A leak-proof and break-resistant panel with a locking element and a method for manufacturing such a panel

Description

[0001] The invention relates to a panel with a high breaking strength and a high level of resistance to liquid reaching an underside of the panel, which panel can cover a surface of a room by means of panels locked together via a locking element, in particular a fixed one, in particular in order to improve the visual appearance of the room and / or to conceal the surface of the room with a material layer that is more suitable for the intended function, as well as a method by which such a panel can be produced.

[0002] From WO 2007 / 079845 A1 it is known to provide a retaining groove on a short side of a panel over the entire transverse extent of the panel, into which a locking element designed as a locking clip can be inserted in a movement-proof manner.

[0003] From WO 2010 / 087752 A1 it is known to saw a part-circular groove in a partial area on a short side of a panel, in which groove a projection of a locking element otherwise provided outside the groove can be displaced in the transverse direction, wherein the projection can slide on the rounded edges of the part-circular groove and can thereby press the locking element with a movement component in the longitudinal direction into an opposite groove of another panel.

[0004] EP 2 946 047 B1 discloses a panel according to the preamble of claim 1 and a method according to the preamble of claim 10. It discloses a floor panel for forming a floor covering, wherein the floor panel has coupling parts on at least one pair of opposite edges, which enable two such floor panels to be connected by a downward movement of one floor panel with respect to the other floor panel, wherein these connecting parts enable locking in a first direction perpendicular to the plane of the floor panels and in a second direction perpendicular to the respective edge and in the plane of the floor panels, wherein at least one of the edges has a longitudinal recess below the upper surface with a locking element, characterized in that the shape and / or the position of the recess and / or the configuration of the connecting parts is such that deformations are avoided.

[0005] EP 2 2346 694 A1 discloses a fastening system for fastening two panels to one another, comprising a first panel with a first edge having an undercut that receives a fastening element, and a second panel with a second edge that has a locking region. The first and second edges lie next to one another when the panels are fastened to one another by means of the fastening system. The fastening element comprises a displaceable activation portion and a locking portion that is displaceable with respect to the first panel by rotation about a pivot axis upon displacement of the activation portion, such that the locking portion engages the locking region of the second panel when the panels are fastened to one another by means of the fastening system. The pivot axis is spaced from a wall of the undercut.

[0006] US 7,131,473 B1 discloses a copy cutter that can be easily modified to cut profiles with tenons of different lengths. The cutter comprises an axially extending main drive shaft and a first cutting element fixed to the main drive shaft. An axially extending secondary drive shaft having an upper and a lower portion is removably mounted on the primary drive shaft for rotation therewith, and a second cutting element is mounted on the secondary drive shaft at a distance from the first cutting element when the secondary drive shaft is mounted to the primary drive shaft.

[0007] There is a constant need to improve the fracture strength and resistance to liquid penetration of panels.

[0008] The object of the invention is to show measures that enable a break-proof and walk-through-proof panel.

[0009] The object is achieved by a panel having the features of claim 1 and a method having the features of claim 10. Preferred embodiments of the invention are specified in the subclaims and the following description, which may each individually or in combination represent an aspect of the invention.

[0010] One embodiment of the invention relates to a panel for covering a surface of a room, comprising a panel body extending in a longitudinal direction and a transverse direction for transferring service loads introduced at an upper side of the panel body to an underside of the panel body facing the surface of the room, wherein the upper side is spaced from the underside in a thickness direction, and a retaining groove extending in a transverse direction in a frontal short side of the panel body and a locking element inserted in the retaining groove, in particular substantially immobile, wherein for an extension b 0 of the retaining groove in the transverse direction relative to a nominal width B of the panel body between a longitudinally extending first edge and a longitudinally extending second edge of the panel body 0.50 ≤ b 0 / B ≤ 0.97, in particular 0.75 ≤ b 0 / B ≤ 0.95, preferably 0.85 ≤ b 0 / B ≤ 0.93 and particularly preferably b 0 / B = 0.90 ± 0.02 applies, wherein in the transverse direction (32) between a first end of the holding groove (20) pointing in the transverse direction (32) towards the first edge, a first reinforcement region (24) with an extension t 1 in the transverse direction (32) is formed, wherein in the transverse direction (32) between a second end of the holding groove (20) pointing in the transverse direction (32) towards the second edge, a second reinforcement region (26) with an extension t 2 in the transverse direction (32) is formed, wherein for the first reinforcement region (24) 0.005 ≤ t 1 / B ≤ 0.090, in particular 0.015 ≤ t 1 / B ≤ 0.050, preferably 0.020 ≤ t 1 / B ≤ 0.030 and particularly preferably t 1 / B = 0.025 ± 0.002 and / or for the second gain region (26) 0.005 ≤ t 2 / B ≤ 0.090, in particular 0.015 ≤ t 2 / B ≤ 0.050, preferably 0.020 ≤ t 2 / B ≤ 0.030 and particularly preferably t 2 / B = 0.025 ± 0.002, with the proviso that t 1 + b 0 + t 2 = B,wherein the panel body (28) has a bung groove (12) extending into the panel body (28) at the first edge and a bung projection (14) projecting from the panel body (28) at the second edge, wherein t 1 < t 2 , in particular 0.75 ≤ t 1 / t 2 ≤ 0.99, preferably 0.80 ≤ t 1 / t 2 ≤ 0.95 and particularly preferably 0.85 ≤ t 1 / t 2 ≤ 0.90.

