Set of panels and covering composed of said set of panels

Abstract

The invention relates to a set of panels, in particular decorative panels, such as decorative floor panels or decorative wall panels. The invention also relates to a covering, in particular a decorative covering, such as a decorative floor covering or decorative wall covering, comprising a plurality of interconnected panels of the set of panels according to the invention.

Description

[0001] Set of panels and covering composed of said set of panels

[0002] The invention relates to a set of panels, in particular decorative panels, such as decorative floor panels or decorative wall panels. The invention also relates to a covering, in particular a decorative covering, such as a decorative floor covering or decorative wall covering, comprising a plurality of interconnected panels of the set of panels according to the invention.

[0003] Interconnectable panels, such as interconnectable floor panels, are generally joined mechanically at edges of the panels by using complementary coupling parts at opposite edges. Traditionally, rectangular floor panels are connected at the long edges by means of a traditional angling method. On the short side, the different coupling mechanisms can be applied, wherein a short edge coupling mechanism may, for example, be based upon vertical folding, also referred to as a drop down, wherein a downward tongue located at a short edge of a panel to be coupled is moved in downward direction, such that said downward tongue is inserted into an upward groove located at a short edge of a panel already installed. An example of such a panel is disclosed in US7896571, wherein a short edge coupling mechanism is shown being configured to vertically lock mutually coupled short edges of adjacent panels. Although this aimed vertical locking effect at the short edges is intended to stabilize the coupling between floor panels at the short edges, in practice often breakages, due to coupling edges being put under tension both during assembly and during practical use, occur at the coupling edges, which affects the reliability and durability of this type of drop down coupling. Moreover, the known coupling mechanisms are less suitable for relatively thin panels.

[0004] An objective of the invention is to provide an improved set of panels which can be coupled in improved manner to each other.

[0005] Another objective of the invention is to provide an improved set of relatively thin panels which can be coupled in improved manner to each other.

[0006] Yet another objective of the invention is to provide an improved set of panels which can be coupled in a reliable predefined manner to each other.At least one of these objectives can be reached by providing a set of panels according to the preamble, wherein each panel comprises:

[0007] • at least one core layer,

[0008] • at least one optional first coupling part and at least one optional second coupling part provided at different panel edges, preferably a first pair of opposite panel edges,

[0009] wherein said optional first coupling part comprises:

[0010] o an upward tongue,

[0011] o at least one upward flank lying at a distance from the upward tongue, o an upward groove formed in between the upward tongue and the upward flank, wherein the upward groove is adapted to receive at least a part of a downward tongue of a second coupling part of an adjacent panel, and wherein the upward tongue is connected to the upward flank via a lower bridge, wherein a(n) - preferably substantially horizontal and / or planar - upper side (upper surface) of said lower bridge defines at least a part of a bottom surface of the upward groove configured to support said downward tongue of an adjacent panel, and

[0012] o at least one optional first locking element provided at a distal side of the upward tongue facing away from the upward flank, wherein said optional first locking element comprises at least one first contact surface,

[0013] o at least one fourth locking element provided at the upward flank, wherein said fourth locking element comprises at least one inclined fourth contact surface,

[0014] wherein said optional second coupling part comprises:

[0015] o a downward tongue having a lower surface or lower side, which lower surface or lower side is preferably at least partially planar and / or at least partially horizontal and / or inclined,

[0016] o at least one downward flank lying at a distance from the downward tongue, o a downward groove formed in between the downward tongue and the downward flank, wherein the downward groove is adapted to receive at least a part of an upward tongue of a first coupling part of an adjacent panel, o at least one optional second locking element provided at the downward flank, wherein said optional second locking element comprises at least one second contact surface configured to co-act with and / or face the first contact surface of an adjacent panel,o at least one third locking element provided at a distal side of the downward tongue facing away from the downward flank, wherein said third locking element comprises at least one inclined third contact surface configured to co-act with and / or face the fourth contact surface of an adjacent panel, wherein the third contact surface and the fourth contact surface are at least partially, preferably entirely, located below a horizontal plane (HP), parallel to a plane defined by the panel, defining a maximum height of the upward tongue, and wherein, in coupled state of adjacent panels,

[0017] - a proximal side of the upward tongue facing towards the upward flank coacts with a proximal side of the downward tongue facing the downward flank of an adjacent panel,

[0018] - the upper side or upper surface of said lower bridge supports a part of the lower side or lower surface of the downward tongue of the adjacent panel preferably at a lower contact zone, which lower contact zone is at least partially located closer the proximal side of the upward tongue than to the upward flank (or closer to the upward flank than to the proximal side of the upward tongue),

[0019] - at least a part of the upward flank co-acts with a part of a distal side of the downward tongue of the adjacent panel,

[0020] - the panels enclose at least one distal space between a distal side of the upward tongue and the facing downward flank,

[0021] - the panels enclose at least one intermediate space between the lower bridge and the facing downward tongue at least at a location closer to the proximal side of the upward tongue than to the upward flank, preferably at both sides of said lower contact zone, and

[0022] - the panels enclose at least one joint space between the upward flank and the distal side of the downward tongue,

[0023] wherein each panel further comprises at least one third coupling part and at least one fourth coupling part provided at different panel edges, preferably at a second pair of opposite panel edges, wherein said third coupling part and said fourth coupling part are configured to be coupled by means of a lateral snap-in movement,

[0024] wherein the fourth coupling part comprises:

[0025] • a sideward tongue extending in a direction substantially parallel to the upper side of the core layer,• at least one second downward flank lying at a distance from the sideward tongue, and

[0026] • a second downward groove formed between the sideward tongue and the second downward flank; and

[0027] wherein the third coupling part comprises a third groove configured for accommodating at least a part of the sideward tongue of the fourth coupling part of an adjacent panel, said third groove being defined by an upper lip and a lower lip, wherein said lower lip is provided with an upward locking element, wherein the third coupling part and fourth coupling part are preferably designed such that the fourth coupling part of a first panel can be positioned in an intermediate position with respect to the third coupling part of an adjacent panel, wherein, in said intermediate position, the planes defined by the panels in the intermediate state run in parallel, and wherein a lower side of the sideward tongue is supported by, preferably an upper side of, the upward locking element while a part of the sideward tongue is located within the third groove and below the upper lip, and

[0028] wherein, in coupled state of said third coupling part and said fourth coupling part of adjacent panels:

[0029] • at least a part of the sideward tongue is inserted into the third groove of an adjacent panel, and wherein at least a part of the upward locking element of said second panel is inserted into the second downward groove of said first panel,

[0030] • a proximal side of the upward locking element facing towards the third groove co-acts with a proximal side of the downward tongue facing the downward flank of an adjacent panel to prevent drifting apart of said panels,

[0031] • the upper side of said lower lip preferably supports a part of the lower side of the sideward tongue of an adjacent panel, at a lower contact zone which is preferably located adjacent to the proximal side of the upward locking element,

[0032] • at least a part of an end surface of the upper lip co-acts with a part of a distal side of the fourth coupling part of the adjacent panel, wherein, in coupled state of said third coupling part and said fourth coupling part, adjacent panels preferably enclose:

[0033] • at least one distal space between the distal side of the lower lip and a facing downward flank of the fourth coupling part,• at least one intermediate space between the upper side of the lower lip and the facing lower side of the sideward tongue at at least one side of said lower contact zone, and

[0034] • at least one joint space between the third coupling part, in particular the upper lip and / or the third groove, and a distal side of the sideward tongue.

[0035] In this manner, the third coupling part and the fourth coupling part are configured such that two of such panels can be coupled to each other by means of a predominantly lateral translational (linear) movement, wherein, in coupled state: at least a part of the sideward tongue of a first panel is inserted into the third groove of an adjacent, second panel, and wherein at least a part of the upward locking element of said second panel is inserted into the second downward groove of said first panel. This allows an easy installation of the panels, and is in particularly advantageous in case of narrow spaces, such as near a door sill for example, where there is a lack of space to seriously angle or tilt a panel to be installed during the installation process. Preferably, as indicated above, the third and fourth coupling parts are designed such that the fourth coupling part of a first panel can be positioned in an intermediate position with respect to the third coupling part of an adjacent panel, wherein the planes defined by the panels in the intermediate state run in parallel, and wherein a lower side of the sideward tongue is supported by an upper side of the upward locking element while a part of the sideward tongue is situated within the third groove and below the upper lip. In this intermediate state (intermediate position), which can be an initial state during the coupling process of coupling both panels, (a tip of) the sideward tongue preferably contacts a lower side of the upper lip, thereby defining front(al) contact surfaces. A front contact surface of the upper side of the sideward tongue configured to co-act with the lower lip in the intermediate positioned is preferably at least partially downwardly inclined towards a terminal portion of the sideward tongue. This inclined contact surface may be planar and / or curved, and is configured as sliding surface to slide the sideward tongue into the third groove. A front contact surface located at the lower side of the upper lip is preferably (also) downwardly inclined towards a terminal portion of the third groove. This inclined contact surface may be planar and / or curved, and is (also) configured as sliding surface to facilitate sliding the sideward tongue into the third groove. In the intermediate position, the shortest verticaldistance between the front contact surfaces and the rear contact surfaces (at the upward locking element) is preferably 20-30% of the panel thickness and / or between 0.8 and 1.5 mm. The vertical distance for displacing the fourth coupling part from the intermediate state into the coupled state is preferably 10-50% of the panel thickness and / or between 0.3 and 1.0 mm.

[0036] A proximal side of the upward locking element acts as locking surface configured to co-act with a rear side surface of the sideward tongue. This results in horizontal locking of the panel in coupled state. The upper side of the lower lip may have a deepened portion, which defines the lowest point or lowest zone, of the lower lip. This deepened portion is preferably situated directly adjacent to the upward locking element. The deepened portion is preferably configured to support the sideward tongue in the coupled state. The lower side of the sideward tongue may (also) have a deepened portion which defines the lowest point or lowest zone, of the sideward tongue. This deepened portion is preferably situated directly adjacent to the rear contact surface of the sideward tongue acting as locking surface. Preferably, the deepened portion is configured to be supported by the lower lip in the coupled state, more preferably by the deepened portion (if applied) of the sideward tongue. The width of the deepened portion of the lower lip preferably exceeds the width of the deepened portion of the sideward tongue to facilitate coupling of the panels.

[0037] As indicated above, the third coupling part and the fourth coupling part can be configured such that two of such panels can be coupled to each other by means of a predominantly lateral translational (linear) movement. However, during coupling a slight angling of the panel to be installed can be needed in order to achieve the coupled state. This slight angling is preferably limited to 10-15 degrees, preferably less than 10 degrees. This makes it possible to install panels even at location where there is a lack of space to more drastically (> 45 degrees) angle a panel into another panel, e.g. near a door sill (plate). In the coupled state of adjacent panels, the third coupling part, preferably only, co-acts with the fourth coupling part at spaced contact zones, wherein a first contact zone is located at a side surface of the upper lip, a second contact zone is located at the lower side of the upper lip, an optional third contact zone is located at the upper side of the lower lip located underneath the upper lip, a fourth contact zone is located at the upper side of the lower lip located at a horizontal distance from the upper lip (and hence at ahorizontal distance from a vertical plane defined by the side surface of the upper lip), and a fifth contact zone which is located at a proximal side of the upward locking element. The fourth and the fifth contact zone may optionally form a single zone.

[0038] In coupled state of adjacent panels, the lower side of the sideward tongue and the upper side of the lower lip preferably mutually enclose an intermediate space, wherein a height of said intermediate space increases towards the upward locking element. Optionally, the lower side of the sideward tongue and the upper side of the lower lip mutually co-act with each other at a location right below the upper lip (as seen in vertical direction, perpendicular to the plane defined by the panel(s)). The third coupling part and / or the fourth coupling part is preferably configured to deform when displacing the fourth coupling part of a panel from the intermediate position to the coupled state. In coupled condition, this (pre)tension may still be present at least partially, although it is also imaginable that the no tension is present between the third coupling part and the fourth coupling part in coupled condition.

[0039] In a preferred embodiment, the third coupling part and / or the fourth coupling part are configured to allow a substantially linear translation of the sideward tongue of a panel into the third groove of an adjacent panel, when displacing the fourth coupling part of a panel from the intermediate position to the coupled state. This translation may at least partially be slightly curved, like e.g. an arc-shaped curve.

[0040] The upper side of the sideward tongue preferably comprises a, preferably planar, proximal upper surface and a, preferably planar, distal upper surface, wherein the distal upper surface is more inclined with respect to the plane defined by the panel than the proximal upper surface of the sideward tongue. Preferably, the lower side of the upper lip comprises a, preferably planar, proximal lower surface and a, preferably planar, distal lower surface, wherein the distal lower surface is more inclined with respect to the plane defined by the panel than the proximal lower surface of the upper lip. More preferably, the (first) inclination of the, preferably planar, proximal upper surface of the sideward tongue is preferably substantially identical to the inclination of the, preferably planar, proximal lower surface of the upper lip, wherein said surfaces are configured not to co-act with each other incoupled state of adjacent panel, but optionally only in the intermediate state.

[0041] Preferably, the (second) inclination of the, preferably planar, distal upper surface of the sideward tongue is preferably substantially identical to the inclination of the, preferably planar, distal lower surface of the lower lip, wherein said surfaces are configured to co-act with each other in coupled state of adjacent panel. Said second inclination is preferably steeper (having a larger vertical component) than the first inclination. The first inclination preferably encloses an angle with a plane defined by the panel(s) of between 10 and 30 degrees. The second inclination preferably encloses an angle with a plane defined by the panel(s) of between 30 and 60 degrees, such as 45 degrees.

[0042] Preferably, a lower side of the upper lip comprises a concavely shaped lower surface connecting to a distal side of the upper lip. This further facilitates insertion of the sideward tongue into the third groove.

[0043] In coupled state of said panels, the panels preferably mutually enclose both a lower joint space, positioned below and adjacent to co-acting and / or facing said contact surfaces of the lower side of the upper lip and the sideward tongue; as well as an upper joint space, positioned above and adjacent said co-acting and / or facing said contact surfaces. Said upper joint space is preferably situated at both sides of a vertical plane (VP) defined a distal end of the third coupling part and / or vertical coupling part.

[0044] A thinnest part of the sideward tongue defining the second downward groove, which in coupled state is facing the upward locking element of the lower lip, has a height which is preferably less than half the length (width) of the sideward tongue, measured from said thinnest part to a distal end of the sideward tongue within the plane defined by the panel(s). Preferably, the sideward tongue is situated at both sides of a vertical plane (VP) defined a distal (upper) end of the third coupling part and / or vertical coupling part (at the (upper) joint of the panels), virtually dividing the sideward tongue into a distal part, located below the upper lip in coupled condition, and a proximal part, located at a (horizontal) distance from the upper lip in coupled condition. The distal part is also referred to as the tip of the sideward tongue.

[0045] Preferably, the width of distal part of the sideward tongue is between 0.2 to 0.6 times, preferably 0.3 to 0.4 times, the width of the proximal part of the sidewardtongue, measured from said thinnest part to a distal end of the sideward tongue within the plane defined by the panel(s). A lower surface of the tip of the sideward tongue is preferably convexedly curved, and an upper surface of the tip of the sideward tongue is preferably planar and inclined and configured to act as sliding surface.

[0046] The above described coupling mechanism of the panels aims to find a balance between position-selective contact portions, and gaps or spaces, defined as inactive portions, formed in between said contact portions. Here, the application of no less than three, preferably three, four or five, predefined contact portions and three, four, five (or more) intermediate gaps or space results in a solid and firm positioning, and hence coupling, of the coupling parts in coupled state of adjacent panels. This coupling is preferably aimed to be a free-of-play coupling, wherein the coupling parts are mutually fixated and locked in coupled state of the coupling parts. When a floor covering composed of said set of (interconnected) panels is being walked upon, tiny mutual movements can be prevents. As most of these noises are produced at the height of the aforementioned contact portions, this mutual panel fixation thus also has as a result that the risk that such sounds are created, is considerably reduced, if not the occurrence thereof is completely excluded. Hence, the design of the profiles of the coupling parts is such that the risk of said undesired noises is reduced even if no sliding agent is applied, which, however, does not exclude that a sliding agent still can be applied on the coupling parts of the floor panels according to the invention. The position-selectively applied gaps, as defined above, are preferably of such a design that the gap creation is secured during production, wherein machine tolerances and hence slight deviations in dimensions of the coupling part are taken into account in the gap design and aimed gap dimensioning. As indicated above, the snap-in mechanism provided by the third coupling part and fourth coupling part does not require high lifting or angling of a panel to be installed, but due to the dedicated intermediate state, wherein the sideward tongue of a panel is already partially inserted into a third groove part enclosed by the upper lip and lower lip (directly below the upper lip) the panel(s) can be installed even in spaces where this is practically no or only little space for panel lifting, e.g. near a door sill (plate). This snap-in movement may involve a temporary elastic deformation of at least one of the coupling parts. This deformation typically occurs during the insertion process of the sideward tongue into the third groove, when the panels to be installed is shifted, more or less linearly(typically in inclined fashion), towards each other. In coupled state, the tension may still be present to urge the panels towards each other. It is also imaginable that in coupled state practically no tension is present between the third coupling part and the fourth coupling part.

[0047] The panel(s) may be oblong rectangular or oblong parallelogrammatic (stretched diamond-like-shaped also indicated as chevron shaped panels allowing installation of a chevron pattern). The first coupling part and the second coupling part may be positioned at opposite short edges. The other edges, such as the long edges, may be provided with first and second coupling parts as well. Alternatively, the other edges, such as the long edges, may be provided with angling down profiles, which are designed to be coupled by a turning or rotational movement, and / or with snapprofiles which are designed to be coupled by a lateral movement, in particular a lateral substantially linear movement, and / or (lateral) snap-in movement. Such profiles for instance have a sideward groove on one of the sides, and a sideward tongue on the opposite side. These profiles are indicated a s the third coupling part and the fourth coupling part. Hence, according to an embodiment, each panel comprises at least one third coupling part and at least one fourth coupling part provided at a second pair of opposite panel edges, wherein said third coupling part and said fourth coupling part are configured to be coupled by means of a lowering movement, and / or an angling movement, and / or a lateral movement and / or a snap-in movement. This provides the advantage of allowing different coupling mechanisms on different edges. As an alternative, all edges could use the same coupling mechanism. It is imaginable that at least one coupling part of the first coupling part and second coupling part is configured to be coupled to at least one coupling part of the third coupling part and fourth coupling part. In this manner, a herringbone pattern may be created by the set of panels.

[0048] The first coupling part and the second coupling part are configured to realize a so-called drop-lock coupling, by lowering, possibly linearly lowering, in particular vertically lowering, and / or angling the second coupling part towards the first coupling part to insert the downward tongue into the upward groove and to insert the upward tongue into the downward groove. This provides the advantage of easy installation without the need for special tools or excessive force. Hence, the panel is provided with hook-like coupling means wherein the upward tongue and thedownward groove, as well as the upward groove and the downward tongue, cooperate and hook behind each other. In this way, these elements provide a (horizontal) locking of two coupled panels in horizontal direction, at least when placed on a horizontal floor. The locking elements, the optional first, optional second, and third and fourth locking element, provide a vertical locking of two coupled panels in vertical direction, at least when placed on a horizontal floor. In the context of this disclosure, the horizontal direction may be considered to be the direction in the plane of the panel, whereas the vertical direction may be considered to be a direction perpendicular to the horizontal direction and hence perpendicular to the plane of the panel. The locking in vertical direction may partially be achieved by the co-action of the first and second locking element (if applied), and is at least partially achieved by the co-action of the third and fourth locking element. Hence, according to an embodiment, in coupled state of said panels, the first coupling part and the co-acting second coupling part of said panels lock the panel both in a direction parallel to the plane defined by the panels as well as in a direction perpendicular to said plane defined by the panels. As an alternative, the coupling could provide locking in only one direction.

