EP3581731B1 - Panel - Google Patents

Description

The invention relates to a panel with a panel core, a panel top side with a wear layer, a panel bottom side and pairs of edges provided on opposite panel edges, wherein at least a first pair of edges is provided with complementary locking means, of which a locking means on a groove side of the edge pair acts as a locking groove and the complementary locking means on one tongue side of the pair of edges is designed as a locking spring, which fits together with the locking groove in a form-fitting manner so that panels of the same type can be locked to one another, the locking spring of a first panel being attachable to the locking groove of a second panel of the same type when this panel is inclined and then by a rotating Joining movement of the panels relative to each other, both panels can be locked together in a form-fitting manner, so that the achievable form-fitting is a moving apart of the locked panels elkanten counteracts in a direction that is in the plane of the locked panels and at the same time perpendicular to the locked panel edges, wherein the locking spring has a contact surface on its spring top side, which is directed towards the top side of the panel (the surface normal of the contact surface is to the top side of the panel directed), and wherein the upper groove wall has a contact surface designed to mate with the contact surface of the tongue top in the interlocked condition of two panels.

A generic panel is from EP 3 087 230 B1 known. Its overall thickness is relatively small. It can be 2 mm or less than a total thickness of 4 mm. The panel edges of the known panel are designed in such a way that a corresponding profiling of the panel edges can be produced at all. The known panel is also provided with a panel core made of a carrier material which has a matrix material comprising plastic. A proportion of solid material is provided therein. According to one embodiment, the solid material is a mineral filler, for example talc.

The invention is based in particular on the fact that the panel core has a carrier material comprising a matrix and at least one filler provided therein in the form of particles, with the carrier material being able to have a certain degree of brittleness. The filler is preferably a mineral filler, such as a phyllosilicate.

The design of the known panel has weaknesses in terms of the stability of the panel edges. In the prior art, the free end of the locking spring has particular weaknesses; it can suffer damage from external mechanical influences, in particular before it is laid. In particular, when the carrier material has a structure with a certain degree of brittleness, weaknesses occur in the known panel.

The object of the invention is to propose a panel that benefits from a shape of the panel core that improves stability.

From the WO 2018/087637 A1 discloses a floorboard comprising a substrate made of thermoplastic material, a decoration provided thereon and at least one pair of opposite edges, coupling parts which are at least partially realized from the substrate, the coupling parts enabling mechanical locking between two such floorboards, characterized in that the The substrate comprises a rigid substrate layer of thermoplastic material and a glass fiber layer is present in the floor panel.

the WO 2012/142986 A1 proposes a floor element which has a carrier board with a top-side, multi-layer wear coating. The functional coating comprises a damping layer, a decorative layer and a wearing layer, with the wearing layer consisting of a thermoplastic based on polyethylene terephthalate (PET) and/or polypropylene (PP). The damping layer preferably consists of a highly compressed granular material, in particular cork. A polyurethane-based lacquer seal is provided on the upper side of the wear layer.

According to the invention, the object is achieved in that the front of the locking spring is rounded tangentially to the contact surface, the rounding forms a free end of the locking spring that is round in cross section, a round transition to the underside of the spring is created, the rounding of the locking spring has a radius , equal to or greater than the distal extent of the contact surface, and that the rounding of the locking spring merges into an outwardly curved contour that extends along the underside of the spring. The convex contour can be a radius.

The size of the radius of the rounding is preferably in a range of 10%-20% of the total thickness of the panel, particularly preferably in the range of 10%-15% of this total thickness.

The cross section of the free end of the locking spring is formed as a relatively large radius. This measure has improved the stability of the panel edge equipped with the locking spring. Even if the panel core has a carrier material that tends to be brittle, the proposed panel turns out to be more stable than the prior art. In particular, it has been shown that with a panel core made of a carrier material with a certain brittleness, better cohesion of the entire structure is achieved. Without being bound to this theory, it appears to the inventor that a special feature arises when plate-shaped mineral particles, for example made of talc, are used. During production, the plate-shaped mineral particles are initially randomly embedded in a matrix. During production they are in a granulate. However, if a bed of granules is heated and formed into a plate in a continuous process, then a certain alignment of the plate-shaped particles appears to occur, predominantly in a direction parallel to the plane of the plate. This may be due to some alignment of the plate-like particles occurring under the action of heat and some pressure applied in a direction perpendicular to the plane of the plate.

