BE1030080A1 - Panel - Google Patents

Abstract

Panel, wherein this panel (1) has at least a first pair of opposite edges (4-5) with coupling parts (6) that allow two such panels (1) to be mutually coupled, the coupling parts (6) forming a horizontal contain an active locking system which, in a coupled condition of two such panels (1), effects a locking in the plane of the panels (1) and perpendicular to the relevant edges (4-5), and in which the horizontal active locking system (8) bottom side of the panel (1) comprises protruding lip (10) with an upwardly directed locking element (11), characterized in that the upwardly directed locking element (11) adjoins the proximal top (12) of said protruding lip (10 ) at least by means of a concave surface (13-13A).

Description

1 BE2021/6042

Panel.

This invention relates to panels, more specifically to panels which are provided on opposite edges with coupling parts which allow two such panels to be locked together at the relevant edges.

Such panels, for instance floor panels, are known per se, for instance from the

WO 97/47834, WO 2011/077311, WO 2018/087637 or WO 2011/141849.

WO 97/47834 mainly discloses floor panels with a substrate and a decorative top layer, the substrate consisting of compressed and glued wood particles, as is the case with wood chipboard or wood fiber board. The panels of it

For example, WO 834 may contain a substrate of MDF or HDF (Medium or High

Density Fiberboard). With low quality or low density of the wood fiber board, MDF or

HDF, joining together, separating the coupling parts, or repeated expansion and contraction can cause cracks in the substrate material. This is also the case when working with thicker substrates, for instance with substrates with a thickness of 9 mm or more, in which case there is a zone centrally in the substrate with relatively strongly reduced mechanical properties which can be susceptible to cracking.

Floor panels with a substrate and a decorative top layer are known from WO 2011/077311, WO 2018/087637 and WO 2011/141849, wherein the substrate is a filled plastic substrate, for example obtained by extruding operations, spreading operations or calendering operations. The plastic in this case is, for example, polyvinyl chloride. The fillers can for instance comprise lime. Such panels are usually thin, for instance 5 mm or thinner, and can have a high degree of filling, for instance be filled with a filler : plastic ratio of 2:1 or more. With such panels, problems can also arise when joining together, when separating the connecting parts, or when repeatedly expanding and contracting, breaks

2 BE2021/6042 arise in the substrate material and/or deformations appear visible on the surface of the decorative top layer.

It is noted that the risk of fractures and cracks occurring when using a covering composed of panels can be quantified by means of the so-called wheelchair test (for example the wheelchair test (EN: castor chair) as described in EN 425). This involves a test in which three loaded wheels move continuously over a revolving revetment. When the tested covering is inspected regularly, the length of the connecting parts affected by cracks or breaks can be noted as a function of the number of revolutions the covering has made under the aforementioned wheels. In this way, different coatings can be compared with each other and their suitability for a particular use, for example for commercial or residential use, can be estimated.

The present invention primarily aims at an alternative panel, which, according to preferred embodiments, offers a solution to one or more of the problems with the panels of the prior art. For example, a better coupling between panels can be achieved, even in panels with zones of low density and/or a high degree of filling.

To this end, according to a first independent aspect, the invention is a panel, wherein this panel has at least a first pair of opposite edges with coupling parts, wherein the aforementioned coupling parts allow two such panels to be mutually coupled and furthermore have the following features: - the coupling parts contain a horizontal active locking system which, when two such panels are coupled, provides locking in the plane of the panels and perpendicular to the relevant edges, namely in a horizontal direction; - the coupling parts also contain a vertically active locking system which, in a coupled position of two such panels, effects a locking transverse to the plane of the panels, namely in the vertical direction;

3 BE2021/6042 in which the horizontal active locking system comprises a protruding lip at the bottom of the panel with a locking element directed upwards, and, preferably on the opposite edge, a locking element directed downwards which, in the aforementioned coupled condition, makes or can make contact with said upward locking element; characterized in that the upwardly directed locking element connects to the proximal top of said protruding lip at least by means of a curved concave surface with a radius of at least 0.7 mm, and preferably of at least 0.8 mm; and/or by means of a curved concave surface with a radius that is at least 75%, or at least 85% of the thickness of the panel, excluding any adhered underlay; and/or by means of a concave surface formed by two planes that include an angle of at least 105°, and preferably at least 110°. By forming a concave surface, or a faceted surface with two or more faces, at the junction or transition between the upwardly facing locking element and the proximal top of the cantilever lip, the risk of cracks or fractures is minimized. location of this connection or transition is minimized.

The inventors were able to determine this on the basis of a wheelchair test as described above. The first cracks in the coupling parts only appear after 25000 revolutions of the wheelchair test (EN 425). In comparison, with identical coupling means, but where the aforementioned connection is formed with a curved concave surface with a radius of 0.5 mm or less, the first cracks in the coupling parts already occur before 15000 revolutions have been completed on the wheelchair test (EN 425). The inventors were surprised to find that such a minimal intervention in the profile of the coupling parts can lead to such excellent results. The above data relates to a panel with a substrate of wood fiber board, namely HDF, with a thickness of more than 9 mm, namely about 12 mm, but the inventors have also found remarkable improvements in similar tests with thinner HDF substrates, and with substrates of filled plastic. .

It will be appreciated that said proximal top of the protruding lip preferably comprises a portion extending horizontally or substantially horizontally to said junction or transition. Preferably, if

4 BE2021/6042 not horizontal, the part concerned includes an angle with the horizontal that is less than 10°, or 5° or less.

Preferably the aforesaid contact extends over a contact area that is completely in the lower 65%, and preferably is completely in the lower 60%, and more preferably is completely in the lower 55%, of the total height over which the upwardly directed locking element extends with respect to said proximal top of the cantilever lip. In this way, a space is formed above the contact surface that can be occupied when the respective coupling parts are taken apart, for example by means of a revolving movement of the edge with the locking element pointing downwards relative to the edge with the locking element pointing upwards. .

Preferably, said contact is formed or can be formed on a surface of the downward facing locking element which, measured in the proximal direction of the panel, forms a first angle with the underside of the panel of less than 80°, preferably of less than 75°, more preferably of less than 70°, more preferably of less than 65°, and more preferably of at least 55°. The relatively low angle promotes the separation of the coupling parts, while a minimum angle of 55° still achieves a decent locking in the horizontal direction. Preferably said contact is formed or can be formed on a surface of the upwardly facing locking element which, measured distally, forms a second angle with the underside of the panel, said second angle being equal to or greater than: said first corner; preferably wherein the possible difference between the first angle and the second angle is at least 2°, more preferably at least 3°, more preferably at most 5°. In this way a good connection to the above-mentioned contact surface can be obtained, even when the above-mentioned protruding lip is slightly bent in the above-mentioned coupled condition, for instance bent downwards and/or to the side.

Preferably, the above-mentioned coupling parts can be coupled together by means of a downward movement of the relevant edges towards each other. With such coupling parts, bending and/or compression of a part of the coupling parts can take place during coupling. Such bending and/or compression can, preferably to a lesser extent, remain present in the obtained coupled condition. Such bending and/or compression can also occur when such coupling means are taken apart, for instance by means of a revolving movement.

These deformations can give rise to local stress that can lead to fracture or cracks in the substrate material. It is especially in coupling parts that benefit from compression and/or deflection when coupling and/or in the coupled condition that the concave surface or the faceted surface of the panel of the present invention offers its advantages.

