PANEL

Abstract

A panel has at least one first pair of opposite edges with coupling parts that allow two such panels to be couplable together. The coupling parts include a horizontally acting locking system that in a coupled state of two such panels achieves locking in the plane of the panels and perpendicular to the respective edges. The horizontally acting locking system includes a projecting lip with an upward directed locking element on the underside of the panel. The upward directed locking element abuts against the proximally located upper side of the aforementioned projecting lip at least by means of a concave surface.

Description

The present invention relates to panels, more particularly to panels that are provided on opposite edges with coupling parts that allow two such panels to be locked together on the respective edges.

Panels of this kind, for example floor panels, are known per se for example from WO 97/47834, WO 2011/077311, WO 2018/087637 or WO 2011/141849.

From WO 97/47834, mainly floor panels are known with a substrate and a decorative top layer, wherein the substrate consists of compressed and glued wood particles, as is the case with wood chipboard or wood fiberboard. The panels in WO 834 may for example comprise a substrate of MDF or HDF (Medium or High Density Fiberboard). In the case of low quality or low density of wood fiberboard, MDF or HDF, when fitting the coupling parts into each other or taking them apart, or with repeated expansion and shrinkage, cracks may develop in the substrate material. Such is also the case when working with thicker substrates, for example with substrates with a thickness of 9 mm or more; in such a case there is, located centrally in the substrate, a zone with relatively greatly reduced mechanical properties, which may be susceptible to cracking.

From WO 2011/077311, WO 2018/087637 and WO 2011/141849, floor panels are known with a substrate and a decorative top layer, wherein the substrate is a filled plastic substrate, for example obtained by extrusion operations, spreading operations or calendering operations. The plastic is in this case for example polyvinyl chloride. The fillers may for example comprise lime. Panels of this kind are usually thin, for example 5 mm or thinner, and may have a high filling ratio, for example may be filled to a ratio of filler to plastic of 2:1 or more. With panels of this kind, problems may also arise when fitting the coupling parts into each other or taking them apart, or with repeated expansion and shrinkage, cracks may develop in the substrate material and/or deformations may develop that are visible on the surface of the decorative top layer.

It is to be noted that the risk of the occurrence of fractures and cracks when using a covering assembled from panels may be quantified by means of the so-called castor chair test (for example the castor chair test as described in EN 425). This is a test wherein three loaded wheels move continuously over a rotating covering. When the tested covering is inspected regularly, the length of the coupling parts that is affected by small cracks or fractures may be noted as a function of the number of revolutions that the covering has made under the aforementioned wheels. Different coverings may in this way be compared with each other and their suitability for a particular use, for example for commercial or residential use, can be assessed.

The present invention relates firstly to an alternative panel, wherein, according to preferred embodiments, a solution is offered for one or more of the problems with the panels from the prior art. Thus, for example better coupling between panels may be obtained, even in panels with zones of low density and/or high filling ratio.

For this purpose, according to a first independent aspect, the invention is a panel, wherein this panel has at least one first pair of opposite edges with coupling parts, wherein the aforementioned coupling parts allow two such panels to be coupled together, and further have the following characteristic features:

• • the coupling parts comprise a horizontally acting locking system which, in a coupled state of two such panels, achieves locking in the plane of the panels and perpendicular to the respective edges, namely in a horizontal direction;
  • the coupling parts also comprise a vertically acting locking system which, in a coupled state of two such panels, achieves locking transverse to the plane of the panels, namely in the vertical direction;wherein the horizontally acting locking system comprises a projecting lip on the underside of the panel with an upward directed locking element, and, preferably on the opposite edge, a downward directed locking element which, in the aforementioned coupled state, comes into contact or may come into contact with the aforementioned upward directed locking element; characterized in that the upward directed locking element abuts against the proximally located upper side of the aforementioned projecting 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 an optional glued-on sublayer; and/or by means of a concave surface formed by two planes that enclose an angle of at least 105°, and preferably at least 110°. Because a concave surface, or a facetted surface with two or more planes, is formed at the abutment or transition between the upward directed locking element and the proximally located upper side of the projecting lip, the risk of the development of cracks or fractures at the location of this abutment or transition is minimized. The inventors were able to establish this on the basis of a castor chair test as described above. The first cracks in the coupling parts only occur after 25000 revolutions of the castor chair test (EN 425). For comparison, with identical coupling means, but wherein the aforementioned abutment 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 in the castor chair test (EN 425). The inventors were surprised to find that such a minimal intervention in the profile of the coupling parts could lead to such excellent results. The above data relate to a panel with a substrate of wood fiberboard, namely HDF, with a thickness of more than 9 mm, namely about 12 mm, but the inventors also found noteworthy improvements in similar tests with thinner HDF substrates, and with substrates of filled plastic.

It is clear that the aforementioned proximally located upper side of the projecting lip preferably comprises a portion that extends horizontally or approximately horizontally to the aforementioned abutment or transition. Preferably, if not horizontal, the relevant portion encloses an angle with the horizontal that is less than 10°, or is 5° or less.

Preferably the aforementioned contact extends over a contact surface that is located completely in the lowest 65%, and preferably is located completely in the lowest 60%, and more preferably is located completely in the lowest 55%, of the total height over which the upward directed locking element extends relative to the aforementioned proximally located upper side of the projecting lip. In this way, above the contact surface, a space is formed that may be occupied when taking apart the respective coupling parts, for example by means of a rolling motion of the edge with the downward directed locking element relative to the edge with the upward directed locking element.

Preferably the aforementioned contact is formed or may be formed on a surface of the downward directed locking element which, measured in the proximal direction of the panel, makes 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 small angle is favorable for taking apart the coupling parts, whereas a minimum angle of 55° still produces proper locking in the horizontal direction. Preferably the aforementioned contact is formed or may be formed on a surface of the upward directed locking element which, measured in the distal direction, makes a second angle with the underside of the panel, wherein this second angle is equal to, or is greater than, the aforementioned first angle; preferably wherein the possible difference between the first angle and the second angle is at least 2°, more preferably is at least 3°, more preferably is at most 5°. In this way, good abutment to the aforementioned contact surface can be obtained, even when the aforementioned projecting lip, in the aforementioned coupled state, is somewhat bent, for example is bent out downwards and/or sideways.

Preferably the aforementioned coupling parts may be coupled together by means of a downward motion of the respective edges toward each other. With coupling parts of this kind, a deflection and/or a compression of a portion of the coupling parts may occur during coupling. Said deflection and/or compression may, preferably to a more limited extent, still be present in the coupled state obtained. Also when taking apart said coupling means, for example by means of a rolling motion, said deflection and/or compression may occur. These deformations may give rise to local stresses, which may lead to fracture or cracking in the substrate material. It is especially in the case of coupling parts that utilize a compression and/or deflection during coupling and/or in the coupled state, that the concave surface or the facetted surface of the panel of the present invention offers its advantages.

