Patent Description:
Such floor panel assembly is known in the art and is for example described in <CIT>.

It is an object of the invention to improve the prior art floor panel assembly, especially with respect to the water tightness of the joining members. The invention is described in the independent claim <NUM>.

To obtain this object, the tongue and groove are so adapted to each other that an upper surface of the tongue is urged against an upper wall of the groove.

This creates a tight fit between the tongue and groove in vertical direction, improving water tightness between the joining members, even if the panel edges of adjacent panels would have a small gap in horizontal direction.

One way of obtaining this is that the vertical size of the tongue is larger than the vertical size of the groove, in non-joined condition.

This means that the tongue must be compressed or bent in vertical direction in order to enable the tongue to be engaged in the groove. According to the invention, in the joined position of the panels, the upper surface of the tongue is in contact with the upper wall of the groove in a contact area, the contact area having a small inclination with respect to a corresponding area of the upper wall of the groove in the non-joined condition, and being substantially parallel thereto in the joined condition.

This inclination, which may vary for example between <NUM><NUM> and <NUM><NUM>, is downwardly in the direction towards the vertical plane VP. Downward bending of the tongue will then result in rotation of the upper surface of the tongue towards horizontal and thereby lowering the height of the tongue to adapt to the size of the groove.

If a clearance is present between the lower surface of the tongue and the lower wall of the groove in the area substantially below the contact area at the upper surface of the tongue, there is created sufficient room for downward displacement of the tongue if it is bent downwards.

The said contact area is at a distance from the vertical plane VP.

Due to this feature, the force exerted by the tongue on the panel portion above the groove is concentrated in the area near the bottom of the groove where resistance against deformation is much higher than at the opening of the groove. Thus, this features assist in minimizing upward deformation of the panel edge adjacent the seam between the panels, so that the panels fit smoothly with minimal or no height difference.

The upper surface of the tongue adjacent the vertical plane VP is lowered with respect to the upper surface at a distance from the vertical plane, by providing the upper surface of the tongue, adjacent to the vertical plane VP, with a notch parallel to the adjacent edge.

This notch in the upper surface of the tongue not only creates the contact area spaced from the vertical plane VP, but also reduces the bending resistance of the tongue. This bending resistance can be regulated by dimensioning this notch in dependence of the tongue dimensions and the rigidity of the material of the tongue. The tongue should bend but should also have sufficient bending resistance so as to exert and maintain pressure on the groove under all conditions of use.

In another embodiment, the tongue and groove are so adapted to each other that in the joined position there is a pressure line between a lower surface of the tongue and a lower wall of the groove at a distance from the vertical plane VP, substantially below the start of the contact area at the upper surface of the tongue, and wherein the lower wall of the groove may have a stepped surface.

This pressure line or area may provide an alternative or additional way of creating pressure between the upper surface of the tongue and the upper wall of the groove.

One possibility to obtain this is that the lower wall of the groove is provided with a ridge extending parallel to the adjacent edge of the panel, and the lower surface of the tongue may be provided with an indentation extending parallel to the adjacent edge of the panel and being adapted to receive the ridge of the groove at least partly.

In a specific embodiment, the floor panels are substantially rectangular and has opposite third and fourth edges adjacent to the opposite first and second edges, each floor panel being provided on at least the third edge with a third joining member and, on the opposite fourth edge, with a fourth joining member, the third and fourth joining members of two panels being vertical joining members and being joined to each other by a mainly vertical movement of the respective panel edges towards each other, the third and fourth joining members locking the panels at the adjacent edges at least in a direction perpendicular to the upper side and in a direction parallel to the upper side but perpendicular to the adjacent third and fourth edges in their joined position, the third and fourth joining members being provided with at least one locking element locking the third and fourth joining members to each other in the joined position, at least in said direction perpendicular to the upper side.

The joining members of the first and second edges of each panel may allow a joining of the first and second edges of two panels by bringing the first and second edges into engagement with each other in a relatively inclined position of the panels and then rotating said panels with respect to each other so as to bring the upper sides of both panels substantially in alignment with each other, thereby also bringing the vertical joining members of the third and fourth edges of the tilted panel and an adjacent panel into engagement.

The locking element may be a horizontal protrusion on the third or fourth edge protruding towards the fourth or third edge and engaging in a recess on the other of the third or fourth edge.