A few optional features of coupling parts are discussed below, which, individually or in any combination, can mainly be applied to coupling parts that allow a coupling by means of a downward movement, but these features can also be applied more generally, for example to coupling parts that allow a coupling. by means of a turning movement and/or a horizontal sliding movement of the relevant edges towards each other.

According to a first optional feature, proximal of the upwardly directed locking element is a female part, wherein said downwardly directed locking element forms a male part and wherein the male part is arranged in the female part in said coupled condition.

According to a second optional feature, the vertically active locking system includes a first locking member and a cooperating second locking member, the first locking member being located at the distal end of the downward locking member and the second locking member being located at the proximal end of the female part is located. The first and the second locking part can herein form a contact surface, the tangent of which forms an angle with the plane of the panel of at least 15°, preferably of at least 20°, more preferably of at least 25°; and preferably less than 75°, more preferably less than 60°, more preferably less than 50° and more preferably less than 40°,

6 BE2021/6042 where this tangent is ascending in the distal direction of the female part. Such a contact surface reduces the risk of cracks or breakage occurring when the coupling parts are taken apart by means of a rotational movement.

According to a third optional feature, the first locking member includes a horizontal projecting part of the downwardly facing locking element and the second locking member includes an undercut. Alternatively, or in combination therewith, the first locking member comprises a recess in the downwardly facing locking element and the second locking member comprises a horizontal projection at a proximal edge of the female part.

According to a fourth optional feature, in the above-mentioned coupled condition, contiguous or substantially contiguous closing surfaces are formed on the upper edges of the first pair of opposite edges, preferably substantially perpendicular to the plane of the panel, the edge with the female coupling part above the said second locking part, optionally including the second locking part, does not contain any parts that protrude beyond the aforementioned closing surface.

According to a fifth optional feature, said first locking member and/or said second locking member is formed by or on a separate insert provided in the respective edge. According to an alternative, the coupling parts of the first pair of opposite edges are mainly or completely made of the material of the panel itself.

According to a sixth optional feature, the aforementioned vertical locking system includes at the distal end of the upwardly facing locking element or at the distal end of the protruding lip a locking member which cooperates with a locking member on the opposite edge of the panel coupled thereto. These are preferably coupling parts which are mainly or completely realized from the material of the panel itself.

7 BE2021/6042

According to a seventh optional feature, said protruding lip includes a recess on the underside of the distal end of the protruding lip, preferably wherein said recess extends proximally beyond the upwardly directed locking element. On the one hand, the use of such a recess increases the ease of installation, especially with coupling parts that can be coupled downwards, but increases the risk of fractures and cracks. Therefore, the use of the concave or faceted surface of the first aspect is desirable in combination with this seventh optional feature, especially when these coupling parts are mainly or completely realized from the material of the panel itself. Preferably, said recess, vertically below said concave surface, curved or not, has a height, measured perpendicular to the plane of the panel, of at least 10% and preferably of at least 15% of the total thickness of the panel.

According to an eighth optional feature, in said coupled state, contiguous or substantially contiguous closing surfaces are formed with the upper edges of the first pair of opposing edges, preferably substantially perpendicular to the plane of the panel, the center of said contacting surface being at a horizontal distance from the closing area is greater than 50% of the thickness of the panel, or is 60% or more of the thickness of the panel. This horizontal distance improves the possibility of separating the coupling parts by means of a turning movement.

Preferably, the downwardly directed locking element extends deeper in its proximal half than in its distal half, the difference in depth preferably being at least 0.20 millimeters, and more preferably at least 0.25 millimeters. Such an arrangement can increase the ease of installation since such a deeper extending portion can serve as a maneuvering portion for deflecting the upwardly directed locking element. However, such a deeper extending part also requires additional space in the female part, as a result of which a thinner part of the protruding lip can be available in the vicinity of the upwardly directed locking element. The feature of the present invention according to its first aspect,

8 BE2021/6042 where a concave surface and/or facetted surface is used for the aforementioned connection can limit this risk.

As already mentioned above with certain preferred embodiments, it is also generally preferred that the protruding lip is bent downwards in the aforementioned coupled condition. The springback force of such a lip can lead to an improved coupling strength, for example in the horizontal direction.

Preferably, the coupling part at the aforementioned opposite edge contains a tooth, the tooth at its underside containing the downwardly directed locking element, the said protruding lip being the lower lip of a groove bounded upwards by an upper lip, wherein preferably the lower lip protrudes further than the upper lip, wherein the cooperation of said tongue and groove in the said coupled condition produces a locking in the direction perpendicular to the coupled panels, or wherein, in other words, the said tongue and groove be part of the aforementioned vertical locking system. The presently preferred embodiment is mainly used in the case of coupling parts which can be fitted into each other by means of a turning movement or a horizontal sliding movement. Preferably, the tongue of a first such panel can be brought into the groove of a second such panel by means of a revolving movement and/or by means of a substantially horizontal sliding movement, possibly with a snap effect, wherein a coupling between the first such panel and the second such panel is obtained.

The panel of the invention according to its first aspect preferably has a second pair of opposing edges with coupling parts which allow two such panels to be mutually coupled together and wherein these coupling parts comprise a tongue and groove, the groove being bounded by a lower lip and an upper lip, preferably with the lower lip protruding further than the upper lip, wherein in the coupled condition the tongue and groove provide a locking in the direction perpendicular to the coupled panels, the lower lip containing an upright locking element, where the underside of the tooth has a locking element

9 BE2021/6042, where in the coupled condition the upright locking element together with the locking element on the underside of the tooth ensures a locking in the direction perpendicular to these coupled edges and in the plane of the panels. Preferably, the tongue can be brought into the groove of a second such panel by means of a revolving movement and/or by means of a substantially horizontal sliding movement, optionally with a snap effect, wherein a coupling between the first such panel and the second such panel is obtained.

Preferably, the upstanding locking element connects to the proximal top of said lower lip at least by means of a curved concave surface with a radius of at least 0.7 millimeters, and preferably of at least 0.8 mm; and/or by means of a concave surface formed by two planes that include an angle of at least 105°, and preferably at least 110°.

In coupled condition, said lower lip of the second pair of opposite edges is preferably bent downwards. The use of such coupling parts on the second pair of opposite edges may lead to less smooth locking and/or disconnection on the first pair of opposite edges, increasing the risk of cracks and/or breakage on the first pair of opposite edges. The concave or faceted surface applied to the first pair of opposite edges according to the first aspect can limit this risk.

Preferably, the panel of the invention is rectangular, either square or elongate, the first pair of opposite edges preferably forming the short edges of the panel.

With the same object as in the first aspect, the present invention is, according to an independent second aspect, a panel, said panel having at least a first pair of opposed edges with interlocking parts, said interlocking parts allowing two such panels to be mutually joined together. coupled whereby, in the coupled state, locking is obtained at the relevant edges both in a horizontal direction in the plane of the panels and perpendicular to the

10 BE2021/6042 concerning edges as in a vertical direction transverse to the plane of the panels, wherein the coupling parts are mainly designed as a tongue and a groove delimited by means of a lower lip and an upper lip, the said tongue and groove being provided being of locking elements which prevent the tongue and groove from moving apart and wherein said locking element comprises an upstanding locking element on said lower lip and cooperating downward locking element on the underside of the tooth, wherein in said engaged condition a contact surface is formed between the top of the aforementioned tooth and the underside of the aforementioned upper lip, characterized in that - the greatest thickness of the aforementioned upper lip at the location of the said contact surface is equal to, or virtually equal to, the smallest thickness of the aforementioned lower lip and/ or where the difference in thickness is less than 10%, or even 5% or less of the thickness of the panel, not including any adhered underlay; and/or wherein the lesser of said lower lip and upper lip thicknesses is at least 90% of the greater of said thicknesses; - the smallest thickness of the part of the lower lip, proximal to the upstanding locking part, is at a distal position of the upper lip, or, in other words, in the part of the lower lip that extends beyond the upper lip, or , in still other words, in the projecting part of the lower lip; and - the sum of the aforementioned greatest thickness of the upper lip, the smallest thickness of the lower lip and the greatest thickness of the tooth at the location of the aforementioned contact surface is less than, but substantially equal to, the thickness of the panel, and /or where between the aforementioned sum and the thickness of the panel is less than 10%, or even 5% or less of the thickness of the panel, not including any adhered underlay.

