b shows vertical folding of a corner section CS
and the position of the new panel 1' when it is close to a
contact angle. Due to the bevelled sliding surfaces 23, 32
there is not yet any contact between the folding panel 1'
and the flexible tongue 30. Figure 13c shows the contact
10 angle, which in this embodiment is 10 degrees. The sliding
surfaces 32,23 overlap each other at an initial contact
point CP5. Further angling will start to create a
gradually increased separation pressure between the short
edges of the panels 1, 1' since a larger part TPC of the
15
flexible tongue will be pressed horizontally inwards into
a displacement groove by the sliding surface 23 of the
folding panel 1' as shown in figure 13d.
Figure 14a and 14b shows the position of the flexible
tongue 30 in two embodiments of the invention. The
20 flexible tongue 30 is in these embodiments bendable in the
length direction horizontally. The edge of the flexible
tongue is in the figure 14a located in a position FD1
close the long edge 5b, for example about 15 mm from the
edge. Such a locking system will in a laminate floor with
25 a normal thickness have a contact angle of about 10
degrees. The contact angle could be lower if the edge of
the tongue will be positioned at a distance FD2 further
away from the long edge 5b as shown in figure 14b. In this
case locking systems with a lower contact angle could be
30 used. Such an embodiment could be sufficient in thick and
stable floor panels or narrow floor panels. In thinner
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floor boards, for example 6 - 8 mm laminate and veneered
floorings, it is an advantage if the flexible tongue could
lock the short edges close the to long edge and over a
substantial distance of the short edge. Figures 14c and
14d show the flexible tongue in an essentially contact
position when a first part of the flexible tongue 30 has
been bended horizontally and pressed horizontally inwards
into the displacement groove. It is obvious that the
separation pressure will increase when a larger part of
the tongue is bended and pressed horizontally sideways
during the folding action. These and previously described
embodiments show that the long and short edge locking
systems are dependant of each other and must be adapted to
each order in order to guarantee a simple and reliable
locking function.
Figures 15a-c show friction means 53,53' which in this
embodiment are formed as small local protrusions on the
upper part of the locking strip 6 on the strip panel 1 and
on the lower part of the tongue or on the groove panel 1'.
Such protrusions could be formed on other surfaces in the
locking system and they will prevent displacement at high
angles for example when there are only two contact points
as shown in figure 15a. The friction means could also
comprise any type of materials or chemicals such as small
hard particles, rubber, binders and similar materials that
are applied in the locking system. Preferred materials are
soft waxes such as Microcrystalline waxes or paraffin
based waxes which could be applied on one or several
surfaces in the locking system, for example on the tongue
and or the tongue groove, on the strip, on the locking
element and/or in the locking groove, on one or both
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guiding surfaces etc. and they could increase the initial
friction between especially HDF surfaces. In a plywood
core different layers and fibre structure could be used to
form a tongue 10 and a strip 6 such that high friction is
obtained during angling. The above mentioned friction
means could be combined. Local small protrusions, rough
surfaces, oriented fibre structures etc could for example
be combined with wax or chemicals
Figure 16a-d show methods to measure friction between
long edges of floor panels. A sample of a groove panel 1'
with a width W2 of about 200 mm is pressed with a pressure
force Fl of 10 N at an angle A against a strip panel 1",
which is fixed and has a with W1 exceeding 200 mm. The
pressure force Fl is applied on the groove panel l'with a
wheel which rotates with low friction. The displacement
friction is defined as the maximal force F2 which is
required to displace the groove panel l'along the joint.