In a further development, the vertical joining members include a male and a female joining member, at least one of which is deformable, such as bendable for cooperation with the other of the male and female vertical joining members to create tension between them in the joined position. This create an additional locking force and/or water tightness of the connection. The female joining member may have a shape to force the lip(s) into a locking position. In case of two downward lips separated by a vertical notch, the female joining member may have an upward ridge or the like adapted to engage into the notch but being wider than the notch to force the lips away from each other into engagement with walls of the female member. This can also be obtained in case of a single lip, or if in the final joined position, the deformable male or female vertical joining member is deformed away from its resting position thereby creating pressure between the joining members.

Preferably, the contact area providing water tightness of the joint is as close as possible to the position where the upper surfaces of the panels meet and thus where water can enter the joint. If the contact area has a horizontal component, i.e. is between substantially horizontal surfaces, or surfaces having a horizontal component, this horizontal component contact area should be the first one of this type that any water entering the joint meets. This applies both to the horizontal and vertical joints.

The invention also includes a floor panel for use in the floor panel assembly as described above, and joining members for use on this floor panel.

Further details and advantages of the invention will follow from the below description with reference to the drawings showing an embodiment of the panel assembly according to the invention by way of example.

The drawings and in first instance <FIG> and <FIG> thereof, show a number of panels of an embodiment of the panel assembly according to the invention. In particular, <FIG> shows a first panel <NUM>, a second panel <NUM>, a third panel <NUM> and a fourth panel <NUM>. These panels are substantially rectangular and may both be square or elongated. The four panels <NUM> - <NUM> shown are elongated having a first edge <NUM> and an opposite second edge <NUM> that form the long edges and a third edge <NUM> and an opposite fourth edge <NUM> that are the short edges.

In principle the panel assembly is intended to form a floor covering, but the panels may also be used as wall panels, ceiling panels or panels for covering other surfaces. These surfaces may be indoor or outdoor surfaces. The panels may be constructed as flexible/bendable/resilient LVT-like panels for forming a laminate flooring which is known in the art. These panels are normally used to imitate planks or tiles of natural material, such as wood, stone or any other material. Generally these panels comprise a core of relatively resilient and/or bendable material, in particular material including a soft plastics material. The plastics material may be polyvinylchloride, polyvinyl chloride/polyvinyl acetate copolymer, polythene, polypropylene or any other suitable polymer, copolymer or mixture thereof. The material would normally incorporate one or more additives such as are conventionally used in the formulation of PVC floor coverings including: plasticizers, extending oils, stabilizers (e.g. metal salts), pigments, and fillers (e.g. ground limestone, or other finely divided inorganic materials such as mica, slate, china clay. The plastics could be engineered with other materials, such as natural or synthetic fibers or flour to obtain composite material such as WPC (Wood Plastic Composite) or plastic material mixed with carpet waste.

The core of these panels may be covered by a decorative layer formed for example from transfer foil. The décor may also be formed in a different way, for example by printing directly and/or digitally on the core, and/or by finishing the core by embossing, chafing or the like. An upper surface <NUM> is formed thereby. A lower surface <NUM> of the panels may be formed by another layer, for example a water-proof coating or sheet. However, the invention is also applicable for panels made of plastic or other material with or without separate upper and/or lower layers. The thickness of the panels may for example vary between <NUM> and <NUM>, the panel shown in the drawings is <NUM>.

The edges <NUM> - <NUM> of each panel <NUM> - <NUM> are provided with joining members to join the panels to each other to obtain a floor covering in which the panels are coupled to each other substantially without the formation of a gap. For this purpose, the third edge <NUM> of each panel is provided with a third or male vertical joining member <NUM>, the fourth edge <NUM> with a fourth or female vertical joining member <NUM> (see <FIG> and <FIG>), whereas the first edge <NUM> is provided with a first or male horizontal joining member <NUM> and the second edge <NUM> with a second or female horizontal joining member <NUM>.