[0049] The set of panels according to the invention is typically used to provide a (decorative) floor covering, but can also be applied to form an alternative covering, for example a (decorative) wall covering, a (decorative) ceiling covering, a (decorative) column covering, beam covering, or furniture covering. The panel may have a thickness between 2.5 and 12 mm thick. More preferably, the panel thickness of each panel is 6 mm or less, preferably 5 mm or less, more preferably 4 mm or less. The relatively low positioned third and fourth contact surfaces allow the application of the above coupling mechanism at relatively thin panels. Thinner panels are more easy to handle, more efficient to transport, and are generally cheaper due to material savings compared to thicker panels.

[0050] The lower surface or lower side of the downward tongue and the upper side of the lower bridge may be configured to support the downward tongue at its heel, hence at or close to its proximal side of the downward tongue facing towards the downward flank. An adjacent toe of the lower surface or lower side of the downward tongue, which is positioned farther away from the downward flank than the heel of the downward tongue may (or may not) be positioned at a distance from the lower bridge. This typically results in a single point (zone) of contact - optionallya dual point (zone) of contact - at the lower surface or lower side of the downward tongue. This heel support of the downward tongue results in a relatively stable support at or near the upward tongue, which is beneficial to prevent vertical displacement of the coupling parts at or near the upward tongue, which as such is favourable in order to prevent creaking noise when exerting a (vertical) load onto said coupling parts, for example during walking onto said panels during normal use.

[0051] Additionally or alternatively, the lower surface or lower side of the downward tongue and the upper side of the lower bridge are configured to support the downward tongue at its toe, hence at or close to its distal side of the downward tongue facing away from the downward flank. An adjacent heel of the lower surface or lower side of the downward tongue, which is positioned closer to the downward flank than the toe of the downward tongue is positioned at a distance from the lower bridge. This typically results in a single point (zone) of contact at the lower surface or lower side of the downward tongue. This toe support of the downward tongue results in a relatively stable support close to the joint formed in between adjacent panels, which typically secures the joint and hence the panels as such. A combination of toe support and heel support of the downward tongue is also imaginable.

[0052] According to an embodiment, the lower surface of the downward tongue is a substantially horizontal or inclined lower surface. This inclination with respect to the plane defined by the panel is preferably limited to 5 degrees or less, preferably 3 degrees or less. The lower surface, or at least a part thereof is preferably substantially planar. This provides the advantage of a stable and consistent support surface. As an alternative, the lower surface could have a slight curvature or inclination. The same applies to the upper side of the lower bridge which is preferably substantially horizontal (or slightly inclined) and / or planar lower surface. It may be preferred that the lower surface of the downward tongue and the upper side of the lower bridge extend in mutually (slightly) different directions. According to an embodiment, the lower surface of the downward tongue and the upper side of the bridge mutually enclose an angle, preferably an angle less than 5 degrees, more preferably less than 3 degrees. This small angle provides the advantage of a tight fit while still allowing some tolerance. As an alternative, the surfaces could run in parallel.In a preferred embodiment, in the intermediate position of the third coupling part and fourth coupling part, a lower side of the sideward tongue is supported at a first inclined lower intermediate contact surface by a second inclined lower intermediate contact surface at an upper side of the upward locking element. Said first inclined lower intermediate contact surface preferably encloses an angle with a plane defined by each panel which is smaller than an angle enclosed by said second inclined lower intermediate contact surface and a plane defined by each panel. Said first inclined lower intermediate contact surface and said second inclined lower intermediate contact surface together define a lower intermediate contact zone having a width measured in a plane defined by the panels which is preferably less than 3%, more preferably less than 2%, of the panel thickness and / or having a width of less than 0.08 mm, preferably less than 0.06 mm, such as 0.03 mm, 0.04 mm, or 0.05 mm.

[0053] This angular relationship between the first and second inclined lower intermediate contact surfaces provides the advantage of a controlled and stable support during the intermediate coupling phase, wherein the contact zone is precisely defined and limited in width. By limiting the width of the intermediate contact zone to less than 3%, and preferably less than 2%, of the panel thickness and / or to less than 0.08 mm, preferably less than 0.06 mm, the contact between the coupling parts in cross-sectional view approximates contact points rather than extended contact lines or contact surfaces. This point-like contact configuration significantly reduces the overall surface area of mutual engagement between the coupling profiles during the coupling process. As a result of this reduced contact area, frictional forces between the coupling parts are minimized, which in turn facilitates smoother and easier coupling of adjacent panels. The reduced friction means that less force is required to move the panels from the intermediate position to the coupled state, which is particularly advantageous during installation in confined spaces where the installer has limited room to apply force. Furthermore, the small contact zones result in less material stress on the coupling parts during the coupling process, as the forces are concentrated at predefined locations rather than distributed over larger contact surfaces that could cause uneven stress distribution and potential deformation or damage. This reduced material stress contributes to a longer lifespan of the coupling parts and reduces the risk of cracking or breaking during repeated coupling and uncoupling cycles. The small contact zones also facilitate uncouplingof the panels, for example when individual panels need to be replaced or when the floor covering needs to be disassembled for relocation, as the reduced contact area means less resistance when separating the panels. Additionally, the point-like contact configuration makes the coupling mechanism less sensitive to manufacturing tolerances and variations in the dimensions of the coupling parts, as small deviations have less impact on the coupling behaviour when the contact zones are small. This results in more consistent coupling behaviour across different panels and production batches. The small contact zones also reduce the risk of creaking noises during use, as there is less surface area where friction-induced sounds could be generated when the panels are subjected to loads, for example when being walked upon. The difference in inclination angles ensures that the contact occurs at a predictable location, which facilitates smooth transition from the intermediate position to the coupled state. As an alternative, the first and second inclined lower intermediate contact surfaces could have substantially identical inclination angles, or the angular relationship could be reversed.

[0054] In a further preferred embodiment, in the intermediate position, an upper side of the sideward tongue co-acts at a first inclined upper intermediate contact surface with a second inclined upper intermediate contact surface at a lower side of the upper lip, wherein said first inclined upper intermediate contact surface encloses an angle with a plane defined by each panel which is larger than an angle enclosed by said second inclined upper intermediate contact surface and a plane defined by each panel, and wherein said first inclined upper intermediate contact surface and said second inclined upper intermediate contact surface together define an upper intermediate contact zone having a width measured in a plane defined by the panels which is less than 3%, preferably less than 2%, of the panel thickness and / or having a width of less than 0.08 mm, preferably less than 0.06 mm, such as 0.03 mm, 0.04 mm, or 0.05 mm. This configuration provides the advantage of guiding the sideward tongue into the third groove in a controlled manner during the coupling process, wherein the limited contact zone width ensures that the coupling parts can slide relative to each other with minimal friction. The small width of the upper intermediate contact zone provides similar advantages as described above for the lower intermediate contact zone, including facilitated coupling and uncoupling, reduced material stress, less sensitivity to manufacturing tolerances, and reduced risk of creaking noises. The angular difference between the contactsurfaces creates a self-centering effect that assists in proper alignment of the panels, which further contributes to easy and reliable coupling. The combination of the small lower intermediate contact zone and the small upper intermediate contact zone results in a coupling mechanism that requires minimal force to operate, causes minimal wear on the coupling parts, and provides consistent and predictable coupling behaviour. As an alternative, the angular relationship could be reversed or the contact surfaces could be substantially parallel.

[0055] According to a preferred embodiment, said first inclined lower intermediate contact surface encloses an angle with a plane defined by each panel, which angle is situated between 1 and 8 degrees, preferably between 2 and 6 degrees. This relatively shallow inclination provides the advantage of stable support during the intermediate position while allowing smooth sliding movement towards the coupled state. As an alternative, the angle could be outside this range, for example less than 1 degree or greater than 8 degrees.

[0056] According to another preferred embodiment, said second inclined lower intermediate contact surface encloses an angle with a plane defined by each panel, which angle is situated between 5 and 15 degrees, preferably between 8 and 12 degrees. This steeper inclination compared to the first inclined lower intermediate contact surface provides the advantage of creating a defined contact point rather than a contact surface, which reduces friction during the coupling movement. As an alternative, the angle could be outside this range.

[0057] In a preferred embodiment, said first inclined upper intermediate contact surface encloses an angle with a plane defined by each panel, which angle is situated between 30 and 40 degrees, preferably between 32 and 38 degrees. This inclination provides the advantage of effective guidance of the sideward tongue into the third groove while maintaining sufficient contact for stable positioning in the intermediate state. As an alternative, the angle could be outside this range, such as less than 30 degrees or greater than 40 degrees.

[0058] According to yet another preferred embodiment, said second inclined upper intermediate contact surface encloses an angle with a plane defined by each panel, which angle is situated between 25 and 35 degrees, preferably between 27 and 33degrees. The difference between this angle and the angle of the first inclined upper intermediate contact surface provides the advantage of creating a narrow contact zone that facilitates the sliding movement during coupling. As an alternative, the angle could be outside this range or could be substantially equal to the angle of the first inclined upper intermediate contact surface.

[0059] According to an embodiment, at least one contact surface part of one surface of the lower surface of the downward tongue and the upper side of the bridge runs horizontally and / or runs in inclined fashion, and wherein at least one opposing contact surface part of the lower surface of the downward tongue and the upper side of the bridge runs in inclined fashion, wherein, coupled state of said panels, a height of the intermediate space preferably increases towards the upward tongue or towards the upward flank. This configuration provides the advantage of a secure fit at the contact point while allowing some tolerance.

[0060] According to an embodiment, a shortest distance (HD4) between the fourth locking element and the upward tongue, measured in the plane defined by each panel, is at least 2 times, preferably at least 3 times, the width of the contact surface formed between the lower surface of the downward tongue and the upper side of the bridge in coupled state of adjacent panels. This allows the downward tongue to be designed in a relatively robust manner, which is in favour of the locking engagement and hence of the durability of the locking. According to an embodiment, said shortest distance (HD4), measured in the plane defined by each panel, between the fourth locking element and the upward tongue, measured in the plane defined by each panel, is less than 8 times the width of the contact surface formed between the lower surface of the downward tongue and the upper side of the bridge in coupled state of adjacent panels. This secures sufficiently width and therefore reliable contact surfaces between the downward tongue and the lower bridge.

[0061] According to an embodiment, the contact surface formed between a lower side of the downward tongue and the upper side of the lower bridge in coupled state of adjacent panels is preferably positioned at a (horizontal) distance of at least one, preferably each, virtual vertical plane (perpendicular to the plane defined by the panel) defining the extremities of the fourth locking element, measured in the planedefined by each panel. This provides the advantage of a balanced support. This does not exclude the option that the contact surface could connect to and even be intersected at least one, even each, of said virtual vertical planes.

[0062] According to an embodiment, the contact surface formed between a lower side of the downward tongue and the upper side of the lower bridge, at the lower contact zone, is preferably less than half of the width of the entire lower side and / or the entire lowest surface of the downward tongue. This provides the advantage of creating a relatively large gap in between said downward tongue and said lower bridge. As an alternative, the contact surface could be at least half the width.

[0063] Preferably, the contact surface formed between a lower side of the downward tongue and the upper side of the lower bridge defines a single lower contact zone only. Preferably, at both sides a the lower contact zone, (intentional) intermediate spaces are present to secure that the lower contact zone is the only zone of contact of the lower side of the downward tongue. In coupled state, the intermediate space located closest to the upward tongue is preferably the smallest intermediate space. Typically this smallest intermediate space is or may be banana-shaped. At least a part of the intermediate space located closest to the upward tongue preferably extends in upward direction. The intermediate space located more distant from the upward tongue is preferably connected to a lower joint space and forms one space therewith. The cross-sectional surface area of this latter space defined by the intermediate space and the lower joint space is preferably at least two times to the cross-sectional surface area of the intermediate space located closest to the upward tongue, in particular in case the lower contact zone is situated closer to the upward tongue than to the upward flank. These intermediate spaces and / or other intentional spaces allow expansion of the profiles during normal use without affecting the coupling in between and / or mutual alignment of the panels.

[0064] According to an embodiment, a shortest distance (HD4) between the fourth locking element and the upward tongue, measured in the plane defined by each panel, is smaller than a thickness of each panel. This provides the advantage of a compact coupling design allowing the panel thickness to be kept limited (e.g. 4-6 mm).According to an embodiment, the width of the lower side and / or the width of the lowest surface of the downward tongue is at least half of a thickness of each panel. This provides the advantage of a robust downward tongue and allows for a robust and reliable contact surface between the downward tongue and the lower bridge. This does not take away the option that the downward tongue could have a lower side width which is less than half the panel thickness.

[0065] According to an embodiment, the fourth locking element comprises at least one recess and the third locking element comprises at least one bulge, wherein, in coupled state of adjacent panels, the (at least one) bulge is at least partially accommodated in said (at least one) recess. This may provide the panels sufficient locking, in particular in vertical direction, and typically impedes accidentally uncoupling the panels. Additionally or alternatively, as will also be described below, the third element could alternatively or additionally comprise a recess and the fourth element could alternatively or additionally comprise a bulge.

[0066] According to an embodiment, at least a part of an upper side of the fourth locking element, in particular of a recess of the fourth locking element, defines said at least one inclined fourth contact surface, and wherein at least a part of an upper side of the third locking element, in particular of a bulge of the third locking element, defines said at least one inclined third contact surface. This provides the advantage of smooth engagement of the locking surfaces.

[0067] In an embodiment of the set of panels according to the invention, the recess of the fourth locking element is oversized with respect to the bulge of the third locking element. This provides the advantage of easier coupling and some tolerance.

[0068] Moreover, in this manner it can be more easily realized that the bulge and recess contact each other at the desired location(s) of the bulge and the recess. As an alternative, the recess and bulge could be more closely matched, and hence more or even substantially completely form-fittingly , in size.

[0069] According to an embodiment, in coupled state of said panels, at least one (horizontally extending) space is present between an extremity of the bulge of the third locking element and an extremity of the recess of the fourth locking element, in particular as seen in a plane defined by each panel. This provides the advantageof allowing some flexibility in the coupling and forces the third locking element and fourth locking element to co-act with each other at one or more predefined locations.

[0070] According to an embodiment, said at least one inclined third contact surface and the plane defined by each panel encloses a first angle, preferably between 35 and 45 degrees, and wherein said at least one inclined fourth contact surface and the plane defined by each panel encloses a second angle, preferably between 25 and 35 degrees, wherein the first angle is larger than the second angle. This provides the advantage of a facilitated insertion of the downward tongue into the upward groove while still maintaining a sufficiently large vertical locking effect. This does not exclude the option that the first angle and second angle could be equal or that the second angle could be larger than the first angle.

[0071] According to an embodiment, said inclined fourth contact surface is upwardly inclined towards a vertical plane intersecting the upward tongue, said vertical plane being perpendicular to the plane defined by each panel, and wherein said inclined third contact surface is upwardly inclined in a direction towards the downward tongue. This provides the advantage of guiding the elements into engagement. In case differently shaped third and fourth locking elements would be used, it could be imaginable that one or both surfaces could be downwardly inclined.

[0072] According to an embodiment, the recess of the fourth locking element and the bulge of the third locking element are entirely situated below the horizontal plane (HP) defining the maximum height of the upward tongue. This provides the advantage of a compact locking design allowing the application of the first coupling part and second coupling part onto relatively thin panels, such as for example panels having a thickness of 4 or 5 mm.

[0073] According to an embodiment, the upward flank and a part of a distal side of the downward tongue of the adjacent panel together define an upper joint contact zone, wherein a vertical plane (VP) defined by said upper joint contact zone intersects the recess of the fourth locking element, such that said recess of the fourth locking element is situated at both sides of the vertical plane (VP), and wherein the bulge of the third locking element is preferably situated at a single sideof said vertical plane (VP). This provides the advantage of balanced engagement of the locking elements. As an alternative, the recess could be on one side of the plane.

[0074] According to an embodiment, the fourth locking element comprises a bulge located above the recess of said fourth locking element, and wherein the third locking element comprises a recess located above the bulge of said third locking element, wherein, in coupled state of adjacent panels, the bulge of the fourth locking element is at least partially accommodated in the recess of the third locking element. This provides the advantage of additional locking engagement. As an alternative, only one set of bulges / recesses could be used.

[0075] According to an embodiment, the recess of the third locking element is oversized with respect to the bulge of the fourth locking element. This provides the advantage of easier coupling and some tolerance. As an alternative, the recess and bulge could be more closely matched in size.

[0076] According to an embodiment, in coupled state of said panels, a space is present between an extremity of the bulge of the fourth locking element and an extremity of the recess of the third locking element, in particular as seen in a plane defined by each panel. This provides the advantage of allowing some flexibility in the coupling. As an alternative, the bulge could fully occupy the recess.

[0077] According to an embodiment, the upward flank and a part of a distal side of the downward tongue of the adjacent panel together define an upper joint contact zone and an intersecting vertical plane (VP), wherein the maximum width of the recess of the third locking element in view of the vertical plane (VP) exceeds the maximum width of the of bulge fourth locking element in view of the vertical plane (VP). This provides the advantage of easier coupling. As an alternative, the widths could be equal or the bulge could be wider.

[0078] According to an embodiment, the upward flank and a part of a distal side of the downward tongue of the adjacent panel together define an upper joint contact zone, wherein a vertical plane (VP) defined by said upper joint contact zone intersects the recess of the fourth locking element, such that said bulge of thefourth locking element is situated at both sides of the vertical plane (VP), and wherein the recess of the third locking element is preferably situated at a single side of said vertical plane (VP). This provides the advantage of balanced engagement of the locking elements. As an alternative, the bulge could be on one side of the plane.

[0079] According to an embodiment, each of the bulge of the fourth locking element and the recess of the third locking element is situated at least partially above the horizontal plane (HP) defining or defined by the maximum height (highest point) of the upward tongue. This provides the advantage of additional vertical locking. As an alternative, the elements could be at least partially below the plane. This latter could e.g. be the case in the case maximum height of the upward tongue is at least half the panel thickness.

[0080] According to an embodiment, the fourth locking element and / or the third locking element are, preferably continuously, curved. This provides the advantage of smooth engagement. As an alternative, the elements could have some straight portions. According to an embodiment, at least a part of each of the fourth locking element and the third locking element are S-shaped. This provides the advantage of secure locking engagement. As an alternative, the elements could have a simpler curved shape.

[0081] Preferably, both the third contact surface and / or the fourth contact surface is / are curved. The curvature of the third contact surface and / or the fourth contact surface may be identical, but may also be different. To this end, it is imaginable, for example, that the curvature of the third contact surface is smaller than the curvature of the fourth contact surface, which may facilitate the coupling process while maintaining a reliable locking effect. For example, the curvature of the third contact surface may have a radius of 0.2 - 0.3 mm and the curvature of the fourth contact surface may have a radius of 0.1 - 0.2 mm.

[0082] According to an embodiment, the bulge and lower located recess of the fourth locking element define a curved shape, wherein the curvature of said shape increases from the bulge to the fourth contact surface and decreases from thefourth contact surface to a lower part of the recess. This provides the advantage of guiding the elements into engagement.

[0083] According to an embodiment, the recess and lower located bulge of the third locking element define a curved shape, wherein the curvature of said shape increases from the recess to the third contact surface and further increases from the third contact surface to a lower part of the bulge. This provides the advantage of secure locking engagement. The recess of the third locking element may have a substantially constant curvature (constant radius). This leads to a relatively symmetrical shape of said recess of the third locking element. The bulge of the fourth locking element may have a varying curvature across in vertical direction (height direction), wherein the curvature preferably increases in downward direction. This leads to an asymmetrical shape of said bulge of the fourth locking element.

[0084] According to an embodiment, in coupled state of said panels, the third contact surface and fourth contact surface are entirely positioned at a distance from each other (in a normally (unloaded) coupled state). This provides the advantage of allowing some flexibility in the coupling. In case the panels are mutually shifted and / or angled, for example during exerting a load onto the panels, the third contact surface and fourth contact surface may be moved towards each other and may contact each other thereby limiting the mutual movement between the panels. As an alternative, the surfaces could contact each other in a normally (unloaded) coupled state of adjacent panels.

