Abstract:
An arrangement which comprises: first and second panel-shaped pieces of flooring for joining together, said pieces resting on a sub-floor and having profiles along mutually meeting edge portions which, on the first piece, consist of a groove and a projection located thereunder, and on the second piece a tongue insertible in the groove, and also a recess accommodating the projection; wherein said projection, at its outer, free edge, is of greater thickness transversely of the plane of extent of the flooring piece than at its inner edge connected with remaining parts of the piece; and wherein the underside of the projection lies flush with the remainder of the underside of the flooring piece.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a Continuation-In-Part of U.S. patent application Ser. No. 09/297,761, filed May 7, 1999, now U.S. Pat. No. 6,670,019. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to an arrangement for joining together first and second panel-shaped pieces of flooring resting on a sub-floor, the pieces having profiles along mutually meeting edge portions which, on the first piece, consist of a groove and a projection located thereunder, and on the second piece a tongue insertible in the groove, and also a recess accommodating the projection. 
     The present invention has for its object to improve the arrangement intimated by way of introduction such that it can be manufactured simply and rationally, that it will have an improved unifying effect between adjacent pieces of flooring material even if the flock or other unifying material were to be damaged, and that, in addition, laying of the flooring material is simplified. In particular, the present invention has for its object to design the arrangement such that the unifying force between two joined pieces of flooring material increases if an attempt is made to displace them away from one another when they are lying flat on a sub-floor. 
     SUMMARY OF THE INVENTION 
     The objects forming the basis of the present invention will be attained if the arrangement intimated by way of introduction is characterized in that the projection, at its outer, free edge, is of greater thickness transversely of the plane of extent of the flooring piece than at its inner edge connected with remaining parts of the piece, and that the underside of the projection lies flush with the remainder of the underside of the flooring piece. 
    
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
     The present invention will now be described in greater detail hereinbelow with particular reference to the accompanying drawings. In the accompanying drawings: 
     FIG. 1 is a partial cross section or end elevation of an edge portion of a first piece of flooring; 
     FIG. 2 is a corresponding partial cross section or end elevation of a second piece of flooring material intended to be joined together with the first; 
     FIG. 3 shows two pieces of flooring material of the type shown in FIGS. 1 and 2 at the beginning of a joining operation; 
     FIG. 4 shows the pieces of flooring material according to FIG. 3 after a part of the joining operation; and 
     FIG. 5 shows the flooring material according to FIGS. 3 and 4 after completion of the joining. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     In the following description, use will be made of directional and positional disclosures such as upwards, downwards, upper and lower. These refer to those positions which the pieces of flooring material assume when they are located in the position of use on a sub-floor. Outwards, inwards, relate to directions in relation to the central portion of a piece of flooring material. Thus, outwards is taken to signify out towards or out from the edge of a piece, i.e. away from its central region, all seen in the plane of extent of the flooring piece. 
     FIG. 1 shows an end elevation or a vertical section through an edge portion of a first piece  1  of flooring material, which has an upper surface  2  and a lower surface  3 , where the lower surface is intended to rest on a sub-floor  4  (FIGS.  3 - 5 ). 
     Analogous with that described with reference to FIG. 1, a second piece  5  of flooring material has an upper surface  6  and a lower surface  7  which is intended to rest on the sub-floor  4 . 
     The upper surfaces  2  and  6  are the upwardly facing surfaces of the flooring material which have been provided with an aesthetically attractive pattern or color and which, moreover, are designed to function as a wearing course or surface. While not being apparent from the drawings, there is suitably provided, on the lower surfaces  3  and  7 , some form of barrier layer which, in dampness variations in the core material  8  of the flooring material, rigidify so that the core material, by being united with the decorative layer or wearing surface, will not be warped. 
     The decorative layer, the wearing surface, the barrier layer and the core material  8  are produced in accordance with known, conventional techniques. 
     The first piece of flooring material has, along one edge portion, a profile which includes a groove  9 . Correspondingly, the second piece  5  of flooring material has, along an edge portion which is intended to be joined together with the edge portion of the first piece of flooring material, a tongue  10  which may be accommodated in the groove  9 . 
     The groove  9  in the first piece  1  of flooring material has an upper defining surface  11 , a lower defining surface  12  and an inner defining surface  13 , where the term “inner” signifies that it is turned to face towards an inner, central portion of the piece  1  of flooring material. The upper and lower defining surfaces  11  and  12 , respectively, are suitably parallel with each other and with the upper surface  2  of the flooring piece  1  and its lower surface  3 . The inner defining surface is substantially at right angles to the plane of extent of the flooring piece and has more or less rounded transitions to the upper and lower defining surfaces  11  and  12 , respectively, of the groove. 
     Above the groove  9 , the first piece  1  has an upper edge surface  14  which, in the illustrated embodiment, is at right angles to the upper side  2  of the flooring piece, and a lower edge surface  15  which may also be at right angles to the upper side  2  of the flooring piece, but which also, as is the case in FIG. 1, inclines somewhat outwards in a direction from above and downwards. 