The first and second edges <NUM>, <NUM> with first and second joining members <NUM>, <NUM> are shown schematically in <FIG>. These joining members <NUM>, <NUM> are such that they allow a joining of the first and second edges <NUM>, <NUM> of two panels <NUM>, <NUM> by bringing male joining member <NUM> in contact with female joining member <NUM> of a panel or of two panels which are already installed on the surface. In <FIG>, panel <NUM> is brought into engagement with panels <NUM> en <NUM>. The first male joining member <NUM> is brought in engagement with the second female joining member <NUM> while the panel <NUM> is held in a relatively inclined position, whereafter panel <NUM> with the male joining member <NUM> is rotated with respect to the other panels <NUM> and <NUM> so as to bring the upper surfaces <NUM> of the panels substantially in alignment with each other. This method is also known as the "angling in" joining method. In principle, it would also be possible to angle in a female joining member onto a male joining member of a panel already installed. Other methods of bringing the joining members into engagement with each other, such as horizontal shifting, are conceivable as well.

In the embodiment shown in <FIG>, the joining members <NUM>, <NUM> comprise locking means which prevent the panels <NUM>, <NUM> from drifting apart in a direction parallel to their surfaces <NUM>, <NUM> and perpendicularly to their edges <NUM>, <NUM>. These locking means are configured such that they exert a force urging the panels towards each other (i.e. perpendicular to their edges) while the panels are in their joined condition. This force counteracts the formation of gaps between the panels, in particular at the position near the upper surface <NUM> where the panels meet each other. This position may be exactly at the upper surface in the situation of <FIG>, but in case the upper edges of the panels are machined for example to form a V-groove (see <FIG>, <FIG>), U-groove or other lowered area between the panels, the panel edges will meet at a distance from the upper surface <NUM>. The panels <NUM>, <NUM> will contact each other in a plane, here a substantially vertical plane VP through surfaces <NUM> and <NUM> which here extend substantially vertical.

<FIG> also shows that the first male joining member <NUM> includes a tongue <NUM>, while the second female joining member <NUM> includes a groove <NUM> which is able to receive at least a portion of tongue <NUM> therein so as to lock the panels with respect to each other in a direction perpendicularly to surfaces <NUM>, <NUM>, i.e. in vertical direction. The shape of the tongue and groove <NUM>, <NUM> may have all kinds of configurations and orientations as long as they include surfaces that restrict movements in a direction perpendicularly to surfaces <NUM>, <NUM>.

The horizontal lock of the panels away from each other is accomplished by means of a lip <NUM> below groove <NUM> projecting from panel <NUM> beyond vertical plane VP and carrying near its free edge an upper protrusion <NUM> engaging into a downwardly open groove or recess <NUM> positioned behind tongue <NUM> of panel <NUM>.

<FIG> and <FIG> show the first and second joining members <NUM>, <NUM> in more detail. It is shown that the lower surface of tongue <NUM>, especially in an area before vertical plane VP is rounded, and has a heel <NUM> ending into the front wall of downwardly open groove <NUM>. This heel <NUM> cooperates with an upward wall <NUM> of upper protrusion <NUM> to accomplish the horizontal lock at these edges <NUM>, <NUM> and also might urge panels <NUM>, <NUM> toward each other so as to be pressed against each other at the position of substantially vertical surfaces <NUM> and <NUM> forming a seam which is closed, also when forces are exerted on panels <NUM>, <NUM> trying to separate the panels at their first and second edges <NUM>, <NUM>. Above protrusion <NUM> and beyond lip <NUM> there is a gap or clearance towards the other panel so that contact between the panel edges is limited to designated areas.

One of the designated surfaces is an upper surface <NUM> of tongue <NUM> engaging in the joined position with an upper wall <NUM> of groove <NUM>. As is shown in <FIG> contact between these surfaces is only in a limited contact area <NUM> at a distance from vertical plane VP. This is accomplished by lowering upper surface <NUM> of the tongue adjacent the vertical surface <NUM> or vertical plane VP, by providing a notch <NUM> in the upper surface <NUM> extending parallel to the adjacent edge. This notch <NUM> may be one tenth to a few tenths of a millimetre deep and the width is approximately between a quarter and half of the length of tongue <NUM>, thus leaving a contact area <NUM> of approximately half of the upper surface of the tongue remote from vertical plane VP. This means that any pressure exerted by tongue <NUM> onto upper wall <NUM> of groove <NUM> is exerted near the bottom, i.e. deepest part, of groove <NUM> only. This reduces any deformation of the panel portion above groove <NUM> to a minimum as the moment of inertia on this panel portion is minimum, due to the shorter distance to the bottom of groove <NUM>, i.e. near the solid portion of the panel.