[0085] According to an embodiment, the panel thickness is at least two times the height of the third locking element and / or the fourth locking element and preferably equal to or less than 4 times the height of the third locking element and / or the fourth locking element. This provides the advantage of a strong locking engagement relative to panel thickness.

[0086] According to an embodiment, the height of the third locking element and / or the fourth locking element is situated between and including 0.8 and 2 mm. This provides the advantage of effective and sufficiently robust locking for typical panel thicknesses. As an alternative, the height could be smaller or larger. Smallerdimensions will facilitate coupling but may affect the locking strength, while larger dimensions may impede the coupling process, but may be in favour of the locking strength.

[0087] According to an embodiment, in coupled state of said panels, the panels mutually enclose both a lower joint space, positioned below and adjacent to co-acting and / or facing said third and fourth locking surfaces, and an upper joint space, positioned above and adjacent to co-acting and / or facing said third and fourth locking surfaces. This provides the advantage of allowing some flexibility in the coupling. As an alternative, one of the spaces could be eliminated.

[0088] According to an embodiment, in coupled state of adjacent panels, the third and fourth contact surfaces define a first tangent line (R1) which runs upwardly in the direction towards the downward tongue, and wherein this tangent line (R1) forms a first angle (A1) with the plane defined by the panels which preferably is smaller than or equal to 45 degrees; and wherein the co-acting proximal side of the upward tongue and the proximal side of the downward tongue define a second tangent line (R2) which wherein this second tangent line (R2) forms a second angle (A2) with the plane defined by the panels which larger than the first angle. This provides the advantage of secure vertical and horizontal locking. As an alternative, the first angle could be larger than the second angle.

[0089] According to an embodiment, (at least a part of) the third locking element and / or (at least a part of) the fourth locking element are made in one piece with the core layer and / or with the panel. According to an embodiment, (at least a part of) the first coupling part and (at least a part of) the second coupling part are made in one piece with the core layer and / or with the panel. This provides the advantage of simplified manufacturing and an efficient cost price of the panels.

[0090] According to an embodiment, the fourth locking element comprises a separate insert provided in a recess of the first coupling part and / or wherein the third locking element comprises a separate insert provided in a recess of the second coupling part, wherein said insert comprises a locking part which, when coupling adjacent panels, arrives in a locking position by at least partially performing a lateral movement wherein the strip co-acts and / or faces an opposing coupling part of anadjacent panel, and wherein the insert or at least a portion thereof is elastically deformable and / or displaceable in order to allow said lateral movement. This provides the advantage of allowing some flexibility in the coupling. As an alternative, the elements could be rigid and non-movable. The use of the insert offers the advantage that the features thereof do not depend on the material of the floor panel. The insert can be configured such that it allows a smooth installation as well as a good vertical locking, and this independent from the material characteristics of the actual panel. The material of the insert preferably comprises a synthetic material. Examples of suitable synthetic materials, which can be applied to this end, are polyvinyl chloride, polypropylene, polyethylene or polyurethane. Further, the material of the insert, in order to increase the strength thereof, may also comprise fibers. For example, mineral fibers, such as glass fibers, can be applied for this purpose. The insert can be manufactured from one and the same material; however, this does not necessarily have to be so. So, the insert can be composed of several materials, which, for example, mutually show a different flexibility. According to the function of the specific portion of the insert, this then can be made of a more or less flexible material. A technique which can be applied for manufacturing the insert from several materials is coextrusion.

[0091] According to an embodiment, the insert described above may make part of third locking element, wherein the insert defines at least a part of at least one inclined third contact surface configured to co-act with and / or face the fourth contact surface of an adjacent panel; and / or wherein, in case the insert makes part of fourth locking element, the insert defines at least a part of at least one inclined fourth contact surface configured to co-act with and / or face the third contact surface of an adjacent panel. This provides the advantage of allowing customization of the contact surfaces.

[0092] According to an embodiment, a transition between the downward flank and an upper side of the downward groove defines a concave vertex, and wherein, preferably, a centreline of the third locking element substantially coincides with a centreline of said concave vertex. This provides the advantage of compact and effective positioning of the locking element and reduces the risk of cracking of the coupling part.According to an embodiment, the third locking element is at least partially located inward compared to an upper part of the side of the downward tongue facing away from the downward flank. This provides the advantage of protecting the locking element.

[0093] According to an embodiment, in coupled state of said panels, the panels mutually enclose both a lower distal space, positioned below and adjacent to said co-acting and / or facing first and second locking surfaces, and an upper distal space, positioned above and adjacent to said co-acting and / or facing first and second locking surfaces. This provides the advantage of allowing some flexibility in the coupling and secures that the panels are configured to co-act with each other at the predefined first and second locking surfaces rather than in the lower or upper distal space which could affect the coupling of the panels.

[0094] According to an embodiment, said upper distal space extends to said proximal side of the upward tongue co-acting with said proximal side of the downward tongue. This means the upper side of the upward tongue may be entirely free of any contact and does not engage the upper side of the lower groove. This provides the advantage of allowing material to collect without interfering with the coupling.

[0095] According to an embodiment, the first and second locking surfaces are positioned at least partially, preferably entirely, below (the level of) the upper side of the lower bridge. This provides the advantage of a compact locking design and a relatively low positioning of the first and second locking surfaces which typically improves the stability of the coupling of the panels and / or facilitates coupling of the panels. It is not excluded that the first and second contact surfaces could at least partially extend above (the level of) the upper side of the lower bridge.

[0096] According to an embodiment, the first locking element comprises a bulge and the second locking element comprises a recess configured to at least partially accommodate said bulge of the first locking element of an adjacent panel. This provides the advantage of secure locking engagement. As an alternative, the first element could have the recess and the second element could have the bulge. A combination of both options, wherein each locking element comprises both at least one bulge and at least one recess is also imaginable.According to an embodiment, the side of the upward tongue facing away from the upward flank comprises two, preferably substantially vertical, side parts, wherein the first locking element is situated in between said substantially vertical side parts. This provides the advantage of protecting the locking element. Preferably, the downward flank comprises two, preferably substantially vertical, side parts, wherein the second locking element is situated in between said substantially vertical side parts. In coupled state, preferably at least one vertical side part of the side of the upward tongue facing away from the upward flank engages at least one vertical side part of the downward flank. This will commonly provide more stability and robustness to the realized coupling between the panels. As an alternative, at least one side part of the upward tongue and / or the downward flank could be angled (inclined) and / or curved.

[0097] According to an embodiment, the upward flank and a part of a distal side of the downward tongue of the adjacent panel together define an upper joint contact zone, and together defining a vertical plane (VP), wherein at the upper joint contact zone the upward flank and said part of the distal side of the downward tongue mutually enclose an angle, preferably of 5 degrees or less, and wherein at the upper joint contact zone the upward flank preferably coincides with said vertical plane (VP) and said part of the distal side of the downward tongue is preferably inclined with respect to said vertical plane (VP). This provides the advantage of a tight joint. As an alternative, the angle could be larger than 5 degrees.

[0098] According to an embodiment, at least a part of the proximal side of the upward tongue facing toward the upward flank is upwardly inclined towards the upward flank, and preferably at least a part of the proximal side of the downward tongue is downwardly inclined towards the downward flank. This angling and inclination creates a so-called “closed groove” system, in which the inclined parts facilitate the vertical locking of coupled panels. In order to couple two panels with such “closed groove”, at least one of the coupling parts may deform at least partially and temporarily. A “closed groove” may thus increase the vertical locking of coupled panels, and may increase the difficulty to couple panels. The angle enclosed by the direction in which the part is inclined and the vertical may for instance lie between 0 and 45 degrees, in particular between 0 and 10 degrees. The angle may exclude 0 degrees, since this would result in a vertical direction and not a direction which canbe considered angled. In the “closed groove” systems, vertical locking is typically improved by increasing the angle enclosed, but the greater the angle, the more difficult it is to couple adjacent panels.

[0099] According to an(other) embodiment, at least a part of the proximal side of the upward tongue is upwardly inclined away from the upward flank, wherein, preferably, at least a part of the proximal side of the downward tongue is be inclined away from the downward flank. This angling and inclination creates a so-called “open groove” system, which is relatively easy to couple, as well as uncouple, and does not require deformation of the coupling parts (or at least not as much as in a “closed groove”). The angle enclosed by the direction in which the part is inclined and the vertical may for instance lie between 0 and 45 degrees, in particular between 0 and 10 degrees. The angle may exclude 0 degrees, since this would result in a vertical direction and not a direction which can be considered angled. Hence, preferably the (complete) side of the upward tongue facing toward the upward flank is upwardly inclined in a direction away from the upward flank, and wherein the (complete) side of the downward tongue facing toward the downward flank is downwardly inclined in a direction away from the downward flank.

[0100] Alternatively or additionally, at least a part of the proximal side of the upward tongue runs vertically (perpendicular to the plane defined by the panel(s), and / or at least a part of the proximal side of the downward tongue runs vertically (perpendicular to the plane defined by the panel(s).

[0101] According to an embodiment, the substantially complete upper side of the upward tongue and / or the substantially complete upper side of the downward groove is / are flat (planar). As an alternative, the upper side(s) could be curved or angled. In a preferred embodiment, the transition between the side of the upward tongue facing away from the upward flank, and the upper side of the upward tongue, defines a convex vertex, and wherein a centreline of the fourth locking element substantially coincides with a centreline of said convex vertex. Aforementioned transition may be a concrete point (or concrete corner) where said two sides (the upper side and the outer (distant) side of the upward tongue) meet each other, or may be a - typically curved - area (or zone or region) connecting said two sides of the upward tongue. In case the transition is formed by an area (or zone or region), a centre (point) of said zone may, for example, be considered as convex vertex. Preferably, theconvex vertex is defined by a transition between a flat, preferably vertically oriented, part of the side of the upward tongue facing away from the upward flank, and a flat, preferably inclined, part of the upper side of the upward tongue. In this preferred embodiment, the transition is a clear corner where the two sides meet each other, wherein the convex vertex coincides with said corner.

[0102] In a preferred embodiment, the transition between the downward flank and the upper side of the downward groove defines a concave vertex, and wherein a centreline of the third locking element is situated in between a centreline of said concave vertex and a centreline of said second locking element. Also in the case, aforementioned transition may be a concrete point (or concrete corner) where said two sides (the upper side of the downward groove, and the downward flank) meet each other, or may be a - typically curved - area (or zone or region) connecting said two sides. In case the transition is formed by an area (or zone or region), a centre (point) of said zone may, for example, be considered as concave vertex. Preferably, the transition between the downward flank and the upper side of the downward groove defines a concave vertex, and wherein the centreline of the third locking element substantially coincides with a centreline of said concave vertex.

[0103] According to an embodiment, the upper side of the downward groove is downwardly inclined in a direction towards the downward flank. This provides robustness to the upper bridge. As an alternative, the upper side could be flat or curved. Preferably, the upper side of the upward tongue is preferably at least partially downwardly inclined towards the distal side of the upward tongue. This means that the highest point of the upward tongue is preferably situated closer to the proximal side of the upward tongue than to the distal side of the upward tongue. Optionally, the highest point may be situated substantially centrally in between said proximal side and said distal side of the upward tongue. Preferably, both inclinations mutually enclose an angle between (and including) 0 and 5 degrees. The inclination of the upper side of the upward tongue is preferably situated between 15 and 45 degrees, more preferably between 25 and 35 degrees, and is most preferably about 30 degrees, with respect to a horizontal plane (being a plane defined by the panel). The inclination of the upper side of the upward tongue is preferably constant, which means the upper side has a substantially flat orientation. Preferably, the upper side of the downward groove has a, preferably likewise(compared to the inclination of the upper side of the upward tongue) inclining orientation, which is more preferably upward in the direction of the downward tongue. A lower side of a bridge connecting the downward tongue to the core (main body) of the panel is defined by the upper side of the downward groove. Applying an inclined upper side of the downward groove will result in a varying thickness of the bridge, as seen from the core in the direction of the downward tongue. This position-dependent bridge thickness, wherein the bridge thickness is preferably relatively large close to the core and relatively small close to the downward tongue, bridge thickness has multiple advantages. The thicker part of the bridge, close to the core, provides the bridge more and sufficient strength and robustness, while the thinner part of the bridge, close to the downward tongue, forms the weakest point of the bridge and will therefore be decisive for the location of first deformation (pivoting point) during coupling. Since this point of deformation is located close to the downward tongue the amount of material to be deformed to be able to insert the downward tongue into the upward groove can be kept to a minimum. Less deformation leads to less material stress which is in favour of the life span of the coupling part(s) and hence of the panel(s).

[0104] According to an embodiment, the minimal thickness of the second coupling part, in particular the bridge thereof, is less than half the total thickness of the panel. This provides the advantage of allowing flexibility in the coupling. As an alternative, the thickness could be equal to or greater than half the panel thickness.

[0105] As indicated above, according to an embodiment, a panel thickness of each panel may be 6 mm or less, preferably 5 mm or less, more preferably 4 mm or less. This provides the advantage of material savings and easier handling. This does not exclude the option that thicker panels (> 6 mm) may be used. The panel may for instance be elongated, and may have a width between 10 and 100 cm, and a length of 50 to 250 cm.

[0106] At least one core layer of at least one panel may comprise at least one polymer material, in particular at least one polymer matrix, preferably at least one thermoplastic, which polymer material is preferably at least partially composed of a polymer that is selected from the group consisting of: polypropylene (PP), polyurethane (PU), thermoplastic polyurethane (TPU), polystyrene (PS),polyethylene (PE), polyvinyl chloride (PVC), at least one polyester, or mixtures thereof. In case at least one polyester is used in the core layer(s), this polyester is preferably a homopolyester, such as polyethylene terephthalate (PET), or polyethylene furanoate (PEF), and / or a copolyester, such as polyethylene furanoate terephthalate (PEFT) or polyethylene terephthalate glycol-modified PETG). PET is a homopolyester made from terephthalic acid and ethylene glycol. PEF is also a homopolyester, derived from furandicarboxylic acid and ethylene glycol. It is considered a more sustainable alternative to PET due to its bio-based origin. PEFT is a copolyester made by copolymerizing furandicarboxylic acid, terephthalic acid, and ethylene glycol. PETG is a copolyester. It is modified by adding glycol, such as cyclohexanedimethanol (CHDM), which provides greater clarity and durability compared to standard PET. The use of one or more polyesters in the panel(s) according to the invention may be advantageous and preferred over PVC and various other thermoplastic polymers due to the relatively high temperature resistance of polyesters. Contrary to PVC and various other thermoplastic polymers, polyesters are suitable to withstand temperatures of above 200 degrees Celsius.

[0107] Preferably, at least one core layer is entirely composed of a mixture of at least one polymer material, in particular at least one polymer matrix, and at least one filler, preferably a mineral filler, such as chalk and / or talc. The core layer and / or the panels as such may be free of any glass (particles). The presence of glass may render post-use recycling more difficult. Despite of this, it may be imaginable that glass is used in the set of panels according to the invention.

[0108] Optionally, at least one core layer, comprises at least one additive chosen from the group consisting of talc, chalk, wood, graphene, graphite, calcium carbonate, titanium dioxide, calcined clay, porcelain, iron oxide, at least one fatty acid salt, glass particles, glass fibres, carbon particles, silicon particular, a mineral filler, rice, a natural filler, a polymer, such as an elastomer and / or latex. Said one or more mineral fillers may include chalk (calcium carbonate) and / or talc. These inert fillers lower the cost price of the panels. Some of these fillers are functional fillers rather than inert fillers, such as an elastomeric filler and / or glass particles, which could influence the elasticity of the panel(s) layer. It is imaginable and even preferably that the core layer comprises at least one polymer, in particular thermoplasticpolymer, such as PVC, PET, TPU, PET, PEF, PEFT, and / or PETG; and / or at least one mineral filler, wherein in said core layer the overall weight percentage of the mineral filler(s) exceeds the overall weight percentage of the polymer(s).

[0109] At least a part of the core layer may be foamed. At least a part of the core layer may be solid (non-foamed). The core layer may be flexible, semi-rigid, or substantially rigid. The polymer may be a virgin polymer, a recycled polymer, or a mixture of virgin and recycled polymer. The core may comprise at least one composite material of at least one polymeric material and at least one non-polymeric material.

[0110] The thermoplastic polymer(s) comprising core layer(s), optionally enriched with one or more fillers, is / are preferably extruded core layer(s). The panels may comprise a plurality of laminated core layers. At least two of these layers may be extruded layers, preferably co-extruded layers. Optionally at least one reinforcement layer, such as a glass fiber layer, a graphene layer, and / or a DLC (diamond-like carbon) layer, is situated in between adjacent core layers.

[0111] Additionally or alternatively, the core layer may comprise magnesium oxide and / or magnesium hydroxide, and / or cement, and / or gypsum, and / or ceramic. It is imaginable that at least one panel layer, preferably the core layer, comprises wood and / or a wood-based material, such as MDF or HDF.

[0112] According to an embodiment, each panel comprises a decorative top structure applied, directly or indirectly, onto the core layer, wherein said decorative top structure comprises at least one decorative layer and at least one translucent or transparent wear layer situated above the decorative layer. This provides the advantage of an attractive and durable surface. As an alternative, the decorative structure could be integrated into and / or be formed by the core layer.

[0113] In an embodiment, each panel comprises a decorative top structure applied, directly or indirectly, onto the core layer, wherein said decorative top structure comprises at least one decorative layer and at least one translucent or transparent wear layer situated above the decorative layer. Such wear layers are often composed of a transparent polymer such as polyvinylchloride (PVC) or transparentpolyurethane (PU). A top coating may be applied on top of said wear layer to improve the scratch resistance of the floor panel.

[0114] In a preferred embodiment, the decorative top structure comprises a textured upper surface. A textured upper surface may improve the anti-slip properties of the panel(s). Preferably, the texture surface makes part of at least one transparent and / or translucent layer, in particular at least one wear layer and / or at least one top coating. One or more of these layers may comprise and / or consist of DLC (diamond-like coating) and / or graphene. Preferably a decorative visual print layer (decorative layer) is located underneath said at least one transparent and / or translucent layer. This textured surface (relief surface) typically improves the optical and haptic appearance of the decorative layer. Said textured surface comprises a pattern of recesses (indentations or impressions) and / or projections, wherein said pattern is preferably at least partially realized by means of printing, in particular digital printing (i.e. by means of a digital printing technique). Digital printing is a method of printing from a digital-based image directly to a media. This digital image can be a decorative image (or a plurality of images), such as the aforementioned decorative visual print layer (decorative layer), but also an image representing another part of the top structure, such as at least one wear layer and / or at least one top coating. The digital image can either be a 2D or a 3D image. By digitally (3D) printing the top structure, an infinite degree of freedom of design of the top structure (and the decorative layer) can be obtained, wherein the top structure (and the decorative layer) moreover can be applied in an accurate manner with a high level of detail, which leads to realistic appearances and unique, one-of-a-kind decorative panels. This result cannot be achieved by means of traditional mechanically impressed covering structures. As printing device(s), for example, one or more inkjet printers and / or laser printers may be used. As indicated above, a substantially transparent or translucent part of the top structure may be partially or entirely digitally printed. The decorative visual print layer is preferably digitally printed. To this end, transparent or translucent, either coloured or non-coloured (transparent), ink may be used. At least one substance, in particular ink, used to realize at least a part of the decorative top structure, may be provided with graphene and / or graphene derivative(s) and / or DLC and / or other (solid) particles. This latter results in the situation that DLC material, in particular DLC particlesand / or a DLC comprising layer, can be applied by means of printing, in particular digital printing, or alternatively by means of spraying, pouring, or rolling.

[0115] Preferably, at least a part of the textured surface of the top structure is aligned in register with at least a part of at least one decor image formed by said decorative print layer, in particular at least one pattern defined by at least one decor image formed by the decorative print layer. By applying an alignment in register, also referred to as embossing in register, a very realistic and / or artistic design and appearance of the panel can be realized. In this manner, for example, a realistic wood nerve pattern can be realized, wherein the decorated printed wood nerves (2D) are in register (inline) with the embossed printed wood nerves (3D). The same effect can, for example, be realized with a stone like design, an animal skin design, etcetera. Also, in case one or more artificial, decorative grout lines and / or one or more bevels are printed, the textured surface may comprise one or more recessed channels directly above said decorative grout lines to realize a realistic appearance of the panel which is practically equal to the surface relief obtained when using real tiles and grouts.