The curve Fa in Figure 16 b shows measurements made on a
sample of a 8 mm laminated panel with a surface of printed
paper impregnated with thermosetting resins and with a HDF
core. Friction should be measured from an installation
angle and gradually at lower angles. The displacement
friction of this sample is at an installation angle IA
about 10 N and almost the same at a contact angle CA of 10
degrees. The friction angle FA is in this sample about 5
degrees. Many HDF based locking systems on the market have
a displacement friction below 10 N at the installation
angle. The friction could be as low as 5 N. The long edges
will in such locking system only contribute marginally to
counteract displacement of the short edges during the
initial stage of the vertical folding since the friction
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angle is lower than the contact angle. The curve Fb shows
a special locking system where the friction, due to the
geometry of the locking system, at an installation angle
is higher than at a lower angle. The invention is based on
the principle that friction should be increased at the
contact angle compared to a installation angle or any
other angle between the installation angle and the contact
angle where the friction force is at the lowest level. A
preferred embodiment is that the friction at the contact
angle exceeds 15 N and still more, preferable 20 N. A
preferred embodiment is also a vertical locking system
with a flexible tongue that creates a tongue pressure of
more than 20 N, even more than 30 N
There are locking systems on the market that show rather
high friction at high angles. Such locking systems are not
possible to angle down from an installation angle to a
contact angle or a guiding angle in a normal way with a
pressure Fl of 10 N, which corresponds to a 60 N pressure
force applied to a floor panel of 120 cm during
installation and they are a type of locking systems where
angling must be combined with very hard pressure or a snap
action in an angled position. Such locking systems are not
used in vertical folding systems. They are not excluded
according to the invention but they are not favourable in
an vertical folding system since they will only
marginally, in some specific applications, improve
installation compared to the traditionally used
installation with angling short and long edges, snapping
short and long edges or angling long edges and snapping
short edges.
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Figure 16c shows a more favourable locking system
according to the invention where the friction angle FA is
about 15 degrees and the contact angle CA 10 degrees. The
friction angle FA is higher than the contact angle CA and
the friction between the long edges has increased
considerably at the contact angle CA compared to the
installation angle IA. Figure 16d shows how two samples 1,
1' with a width W3 of 200 mm are installed and according
to the forth principle of the invention, such an
installation should not cause a separation of the short
edges when the folding panel is pressed to the sub floor,
exclusively vertically and without any sideways pressure
towards the short edge, provided that the panels have
locking systems according to the invention. The test could
also be made with one full size panel 1 and one panel 1'
cut to a length of about 20 cm. Such locking system with a
long edge friction that prevents displacement of such
small floor pieces, will allow an easy installation, not
only of the ordinary floor panels but also of all the cut
to size floor panels close to the wall.
Figure 17a-c show how the locking system in figure 11
could be adjusted in order to create a friction with
initially three contact points CP3, CP1 and CP4. The
friction is mainly obtained by the pressure between the
locking element 8/locking groove 14 and the upper part of
the tongue 10/ tongue-groove 9. The tongue has in this
embodiment a lower part 54 which is essentially parallel
with the horizontal plane HP and which extends from the
vertical plane preferably along a shorter distance TD then
in figure 11 and which is less than 0,1 times the floor
thickness T.
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Figure 18a-18c show that the locking system in figure 11
could also be adjusted in order to create a friction with
initially three other contact points CP3, CP1 and CP3. The
friction is mainly obtained by the pressure between the
5 upper and lower parts of the tongue 10/tongue groove 9.
The tongue has in this embodiment a lower part 54 which is
essentially parallel with the horizontal plane HP and
which extends from the vertical plane preferably along a
the same distance TD as in figure 11. The height LH of the
10 locking element is however lower. Friction means 53 are
shown in the form of wax, on the lower part on the tongue
10. The wax should preferably be rather soft and it should
preferably be possible to deform during the angling. This
soft wax will prevent initial displacement along the
15 joint. Such wax could be applied in all locking system and
it would prevent displacement especially against surfaces
made of HDF.
Figure 17 and 18 show that a lot of combinations of
friction angles and friction points could be obtained if
20 the dimensions of the tongue 10, groove 9, strip 6 locking
element 8 and the locking groove 14 are adjusted within
the principles of the invention.