A pressure is exerted by tongue <NUM> on upper wall <NUM> of groove <NUM> by urging tongue <NUM> upwardly due to the engagement of heel <NUM> of the tongue with upward wall <NUM> of protrusion <NUM> and also with a recess <NUM> in the upper surface of lip <NUM>. The upper surface <NUM> of tongue <NUM> at the position of contact area <NUM> is slightly inclined downwardly in a direction towards vertical plane VP in the non-joined position, see <FIG> at angle α. This inclination α may for example be <NUM><NUM> - <NUM><NUM>, preferably <NUM><NUM> - <NUM><NUM>, most preferably approximately <NUM><NUM> with respect to the upper wall <NUM> of the groove <NUM> or in this case with respect to the horizontal. The vertical distance between the highest part of the upper surface <NUM> and the lowest point of the heel <NUM> of the tongue is greater than the vertical distance between the upper wall <NUM> of groove <NUM> and the bottom of the recess <NUM> in the lip <NUM>. Thus, when tongue <NUM> is inserted into groove <NUM>, tongue <NUM> should be deformed slightly, for example by compression or bending, in order to allow the joining members <NUM>, <NUM> to engage. In this case, when joining members <NUM>, <NUM> are joined, the tongue is bent and as a result the contact area <NUM> of tongue <NUM> is rotated to an orientation in which it extends substantially parallel to upper wall <NUM> of groove <NUM>, in this case substantially horizontal. Due to this rotation of a part of the tongue, the height of the tongue is reduced (the highest part of the tongue <NUM> is remote from vertical plane VP beyond which the deformation starts) whereby the joining members <NUM>, <NUM> are allowed to fully engage.

Alternatively, it is conceivable to shape upper wall <NUM> of groove <NUM> such that there is only pressing contact between upper surface <NUM> of tongue <NUM> and upper wall <NUM> of groove <NUM>, for example by creating a notch in upper wall <NUM> at the open end of groove <NUM>, or by incline upper wall <NUM>, such that wall <NUM> is higher at its open end than at its closed end. The other way around, upper surface <NUM> of tongue <NUM> can be configured at an inclination of e.g. <NUM><NUM> - <NUM><NUM>, such that when the tongue is slightly deformed and/or rotated, the free end of tongue <NUM> is still higher than its base, so that there is contact only at a distance from vertical plane VP.

In order to create freedom of movement for tip <NUM> of tongue <NUM> within groove <NUM>, there is a distance between tip <NUM> of tongue <NUM> and bottom <NUM> of groove <NUM> in the joined position of joining members <NUM>, <NUM>, and there is also a clearance <NUM> between a lower surface <NUM> of tongue <NUM> and the recess <NUM> or upper wall of lip <NUM>, lower wall of groove <NUM>. One could also say that in the non-joined condition the vertical distance between the upper surface <NUM> of the panel and the highest part of the upper surface <NUM> of the tongue is smaller that the vertical distance between the upper surface <NUM> of the panel and the upper wall <NUM> of groove <NUM>, and the deformation of the joining members will be such that these vertical distances will be equal, so that the upper surfaces of adjacent panels will be on equal levels.

Thus, in the joined position of the joining members, the designated contact areas are between.

Of course, it would be possible to split up or reduce these contact areas by providing lowered portions within these contact areas. For example, the substantially vertical surfaces <NUM>, <NUM> could be made such that the contact is concentrated in the upper part thereof, ensuring that the seam is closed also in critical tolerance situations.

In <FIG> it is shown that in the recess <NUM> in lip <NUM>, i.e. in the lower wall of groove <NUM> there is formed a ridge <NUM>, which has no function here as it does not have contact with the lower surface <NUM> of tongue <NUM>. Here it is the result of machining the joining member <NUM> with different tools under different angles.

In the alternative embodiment of <FIG> not according to the invention, it is shown that the pressure between the upper surface <NUM> of tongue <NUM> and the upper wall <NUM> of groove <NUM> can additionally or alternatively be accomplished by creating a pressure line or area between the lower surface of tongue <NUM> and the lower wall of groove <NUM> extending parallel to the respective edge, for example by the ridge <NUM> or otherwise raised area on lower wall <NUM> of groove <NUM> urging tongue <NUM> upwards when it is inserted into groove <NUM>. Due to the elasticity of the material of ridge <NUM>, it can be deformed downwardly to enable entry of the tongue (see dotted line and arrow in <FIG>). However, additionally or alternatively, tongue <NUM> can be bent downwardly by upper wall <NUM> of groove <NUM> at a position slightly beyond the pressure line enabled by the gap or clearance <NUM> between lower surface <NUM> of tongue <NUM> and lower wall <NUM> of groove <NUM>. Ridge <NUM> is positioned substantially below the start of contact area <NUM> between upper surface <NUM> of tongue <NUM> and upper wall <NUM> of groove <NUM>.

