Patent Publication Number: US-2005115184-A1

Title: Panel connection

Description:
The invention relates to a panel, in particular a floor panel, having two tongues on one side and a groove on the opposite side, which tongues and groove are constructed in such a way that a number of panels can be connected to one another by the joining-together of said tongues and grooves, the tongue-and-groove connection being provided with interlatching means which prevent the separation of two panels.  
      Such a panel is known from DE 100 08 108 C1. In that instance, a wedge-shaped projection protrudes between the tongues from the base of the groove, said projection supporting the free ends of said tongues on the faces of the wedge.  
      This prior art poses problems in practice. The wedge-shaped projection requires considerable over-defining of the system, for which reason close tolerance requirements, which can be adhered to only with very high outlay, if at all, arise in the course of manufacture. The lengths of the tongues, the dimensions of the wedge-shaped projection and the individual angles, as well as the dimensions of all the elements in the vertical direction (the vertical direction is perpendicular to the panel), are extremely critical. The detachment of the panels from one another is also rather difficult, and associated with the risk of breakage, because of the tilting of the parts that occurs in the case of this prior art.  
      WO 01/48331 A1 describes a panel connection for, for example, floor panels, which has a tongue-and-groove connection that passes through a junction plane between adjacent panels, a so-called “locking peg on the floor side” being provided with latching means and said locking peg being functionally separate from the tongue-and-groove connection.  
      German Utility Model 200 18 760 indicates a tongue-and-groove connection for panels, in which a double tongue is used with a latching contour on the upper side of the panel.  
      The object underlying the invention is to provide a panel in which a reliable connection between adjacent panels can be produced by simple means. In this context, “simple means” signifies, in particular, simple tools, the least critical tolerances possible in manufacture, and also the lowest possible demands on the material of the panel. For the purposes of the invention, a “reliable connection” signifies, in particular, high long-term stability of the connection against drifting-apart of the panels, and also simple assembly of panels and relatively risk-free detachment of fitted panels from one another.  
      According to the invention, these goals are achieved, in a panel of the type initially mentioned, through the fact that, when two panels are in the joined-together condition, the tips of the two tongues protrude freely into the groove.  
      According to the invention, therefore, there is no need to form out, in the base of the groove, any additional functional element which, after the fashion of a wedge-shaped projection, for instance, as in the prior art explained above, engages between the tongues and at the same time supports the latter in the upward and downward directions.  
      According to a preferred configuration of the invention, provision is made for the base of the groove to be rounded. This benefits the elasticity of the tongue-and-groove connection as a whole, and also reduces the risk of cracks, i.e. benefits the stability of the connection.  
      Another preferred configuration of the invention makes provision for a vacant indentation having a depth of at least 1 mm, and preferably 1.5 mm, to be provided between the tongues in the joined-together condition.  
      This exemplified embodiment of the invention can also be further developed to the effect that the depth of the aforesaid vacant indentation amounts to at least 2 mm or at least 2.5 mm. The depth of this indentation largely determines the springiness of the tongues. Said springiness in turn determines, on the one hand, the stability of the interlatching arrangement and, on the other, the degree of resistance both when assembling two panels and when detaching them from one another.  
      Particularly simple detachment of the panels from one another comes about if, according to a preferred further configuration of the invention, the interlatching means are disposed on the upper tongue. In this case, a projection on said upper tongue preferably protrudes upwards and engages in a recess which is formed out in the upper boundary of the groove (i.e., the upper side wall of the groove) in the adjacent panel. In the assembled condition, a small clearance which is not filled up by the projection is, in this case, preferably left in the depression.  
      According to another preferred configuration of the invention, provision is made for the lower tongue to be shorter than the other tongue. This facilitates, in particular, the detachment of two panels from one another and, in the process, reduces the danger of breakage. When reference is made to “top” and “bottom” in the context of this invention, these indications relate to the usual use of the panels as a floor covering, and “top” therefore means vertically opposite to the direction of gravitational force, and “bottom” conversely means vertically in the direction of gravitational force, i.e. lying directly on the ground. If, on the other hand, the panels are not used on the floor, that is to say are used on a wall, for example, the terms are understood in an analogous manner, to the effect that “bottom” means: facing the wall.  
      In the case of the prior art initially mentioned, when two panels are in the assembled condition, there are cavities in the region of the junction plane, i.e. a section perpendicular to the surface of the panels in, or in the vicinity of, the junction plane intersects cavities. This is critical to the stability of the connection.  
      According to another, particularly preferred aspect of the present invention, therefore, provision is made for a region with continuous support from top to bottom to be provided at the junction plane of two panels which are joined together.  
      This means that a section perpendicular to the surface of the panels in, or in the vicinity of, the junction plane, intersects, at least over a certain width (that is to say, measured in the horizontal direction, i.e. in the direction parallel to the surface of the panels), material which is solid overall, that is to say intersects no cavities (air spaces or spaces with an adhesive filling or the like) worth mentioning.  