Some further optional features of coupling parts are discussed hereunder, which, each separately or in any combination, may mainly be applied with coupling parts that allow coupling by means of a downward motion, but these features may also be applied more generally, for example with coupling parts that allow coupling by means of a rolling motion and/or a horizontal sliding motion of the respective edges toward each other.

According to a first optional feature, a female part is located proximally to the upward directed locking element, wherein the aforementioned downward directed locking element forms a male part and wherein, in the aforementioned coupled state, the male part is fitted into the female part.

According to a second optional feature, the vertically acting locking system comprises a first locking part and comprises a second locking part interacting therewith, wherein the first locking part is located at the distal end of the downward directed locking element and wherein the second locking part is located at the proximal end of the female part. The first locking part and the second locking part may thus form a contact surface whose tangent makes 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 of less than 75°, more preferably of less than 60°, more preferably of less than 50° and more preferably of less than 40°, wherein this tangent increases in the distal direction of the female part. Said contact surface reduces the risk of the development of cracks or fracture when taking the coupling parts apart by means of a rolling motion.

According to a third optional feature, the first locking part comprises a horizontal projecting component of the downward directed locking element and the second locking part comprises an undercut. According to an alternative, or in combination therewith, the first locking part comprises a recess in the downward directed locking element and the second locking part comprises a horizontal projecting component on a proximal edge of the female part.

According to a fourth optional feature, in the aforementioned coupled state, on the upper edges of the first pair of opposite edges, abutting or practically abutting sealing faces are formed, preferably substantially perpendicular to the plane of the panel, wherein the edge with the female coupling part above the aforementioned second locking part, optionally including the second locking part, does not comprise any components that project outside the aforementioned scaling face.

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

According to a sixth optional feature, the aforementioned vertical locking system comprises, at the distal end of the upward directed locking element or at the distal end of the projecting lip, a locking part that interacts with a locking part on the opposite edge of the panel coupled therewith. This preferably relates to coupling parts that are made mainly or completely from the material of the panel itself.

According to a seventh optional feature, the aforementioned projecting lip comprises a recess on the underside from the distal end of the projecting lip, preferably wherein this recess extends in the proximal direction beyond the upward directed locking element. The use of said recess increases on the one hand the case of installation, mainly with downward couplable coupling parts, but increases the risk of fractures and cracks. Therefore application of the concave or facetted surface of the first aspect is desirable in combination with this seventh optional feature, particularly when these coupling parts are made mainly or completely from the material of the panel itself. Preferably the aforementioned recess has, vertically under the aforementioned, whether or not curved, concave surface, 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 the aforementioned coupled state, on the upper edges of the first pair of opposite edges, abutting or practically abutting sealing faces are formed, preferably substantially perpendicular to the plane of the panel, wherein the center of the aforementioned contact surface is located at a horizontal distance from the sealing face that is greater than 50% of the thickness of the panel, or is 60% of the thickness of the panel or more. This horizontal distance improves the possibility of taking the coupling parts apart by means of a rolling motion.

Preferably the downward directed locking element extends deeper in the proximal half thereof than in the distal half thereof, wherein the difference in depth is preferably at least 0.20 mm, and more preferably is at least 0.25 mm. This configuration may increase the case of installation since this portion that extends more deeply may serve as a maneuvering portion for bending the upward directed locking element. However, this portion that extends more deeply also requires additional space in the female part, so that a thinner portion of the projecting lip may be present in the region of the upward directed locking element. The measure in the present invention according to its first aspect, wherein a concave surface and/or facetted surface is employed for the aforementioned abutment, may limit this risk.

As already mentioned above for certain preferred embodiments, it is also generally preferred that the projecting lip in the aforementioned coupled state is bent out downward. The resilience of said lip may lead to improved coupling strength for example in the horizontal direction.

Preferably the coupling part comprises a tongue on the aforementioned opposite edge, wherein the tongue comprises the downward directed locking element on its underside, wherein the aforementioned projecting lip is the lower lip of a groove, which is delimited upward by an upper lip, wherein preferably the lower lip projects farther than the upper lip, wherein the interaction of the aforementioned tongue and groove in the aforementioned coupled state brings about locking in the direction perpendicular to the coupled panels, or wherein, in other words, the aforementioned tongue and groove form part of the aforementioned vertical locking system. The present preferred embodiment is mainly applied in the case of coupling parts that can be fitted together by means of a rolling motion or a horizontal sliding motion. Preferably the tongue of a first such panel can be brought by means of a rolling motion and/or by means of a substantially horizontal sliding motion, optionally with a snap effect, into the groove of a second such panel, wherein coupling is obtained between the first such panel and the second such panel.

The panel of the invention preferably has, according to its first aspect, a second pair of opposite edges with coupling parts that allow two such panels to be coupled together and wherein these coupling parts comprise a tongue and groove, wherein the groove is delimited by a lower lip and an upper lip, preferably wherein the lower lip projects farther than the upper lip, wherein in the coupled state the tongue and the groove provide locking in the direction perpendicular to the coupled panels, wherein the lower lip comprises an upright locking element, wherein the underside of the tongue comprises a locking element, wherein in the coupled state, the upright locking element together with the locking element on the underside of the tongue provides locking in the direction perpendicular to these coupled edges and in the plane of the panels. Preferably the tongue can be brought by means of a rolling motion and/or by means of a substantially horizontal sliding motion, optionally with a snap effect, into the groove of a second such panel, wherein coupling is obtained between the first such panel and the second such panel.

Preferably the upright locking element abuts against the proximally located upper side of the aforementioned lower 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 concave surface formed by two planes that enclose an angle of at least 105°, and preferably at least 110°.

Preferably, in the coupled state the aforementioned lower lip of the second pair of opposite edges is bent out downward. The use of said coupling parts on the second pair of opposite edges may lead to less smooth locking and/or uncoupling on the first pair of opposite edges, so that the risk of cracks and/or fractures on the first pair of opposite edges increases. The concave or facetted surface that is provided according to the first aspect on the first pair of opposite edges may keep this risk limited.

Preferably the panel of the invention is rectangular, either square, or elongated, wherein the first pair of opposite edges preferably form the short edges of the panel.