Ridge <NUM> may have a substantially triangular cross-section so as to create the pressure line between tongue <NUM> and groove <NUM>. Other cross-sections are conceivable, for example having a rounded or flat top. The ridge <NUM> may be more or less pronounced. The ridge <NUM> could also be created on lower surface <NUM> of tongue <NUM>. The same is true for contact area <NUM> between upper surface <NUM> of tongue <NUM> and upper wall <NUM> of groove <NUM>. This may be defined by a notch or the like in the upper wall of the groove adjacent to the vertical plane VP, such that contact is only created where this notch or inclined area ends. In <FIG> the contact area <NUM> of the tongue extends substantially the whole length thereof.

As is shown in <FIG>, lower surface <NUM> of tongue <NUM> could be provided with a recess or indentation <NUM> extending parallel to respective panel edge <NUM>, <NUM> and being adapted to at least partly receive ridge <NUM> when joining members <NUM>, <NUM> are in their joined condition. Upper surface <NUM> of tongue <NUM> is here uninterrupted so that contact with upper wall <NUM> of groove <NUM> is substantially over the entire area of the upper surface of the tongue, but also here notch <NUM> may be provided to concentrate the contact at the bottom of groove <NUM>.

A close contact between the tongue and the groove can also be accomplished by dimensioning the vertical size of the tongue and groove, such that the vertical size of the tongue in a vertical cross section is larger than the vertical size of the groove in the corresponding cross section, i.e. in the joined position. To obtain this joined position, at least one of the tongue and groove must deform to adapt the vertical sizes to correspond, so that the tongue fits into the groove. If the tongue deforms, this can be accomplished by compression or bending. Bending can be promoted by shaping the tongue, for example by providing the tongue with a horizontal notch. Compression can be accomplished by proper material selection.

<FIG> and <FIG> show third and fourth vertical joining members <NUM>, <NUM> at short edges <NUM>, <NUM> of panels <NUM>, <NUM>. The panels meet each other near their upper surface <NUM> in a vertical plane VP. The fourth or female joining member <NUM> comprises a recess <NUM> extending at a distance below the upper surface <NUM> of panel <NUM> and parallel to respective panel edge <NUM> to limit a contact area between vertical wall surfaces <NUM>, <NUM>. A lower panel portion is extended beyond vertical plane VP into a protruding lip <NUM> including in its upper surface a depression <NUM> adjacent to the vertical plane VP. In the embodiment shown, depression <NUM> has a flat bottom parallel to edge <NUM>. On its free end lip <NUM> is provided with an upward projection <NUM> having an upright wall <NUM> bordering depression <NUM> and an upper surface <NUM>. On the free end of lip <NUM> remains a free space <NUM> to first edge <NUM> of the other panel in order to ensure that the seam between vertical wall surfaces <NUM>, <NUM> near upper surface <NUM> of panels <NUM>, <NUM> can be closed.

The third or male vertical joining member <NUM> comprises a downward protrusion <NUM> having in this case a substantially flat lower surface extending parallel to first edge <NUM>. The shape and dimension of this downward protrusion <NUM> is such that it will fit into depression <NUM> of female joining member <NUM> when first and second joining members <NUM> and <NUM> are in their joined condition. The lower surface of protrusion <NUM> forms the lowest point of first joining member <NUM> where the distance from upper surface <NUM> of the panel is at a maximum. The lower surface of the protrusion <NUM> might or might not contact the bottom of depression <NUM> in its joined position, at least it is not necessary to have contact. Inclined wall <NUM> together with the engagement of vertical wall surfaces <NUM> and <NUM> provide vertical support to panel <NUM>. On the lower side of first edge <NUM> is a downwardly open recess <NUM> which is sufficiently large to take up upward projection <NUM> on lip <NUM> of female joining member <NUM> with either a clearance (as shown) or with contact between surface <NUM> and the upper wall of recess <NUM>.