The invention is preferably intended for panels which have an overall thickness in the range from 2 to 6 mm, more preferably the overall thickness is between 2.5 to 5 mm and particularly preferably between 2.8 and 4 mm.

The locking groove expediently has a groove base which is round in cross-section and connects to the contact surface of the upper groove wall, the groove base having a radius which is the same size or greater than the distal extent of the contact surface. More preferably, this groove base is adapted to the front curve of the locking spring in such a way that in the locked state there is a small gap between the groove base and the curve of the locking spring. This ensures that when two panels are locked, there is a closed joint above the locking tongue.

A further improvement of the panel can be achieved if the contact surface is inclined downwards in the distal direction, the angle of inclination of the contact surface relative to the horizontal being in a range of 3° - 15°, preferably 5° - 10° and particularly preferably 7° - 9°. The panel level is usually aligned horizontally when two panels are in the locked state. In the context of the invention, the term "horizontal" means an orientation parallel to the plane of the panel or the upper side of the panel. Due to the inclination of the contact surface, better cohesion can be achieved, particularly in the case of a panel core made of a carrier material that is brittle, which comes to the surface in the region of the contact surface.

It has proven to be particularly useful when the outside spring bottom cambered contour is an outwardly cambered radius centered above the panel top. By this measure, a relatively elongated underside of the spring is formed. It works together with an equally elongated lower groove wall, which has a concave contour adapted to the underside of the tongue. The curvatures of the underside of the spring and the lower wall of the groove are small and the surface is relatively large. When the top side of the panel is loaded, the panel edge with the locking tongue benefits from a high load-bearing capacity between the underside of the tongue and the lower groove wall.

A tangential transition from the rounding of the free end of the locking spring to the convex contour of the underside of the spring is preferably provided. Abandoning an edged transition also increases the stability of the panel edge or the panel at this point.

The locking groove may have a short upper groove wall with a free end and a long lower groove wall with a distal ridge on it.

It is advantageous if the edge strip has a holding surface and the normal to the surface of the holding surface points in the proximal direction. Arranged in this way, the holding surface can achieve a good holding force to counteract the panel edges moving apart perpendicularly from one another in the plane of the panel (horizontally).

The locking spring expediently has a counter-retaining surface, which is provided with a proximally oriented surface normal, and that the counter-retaining surface interacts with the retaining surface of the edge strip of the lower groove wall when two panels are in the locked state. True, the concave The contour of the lower groove wall increases in the direction of the edge strip and, together with the matching convex contour of the underside of the tongue, forms an overlap that counteracts the panel edges moving apart in the horizontal direction mentioned above, but the horizontal locking effect that can be achieved by means of a pronounced holding surface and matching counter-holding surface significantly improved.

Further favorable properties can be achieved if the retaining surface of the edge strip and the counter-retaining surface of the locking spring are arranged parallel to one another in the locked state and at the same time in an angle range of -10° to +10°, preferably -5° to +, relative to the perpendicular to the top of the panel 5° are arranged. If the holding surface/counter-holding surface is in the negative part of the angle range, then there is an additional undercut between these two surfaces. Due to the additional undercut, locking is also effected in a direction perpendicular to the panel plane (vertical). A certain elastic deformation in the area of the locking means is necessary during the joining process to produce the locking in order to produce the additional undercut and to bring the holding surface into engagement with the counter-holding surface.

If the retaining surface/counter-retaining surface are arranged differently, namely so that they lie in the positive part of the angular range, then the locking means can be connected to one another without elastic deformation and the locked state can be established more easily. Then interlocked panel edges have an interlocking effect only in the horizontal direction. The lower the angle of inclination from the perpendicular to the panel surface, the better this locking effect deviates.

At the free end of the upper groove wall an abutment surface is usefully provided, the panel edge with the locking tongue above it having a counter abutment surface which, when two panel edges are locked together, cooperates with the abutment surface of the upper groove wall. The pairing of abutment surface/counter abutment surface limits the joining movement during the locking process, i.e. the locking spring cannot then be moved deeper into the locking groove. At the same time, a closed joint forms between the panel edges involved on the top side of the panel.