With the same aim as in the first aspect, according to an independent second aspect, the present invention is a panel, wherein this panel has at least one first pair of opposite edges with coupling parts, wherein the aforementioned coupling parts allow two such panels to be coupled together, wherein in the coupled state locking is obtained on the respective edges both in a horizontal direction in the plane of the panels and perpendicular to the respective edges, and in a vertical direction transverse to the plane of the panels, wherein the coupling parts are configured substantially as a tongue and a groove delimited by means of a lower lip and an upper lip, wherein the aforementioned tongue and groove are provided with locking elements that prevent the tongue and the groove moving apart and wherein the aforementioned locking element comprises an upright locking element on the aforementioned lower lip and, interacting therewith, a downward directed locking element on the underside of the tongue, wherein in the aforementioned coupled state a contact surface is formed between the upper side of the aforementioned tongue and the underside of the aforementioned upper lip, with the characteristic feature that

• • the largest thickness of the aforementioned upper lip at the location of the aforementioned contact surface is equal, or is almost equal, to the smallest thickness of the aforementioned lower lip and/or wherein the difference in thickness there is less than 10%, or even 5% of the thickness of the panel or less, excluding an optional glued-on sublayer; and/or wherein the smallest of the aforementioned thicknesses of the lower lip and upper lip is at least 90% of the largest of the aforementioned thicknesses;
  • the smallest thickness of the portion of the lower lip, proximal to the upright locking portion, is located at a distal position of the upper lip, or, in other words, in the portion of the lower lip that extends beyond the upper lip or, in yet other words, in the projecting portion of the lower lip; and
  • the sum of the aforementioned largest thickness of the upper lip, the smallest thickness of the lower lip and the largest thickness of the tongue at the location of the aforementioned contact surface is less than, but is almost equal to the thickness of the panel, and/or wherein between the aforementioned sum and the thickness of the panel there is less than 10%, or even 5% of the thickness of the panel or less, excluding an optional glued-on sublayer.

The combination of characteristic features of the panel of the second independent aspect also leads to a panel that has better resistance to the development of cracks and/or fractures during installation, use or de-installation. Here too, the inventors were able to complete 25000 revolutions of the castor chair test (EN425) without cracks or fractures occurring. Without these features, cracks were already found before 10000 revolutions were completed. The above data relate to a panel with a substrate of filled plastic, namely filled PVC, obtained by extrusion and with a filling ratio of more than 3:1 (filler:plastic), namely a filling ratio of approx. 4:1, and a thickness of about 5 mm, but the inventors have also found noteworthy improvements in similar tests with thinner filled plastic substrates, and with wood fiber substrates. The inventors attribute the good results to the optimization of the thicknesses as stated in the second aspect. These thicknesses lead namely to optimal support of the coupling parts in the vertical direction. The upper lip and the lower lip are massive enough to limit the movement of the tongue, and the tongue is massive enough to bend only minimally.

It is to be noted that the panel of the second independent aspect may optionally have the characteristic features of the first aspect and/or the preferred embodiments thereof. Additional resistance to cracking or fractures is then obtained in the coupling parts.

Preferably the thickness of the projecting portion of the lower lip decreases continuously in the distal direction up to the position with the aforementioned smallest thickness. This profile of the lower lip leads to minimization of possible bending stresses in the lower lip during coupling, uncoupling and/or in the coupled state and thus to a decreased risk of the development of cracks or fractures.

Preferably the aforementioned smallest thickness of the lower lip is manifested during or just before abutment of the upper side of the lower lip to the aforementioned upright locking element. In this way the strength of the lower lip is further optimized.

Preferably the horizontal distance of the position with the aforementioned smallest thickness of the lower lip from the distal end of the upper lip is at least 50%, or 75% or more of the distance by which the lower lip projects beyond the upper lip.

Preferably, in the aforementioned coupled state there is a space between the upper side of the lower lip and the underside of the tongue. Said space may have one or more of the following optional features.

According to a first optional feature, the aforementioned space may at least be present at the location of the position with the aforementioned smallest thickness.

According to a second optional feature the aforementioned space is present continuously from a position vertically under the distal end of the upper lip at least up to the position with the aforementioned smallest thickness. Said space avoids additional compressive stresses on the lower lip in the coupled state, even when for example owing to machining tolerances the profile of the lower lip or of the underside of the tongue would move somewhat.

According to a third optional feature, the aforementioned space has, at least over 80% of the distance over which the space extends in the horizontal direction, an almost constant vertical dimension, wherein this vertical dimension displays, over the respective distance, if it varies, a variation of less than 10%, or even of 5% or less. This constant or slightly varying space may, in production, easily be converted to a space with a small vertical dimension, in such a way that the thickness of the lower and upper lip and the tongue can be maximized.

Preferably, in the aforementioned coupled state, a contact surface is formed between the aforementioned upright locking element and the aforementioned downward directed locking element, wherein this contact surface has a tangent increasing in the distal direction of the lower lip, said tangent making an angle of at least 45°, or at least 47.5° to 65° with the horizontal. Preferably the position with the aforementioned smallest thickness is located at a distance from the center of the aforementioned contact surface, wherein this distance is less than 20% of the thickness of the panel, or is 10% or less of this thickness. The strength of the lower lip is also maximized in this embodiment. According to another embodiment, or in combination therewith, the center of the aforementioned contact surface is located at a horizontal distance from the distal end of the upper lip that is greater than 50% of the thickness of the panel, or is 60% of the thickness of the panel or more. In this way the possibility of taking the coupling parts apart by means of a rolling motion is improved.

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

Preferably the panel has a substrate and a decorative top layer applied thereon. Without intending to be limiting, some possibilities for the substrate and the decorative top layer are enumerated below.

According to a first possibility, the substrate is a wood-based substrate, preferably a substrate that consists substantially of pressed and glued wood particles. For example, the substrate comprises a wood fiberboard, preferably comprises an MDF or an HDF board, a chipboard or a plywood. The substrate of this first possibility preferably has an internal bond strength of less than 1.3 N/mm², preferably of less than 1.2 N/mm², more preferably of less than 1.1 N/mm², or even less than 0.85 N/mm². This internal bond strength is preferably measured in accordance with EN 319:1996. According to the most preferred embodiment of this first possibility the substrate is an HDF board, namely a wood fiberboard with a density of 800 kg/m³ or more, a thickness of 8 mm or more, and an internal bond strength measured according to EN 319:1996 of 1.2 N/mm² or less. It is to be noted that HDF boards usually employed for floors have an internal bond strength of 1.5 N/mm² or more. However, the present invention also allows good results to be obtained with boards of lower quality. According to another preferred embodiment of this first possibility the substrate is a wood fiberboard 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 to be noted that HDF boards usually employed for floors have a density of more than 800 kg/m³. However, the present invention also allows good results to be obtained with wood fiberboards of lower density.