[0116] The visual print layer not only may be composed solely of a decorative ink layer, but it also is imaginable that the visual print layer comprises a substrate layer (or carrier layer), such as a polymer film or paper film or primer layer, onto which a decorative ink layer (a decor) is printed or otherwise applied. Preferably the substrate layer is a white or whitish layer, which will typically enhance the colour authenticity of the printed decor. Said substrate layer may have a textured surface, such as a nanotextured and / or microtextured surface. This may facilitate bonding of further layers on top of said decorative layer, such as a wear layer and / or a DLC comprising layer, in particular a DLC comprising protective coating. Said visual print layer may be attached directly to the core, e.g. by fusing the visual print layer onto the core or by gluing the visual print layer to the core, wherein use can be made e.g. of a polyurethane adhesive. Optionally, an upper surface of the core is covered by at least one primer layer before attaching the visual print layer to the core, wherein the visual print layer will actually be attached to the (upper) primer layer applied to the core. This preferred embodiment implies that (at least a part of) the DLC may be applied on top of said decorative print layer, and hence is able to contribute to the protection of said decorative print layer. As mentioned above, thedecorative top structure can be partially or entirely realized by digital printing. At least one wear layer, and preferably each wear layer in case a plurality of wear would be applied, is preferably made of transparent or translucent polyurethane or, alternatively, polyvinylchloride, polypropylene, a (poly)acrylate polymer (acrylic polymer), or any another suitable transparent or translucent polymer, which polymer(s) may be enriched with one or more additives, such as DLC material.

[0117] Instead of or in addition to the application of a printed decorative layer covered by at least one wear layer, it is also imaginable that the top section of the decorative top structure comprises or is entirely formed by at least one tile. This tile may be made of sliceable natural stone, marble, concrete, limestone, granite, slate, glass, ceramics, wood, or composite material. Particularly preferred are ceramic materials of a type selected from the group consisting of Monocuttura ceramic, Monoporosa ceramic, porcelain ceramic, or multi-casted ceramic. This tile may be a relatively thin tile (veneer tile) as this tile is attached to the core layer, with a preferred thickness of less than 1 cm, preferably less than 7.5 mm, more preferably less than 5 mm.

[0118] It may be preferred that at least one of the first coupling part and second coupling part are configured to deform during coupling and preferably to create a tension (pretension) between them in coupled state. Preferably, in coupled state the panels are urged towards each other. This creates an additional locking force and / or water tightness of the connection, in particular at the joint in between the panel.

[0119] Additionally or alternatively, it may be preferred that at least one of the third coupling part and fourth coupling part are configured to deform during coupling and preferably to create a tension (pretension) between them in coupled state.

[0120] Preferably, in coupled state the panels are urged towards each other. It is also imaginable that the first coupling part and second coupling part are designed to not to create a tension (pretension) between them in coupled state, which leads to (substantially) tensionless coupling parts. It is also imaginable that the third coupling part and fourth coupling part are designed to not to create a tension (pretension) between them in coupled state, which leads to (substantially) tensionless coupling parts.The invention also relates to a covering, in particular a decorative covering, such as a decorative floor covering or decorative wall covering, comprising a plurality of interconnected panels of the set of panels according to the invention.

[0121] Preferred embodiments of the invention as set out in the non-limitative set of clauses presented below.

[0122] Clauses

[0123] 1. A set of panels, in particular decorative panels, such as decorative floor panels or decorative wall panels, each panel comprising:

[0124] • at least one core layer,

[0125] • at least one optional first coupling part and at least one optional second coupling part provided at different panel edges, preferably at a first pair of opposite panel edges,

[0126] wherein said optional first coupling part comprises:

[0127] o an upward tongue,

[0128] o at least one upward flank lying at a distance from the upward tongue, o an upward groove formed in between the upward tongue and the upward flank, wherein the upward groove is adapted to receive at least a part of a downward tongue of a second coupling part of an adjacent panel, and wherein the upward tongue is connected to the upward flank via a lower bridge, wherein a substantially horizontal and / or planar upper side of said lower bridge defines at least a part of a bottom side of the upward groove configured to support said downward tongue of an adjacent panel, and

[0129] o at least one optional first locking element provided at a distal side of the upward tongue facing away from the upward flank, wherein said optional first locking element comprises at least one first contact surface,

[0130] o at least one fourth locking element provided at the upward flank, wherein said fourth locking element comprises at least one inclined fourth contact surface, wherein said optional second coupling part comprises:

[0131] o a downward tongue having a lower side which is preferably at least partially planar,

[0132] o at least one downward flank lying at a distance from the downward tongue,o a downward groove formed in between the downward tongue and the downward flank, wherein the downward groove is adapted to receive at least a part of an upward tongue of a first coupling part of an adjacent panel,

[0133] o at least one optional second locking element provided at the downward flank, wherein said optional second locking element comprises at least one second contact surface configured to co-act with and / or face the first contact surface of an adjacent panel,

[0134] o at least one third locking element provided at a distal side of the downward tongue facing away from the downward flank, wherein said third locking element comprises at least one inclined third contact surface configured to co-act with and / or face the fourth contact surface of an adjacent panel,

[0135] wherein the third contact surface and the fourth contact surface are entirely located below a horizontal plane (HP) defined by a highest point of the upward tongue, and running parallel to a plane defined by the panel, and

[0136] wherein, in coupled state of said first coupling part and said second coupling part of adjacent panels,

[0137] a proximal side of the upward tongue facing towards the upward flank coacts with a proximal side of the downward tongue facing the downward flank of an adjacent panel,

[0138] the upper side of said lower bridge supports a part of the lower side of the downward tongue of an adjacent panel, at a lower contact zone which is preferably located closer to the proximal side of the upward tongue than to the upward flank, a part of the upward flank co-acts with a part of a distal side of the downward tongue of the adjacent panel,

[0139] wherein, in coupled state, adjacent panels enclose:

[0140] at least one distal space between the distal side of the upward tongue and the facing downward flank,

[0141] at least one intermediate space between the upper side of the lower bridge and the facing lower side of the downward tongue, preferably at both sides of the lower contact zone, and

[0142] at least one joint space between the upward flank and the distal side of the downward tongue;

[0143] wherein each panel further comprises at least one third coupling part and at least one fourth coupling part provided at different panel edges, preferably at a second pair of opposite panel edges, wherein said third coupling part and said fourthcoupling part are configured to be coupled by means of a lateral snap-in movement,

[0144] wherein the fourth coupling part comprises:

[0145] o a sideward tongue extending in a direction substantially parallel to the upper side of the core layer,

[0146] o at least one second downward flank lying at a distance from the sideward tongue, and

[0147] o a second downward groove formed between the sideward tongue and the second downward flank; and

[0148] wherein the third coupling part comprises a third groove configured for accommodating at least a part of the sideward tongue of the fourth coupling part of an adjacent panel, said third groove being defined by an upper lip and a lower lip, wherein said lower lip is provided with an upward locking element,

[0149] wherein the third coupling part and fourth coupling part are designed such that the fourth coupling part of a first panel can be positioned in an intermediate position with respect to the third coupling part of an adjacent panel, wherein, in said intermediate position, the planes defined by the panels in the intermediate state run in parallel, and wherein a lower side of the sideward tongue is supported by, preferably an upper side of, the upward locking element while a part of the sideward tongue is located within the third groove and below the upper lip, and wherein, in coupled state of said third coupling part and said fourth coupling part of adjacent panels:

[0150] at least a part of the sideward tongue is inserted into the third groove of an adjacent panel, and wherein at least a part of the upward locking element of said second panel is inserted into the second downward groove of said first panel, a proximal side of the upward locking element facing towards the third groove co-acts with a proximal side of the downward tongue facing the downward flank of an adjacent panel to prevent drifting apart of said panels,

[0151] the upper side of said lower lip supports a part of the lower side of the sideward tongue of an adjacent panel, at a lower contact zone which is preferably located adjacent to the proximal side of the upward locking element,

[0152] at least a part of an end surface of the upper lip co-acts with a part of a distal side of the fourth coupling part of the adjacent panel,

[0153] wherein, in coupled state of said third coupling part and said fourth coupling part, adjacent panels enclose:at least one distal space between the distal side of the lower lip and a facing downward flank of the fourth coupling part,

[0154] at least one intermediate space between the upper side of the lower lip and the facing lower side of the sideward tongue at at least one side of said lower contact zone, and

[0155] at least one joint space between the third coupling part, in particular the upper lip and / or the third groove, and a distal side of the sideward tongue.

[0156] 2. Set of panels according to any of the preceding clauses, wherein, in the intermediate position of adjacent panels, an upper surface of the sideward tongue co-acts with a lower side of the upper lip.

[0157] 3. Set of panels according to clause 2, wherein the upper surface of the sideward tongue configured to co-act with the lower side of the upper lip of an adjacent panel is at least partially downwardly inclined towards a terminal portion of the sideward tongue, wherein said inclined contact surface is preferably is configured as sliding surface to slide the sideward tongue into the third groove of an adjacent panel.

[0158] 4. Set of panels according to any of the preceding clauses, wherein a front contact surface located at the lower side of the upper lip configured to co-act with the sideward tongue of an adjacent panel is downwardly inclined towards a terminal portion of the third groove, wherein said inclined contact surface is preferably configured as sliding surface to facilitate sliding the sideward tongue into the third groove.

[0159] 5. Set of panels according to any of the preceding clauses, wherein, in the intermediate position, the shortest vertical distance, perpendicular to a plane defined by the panels, between the front contact surfaces, defined by the co-action between the upper lip and the sideward tongue, and the rear contact surfaces, defined by the co-action between the proximal side of the upward locking element and the sideward tongue, is preferably 20-30% of the panel thickness and / or between 0.8 and 1.5 mm.6. Set of panels according to any of the preceding clauses, wherein the vertical distance, perpendicular to a plane defined by the panels, for displacing the fourth coupling part from the intermediate state into the coupled state is preferably 10-50% of the panel thickness and / or between 0.3 and 1.0 mm.

[0160] 7. Set of panels according to any of the preceding clauses, wherein the upper side of the lower lip has a deepened portion which defines the lowest point or lowest zone of the lower lip, wherein said deepened portion is preferably situated directly adjacent to the upward locking element, and wherein said deepened portion is configured to support the sideward tongue in the coupled state.

[0161] 8. Set of panels according to any of the preceding clauses, wherein the lower side of the sideward tongue has a downwardly protruding portion which defines the lowest point or lowest zone of the sideward tongue, wherein said downwardly protruding portion is preferably situated directly adjacent to a proximal side of the sideward tongue acting as locking surface.

[0162] 9. Set of panels according to clause 7 and 8, wherein, in the coupled state, the downwardly protruding portion of the sideward tongue is supported by the deepened portion lower lip, wherein the width of the deepened portion of the lower lip preferably exceeds the width of the downwardly protruding portion of the sideward tongue.

[0163] 10. Set of panels according to any of the preceding clauses, wherein, in the coupled state of adjacent panels, the third coupling part, preferably only, co-acts with the fourth coupling part at spaced contact zones, wherein a first contact zone is located at a side surface of the upper lip, a second contact zone is located at the lower side of the upper lip, an optional third contact zone is located at the upper side of the lower lip located underneath the upper lip, a fourth contact zone is located at the upper side of the lower lip located at a horizontal distance from the upper lip, and a fifth contact zone which is located at a proximal side of the upward locking element, wherein the fourth and the fifth contact zone may optionally form a single zone.11. Set of panels according to any of the preceding clauses, wherein, in coupled state of adjacent panels, the lower side of the sideward tongue and the upper side of the lower lip mutually enclose an intermediate space, wherein a height of said intermediate space increases towards the upward locking element.

[0164] 12. Set of panels according to any of the preceding clauses, wherein the third coupling part and / or the fourth coupling part is configured to deform when displacing the fourth coupling part of a panel from the intermediate position to the coupled state.

[0165] 13. Set of panels according to any of the preceding clauses, wherein the third coupling part and / or the fourth coupling part are configured to allow a substantially linear translation of the sideward tongue of a panel into the third groove of an adjacent panel, when displacing the fourth coupling part of a panel from the intermediate position to the coupled state.

[0166] 14. Set of panels according to any of the preceding clauses, wherein the upper side of the sideward tongue comprises a, preferably planar, proximal upper surface and a, preferably planar, distal upper surface, wherein the distal upper surface is more inclined with respect to the plane defined by the panel than the proximal upper surface of the sideward tongue.

[0167] 15. Set of panels according to any of the preceding clauses, wherein the lower side of the upper lip comprises a, preferably planar, proximal lower surface and a, preferably planar, distal lower surface, wherein the distal lower surface is more inclined with respect to the plane defined by the panel than the proximal lower surface of the upper lip.

[0168] 16. Set of panels according to clause 14 and clause 15, wherein the inclination of the, preferably planar, proximal upper surface of the sideward tongue is preferably substantially identical to the inclination of the, preferably planar, proximal lower surface of the upper lip, wherein said surfaces are configured not to co-act with each other in coupled state of adjacent panel; and / or wherein the inclination of the, preferably planar, distal upper surface of the sideward tongue is preferably substantially identical to the inclination of the, preferably planar, distal lower surfaceof the lower lip, wherein said surfaces are configured to co-act with each other in coupled state of adjacent panel.

[0169] 17. Set of panels according to any of the preceding clauses, wherein a lower side of the upper lip comprises a concavely shaped lower surface connecting to a distal side of the upper lip.

[0170] 18. Set of panels according to any of the preceding clauses, wherein, in coupled state of said panels, the panels mutually enclose both a lower joint space, positioned below and adjacent to co-acting and / or facing said contact surfaces of the lower side of the upper lip and the sideward tongue; as well as an upper joint space, positioned above and adjacent said co-acting and / or facing said contact surfaces.

[0171] 19. Set of panels according to clause 18, wherein the upper joint space is situated at both sides of a vertical plane (VP) defined a distal end of the third coupling part and / or vertical coupling part.

[0172] 20. Set of panels according to any of the preceding clauses, wherein the lower side of the downward tongue is a substantially horizontal and / or planar .

[0173] 21. Set of panels according to any of the preceding clauses, wherein the lower side of the downward tongue and the upper side of the bridge mutually enclose an angle, preferably an angle less than 5 degrees, more preferably less than 3 degrees.

[0174] 22. Set of panels according to any of the preceding clauses, wherein at least one contact surface part of one surface of the lower side of the downward tongue and the upper side of the bridge runs horizontally and / or runs in inclined fashion, and wherein at least one opposing contact surface part of the lower side of the downward tongue and the upper side of the bridge runs in inclined fashion, wherein, coupled state of said panels, a height of the intermediate space preferably increases towards the upward flank.23. Set of panels according to any of the preceding clauses, wherein a shortest distance (HD4) between the fourth locking element and the upward tongue, measured in the plane defined by each panel, is at least 3 times the width of the contact surface formed between the lower side of the downward tongue and the upper side of the bridge in coupled state of adjacent panels.

[0175] 24. Set of panels according to any of the preceding clauses, wherein the contact surface formed between a lower side of the downward tongue and the upper side of the bridge in coupled state of adjacent panels is positioned at a distance of one or more virtual vertical planes defined by the fourth locking element.

[0176] 25. Set of panels according to any of the preceding clauses, wherein the contact surface formed between a lower side of the downward tongue and the upper side of the bridge is less than half of the width of the lower side and / or lowest surface of the downward tongue.

[0177] 26. Set of panels according to any of the preceding clauses, wherein a shortest distance (HD4) between the fourth locking element and the upward tongue, measured in the plane defined by each panel, is smaller than a thickness of each panel.

[0178] 27. Set of panels according to any of the preceding clauses, wherein width of the lower side and / or the width lowest surface of the downward tongue is at least half of a thickness of each panel.

[0179] 28. Set of panels according to any of the preceding clauses, wherein the fourth locking element comprises a recess and the third locking element comprises a bulge, wherein, in coupled state of adjacent panels, the bulge is at least partially accommodated in said recess.

[0180] 29. Set of panels according to clause 28, wherein at least a part of an upper side of the fourth locking element defines said at least one inclined fourth contact surface, and wherein at least a part of an upper side of the third locking element defines said at least one inclined third contact surface.30. Set of panels according to any of clauses 28-29, wherein the recess of the fourth locking element is oversized with respect to the bulge of the third locking element.

[0181] 31. Set of panels according to any clauses 28-30, wherein, in coupled state of said panels, a space is present between an extremity of the bulge of the third locking element and an extremity of the recess of the fourth locking element, in particular as seen in a plane defined by each panel.

[0182] 32. Set of panels according to any of clauses 28-31 , wherein said at least one inclined third contact surface and the plane defined by each panel encloses a first angle, preferably between 35 and 45 degrees, and wherein said at least one inclined fourth contact surface and the plane defined by each panel encloses a second angle, preferably between 25 and 35 degrees, wherein the first angle is larger than the second angle.

[0183] 33. Set of panels according to any of clauses 28-32, wherein said inclined fourth contact surface is upwardly inclined towards a vertical plane intersecting the upward tongue, said vertical plane being perpendicular to the plane defined by each panel, and wherein said inclined third contact surface is upwardly inclined in a direction towards the downward tongue.

[0184] 34. Set of panels according to any of clauses 28-33, wherein the recess of the fourth locking element and the bulge of the third locking element are entirely situated below the horizontal plane (HP) defined by the highest point of the upward tongue.

[0185] 35. Set of panels according to any of clauses 28-34, wherein the upward flank and a part of a distal side of the downward tongue of the adjacent panel together define an upper joint contact zone, wherein a vertical plane (VP) defined by said upper joint contact zone intersects the recess of the fourth locking element, such that said recess of the fourth locking element is situated at both sides of the vertical plane (VP), and wherein the bulge of the third locking element is preferably situated at a single side of said vertical plane (VP).36. Set of panels according to any of clauses 28-35, wherein the fourth locking element comprises a bulge located above the recess of said fourth locking element, and wherein the third locking element comprises a recess located above the bulge of said third locking element, wherein, in coupled state of adjacent panels, the bulge of the fourth locking element is at least partially accommodated in the recess of the third locking element.

[0186] 37. Set of panels according to clause 36, wherein the recess of the third locking element is oversized with respect to the bulge of the fourth locking element.

[0187] 38. Set of panels according to clause 36 or 37, wherein, in coupled state of said panels, a space is present between an extremity of the bulge of the fourth locking element and an extremity of the recess of the third locking element, in particular as seen in a plane defined by each panel.

[0188] 39. Set of panels according to any of clauses 36-38, wherein the upward flank and a part of a distal side of the downward tongue of the adjacent panel together define an upper joint contact zone and an intersecting vertical plane (VP), wherein the maximum width of the recess of the third locking element in view of the vertical plane (VP) exceeds the maximum width of the of bulge fourth locking element in view of the vertical plane (VP).

[0189] 40. Set of panels according to any of clauses 36-39, wherein the upward flank and a part of a distal side of the downward tongue of the adjacent panel together define an upper joint contact zone, wherein a vertical plane (VP) defined by said upper joint contact zone intersects the recess of the fourth locking element, such that said bulge of the fourth locking element is situated at both sides of the vertical plane (VP), and wherein the recess of the third locking element is preferably situated at a single side of said vertical plane (VP).

[0190] 41. Set of panels according to any of clauses 36-40, wherein each of the bulge of the fourth locking element and the recess of the third locking element is situated at least partially above the horizontal plane (HP) defined by the highest point of the upward tongue.42. Set of panels according to any of the preceding clauses, wherein the fourth locking element and / or the third locking element are continuously curved.

[0191] 43. Set of panels according to any of the preceding clauses, wherein at least a part of each of the fourth locking element and the third locking element are S-shaped.