Both the abutment surface mentioned and the counter-abutment surface are expediently arranged perpendicularly to the panel plane. If a certain contact pressure occurs, which presses the abutment surface and the mating surface against one another, then these surfaces can absorb the contact pressure. There is then no risk of the two surfaces slipping relative to each other and possibly causing a height offset on the top of the panel. In the case of an arrangement of the pairing of abutment surface/counter abutment surface which is inclined relative to the perpendicular to the plane of the panel, there would be a risk of a relative displacement of these surfaces, which could have a disadvantageous effect as a height offset on the upper side of the panel.

A further benefit arises when the lower groove wall has a depression at the transition to the edge strip, the depression merging into the holding surface of the edge strip. This measure is favorably accompanied by the fact that the holding surface can be better used at its lower end. For example, it can also reach a little deeper down, right into the depression. At least creates the deepening a cut-out area that helps the underside of the spring to settle unhindered and the counter-retaining surface of the locking spring can position exactly against the retaining surface of the edge strip of the lower groove wall.

If the above-mentioned indentation, with which the lower groove wall merges into the holding surface of the edge strip, is dispensed with, the edge strip can alternatively be designed somewhat higher in order to enlarge the holding surface upwards and give it the desired stability.

Moreover, it is considered advantageous if the top side of the panel has a broken edge on that panel edge with the locking groove and/or has a broken edge on the panel edge with the locking tongue. In this way, a panel edge can also be improved in the area of the top side of the panel, because a broken edge, which can be designed as a phase or radius, for example, acts as edge protection.

On its upper side, the locking spring has a distal extension from the counter-abutment surface to the free end of the locking spring.

In addition, if two interlocked panel edges each have an edge break, for example a chamfer each, then two edge breaks form a common clearance. Below the free space, the panels touch in a plane that can be marked with a center line. The common free space can be a V-shaped free space (V-joint), for example. It is preferred if the width of the common free space is greater than the distal extension of the upper side of the locking spring.

In addition, it is considered expedient to put the cross-section of the common clearance in a suitable ratio with that part of the cross-section of the locking spring which protrudes above the plane of the center line mentioned. Put simply, the front part of the locking spring should have a cross section that is approximately the same size as the free cross section of the free space.

More generally, the front part of the locking spring can have a cross-section which is a certain amount smaller or a certain amount larger than the free cross-section of the free space. The cross section of the front part of the locking spring should then be in the range of 80 - 120% of the size of the cross section of the free space.

Alternatively, the width of the edge bevel and/or its depth may range from 5% to 20% of the total thickness of the panel. In this way, the degree of edge beating is related to the size of the radius of curvature of the locking spring; There is some overlap in relation to the overall thickness of the panel because the radius should be in the range of 10% - 20% of the overall thickness.

Fig. 1

ein Ausführungsbeispiel des erfindungsgemäßen Paneels

Fig. 2

eine alternative Gestaltung für den Ausschnitt im Bereich von II in Fig. 1,

Fig. 3

eine erste alternative Gestaltung für den in Fig. 1 mit III vermerkten Bereich,

Fig. 4

eine zweite alternative Gestaltung für den in Fig. 1 mit III vermerkten Bereich,

Fig. 5

eine dritte alternative Gestaltung für den in Fig. 1 mit III vermerkten Bereich,

Fig. 6

eine vierte alternative Gestaltung für den in Fig. 1 mit III vermerkten Bereich,

Fig. 7

eine fünfte alternative Gestaltung für den in Fig. 1 mit III vermerkten Bereich,

Fig. 8

eine sechste alternative Gestaltung für den in Fig. 1 mit III vermerkten Bereich,

Fig. 9

eine siebte alternative Gestaltung für den in Fig. 1 mit III vermerkten Bereich,

Fig. 10

eine achte alternative Gestaltung für den in Fig. 1 mit III vermerkten Bereich.

The invention is illustrated by way of example in a drawing and described in detail below. Show it:

1

an embodiment of the panel according to the invention

2

an alternative design for the neckline in the area of II in 1 ,

3

a first alternative design for the in 1 area marked III,

4

a second alternative design for the in 1 area marked III,

figure 5

a third alternative design for the in 1 area marked III,

6

a fourth alternative design for the in 1 area marked III,

7

a fifth alternative design for the in 1 area marked III,

8

a sixth alternative design for the in 1 area marked III,

9

a seventh alternative design for the in 1 area marked III,

10

an eighth alternative design for the in 1 area marked III.