The combination of features of the panel of the second independent aspect also leads to a panel that has a better resistance to the occurrence of cracks and/or fractures during installation, use or de-installation. Here too, the inventors have been able to go through 25000 revolutions of the wheelchair test (EN425) without cracks or

11 BE2021/6042 fractures occurred. Without these characteristics, cracks were already detected before 10000 revolutions had been completed. The above data concern a panel with a substrate of filled plastic, namely filled PVC, obtained by extrusion and with a filling degree of more than 3:1 (filler : plastic), namely filling degree about 4 : 1, and a thickness of about 5 mm, but the inventors have also found remarkable improvements in similar tests with thinner filled plastic substrates and with wood fiber substrates. The inventors attribute the good results to optimizing the thicknesses as mentioned in the second aspect. This is because these thicknesses lead to optimum support of the coupling parts in vertical direction. The upper and lower lips are massive enough to limit the movement of the tooth, and the tooth is massive enough to bend only minimally.

It is noted that the panel of the second independent aspect may optionally exhibit the features of the first aspect and/or its preferred embodiments. In this way, additional resistance to crack formation or breaks in the coupling parts is obtained.

Preferably, the thickness of the protruding portion of the lower lip decreases continuously in the distal direction up to the position of said smallest thickness. Such a profile of the lower lip leads to a minimization of possible bending stresses in the lower lip when connecting, disconnecting and/or in the connected state and thus to a reduced risk of cracks or fractures occurring.

Preferably, said smallest thickness of the lower lip manifests itself at or just before the connection of the top of the lower lip with said upstanding locking element. In this way, the strength of the lower lip is further optimized.

Preferably, the horizontal distance from the position of said smallest thickness of the lower lip to the distal end of the upper lip is at least 50%, or 75% or more of the distance over which the lower lip protrudes beyond the upper lip.

12 BE2021/6042

Preferably, in the aforementioned coupled condition, a space is present between the top of the lower lip and the bottom of the tooth. Such space may have one or more of the following optional features.

According to a first optional feature, said space can be present at least at the location of said smallest thickness.

According to a second optional feature, said space is continuous from a position vertically below the distal end of the upper lip at least to the position of said smallest thickness. Such a space avoids additional compressive stresses on the lower lip in the coupled condition, even if, for example, the profile of the lower lip or the underside of the tooth were to move slightly due to machine tolerances.

According to a third optional feature, said space has a quasi-constant vertical dimension over at least 80% of the distance over which the space extends in the horizontal direction, said vertical dimension over the distance in question, if varying, having a variation of less than 10% or even of 5% or less. Such a constant or slightly varying space can be easily reduced in production to a space with a small vertical dimension, in such a way that the thickness of the lower and upper lip and the tooth can be maximized.

Preferably, in said coupled condition, a contact surface is formed between said upright locking element and said downwardly directed locking element, wherein this contact surface has a tangent line rising in the distal direction of the lower lip, which tangent line forms an angle of at least 45°, or at least 47.5° up to 65° with the horizontal. Preferably, the position with said smallest thickness is at a distance from the center of said contact surface, wherein this distance is less than 20% of the thickness of the panel, or is 10% or less of this thickness. Also in this embodiment the strength of the lower lip is maximized. According to another embodiment, or in combination therewith, the center of said contact surface is located on a

13 BE2021/6042 horizontal distance from the distal end of the top lip that is greater than 50% of the thickness of the panel, or 60% or more of the thickness of the panel. This improves the possibility of separating the coupling parts by means of a turning movement.

Some preferred features of the first and/or second independent aspect are explained below.

The panel preferably has a substrate and a decorative top layer applied thereto. Without intending to limit, some options for the substrate and the decorative top layer are listed below.

According to a first possibility, the substrate is a wood-based substrate, preferably a substrate that mainly consists of pressed and glued wood particles.

For example, the substrate comprises a wood fiber board, preferably an MDF or an HDF board, a chipboard or a plywood board. The substrate of this first option preferably exhibits an internal bond strength of less than 1.3

N/mm2, preferably less than 1.2 N/mm2, more preferably less than 1.1 N/mm2, or even less than 0.85N/mm2. Such internal bond strength is preferably measured in accordance with EN 319:1996. According to the most preferred embodiment of this first option, the substrate is a

HDF board, namely a wood fiber board with a density of 800 kg/m? or more, a thickness of 8 mm or more, and an internal bond strength measured according to EN 319:1996 of 1.2 N/mm? or less. It is noted that HDF boards usually used for floors show an internal bond strength of 1.5N/mm° or more. However, the present invention also allows good results to be obtained with lower quality plates. According to another preferred embodiment of this first possibility, the substrate is a wood fiber board with a density of less than 800 kg/m3, for example from 550 to 750 kg/m3, and a thickness of 8 mm or more. It is noted that HDF boards usually used for floors have a density of more than 800 kg/m? show. However, the present invention also allows good results to be obtained with wood fiber boards of a lower density.

14 BE2021/6042

According to a second possibility, the substrate is a, preferably filled, plastic substrate, preferably a substrate comprising thermoplastic plastic, such as polyvinyl chloride, polyethylene terephthalate, polyethylene or polypropylene.

In this case, the substrate may be a foamed plastic substrate, wherein, preferably, the upwardly directed locking element or upright locking element, depending on whether it concerns an embodiment of the first aspect or of the second aspect, respectively, mainly or completely in a foamed part of the substrate and/or a substrate comprising inorganic or mineral fillers, wherein the upwardly facing locking element or upstanding locking element, depending on whether it is an embodiment of the first aspect or of the second aspect, respectively, is mainly or completely in a part of the substrate which consists of at least 50% by weight, or at least 65% by weight, or at least 80% by weight of the aforementioned fillers. The invention, either according to the first aspect or the second aspect or both, always provides optimum strength, tear and fracture resistance of such coupling parts, notwithstanding that they are partly designed in a weakened, for instance foamed and/or filled, part of the substrate.

The panel of the second option can be obtained by means of plastic extrusion. In such a case, the substrate can have a degree of filling of 3:1 (fillers: plastic) or more, for example of 4:1 or more.

With both the aforementioned first possibility and with the said second possibility or in general, the said decorative top layer can comprise a printing, preferably a printing carried out on the substrate possibly with intermediate preparatory layers, a printing that is on a paper layer, the paper layer being impregnated can be with resin, for example impregnated with melamine resin or with an acrylate resin, or a print on a polymer foil, preferably a printed polyvinyl chloride foil is used.

15 BE2021/6042

In both the first possibility as well as in the second possibility or in general, said decorative top layer may comprise a transparent or translucent wear layer, the wear layer comprising one or more of - a polymer foil, for instance a polyvinyl chloride foil; - a paper layer impregnated with resin, for instance with melamine resin or with an acrylate resin, and/or - a lacquer layer, preferably an acrylate layer.