[0192] 44. Set of panels according to any of clauses 36-41 and any of clauses 42-43, wherein the bulge and lower located recess of the fourth locking element define a curved shape, wherein the curvature of said shape increases from the bulge, preferably an upper part of the bulge, towards the fourth contact surface and decreases from the fourth contact surface towards the recess, preferably a lower part of the recess.

[0193] 45. Set of panels according to any of clauses 36-41 and any of clauses 42-44, wherein a curvature of the bulge of the fourth locking element and a curvature of the lower located recess of the fourth locking element are each less than a curvature of the fourth locking surface.

[0194] 46. Set of panels according to any of clauses 36-41 and any of clauses 42-45, wherein the recess and lower located bulge of the third locking element define a curved shape, wherein the curvature of said shape increases from the recess, preferably an upper part of the recess, towards the third contact surface and further increases from the third contact surface towards the bulge, preferably a lower part of the bulge.

[0195] 47. Set of panels according to any of clauses 36-41 and any of clauses 42-46, wherein a curvature of the recess of the third locking element is less than a curvature of the third contact surface and wherein both said curvatures are less than a curvature of the lower located bulge of the third locking element.

[0196] 48. Set of panels according to any of the preceding clauses, wherein the upward flank and a part of a distal side of the downward tongue of the adjacent panel together define an upper joint contact zone, and together defining a vertical plane (VP), wherein at the upper joint contact zone the upward flank and said partof the distal side of the downward tongue mutually enclose an angle, preferably of 5 degrees or less, and wherein at the upper joint contact zone the upward flank preferably coincides with said vertical plane (VP) and said part of the distal side of the downward tongue is preferably inclined with respect to said vertical plane (VP).

[0197] 49. Set of panels according to any of the preceding clauses, wherein, in coupled state of said panels, the third contact surface and fourth contact surface are entirely positioned at a distance from each other.

[0198] 50. Set of panels according to any of the preceding clauses, wherein the panel thickness is at least two times the height of the third locking element and / or the fourth locking element and preferably less than 4 times the height of the third locking element and / or the fourth locking element.

[0199] 51. Set of panels according to any of the preceding clauses, wherein the height of the third locking element and / or the fourth locking element is situated between and including 0.8 and 2 mm.

[0200] 52. Set of panels according to any of the preceding clauses, wherein, in coupled state of said panels, the panels mutually enclose both a lower distal space, positioned below and adjacent to said co-acting and / or facing first and second contact surfaces, and an upper distal space, positioned above and adjacent to said co-acting and / or facing first and second contact surfaces

[0201] 53. Set of panels according to clause 52, wherein said upper distal space extends to said proximal side of the upward tongue co-acting with said proximal side of the downward tongue.

[0202] 54. Set of panels according to any of the preceding clauses, wherein the first and second contact surfaces are positioned below the upper side of the lower bridge.

[0203] 55. Set of panels according to any of the preceding clauses, wherein the first locking element comprises a bulge and the second locking element comprises arecess configured to at least partially accommodate said bulge of the first locking element of an adjacent panel.

[0204] 56. Set of panels according to one of the preceding clauses, wherein the side of the upward tongue facing away from the upward flank comprises two substantially vertical side parts, wherein the first locking element is situated in between said substantially vertical side parts

[0205] 57. Set of panels according to any of the preceding clauses, wherein, in coupled state of said panels, the panels mutually enclose both a lower joint space, positioned below and adjacent to co-acting and / or facing said third and fourth contact surfaces, and an upper joint space, positioned above and adjacent to coacting and / or facing said third and fourth contact surfaces.

[0206] 58. Set of panels according to any of the preceding clauses, wherein the first coupling part and the second coupling part are configured to be coupled by lowering and / or angling the second coupling part of a panel into the first coupling part of an adjacent panel.

[0207] 59. Set of panels according to any of the preceding clauses, wherein in coupled state of said panels, the first coupling part and the co-acting second coupling part of said panels lock the panel both in a direction parallel to the plane defined by the panels as well as in a direction perpendicular to said plane defined by the panels.

[0208] 60. Set of panels according to any of the preceding clauses, wherein at least a part of the proximal side of the upward tongue is upwardly inclined towards the upward flank, and wherein at least a part of the proximal side of the downward tongue is downwardly inclined towards the downward flank.

[0209] 61. Set of panels according to any of the preceding clauses, wherein at least a part of the proximal side of the upward tongue is upwardly inclined away from the upward flank, and wherein at least a part of the proximal side of the downward tongue is downwardly inclined away from the downward flank.62. Set of panels according to any of the preceding clauses, wherein, in coupled state of adjacent panels, the third and fourth contact surfaces define a first tangent line (R1) which runs upwardly in the direction towards the downward tongue, and wherein this tangent line (R1) forms a first angle (A1) with the plane defined by the panels which preferably is smaller than or equal to 45 degrees; and wherein the coacting proximal side of the upward tongue and the proximal side of the downward tongue define a second tangent line (R2) which wherein this second tangent line (R2) forms a second angle (A2) with the plane defined by the panels which larger than the first angle.

[0210] 63. Set of panels according to any of the preceding clauses, wherein at least a part of the third locking element and / or at least a part of the fourth locking element are made in one piece with the core layer, and wherein, preferably, the first coupling part and second coupling part are made in one piece with the panel.

[0211] 64. Set of panels according to any of the preceding clauses, wherein the fourth locking element comprises a separate insert provided in a recess of the first coupling part and / or wherein the third locking element comprises a separate insert provided in a recess of the second coupling part, wherein said insert comprises a locking part which, when coupling adjacent panels, arrives in a locking position by at least partially performing a lateral movement wherein the strip co-acts and / or faces an opposing coupling part of an adjacent panel, and wherein the insert or at least a portion thereof is elastically deformable and / or displaceable in order to allow said lateral movement.

[0212] 65. Set of panels according to clause 64, wherein, in case the insert makes part of third locking element, the insert defines at least a part of at least one inclined third contact surface configured to co-act with and / or face the fourth contact surface of an adjacent panel; and / or wherein, in case the insert makes part of fourth locking element, the insert defines at least a part of at least one inclined fourth contact surface configured to co-act with and / or face the third contact surface of an adjacent panel.

[0213] 66. Set of panels according to any of the preceding clauses, wherein a transition between the downward flank and an upper side of the downward groove defines aconcave vertex, and wherein, preferably, a centreline of the third locking element substantially coincides with a centreline of said concave vertex.

[0214] 67. Set of panels according to any of the preceding clauses, wherein the upper side of the upward tongue is downwardly inclined in a direction away from the upward flank.

[0215] 68. Set of panels according to any of the preceding clauses, wherein the substantially complete upper side of the upward tongue is flat.

[0216] 69. Set of panels according to any of the preceding clauses, wherein the upper side of the downward groove is downwardly inclined in a direction towards the downward flank.

[0217] 70. Set of panels according to any of the preceding clauses, wherein the third locking element is located inward compared to an upper part of the side of the downward tongue facing away from the downward flank.

[0218] 71. Set of panels according to any of the preceding clauses, wherein the minimum thickness of the second coupling part, in particular the bridge thereof, is less than half the total thickness of the panel.

[0219] 72. Set of panels according to any of the preceding clauses, wherein each panel is oblong and / or rectangular, wherein said first pair of edges is formed by short edges of the panel.

[0220] 73. Set of panels according to clause 72, wherein said second pair of edges is formed by long edges of the panel.

[0221] 74. Set of panels according to any of the preceding clauses, wherein a panel thickness of each panel is 6 mm or less, preferably 5 mm or less, more preferably 4 mm or less.

[0222] 75. Set of panels according to any of the preceding clauses, wherein each panel comprises a decorative top structure applied, directly or indirectly, onto the corelayer, wherein said decorative top structure comprises at least one decorative layer and at least one translucent or transparent wear layer situated above the decorative layer.

[0223] 76. Covering, in particular a decorative covering, such as a decorative floor covering or decorative wall covering, comprising a plurality of interconnected panels of the set of panels according to any of the preceding clauses.

[0224] The invention will be further elucidated by several illustrative examples and with reference to the appended non-limitative figures, in which:

[0225] Figure 1 shows, schematically, a decorative panel as may be included in an embodiment of a set of panels according to the present invention;

[0226] Figure 2 shows a cross section of a decorative panel as may be included in an embodiment of a set of panels according to the present invention, along line A-A as indicated in figure 1 ;

[0227] Figures 3A and 3B show coupling parts, in coupled state and an intermediate state, respectively, of adjacent panels as may be included in an embodiment of a set of panels according to the present invention;

[0228] Figure 4 shows alternative coupling parts of adjacent panels as may be included in a set of panels;

[0229] Figure 5 shows further alternative coupling parts of adjacent panels as may be included in a set of panels;

[0230] Figure 6 shows a cross section of a decorative panel as may be included in a set of panels according to the present invention, along line B-B as indicated in figure 1; Figures 7a and 7b show coupling parts of adjacent panels as may be included in an embodiment of a set of panels according to the present invention and according to Figure 6;

[0231] Figures 8a and 8b show alternative coupling parts of adjacent panels as may be included in an embodiment of a set of panels according to the present invention, which could e.g. replace the coupling parts shown in Figures 6 and 7a-7b; and Figure 9 shows further alternative coupling parts of adjacent panels as may be included in an embodiment of a set of panels according to the present invention, and, which could e.g. replace the coupling parts shown in Figures 6 and 7a-7b; Figures 10a and 10b show further alternative coupling parts of adjacent panels as may be included in an embodiment of a set of panels according to the presentinvention, which could e.g. replace the coupling parts shown in Figures 6 and 7a-7b; and

[0232] Figures 11 a and 11 b show alternative coupling parts of adjacent panels as may be included in an embodiment of a set of panels according to the present invention, which could e.g. replace the coupling parts shown in Figures 3a-3b.

[0233] Within these figures, similar reference numbers correspond to similar or equivalent elements or features.

[0234] Figure 1 shows, schematically, a decorative panel 1 according to the present invention. In this embodiment, panel 1 comprises a substrate 106, a decorative top structure 105 applied onto substrate 106, and a backing layer 107 applied below substrate 106. Instead of substrate 106, other core layers may also be used.

[0235] Decorative top structure 105 may itself be made of several layers, such as one or more decorative layers and a translucent or transparent wear layer situated above the decorative layer. In this embodiment, structure 105 is applied directly on top of substrate 106. In some embodiments, structure 105 is applied indirectly, for example in embodiments where further layers are arranged in between substrate 106 and structure 105. Decorative top structure 105 and backing layer 107 are both optional. The thickness of panel 1 may be 6 mm or less, preferably 5 mm or less, more preferably 4 mm or less. The panel 1 , in this embodiment, is oblong or rectangular and accordingly has four side edges 101, 102, 103, 104. Decorative panels may also come in other shapes. Each side edge is provided with a corresponding coupling part: first side edge 101 is provided with a first coupling part 10, second side edge 102 is provided with a second coupling part 20, and third side edge 103 is provided with a third coupling part 30. And, while not shown in figure 1, fourth side edge 104 is provided with a fourth coupling part 40.

[0236] In the panel 1 , one pair of opposite side edges is formed by first side edge 101 and second side edge 102. These side edges may also be referred to as the short edges of panel 1. Another pair of opposite side edges is formed by third side edge 103 and fourth side edge 104. These side edges may also be referred to as the long edges of panel 1. The panel 1 has a length extending longitudinally along line B-B, and a width extending transversally along line A-A. The plane of the decorative panel is hence determined by the combination of lines A-A and B-B.The first coupling part 10 can be coupled to the second coupling part 20 and vice-versa. This allows for the same or similar panels from the set of decorative panels to be arranged adjacent and coupled to one another along their first side edge 101 and second side edge 102, respectively. The third coupling part 30 can be coupled the fourth coupling part 40 and vice-versa. This allows for the same or similar panels from the set of decorative panels to be arranged adjacent and coupled to one another along their third side edge 103 and fourth side edge 104, respectively. Multiple panels 1 may together form a set of panels and / or may be interconnected to form a covering, in particular a decorative covering, such as a decorative floor covering or decorative wall covering.

[0237] Figure 2 shows a cross section of panel 1 along line A-A, panel 1 again comprising substrate 106, decorative top structure 105 and backing layer 107, as well as a fourth coupling part 40 and a third coupling part 30. Fourth coupling part 40 is formed by a sideward tongue 41 , an downward flank 42, and a downward groove 43 therein between. Sideward tongue 41 is attached to the rest of panel 1 via upper bridge 44. Third coupling part 30 is formed by a lower lip 34, an upper lip 32, and a sideward groove 33 therein between. Lower lip 34 comprises an upward locking element 31. An upper surface 442 of lower lip 34 defines a bottom surface of sideward groove 33. This minimum thickness is ideally less than half the total thickness of the panel.

[0238] Figure 3a shows coupling parts 30C and 40D of adjacent panels, in a coupled position. Upper tongue 32 co-acts with sideward tongue 41 at contact surfaces 32-10 and 41-10. Sideward groove 33 accommodates part of sideward tongue 41. Upward surface 342-1 of lower lip 34 supports downwardly protruding lower surface 412-1 of sideward tongue 41 at contact C, close to the co-acting proximal sides 313 and 413. Here, contact C is positioned at the deepest point of lower lip 34, adjacent to proximal surface 313. Similarly, contact C is positioned at a lowest or farthest downward protruding surface 412-1, adjacent to proximal surface 413. To accommodate this downward protruding surface 412-1 of sideward tongue 41, the indentation or deepened portion of lower lip 34, of which lower surface 342-1 forms the bottom surface, is slightly wider than said downward protruding surface 412-1. A distal space is enclosed by the adjacent panels, more specifically between distal surface 311 and downward flank 42. Embodiments are also conceivable for thesecoupling parts wherein the lower side of sideward tongue 41 is formed by a single surface, and / or wherein the upper side 342 of lower lip 34 is formed by a single surface, similar to figure 5.

[0239] In figure 3b, the third and fourth coupling parts are shown in an intermediate position. Therein, the panels are essentially parallel. Lower surfacer 412-1 of sideward tongue 41 is supported by upper side 312 of upward locking element 31. A distal end of sideward tongue 41 is located within groove 33, below upper lip 32. In this intermediate position, upper tongue 32 co-acts with sideward tongue 41 via sliding surfaces 32-11 and 41-11, respectively. Said sliding surfaces assist in coupling the adjacent panels 1 A and 1 B. With respect to contact surface 32-10, sliding surface 32-11 is further upwardly inclined, away from groove 33. With respect to contact surface 41-10, sliding surface 41-11 is further downwardly inclined, toward a terminal portion of sideward tongue 41. Sliding surfaces 32-11 and 41-11 in figures 3A and 3B are parallel. Embodiments are also conceivable in which they are at an angle. In such embodiments, preferably 10 degrees or less. Panels having coupling parts arrangeable in such an intermediate position are easier to couple. Such panels can remain substantially parallel while being arranged in the intermediate position. This, in practise, is more convenient. From this intermediate position, panels 1A and 1B can be moved closer together. Sliding surface 32-11 urges sideward tongue 41 , specifically via sliding surface 41-11, diagonally downward and towards a terminal end of groove 33.

[0240] The height of locking element 31 and accordingly the upper surface of groove 43 has to be fine tuned with respect to the position of sliding surface 41-11. Sideward tongue 41 is at least partially facilitated in groove 33 as in the intermediate position, when considered in height, the sliding surfaces 32-11 and 41-11 at least partially overlap. That is, the upper end of sliding surface 32-11 is higher than the lower end of sliding surface 41-11.

[0241] Coupling parts 30C and 40D can further facilitate moving from the intermediate position to the coupled position in a number of ways. In some embodiments, material of either coupling part 30C, 40D is compressed. For example, upper surface 312 may be indented by the contacting lower surface 412-1. Locally the height of locking element 31 is then temporarily decreased. In another example,lower surface 412-1 may be indented by the contacting upper surface 312. Locally, the height of upward tongue is then temporarily decreased. Either type of compression allows sideward tongue 41 to pass over locking element 31 while the sliding surfaces 32-11 and 41-11 remain in contact and the panels 1A and 1B remain substantially parallel.

[0242] In some embodiments, upper lip 32 or lower lip 34 bends away from sideward tongue 41 to temporarily increase the dimensions of groove 33, to allow for sideward tongue 41 to be arranged therein. In case lower lip 34 bends away, this ideally combined with a compressible surface. It is not necessary, however. Only a relatively small bend for this type of lower lip is necessary to allow for lower surface 412-1 to pass over upper surface 312.

[0243] These ways in which coupling parts can be configured to move from the intermediate position to the coupled position can also be combined in further embodiments.

[0244] Figure 4 shows a third coupling part 30A of one panel 1 A in a coupled state with a fourth coupling part 40B of another panel 1B, adjacent thereto. Specifically, the coupled state shown here is one that may occur between the long edges of two adjacent panels. This coupling locks panels 1A and 1B both in a direction parallel to a plane defined by the panels, as well as in a direction perpendicular to said plane. The third and fourth coupling parts may be referred to as angling-in profiles. The coupled state shown here may for example be achieved by placing panel 1A on the floor, arranging panel 1 B at a non-zero angle with respect to panel 1 A, arranging sideward tongue 41 in sideward groove 33, and lowering and / or angling panel 1B or more specifically Fourth coupling part 40B, into panel 1A or more specifically Third coupling part 30A. The skilled person will appreciate that the coupling can also be achieved on non-horizontal surfaces such as walls.

[0245] An upper part of upper lip 32 contacts and / or co-acts with an upper part of a distal side 411 of sideward tongue 41 , forming an upper joint contact zone. This contact zone, or, more specifically the point where this contact surface ends at the upper side of the panels 1 A and 1 B, is sometimes referred to simply as the joint. As shown here, said joint defines a vertical plane VPL along the long edge of panels 1A and 1B.While the figures show flat upper ends for the upper joint contact zones, other types of upper ends are also conceivable. That is, an upper end part of the upper side of upper lip 32 and an upper end part of distal side 411 may each inclined outward, inclining away from VPL, and thereby form a bevel. These upper end parts may also have stepped indent portions, stepping away from VPL and thereby form a grout line. Bevels and grout lines can be present in any upper joint contact zone. In this embodiment, the upper part of upper lip 32 and the upper part of distal side 411 both coincide with vertical plane VPL and thus form a contact surface. Said contact surfaces allows the coupled panels 1A and 1B to better distribute forces amongst each other that are exerted on an upper side of one of them, for example by a user. When coupled, the panels 1 A and 1 B may then better absorb said forces, therefore improving stability.

[0246] Embodiments are also conceivable in which the upper part of upper lip 32 and the upper part of distal side 411 enclose an angle. For example of 5 degrees or less. For such example, one of the upper part of the upper lip 32 and the upper part of distal side 411 may then still coincide with vertical plane VPL, in which case the other is then inclined with respect to said vertical plane VPL. A proximal side 413 of sideward tongue 41 contacts a proximal side 313 of upward tongue 31. Proximal side 413 and proximal side 313 each incline outward. That is, away from downward flank 42 and upper lip 32, respectively. Coupling parts with this property are sometimes referred to as ‘open’ profiles. A distal space is enclosed between a distal side 311 of sideward tongue 31 and downward flank 42. In some embodiments, said distal space extends upward, to what is enclosed between an upper surface 312 of upward locking element 31 and a lower surface of upper bridge 44, and preferably beyond that, to where proximal side 313 co-acts with proximal side 413.

[0247] In this embodiments, upper surface 312 is mostly flat and downwardly inclined in a direction away from upper lip 32. Embodiments are also conceivable in which upper surface 312 inclines upward away from upper lip 32.

[0248] In a coupled state, an upper surface 342 of lower lip 34 supports a lower surface 412 of sideward tongue 41 at contact C. Because upper surface 342 and lower surface 412 enclose an angle and / or are not parallel, an intermediate space is enclosed by sideward tongue 41 and lower lip 34. Said enclosed angle may be in the range of 0 and 10 degrees, not including 0. Specifically, said angle may be lessthan 5 degrees, preferably less than 3 degrees, and / or larger than zero. In the intermediate space, moving away from contact C, the distance between upper surface 342 and lower surface 412, also referred to as the height of the intermediate space, increases.