1 shows an embodiment of a panel according to the invention. The panel is shown split to show its opposite panel edges 1 and 1' and their complementary locking means 2 and 3 in the locked condition. Of course, the panel edges shown in sections can also be interpreted as a representation of two panels which are not severed.

In practice, it is quite common to cut through a panel, for example if the panel is too long at the end of a row of panels. It is then trimmed to fit and severed for the purpose. The leftover piece cut off can usually be used to start a new row of panels, starting with the side with the sectioned area of the row and there is locking means at the opposite end to lock a new panel thereto. Complementary locking means of a severed panel thus fit into each other and can in principle be locked together as shown in FIG 1 recognizable.

The design according to the invention is preferably intended to enable the panels to be designed with a small overall thickness. The low overall thickness should be possible even if the panel core is made of a carrier material that is brittle.

The panel according to 1 consequently has a panel core 4 made of a carrier material which has a plastic as the matrix material. A proportion of solid material is provided therein as a filler, namely a mineral filler in the form of talc. This carrier material has a certain brittleness due to the filler.

In order to obtain a panel with good stability despite this peculiarity, in particular good stability of the panel edges 2 and 3, these have a special design.

Basically it is about 1 to a panel with a panel top 5 with a wear layer 6, a panel bottom 7 and with pairs of opposite panel edges 1 and 1 ', which form a pair of edges. At least that in 1 The pair of edges shown has complementary locking means 2 or 3 with a tongue and groove profile, namely a locking groove 8 on a groove side of the pair of edges and a locking spring 9 on a tongue side of the pair of edges two panels perpendicular to the interlocked panel edges and away from each other. At the same time, the panel edges have a positive locking effect in the vertical direction.

On the groove side, the panel has an upper groove wall 10 and a lower groove wall 11 . The upper groove wall has a free end on which a flat abutment surface 12 is formed. The abutment surface 12 is arranged perpendicular to the panel plane. The lower groove wall 11 is longer than the upper groove wall. It protrudes further in the distal direction than the upper groove wall. At its free end it is provided with an edge strip 13 which has a holding surface 14 which is arranged in the proximal direction, i.e. its surface normal is aligned proximally.

On the spring side, the panel has the locking spring 9 and above it a counter-abutment surface 15 which interacts with the upper groove wall 10, namely touches its abutment surface 12 when the panel edges 1 and 1' are in the locked state.

The locking spring 7 has a spring top 16 with a contact surface 17 which is directed toward the panel top 5 . In the embodiment of 1 the contact surface 17 is arranged parallel to the top side 5 of the panel. A rounding 18 follows the contact surface 17 . The rounding has a radius 20 which is larger than the distal extension 21 of the contact surface 17. In this way the free end of the locking spring 9 is provided with a comparatively large rounding 18 and is thereby more stable than known panels which are more pointed or have corners . In particular, it is found that the carrier material holds together better at the free end of the locking spring 9 . The contours are made by machining, for example milled.

The locking groove 8 has a contact surface 22 on the upper groove wall 10, which is arranged parallel to the contact surface 17 and according to FIG 1 at this. The contact surface 22 transitions into a groove base 23 which has a radius 24 and is adapted to the curve 18 of the locking spring 9, so that the curve 18 fits into the locking groove 8 and between the curve 15 and the radius 24 of the groove base 23 there is a small gap remains, which is in the order of tenths of a millimeter or fractions thereof.

The large rounding 18 at the front of the locking spring 9 transitions into an outwardly curved (convex) contour 25 which forms the underside 26 of the spring. The convex contour 25 lies on a large radius 27, the center of which is well above the panel. The radius 27 is several times larger than the overall thickness T of the panel. The contour 25 of the underside 26 of the spring that is curved in this way extends far in the proximal direction. At its end, the contour 25 transitions into a counter-retaining surface 29. The counter-retaining surface has a surface normal in the proximal direction. In the locked state, the counter-retaining surface 29 interacts with the above-mentioned retaining surface 14 of the edge strip 13 of the lower groove wall 11. To 1 the holding surface 14 and the counter-holding surface 29 are parallel to one another and touch one another. Furthermore, this surface pairing of holding surface/counter-holding surface is inclined relative to the perpendicular L of the top side of the panel 5, the angle of inclination α relative to the perpendicular being marked with +/- within the meaning of the invention. In the present case, the angle of inclination α is +5° according to this definition.