Figure 19a shows an embodiment with a friction angle of
20 degrees where the friction is obtained with only two
25 contact points CP1 and CP2 between the upper and lower
parts of the tongue 10/ tongue-groove 9. The tongue has in
this embodiment also a lower part 54, which is essentially
parallel with the horizontal plane HP, and which extends
from the vertical plane along a distance TD of more than
30 0,2 times the floor thickness T. The tongue has in this
embodiment a space 55 between the lower part of the tongue
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and the tongue groove which facilitates the locking and
allows that the guiding surfaces 11,12 are overlapping at
a high angle of for example 15 degrees as shown in figure
19b.
Figure 20a-c show that it is possible to design a locking
system with three contact points CP3, CP1 and CP2 at an
installation angle of 25 degrees as shown in figure 20a.
The locking element has been made even higher (LH) than in
the previous embodiments and the groove panel 1' has a
protrusion 56 between the tongue 10 and the tongue groove
9. The upper portion of the tongue has an angle against
the horizontal plane and this facilitates machining with
large rotating tools of the tongue groove 9.
A simple vertical locking on the short edge does not give
any major improvement over the present technology if it is
not combined with a well functioning long edge locking
system with superior guiding and locking properties that
allow a connection of long and short edges with a simple
angling action. As can be seen from the embodiments shown
in for example figures 10b, 11a, 17a, 13c 18b, 19b and
20b, it is possible to form a locking system with a
combined friction angle and guiding angle and with a
locking element 8 and a locking groove 14 that holds the
folding panel in an angled up position. The only action,
which is than required to lock the panels, is a vertical
pressing on the folding panel close to the short edges.
The invention provides, based on this principle, an
installation method of three panels where the first 1"
and the second panel 1 is laying flat on the sub floor
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with the long edges connected to each other as for example
shown in figure 7a. The method comprises the steps of
a) bringing a new panel 1' in an angled position with a
long edge 5a in contact with the upper part of a
long edge 5b of the first panel 1" and
b) bringing a short edge 4b of the new panel 1' in
contact with a short edge 4a of the second panel 1
such that the new panel 1' is maintained in this
position by the locking system on the long and/or
short edges. The new panel 1' could be maintained in
this position by the guiding surface of the locking
element and the locking groove as shown in figure
10a and/or by the edge of the flexible tongue.
c) pressing a short edge section of the new panels
downwards towards the floor and thereby connection
the first, second and third panel to each other with
vertical folding preferably without substantial
visible gaps between the short edges.
This installation method allows that floor panels will be
maintained in an angled up position by for example the
guiding surfaces 11,12 as shown in figure 10. This will
facilitate installation since the installer could change
hand position from a first position where the panel is
brought into an installation angle of 25 degrees, pressed
towards the edge of the already installed first panel 1"
and preferably angle down slightly to the friction and
guiding angle. The installer can then move his hands to a
second position suitable to press down preferably both
short edge section of panel towards the sub floor. The
guiding surfaces will guide the locking element into the
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locking groove and the tongue in the tongue groove. The
friction between long edges will prevent displacement. The
advantage is that the combined actions of pressing
together upper edges in an angle, pressing the panel
sideways to avoid separation of short edges and folding
down the panel to the floor, could be avoided and replaced
by two or three separate and simple independent actions.
Figures 21a - c show a flexible tongue 30 with an inner
62 and an outer 61 flexible part. Flexible tongues as
shown in figures 5a- 5c suffers from the following
disadvantages
1. They are generally made from an extruded plastic
section that is cost effective but the production
tolerances are not sufficient to obtain a high quality
locking.
2. The flexibility is not sufficient due to the fact that
only one flexible snap tab is used that bends over a very
limited vertical distance in thin floorboards. This low
flexibility creates substantial separation forces of the
edges.