According to a second possibility, the substrate is a, preferably filled, plastic substrate, preferably a substrate that comprises a thermoplastic, such as polyvinyl chloride, polyethylene terephthalate, polyethylene or polypropylene. Herein, the substrate may be a foamed plastic substrate, wherein, preferably, the upward directed locking element or upright locking element, depending on whether it relates to an embodiment of the first aspect or of the second aspect respectively, is made mainly or completely in a foamed portion of the substrate and/or a substrate that comprises inorganic or mineral fillers, wherein the upward directed locking element or upright locking element, depending on whether it relates to an embodiment of the first aspect or of the second aspect respectively, is made mainly or completely in a portion of the substrate that consists at least to 50 wt %, or at least to 65 wt %, or at least to 80 wt %, of the aforementioned fillers. The invention, either according to the first aspect or the second aspect or both, provides in each case an optimal strength, cracking and breaking resistance of said coupling parts despite being made partially in a weakened, for example foamed and/or filled, portion of the substrate.

The panel of the second possibility may have been obtained by extrusion of plastic. In that case the substrate may have a filling ratio of 3:1 (fillers:plastic) or more, for example of 4:1 or more.

In both the aforementioned first possibility and in the aforementioned second possibility or in general, the aforementioned decorative top layer may comprise a print, preferably a print made on the substrate optionally with intermediate preparatory layers, a print that is located on a layer of paper, wherein the layer of paper may be impregnated with resin, for example impregnated with melamine resin or with an acrylate resin, or a print that is located on a polymer film, thus preferably working with a printed polyvinyl chloride film.

In both the aforementioned first possibility and in the aforementioned second possibility or in general, the aforementioned decorative top layer may comprise a transparent or translucent wear layer, wherein the wear layer comprises one or more of

• • a polymer film, for example a polyvinyl chloride film;
  • a layer of paper impregnated with resin, for example with melamine resin or with an acrylate resin; and/or
  • a varnish coat, preferably an acrylate layer.The wear layer may comprise particles that increase the abrasion resistance of the wear layer, for example wherein these particles are corundum particles.

The invention also relates to a panel, wherein this panel has at least one first pair of opposite edges with coupling parts, wherein the aforementioned coupling parts allow two such panels to be coupled together, wherein in the coupled state locking is obtained on the respective edges both in a horizontal direction in the plane of the panels and perpendicular to the respective edges, and in a vertical direction transverse to the plane of the panels, wherein the coupling parts are configured substantially as a tongue and a groove delimited by means of a lower lip and an upper lip, wherein the aforementioned tongue and groove are provided with locking elements that prevent the tongue and the groove moving apart and wherein the aforementioned locking elements comprise an upright locking element on the aforementioned lower lip and, interacting therewith, a downward directed locking element on the underside of the tongue, wherein in the aforementioned coupled state a contact surface is formed between the upper side of the aforementioned tongue and the underside of the aforementioned upper lip, characterized in that the panel comprises one or more of the following characteristic features, so long as these are not contradictory:

• • the largest thickness of the aforementioned upper lip at the location of the aforementioned contact surface is equal, or is almost equal, to the smallest thickness of the aforementioned lower lip and/or wherein the ratio of the smallest thickness of the aforementioned lower lip to the largest thickness of the aforementioned upper lip is at least 1.1, preferably at least 1.2, and/or is at most 1.5, preferably at most 1.4;
  • the smallest thickness of the portion of the lower lip, proximal to the upright locking portion, is located at a distal position of the upper lip, or, in other words, in the portion of the lower lip that extends beyond the upper lip or, in yet other words, in the projecting portion of the lower lip;
  • the sum of the aforementioned largest thickness of the upper lip, the smallest thickness of the lower lip and the largest thickness of the tongue at the location of the aforementioned contact surface is less than, but is almost equal to the thickness of the panel, and/or wherein between the aforementioned sum and the thickness of the panel there is less than 10%, or even 5% of the thickness of the panel or less, excluding an optional glued-on sublayer;
  • the largest thickness of the tongue at the location of the aforementioned contact surface is less than the smallest thickness of the lower lip, preferably wherein the largest thickness of the tongue at the location of the aforementioned contact surface is at most 70% of the smallest thickness of the lower lip, preferably at most 60%;
  • the largest thickness of the tongue at the location of the aforementioned contact surface is less than the largest thickness of the upper lip, preferably wherein the largest thickness of the tongue at the location of the aforementioned contact surface is at most 80% of the largest thickness of the upper lip, preferably at most 70%.All embodiments of the second aspect are also applicable to this last-mentioned panel according to the invention, so long as this is not contradictory. This panel may for example have a total thickness, excluding an optional glued-on sublayer, of approximately 3.5 mm, wherein the largest thickness of the aforementioned upper lip at the location of the aforementioned contact surface is between 1.2 and 1.3 mm, wherein the largest thickness of the tongue at the location of the aforementioned contact surface is between 0.65 and 0.85 mm and wherein the smallest thickness of the aforementioned lower lip is between 1.4 and 1.5 mm.

For better illustration of the features of the invention, some preferred embodiments are described hereunder, as examples without any limiting character, referring to the appended drawings, in which:

FIG. 1 shows, in perspective, a step in the installation of a floor covering based on panels with the characteristic features of the first aspect of the invention;

FIG. 2 shows, on a larger scale, a view of the region that is indicated with F2 in FIG. 1;

FIG. 3 shows a top view of a panel from FIGS. 1 and 2;

FIG. 4 shows, on a larger scale, a cross section according to the line IV-IV shown in FIG. 3;

FIG. 5 shows, on an even larger scale, the coupled state of the coupling parts shown in FIG. 4;

FIG. 6 shows, on the same scale as FIG. 4, a cross section according to the line VI-VI shown in FIG. 3;

FIG. 7 shows, on the same scale as FIG. 5, the coupled state of the coupling parts shown in FIG. 6;

FIGS. 8 to 11 show variants in a view similar to that of FIG. 5, but on a smaller scale;

FIG. 12 shows, on a larger scale, a view of the region that is indicated with F12 in FIG. 5;

FIG. 13 shows a variant, in a similar view; and

FIG. 14 shows, in a view similar to that in FIG. 7, a panel with the characteristic features of the second aspect of the invention;

FIG. 15 shows, in a view similar to that in FIG. 14, a panel with characteristic features of the second aspect of the invention.

FIG. 1 shows, schematically and in perspective, a portion of a floor covering that consists of panels 1, more particularly floor panels 1, according to the invention.

FIG. 2 clearly shows that the panels 1 of this example are configured on their edges in such a way that they are couplable together according to the so-called fold-down principle.