[0011] The panel can have a panel body based on a cuboid as its basic shape, the longitudinal extent of which is generally significantly greater than its transverse extent, while the thickness of the panel body in the thickness direction is generally smaller than its transverse extent. The panel body can have a tongue and groove joint on one long side running in the longitudinal direction, in particular a continuous tongue and groove joint extending in the transverse direction, and on the other side a tongue and groove joint introduced into the panel body in the transverse direction, so that essentially identically designed panels can be connected to one another along the long sides via a tongue and groove joint designed as a tongue and groove joint.In particular, a locking hook can protrude longitudinally from the short side of the panel body running in the transverse direction, while a spring body can protrude on the other short side of the panel body, delimiting a receiving groove, so that essentially identically designed panels can also be locked together on their short sides via a spring-groove connection. In addition to or alternatively to the spring-groove connection formed with the aid of the locking hook and the receiving groove of the spring body, the locking element can be inserted, in particular in a movement-proof manner, in the holding groove provided on the short side of one panel, which can engage in a locking groove provided on a short side of another, in particular essentially identically designed, panel facing the locking element.For this purpose, the locking element, which is designed in particular in the manner of a locking clip, can have a locking web with a locking lug which can be elastically pushed away as the panels move past during assembly in order to snap elastically at least partially, in particular with the locking lug, into the locking groove in the designated end position of the panels to be locked together, and to secure the panels thus locked together against accidental release. During assembly, one panel can lie flat on a surface defining a usage plane, for example a floor, a side wall or a ceiling of a room. The other panel can, if necessary, for example, at an angle of approx.Slightly beveled at 30°, it is placed on the long side with an already installed panel running alongside the panel and then pivoted onto the substrate, thereby creating at least one locking connection between the panels facing each other on the short sides. During locking, the locking hook can be locked into the receiving groove of the other panel, and the locking element inserted into the holding groove can be locked into the locking groove of the other panel, essentially simultaneously. The extension of the locking groove in the transverse direction corresponds in particular to the extension of the holding groove in the transverse direction. In particular, for an extension c 0 of the locking groove in the transverse direction based on the nominal width B of the panel body, 0.50 ≤ c 0 / B ≤ 0.97, in particular 0.75 ≤ c 0 / B ≤ 0.95, preferably 0.85 ≤ c 0 / B ≤ 0.93 and particularly preferably c 0 / B = 0.90 ± 0.02.Preferably, the locking groove is configured identically to the retaining groove and / or manufactured using the same manufacturing process, thereby simplifying the simultaneous and / or identical production of the locking groove and the retaining groove. The retaining groove accommodating the pre-assembled locking element can be provided on one short side of the panel, while the locking groove is provided on the other short side of the panel.