The wear layer may contain particles that increase the abrasion resistance of the wear layer, for example where these particles are corundum particles.

With the intention of better demonstrating the features of the invention, some preferred embodiments are described below, by way of example without any limiting character, with reference to the accompanying drawings, in which:

Figure 1 shows a perspective view of a step in the installation of a floor covering using panels with the characteristics of the first aspect of the invention;

Figure 2 shows a larger-scale view of the area shown in Figure 1

F2 is indicated;

Figure 3 shows a top view of a panel from figures 1 and 2;

Figure 4 shows a cross-section on a larger scale along the line IV-IV shown in Figure 3;

Figure 5 shows on an even larger scale the coupled condition of the coupling parts shown in figure 4;

Figure 6 shows a cross-section on the same scale as Figure 4 along the line VI-VI shown in Figure 3;

Figure 7, on the same scale as Figure 5, shows the coupled condition of the coupling parts shown in Figure 6;

Figures 8 to 11 show variants in a view similar to that of Figure 5, but on a smaller scale;

Figure 12 is a larger-scale view of the area indicated by F12 in Figure 5;

16 BE2021/6042

Figure 13 shows a variant in a similar view, and

Figure 14 shows in a view similar to that of Figure 7 a panel with the features of the second aspect of the invention.

Figure 1 shows schematically and in perspective a part of a floor covering consisting of panels 1, more particularly floor panels 1, according to the invention.

Figure 2 clearly shows that the panels 1 of this example are configured at their edges in such a way that they can be mutually coupled according to the so-called fold-down principle.

Figure 3 shows that these are, in this case, rectangular and elongate floor panels 1, provided with a pair of long opposite edges 2-3, and a pair of short opposite edges 4-5. In the example, both pairs of edges 2-3;4-5 are provided with coupling parts 6.

An installation with the fold-down principle, as shown in figure 2, consists in such floor panels 1 being coupled together at the long pair of opposite edges 2-3 by a revolving movement W, and at the short pair of edges 4-5 by a downward movement M can be coupled to each other, wherein the downward movement M is the result of the revolving movement W and is therefore substantially simultaneous. In this case, the floor panels 1 are also configured at their edges 2-3 and 4-5 in such a way that ultimately a locking in vertical direction V perpendicular to the plane of the coupled panels 1, and also in horizontal direction H1-H2 leads to stands. The latter in each case perpendicular to the respective respective edges 2-3; 4-5 and in the plane of the coupled panels 1.

Figure 4 shows that the coupling parts 6 at the short pair of opposite edges 4-5 contain a horizontal active locking system 8 which, in the coupled condition, shown in figure 5, effects the locking in said horizontal direction H2. The coupling parts 6 further comprise a vertically active locking system 9 which, in the coupled condition, shown in figure 5, locks the

17 BE2021/6042 achieves the aforementioned vertical direction V. The horizontal active locking system 8 comprises a lip 10 protruding from the underside of the panel 1 and comprising a locking element 11 directed upwards. The upwardly facing locking element 11 adjoins the proximal top 12 of the aforementioned protruding lip 10 at least by means of a curved concave surface 13 with a radius R of at least 0.7 millimeters, and preferably of at least 0.8 mm. In this case, the curved concave surface 13 has a radius R that is at least 75%, or at least 85% of the thickness T of the panel 1, excluding any adhered underlay 14. The thickness of any adhered underlay 14 is not taken into account, since it does not or hardly intervene in the material properties of the actual substrate 15.

The short pair of opposite edges 4-5 of the example thus exhibits the features mentioned in connection with the first pair of opposite edges mentioned in the first aspect.

The horizontal active locking system 8 comprises on the opposite edge 5 a downwardly directed locking element 16 which, in the above-mentioned coupled condition, makes or can make contact with the above-mentioned upwardly directed locking element 11. In the example, the above-mentioned contact extends over a contact surface 17 which is completely in the lower 65% of the total height H over which the upwardly directed locking element extends with respect to said proximal top 14 of the cantilever lip 10.

The aforementioned contact or the contact surface 17 is formed on the one hand on a surface of the downwardly facing locking element 16 which, measured in the proximal direction of the panel 1, has a first angle A with the underside of the panel 1 of less than 80°, and, in this case, an angle A of less than 65°, namely about 62°.

On the other hand, the aforesaid contact or the contact surface 17, in the example, is formed on a surface of the upwardly facing locking element 11 making a second angle B measured in the distally direction with the underside of the panel 1,

18 BE2021/6042 where this second angle B, here, is greater than the aforementioned first angle A. In the example, the difference between the first angle A and the second angle B is approximately 3°.

It is clear that proximal of the upwardly directed locking element 11 is a female part 18, the aforementioned downwardly directed locking element 16 forming a male part 19, the male part 19 being arranged in the female part 18 in said coupled condition.

The vertically active locking system 9 includes a first locking member 20 and a cooperating second locking member 21. The first locking member 20 is located at the distal end of the downward locking member 16 and the second locking member 21 is located at the proximal end of the female part 18 is located.

According to the example, in the engaged condition as shown in Figure 5, the first locking part 20 and the second locking part 21 form a contact surface whose tangent line T makes an angle C with the plane of the panel of at least 15°, in this case of approximately 20°, this tangent line T being ascending in the distal direction of the female portion 18.

It will be appreciated that, in the example of Figures 1 to 5, the first locking member 20 comprises a horizontal projecting part of the downwardly facing locking element 16 and the second locking member 21 comprises an undercut. In said coupled state, contiguous or substantially contiguous closing surfaces 22 are formed on the upper edges of the second or short pair of opposing edges. In the example, the closing surfaces 22 are substantially perpendicular to the plane of the panel, wherein the edge 5 with the female coupling part 18 above the aforementioned second locking part 21 does not contain any parts which, in horizontal direction, protrude beyond the aforementioned closing surface 22.

Figures 4 and 5 further show that the aforementioned protruding lip 10 contains a recess 23 on the underside from the distal end of the protruding lip 10,

19 BE2021/6042, wherein this recess extends proximally beyond the upwardly directed locking element 11. Below the aforementioned concave surface 13, the recess 23 has a height H3, measured perpendicular to the plane of the panel 1, in this case of approximately 5% of the total thickness T of the panel, not including any adhered underlayer 14. Not shown are versions in panels with a thickness T of 9 mm or more, where the height H3 is preferably at least 10% of the thickness.

T amounts to. Such panels preferably consist of wood fiber board.

The above-mentioned vertical locking system 9, in the example of figures 1 to 5, further comprises at the distal end of the upwardly directed locking element 11 or at the distal end of the protruding lip 10 a locking part 24 which cooperates with a locking part 25 on the opposite edge 4 of the associated panel 1.

Figures 6 and 7 show the long pair of opposite edges 2-3 of the panel 1. These edges 2-3 are also provided with coupling parts 6 with a horizontal active locking system 8 and a vertical active locking system 9. The horizontal active locking system 8 comprises, also here, a protruding lip 10 on the underside of the panel 1 with an upwardly directed locking element 11. The upwardly directed locking element 11 connects to the proximal top 12 of said protruding lip 10 at least by means of a curved concave surface 13 with a radius R of at least 0.7 mm, and preferably of at least 0.8 mm. In this case, the curved concave surface 13 has a radius R that is at least 75%, or at least 85% of the thickness T of the panel 1, excluding any adhered underlayer 14.