      According to another preferred configuration of the invention, provision is made for the lower tongue to be slightly rounded-off on the underside at its tip. This facilitates, in particular, the detachment of the panels from one another, but also their assembly. In this case, therefore, the lower tongue is preferably shaped asymmetrically at its tip, with a rounded-off portion on the underside.  
      Another preferred configuration of the invention makes provision for a lower bottom projection, which delimits the groove at the bottom, to protrude at least 1.5 mm beyond the tip of the lower tongue (distance  36 ) in the joined-together condition. 
    
    
      An exemplified embodiment of the invention will be described below with the aid of the drawings.  
       FIG. 1  shows, diagrammatically, a section through a first exemplified embodiment of a connection between two floor panels; and  
       FIG. 2  shows a diagrammatic section through a second exemplified embodiment of a connection between two floor panels. 
    
    
      In the drawings, components which correspond, and are functionally similar, to one another are provided with the same reference symbols.  
      The floor panels  10 ,  12  are represented, solely in the region of their tongue-and-groove connection, in  FIGS. 1 and 2 . It is understood that the panel  10  has a groove on its left side (not represented) like the panel  12 , and that, correspondingly, the panel  12  has a double tongue on its right side (not represented) like the panel  10 .  
      In accordance with  FIG. 1 , the tongue-and-groove connection has two tongues  14   a ,  14   b  which are constructed so as to be integral (in one piece) with the panel  10  and which jut out from the latter in the horizontal direction. The terms “horizontal” and “vertical” will be used here with reference to the use of the panels as a floor covering.  
      The lower tongue  14   b  is represented in the figure with a cross-hatched region  14   c  at its tip. This cross-hatching indicates that the horizontal length of the tongue  14   b  can be varied, approximately by the span of the cross-hatched region, something which will be explained in greater detail further on.  
      When the panels are assembled, the two tongues  14   a ,  14   b  engage in a groove  16  in the panel  12 . At its base  16   a , the groove  16  does not have any projection that comes into engagement with the two tongues  14   a ,  14   b  in the assembled condition. Rather, said groove  16  has a rounded-off base  16   a . This has a number of advantages: In contrast to a groove that has corners in the region of its base, the danger of cracks or even of a break is greatly reduced. Furthermore, the round configuration of the groove, coupled with high elasticity, permits a diminution in the cavity formed, and thus an improvement in the stability of the panel connection. In the exemplified embodiment represented, the base  16   a  of the groove is approximately semicircular in shape and merges tangentially into the parallel side faces of said groove  16 .  
      On its upper side, the upper tongue  14   a  has a projection  18  which engages in a latching manner in a depression  20  in the upper outrigger  12   b  of the panel  12 , in order to prevent separation of the panels  10 ,  12  in the horizontal direction in a force-locking manner. The connection therefore does not necessarily need any glue. In the assembled condition, a clearance is left in the depression  20 , as is represented.  
      This configuration of the interlatching means permits simple disengagement of the connection without the danger of breakage. Simple unlatching and also simple assembly are further benefited by the fact that the two tongues  14   a ,  14   b  engage freely in the groove  16 , that is to say a certain elastic relative movement of the two tongues towards one another is possible in the assembled condition. It has proved to be the case that, in spite of this elasticity, very satisfactory resistance of the connection to coming undone in the horizontal direction is nevertheless achieved with that construction of the tongue-and-groove connection which is represented. The interlocking on the upper side permits clean and close contact of the panels against one another over their entire lateral edges. When the connection is taken apart, the lower tongue  14   b  can be easily detached from the groove, without there being any danger of breakage, since it is neither latched in, nor pressed into a constrained location by a wedge.  
      The drawing also shows the junction plane  24  between the two connected panels  10 ,  12 . Located directly below the upper joining line between the two panels is a clearance  22  which may optionally accommodate glue and also, apart from that, promotes precise contact of the two panels in the region of their upper joining line.  
      Represented in the figure, next to, and to the right of, the junction plane  24 , is a region  26  in which a force vector acting vertically from above over the entire connection from top to bottom is completely absorbed by solid material. For this purpose, the regions which are cross-hatched in the figure are important: First of all, the figure shows a cross-hatched region  10   a  which can be described as a “feather-arm support”. Said region  10   a  is an integral (one-piece) constituent part of the panel  10 , i.e. the material of said panel  10  extends fully into the cross-hatched region  10   a . The only clearance then remaining between the tongues  14   a ,  14   b  is the indentation  32 . As has been mentioned above, it is possible, in a modification to the exemplified embodiment shown in the figure, to vary the cross-hatched region  10   a , i.e. the right-hand boundary of said region  10   a  can be altered, in accordance with the double arrow represented, towards the left or even towards the right. It is possible to alter the springiness of the tongues  14   a ,  14   b , depending upon the horizontal length of the region  10   a . On the other hand, the size of the region  10   a  defines the region  26  over which, continuously from top to bottom, a force operating vertically in the region of the junction plane is absorbed, without cavities, by solid material. For this purpose, the bottom projection  12   a  of the right-hand panel  12 , which projection is represented at the bottom in the figure, is also significant. The material of the bottom projection  12   a  is formed out in a manner integral (in one piece) with the material of the right-hand panel  12 , and the horizontal length of said bottom projection  12   a  can be varied over the cross-hatched region, in which connection two possible extreme locations are represented in the figure:  
      In accordance with one extreme location, that bottom projection  12   a  of the panel  12  which is represented in a cross-hatched manner reaches as far as the junction plane  24 , but in the other extreme location, said bottom projection  12   a  is substantially shorter and reaches under the lower tongue  14   b  only by the span  36 , i.e. the lower bottom projection  12   a  is precisely long enough to come into plane-parallel contact, with satisfactory, stable support, with the lower face of the tongue  14   b . The bottom projection  12   a  is preferably constructed in such a way that it protrudes into the region  26  by more than 1 mm, and preferably more than 1.5 mm, in order to thus guarantee that a force vector acting perpendicularly (vertically) in the region  26  is absorbed at every point by material.  