[0012] Because the retaining groove and / or the locking groove are not provided over the entire transverse extent of the panel body, but only in a portion of the transverse extent, it is possible to avoid weakening the panel body in the corners of the panel body in a transition area between the short side and the long side. This takes advantage of the knowledge that with a retaining groove that is continuous in the transverse direction, both the retaining groove and a sheet bung groove can end in a corner of the panel body, resulting in a particularly large amount of material being missing in the transition area between the short side and the long side, which could compromise the strength of the panel. In addition, outlet openings on the long edges of the panel through which water could flow downwards can be avoided. Instead, one groove base of the sheet bung groove is also closed on the short side, providing an effective barrier against water flowing through.However, since the retaining groove running transversely along the short side can end at a distance from the tongue and groove running longitudinally along the long side, sufficient material of the panel body remains between the retaining groove and the tongue and groove to prevent a significant impairment of the strength of the panel body in the transition area between the short side and the long side compared to the strength of the tongue and groove and / or the remaining retaining groove. This at least reduces the risk of damage to the panel in the corners due to heavy, particularly localized, stresses, for example, when an office chair is driven over the corner or a table leg rests against the corner.If the locking element is not movable but fixed in the retaining groove, an air gap between the locking element and at least some of the surfaces of the retaining groove facing the locking element can be minimized, in particular eliminated by a press fit. Breakage of the material delimiting the retaining groove can thus be prevented. Instead, the locking element can fill a large part of the volume of the retaining groove, in particular more than 50%, preferably more than 75%, more preferably more than 85% and particularly preferably more than 95%, whereby loads acting on the material of the panel body delimiting the retaining groove can be dissipated via the locking element. The breaking strength of the panel, in particular in the corner regions of the panel, is thereby improved.

[0013] At the same time, hydraulic communication between the retaining groove and the sheet bung groove can be avoided or at least reduced. This avoids a larger collection volume at a T-joint of three panels, which would otherwise be joined by two sheet bung grooves and a retaining groove, compared to the flow cross-section along the retaining groove in the transverse direction and / or along the sheet bung groove in the longitudinal direction. A drop in capillary forces acting on penetrated liquids can be avoided, so that the penetrated liquid can more easily evaporate at a later time and / or escape from a joint between the panels, even at a T-joint.This at least reduces or even prevents the accumulation of liquid in the collection volume, from which the liquid can reach the underside of the panel body, particularly due to increasing hydrostatic pressure over time as a result of subsequent liquid ingress, and remain there, promoting the formation of mold. The risk of liquid seeping through joints between the panels to the underside of the panel is thus at least reduced, thus improving the permeability of the panel against liquid reaching the underside.

[0014] The leak resistance of the panel can be measured by filling a container that is open at the top and bottom with a liquid, in particular water, of a predefined volume, such that the liquid reaches a defined fill level in the container with a resulting defined hydrostatic pressure. The container filled with the liquid is placed centrally on a T-shaped joint intersection area on the top sides of three locked-together panels. The fill level of the liquid remaining in the container after a predefined period of time is a measure of the leak resistance against the liquid penetrating the joint formed between the locked-together panels.

[0015] Since the retaining groove does not extend across the entire transverse extent of the panel body, the locking element can also have a transverse extent that is less than the entire transverse extent of the panel body. This utilizes the finding that the locking element, designed in the manner of a locking clip, can provide sufficiently good locking even with a smaller transverse extent due to the positive clip connection, so that it is not even necessary to provide locking across the entire transverse extent of the panel body. At the same time, the transverse extent of the locking element is still large enough that the forces acting on the locking element during locking can be distributed over a larger area, and the local mechanical loads on the locking element can be kept low.The selected ratio of the transverse extension b 0 of the retaining groove relative to the nominal width B of the panel body results in improved fracture strength and improved perforation resistance in the corner areas of the panel body, while simultaneously ensuring good locking with low component loads for the locking element. The retaining groove, which only extends over a large portion of the short side, and the locking element accommodated in the retaining groove enable a fracture-resistant and perforation-resistant panel with good, material-friendly locking.

[0016] The locking element is in particular inserted into the retaining groove in such a way that movement of the locking element in the transverse direction is blocked by frictional engagement and / or positive engagement. In particular, it can be provided that the locking element abuts against the corresponding end of the retaining groove during movement in the transverse direction and cannot be moved any further. Preferably, a clearance fit is formed between the retaining groove and the locking element in the transverse direction. Particularly preferably, a press fit is formed between the retaining groove and the locking element in the thickness direction, whereby stiffening of the material of the panel body forming the retaining groove can be achieved. Suitable locking elements are described, for example, in WO 2007 / 079845 A2, the relevant content of which is hereby incorporated by reference as part of the invention.