[0249] Sideward tongue 41 and / or lower lip 34 may be conceptually divided into sections by vertical planes, similar to the downward tongue as shown in figures 7a and 9. Vertical plane VP1 may indicate a distal end of lower surface 412 or a proximal end of upper surface 342. Vertical plane VP5 may indicate a proximal end of lower surface 412 or a distal end of upper surface 342. Vertical planes VP2, VP3, and VP4 may divide the distance between VP1 and VP2 into four. Vertical plane VP3 may divide lower surface 412 and / or upper surface 342 in half.

[0250] The angle between said sides allows for sideward tongue 41 and lower lip 34 to only partially and / or selectively come into contact. This limits the effect of possible deviations in the coupling parts, for example due to manufacturing errors, on the position of contact C. Also, the intermediate space reduces the impact of deviations in the dimensions of sideward tongue 41 and lower lip 34, for example due to warping of the panel and / or heat contraction or retraction, on the mutual positioning of panels 1A and 1B.

[0251] The skilled person will appreciate that contact C can be or at least can be described as a contact point, and can also be a contact surface. For example, where contact C can initially be relatively small with respect to the lengths of sides 342 and 412, it is conceivable that external forces, overtime, deform downward sideward tongue 41 and / or lower lip 34, increasing the surface of contact C. In embodiments in which contact C is a contact surface, said contact surface may therefore also be of varying lengths - preferably being less than half of the width of the lower surface and / or lowest surface of the downward tongue.

[0252] In some embodiments, for example the one shown in figure 8, contact C is positioned at a location closer to upper lip 32 than to proximal side 313 of upward locking element 31. For such embodiments, it may be said that the height of the enclosed intermediate space increases towards upward locking element 31.

[0253] In figures 3a and 4b, contact C is positioned at a location closer to proximal side 313 of upward locking element 31 than to upper lip 32. Specifically, here contact Cis positioned at a distal end of upper surface 342-1 and / or a proximal end of lower surface 412-1. The intermediate space formed here extends from contact C away from upward locking element 31 and / or downward flank 42, and towards upper lip 32. Considered as a point, contact C may be positioned between VP5 and VP3, preferably between VP5 and VP4. Considered as a surface, contact C may extend between VP5 and VP4, between VP5 and VP3, or between VP5 and VP2.

[0254] Coupling parts with any of these properties are sometimes referred to as profiles with Tear support’ or ‘heel support.’

[0255] In different embodiments, for example like the one shown in figure 5, contact C may be positioned at a proximal end of upper surface 342 and / or a distal end of lower surface 412. The intermediate space extends from contact C towards upward locking element 31 and / or downward flank 42, and away from upper lip 32.

[0256] Considered as a point, contact C may be positioned between VP1 and VP3, preferably between VP1 and VP2. Considered as a surface, contact C may extend between VP1 and VP2, between VP1 and VP3, or between VP1 and VP4.

[0257] Coupling parts with any of these properties are sometimes referred to as profiles with ‘front support’ or ‘toe support.’

[0258] In the embodiments shown in figures 2 and 5, the side of sideward tongue 41 that faces lower lip 34 is planar and is substantially formed by lower surface 412.

[0259] Similarly, the opposing side, that of lower lip 34, facing sideward tongue 41 is also planar and is substantially formed by upper surface 342.

[0260] In the embodiments shown in figures 3a, 3b, 4, the side of sideward tongue 41 that faces lower lip 34 is formed by multiple surfaces. Specifically, lowest surface 412-1, intermediate surface 412-2, and indented surface 412-3. Similarly, the side of lower lip 34 that faces sideward tongue 41 is also formed by multiple surfaces.

[0261] Specifically, upper surface 342-3, intermediate surface 342-2, and indented surface 342-1. Here, indented surface 342-1 provides heel support to lowest surface 212-1. Embodiments are conceivable for each of the mentioned types of support, between each pair of opposing surfaces.

[0262] The coupling parts shown in figures 2-5 are typically applied at the long edges of the panel(s). The coupling parts shown in these figures 2-5 are interchangeable in the sense that instead of the coupling part shown in figure 2, the coupling part ofone of figures 3a5 can be used, that instead of the coupling part shown in figure 3a, the coupling part of one of figures 2, 3b-5 can be used, etcetera.

[0263] Figure 6 shows a cross section of panel 1 along line B-B, panel 1 again comprising substrate 106, decorative surface structure 105 and backing layer 107, as well as second coupling part 20 and first coupling part 10.

[0264] Second coupling part 20 is formed by a downward tongue 21, a downward flank 22 lying at a distance of downward tongue 21, and a downward groove 23 therein between. Downward tongue 21 is attached to the rest of panel 1 via upper bridge 24. Downward tongue 21 is preferably at least half a panel thick. An S-shaped locking element 21-1 is provided on a distal side of downward tongue 21, facing away from the rest of panel 1 , more specifically away from the downward flank 22. A locking element 22-1 , in this embodiment in the form of a recess, is provided on downward flank 22.

[0265] First coupling part 10 is formed by an upward tongue 11, an upward flank 12 lying at a distance of upward tongue 11, and an upward groove 13 therein between. Upward tongue 11 is attached to the rest of panel 1 via lower bridge 14. An upper surface of lower bridge 14 defines a bottom surface of upward groove 13. A locking element 11-1, in this embodiment in the form of a bulge, is provided on a distal side of upward tongue 11 , facing away from the rest of panel 1 , more specifically away from the upward flank 12. An S-shaped locking element 12-1 is provided on upward flank 12.

[0266] Positioning of locking elements 21-1 and 12-1 affects the ease of coupling and locking of adjacent panels. In some embodiments, the height of locking element 21- 1 and / or locking element 12-1 may be situated between and including 0.8 mm and 2 mm. The panel thickness is at least two times the height of the third locking element and / or the fourth locking element and preferably less than 4 times the height of the third locking element and / or the fourth locking element.

[0267] Any pair of locking elements may include a bulge-recess combination for which, when co-acting, the bulge is at least partially accommodated in said recess. In some embodiments, the recess is oversized with respect to the bulge. This allowsdefining where the bulge and recess come into contact more accurately. It may also provide for a space to be present between an extremity of the bulge and an extremity of the recess, as seen in a plane defined by each panel 1A. A space between said extremities allows the coupling parts to absorb changes in the dimensions of the panel in said plane, for example due to panel 1 A or 1 B expanding and / or contracting. Embodiments are conceivable in which locking element 11-1 is embodied by a recess and in which locking element 22-1 is embodied by a bulge.

[0268] Figure 7a shows a first coupling part 10A of one panel 1A in a coupled state with a second coupling part 20B of another panel 1 B, adjacent thereto. Specifically, the coupled state shown here is one that may occur between the short edges of two adjacent panels. This coupling locks panels 1A and 1B both in a direction parallel to a plane defined by the panels, as well as in a direction perpendicular to said plane.

[0269] Downward tongue 21 is received by upward groove 13 and upward tongue 11 is received by downward groove 23. Locking element 21-1 co-acts with locking element 12-1 and locking element 22-1 co-acts with locking element 11-1.

[0270] The first and second coupling parts have what are also known as drop-lock profiles. The coupled state shown here may for example be achieved by placing panel 1 A on the floor, arranging second coupling part 20B of panel 1B at least partially above first coupling part 10A of panel 1A, and with an at least partially horizontal movement placing downward tongue 21 into upward groove 13. The skilled person will appreciate that the coupling can also be achieved on non-horizontal surfaces such as walls, for which cases the coupling movement can be more generally described as one at least partially perpendicular to the plane of panel 1 A and / or plane 1B.

[0271] An upper part of upward flank 12 contacts and / or co-acts with an upper part of a distal side 211 of downward tongue 21 , forming an upper joint contact zone. This contact zone, or, more specifically the point where this contact surface ends at the upper side of the panels 1 A and 1 B, is sometimes referred to as the joint. As shown here, the upper joint contact zone defines a vertical plane VPs along the short edge of panels 1A and 1B.In some embodiments, when coupling parts 10A, 20B are coupled, one or both of these coupling parts 10A, 20B bends, warps or otherwise deforms. Elasticity or resilience of the deformed coupling part(s) 10A, 20B urges it back into its original shape. Consequently, the deformed coupling part(s) affect a tension onto the part it is coupled with. This effect is sometimes referred to as pre-tension. In embodiments, pretension may be achieved by use of a slightly oversized downward tongue 21 and / or a slightly undersized upward groove 13. This causes proximal surface 113 to enact a force on downward tongue 21, pushing distal side 211 against upward flank 12, resulting in closer and / or tighter joint.

[0272] In this embodiment, the upper part of upward flank 12 and the upper part of distal side 211 both coincide with vertical plane VPs and thus form a contact surface. Said contact surfaces allows the coupled panels 1 A and 1 B to better distribute forces amongst each other that are exerted on an upper side of one of them, for example by a user. When coupled, the panels 1 A and 1 B may then better absorb said forces, therefore improving stability. Embodiments are also conceivable in which the upper part of upward flank 12 and the upper part of distal side 211 enclose an angle. For example of 5 degrees or less. For such example, one of the upper part of the upward flank 12 and the upper part of distal side 211 may then still coincide with vertical plane VPS, in which case the latter then runs inclined with respect to said vertical plane VPs towards the former. A lower part of upward flank 12 is, preferably continuously, curved to form S-shaped locking element 12-1. Similarly, a lower part of distal side 211 is, preferably continuously, curved to form S-shaped locking element 21-1.

[0273] The locking elements 21-1 and 12-1 are provided with contact surfaces 21-10 and 12-10, respectively. When panels 1A and 1B are coupled, said surfaces contact each other and allow for the co-acting of the locking elements. The contact surfaces 21-10 and 12-10 are both arranged in their respective coupling part such that, in coupled state they are below a horizontal plane HP, parallel to a plane defined by panel 1 A or 1 B and including a highest point of upward tongue 11.

[0274] The contact surfaces 21-10 and 12-10 together define a tangent line R1 which runs upwardly in the direction away from upward flank 12 and towards downward tongue 21. Said line R1 forms an angle A1 with respect to the plane defined by the respective panel 1A and 1B. Contact surface 21-10 inclines inward, or toward therest of downward tongue 21. Contact surface 12-10 inclines outward, or away from the rest of upward flank 12. Angle A1 lies in the range of 10 to 80 degrees, preferably 20 to 70 degrees. More preferably, angle A1 is around or less than 45 degrees or around 60 degrees. Alternatively said, contact surfaces 21-10 and 12-10 are upwardly inclined towards VPS.

[0275] Embodiments are also conceivable in which contact surfaces 21-10 and 12-10, while still facing each other, are entirely positioned at a distance from each other. By ensuring there is at least some space between said facing contact surfaces 21-10 and 12-10, there is less risk of there being continuous tension of the first and second coupling parts. Such continuous tension risks damage to these coupling parts. At the same time, as said surfaces still face each other, when panels 1 A and 1B are coupled and a force is exerted on either of them, said contact surfaces 21-10 and 12-10 may still come into contact with each other and provide horizontal and / or vertical locking for which locking elements 21-1 and 12-1 are intended.

[0276] Embodiments are also conceivable in which contact surfaces 21-10 and 12-10 are not parallel. For example, Contact surface 21-10 may form an angle with respect to a plane defined by panel 1B between 35 and 45 degrees. Contact surface 12-10 may form an angle with respect to a plane defined by panel 1 A between 25 and 35 degrees. The angle of contact surface 21-10 is preferably larger than that of contact surface 12-10. In some embodiments, locking elements 21-1 and 12-1 are not S-shaped and formed by a single bulge-recess pair, similar to the locking elements 22-1 and 11-1. In such embodiments, locking element 12-1 may be a recess and locking element 21-1 may be a bulge, or vice-versa.

[0277] In other embodiments, S-shaped locking elements 21-1 and 12-1 are formed by two bulge-recess pairs: locking element 21-1 comprises a bulge 21-11 and a recess 21-12 arranged above said bulge 21-11. Locking element 12-1 comprises a recess 12-11 and a bulge 12-12 arranged above said recess 12-11.

[0278] Contact surface 21-10 may be an upper surface of bulge 21-11 and Contact surface 12-10 may be an upper surface of recess 12-11. Therefore, bulge 21-11 and recess 12-11 may each be said to be entirely situated below horizontal plane HP. Said horizontal plane HP then intersects bulge 12-12 and recess 21-12, whichin turn may be said to be situated at least partially above and / or at least partially below said plane.

[0279] The curvature of the locking elements 12-1 and 21-1 assists in smooth coupling and locking of the coupling parts. In some embodiments, the curvature of locking element 12-1 increases from bulge 12-12, ideally an upper part or even upper end thereof, to contact surface 12-10 and decreases from contact surface 12-10 to recess 12-11, ideally a lower part or even a lower end thereof. Alternatively phrased, a curvatures of bulge 12-12 and recess 12-11 are each less than a curvature of the intermediate Contact surface 12-10. In some embodiments, the curvature of locking element 21-1 increases from recess 21-12, ideally an upper part or even upper end thereof, to contact surface 21-10 and further increases from contact surface 21-10 to bulge 21-11, ideally a lower part or even a lower end thereof. Alternatively phrased, a curvatures of recess 21-12 is less than a curvature of the lower situated Contact surface 21-10, which is less than a curvature of the even lower situated bulge 21-11.

[0280] Vertical plane (“VPS”) intersects S-shaped locking element 12-1. Recess 12-11 and / or bulge 12-12 may be intersected by and situated at both sides of VPS. VPs does not intersect S-shaped locking element 21-1. Locking element 21-1 is located inward, compared to the upper part of distal side 211 based on which VPSis defined. Bulge 21-11 and recess 21-12 are each situated at a single side of VPS. The maximum width of recess 21-12, in view of VPs, exceeds the maximum width of bulge 12-12. These aspects of the positioning of said locking elements each contributes to a more smooth drop-lock when panels 1 A and 1 B are coupled. Below the upper joint contact zone, an upper joint space and a lower joint space are enclosed. These joint spaces are separated by and adjacent to contact surfaces 21-10 and 12-10. In some embodiments, there is just one or there are more than two, such as three, joint spaces are enclosed. Joint spaces provide space for deviations in the dimensions of coupling parts, which may occur due to processing errors in the production process.

[0281] A distal space is enclosed between a distal side 111 of upward tongue 11 and downward flank 22. In some embodiments, said distal space extends upward, to what is enclosed between an upper surface 112 of upward tongue 11 and a lower surface 242 of upper bridge 24, and preferably beyond that, to where proximal side213 co-acts with proximal side 113. As indicated in figure 7a, distal side 111 may be considered divided one to two substantially vertical side parts 111-1 and 111-2 by locking element 11-1 which is arranged in between.

[0282] In coupled state, a contact surface 11-10 of locking element 11-1 faces and / or coacts a contact surface 22-10 of locking element 22-1. In some embodiments, contact surfaces 11-10 and 22-10 face each other but, at least when panels 1A and 1B are coupled and otherwise at rest, do not come into contact. Contact surfaces 11-10 and 22-10 divide distal space into an upper distal space and a lower distal space.

[0283] In this embodiment, upper surface 112 is mostly flat and downwardly inclined in a direction away from upward flank 12. Embodiments are also conceivable in which upper surface 112 is horizontal or inclines upward away from upward flank 12. Lower surface 242 defines an upper side of downward groove 23. In this embodiment, lower surface 242 is also mostly flat, corresponding to opposing upper surface 112. While said surfaces are preferably at least similar this is not necessary. Lower surface 242 upwardly inclines in a direction away from downward flank 22. Embodiments are also conceivable in which lower surface 242 inclines downward away from downward flank 22.

[0284] In a coupled state, an upper surface 142 of lower bridge 14 supports a lower surface 212 of downward tongue 21 at contact C. Because upper surface 142 and lower surface 212 are not parallel and / or enclose an angle, an intermediate space is enclosed by downward tongue 21 and lower bridge 14. Said enclosed angle may be in the range of 0 and 10 degrees, not including 0. Specifically, said angle may be less than 5 degrees, preferably less than 3 degrees, and / or larger than zero. In the intermediate space, moving away from contact C, the distance between upper surface 142 and lower surface 212, also referred to as the height of the intermediate space, increases.

[0285] In the embodiments shown in figures 7a-10b, lower surface 212 transitions into proximal side 213 with a smooth curve. Similarly, upper surface 142 transitions into proximal side 113 with a smooth curve. The curvature of the transition from lower surface 212 to proximal side 213 is smaller than the curvature of the transition from upper surface 142 to proximal side 113. This relation provides for the upwardlycurved end portion of intermediate space Si. By providing this upwardly curved end portion, the coupling parts become more robust for manufacturing errors in proximal sides 113, 213 - more specifically the angles at which they are machined. These angles are particularly relevant in coupling parts in which the contact surface between said proximal surfaces 113, 213 is relatively large with respect to other contact points, zones or surfaces between said coupling parts.

[0286] In the embodiment shown in figure 7a-7b, the side of downward tongue 21 that faces lower bridge 14 is planar and substantially formed by lower surface 212. Similarly, the opposing side, that of lower bridge 14, is also planar and substantially formed by upper surface 142.

[0287] Similar to the differences between the embodiments shown in figures 4 and 5, embodiments are conceivable in which the side of downward tongue 21 that faces lower bridge 14 is formed by multiple surfaces. Ideally, the side of lower bridge 14 is then also formed by multiple surfaces. Embodiments are conceivable for each of the mentioned types of support, between each pair of opposing surfaces.

[0288] Downward tongue 21 and / or lower bridge 14 may be conceptually divided into sections by vertical planes as shown in figures 7a-9.

[0289] Vertical plane VP1 may indicate a distal end of lower surface 212 or a proximal end of upper surface 142. Vertical plane VP5 may indicate a proximal end of lower surface 212 or a distal end of upper surface 142. Vertical planes VP2, VP3, and VP4 may divide the distance between VP1 and VP2 into four. Vertical plane VP3 may divide lower surface 212 and / or upper surface 142 in half.

[0290] The angle between said sides allows for downward tongue 21 and lower bridge 14 to only partially and / or selectively come into contact. This limits the effect of possible deviations in the coupling parts, for example due to manufacturing errors, on the position of contact C. Also, the intermediate space reduces the impact of deviations in the dimensions of downward tongue 21 and lower bridge 14, for example due to warping of the panel and / or heat contraction or retraction, on the mutual positioning of panels 1 A and 1 B.The skilled person will appreciate that contact C can be or at least can be described as a contact point, and can also be a contact surface. For example, where contact C can initially be relatively small with respect to the lengths of sides 142 and 212, it is conceivable that external forces, overtime, deform downward tongue 21 or lower bridge 14, increasing the surface of contact C. In embodiments in which contact C is a contact surface, said contact surface may therefore also be of varying lengths.

[0291] In some embodiments, for example the ones shown in figures 9, 10a, 10b, contact C is positioned at a location closer to upward flank 12 than to proximal side 113 of upward tongue 11. For such embodiments, it may be said that the height of the enclosed intermediate space increases towards the upward tongue.

[0292] Contact C may be positioned at a proximal end of upper surface 142 and / or a distal end of lower surface 212. The intermediate space extends from contact C towards upward tongue 11 and / or downward flank 22, and away from upward flank 12. Considered as a point, contact C may be positioned between VP1 and VP3, preferably between VP1 and VP2. Considered as a surface, contact C may extend between VP1 and VP2, between VP1 and VP3, or between VP1 and VP4.

[0293] Coupling parts with any of these properties are sometimes referred to as profiles with ‘front support’ or ‘toe support.’

[0294] In a different embodiment, for example the ones shown in figures 7a, 7b, 8a, 8b, contact C is positioned at a location closer to proximal side 113 of upward tongue 11 than to upward flank 12. Specifically, here contact C is positioned at a distal end of upper surface 142 and / or a proximal end of lower surface 212. The intermediate space formed here extends from contact C away from upward tongue 11 and / or downward flank 22, and towards upward flank 12. Considered as a point, contact C may be positioned between VP5 and VP3, preferably between VP5 and VP4.