3. It is difficult to combine flexibility and locking
strength especially in flexible tongues as shown in
figures 5a, b. The embodiment according to the invention
reduces or eliminates the above-mentioned problems. The
inner flexible part 62 is not a part of the vertical
locking and could therefore be made very flexible since
its main function is to displace the flexible tongue 30 in
a displacement groove. The upper part 67 of the inner
flexible part will be pressed against an inner part of a
displacement groove and will be bended or compressed as
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soon as an edge of a floor panel is pressed against the
outer flexible part 61. It is proffered that the outer
part 61 is more rigid and stronger than the inner part 62.
The combined flexibility of the inner and outer parts
could be designed to give a stronger locking with less
separation force than the known tongues. The flexible
tongue 30 could of course have one or several for example
W-shaped inner parts and/or outer parts extending
vertically up or down and this could be used to create
more flexibility and displacement. Such tongue could also
be made with a rigid outer part that is not bendable. The
tongue could be connected to the folding panel. The outer
flexible part 61 will in such an embodiment extend
vertically upwards and lock against an upper part of a
tongue groove.
Figure 21b shows that an extruded tongue made of for
example plastic or metal could be equalized by for example
machining or grinding. This will improve production
tolerances considerably to a level similar to injection
moulding or even better. Displacement, locking function
and locking strength could be improved considerably. In
the shown embodiment the lower contact surface 64 and/or
the locking surface 65 has been equalized prior to the
insertion into the displacement groove 40. A part of the
flexible tongue, preferably the outer flexible part 61
could be equalized when the tongue is or has been
connected to the edge. This could be obtained in a
separate production step or in line when the locking
system is formed. The flexible tongue could be designed
such that it bends horizontally in the length direction
during vertical folding. Such bending will be facilitated
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and separation forces will be reduced if a tongue section
68 at an edge as shown in figure 21d is removed. This
means that the width W of the tongue 30 will vary along
the length L. Such tongue section could also be removed
5 from the inner resilient part 67 and the tongue will bend
in the length direction with less resistance and
facilitate the vertical folding. Such forming with a cut
of part at an edge section could be made in all types of
extruded tongues especially in such tongues that have a
10 limited flexibility, for example the embodiment with only
one outer resilient or flexible part as shown in figures
5a, 5b and 6c. The flexible tongue could also be designed
according to the hinge principle with a rigid protrusion
and a flexible knee joint such that it does not bend
15 horizontally during locking. Such embodiment could give a
strong locking. Considerable separation forces could
however occur. This could be counteracted for example with
an embodiment that comprises several inner or outer
individual flexible parts 61a, 61b which are separated
20 with a cut 69 made by for example punching or machining.
Such individual flexible parts could snap individually and
this will make it possible to reduce production tolerances
especially if the tongues are made with individual
flexible parts that have lengths which for example could
25 vary some 0,1 mm and that are designed to lock at specific
predetermined levels in relation to each other. This
ensures that some individual flexible parts always will be
in a perfect locked position. Individual separate parts
could be combined with a flexible tongue that is connected
30 in a fixed manner to the panel edge, preferably into a
groove extending horizontally.
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The invention comprises also a separate extruded flexible
tongue designed to be used for vertical locking of
floorboard characterized in that such a tongue has been
equalized preferably on an upper 63 and/or lower 64
contact surface and/or on a locking surface 65. Such a
tongue and the above described tongue with a removed edge
section could also have a shape similar to the shapes
shown in figures 5a-5c where the flexible tongue comprises
only an inner or an outer flexible snap tab.
Machining, grinding and similar production steps will
generally create a surface that differs from the extruded
virgin surface. This could in most cases be detected in a
microscope. Such machining could also be used to increase
or decrease friction between the tongue and the
displacement groove.
Figures 22a-22c shows vertical folding or vertical
locking. One panel 1' is moved preferably along the
vertical plane VP towards another panel 1. The inner
flexible part 62 will be bended vertically when an edge
section of the folding panel 1' comes in contact with an
outer part of the flexible tongue 30, preferably the outer
flexible part 61, and the flexible tongue will be
displaced inwardly into the displacement groove 40 where
it is connected preferably with a friction connection.