[0017] According to the invention, a first reinforcement region with an extension t 1 in the transverse direction is formed in the transverse direction between a first end of the retaining groove pointing transversely towards the first edge, wherein a second reinforcement region with an extension t 2 in the transverse direction is formed in the transverse direction between a second end of the retaining groove pointing transversely towards the second edge, wherein for the first reinforcement region 0.005 ≤ t 1 / B ≤ 0.090, in particular 0.015 ≤ t 1 / B ≤ 0.050, preferably 0.020 ≤ t 1 / B ≤ 0.030 and particularly preferably t 1 / B = 0.025 ± 0.002 and / or for the second reinforcement region 0.005 ≤ t 2 / B ≤ 0.090, in particular 0.015 ≤ t 2 / B ≤ 0.050, preferably 0.020 ≤ t 2 / B ≤ 0.030 and particularly preferably t 2 / B = 0.025 ± 0.002, with the proviso that t 1 + b 0 + t 2 = B.Each reinforcement area adjoins the associated edge of the panel body and extends transversely along the short side to the associated end of the retaining groove. This means that the reinforcement area is free of the retaining groove. Instead of the retaining groove that would otherwise be present in the reinforcement area, the volume of the otherwise present retaining groove is filled by the material of the panel body. This accumulation of material in the reinforcement area leads to increased stability and increased fracture strength in the corner area of ​​the panel body. At the same time, each reinforcement area is short enough that a sufficiently large portion of the transverse extension of the short side remains for the retaining groove and the locking element inserted in the retaining groove.

[0018] The panel body has a bung groove extending into the panel body at the first edge and a bung extension protruding from the panel body at the second edge, where t 1 < t 2 , in particular 0.75 ≤ t 1 / t 2 ≤ 0.99, preferably 0.80 ≤ t 1 / t 2 ≤ 0.95 and particularly preferably 0.85 ≤ t 1 / t 2 ≤ 0.90. It can be taken into account here that the bung extension makes the panel body more stable and stronger at the second edge than at the first edge, where the bung groove is provided. This allows the second reinforcement region to be correspondingly shorter in the transverse direction than the first reinforcement region.In the joint area between two essentially identically designed panels that are adjacent to one another along their long sides, a joint reinforcement area of ​​t 1 + t 2 of equal size is created on both long sides of the respective panel, with the first reinforcement area provided by one panel and the second reinforcement area provided by the other panel. This allows good fracture resistance in the area of ​​the tongue and groove to be achieved while simultaneously achieving good fracture resistance at the tongue and groove joint formed on the long sides. The tongue and groove is provided within the panel body between the first edge and the second edge of the panel body.The bung extension protrudes from the remaining panel body, with which the bung extension can be formed integrally, and is thus arranged outside the nominal width B of the panel body measured from the first edge to the second edge, so that the extension of the bung extension does not contribute to the nominal width B of the panel body.

[0019] Particularly preferably, the extension b 1 of the locking element in the transverse direction relative to the nominal width B of the panel body is 0.40 ≤ b 1 / B ≤ 0.95, in particular 0.50 ≤ b 1 / B ≤ 0.90, preferably 0.60 ≤ b 1 / B ≤ 0.80, and particularly preferably b 1 / B = 0.70 ± 0.05. The extension of the locking element in the transverse direction of the panel body can, in particular, essentially correspond to the extension of the retaining groove in the transverse direction. However, it is also possible for the extension of the locking element in the transverse direction to be selected to be slightly or significantly less than the extension of the retaining groove. The extension of the locking element can, for example, be dimensioned essentially solely with regard to the locking functionality and the ability to withstand the forces to be expected in this case, whereby it is quite possible that the extension of the locking element can be selected to be smaller than the extension of the retaining groove.In this case, it is in principle possible to adapt the transverse extension of the retaining groove to the required smaller extension of the locking element. However, if the transverse extension of the retaining groove is selected to be significantly larger than the extension of the locking element, alternative manufacturing options for the retaining groove arise. Instead of producing the retaining groove with a pin-shaped milling cutter moving transversely, the diameter of which corresponds in particular to the thickness extension of the retaining groove, it is possible to produce the retaining groove using a circular saw or peripheral milling cutter that plunges into the panel body, as a rounded lead-in area can be permitted at the ends of the retaining groove. This allows for faster and more cost-effective production of the retaining groove.

[0020] In particular, a frictional connection of the locking element in the retaining groove is provided exclusively by clamping forces pointing in the thickness direction. The locking element can be clamped between an upper surface of the retaining groove in the thickness direction and a lower surface of the retaining groove. Hooks and / or spikes protruding from the locking element are preferably driven in a form-fitting manner into the material of the locking element delimiting the retaining groove. Clamping in the transverse direction is precisely not provided. Unnecessary shear forces acting on the locking element can thus be avoided. In addition, it is possible for the locking element to elastically yield slightly in the transverse direction when inserted into the retaining groove, which facilitates pressing the locking element into the retaining groove and / or driving hooks and / or spikes into the material of the retaining groove.