In this embodiment, female joining member <NUM> is provided with a vertical locking element <NUM> in the form of a protrusion extending horizontally parallel to the adjacent panel edge and protruding towards the other panel <NUM>, in this case towards a wall <NUM> defining one side of protrusion <NUM>. In this vertical wall <NUM>, there is created an undercut <NUM> to take up locking element <NUM>. The inclined lower surface <NUM> of protrusion <NUM> and inclined lower wall <NUM> of undercut <NUM> engage with each other and lock panel edges <NUM>, <NUM> with respect to each other in vertical direction, in cooperation with the engagement of the downward protrusion <NUM> and upward surface <NUM> of protrusion <NUM> bordering the depression <NUM>. The downward protrusion <NUM> and the depression <NUM> are formed such that protrusion <NUM> can enter depression <NUM> by a downward displacement in combination with a slightly sideways displacement and/or by deformation of the locking element <NUM>, downward protrusion <NUM> and/or lip <NUM>. To further improve the water tightness of the connection one can vary the angles of the engaging surfaces of protrusion <NUM> and/or of depression <NUM> (also different angles of engaging surfaces) to create increased pressure there between. Creating increased pressure due to other measures such as different sizes is also conceivable.

Locking element <NUM> and undercut <NUM> could also be positioned in other places where upright or substantially vertical surfaces of third and fourth joining members <NUM>, <NUM> are adjacent to each other, such as on one of the upright walls of the upward protrusion <NUM> on lip <NUM>. In the embodiment shown, one could also say the depression <NUM> with wall <NUM> forms a locking element engaging in a recess or undercut formed below locking element <NUM> by wall <NUM>.

Locking element <NUM> as shown is integrated in the joining member, i.e. made in one piece with the panel from the same material. It may however also be made separately and be attached or connected to the panel. It may extend along the whole length of first edge <NUM>, but especially if it is made separately, it is possible to provide a plurality of short locking elements distributed along the length of edge <NUM>, or even only one short locking element substantially in the middle of second edge <NUM>. The length and placement of the locking element depends on various factors, in particular the length of edges <NUM>, <NUM>, the material of the panels and the particular use of the panel assembly. The use of one or more narrow locking elements <NUM> facilitate a connection between two panel edges when the edges are moved towards each other in a non-parallel orientation, for example, if one panel is folded down as is disclosed here. Also the locking effect is better when there is a high local load because if one locking element is disengaged due to the high local load, the other locking elements will remain locked and keep the edges together. Of course, if locking element is interrupted along the length, it cannot provide water tightness to the joint. In that case, water tightness should be effected between other surfaces.

<FIG> show a variation of the vertical joining members <NUM>, <NUM>. In this case, the downward protrusion <NUM> of joining member <NUM> is split at the bottom by a substantially vertical notch <NUM> extending parallel to the adjacent edge and creating two resilient lips <NUM>, <NUM> which can slightly bend towards and away from each other. For example when the protrusion <NUM> enters the depression <NUM> to join the vertical joining members <NUM>, <NUM>, one or both lips <NUM>, <NUM> might be urged to bend inwardly. When protrusion <NUM> has fully entered depression <NUM>, the lip(s) is or are allowed to bend at least partly back to form a vertical lock together with the walls <NUM>, <NUM> of the depression <NUM>. These lips <NUM>, <NUM> of the protrusion <NUM> and walls <NUM>, <NUM> of the depression <NUM> can be shaped to form a strong or weaker vertical lock, and also additional water tightness of the connection.

As is shown in <FIG>, at the bottom of the depression <NUM> there may be formed an upwardly converging ridge <NUM> which is forced to enter notch <NUM> when the protrusion <NUM> is almost in its lowest position (from <FIG> on), thereby forcing at least lip <NUM> adjacent wall <NUM> away from the other lip (from <FIG> on) as ridge <NUM> becomes wider than notch <NUM>. In this way, it is not necessary to first bend the lips <NUM>, <NUM> towards each other to create the lock and/or water tightness when in the final position.