Gradually even this outer flexible part 61 will start to
bend as shown in figure 22b. Finally both the inner 62 and
the outer parts 62 will snap back towards its initial
positions and the flexible tongue will be displace in the
displacement groove 40 towards the tongue groove 20. The
locking surface 65 of the flexible tongue 30 will lock
against a part of a tongue groove 20. The connection
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between the tongue and the displacement groove could be
made with a small play allowing easy displacement and some
tilting of the tongue during locking. The outer flexible
part 61 is preferably during locking mainly displaced
horizontally with a minor turning around the upper knee
70. The lower contact surface 65 could be made with an
angle, which is preferably less than 10 degrees against
the horizontal plane and this will increase the locking
strength.
Figure 23a show a tongue lock system, which could be
locked with angling. The new panel 1' has a first
connector comprising a tongue 10 with a locking element 8a
at the upper part. The first panel 1" has an undercut
tongue groove 9 with an upper 6b and lower 6b lip and a
locking groove 14a formed in the upper lip 6b and
extending downwards towards the lower lip 6a. The first
and second connectors lock the panels vertically and
horizontally. The lower lip 6a extends preferably beyond
the vertical plane VP and has preferably a horizontal
contact surface, which is in contact with a lower part of
the tongue 10. The locking system could for example be
designed such that it has three contact points CP1,2,3 at
an angle exceeding 15 degrees as shown in figure 23a. The
tongue lock could be used as an alternative to the strip
lock systems in all embodiments described above. A tongue
lock on long edges could be combined with a hook system on
the short edges, which preferably only locks horizontally
as shown in figure 24d.
Figure 24a shows a locking system with a double tongue
10, 10' and two corresponding tongue grooves 9,9'which
could be used to lock the long edges with angling,
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snapping or even vertical locking if the tongues and the
strip is adjusted to allow a vertical snap action. Such
system could have more than four contact points and the
friction along the joint could be considerable.
Figure 24b shows a locking system with a separate strip
6' which also could be used to lock the long edges in the
same way as the embodiment in figure 24a. Such a strip
could comprise a material or a surface that has more
favourable friction properties than the core material.
Figure 24c shows a locking system with a separate tongue
10' that could be flexible or rigid and that could be
connected to the strip panel 1" or the folding panel l'
on long and/or short edges in order to improve friction
properties or to save material.
Figure 24d shows a hook system, which only locks
horizontally.
Figure 24e show an embodiment of a locking system with a
flexible tongue 30 made in one piece with the core. An
undercut groove 71, which is formed behind the flexible
tongue 30, could increase the flexibility of the tongue.
Such a groove could be formed, preferably by a scraping
tool, when the short edges are machined. Such scraping or
broaching technology could be used to form advanced shapes
similar to extruded plastic sections especially in fibre-
based material such as HDF but even in solid wood and
plastic materials. The flexible tongue 30 could also be
formed with large rotating tools on the folding panel l'
with an outer part that extend upwards. The locking system
could also have two flexible tongues - one on each edge.
Wood fibres in the flexible tongue could be impregnated
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and/or coated with for example a binder 70 in order to
increase the strength and flexibility. Impregnation could
be made prior or after the forming of the tongue or the
edge. The whole edge or parts of the locking system for
example the tongue groove 20, the locking element 8 or the
locking groove 14 could also be impregnated and/or coated.
The undercut groove could be filled with flexible
materials in order to improve strength and flexibility.