In 2 an alternative design for the cutout is shown in 1 is marked with II. A section of the locking groove 8 and a section of the locking spring 9, which are in the locked state, can be seen. At the edges of the top side 5 of the panel, an edge break 29 or 30 is provided in the form of a 45° chamfer 29a and 30a. Together, the 45° bevels form a free space 31 in the form of a V-joint 31a. In this exemplary embodiment, the depth of the V-joint 31a, or the depth of the chamfer, is 19% of the total thickness T of the panel. Also visible is the rounding 18 at the free end of the locking spring 9, which in this embodiment has a radius 20, the size of which is 12% of the total thickness T of the panel. In addition, in contrast to the embodiment of 1 provided on the spring top 16 of the locking spring 9 is a contact surface 28 which is inclined relative to the horizontal by an angle of inclination β. The angle of inclination β has an amount of 8° here, so that the contact surface 28 runs downwards towards the rounding 18 .

At the locking groove 8 is according 2 the upper groove wall 10 is shown, which has an abutment surface 12 at its free end. The abutment surface 12 is arranged perpendicularly (vertically) to the top side 5 of the panel. Due to the edge break 29 located above, the abutment surface 12 is somewhat smaller than in the exemplary embodiment of FIG 1 .

the Figures 3 to 10 show alternative designs for the area in 1 is marked with III. Each of these alternatives can be used both as a modification of 1 provide, as well as use together with the modification in 2 has already been suggested.

Area III is about the lower groove wall 11 of the locking groove 8, which is provided with the edge strip 13, and the matching contour 25 of the spring underside 26 locking spring 9.

3 shows a section of the lower groove wall 11 with the edge strip 13, which has a proximally arranged holding surface 14, which means that the surface normal of the holding surface 14 is aligned proximally. In this exemplary embodiment, the holding surface is inclined by +5° relative to the perpendicular L on the top side of the panel. This embodiment provides positive locking against moving apart of the locked panel edges in a direction that is in the plane of the locked panels and at the same time perpendicular to the locked panel edges. A locking effect against the locked panel edges moving apart perpendicular to the panel plane (vertical) is according to FIG 3 not provided. The contour 25 of the spring underside 26 curves outwards (convex), the curve having a large radius 27 that appears almost straight in the illustration. Proximally, the contour 25 of the spring underside 26 merges into a counter-retaining surface 29 which is inclined to match the retaining surface 14 of the edge strip 13 . The support surface/countersurface mating is parallel and in contact with each other. The transition between the curved contour 25 of the spring underside 26 and the counter-retaining surface 29 is provided as a tangential transition with a small radius 32 .

At its upper end, the edge strip 13 is bent downwards in the distal direction. In this area, the locking spring 9 has a recess 33 which is larger than the edge strip 13. A gap 34 (air) is provided between the edge strip 13 and the recess 33 in the distal direction. The contour of the recess 33 is also curved to match the edge strip 13 . This arcuate design of the edge strip 13 and recess 33 in turn benefits the stability, in particular when the panel core consists of a carrier material with a certain degree of brittleness, better cohesion of the structure is achieved and less breakage occurs.

In 4 an alternative design is shown, based on 3 based to which reference is made. It differs in a modified contour 25 of the outwardly curved spring underside 26 and the matching contour of the lower groove wall 11. The lower groove wall 11 namely has a low point 35 and from there a certain (slight) rise in the distal direction. This configuration is preferred when a contact surface at the top of the locking spring 9 has a slope, as in the example of FIG 2 the contact surface 28, whereby it is on the in 2 planned edge breaking does not arrive. When the panels are moved apart under a certain elastic deformation, the mentioned rise in the contour of the lower groove wall 11 can cause the locking spring 9 to slide up along the rise. At the same time, the contact surface 28 provided at the top of the locking spring 9 can slide along a complementary contact surface 22 of the upper groove wall 10 because this has an inclination angle β which is approximately parallel to the slope of the contour of the lower groove wall 11.

The embodiment of figure 5 based on that of 3 . In contrast to 3 however, the lower groove wall 11 has a recess 36 at the transition to the edge strip 13, which merges into the holding surface 14 of the edge strip 13. The recess 36 is groove-shaped with a round cross-section, which serves for stability.