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

Installation by the fold-down principle, as shown in FIG. 2, consists in that said floor panels 1 are couplable together on the long pair of opposite edges 2-3 by a rolling motion W, and are couplable together on the short pair of edges 4-5 by a downward motion M, wherein the downward motion M is a consequence of the rolling motion W and thus occurs substantially simultaneously. The floor panels 1 are, in this case, also configured on their edges 2-3 and 4-5 in such a way that finally locking is brought about in the vertical direction V perpendicular to the plane of the coupled panels 1, as well as in the horizontal direction H1-H2. The latter is in each case perpendicular to the respective relevant edges 2-3; 4-5 and in the plane of the coupled panels 1.

FIG. 4 shows that the coupling parts 6 comprise, on the short pair of opposite edges 4-5, a horizontally acting locking system 8, which, in the coupled state, shown in FIG. 5, achieves the locking in the aforementioned horizontal direction H2. The coupling parts 6 further comprise a vertically acting locking system 9 which, in the coupled state, shown in FIG. 5, achieves the locking in the aforementioned vertical direction V. The horizontally acting locking system 8 comprises a projecting lip 10 with an upward directed locking element 11 on the underside of the panel 1. The upward directed locking element 11 abuts against the proximally located upper side 12 of the aforementioned projecting 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 an optional glued-on sublayer 14. The thickness of the optional glued-on sublayer 14 is not included, since this makes little or no contribution to the material properties of the actual substrate 15.

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

The horizontally acting locking system 8 comprises, on the opposite edge 5, a downward directed locking element 16, which in the aforementioned coupled state comes or may come into contact with the aforementioned upward directed locking element 11. In the example the aforementioned contact extends over a contact surface 17 that is completely within the lowest 65% of the total height H over which the upward directed locking element extends relative to the aforementioned proximally located upper side 14 of the projecting lip 10.

The aforementioned contact or the contact surface 17 is on the one hand formed on a surface of the downward directed locking element 16, which, measured in the proximal direction of the panel 1, makes a first angle A with the underside of the panel 1 of less than 80°, and, in this case, an angle of less than 65°, namely about 62°. On the other hand, the aforementioned contact or the contact surface 17 is, in the example, formed on a surface of the upward directed locking element 11, which, measured in the distal direction, makes a second angle B with the underside of the panel 1, wherein this second angle B is, in this case, greater than the aforementioned first angle A. In the example, the difference between the first angle A and the second angle B is about 3°.

It is clear that proximally to the upward directed locking element 11 there is a female part 18, wherein the aforementioned downward directed locking element 16 forms a male part 19, wherein in the aforementioned coupled state the male part 19 is fitted in the female part 18.

The vertically acting locking system 9 comprises a first locking part 20 and a second locking part 21 interacting therewith. The first locking part 20 is located at the distal end of the downward directed locking element 16 and the second locking part 21 is located at the proximal end of the female part 18.

According to the example, in the coupled state as shown in FIG. 5, the first locking part 20 and the second locking part 21 form a contact surface whose tangent T makes an angle C with the plane of the panel of at least 15°, in this case of about 20°, wherein this tangent T increases in the distal direction of the female part 18.

It is clear that, in the example in FIGS. 1 to 5, the first locking part 20 comprises a horizontal projecting component of the downward directed locking element 16 and the second locking part 21 comprises an undercut. In the aforementioned coupled state, abutting or practically abutting sealing faces 22 are formed on the upper edges of the second or short pair of opposite edges. In the example the sealing faces 22 are substantially perpendicular to the plane of the panel, wherein the edge 5 with the female coupling part 18 does not comprise, above the aforementioned second locking part 21, any components that, in the horizontal direction, project outside the aforementioned sealing face 22.

FIGS. 4 and 5 further show that the aforementioned projecting lip 10 comprises a recess 23 on the underside from the distal end of the projecting lip 10, wherein this recess extends in the proximal direction to beyond the upward directed locking element 11. Under 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 about 5% of the total thickness T of the panel, excluding an optional glued-on sublayer 14. Embodiments are not shown in panels with a thickness T of 9 mm or more, wherein the height H3 is preferably at least 10% of the thickness T. Panels of this kind preferably consist of wood fiberboard.

The aforementioned vertical locking system 9, in the example in FIGS. 1 to 5, further comprises at the distal end of the upward directed locking element 11 or at the distal end of the projecting lip 10, a locking part 24 that interacts with a locking part 25 on the opposite edge 4 of the panel 1 coupled therewith.

FIGS. 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 horizontally acting locking system 8 and a vertically acting locking system 9. The horizontally acting locking system 8 comprises, also in this case, a projecting lip 10 with an upward directed locking element 11 on the underside of the panel 1. The upward directed locking element 11 abuts against the proximally located upper side 12 of the aforementioned projecting 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 an optional glued-on sublayer 14.

On the long edge 2 opposite the long edge 3 with the projecting lip 10, the coupling part 6 comprises a tongue 26. The tongue 26 comprises, on its underside, the downward directed locking element 16. The aforementioned projecting lip 10 is the lower lip of a groove 27, which is delimited upward by an upper lip 28. In the example, the lower lip or projecting lip 10 projects farther than the upper lip 28, wherein the interaction of the aforementioned tongue 26 and groove 27 in the aforementioned coupled state brings about locking in the direction V perpendicular to the coupled panels 1, or wherein, in other words, the aforementioned tongue 26 and groove 27 form part of the aforementioned vertical locking system 9.

As shown in FIG. 6, the tongue 26 of a first such panel 1, may be brought, selectively, by means of a rolling motion W or by means of a substantially horizontal sliding motion S, optionally with a snap effect, into the groove 27 of a second such panel 1, wherein coupling is obtained between the first such panel 1 and the second such panel 1.

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 may also have coupling parts that comprise a tongue and groove, wherein the groove is delimited by a lower lip and an upper lip, preferably wherein the lower lip projects farther than the upper lip, wherein in the coupled state the tongue and the groove provide locking in the direction perpendicular to the coupled panels, wherein the lower lip comprises an upright locking element, wherein the underside of the tongue comprises a locking element, wherein in the coupled state, the upright locking element together with the locking element on the underside of the tongue provides locking in the direction perpendicular to these coupled edges and in the plane of the panels, without the upper side of the lower lip necessarily abutting against the upright locking element by means of a concave surface, as stated in the context of the first aspect of the invention.

It is to be noted that coupling parts identical or similar to the coupling parts 6 as shown in FIGS. 4 and 5, according to a variant, may also be applied on 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 FIGS. 6 and 7 may also be applied on the short pair of opposite edges 4-5.

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

FIG. 8 shows a variant, for example for the coupling parts 6 on the short pair of opposite edges 4-5, wherein the aforementioned first locking part 20 is formed by or on a separate insert 29 that is applied in the respective edge 4, in this case the edge 4 with the downward directed locking element 16, or male coupling part.