Vertical folding could be facilitated if the strip 6
and/or the locking element 8 could flex during the
vertical folding. Wax in the locking system will
facilitate locking. A essentially vertical groove 73,
above the strip in the folding panel 1' or a cavity 72 in
the strip 6 adjacent to the locking element 8 in the strip
panell 1 will increase the flexibility of the locking
further system and allow parts to be more flexible. Parts
78 of the lower side of the strip and/or balancing layer
could be removed and this could increase the flexibility
of the strip and allow easier bending towards the sub
floor. The folding panel could have a protrusion 74 and
preferably also locking surfaces of the type as described
in figure 27c. The flexible tongue could also be formed
from a separate material, which is fixed connected to the
panel by for example gluing, friction or snapping. Such
separate material could for example be a rather local edge
portion 77 that could be connected to the edge prior to
the final machining. The undercut grove 71 could also be
preformed before the separate material 77 is connected to
the edge of the panel. Such a connection could be made on
individual panel edges or to a panel board that is
thereafter cut to individual floor panels. The separate
material 75, 76 could also be connected to the edge of the
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strip panel 1 and/or the folding panel 1' such that it
comprises a major parts of the locking system. Such
separate material could in a wood floor preferably be
glued to the upper top layer and the lower balancing
5 layer. Separate materials could comprise of for example
solid wood which is preferably hard and flexible such as
rubber wood or birch, wood impregnated with binders, for
example acrylic binders, plastic materials, compact
laminate made of wood fibre material and phenol which also
10 could comprise glass fibre, HDF or HDF reinforced by
binders, HDF with essentially a vertical fibre
orientation, materials with several layers comprising wood
fibres and/or plastic materials and/or glass fibre. Such
materials could be used separately or in combinations. The
15 locking system could of course also be made according to
the principles described above without the undercut groove
71, for example according to the embodiment described in
figure 5e if appropriate materials and joint
configurations are used to allow the required flexibility.
20 A lot of chemicals could be used to impregnate or to coat
parts or the whole locking systems such as melamine, urea,
phenol, thermoplastic materials such as PP or PUR. Such
chemicals could be cured with for example heat, microwave,
UV or similar with or without pressure.
25 The flexible tongue 70 could in a standard HDF material
flex a few tenths of a millimetre and this could be
sufficient to obtain a vertical locking especially in a
laminate floor. Impregnation and/or coating could increase
this flexibility considerably
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According to the invention a preferred embodiment
comprising a short edge locking system is provided that
could be locked with vertical folding or vertical locking
and that is characterized in that the locking system
comprises an edge with a strip 6, a locking element 8, a
flexible tongue 30 extending downwards and formed in one
piece with a panel core or in a separate material which
iud connected in a fixed manner to the core. The flexible
tongue 30 comprises an undercut groove 70 formed behind
the tongue.
Figures 25a-c shows how the highest three point contact
angle could be correctly determined in a locking system
mainly made in a wood fibre based core material. There are
several hundred different locking systems on the market
used to connect laminate floorings only. In most of them
it is rather easy to measure the highest three point
contact angle. This is shown in figure 25a. A sample with
a width W2 and length of about 100 mm is angled down from
an installation angle with top edges in contact until a
resistance occurs from the contact between the locking
groove and the locking element. The sample should in this
position, which is the highest three point contact angle,
be able to maintain it's up angled position and it should
not fall down to the sub-floor due to the weight of the
sample. Such a locking system has a design, which is
characterized in that the three points are the upper edges
CP3, the upper part of the tongue and the groove CP1 and
the locking element/locking groove CP4. A locking system
could however have a design as showed in figures 25b,c
where the three contact points are the upper and lower
parts of the tongue together with top edges (CP1, CP2,
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CP3). Some of such locking systems will however not stand
up in an up angled position. In such systems a cross
section of a joint should be analysed in a microscope. If
lose fibres makes it difficult to define a three point
contact angle, friction should be measured as described in
figure 16. Increased friction is an indication that an
additional contact point is active in the locking system.
Figures 26a-26d shows an embodiment of a locking system
at the short edges that counteracts or prevents
displacement of the long edges during vertical folding.