[0021] The locking element preferably has a locking web that can be elastically bent at least partially into the retaining groove. The locking element can therefore be designed as a locking clip. When two panels are locked together and one panel moves past the other, particularly during a pivoting movement, the panel can elastically bend the locking web toward the retaining groove of the locking element and / or at least partially into the retaining groove of the locking element, so that the panel can be moved past the locking element. In the intended end position, the locking element, in particular a locking lug of the locking web, can elastically snap into a locking groove of the panel moving past, creating the locking connection. The locking web of the panel can at least partially engage in the locking groove of the other panel, thereby forming a tongue and groove connection.

[0022] Particularly preferably, the retaining groove has a receiving space adjoining an end face of the short side for receiving a part of the locking element, in particular for temporarily receiving an elastically bendable locking web of the locking element, and a fastening space adjoining the side of the receiving space facing away from the end face for frictionally and / or positively fastening a fastening projection of the locking element, wherein the extension of the fastening space in the thickness direction is smaller than the extension of the receiving space in the thickness direction. The fastening of the locking element in the retaining groove, in particular in a movement-resistant manner, can be effected largely or entirely via the fastening projection of the locking element, which extends into the fastening space.At the same time, the locking element can maintain sufficient free space within the receiving space of the retaining groove for the elastically flexible locking bar of the locking element or another component that enables locking to engage when the panel to be locked is moved past. The locking element does not block the relative movement of the panels intended for locking the two panels.

[0023] In particular, the locking element rests against both surfaces of the receiving space facing in the thickness direction, in particular with a clamping force, wherein the locking element in particular has a receiving pocket extending into the receiving space for temporarily receiving an elastically flexible locking web of the locking element. This makes it possible to provide a movement-resistant and / or in particular load-bearing fastening of the locking element in the retaining groove. It may even be permitted for the locking element to yield elastically in the thickness direction within the volume of the receiving space. The locking element can therefore be manufactured more cost-effectively. Since the locking element rests against the surfaces facing in the thickness direction, at least a certain degree of frictional engagement is provided, which can make it more difficult for the locking element to slip out of the retaining groove.A free volume can be maintained between the material areas of the locking element that are in contact with the surfaces to form the receiving pocket. This allows sufficient pivoting of the elastically flexible locking bar into the receiving pocket as a panel to be locked moves past, and ensures a good frictional connection of the locking element within the retaining groove.

[0024] Preferably, the panel body has, on the short side forming the retaining groove, a locking hook extending longitudinally from the short side of the panel body for locking into a receiving groove of another panel. This enables locking of one panel to another panel both with the aid of the locking element engaging in a locking groove of the other panel and with the aid of the locking hook engaging in a retaining groove of the other panel. Suitable locking hooks and suitable spring bodies having a retaining groove are described in WO 2006 / 133690 A1, the relevant content of which is hereby incorporated by reference as part of the invention.

[0025] Particularly preferably, the retaining groove has, in a cutting plane spanned by the longitudinal and transverse directions, a cross-sectional area that can be produced by rotary cutting and has rounded run-out regions at the transversely facing ends of the retaining groove. Rotary cutting is understood to be a machining process with a rotating cutting movement on a relatively stationary workpiece using a rotating cutting tool with a geometrically defined cutting edge, for example circular saws with a circular saw blade or milling with a peripheral milling cutter. In rotary cutting, machining takes place with a circular cutting movement assigned to the tool and any feed movement, wherein the rotational axis of the cutting movement maintains its position relative to the tool regardless of the feed movement.The three-dimensional shape of the locking element can be adapted to the shape of the retaining groove, so that corresponding surfaces can face one another and, in particular, can bear against one another flatly. Preferably, the locking element is essentially based on a cuboid basic shape, so that the locking element is inserted into the retaining groove outside the rounded run-out areas of the retaining groove, in particular in a movement-resistant manner, thereby making the production of the locking element more cost-effective. This utilizes the finding that a smaller extension of the locking element in the transverse direction can also be sufficient to provide the locking functionality of the locking element.The extent of the locking element, for example, can be dimensioned essentially solely with regard to its locking functionality and the ability to withstand the forces expected in this case, making it entirely possible for the extent of the locking element to be selected to be smaller than the extent of the retaining groove. Instead of producing the retaining groove with a pin-shaped milling cutter moving in the transverse direction, the diameter of which corresponds in particular to the extent of the retaining groove in the thickness direction, it is possible to produce the retaining groove with a circular saw or peripheral milling cutter plunging into the panel body, since rounded inlet areas at the ends of the retaining groove can be permitted. This allows for faster and more cost-effective production of the retaining groove.