FIG. 9 shows another variant, for example for the coupling parts 6 on the short pair of opposite edges 4-5, wherein the aforementioned second locking part 21 is formed by or on a separate insert 29 that is applied in the respective edge 5, in this case the edge 5 with the upward directed locking element 11, or the edge 5 with the female coupling part 18.

The embodiments shown in FIGS. 8 and 9 otherwise have similar characteristic features as the coupling parts 6 from FIGS. 4 and 5, but wherein the distal end of the projecting lip 10 is free from locking parts. Thus, for example the concave surface 13 has identical characteristic features at the location of the abutment of the upward directed locking element 11 on the proximally located upper side 12 of the projecting lip 10.

FIGS. 10 and 11 show in each case another variant, for example for the coupling parts 6 on the short pair of opposite edges 4-5. Herein, the coupling parts 6 are made from the material of the panel 1, more particularly of the substrate 15.

FIG. 10 displays substantially similar characteristic features as the coupling parts 6 shown in FIGS. 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 about 100°:
  • the distal end of the projecting lip 10 is free from locking elements. In other words the vertical locking system 9 comprises exclusively locking parts on the distal and proximal side of the downward directed locking element 16, and locking parts on the opposite edge 5 interacting therewith.

FIG. 11 displays substantially similar characteristic features as the coupling parts 6 shown in FIGS. 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 about 95°:
  • the proximal end of the female coupling part 18 is free from locking elements. In other words the vertical locking system 9 comprises exclusively locking parts on the distal and proximal side of the upward directed locking element 11, and locking parts on the opposite edge 4 interacting therewith.

FIGS. 4, 5, 9 and 11 further have the feature that the downward directed locking element 16 extends deeper in the proximal half thereof than in the distal half thereof.

FIG. 12 again shows the concave surface 13 as is applied in the embodiment in FIGS. 4 and 5, and may be applied in the other embodiments. FIG. 12 clearly shows that, in the coupled state, at the location of the concave surface 13 there is preferably a space 30 between the concave surface and the downward directed locking element 16. This space 30 preferably abuts on at least 80% of the concave surface 13, and better still over the whole, or almost the whole concave surface 13.

As already mentioned, the aforementioned contact extends over a contact surface 17 that is completely within the lowest 65% of the total height H over which the upward directed locking element 11 extends relative to the aforementioned proximally located upper side 14 of the projecting lip 10.

It is clear that the aforementioned proximally located upper side 12 of the projecting lip 10, in this case, comprises a portion that extends horizontally or approximately horizontally to the aforementioned abutment or transition to the upward directed locking element 11. In general the concave surface 13 is preferably seen as extending from a first point 31 where the upper side 12 of the projecting lip 10 deviates from the horizontal. In the case when the proximally located upper side 12 of the projecting lip 10 has a direction that per se deviates preferably less than 10° from the horizontal, the first point 31 is located at the position where the upper surface of the projecting lip 10 deviates further still from the horizontal. Furthermore, the concave surface 13 is preferably seen as extending to a second point 32 wherein the upper surface of the projecting lip 10 abuts with and has the same direction as the contact surface 17.

The aforementioned space 30 preferably extends at least between the aforementioned first point 31 and the aforementioned second point 32.

In general, the aforementioned concave surface 13 may further display one or more of the following properties:

• • the property that the concave surface 13 extends in the horizontal direction H2 over a distance HE that is greater than the distance VE over which the concave surface 13 extends in the vertical direction V. Preferably the ratio HE:VE is between 1.65:1 and 1.2:1;
  • the property that the concave surface 13 extends over a horizontal distance HE that is greater than 40% of the height H of the upward directed locking element 11;
  • the property that the concave surface 13 extends over a horizontal distance HE that is less than 65% of the height H of the upward directed 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 directed locking element 11.

FIG. 13 shows another variant wherein the concave surface 13A is formed by a facetted surface, namely a concave surface 13A formed by two planes 33-34 that enclose an angle D of at least 105°, and preferably at least 110°. In this case the angle D is about 150°. Otherwise the variant in FIG. 13 has the same characteristic features as FIG. 12. It is clear that this variant may be applied in any embodiment of the first aspect of the invention, for example in the embodiments in FIGS. 1 to 11.

FIG. 14 shows an embodiment with the characteristic features of the second independent aspect of the invention stated in the introduction. This relates to a floor panel in which coupling parts 6 are used that are configured substantially as a tongue 26 and a groove 27 delimited by means of a lower projecting lip 10 and an upper lip 28. The aforementioned tongue 26 and groove 27 are provided with locking elements 11-16, which prevent the tongue 26 and groove 27 moving apart and wherein the aforementioned locking elements comprise an upright locking element 11 on the aforementioned lower lip 10 and a downward directed locking element 16, interacting therewith, on the underside of the tongue 26. The aforementioned tongue 26 and groove 27 form per se the vertically acting locking system 9, whereas the locking elements 11-16 form the horizontally acting locking system 8.

In the coupled state, as shown in FIG. 14, a contact surface 35 is formed between the upper side of the aforementioned tongue 26 and the underside of the aforementioned upper lip 28. Herein, the largest thickness DU of the aforementioned upper lip 28 at the location of the aforementioned contact surface 35 is approximately equal to the smallest thickness DL of the aforementioned lower lip 10. Herein, the difference in thickness there is less than 10%, or even 5% of the thickness of the panel or less, excluding an optional glued-on sublayer. In this case the smaller of the thicknesses DU and DL is more than 90% of the larger of the thicknesses DU and DL.

The smallest thickness DL of the portion of the lower lip 10, proximal to the upright 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 that extends beyond the upper lip 28 or, in yet other words, in the projecting portion of the lower lip 10. In the example the lower lip 10 comprises a zone 36 that 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 upper side 12 of the projecting lip 10 deviates from the horizontal.

The sum of the aforementioned largest thickness DU of the upper lip 28, the smallest thickness DL of the lower lip 10 and the largest thickness DT of the tongue 26 at the location of the aforementioned contact surface 35 is less than, but approximately equal to the thickness T of the panel 1. In this case the difference between the aforementioned sum and the thickness T of the panel is less than 10%, namely about 7.5%.

FIG. 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 with the aforementioned smallest thickness DL. The aforementioned smallest thickness DL of the lower lip 10 is manifested at the abutment of the upper side 12 of the lower lip 10 with the aforementioned upright locking element 11. The horizontal distance HD of the most distal position with the aforementioned smallest thickness DL from the lower lip 10 to the distal end of the upper lip 28 is at least 50% of the distance HL by which the lower lip 10 projects beyond the upper lip 28.