<FIG> shows a variation of <FIG>, in which there is no ridge <NUM> provided in depression <NUM>, but lip <NUM> adjacent wall <NUM> of locking element <NUM> (the lip furthest away from the centre of panel <NUM>) is pre-shaped such that in the final joined position lip <NUM> is bent away (see arrow) from its resting position (shown in dashed lines) so that it is positioned against wall <NUM> with tension to strengthen the vertical lock and (water) tightness of the joint. Thus, the width of protrusion <NUM> is larger than that of depression <NUM>, at least at one corresponding level, so that the width of the protrusion <NUM> must be reduced elastically by bending a part (i.e. lip <NUM>) to enter its joined position in the depression <NUM>. In the embodiment of <FIG> lip <NUM> is more slender than lip <NUM> which is more massive, especially at its upper end, thereby increasing the resistance to bending.

Surface <NUM> of lip <NUM> preferably does not extend beyond surface <NUM> in horizontal direction, i.e. remains behind this surface <NUM>, so that during a downward movement of this panel the lip will not engage with upper surface <NUM> of the other panel already laid. If there is a small horizontal distance between surface <NUM> and extreme part of surface <NUM>, it will not engage upper surface <NUM> even if the adjacent sides of panel <NUM> rae not exactly square.

<FIG> shows another variation in which the downward protrusion <NUM> of the male joining member <NUM> as a whole is formed as a bendable lip <NUM> which is tensioned in its final joined position against wall <NUM> of locking element. This is the result of the fact that the distance between the front face of lip <NUM> and vertical plane VP is smaller than the distance between wall <NUM> and VP at the corresponding level, so that lip <NUM> must be deformed to equal the distance. Depression <NUM> is large enough to take of the bending deformation of lip <NUM>, but horizontally supports the upper side of lip <NUM> to urge the panels in engagement with each other near their upper sides at vertical plane VP.

Of course, it would in principle be possible that the walls <NUM> and/or <NUM> of the female joining member <NUM> are deformable, i.e. bendable to provide the same kind of tension between the male and female joining members <NUM>, <NUM>.

Claim 1:
Floor panel assembly comprising sheet-shaped floor panels (<NUM>-<NUM>), which floor panels are provided with a plurality of edges (<NUM>-<NUM>), wherein a first edge (<NUM>) of a first panel (<NUM>) and a second edge (<NUM>) of a second panel (<NUM>) are equipped with joining members (<NUM>, <NUM>) which allow a joining of the first and second edges (<NUM>, <NUM>) of the two panels (<NUM>, <NUM>) by bringing these into engagement with each other, preferably in a relatively inclined position of the panels (<NUM>, <NUM>) and then rotating said panels (<NUM>, <NUM>) with respect to each other, so as to bring the upper sides of both panels (<NUM>, <NUM>) substantially in alignment with each other and have them meet at a vertical plane VP, the first edge (<NUM>) being provided with a tongue (<NUM>) and the second edge (<NUM>) with a groove (<NUM>) adapted to receive the tongue (<NUM>) therein so as to lock the panels (<NUM>, <NUM>) at the adjacent edges at least in a direction perpendicular to the upper side and in a direction parallel to the upper side but perpendicular to the adjacent first and second edges in their joined position, wherein the tongue (<NUM>) and groove (<NUM>) are so adapted to each other that an upper surface (<NUM>) of the tongue (<NUM>) is urged against an upper wall (<NUM>) of the groove (<NUM>) and is in contact with the groove (<NUM>) in a contact area (<NUM>), wherein said contact area (<NUM>) is at a distance from the vertical plane VP;
wherein the contact area (<NUM>) has an inclination (α) with respect to a corresponding area of the upper wall (<NUM>) of the groove (<NUM>) in the non-joined condition, and is substantially parallel to the corresponding area of the upper wall (<NUM>) of the groove (<NUM>) in the joined condition, wherein said inclination (α) is downwardly in the direction towards the vertical plane VP;
wherein the upper surface (<NUM>) of the tongue (<NUM>) adjacent the vertical plane VP is lowered with respect to the upper surface (<NUM>) of the tongue (<NUM>) at a distance from the vertical plane VP, by providing the upper surface (<NUM>) of the tongue (<NUM>), adjacent to the vertical plane VP, with a notch parallel to the adjacent edge,
characterized in that the width of the notch is between a quarter and half of the length of tongue (<NUM>), thus leaving the contact area (<NUM>) of approximately half of the upper surface (<NUM>) of the tongue (<NUM>) remote from vertical plane VP.