6 is an alternative design based on figure 5 based to which reference is made. It differs in a modified contour 25 of the outwardly curved underside of the tongue 26 and the matching contour of the lower groove wall 11. These contours are designed as described above in 4 , ie the lower groove wall 11 has a low point 35 . From the low point 35 in the distal direction, a certain (slight) increase towards the edge strip 13 is provided. This design is preferred in combination with one, as in the example 2 , inclined contact surface 28 on the spring top 16 of the locking spring 9, for the same reasons as mentioned above.

The embodiment of 7 based on that of figure 5 . It differs in the design of the wheel bar 13, which now has a proximal holding surface 14, which is again inclined relative to the perpendicular L of the panel top 5, but compared to figure 5 in the opposite direction, which means an angle of inclination α of -5° in the present exemplary embodiment. The locking spring 9 has a proximal counter-retaining surface 29 which, in the locked state, is arranged parallel to the retaining surface 14 of the edge strip 13 and touches it over an area.

If the pairing of retaining surface/counter-retaining surface is arranged with an angle of inclination α of -5°, then there is an additional undercut between the two surfaces of this pairing, which also causes locking in a direction perpendicular to the panel plane (vertical). In order to bring this undercut into engagement, a certain elastic deformation in the area of the locking means 2 and 3 is necessary during the joining process.

8 shows an embodiment, the holding surface / counter holding surface identical with 7 are arranged at an angle of inclination α of -5°, so that they can cause locking perpendicular to the panel level (vertical). In addition, the contour 25 of the outwardly curved underside of the tongue 26 and the matching contour of the lower groove wall 11 have been modified, as described above in Figures 4 and 5 ie the lower groove wall 11 has a low point 35 and from there in the distal direction towards the edge strip 13 there is a certain (slight) rise. This design is in turn preferred in combination with an inclined contact surface on the upper side of the locking spring, as in the example of FIG 2 the contact surface 28. There is the same advantage as above 4 described. Furthermore, the lower groove wall 11 is provided with a groove-shaped depression 36, as in FIG figure 5 , to which reference is made.

9 is an embodiment whose holding surface / counter holding surface is identical to 7 are arranged at an angle of inclination α of -5°, so that they can cause locking perpendicular to the panel plane (vertical). In contrast to 7 however, a groove-shaped depression 36 in the lower groove wall 11 is dispensed with.

10 is a further exemplary embodiment with a holding surface/counterholding surface arranged at an angle of inclination α of -5°, so that they cause locking perpendicular to the panel plane (vertical), insofar as it is 10 identical with figs 7, 8 and 9 . However, the contour 25 of the outwardly curved spring underside 26 and the matching contour of the lower groove wall 11, which has a low point 35 and from there a certain (slight) rise in the distal direction towards the edge strip 13, differ.

Reference List

1

panel edge

1'

panel edge

2

locking means

3

locking means

4

panel core

5

panel top

6

wear layer

7

panel underside

8th

locking groove

9

locking spring

10

upper groove wall

11

lower groove wall

12

Impact surface (upper groove wall)

13

sidebar

14

holding surface (edge bar)

15

counter impact surface

16

feather top

17

contact surface

18

rounding

20

radius

21

extension (contact area)

22

touchpad

23

groove bottom

24

radius

25

convex contour (feather underside)

26

feather bottom

27

Radius (bottom of spring)

28

contact surface

29

counter surface (spring underside)

30

edge breaking

30a

45° bevel

31

edge breaking

31a

45° bevel

32

free space

32a

V-joint

33

recess

34

gap

35

rock bottom

36

deepening

L

Lot

T

overall thickness

a

Angle of Inclination (Rail)

β

inclination angle (contact surface)

Claims (14)