On the long edge 2 opposite the long edge 3 with the protruding lip 10, the coupling part 6 contains a tooth 26. The tooth 26 contains the downwardly directed locking element 16 on its underside. The above-mentioned protruding lip 10 is the lower lip of a groove 27 , which is bounded upwards by an upper lip 28. Here, in the example, the lower lip or protruding lip 10 protrudes further than the upper lip 28, whereby the cooperation of said tongue 26 and groove 27 in the aforementioned coupled

20 BE2021/6042 condition produces a locking in the direction V perpendicular to the coupled panels 1, or in which, in other words, the aforementioned tongue 26 and groove 27 form part of the aforementioned vertical locking system 9.

As shown in figure 6, the tongue 26 of a first such panel 1 can, as desired, by means of a revolving movement W or by means of a substantially horizontal sliding movement S, optionally with a snap effect, enter the groove 27 of a second such panel 1. can be brought, whereby a coupling between the first such panel 1 and the second such panel 1 is obtained.

It is clear that the coupling parts 6 of the long pair of opposite edges need not necessarily also have a concave surface 13. These edges can also have coupling parts comprising a tongue and groove, the groove being delimited by a lower lip and an upper lip, preferably with the lower lip protruding further than the upper lip, with the tongue and the groove for providing a locking in the direction perpendicular to the coupled panels, the lower lip containing an upright locking element, the underside of the tooth containing a locking element, wherein in the coupled condition the upright locking element together with the locking element on the underside of the tooth provide interlocks in a direction perpendicular to these mated edges and in the plane of the panels, without necessarily abutting the top of lower lip to the upstanding locking element by means of a concave surface, as mentioned in the context of the first aspect of the invention.

It is noted that coupling parts identical or similar to the coupling parts 6 as shown in figures 4 and 5 can, according to a variant, also be applied to the long pair of opposite edges 2-3. According to another variant, coupling parts identical or similar to the coupling parts 6 as shown in figures 6 and 7 can also be used on the short pair of opposite edges 4-5.

21 BE2021/6042

It is clear that the coupling parts 6 shown in figures 1 to 7 are mainly made of the material of the panel 1, more specifically of the material of the substrate 15 itself.

Figure 8 shows a variant for, for example, the coupling parts 6 on the short pair of opposite edges 4-5, the aforementioned first locking part 20 being formed by or on a separate insert 29 which is inserted into the relevant edge 4, in this case the edge 4. with the locking element 16, or male coupling part, directed downwards.

Figure 9 shows another variant for, for example, the coupling parts 6 on the short pair of opposite edges 4-5, the aforementioned second locking part 21 being formed by or on a separate insert 29 which is inserted into the relevant edge 5, in this case the edge 5 with the locking element 11 directed upwards, or the edge 5 with the female coupling part 18, 1s arranged.

The embodiments shown in Figures 8 and 9 otherwise have similar features as the coupling parts 6 of Figures 4 and 5, but in which the distal end of the protruding lip 10 is free of locking parts. For example, the concave surface 13 at the location of the connection of the upwardly directed locking element 11 to the proximal top 12 of the protruding lip 10 has identical features.

Figures 10 and 11 each time show another variant for, for instance, the coupling parts 6 on the short pair of opposite edges 4-5. The coupling parts 6 are herein realized from the material of the panel 1, more specifically of the substrate 15.

Figure 10 has substantially similar features as the coupling parts 6 shown in figures 4 and 5, but with these differences: - the aforementioned angles A and B are 90° or greater than 90°, in this case the angles A and B are both approximately 100°:

22 BE2021/6042 - the distal end of the protruding lip 10 1s free of locking elements.

In other words, the vertical locking system 9 only comprises locking parts on the distal and proximal side of the downward locking element 16, and cooperating locking parts on the opposite edge 5.

Figure 11 has substantially similar features as the coupling parts 6 shown in Figures 4 and 5, but with these differences: - the aforementioned angles A and B are 90° or greater than 90°, in this case the angles A and B are both approximately 95°: - the proximal end of the female coupling part 18 is free of locking elements. In other words, the vertical locking system 9 only comprises locking parts on the distal and proximal sides of the upwardly facing locking element 11, and cooperating locking parts on the opposite edge 4.

Figures 4, 5, 9 and 11 are further characterized in that the downwardly directed locking element 16 extends deeper in its proximal half than in its distal half.

Figure 12 again shows the concave surface 13 as it is used in the embodiment of Figures 4 and 5, and can be used in the other embodiments. Figure 12 clearly shows that, in the engaged condition, a space 30 is preferably present at the location of the concave surface 13 between the concave surface and the locking element 16 pointing downwards. This space 30 is preferably adjacent to at least 80% of the concave surface 13, and even better over the entire, or almost all, concave surface 13.

As already mentioned, the aforesaid contact extends over a contact surface 17 which is entirely in the lower 65% of the total height H over which the upwardly facing locking element 11 extends with respect to said proximal top 14 of the cantilever lip 10.

23 BE2021/6042

It is understood that the aforementioned proximal top 12 of the protruding lip 10, in this case, includes a portion extending horizontally or substantially horizontally up to the aforementioned connection or transition to the upwardly facing locking element 11. In general, it is the concave surface 13 is preferably viewed as extending from a first point 31 where the top 12 of the cantilever lip 10 diverges from the horizontal. In case the proximal top 12 of the cantilever lip 10 has a direction that per se, preferably less than 10°, deviates from the horizontal, the first point 31 is located at the position where the upper surface of the cantilever lip 10 deviates even further from the horizontal. Further, the concave surface 13 is preferably seen as extending to a second point 32 where the top surface of the cantilever lip 10 is contiguous with and oriented in the same direction as the contact surface 17.

Preferably, said space 30 extends at least between said first point 31 and said second point 32.

In general, the above-mentioned concave surface 13 may further exhibit one or more of the following properties: - the property that the concave surface 13 extends in horizontal direction

H2 over a distance HE which is greater than the distance VE over which the concave surface 13 extends in the vertical direction V. Preferably the ratio is

HE:VE between 1.65:1 and 1.2:1; - the property that the concave surface 13 extends over a horizontal distance HE greater than 40% of the height H of the upward locking element 11; - the property that the concave surface 13 extends over a horizontal distance HE which is less than 65% of the height H of the upward locking element 11; and/or - the property that the concave surface 13 extends over a horizontal distance HE between 45 and 55% of the height H of the upward locking element 11.

24 BE2021/6042

Figure 13 shows another variant in which the concave surface 13A is formed by a faceted surface, namely a concave surface 13A formed by two faces 33-34 which include an angle D of at least 105°, and preferably at least 110°. In this case, the angle D is about 150°. Otherwise, the variant of Figure 13 has the same features as Figure 12. It is obvious that this variant can be used in any embodiment of the first aspect of the invention, for example in the embodiments of Figures 1 to 11.

Figure 14 shows an embodiment with the features of the second independent aspect of the invention mentioned in the introduction. This concerns a floor panel in which coupling parts 6 are used which are mainly designed as a tongue 26 and a groove 27 bounded by a lower protruding lip 10 and an upper lip 28. The aforementioned tongue 26 and groove 27 are provided with locking elements 11- 16 preventing the tongue 26 and groove 27 from moving apart and wherein said locking elements include an upstanding locking element 11 on said lower lip 10 and cooperating downward locking element 16 on the underside of the tongue 26. Said tongue 26 and groove 27 per se form the vertically active locking system 9, while the locking elements 11-16 form the horizontally active locking system 8.