[0295] Considered as a surface, contact C may extend between VP5 and VP4, between VP5 and VP3, or between VP5 and VP2. Coupling parts with any of these properties are sometimes referred to as profiles with Tear support’ or ‘heel support.’

[0296] The position of contact C may also be described with respect to vertical planes defined by locking element 12-1. In some embodiments, contact C is positioned at a distance of such vertical planes, and / or in between said vertical planes andupward tongue 11. Both upward tongue 11 and downward tongue 21 have proximal sides, being their sides that face the upward flank 12 and downward flank 22, respectively. When panels 1A and 1B are coupled, a proximal side 213 of downward tongue 21 contacts a proximal side 113 of upward tongue 11. This assists in the co-acting of the coupling parts. Said proximal sides define a tangent line R2 running at an angle A2 with respect to the plane defined by the panels 1 A and 1 B. Angle A2 may lie in the range 0 to 80 degrees or 20 to 70 degrees. More specifically, angle A2 may be around 30 degrees or around 15 degrees. Angle A2 is ideally larger than the aforementioned angle A1.

[0297] In some embodiments with heel support, more than one intermediate space may be enclosed by coupling parts 10A and 20B. In some embodiments, intermediates spaces may be enclosed on both sides of contact C. Embodiments are also conceivable in which such multiple intermediate spaces are enclosed on both sides of a contact C between coupling parts 30C and 40D, in the embodiments shown in figures 3a-5.

[0298] In some embodiments with heel support, one of the intermediate spaces adjoins lower joint space Sij. Part of the resulting combined space between contact C and contact surfaces 12-10 and 21-10 extends below a substantial part of downward tongue 21. Expansion of downward tongue 21 is urged downward by the inclined contact surfaces 12-10 and 21-10 and accommodated by the combined lower joint space Sij and intermediate space Si. Contact C may be considered a pivot point to the displacement of distal end 211 relative to the rest of coupling part 21. This reduces the risk of expansion of downward tongue 21 , which may for example be the result of moist and / or heat affecting the panel 1 B, adversely affecting the joint between adjacent panels 1A and 1B.

[0299] In some embodiments, for example the ones shown in figures 7a, 7b, 8b, proximal side 213 and proximal side 113 each incline inward. That is, toward the downward flank 22 and upward flank 12, respectively. Coupling parts with this property are sometimes referred to as ‘closed’ profiles. In some embodiments, for example the one shown in figure 8a, proximal side 213 and proximal side 113 each incline outward. That is, away from the downward flank 22 and upward flank 12, respectively. Coupling parts with this property are sometimes referred to as ‘open’ profiles.In some embodiments, for example the ones shown in figures 7a, 7b, lower surface 212 and upper surface 142 may be substantially planar and either may be horizontal. In such embodiments, the height of the intermediate space and / or the distance between lower surface 212 and upper surface 142 linearly increase with increased distance from contact C. Embodiments are also conceivable in which upper surface 142 is substantially horizontal and / or parallel to the plane defined by panel 1 A. In embodiments where one of lower surface 212 and upper surface 142 is horizontal, the other preferably runs in an inclined fashion, typically inclined planar and / or curved, fashion. In some embodiments, for example the ones shown in figures 8a, 8b, an upper surface 142 is curved, more specifically concave.

[0300] Embodiments are also conceivable in which a lower surface 212 of downward tongue 21 is curved, more specifically concave.

[0301] In earlier discussed embodiments, locking elements are embodied by bulge-recess pairs. In bulge-recess pairs, opposing surfaces of coupling parts of adjacent panels are provided with either a bulge, as a protrusion which extends generally in a direction parallel to the plane of panel 1, and a recess. Bulges are generally made in one piece with panel 1, usually with substrate 106. During coupling and / or locking of adjacent panels, the bulge and / or part of the coupling part outlining the recess deform, for example be being warped and / or compressed.

[0302] The above described configurations, wherein the coupling parts make integral part of the panel, is also referred to as a single piece configuration.

[0303] Instead of bulge-recess pairs, locking elements may also be implemented as insertrecess pairs. Such embodiments are shown in figures 10A and 10B. Therein, opposing sides of coupling parts 10A and 20B of adjacent panels 1A, 1B are each provided with a recess 12-15, 21-13. In recess 12-15 of first coupling part 10A, an insert 12-14 is arranged. In this coupled state, said insert 12-14 is also at least partially arranged in recess 21-13 in second coupling part 20B.

[0304] Said insert 12-14, at least when at rest, forms the protrusion which extends generally in a direction parallel to the plane of panel 1. Earlier mentioned features of bulges, such as their size and shape, are also applicable to such inserts.Such inserts may be shaped as strips and may include an elastically deformable and / or displaceable portion 12-13. When coupling adjacent panels 1A and 1B, instead of or in addition to the abovementioned warping and / or compression, said portion 12-13 allows for a lateral movement of insert 12-14, in which insert 12-14 at least partially recedes into recess 12-15 in which it was placed. When adjacent panels 1A, 1B are arranged in the desired mutual positions, insert 12-14, more specifically said portion 12-13, reforms and allows for an opposite lateral movement of insert 12-14, arranging an outer side of insert 12-14 at least partially in opposing recess 21-13. Insert 12-14 may be used to implement locking element 12-1 and defines contact surface 12-10. An insert may also be used to implement locking element 11-1 and define contact surface 11-10. The coupling parts 10A and 20B in figure 10a have a closed profile and the coupling parts 10A and 20B in figure 10b have an open profile. This configuration, wherein use is made of a separate insert 12-14, is also referred to as a dual piece configuration.

[0305] Figures 11 a and 11 b show alternative coupling parts of adjacent panels as may be included in an embodiment of a set of panels according to the present invention, which could e.g. replace the coupling parts shown in Figures 3a-3b.

[0306] In figure 11a, the third and fourth coupling parts are shown in an intermediate position. Therein, the panels are essentially parallel. The panel thickness in this embodiment is 4 or 5 mm. The lower side of sideward tongue 41 is supported at a first inclined lower intermediate contact surface 412-4 by a second inclined lower intermediate contact surface 312-1 at an upper side of upward locking element 31. Said first inclined lower intermediate contact surface 412-4 and said second inclined lower intermediate contact surface 312-1 together define a lower intermediate contact zone Cli having a width of approximately 0.03 mm. The first inclined lower intermediate contact surface 412-4 encloses an angle of approximately 4 degrees with a plane defined by each panel, which is smaller than an angle of approximately 10 degrees enclosed by said second inclined lower intermediate contact surface 312-1 and a plane defined by each panel. This angular difference of approximately 6 degrees ensures that the panels contact each other at predefined locations only, preventing unintended contact at other locations which could impede the coupling process. The small width of the lower intermediatecontact zone Cli reduces friction during coupling, ensures a predictable contact location, and facilitates easier installation of the panels.

[0307] Similarly, the upper side of sideward tongue 41 co-acts at a first inclined upper intermediate contact surface 411-1 with a second inclined upper intermediate contact surface 321-1 at a lower side of upper lip 32. Said first inclined upper intermediate contact surface 411-1 and said second inclined upper intermediate contact surface 321-1 together define an upper intermediate contact zone Cui having a width of approximately 0.03 mm. The first inclined upper intermediate contact surface 411-1 encloses an angle of approximately 35 degrees with a plane defined by each panel, which is larger than an angle of approximately 30 degrees enclosed by said second inclined upper intermediate contact surface 321-1 and a plane defined by each panel. This angular difference of approximately 5 degrees guides the sideward tongue 41 into the groove 33 in a controlled manner and provides stability during the intermediate position. The small width of the upper intermediate contact zone Cui ensures that the coupling parts can slide relative to each other with minimal friction.

[0308] With a panel thickness of 4 or 5 mm, the width of each intermediate contact zone Cli, Cui (0.03 mm) is less than 1% of the panel thickness and well below the preferred maximum of 0.08 mm, more preferably preferred maximum of 0.06 mm, which significantly reduces the mutual contact area between the coupling profiles during the coupling process, thereby minimizing frictional forces and facilitating smoother coupling of adjacent panels. Alternative preferred values for the width of the intermediate contact zones include 0.04 mm and 0.05 mm, which are also less than 0.06 mm and provide similar advantages in terms of reduced friction and improved coupling. Alternative (or additional) preferred values for the width of the intermediate contact zones include 0.04 mm and 0.05 mm, which are also less than 0.06 mm and provide similar advantages in terms of reduced friction and improved coupling. The small width of the intermediate contact zones Cli, Cui provides multiple advantages: facilitated coupling requiring less installation force, facilitated uncoupling for repair or replacement of individual panels, reduced material stress on the coupling parts resulting in longer lifespan and reduced risk of damage, reduced friction minimizing heat generation during coupling, accommodation of manufacturing tolerances as small contact zones are less sensitive to dimensional variations, consistent coupling behaviour with predictable contact locations leadingto consistent coupling force requirements, and reduced risk of creaking noises as less surface contact means less potential for friction-induced sounds during use.

[0309] In the intermediate position shown in figure 11a, spaces S1 and S2 are enclosed between the coupling parts. A first space S1 is enclosed between a distal end of sideward tongue 41 and a portion of upper lip 32 facing groove 33. A second space S2 is enclosed between a lower portion of sideward tongue 41 and an upper portion of lower lip 34, said second space S2 being located between the lower intermediate contact zone Cli and the upper intermediate contact zone Cui. These spaces S1, S2 secure that the panels contact each other at the predefined intermediate contact zones Cli and Cui only, preventing unintended contact at other locations. Furthermore, the spaces S1, S2 accommodate manufacturing tolerances and allow for thermal expansion and contraction of the panels without affecting the coupling. The first space S1 has a generally triangular shape in cross-sectional view, while the second space S2 has a more elongated shape extending along the lower side of sideward tongue 41.

[0310] The curvature of the third coupling part 30 and the fourth coupling part 40 in figures 11 a and 11 b differ from each other at specific locations. At the location of the lower intermediate contact zone Cli, the curvature of the first inclined lower intermediate contact surface 412-4 of sideward tongue 41 is smaller than the curvature of the second inclined lower intermediate contact surface 312-1 of upward locking element 31. At the location of the upper intermediate contact zone Cui, the curvature of the first inclined upper intermediate contact surface 411-1 of sideward tongue 41 is larger than the curvature of the second inclined upper intermediate contact surface 321-1 of upper lip 32. These curvature differences contribute to the point-like contact configuration at the intermediate contact zones Cli, Cui, ensure smooth sliding movement during coupling, and reduce wear on the coupling parts. The curvature differences also assist in guiding the sideward tongue 41 into groove 33 during the coupling process.

[0311] Figure 11b shows the coupled state of the third and fourth coupling parts. Sideward tongue 41 is further inserted into groove 33 compared to the intermediate position shown in figure 11a. In this coupled state, the lower side of sideward tongue 41 is supported by an upper side of lower lip 34 at contact C. Contact C is positioned at adeepened portion of lower lip 34, adjacent to upward locking element 31. Upper lip 32 co-acts with sideward tongue 41 at contact surfaces 32-10 and 41-10, respectively. In the coupled state, the lower side of sideward tongue 41 and the upper side of lower lip 34 mutually enclose an intermediate space Si, wherein a height of said intermediate space Si increases towards upward locking element 31. A distal space Sd is enclosed between distal surface 311 and downward flank 42. The intermediate space Si in the coupled state has a generally banana-shaped cross-section, with the narrowest portion at contact C and the widest portion adjacent to upward locking element 31. The intermediate space Si and distal space Sd allow for expansion of the panels during normal use without affecting the mutual positioning of the panels. This provides the advantage that temperature variations and humidity changes do not adversely affect the coupling between adjacent panels.

[0312] The coupling parts shown in figures 6-1 Ob are typically applied at the short edges of the panel(s). The coupling parts shown in these figures 6-1 On are interchangeable in the sense that instead of the coupling part shown in figure 6, the coupling part of one of figures 7a-10b can be used, that instead of the coupling part shown in figure 7a, the coupling part of one of figures 6, 7b-10b can be used, etcetera. Figures 11 a and 11 b show alternative coupling parts of adjacent panels as may be included in an embodiment of a set of panels according to the present invention, which could e.g. replace the coupling parts shown in Figures 3a-3b.

[0313] It will be apparent that the invention is not limited to the working examples shown and described herein, but that numerous variants are possible within the scope of the attached claims that will be obvious to a person skilled in the art.

[0314] The above-described inventive concepts are illustrated by several illustrative embodiments. It is conceivable that individual inventive concepts may be applied without, in so doing, also applying other details of the described example. It is not necessary to elaborate on examples of all conceivable combinations of the abovedescribed inventive concepts, as a person skilled in the art will understand numerous inventive concepts can be (re)combined in order to arrive at a specific application.The ordinal numbers used in this document, like “first”, “second”, and “third” are used only for identification purposes. Hence, the use of the expressions “third locking element” and “second locking element” does therefore not necessarily require the co-presence of a “first locking element”. The “upper surface” may be replaced by the “upper side” and vice versa. It is imaginable though that “the upper side” is defined by a plurality of “upper surfaces”. Likewise, the “lower surface” may be replaced by the “lower side” and vice versa. It is imaginable though that “the lower side” is defined by a plurality of “lower surfaces”. The panels according to the invention may also be referred to as tiles. By "complementary" coupling parts (or locking elements) is meant that these coupling parts (or locking elements) can cooperate with each other. However, to this end, the complementary coupling parts (or locking elements) do not necessarily have to have complementary forms.

[0315] Expressions like “horizontal”, “vertical”, and “inclined” are relative expressions with respect to the plane defined by the panel, which is considered as horizontal plane. By locking in "vertical direction" is therefore meant locking in a direction perpendicular to the plane of the panel. By locking in "horizontal direction" is therefore meant locking in a direction parallel to or falling together with the plane defined by the panel(s). In case in this document reference is made to a “panel”, which expression may be replaced by “floor tile” or “floor panel”, “decorative floor panel”, “tile”, “wall tile”, “decorative wall panel”, “ceiling tile”, “decorative ceiling panel”, “decorative covering tile”, etcetera. It is possible that the panel comprises a combination either of the first and second locking elements or of the third and fourth locking elements, thus effectively leaving out one of the pairs of locking elements.

[0316] The verb “comprise” and conjugations thereof used in this patent publication are understood to mean not only “comprise”, but are also understood to mean the phrases “contain”, “substantially consist of”, “formed by” and conjugations thereof.

Claims

1. Claims1. A set of panels, in particular decorative panels, such as decorative floor panels or decorative wall panels, each panel comprising:• at least one core layer,• at least one optional first coupling part and at least one optional second coupling part provided at different panel edges, preferably at a first pair of opposite panel edges,wherein said optional first coupling part comprises:o an upward tongue,o at least one upward flank lying at a distance from the upward tongue, o an upward groove formed in between the upward tongue and the upward flank, wherein the upward groove is adapted to receive at least a part of a downward tongue of a second coupling part of an adjacent panel, and wherein the upward tongue is connected to the upward flank via a lower bridge, wherein a substantially horizontal and / or planar upper side of said lower bridge defines at least a part of a bottom side of the upward groove configured to support said downward tongue of an adjacent panel, ando at least one optional first locking element provided at a distal side of the upward tongue facing away from the upward flank, wherein said optional first locking element comprises at least one first contact surface,o at least one fourth locking element provided at the upward flank, wherein said fourth locking element comprises at least one inclined fourth contact surface,wherein said optional second coupling part comprises:o a downward tongue having a lower side which is preferably at least partially planar,o at least one downward flank lying at a distance from the downward tongue,o a downward groove formed in between the downward tongue and the downward flank, wherein the downward groove is adapted to receive at least a part of an upward tongue of a first coupling part of an adjacent panel,o at least one optional second locking element provided at the downward flank, wherein said optional second locking element comprises at least one second contact surface configured to co-act with and / or face the first contact surface of an adjacent panel, o at least one third locking element provided at a distal side of the downward tongue facing away from the downward flank, wherein said third locking element comprises at least one inclined third contact surface configured to co-act with and / or face the fourth contact surface of an adjacent panel,wherein the third contact surface and the fourth contact surface are entirely located below a horizontal plane (HP) defined by a highest point of the upward tongue, and running parallel to a plane defined by the panel, andwherein, in coupled state of said first coupling part and said second coupling part of adjacent panels,- a proximal side of the upward tongue facing towards the upward flank coacts with a proximal side of the downward tongue facing the downward flank of an adjacent panel,- the upper side of said lower bridge supports a part of the lower side of the downward tongue of an adjacent panel, at a lower contact zone which is preferably located closer to the proximal side of the upward tongue than to the upward flank,- a part of the upward flank co-acts with a part of a distal side of the downward tongue of the adjacent panel,wherein, in coupled state, adjacent panels enclose:- at least one distal space between the distal side of the upward tongue and the facing downward flank,- at least one intermediate space between the upper side of the lower bridge and the facing lower side of the downward tongue, preferably at both sides of the lower contact zone, and- at least one joint space between the upward flank and the distal side of the downward tongue;wherein each panel further comprises at least one third coupling part and at least one fourth coupling part provided at different panel edges, preferably at a second pair of opposite panel edges, wherein said third coupling part and saidfourth coupling part are configured to be coupled by means of a lateral snap-in movement,wherein the fourth coupling part comprises:o a sideward tongue extending in a direction substantially parallel to the upper side of the core layer,o at least one second downward flank lying at a distance from the sideward tongue, ando a second downward groove formed between the sideward tongue and the second downward flank; andwherein the third coupling part comprises a third groove configured for accommodating at least a part of the sideward tongue of the fourth coupling part of an adjacent panel, said third groove being defined by an upper lip and a lower lip, wherein said lower lip is provided with an upward locking element,wherein the third coupling part and fourth coupling part are designed such that the fourth coupling part of a first panel can be positioned in an intermediate position with respect to the third coupling part of an adjacent panel, wherein, in said intermediate position:the planes defined by the panels in the intermediate state run in parallel, - wherein a lower side of the sideward tongue is supported at a first inclined lower intermediate contact surface by a second inclined lower intermediate contact surface at an upper side of the upward locking element, wherein said first inclined lower intermediate contact surface encloses an angle with a plane defined by each panel which is smaller than an angle enclosed by said second inclined lower intermediate contact surface and a plane defined by each panel, and wherein said first inclined lower intermediate contact surface and said second inclined lower intermediate contact surface together define a lower intermediate contact zone having a width measured in a plane defined by the panels which is less than 3%, preferably less than 2%, of the panel thickness and / or having a width of less than 0.08 mm, preferably less than 0.06 mm,- while a part of the sideward tongue is located within the third groove and below the upper lip, such that an upper side of the sideward tongue co-acts at a first inclined upper intermediate contact surface with a second inclined upper intermediate contact surface at a lower side of the upper lip, wherein said first inclined upper intermediate contact surface encloses an angle witha plane defined by each panel which is larger than an angle enclosed by said second inclined upper intermediate contact surface and a plane defined by each panel, and wherein said first inclined upper intermediate contact surface and said second inclined upper intermediate contact surface together define an upper intermediate contact zone having a width measured in a plane defined by the panels which is less than 3%, preferably less than 2%, of the panel thickness and / or having a width of less than 0.08 mm, preferably less than 0.06 mm,- ; andwherein, in coupled state of said third coupling part and said fourth coupling part of adjacent panels:- at least a part of the sideward tongue is inserted into the third groove of an adjacent panel, and wherein at least a part of the upward locking element of said second panel is inserted into the second downward groove of said first panel,- a proximal side of the upward locking element facing towards the third groove co-acts with a proximal side of the downward tongue facing the downward flank of an adjacent panel to prevent drifting apart of said panels, - the upper side of said lower lip supports a part of the lower side of the sideward tongue of an adjacent panel, at a lower contact zone which is preferably located adjacent to the proximal side of the upward locking element,- at least a part of an end surface of the upper lip co-acts with a part of a distal side of the fourth coupling part of the adjacent panel,wherein, in coupled state of said third coupling part and said fourth coupling part, adjacent panels enclose:- at least one distal space between the distal side of the lower lip and a facing downward flank of the fourth coupling part,- at least one intermediate space between the upper side of the lower lip and the facing lower side of the sideward tongue at at least one side of said lower contact zone, and- at least one joint space between the third coupling part, in particular the upper lip and / or the third groove, and a distal side of the sideward tongue.