      In the shaping of the panel connection, the dimensions are important. The figure shows said panel connection on a scale of 10:1. In the exemplified embodiment represented, the overall height of the two panels (in the vertical direction) amounts to 7 mm.  
      The horizontal length of the lower tongue  14   b  can likewise be varied within the bounds of the cross-hatched region  14   c . As is represented in the exemplified embodiment, the maximum horizontal length of the lower tongue  14   b  is less than the horizontal length of the upper tongue  14   a , i.e. the tip  30  of the lower tongue  14   b  lies closer to the junction plane  24  than the tip  28  of the upper tongue  14   a . The span  34 , i.e. the depth of the vacant indentation  32  with reference to the front end of the tongue  14   b , is critical to the elasticity of the lower tongue  14   b , which elasticity is significant, particularly when unlatching the connection. In the course of the unlatching operation, a panel is normally raised slightly. In the process, the lower tongue  14   b  has to deflect elastically a little. In order to benefit this possibility of deflection and to reduce the forces on the tongue  14   b , the latter is rounded-off on its underside, as is represented in the figure.  
      The horizontal length of the lower bottom projection  12   a , which can also be described as a “side of the groove” with reference to the groove  16 , is coordinated with the length of the lower tongue  14   b . One extreme combination is represented in the figure by those regions of the bottom projection  12   a  and tongue  14   b  which have single hatching. Another extreme combination is represented in the figure by the double-hatched (chequered) regions of said elements. In one preferred exemplified embodiment, what applies as regards the horizontal length of the tongue  14   b  is that at least half the latter protrudes into the region  26 . For accurate assembly, it is also advantageous to take the end face  10   b  of the panel  10 , which end face lies opposite the bottom projection  12   a , back behind the junction plane  24 .  
      That construction of the panel connection which is represented permits the use of less expensive materials than the comparable prior art (which requires more outlay, construction-wise). It is also possible, depending upon the choice of the variable dimensions explained above, to use lower-quality HDF as the material or even MDF as well. Compared with the prior art, the tongues  14   a ,  14   b  may be of relatively robust dimensions, i.e. their dimensions in the vertical direction may be relatively large. In the exemplified embodiment represented, the upper tongue  14   a  has a vertical height of about 1.3 mm (other than in the region of the projection  18 ), while the lower tongue  14   b  has a vertical dimension of 1.2 mm. When the floor panel has a thickness of 7 mm, dimensions of 1 to 1.4 mm are generally eligible for consideration for the upper tongue  14   a , and dimensions of 1 to 1.3 mm for the lower tongue.  
      In a modification to the exemplified embodiment described above, it is also possible for the interlatching means to be disposed on the lower arm  14   b , that is to say a downwardly pointing nose and a corresponding recess in the bottom projection  12   a  may be provided in an analogous manner. This variant is advantageous, in particular, when no unlocking of the panels is planned.  
       FIG. 2  shows a modification to the exemplified embodiment described above with the aid of  FIG. 1 . The features which are identical are immediately apparent from  FIG. 2 . Thus, for example, in the exemplified embodiment according to  FIG. 2 , the lower tongue  14   b  likewise protrudes less far into the groove  16  than the upper tongue  14   a . As already explained above, “lower” and “upper” mean that the first one lies closer to the ground on which the floor panel is disposed.  
      In a modification to the exemplified embodiment according to  FIG. 1 , the indentation  32  between the two tongues  14   a ,  14   b  has a different shape in the exemplified embodiment according to  FIG. 2 . On its inner side, the upper tongue  14   a  has an approximately sinusoidal profile (cf.  FIG. 2 ) from its tip  28  as far as the point of connection to the lower tongue  14   b . This sweeping curve, which avoids sharp angles, is designated by the reference numeral  32  in  FIG. 2 . This shaping of the underside of the upper tongue  14   a  leads to increased stability of the latter and to the avoidance of cracks when panels are taken apart. In the exemplified embodiment according to  FIG. 2 , the front tip  28  of the upper tongue  14   a  abuts against a point on the base of the groove  16 .  
      Furthermore, the upper outrigger ( 12   b ) of the panels is rounded-off in a bead-shaped manner in the exemplified embodiment according to  FIG. 2 . This configuration likewise benefits both the assembly and the taking-apart of the panels.