In the coupled condition, as shown in figure 14, a contact surface 35 is formed between the top of said tooth 26 and the underside of said upper lip 28. Herein, the greatest thickness DU of said upper lip 28 is at said contact surface 35 substantially equal to the smallest thickness DL of the aforementioned bottom lip 10. The difference in thickness here is less than 10%, or even 5% or less of the thickness T of the panel, excluding any adhered underlayer. In this case, the smallest of the thicknesses DU and DL is more than 90% of the largest of the thicknesses DU and DL.

25 BE2021/6042

The smallest thickness DL of the portion of the lower lip 10 proximal to the upstanding locking portion 11 is located at a distal position of the upper lip 28, or, in other words, in the portion of the lower lip 10 extending beyond the upper lip 28 extends or, in still other words, into the projecting portion of the lower lip 10. In the example, the lower lip 10 comprises a zone 36 which has the smallest thickness DL. This zone 36 extends from a proximal position 37 to a distal position 38. In this case, the distal position 38 coincides with the aforementioned first point 31 where the top 12 of the protruding lip 10 deviates from the horizontal.

The sum of the aforementioned greatest thickness DU of the upper lip 28, the smallest thickness

DL of the lower lip 10 and the greatest thickness DT of the tooth 26 at the location of the aforesaid contact surface 35 is smaller than, but substantially equal to, the thickness T of the panel 1. In this case, the difference between the aforesaid sum and the thickness is T of the panel less than 10%, ie about 7.5%.

Figure 14 clearly shows that, in this case, the thickness of the projecting portion of the lower lip 10 decreases continuously in the distal direction up to the position of the aforementioned smallest thickness DL. The aforementioned smallest thickness DL of the lower lip 10 manifests itself at the connection of the top 12 of the lower lip 10 with the aforementioned upright locking element 11. The horizontal distance HD from the most distal position with the aforementioned smallest thickness DL of the lower lip 10 to the distal end of the upper lip 28 is at least 50% of the distance HL that the lower lip 10 extends beyond the upper lip 28 .

In the example, in the aforementioned coupled condition, a space 30 is present between the top 12 of the lower lip 10 and the bottom of the tooth 26. Said space 30 is present at least at the location of the distal position with the aforementioned smallest thickness DL. Preferably, said space 30 extends adjacent to the full zone 36 exhibiting said smallest thickness DL.

The aforementioned space 30 is continuous from a position 39 vertically below the distal end of the upper lip 28 at least to the proximal position

26 BE2021/6042 37, and preferably at least up to the distal position 38 of the zone 36 with the aforementioned smallest thickness DL. Preferably, as here, said space 30 has a quasi constant vertical dimension VS over at least 80% of the distance over which the space 30 extends in horizontal direction H1. Preferably said vertical dimension VS over the distance from the position 39 below the distal end of the upper lip 28 to the proximal position 37 of said zone 36 varies less than 10% of the greatest distance VS in this distance, or even 5% or less of this greatest distance US.

Figure 14 further shows that, in the present case, in the coupled condition a contact surface 17 is formed between the aforementioned upright locking element 11 and the aforementioned locking element 16 pointing downwards, wherein this contact surface 17 has an ascending tangent in the distal direction of the lower lip 10, which tangent makes an angle A of 47.5 to 65° with the horizontal. The distal position 38 of the zone 36 with the aforementioned smallest thickness DL is herein located at a distance from the center 40 of the aforementioned contact surface 17 which is less than 20% of the thickness T of the panel 1, or 10% or less of this thickness. T amounts to.

In the embodiment of Figure 14, the center 40 of said contact surface 17 is located at a horizontal distance HC from the distal end of the upper lip 28 which is 60% or more of the thickness T of the panel 1. In this case the distance HC is about 65% of the thickness T of the panel 1.

It is clear that coupling parts 6 with the features of the second independent aspect of the invention, such as the coupling parts 6 shown in Figure 14, can be applied to any pair of opposite edges 2-3-4-5, either on the long pair of edges 2-3, either on the short pair of edges 2-3-4-5, or on both. If such coupling parts 6 are only used on the long pair of edges 2-3, it is possible to use coupling parts 6 on the short pair of edges 4-5 which allow a coupling by means of a downward movement M, such as the coupling parts 6 shown in figures 4, 5 and 8 to 13, or similar. If such coupling parts 6 are only applied to the long pair of edges 2-3, it is also possible to apply coupling parts 6 to the short pair of edges 4-5, which have a coupling by means of a

27 BE2021/6042 allow a rotational movement W and/or a horizontal sliding movement S, such as the coupling parts 6 shown in figures 6 and 7 or similar.

In connection with all the figures it is noted that the panels from the examples each time have a substrate 15 and a decorative top layer 41 applied thereto. In the embodiments of Figures 1 to 13, this preferably concerns a wood-based substrate 15, preferably a substrate consisting substantially of pressed and glued wood particles, such as an MDF or an HDF board. This may concern a substrate with an internal bond strength of less than 1.3 N/mm2. In the case of Figure 14, it is preferably a filled plastic substrate, preferably a substrate comprising thermoplastic plastic, such as polyvinyl chloride, polyethylene terephthalate, polyethylene or polypropylene. As is the case in Figure 14, the substrate 15 preferably comprises inorganic or mineral fillers, wherein, the upstanding locking element 11 is substantially or completely formed in a portion of the substrate 15 that contains at least 50 weight percent, or at least 65 weight percent, or consists of at least 80% by weight of the aforementioned fillers. The substrate 15 is preferably at least obtained by means of plastic extrusion.

In the case of Figures 1 to 13, said decorative top layer 41 contains a printing which is on a paper layer, the paper layer being impregnated with melamine resin. In the case of figure 14, said decorative top layer 41 contains a printing which is located on a polymer foil, in this case a printed polyvinyl chloride foil.

It is further noted in connection with Figure 14 that the lowered edge regions 42 shown there are entirely optional. In addition, such depressed edge regions 42 are optional in any embodiment of the present invention according to its first and/or second independent aspect. If present, they need not necessarily extend, as in Figure 14, into the substrate 15, but may be limited to the thickness of the top layer 14, or to the thickness of any wear layer. In the example of Figure 14, the depressed edge regions 42 are formed as

28 BE2021/6042 chamfers. This is also not necessary and lowered edge areas with a horizontal or almost horizontal bottom are also possible. Furthermore, such a lowered edge area 42, as in the case of Figure 14, may have been obtained by removing a material portion at the upper edge. In such a case, the surface obtained can be provided with a separate decoration. According to another possibility, a lowered edge area can for instance be obtained by a deformation of the top edge and/or the substrate 15. In such a case it is possible that the decorative top layer 41 extends uninterruptedly from the global top surface of the panel 1 to and over the surface of the depressed edge region 42, preferably up to the closure face 22.

The present invention is by no means limited to the embodiments described above, but such panels can be realized in various variants without departing from the scope of the present invention.