1. Panel comprising a panel core (4), a panel top side (5) having a utility layer, a panel underside (7) and edge pairs provided in paired relationship at mutually opposite panel edges (1, 1'), wherein at least a first edge pair is provided with complementary locking means (2, 3), of which one locking means (2) on a groove side of the edge pair is in the form of a locking groove (8) and the complementary locking means (3) on a tongue side of the edge pair is in the form of a locking tongue (9) which fits together in positively locking relationship with the locking groove (8) so that similar panels can be locked to each other, wherein the locking tongue (9) of a first panel with said panel in an inclined position can be fitted to the locking groove (8) of a second similar panel and then the two panels can be locked together in positively locking relationship by a rotational joining movement of the panels relative to each other so that the positively locking engagement which can be achieved counteracts movement of the locked panel edges (1, 1') away from each other, more specifically in a direction which is in the plane of the locked panels and at the same time perpendicular to the locked panel edges (1, 1'), wherein the locking tongue (9) at its tongue top side (16) has a contact surface (17, 28) which is directed towards the panel top side (5) and wherein the upper groove wall (10) has a contacting surface (22) which is of such a configuration that in the locked state of two panels it fits together with the contact surface (17, 28) of the tongue top side (16), characterised in that at the front on the locking tongue (9) a rounded portion (18) tangentially adjoins the contact surface (17, 28), the rounded portion (18) forms a free end of round cross-section of the locking tongue (9), a round transition to the tongue underside (26) is created, that the rounded portion (18) of the locking tongue (9) is of a radius (20) equal to or greater than the distal extent of the contact surface (17, 28), and that the rounded portion (18) of the locking tongue (9) merges into an outwardly curved contour (25) extending along the tongue underside (26).
2. Panel according to claim 1, characterised in that its overall thickness is in the range of 2 to 6 mm, preferably between 2.5 and 5 mm and particularly preferably between 2.8 and 4 mm.
3. Panel according to claim 1 or claim 2 characterised in that the locking groove (8) has a groove bottom (23) which is of round cross-section and which adjoins the contacting surface (22) of the upper groove wall (10) and the groove bottom (23) of the locking groove (8) is of a radius (24) equal to or greater than the distal extent of the contacting surface (22).
4. Panel according to one of claims 1 to 3 characterised in that the contact surface (28) is inclinedly downwardly in the distal direction, and the angle of inclination (β) of the contact surface (28) relative to the horizontal is in a range of 3° to 15°, preferably 5° to 10°, particularly preferably 7° to 9°.
5. Panel according to claim 4 characterised in that the outwardly curved contour (25) of the tongue underside (26) is an outwardly curved radius (27), the centre point of which is above the panel top side (5).
6. Panel according to claim 5 characterised in that there is preferably a tangential transition from the rounding (18) into the convex contour (25) of the tongue underside (26).
7. Panel according to one of claims 1 to 6 characterised in that the locking groove (8) has a short upper groove wall (10) having a free end and a long lower groove wall (11) at which an edge bar (13) is distally provided.
8. Panel according to claim 7 characterised in that the edge bar (13) has a holding surface (14) and the surface normal of the holding surface (14) faces in the proximal direction.
9. Panel according to claim 7 or 8 characterised in that the locking tongue (9) has a counterpart holding surface (29) provided with a proximally oriented surface normal and the counterpart holding surface (29) in the locked state of two panel cooperates with the holding surface (14) of the edge bar (13) of the lower groove wall (11).
10. Panel according to claim 8 or 9 characterised in that the holding surface (14) of the edge bar (13) and the counterpart holding surface (29) of the locking tongue (9) are arranged parallel to each other in the locked state and are arranged in an angle range of -10° to +10°, preferably -5° to +5° relative to the perpendicular (L) to the panel top side (5).
11. Panel according to one of claims 1 to 10 characterised in that a butting surface (12) is provided at the free end of the upper groove wall (10), the panel edge (1') with the locking tongue (9) has above same a counterpart butting surface (15) which when two panel edges (1, 1') are locked to each other cooperates with the butting surface (12) of the upper groove wall (10).
12. Panel according to one of claims 7 to 11 characterised in that the lower groove wall (11) has a recess (36) at the transition to the edge bar (13) and the recess (36) transitions into the holding surface (14) of the edge bar (13).
13. Panel according to one of claims 1 to 12 characterised in that at the panel edge (1) with the locking groove (8) the panel top side (5) has an edge break (30) and/or at the panel edge (1') with the locking tongue (9) it has an edge break (31).
14. Panel according to one of claims 1 to 13 characterised in that the locking tongue (9) extends in the distal direction beyond the counterpart butting surface (15) and both panel edges (1, 1') have edge breaks (30, 31) which form a free space (32) in the locked state.

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