2. Set of panels according to any of the preceding claims, wherein, in the intermediate position of adjacent panels, an upper surface of the sideward tongue co-acts with a lower side of the upper lip.

3. Set of panels according to claim 2, wherein the upper surface of the sideward tongue configured to co-act with the lower side of the upper lip of an adjacent panel is at least partially downwardly inclined towards a terminal portion of the sideward tongue, wherein said inclined contact surface is preferably is configured as sliding surface to slide the sideward tongue into the third groove of an adjacent panel.

4. Set of panels according to any of the preceding claims, wherein a front contact surface located at the lower side of the upper lip configured to co-act with the sideward tongue of an adjacent panel is downwardly inclined towards a terminal portion of the third groove, wherein said inclined contact surface is preferably configured as sliding surface to facilitate sliding the sideward tongue into the third groove.

5. Set of panels according to any of the preceding claims, wherein, in the intermediate position, the shortest vertical distance, perpendicular to a plane defined by the panels, between the front contact surfaces, defined by the co-action between the upper lip and the sideward tongue, and the rear contact surfaces, defined by the co-action between the proximal side of the upward locking element and the sideward tongue, is preferably 20-30% of the panel thickness and / or between 0.8 and 1.5 mm.

6. Set of panels according to any of the preceding claims, wherein the vertical distance, perpendicular to a plane defined by the panels, for displacing the fourth coupling part from the intermediate state into the coupled state is preferably 10-50% of the panel thickness and / or between 0.3 and 1.0 mm.

7. Set of panels according to any of the preceding claims, wherein the upper side of the lower lip has a deepened portion which defines the lowest point or lowest zone of the lower lip, which deepened portion preferably has a horizontal surface, wherein said deepened portion is preferably situated directly adjacent tothe upward locking element, and wherein said deepened portion is configured to support the sideward tongue in the coupled state.

8. Set of panels according to any of the preceding claims, wherein the lower side of the sideward tongue has a downwardly protruding portion which defines the lowest point or lowest zone of the sideward tongue, wherein said downwardly protruding portion is preferably situated directly adjacent to a proximal side of the sideward tongue acting as locking surface, and wherein a lower side of said downwardly protruding portion is preferably at least partially inclined, and / or wherein a lower side of said downwardly protruding portion preferably defines the first inclined lower intermediate contact surface.

9. Set of panels according to claim 7 and 8, wherein, in the coupled state, the downwardly protruding portion of the sideward tongue is supported by the deepened portion lower lip, wherein the width of the deepened portion of the lower lip preferably exceeds the width of the downwardly protruding portion of the sideward tongue, and wherein, in the coupled state, an upper side of the deepened portion and a lower side of the downwardly protruding portion preferably mutually enclose an angle.

10. Set of panels according to any of the preceding claims, wherein, in the coupled state of adjacent panels, the third coupling part, preferably only, co-acts with the fourth coupling part at spaced contact zones, wherein a first contact zone is located at a side surface of the upper lip, a second contact zone is located at the lower side of the upper lip, an optional third contact zone is located at the upper side of the lower lip located underneath the upper lip, a fourth contact zone is located at the upper side of the lower lip located at a horizontal distance from the upper lip, and a fifth contact zone which is located at a proximal side of the upward locking element, wherein the fourth and the fifth contact zone may optionally form a single zone.

11. Set of panels according to any of the preceding claims, wherein, in coupled state of adjacent panels, the lower side of the sideward tongue and the upper side of the lower lip mutually enclose an intermediate space, wherein a height of said intermediate space increases towards the upward locking element.

12. Set of panels according to any of the preceding claims, wherein the third coupling part and / or the fourth coupling part is configured to deform when displacing the fourth coupling part of a panel from the intermediate position to the coupled state.

13. Set of panels according to any of the preceding claims, wherein the third coupling part and / or the fourth coupling part are configured to allow a substantially linear translation of the sideward tongue of a panel into the third groove of an adjacent panel, when displacing the fourth coupling part of a panel from the intermediate position to the coupled state.

14. Set of panels according to any of the preceding claims, wherein the upper side of the sideward tongue comprises a, preferably planar, proximal upper surface and a, preferably planar, distal upper surface, wherein the distal upper surface is more inclined with respect to the plane defined by the panel than the proximal upper surface of the sideward tongue.

15. Set of panels according to any of the preceding claims, wherein the lower side of the upper lip comprises a, preferably planar, proximal lower surface and a, preferably planar, distal lower surface, wherein the distal lower surface is more inclined with respect to the plane defined by the panel than the proximal lower surface of the upper lip.

16. Set of panels according to claim 14 and claim 15, wherein the inclination of the, preferably planar, proximal upper surface of the sideward tongue is preferably substantially identical to the inclination of the, preferably planar, proximal lower surface of the upper lip, wherein said surfaces are configured not to co-act with each other in coupled state of adjacent panel; and / or wherein the inclination of the, preferably planar, distal upper surface of the sideward tongue is preferably substantially identical to the inclination of the, preferably planar, distal lower surface of the lower lip, wherein said surfaces are configured to co-act with each other in coupled state of adjacent panel.

17. Set of panels according to any of the preceding claims, wherein a lower side of the upper lip comprises a concavely shaped lower surface connecting to a distal side of the upper lip.

18. Set of panels according to any of the preceding claims, wherein, in coupled state of said panels, the panels mutually enclose both a lower joint space, positioned below and adjacent to co-acting and / or facing said contact surfaces of the lower side of the upper lip and the sideward tongue; as well as an upper joint space, positioned above and adjacent said co-acting and / or facing said contact surfaces.

19. Set of panels according to claim 18, wherein the upper joint space is situated at both sides of a vertical plane (VP) defined a distal end of the third coupling part and / or vertical coupling part.

20. Set of panels according to any of the preceding claims, wherein said first inclined lower intermediate contact surface encloses an angle with a plane defined by each panel, which angle is situated between 1 and 8 degrees, preferably between 2 and 6 degrees.

21. Set of panels according to any of the preceding claims, wherein said second inclined lower intermediate contact surface encloses an angle with a plane defined by each panel, which angle is situated between 5 and 15 degrees, preferably between 8 and 12 degrees.

22. Set of panels according to any of the preceding claims, wherein said first inclined upper intermediate contact surface encloses an angle with a plane defined by each panel, which angle is situated between 30 and 40 degrees, preferably between 32 and 38 degrees.

23. Set of panels according to any of the preceding claims, wherein said second inclined upper intermediate contact surface encloses an angle with a plane defined by each panel, which angle is situated between 25 and 35 degrees, preferably between 27 and 33 degrees.

24. Set of panels according to any of the preceding claims, wherein the width of the lower intermediate contact zone is 0.05 mm or less.

25. Set of panels according to any of the preceding claims, wherein the width of the upper intermediate contact zone is 0.05 mm or less.

26. Set of panels according to any of the preceding claims, wherein a panel thickness of each panel is 6 mm or less, preferably 5 mm or less, more preferably 4 mm or less.

27. Set of panels according to any of the preceding claims, wherein the lower side of the downward tongue is a substantially horizontal and / or planar.

28. Set of panels according to any of the preceding claims, wherein the lower side of the downward tongue and the upper side of the bridge mutually enclose an angle, preferably an angle less than 5 degrees, more preferably less than 3 degrees.

29. Set of panels according to any of the preceding claims, wherein at least one contact surface part of one surface of the lower side of the downward tongue and the upper side of the bridge runs horizontally and / or runs in inclined fashion, and wherein at least one opposing contact surface part of the lower side of the downward tongue and the upper side of the bridge runs in inclined fashion, wherein, coupled state of said panels, a height of the intermediate space preferably increases towards the upward flank.

30. Set of panels according to any of the preceding claims, wherein a shortest distance (HD4) between the fourth locking element and the upward tongue, measured in the plane defined by each panel, is at least 3 times the width of the contact surface formed between the lower side of the downward tongue and the upper side of the bridge in coupled state of adjacent panels.

31. Set of panels according to any of the preceding claims, wherein the contact surface formed between a lower side of the downward tongue and the upper side ofthe bridge in coupled state of adjacent panels is positioned at a distance of one or more virtual vertical planes defined by the fourth locking element.

32. Set of panels according to any of the preceding claims, wherein the contact surface formed between a lower side of the downward tongue and the upper side of the bridge is less than half of the width of the lower side and / or lowest surface of the downward tongue.

33. Set of panels according to any of the preceding claims, wherein a shortest distance (HD4) between the fourth locking element and the upward tongue, measured in the plane defined by each panel, is smaller than a thickness of each panel.

34. Set of panels according to any of the preceding claims, wherein width of the lower side and / or the width lowest surface of the downward tongue is at least half of a thickness of each panel.

35. Set of panels according to any of the preceding claims, wherein the fourth locking element comprises a recess and the third locking element comprises a bulge, wherein, in coupled state of adjacent panels, the bulge is at least partially accommodated in said recess.

36. Set of panels according to claim 35, wherein at least a part of an upper side of the fourth locking element defines said at least one inclined fourth contact surface, and wherein at least a part of an upper side of the third locking element defines said at least one inclined third contact surface.

37. Set of panels according to any of claims 35-36, wherein the recess of the fourth locking element is oversized with respect to the bulge of the third locking element.

38. Set of panels according to any claims 35-37, wherein, in coupled state of said panels, a space is present between an extremity of the bulge of the third locking element and an extremity of the recess of the fourth locking element, in particular as seen in a plane defined by each panel.

39. Set of panels according to any of claims 35-38, wherein said at least one inclined third contact surface and the plane defined by each panel encloses a first angle, preferably between 35 and 45 degrees, and wherein said at least one inclined fourth contact surface and the plane defined by each panel encloses a second angle, preferably between 25 and 35 degrees, wherein the first angle is larger than the second angle.

40. Set of panels according to any of claims 35-39, wherein said inclined fourth contact surface is upwardly inclined towards a vertical plane intersecting the upward tongue, said vertical plane being perpendicular to the plane defined by each panel, and wherein said inclined third contact surface is upwardly inclined in a direction towards the downward tongue.

41. Set of panels according to any of claims 35-40, wherein the recess of the fourth locking element and the bulge of the third locking element are entirely situated below the horizontal plane (HP) defined by the highest point of the upward tongue.

42. Set of panels according to any of claims 35-41 , wherein the upward flank and a part of a distal side of the downward tongue of the adjacent panel together define an upper joint contact zone, wherein a vertical plane (VP) defined by said upper joint contact zone intersects the recess of the fourth locking element, such that said recess of the fourth locking element is situated at both sides of the vertical plane (VP), and wherein the bulge of the third locking element is preferably situated at a single side of said vertical plane (VP).

43. Set of panels according to any of claims 35-42, wherein the fourth locking element comprises a bulge located above the recess of said fourth locking element, and wherein the third locking element comprises a recess located above the bulge of said third locking element, wherein, in coupled state of adjacent panels, the bulge of the fourth locking element is at least partially accommodated in the recess of the third locking element.

44. Set of panels according to claim 43, wherein the recess of the third locking element is oversized with respect to the bulge of the fourth locking element.

45. Set of panels according to claim 43 or 44, wherein, in coupled state of said panels, a space is present between an extremity of the bulge of the fourth locking element and an extremity of the recess of the third locking element, in particular as seen in a plane defined by each panel.

46. Set of panels according to any of claims 35-45, wherein the upward flank and a part of a distal side of the downward tongue of the adjacent panel together define an upper joint contact zone and an intersecting vertical plane (VP), wherein the maximum width of the recess of the third locking element in view of the vertical plane (VP) exceeds the maximum width of the of bulge fourth locking element in view of the vertical plane (VP).

47. Set of panels according to any of claims 35-46, wherein the upward flank and a part of a distal side of the downward tongue of the adjacent panel together define an upper joint contact zone, wherein a vertical plane (VP) defined by said upper joint contact zone intersects the recess of the fourth locking element, such that said bulge of the fourth locking element is situated at both sides of the vertical plane (VP), and wherein the recess of the third locking element is preferably situated at a single side of said vertical plane (VP).

48. Set of panels according to any of claims 35-47, wherein each of the bulge of the fourth locking element and the recess of the third locking element is situated at least partially above the horizontal plane (HP) defined by the highest point of the upward tongue.

49. Set of panels according to any of the preceding claims, wherein the fourth locking element and / or the third locking element are continuously curved.

50. Set of panels according to any of the preceding claims, wherein at least a part of each of the fourth locking element and the third locking element are S-shaped.

51. Set of panels according to any of claims 35-48 and any of claims 49-50, wherein the bulge and lower located recess of the fourth locking element define a curved shape, wherein the curvature of said shape increases from the bulge,preferably an upper part of the bulge, towards the fourth contact surface and decreases from the fourth contact surface towards the recess, preferably a lower part of the recess.

52. Set of panels according to any of claims 35-48 and any of claims 49-51 , wherein a curvature of the bulge of the fourth locking element and a curvature of the lower located recess of the fourth locking element are each less than a curvature of the fourth locking surface.

53. Set of panels according to any of claims 35-48 and any of claims 49-52, wherein the recess and lower located bulge of the third locking element define a curved shape, wherein the curvature of said shape increases from the recess, preferably an upper part of the recess, towards the third contact surface and further increases from the third contact surface towards the bulge, preferably a lower part of the bulge.

54. Set of panels according to any of claims 35-48 and any of claims 49-53, wherein a curvature of the recess of the third locking element is less than a curvature of the third contact surface and wherein both said curvatures are less than a curvature of the lower located bulge of the third locking element.

55. Set of panels according to any of the preceding claims, wherein the upward flank and a part of a distal side of the downward tongue of the adjacent panel together define an upper joint contact zone, and together defining a vertical plane (VP), wherein at the upper joint contact zone the upward flank and said part of the distal side of the downward tongue mutually enclose an angle, preferably of 5 degrees or less, and wherein at the upper joint contact zone the upward flank preferably coincides with said vertical plane (VP) and said part of the distal side of the downward tongue is preferably inclined with respect to said vertical plane (VP).

56. Set of panels according to any of the preceding claims, wherein, in coupled state of said panels, the third contact surface and fourth contact surface are entirely positioned at a distance from each other.

57. Set of panels according to any of the preceding claims, wherein the panel thickness is at least two times the height of the third locking element and / or the fourth locking element and preferably less than 4 times the height of the third locking element and / or the fourth locking element.

58. Set of panels according to any of the preceding claims, wherein the height of the third locking element and / or the fourth locking element is situated between and including 0.8 and 2 mm.

59. Set of panels according to any of the preceding claims, wherein, in coupled state of said panels, the panels mutually enclose both a lower distal space, positioned below and adjacent to said co-acting and / or facing first and second contact surfaces, and an upper distal space, positioned above and adjacent to said co-acting and / or facing first and second contact surfaces60. Set of panels according to claim 59, wherein said upper distal space extends to said proximal side of the upward tongue co-acting with said proximal side of the downward tongue.

61. Set of panels according to any of the preceding claims, wherein the first and second contact surfaces are positioned below the upper side of the lower bridge.

62. Set of panels according to any of the preceding claims, wherein the first locking element comprises a bulge and the second locking element comprises a recess configured to at least partially accommodate said bulge of the first locking element of an adjacent panel.

63. Set of panels according to one of the preceding claims, wherein the side of the upward tongue facing away from the upward flank comprises two substantially vertical side parts, wherein the first locking element is situated in between said substantially vertical side parts64. Set of panels according to any of the preceding claims, wherein, in coupled state of said panels, the panels mutually enclose both a lower joint space, positioned below and adjacent to co-acting and / or facing said third and fourthcontact surfaces, and an upper joint space, positioned above and adjacent to coacting and / or facing said third and fourth contact surfaces.

65. Set of panels according to any of the preceding claims, wherein the first coupling part and the second coupling part are configured to be coupled by lowering and / or angling the second coupling part of a panel into the first coupling part of an adjacent panel.

66. Set of panels according to any of the preceding claims, wherein in coupled state of said panels, the first coupling part and the co-acting second coupling part of said panels lock the panel both in a direction parallel to the plane defined by the panels as well as in a direction perpendicular to said plane defined by the panels.

67. Set of panels according to any of the preceding claims, wherein at least a part of the proximal side of the upward tongue is upwardly inclined towards the upward flank, and wherein at least a part of the proximal side of the downward tongue is downwardly inclined towards the downward flank.

68. Set of panels according to any of the preceding claims, wherein at least a part of the proximal side of the upward tongue is upwardly inclined away from the upward flank, and wherein at least a part of the proximal side of the downward tongue is downwardly inclined away from the downward flank.

69. Set of panels according to any of the preceding claims, wherein, in coupled state of adjacent panels, the third and fourth contact surfaces define a first tangent line (R1) which runs upwardly in the direction towards the downward tongue, and wherein this tangent line (R1) forms a first angle (A1) with the plane defined by the panels which preferably is smaller than or equal to 45 degrees; and wherein the coacting proximal side of the upward tongue and the proximal side of the downward tongue define a second tangent line (R2) which wherein this second tangent line (R2) forms a second angle (A2) with the plane defined by the panels which larger than the first angle.

70. Set of panels according to any of the preceding claims, wherein at least a part of the third locking element and / or at least a part of the fourth locking elementare made in one piece with the core layer, and wherein, preferably, the first coupling part and second coupling part are made in one piece with the panel.

71. Set of panels according to any of the preceding claims, wherein the fourth locking element comprises a separate insert provided in a recess of the first coupling part and / or wherein the third locking element comprises a separate insert provided in a recess of the second coupling part, wherein said insert comprises a locking part which, when coupling adjacent panels, arrives in a locking position by at least partially performing a lateral movement wherein the strip co-acts and / or faces an opposing coupling part of an adjacent panel, and wherein the insert or at least a portion thereof is elastically deformable and / or displaceable in order to allow said lateral movement.

72. Set of panels according to claim 71 , wherein, in case the insert makes part of third locking element, the insert defines at least a part of at least one inclined third contact surface configured to co-act with and / or face the fourth contact surface of an adjacent panel; and / or wherein, in case the insert makes part of fourth locking element, the insert defines at least a part of at least one inclined fourth contact surface configured to co-act with and / or face the third contact surface of an adjacent panel.

73. Set of panels according to any of the preceding claims, wherein a transition between the downward flank and an upper side of the downward groove defines a concave vertex, and wherein, preferably, a centreline of the third locking element substantially coincides with a centreline of said concave vertex.

74. Set of panels according to any of the preceding claims, wherein the upper side of the upward tongue is downwardly inclined in a direction away from the upward flank.

75. Set of panels according to any of the preceding claims, wherein the substantially complete upper side of the upward tongue is flat.

76. Set of panels according to any of the preceding claims, wherein the upper side of the downward groove is downwardly inclined in a direction towards the downward flank.

77. Set of panels according to any of the preceding claims, wherein the third locking element is located inward compared to an upper part of the side of the downward tongue facing away from the downward flank.

78. Set of panels according to any of the preceding claims, wherein the minimum thickness of the second coupling part, in particular the bridge thereof, is less than half the total thickness of the panel.

79. Set of panels according to any of the preceding claims, wherein each panel is oblong and / or rectangular, wherein said first pair of edges is formed by short edges of the panel.

80. Set of panels according to claim 79, wherein said second pair of edges is formed by long edges of the panel.

81. Set of panels according to any of the preceding claims, wherein each panel comprises a decorative top structure applied, directly or indirectly, onto the core layer, wherein said decorative top structure comprises at least one decorative layer and at least one translucent or transparent wear layer situated above the decorative layer.

82. Covering, in particular a decorative covering, such as a decorative floor covering or decorative wall covering, comprising a plurality of interconnected panels of the set of panels according to any of the preceding claims.

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