In the example, in the aforementioned coupled state there is a space 30 between the upper side 12 of the lower lip 10 and the underside of the tongue 26. The aforementioned space 30 is at least present at the location of the distal position with the aforementioned smallest thickness DL. Preferably the aforementioned space 30 extends abutting on the whole zone 36 that has the aforementioned smallest thickness DL.

The aforementioned space 30 is continuously present from a position 39 vertically below the distal end of the upper lip 28 to at least the proximal position 37, and preferably at least to the distal position 38 of the zone 36 with the aforementioned smallest thickness DL. Preferably the aforementioned space 30 has, such as here, an almost constant vertical dimension VS at least over 80% of the distance over which the space 30 extends in the horizontal direction H1. Preferably the aforementioned vertical dimension VS varies, over the distance from the position 39 under the distal end of the upper lip 28 to the proximal position 37 of the aforementioned zone 36, less than 10% of the largest distance VS in this distance, or even 5% or less of this largest distance VS.

FIG. 14 further shows that, in the present case, in the coupled state a contact surface 17 is formed between the aforementioned upright locking element 11 and the aforementioned downward directed locking element 16, wherein this contact surface 17 has a tangent increasing in the distal direction of the lower lip 10, said tangent making an angle A from 47.5 to 65° with the horizontal. Herein, the distal position 38 of the zone 36 with the aforementioned smallest thickness DL is located at a distance from the center 40 of the aforementioned contact surface 17 that is less than 20% of the thickness T of the panel 1, or is 10% of this thickness T or less.

In the embodiment in FIG. 14, the center 40 of the aforementioned contact surface 17 is located at a horizontal distance HC from the distal end of the upper lip 28 that 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 characteristic features of the second independent aspect of the invention, such as coupling parts 6 shown in FIG. 14, may be used on any pair of opposite edges 2-3-4-5, either on the long pair of edges 2-3, or on the short pair of edges 2-3-4-5, or on both. If said coupling parts 6 are only used on the long pair of edges 2-3, it is possible to apply coupling parts 6 on the short pair of edges 4-5 to allow coupling by means of a downward motion M, such as coupling parts 6 shown in FIGS. 4, 5 and 8 to 13, or similar. If said coupling parts 6 are only applied on the long pair of edges 2-3, it is also possible to apply coupling parts 6 on the short pair of edges 4-5, to allow coupling by means of a rolling motion W and/or a horizontal sliding motion S, such as coupling parts 6 shown in FIGS. 6 and 7 or similar.

In connection with all figures, it is noted further that the panels from the examples in each case have a substrate 15 and a decorative top layer 41 applied thereon. In the embodiments in FIGS. 1 to 13 this preferably relates to a wood-based substrate 15, preferably a substrate that consists substantially of pressed and glued wood particles, such as an MDF or an HDF board. This may relate to a substrate 15 with an internal bond strength of less than 1.3 N/mm². In the case of FIG. 14 it is preferably a filled plastic substrate, preferably a substrate that comprises a thermoplastic, such as polyvinyl chloride, polyethylene terephthalate, polyethylene or polypropylene. As is the case in FIG. 14, the substrate 15 preferably comprises inorganic or mineral fillers, wherein the upright locking element 11 is made mainly or completely in a portion of the substrate 15 that consists at least to 50 wt %, or at least to 65 wt %, or at least to 80 wt %, of the aforementioned fillers. The substrate 15 is herein preferably at least obtained by plastics extrusion.

In the case of FIGS. 1 to 13, the aforementioned decorative top layer 41 comprises a print that is located on a layer of paper, wherein the layer of paper is impregnated with melamine resin. In the case of FIG. 14, the aforementioned decorative top layer 41 comprises a print that is located on a polymer film, in this case a printed polyvinyl chloride film.

In connection with FIG. 14, it is further noted that the lowered edge regions 42, which are shown there, are entirely optional. In addition, said lowered edge regions 42 are optional in any embodiment of the present invention according to its first and/or second independent aspect. If present, they do not necessarily, as in FIG. 14, have to extend into the substrate 15, but they may be limited to the thickness of the top layer 14, or to the thickness of an optional wear layer. In the example in FIG. 14, the lowered edge regions 42 are formed as chamfers. This too is not essential and lowered edge regions with a horizontal or almost horizontal bottom are also possible. Moreover, said lowered edge region 42, such as in the case of FIG. 14, may be obtained by removing a portion of material on the upper edge. In this case, the surface obtained may be provided with separate decoration. According to another possibility, a lowered edge region may for example be obtained by deforming the upper edge and/or the substrate 15. In that case, it is possible that the decorative top layer 41 extends continuously from the overall upper surface of the panel 1 up to and over the surface of the lowered edge region 42, preferably up to the sealing face 22.

The present invention is by no means limited to the embodiments described above, but panels of this kind may be produced according to many variants while remaining within the scope of the present invention.

Claims

1.-48. (canceled)

49. A panel, wherein this panel has at least one first pair of opposite edges with coupling parts, wherein the aforementioned coupling parts allow two such panels to be couplable together and further have the following characteristic features:the coupling parts comprise a horizontally acting locking system, which in a coupled state of two such panels achieve locking in the plane of the panels and perpendicular to the respective edges;the coupling parts also comprise a vertically acting locking system, which in a coupled state of two such panels achieve locking transverse to the plane of the panels;wherein the horizontally acting locking system comprises a projecting lip with an upward directed locking element on the underside of the panel,wherein the upward directed locking element abuts against the proximally located upper side of the aforementioned projecting lip at least by means of a curved concave surface with a radius of at least 0.7 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 an optional glued-on sublayer; and/or by means of a concave surface formed by two planes that enclose an angle of at least 105°.

50. The panel as in claim 49, wherein the horizontally acting locking system comprises, on the opposite edge, a downward directed locking element, which in the aforementioned coupled state comes or may come into contact with the aforementioned upward directed locking element.

51. The panel as in claim 50, wherein the aforementioned contact extends over a contact surface that is located completely in the lowest 65% of the total height over which the upward directed locking element extends relative to the aforementioned proximally located upper side of the projecting lip.

52. The panel as in claim 50, wherein the downward directed locking element extends deeper in the proximal half thereof than in the distal half thereof, wherein the difference in depth is at least 0.20 mm.

53. The panel as in claim 49, wherein the aforementioned coupled state the projecting lip is bent out downward.

54. The panel as in claim 50, wherein the coupling part comprises a tongue on the aforementioned opposite edge, wherein the tongue comprises the downward directed locking element on its underside,wherein the aforementioned projecting lip is the lower lip of a groove, which is delimited upward by an upper lip,wherein the interaction of the aforementioned tongue and groove in the aforementioned coupled state brings about locking in the direction perpendicular to the coupled panels, orwherein, in other words, the aforementioned tongue and groove form part of the aforementioned vertical locking system,wherein the tongue of a first such panel may be brought by means of a turning motion and/or by means of a substantially horizontal sliding motion, into the groove of a second such panel, wherein coupling is obtained between the first such panel and the second such panel.