[0026] In a further embodiment, the retaining groove has a cross-sectional area, particularly a substantially rectangular one, that can be produced by milling in a sectional plane spanned by the longitudinal and transverse directions. For example, in the case of panels that are very narrow in the transverse direction, the entire transverse extension of the retaining groove can be used to accommodate the locking element. This avoids the need for rounded entry areas that remain exposed.

[0027] A further embodiment of the invention relates to a method for producing a panel, which can be designed and developed as described above, in which the retaining groove is created by rotary machining with a cutting tool that is immersed in the panel body on the short side of the panel body and rotates about a rotation axis running in the thickness direction, wherein the cutting tool is immersed in the panel body at a distance from the first edge and the second edge, is subsequently moved linearly in the transverse direction relative to the panel body, and the cutting tool subsequently emerges from the panel body at a distance from the first edge and the second edge. The method can be designed and developed in particular as explained above with reference to the panel.The retaining groove, which only runs over a large portion of the short side due to rotary machining, and the locking element accommodated in the retaining groove, enable a break-resistant and run-through-proof panel with good and material-friendly locking. The cutting tool has cutting teeth with a main cutting edge pointing essentially in the radial direction with respect to the axis of rotation and two secondary cutting edges pointing essentially in opposite axial directions, with the two secondary cutting edges, in addition to the main cutting edge, engaging the panel body in a cutting and / or smoothing manner to create the retaining groove. The thickness of the cutting teeth in the thickness direction can be essentially wedge-shaped in the circumferential direction, so that the tooth flanks of the cutting teeth pointing in the thickness direction can form clearance surfaces for a suitable wedge angle of the secondary cutting edges.The secondary cutting edges and the main cutting edge can share a common cutting surface. With the help of the secondary cutting edges, the surfaces of the retaining groove created by the main cutting edge and facing in the thickness direction can be finished in the same machining step, thereby facilitating the insertion of the locking element into the retaining groove. By smoothing the surfaces facing one another with the help of the secondary cutting edges, a variation in surface roughness and friction coefficients of the surfaces can be reduced. Preferably, the cutting tool has cutting teeth with radial extensions of different lengths in the axial direction relative to the axis of rotation, wherein the cutting teeth in particular have a radial profile for the simultaneous creation of both a receiving space and a fastening space for the retaining groove.As a result, one part of the cutting tooth can penetrate less deeply into the material of the panel body, for example, to create part of the receiving space, while another part of the cutting tooth, offset in the axial direction, can penetrate more deeply into the material of the panel body, for example, to additionally create the fastening space. The invention is explained below by way of example with reference to the accompanying drawings using preferred embodiments.

[0028] They show: Fig. 1 : a schematic plan view of an end area of ​​a panel, Fig. 2 : a schematic sectioned side view of the panel from Fig. 1 , Fig. 3 : a schematic sectioned side view of the panel from Fig. 2 during production and Fig. 4 : a schematic sectional side view of a detail of the panel from Fig. 1 with an inserted locking element.

[0029] The Fig. 1 The panel 10 shown can be used, for example, as a flooring laminate, to cover a surface of a room. The panel 10 has, on its respective long sides running in the longitudinal direction 30, a tongue and groove 12 on the one hand and a tongue and groove extension 14 on the other. A nominal width B is provided between the long sides of the panel 10, wherein for the nominal width B between the edges of the panel 10 on the long sides, the tongue and groove 12 and the tongue and groove extension 14 are disregarded and considered non-existent. In particular, the panel 10 has, on the short sides running in the transverse direction 32, a locking hook 16 on the one hand and a spring body 18 that can interact with such a locking hook 16 on the other. For example, on the short side with the locking hook 16, a retaining groove 20 is provided, into which a locking element 22 can be inserted in a movement-proof manner.The retaining groove 20 does not extend over the entire nominal width B, but only over a partial distance b 0 , so that between the retaining groove 20 and the long side with the bung groove 12 there remains a first reinforcement region 24 with an extension t 1 in the transverse direction 32 and between the retaining groove 20 and the long side with the bung extension 12 there remains a second reinforcement region 26 with an extension t 2 in the transverse direction 32. The retaining groove 20 can be produced by a groove cutter 40 which is immersed in the short side of a panel body 28 of the panel 10 and is designed in the manner of a circular saw or peripheral milling cutter, so that rounded run-out regions 31 with an extension b 2 in the transverse direction 32 are produced at the ends of the retaining groove 20. The extension b 1 of the retaining groove 20 remaining between the outlet regions 31 can essentially correspond to the extension of the locking element 22 in the transverse direction 32.