Claims (47)

29 BE2021/6042 Conclusions: 1.- Panel, wherein this panel (1) has at least a first pair of opposite edges (4-5) with coupling parts (6), the aforementioned coupling parts (6) allowing two such panels (1) to be mutually coupled and furthermore have the following characteristics: - the coupling parts (6) contain a horizontal active locking system (8) which, in a coupled condition of two such panels (1), locks in the plane of the panels (1) and perpendicular to the respective edges (4-5) accomplishes; - the coupling parts (6) also contain a vertically active locking system (9) which, in a coupled position of two such panels (1), effects a locking transverse to the plane of the panels (1); wherein the horizontal active locking system (8) comprises a protruding lip (10) on the underside of the panel (1) with an upwardly directed locking element (11), characterized in that the upwardly directed locking element (11) connects to the proximal located top (12) of said protruding lip (10) at least by means of a curved concave surface (13) with a radius (R) of at least 0.7 millimeters, and preferably of at least 0.8 mm; and/or by means of a curved concave surface (13) with a radius (R) that is at least 75%, or at least 85% of the thickness (T) of the panel (1), excluding any adhered underlay (14) ; and/or by means of a concave surface (13A) formed by two planes (33-34) including an angle (D) of at least 105°, and preferably at least 110°. 2. Panel according to claim 1, characterized in that the horizontal active locking system (8) on the opposite edge (4) contains a locking element (16) pointing downwards which, in the above-mentioned coupled condition, makes or can make contact with the above-mentioned pointing upwards. locking element (11). Panel according to claim 2, characterized in that the aforementioned contact extends over a contact surface (17) which is entirely in the lower 65%, 30 BE2021/6042 and preferably located completely in the lower 60%, and more preferably completely in the lower 55%, of the total height (H) over which the upwardly directed locking element (11) extends in relation to said proximal top (12) of the cantilever lip (10). Panel according to claim 2 or 3, characterized in that the aforementioned contact is formed or can be formed on a surface of the downwardly directed locking element (16) which, measured in the proximal direction of the panel, forms a first angle (A) with the bottom of the panel (1) of less than 80°, preferably of less than 75°, more preferably of less than 70°, more preferably of less than 65°, and more preferably of at least 55°. Panel according to any one of claims 2 to 4, characterized in that the aforementioned contact is formed or can be formed on a surface of the upwardly directed locking element (11) which, measured in the distal direction, forms a second angle (B) with the underside of the panel, said second angle (B) being equal to or greater than said first angle (A); preferably wherein the possible difference between the first angle (A) and the second angle (B) is at least 2°, more preferably at least 3°, more preferably at most 5°. Panel according to any one of claims 2 to 5, characterized in that the aforementioned coupling parts (6) can be coupled together by means of a downward movement (M) of the relevant edges towards each other. 7. Panel according to claim 6, characterized in that a female part (18) is located proximal of the upwardly directed locking element (11), wherein the aforementioned downwardly directed locking element (16) forms a male part, the male part being in said coupled state is arranged in the female part (18). Panel according to any one of claims 2 to 7, characterized in that the vertically active locking system (9) has a first locking part (20) and an associated 31 BE2021/6042 includes cooperating second locking member (21), with the first locking member (20) located at the distal end of the downward locking member (16) and with the second locking member (21) located at the proximal end of the female part (18). Panel according to claim 8, characterized in that in the aforementioned coupled condition the first locking part (20) and the second locking part (21) form a contact surface (35) whose tangent (T) makes an angle (C) with the plane of the panel (1) of at least 15°, preferably of at least 20°, more preferably of at least 25°; and preferably of less than 75°, more preferably of less than 60°, more preferably of less than 50° and more preferably of less than 40°, this tangent (T) being ascending in the distal direction of the female part (18). Panel according to claim 9, characterized in that the first locking part (20) comprises a horizontal projecting part of the locking element (16) directed downwards and the second locking part (21) comprises an undercut and/or that the first locking part (20 ) includes a recess in the downward facing locking element (16) and the second locking member (21) includes a horizontal projection at a proximal edge of the female member (18). 11. Panel according to claim 9 or 10, characterized in that, in the aforementioned coupled condition, closing surfaces (22) connecting or practically connecting at the top edges are formed substantially perpendicular to the plane of the panel (1), the edge with the female coupling part (18) above said second locking part (21) and/or inclusive of second locking part (21) does not contain any parts that protrude, in horizontal or distal direction, beyond said closing surface (22). Panel according to any one of claims 8 to 11, characterized in that the said first locking part (20) and/or the said second locking part (21) is formed by or on a separate insert (29) which is placed in the relevant edge ( 4-5) is fitted. 32 BE2021/6042 Panel according to any one of claims 2 to 12, characterized in that the locking element (16) directed downwards extends deeper in its proximal half than in its distal half, the difference in depth preferably being at least 0.20 millimeters. and more preferably at least 0.25 millimeters. Panel according to any of the preceding claims, characterized in that in the above-mentioned coupled condition the protruding lip (10) is bent downwards. Panel according to any one of claims 1 to 14, characterized in that the coupling parts (6) of the first pair of opposite edges (4-5) are mainly made of the material of the panel (1) itself. Panel according to claim 14, characterized in that the aforementioned vertical locking system (9) comprises at the distal end of the upwardly pointing locking element (11) or at the distal end of the protruding lip (10) a locking part (24) which interacts with a locking member (25) on the opposite edge (4) of the associated panel (1). Panel according to any one of claims 2 to 5, characterized in that the coupling part (6) has a tooth (26) on the aforementioned opposite edge (4), the tooth (26) on its underside holding the locking element directed downwards. (16), the aforesaid protruding lip (10) being the lower lip of a groove (27), bounded upwards by an upper lip (28), preferably the lower lip (10) protruding beyond the upper lip (28), wherein the cooperation of said tongue (26) and groove (27) in said coupled condition produces a locking in the direction (V) perpendicular to the coupled panels (4-5), or wherein, with in other words, said tongue (26) and groove (27) form part of said vertical locking system (9). 18. Panel according to claim 17, characterized in that the tooth (26) of a first such panel (1) is moved by means of a revolving movement (W) and/or by means of a 33 BE2021/6042 substantially horizontal sliding movement (S), possibly with snap effect, can be brought into the groove (27) of a second such panel (1), with a coupling between the first such panel (1) and the second such panel ( 1) is obtained. Panel according to any of the preceding claims, characterized in that the panel has a second pair of opposite edges (2-3) with coupling parts (6) which allow two such panels (1) to be mutually coupled and wherein these coupling parts (6) comprise a tongue (26) and groove (27), the groove (26) being delimited by a lower lip (10) and an upper lip (28), preferably wherein the lower lip (10) further then the upper lip (28) protrudes, whereby when engaged the tongue (26) and the groove (27) provide a locking in the direction (V) perpendicular to the joined panels (1), the lower lip (10) contains an upright locking element (11), the underside of the prong (26) containing a locking element (16), wherein in the coupled condition the upstanding locking element (11) together with the locking element (16) on the underside of the prong (26 ) locks in the direction (H1) perpendicular to these coupled edges (2-3) and in the plane of the panels (1). 20. Panel according to claim 19, characterized in that the tongue (26) is inserted into the groove (27) of a second such panel (1) can be brought, whereby a coupling between the first such panel (1) and the second such panel (1) is obtained. Panel according to any one of claims 19 to 20, characterized in that the upstanding locking element (11) adjoins the proximal top (12) of said lower lip (10) at least by means of a curved concave surface (13) with a radius (R) of at least 0.7 millimeters, and preferably of at least 0.8 mm; and/or by means of a concave surface (13A) formed by two planes (33-34) including an angle (D) of at least 105°, and preferably at least 110°. 