55. The panel as in claim 49, wherein the aforementioned projecting lip comprises a recess on the underside from the distal end of the lower lip.

56. The panel as in claim 55, wherein the aforementioned recess has, vertically under the aforementioned, whether or not curved, concave surface, a height, measured perpendicular to the plane of the panel, of at least 10% of the total thickness of the panel.

57. A panel, wherein this panel has at least one first pair of opposite edges with coupling parts, wherein the aforementioned coupling parts allow two such panels to be couplable together,wherein in the coupled state locking is obtained on the respective edges both in a horizontal direction in the plane of the panels and perpendicular to the respective edges and in a vertical direction transverse to the plane of the panels,wherein the coupling parts are configured substantially as a tongue and a groove delimited by means of a lower lip and an upper lip,wherein the aforementioned tongue and groove are provided with locking elements that prevent the tongue and groove moving apart andwherein the aforementioned locking elements comprise an upright locking element on the aforementioned lower lip and, interacting therewith, the downward directed locking element on the underside of the tongue,wherein in the aforementioned coupled state a contact surface is formed between the upper side of the aforementioned tongue and the underside of the aforementioned upper lip, whereinthe largest thickness of the aforementioned upper lip at the location of the aforementioned contact surface is equal, or is approximately equal, to the smallest thickness of the aforementioned lower lip and/orwherein the difference in thickness is less than 10%, or even 5% or less than the thickness of the panel, excluding an optional glued-on sublayer; and/orwherein the smaller of the aforementioned thicknesses of the lower lip and upper lip is at least 90% of the larger of the aforementioned thicknesses;the smallest thickness of the portion of the lower lip, proximal to the upright locking portion, is located at a distal position of the upper lip, or, in other words, in the portion of the lower lip that extends beyond the upper lip or, in yet other words, in the projecting portion of the lower lip;the sum of the aforementioned largest thickness of the upper lip, the smallest thickness of the lower lip and the largest thickness of the tongue at the location of the aforementioned contact surface is less than, but is almost equal to the thickness of the panel, and/orwherein between the aforementioned sum and the thickness of the panel there is less than 10%, or even 5% or less of the thickness of the panel, excluding an optional glued-on sublayer.

58. The panel as in claim 57, wherein the thickness of the projecting portion of the lower lip decreases continuously in the distal direction to the proximal position with the aforementioned smallest thickness.

59. The panel as in claim 57, wherein the aforementioned smallest thickness of the lower lip is manifested at or just before the abutment of the upper side of the lower lip with the aforementioned upright locking element.

60. The panel as in claim 57, wherein the horizontal distance of the distal position with the aforementioned smallest thickness from the lower lip to the distal end of the upper lip is at least 50%, or 75% or more of the distance by which the lower lip projects beyond the upper lip.

61. The panel as in claim 57, wherein in the aforementioned coupled state a space is present between the upper side of the lower lip and the underside of the tongue.

62. The panel as in claim 61, wherein the aforementioned space at least is present at the location of the zone or position with the aforementioned smallest thickness.

63. The panel as in claim 61, wherein the aforementioned space is present continuously from a position vertically under the distal end of the upper lip at least to the proximal position with the aforementioned smallest thickness.

64. The panel as in claim 61, wherein the aforementioned space, at least over 80% of the distance over which the space extends in the horizontal direction, has an almost constant vertical dimension, wherein this vertical dimension has, over the respective distance, if it varies, a variation of less than 10%, or even of 5% or less, and/orwherein this vertical dimension, over the distance between the position vertically under the distal end of the upper lip and the proximal position with the aforementioned smallest thickness, if it varies, displays a variation of less than 10%, or even of 5% or less.

65. The panel as in claim 57, wherein in the aforementioned coupled state a contact surface is formed between the aforementioned upright locking element and the aforementioned downward directed locking element, wherein this contact surface has a tangent increasing in the distal direction of the lower lip, said tangent making an angle from 47.5 to 65° with the horizontal.

66. The panel as in claim 65, wherein the distal position with the aforementioned smallest thickness is located at a distance from the center of the aforementioned contact surface, wherein this distance is less than 20% of the thickness of the panel, or is 10% or less of this thickness.

67. The panel as in claim 65, wherein the center of the aforementioned contact surface is located at a horizontal distance from the distal end of the upper lip that is greater than 50% of the thickness of the panel, or is 60% or more of the thickness of the panel.

68. A panel, wherein this panel has at least one first pair of opposite edges with coupling parts, wherein the aforementioned coupling parts allow two such panels to be couplable together,wherein in the coupled state, locking is obtained on the respective edges both in a horizontal direction in the plane of the panels and perpendicular to the respective edges, and in a vertical direction transverse to the plane of the panels,wherein the coupling parts are substantially configured as a tongue and a groove delimited by means of a lower lip and an upper lip,wherein the aforementioned tongue and groove are provided with locking elements that prevent the tongue and groove moving apart andwherein the aforementioned locking elements comprise an upright locking element on the aforementioned lower lip and, interacting therewith, a downward directed locking element on the underside of the tongue,wherein in the aforementioned coupled state a contact surface is formed between the upper side of the aforementioned tongue and the underside of the aforementioned upper lip,wherein the panel comprises one or more of the following characteristic features, so long as these are not contradictory:the largest thickness of the aforementioned upper lip at the location of the aforementioned contact surface is equal, or is approximately equal, to the smallest thickness of the aforementioned lower lip and/orwherein the ratio of the smallest thickness of the aforementioned lower lip to the largest thickness of the aforementioned upper lip is at least 1.1, and/or is at most 1.5;the smallest thickness of the portion of the lower lip, proximal to the upright locking portion, is located at a distal position of the upper lip, or, in other words, in the portion of the lower lip that extends beyond the upper lip or, in yet other words, in the projecting portion of the lower lip;the sum of the aforementioned largest thickness of the upper lip, the smallest thickness of the lower lip and the largest thickness of the tongue at the location of the aforementioned contact surface is less than, but is almost equal to, the thickness of the panel, and/orwherein between the aforementioned sum and the thickness of the panel there is less than 10%, or even 5% or less of the thickness of the panel, excluding an optional glued-on sublayer;the largest thickness of the tongue at the location of the aforementioned contact surface is less than the smallest thickness of the lower lip;the largest thickness of the tongue at the location of the aforementioned contact surface is less than the largest thickness of the upper lip.