[0030] As in Fig. 2 As shown, the retaining groove 20 can have different depths in the longitudinal direction 30 at different heights in a thickness direction 34 of the panel body 28. The retaining groove 20 thus has a receiving space 36 adjoining the short side of the panel body 28 in the longitudinal direction 30 and a fastening space 38 protruding from the receiving space 36 in the longitudinal direction 30 into the interior of the panel body 28, which differ in their extent in the thickness direction 34. The extent of the receiving space 36 in the thickness direction 34 is greater than the extent of the fastening space 38 in the thickness direction 34.

[0031] As in Fig. 3 As shown, the stepped retaining groove 20 can be produced with the aid of a groove cutter 40 designed in the manner of a circular saw or a peripheral milling cutter. The groove cutter 40 has a cutting tool 42, on the radial outer side of which cutting teeth 44 are provided. The cutting teeth 44 are profiled with a stepped radial outer surface, resulting in main cutting edges 46 that are offset in the radial direction. The receiving space 36 with the shorter extension in the longitudinal direction 30 and the fastening space 38 with the greater extension in the longitudinal direction 30 can thus be produced in a common manufacturing step. In addition, the cutting teeth 44 have secondary cutting edges 48 pointing in the thickness direction 34, so that the entire retaining groove 20 can be produced with a defined surface.The retaining groove 20 can be spaced far enough in the thickness direction 34 from an upper side 52 of the panel body 28 that the cutting tool 42 of the grooving cutter 40 can be guided past the locking hook 16. At the same time, the retaining groove 20 is spaced far enough in the thickness direction 34 from an underside 50 of the panel body 28 that sufficient strength of the panel body 28 is also provided in the region of the retaining groove 20. Preferably, the retaining groove 20 is created with the aid of the grooving cutter 40, while the upper side 52 of the panel 10 points downward and the underside 50 of the panel 10 points upward, so that the locking hook 16 covering the cutting teeth 44 above can divert separated chips downward.

[0032] As in Fig. 4As shown, the locking element 22 can have a fastening projection 60 pressed into the fastening space 38 of the holding groove 20. If necessary, the locking element 22 can also be pressed into a part of the receiving space 36 of the holding groove 20 facing the fastening space 38. The locking element 22 has a locking web 54 with a locking lug 56 which, when locked with another panel, can slide along the outside of the other panel and can be elastically pivoted towards the receiving space 36 of the holding groove 20 and, if necessary, completely or partially into a receiving pocket kept free by the locking element 22. When the designated relative position of the panel 10 to the other panel is assumed, the locking web 54 can elastically snap out of the receiving space 36 so that the locking lug 56 can engage in a corresponding locking groove 58 and bring about a locking connection.

Claims

1. Panel for covering a surface of a room, comprising a panel element (28) extending in a longitudinal direction (30) and in a transverse direction (32) for transferring use loads introduced at an upper side (52) of the panel element (28) to a lower side (50) of the panel element (28) facing the surface of the room, wherein the upper surface (52) is spaced apart from the lower side (50) in a thickness direction (34), with a nominal width B of the panel element (28) between a first edge extending in the longitudinal direction and a second edge of the panel body 28 extending in the longitudinal direction, a retaining groove (20) extending in an end face short side of the panel element (28) in the transverse direction (32) with an extension b0 in the transverse direction (32); and a locking element (22) inserted into the retaining groove (20), in particular immovably, wherein the panel element (28) comprises at the first edge a bung groove (12) extending into the panel element (28) and at the second edge a bung projection (14) projecting from the panel element (28), wherein a first reinforcing area (24) with an extension t1 in the transverse direction (32) is formed between a first end of the retaining groove (20) facing the first edge in the transverse direction (32), wherein the reinforcing area (24) is free of the retaining groove, wherein a second reinforcing area (26) with an extension t2 in the transverse direction (32) is formed in the transverse direction (32) between a second end of the retaining groove (20) facing the second edge in the transverse direction (32), wherein the reinforcing area is free of the retaining groove, with the proviso that t1 + b0 + t2 = B, characterized in that for the extension b0 of the retaining groove (20) in the transverse direction (32) with respect to the nominal width B of the panel element (28) 0.50 ≤ b0 / B ≤ 0.97, in particular 0.75 ≤ b0 / B ≤ 0.95, preferably 0.85 ≤ b0 / B ≤ 0.93 and particularly preferably b0 / B = 0.90 ± 0.02 applies, wherein for the first reinforcing area (24) 0.005 ≤ t1 / B ≤ 0.090, in particular 0.015 ≤ t1 / B ≤ 0.050, preferably 0.020 ≤ t1 / B ≤ 0.030 and particularly preferably t1 / B = 0.025 ± 0.002 and / or for the second reinforcing region (26) 0.005 ≤ t2 / B ≤ 0.090, in particular 0.015 < t2 / B < 0.050, preferably 0.020 ≤ t2 / B ≤ 0.030 and particularly preferably t2 / B = 0.025 ± 0.002 applies, and wherein t1 < t2, in particular 0.75 ≤ t1 / t2 ≤ 0.99, preferably 0.80 ≤ t1 / t2 ≤ 0.95 and particularly preferably 0.85 ≤ t1 / t2 ≤ 0.90 applies.