Figure 26a show a cross section B-B of a short side
locking system close to the edge part where the folding
starts, as shown in figure 4a. This locking system, as
described before in connection to for example the figures
1-3, 5, and 8, comprises a strip 6 with a locking element
8 and a separate flexible tongue 30 in a strip panel 1, a
tongue groove 20 and a locking groove 14 in the folding
panel 1'. The locking surfaces are essential vertical and
parallel with the vertical plane VP. Preferably this
locking system could be designed such that the locking
element 8 with its upper part of the locking surface 8a is
in contact with the lower part of the locking surface 14a
of the locking groove 14 as shown in figure 26a, when
there are no contacts between the fold panel 1' and the
flexible tongue 30. This could be accomplished due to the
fact that there is no tongue part close to the long edge
or that the tongue is bow shaped and has no protruding
part that is in contact with the folding panel 1'. Figure
26b shows a cross cut at C-C in figure 4a. The locking
surfaces 8a,14a will prevent separation when the tongue
30 is in contact with the fold panel provided that they
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are essentially and preferably completely vertical and
that they extend vertically along a considerable distance
so that they could prevent displacement at a angle of
preferably 10 degrees or higher, even in an embodiment
where the flexible tongue 30 is positioned close to the
long edge. The locking surfaces should preferably have a
height H which is at least 0,1 or even more than 0,15 time
the floor thickness T. Vertical locking surfaces could
also be made with a height H of about 0,2*T or more.
Several alternatives are possible within the main
principle of this invention. Figure 26d shows that the
function could be equivalent if only the locking surface
14a of the locking groove 14 meets the requirements above.
The function could also be the same if the locking groove
14b is for example bow shaped towards the outer edge,
provided that there are at least two parts which are
located vertically along a vertical plane and that the
distance is about 0,1*T.
Figure 27a shows an embodiment where the locking element
8 and the locking groove 14 on the short edge is used to
prevent separation. It is an advantage if the edge 8a of
the locking element 8 is located close to the long edge 5b
of the first panel 1" since this edge will grip into the
locking groove of the new panel at a rather high angle and
the flexible tongue could be positioned such that it locks
close to the long edge. The flexible tongue 30 is in this
embodiment an extruded section with a cut of edge section
68 that facilitates horizontal displacement during
folding. High and vertical locking surfaces on the short
edges are especially suitable in locking systems with a
flexible tongue comprising an extruded plastic section and
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especially if such a section has only one outer flexible
snap tab that due to limited flexibility causes a
considerable separation pressure.
Figure 27 shows that the flexible tongue 30 could be
moved even further towards the long edge 5b and prevent
displacement along the long edge at an even higher angle
if a compact tongue lock system is used on the long edges
since such a locking system does not comprise a strip 6a
protruding far beyond the vertical plane VP.
Figure 27c show a locking system with a preferably
extruded and flexible tongue 30 and essentially vertical
locking surfaces between the locking element 8 on the
strip 6 and the locking groove 14 in the folding panel 1'.
The folding panel 1' comprises a protrusion 74 adjacent to
the locking surface of the locking groove 14 that is
received in a adjacent cavity 72 on the strip 6 and
preferably an essentially horizontal lower contact surface
24 that locks vertically against an adjacent strip contact
surface 6'. This configuration is very suitable in
flooring with a HDF core since the cavity is formed in the
lower part of the core where the density is high. The
cavity will only to a limited extent decrease the strength
of the locking system. The height H of the vertical
locking surfaces is preferably at least 0,1*T. In order to
avoid cracks when the floor shrinks and to facilitate the
fixing of the separate tongue 30 into the displacement
groove 40, the design of the locking system is preferably
such that the locking element 8 is located below a
horizontal plane H2 that comprises the lower part of the
displacement groove 40 and the locking groove 14 is
CA 02669105 2009-05-08
WO 2008/060232
PCT/SE2007/050781
located under a horizontal plane H1 that comprises the
inner part and lowest part of the tongue groove 20.