34 BE2021/6042 Panel according to any one of claims 19 to 21, characterized in that in coupled condition said lower lip (10) of the second pair of opposite edges (2-3) is bent downwards. Panel according to any of the preceding claims, characterized in that the panel (1) is rectangular, either square or elongated, the first pair of opposite edges (4-5) preferably covering the short edges of the panel (1) forms. Panel according to any of the preceding claims, characterized in that said protruding lip (10) contains a recess (23) at the bottom from the distal end of the lower lip (28), preferably wherein this recess (23) is located in extends proximally beyond the upwardly facing locking element (11). Panel according to claim 24, characterized in that said recess (23), vertically below said concave surface (13-13A), curved or not, has a height (H3), measured perpendicular to the plane of the panel ( 1), of at least 10% and preferably at least 15% of the total thickness (T) of the panel (1). 26.- Panel, wherein this panel (1) has at least a first pair of opposite edges (2-3) with coupling parts (6), wherein the aforementioned coupling parts (6) allow two of such panels (1) to be mutually coupled whereby, in the coupled condition, a locking is obtained at the relevant edges (2-3) both in a horizontal direction (H1) in the plane of the panels (1) and perpendicular to the relevant edges (2-3) and in a vertical direction (V) transverse to the plane of the panels (1), wherein the coupling parts (6) are mainly designed as a tooth (26) and a delimited by means of a lower lip (10) and an upper lip (28). groove (27), said tongue (26) and groove (27) being provided with locking elements (11-16) preventing the tongue (26) and groove (27) from moving apart and wherein said locking elements comprise an upright locking element ( 11) comprise on said lower lip (10) and co-acting downwardly facing locking element (16) on the underside of the tooth (26), forming a contact surface (35) between the top of the tooth (26) in said coupled condition. 35 BE2021/6042 said tooth (26) and the underside of said upper lip (28), characterized in that - the greatest thickness (DU) of said upper lip (28) is equal at the location of said contact surface (35), or substantially equal, to the smallest thickness (DL) of the aforementioned lower lip (10) and/or where the difference in thickness (DU-DL) is less than 10%, or even 5% or less than the thickness (T) of the panel (1), excluding any adhered underlay (14), and/or where the smallest of the aforementioned thicknesses (DU-DL) of the lower lip (10) and upper lip (28) is at least 90% of the greater of the aforementioned thicknesses (DU-DL); - the smallest thickness (DL) of the portion of the lower lip (10), proximal to the upstanding locking portion (11), is at a distal position of the upper lip (28), or, in other words, in the portion of the lower lip (10) extending beyond the upper lip (28) or, in still other words, into the projecting portion of the lower lip (10); - the sum of the aforementioned greatest thickness (DU) of the upper lip (28), the smallest thickness (DL) of the lower lip (10) and the greatest thickness (DT) of the tooth (26) at the location of the aforementioned contact surface (35) is smaller than, but substantially equal to, the thickness (T) of the panel (1), and/or in which between said sum and the thickness (T) of the panel (1) is less than 10%, or even 5% or less of the thickness (T) of the panel, not counting any adhered underlayer (14). Panel according to claim 26, characterized in that the thickness of the protruding part of the lower lip (10) decreases continuously in distal direction up to the proximal position (37) with said smallest thickness (DL). 28. Panel according to claim 26 or 27, characterized in that the aforementioned smallest thickness (DL) of the lower lip (10) manifests itself at or just before the connection of the top (12) of the lower lip (10) with the aforementioned upright locking element (11). 36 BE2021/6042 Panel according to any one of claims 26 to 28, characterized in that the horizontal distance (HD) from the distal position (38) with said smallest thickness (DL) of the lower lip (10) to the distal end of the upper lip (28) is at least 50%, or 75% or more of the distance (HL) that the lower lip (10) extends past the upper lip (28). Panel according to any one of claims 26 to 30, characterized in that in the above-mentioned coupled condition a space (30) is present between the top of the lower lip (10) and the bottom of the tooth (26). Panel according to claim 30, characterized in that said space (30) is present at least at the location of the zone (36) or position with said smallest thickness (DL). Panel according to claim 30 or 31, characterized in that said space (30) is continuous from a position (39) vertically below the distal end of the upper lip (28) at least to the proximal position (37) with said smallest thickness (DL). Panel according to any of claims 30 to 32, characterized in that said space (30) has a quasi constant vertical dimension (VS) over at least 80% of the distance over which the space extends in horizontal direction (H1), wherein this vertical dimension (VS) over the distance in question, if it varies, shows a variation of less than 10%, or even of 5% or less, and/or where this vertical dimension (VS) over the distance between the position (39 ) vertically below the distal end of the upper lip (28) and the proximal position (37) with said smallest thickness (DL), if it varies, shows a variation of less than 10%, or even of 5% or less. Panel according to any of claims 26 to 33, characterized in that in the above-mentioned coupled condition a contact surface (17) is formed between the above-mentioned upright locking element (11) and the above-mentioned pointing downwards 37 BE2021/6042 locking element (16), wherein this contact surface (17) has an ascending tangent in the distal direction of the lower lip (10), which tangent makes an angle (A) of 47.5 to 65° with the horizontal. Panel according to claim 34, characterized in that the distal position (38) with said smallest thickness (DL) is located at a distance (DC) from the center (40) of said contact surface (17), this distance (DC ) is less than 20% of the thickness (T) of the panel (1), or is 10% or less of this thickness (T). Panel according to claim 34 or 35, characterized in that the center (40) of said contact surface (17) is at a horizontal distance (HC) from the distal end of the upper lip (28) which is greater than 50% of the thickness (T) of the panel (1), or 60% or more of the thickness (T) of the panel (1). Panel according to any of the preceding claims, characterized in that the panel (1) has a substrate (15) and a decorative top layer (41) applied to it. 38. Panel according to claim 37, characterized in that the substrate (15) is a wood-based substrate, preferably a substrate (15) which mainly consists of pressed and glued wood particles. Panel according to claim 38, characterized in that the substrate (15) comprises a wood fiber board, preferably an MDF or an HDF board, a chipboard or a plywood board. Panel according to claim 38 or 39, characterized in that the substrate (15) has an internal bond strength of less than 1.3 N/mm2, preferably less than 1.2 N/mm2, more preferably less than 1.1 N/mm2. 41. Panel according to claim 37, characterized in that the substrate (15) is a, preferably filled, plastic substrate, preferably a substrate containing thermoplastic 38 BE2021/6042 plastic, such as polyvinyl chloride, polyethylene terephthalate, polyethylene or polypropylene. Panel according to claim 41, characterized in that the substrate (15) is a foamed plastic substrate, wherein, preferably, the upward locking element or upright locking element (11), depending on the embodiment, is mainly or completely in a foamed portion of the substrate (15). 43.- Panel according to claim 41 or 42, characterized in that the substrate (15) comprises inorganic or mineral fillers, wherein, preferably, the upwardly facing locking element or upstanding locking element, depending on the embodiment, is mainly or completely in part of the substrate (15) is made that at least 50% by weight, or at least 65% by weight, or at least 80% by weight, consists of the aforementioned fillers. Panel according to any one of claims 41 to 43, characterized in that the substrate (15) is obtained by plastic extrusion. Panel according to any one of claims 37 to 44, characterized in that said decorative top layer (41) contains a printing, preferably a printing carried out on the substrate possibly with intermediate preparatory layers, a printing located on a paper layer, wherein the paper layer can be impregnated with resin (preferably impregnated with melamine resin or with an acrylate resin), or a print on a polymer foil (preferably a printed polyvinyl chloride foil). Panel according to any one of claims 37 to 44, characterized in that said decorative top layer (41) contains a transparent or translucent wear layer, the wear layer comprising one or more of a polymer foil (preferably a polyvinyl chloride foil), a paper layer impregnated with resin (preferably melamine resin or an acrylic resin) or a lacquer layer (preferably an acrylic layer). 39 BE2021/6042 47. Panel according to claim 46, characterized in that said wear layer contains particles which increase the abrasion resistance of the wear layer, for example wherein these particles are corundum particles.