2. Panel according to claim 1, characterized in that for an extension b1 of the locking element (22) in the transverse direction with respect to the nominal width B of the panel element (28) 0.40 ≤ b1 / B ≤ 0.95, in particular 0.50 ≤ b1 / B ≤ 0.90, preferably 0.60 ≤ b1 / B ≤ 0.80 and particularly preferably b1 / B = 0.70 ± 0.05.

3. Panel according to any one of claims 1 or 2, characterized in that a frictional engagement of the locking element (22) in the retaining groove (20) is achieved exclusively by means of clamping forces point in the thickness direction (34).

4. Panel according to any one of claims 1 to 3, characterized in that the locking element (22) comprises a latching web (54) which can be elastically bent at least partially in the direction into the retaining groove (20).

5. Panel according to any one of claims 1 to 4, characterized in that the retaining groove (20) comprises a receiving space (36) adjoining an end face of the short side for receiving a part of the locking element (22), in particular for temporary receiving an elastically flexible latching web (54) of the locking element (22), and a fastening space (38) adjoining the side of the receiving space (36) facing away from the end face for fastening a fastening projection (60) of the locking element (22) in a frictional and / or form-fitting manner, wherein the extension of the fastening space (38) in the thickness direction (34) is smaller than the extension of the receiving space (36) in the thickness direction (34).

6. Panel according to claim 5, characterized in that the locking element (22) abuts at both surfaces of the receiving space (36) facing in the thickness direction (34), in particular with a clamping force, wherein in particular the locking element (22) comprises a receiving pocket extending into the receiving space (36) for temporarily receiving an elastically bendable latching web (54) of the locking element (22).

7. Panel according to any one of claims 1 to 5, characterized in that the panel element (28) comprises at the short side forming the retaining groove (20) a locking hook (16) projecting in the longitudinal direction (30) from the short side of the panel element for latching into a retaining groove (20) of a further panel.

8. Panel according to any one of claims 1 to 7, characterized in that the retaining groove (20) comprises in a cross-sectional plane spanned by the longitudinal direction (30) and the transverse direction (32) at the ends of the retaining groove (20) facing in the transverse direction (32) a rounded feed-out area which can be produced by rotary machining.

9. Panel according to any one of claims 1 to 7, characterized in that the retaining groove (20) comprises in a cross-sectional plane spanned by the longitudinal direction (30) and the transverse direction (32) an in particular rectangular cross-sectional area which can be produced by milling.

10. Method of producing a panel according to any one of claims 1 to 8, in which the retaining groove (20) is formed by rotary machining by use of a chip-removing tool (42) engaging into the panel element (28) at the short side of the panel element and rotating about an axis of rotation extending in the thickness direction (34), wherein the cutting tool (42) engages into the panel element (28) at a distance from the first edge and the second edge, subsequently is linearly moved in the transverse direction (32) relative to the panel element (28), and subsequently the cutting tool (42) exits from the panel element (28) spaced from the first edge and the second edge, characterized in that the cutting tool (42) comprises cutting teeth (44) comprising, with respect to the axis of rotation, a major cutting edge (46) facing in a substantially radial direction and two minor cutting edges (46) facing in substantially opposite axial directions, wherein, in addition to the main cutting edge (46), the two minor cutting edges (48) engage in the panel element (28) in a chip-removing and / or smoothing manner in order to produce the retaining groove (20).

11. Method according to claim 10, wherein the cutting tool (42) comprises cutting teeth (44) having radial extensions of different widths in the axial direction with respect to the axis of rotation, wherein in particular the cutting teeth (44) have a radial profiling for simultaneously producing both a receiving space (36) and a fastening space (38) of the retaining groove (20).