     Beneath the groove  9 , the first piece  1  has, in its profile, a projection  16  whose underside coincides with or may be seen as an extension of the lower surface  3  of the piece  1  proper. The projection  16  has an upper surface  17  which, with its inner end, connects to the lower edge surface  15  and which, with its outer end, connects to the outermost edge surface  18  of the flooring piece. The projection  16  is of lesser thickness transversely of the plane of extent of the first piece at its inner region where it connects to remaining parts of the first flooring piece than is the case at its outer region in connection with the outermost edge surface  18 . This thus implies that a is &lt;b. This also implies that the upper surface  17  will have an inclination so that it rises in a direction away from the central portion of the first piece out towards the outermost edge  18 . 
     It will further be apparent from FIG. 1, that the distance e from the lower defining surface  12  of the groove and the underside  3  of the first piece is equal to or greater than the height b of the outer edge of the projection  16 , i.e. e≧b. Further, the height d of the groove  9  and the distance c from its upper defining surface  11  up to the upper side  2  of the first piece  1  are approximately equal. Finally, it suitably further applies that e&gt;d. 
     In the profile of the second flooring piece, there is provided above the tongue  10  a recess  19  which inwardly, i.e. in a direction towards the central portion of the piece  5 , is defined by an edge surface  20  which, when pieces  1  and  5  are united, is disposed to abut against the upper edge surface  14  on the first piece  1 . It is thereby at right angles to the upper surface  6  of the second flooring piece  5 , which is parallel with its lower surface  7 . Downwardly, the recess  19  is defined by the upper defining surface  21  of the tongue, which is parallel with the upper and lower surfaces  6  and  7 , respectively, of the second flooring piece  5 . The relative vertical position between the upper defining surface  11  of the groove  9  and the upper defining surface  21  of the tongue  10  is such that, when the first piece  1  and the second piece  5  are joined together on a planar substrate, surface contact prevails between the defining surfaces  11  and  21 . In the same joined position, the edge surfaces  14  and  20  also abut against one another, so that a tight joint is formed. 
     On the underside of the tongue  10 , there is a lower edge surface  22  which may be at right angles to the upper side  6  of the second flooring piece  5 , but which may also incline in relation to the vertical plane inwards in a direction from above and downwards. 
     For accommodating the projection  16  on the first piece, the second piece has a recess  23  which is defined inwardly by an inner edge surface  24  and which is defined upwardly by an upper defining surface  25 . The cross-sectional forms of the projection  16  and the recess  23  are either identical with one another or possibly complementary with one another. 
     In a first embodiment, the upper surface  17  of the projection  16  abuts, when pieces  1  and  5  are joined together, against the upper defining surface  25  of the recess  23 . On the other hand, there is, between the outermost edge surface  18  and the inner edge surface  24 , a narrower gap, which also applies to the lower edge surface  15  of the first piece and the lower edge surface  22  of the second piece. The reason for these gaps is to ensure a surface contact between the upper edge surface  14  on the first piece and the upper edge surface  20  on the second piece. The advantage is thereby afforded that the joint  28  (FIGS. 4 and 5) between the upper surfaces  2  and  6  of both pieces will be tight. 
     Normally, the core material in the two pieces  1  and  5  consists of MDF-panel, HDF-panel or similar panel material. The surface structure in such material will, on machining, be of such a nature that the friction between the two obliquely inclined surfaces  17  (on the projection  16 ) and  25  (at the recess  23 ) will be considerable. In addition to this frictional force, there will also be the frictional force between the upper defining surface  11  of the groove and the upper defining surface  21  of the tongue  10 . 
     In that the upper surface  17  of the projection  16  inclines upwards in a direction away from the central portion of the first piece, the second piece  5  must be lifted if an attempt is made to separate the two flooring pieces. However, such a lifting is prevented by the abutment of the tongue  10  against the upper defining surface  11  of the groove  9 . In such a case, there only remains a separation possibility if the two pieces are angled somewhat in relation to one another as intimated in FIGS. 3 and 4. The inclination of the upper surface  17  of the projection  16  and the upper defining surface  25  at the recess  23  thus entails that, in a laid, joined floor, the pieces  1  and  5  may be said to mechanically interlock. Expressed otherwise, the inclination implies that the normal force, and thereby the friction between the surfaces  17  and  25  increases if an attempt is made to shift away from one another two pieces  1  and  5  of the flooring material laying flat on a sub-floor. 
     In order to improve the joining together of the two pieces  1  and  5 , it is naturally, as far as is possible, a matter of preventing a relative slipping between the upper surface  17  of the projection and the upper surface  25  of the recess  23 . For this reason, one or both of the above-mentioned surfaces is provided with a slip-preventing or slip-impeding treatment or coating. Expressed otherwise, this implies that either or both of the surfaces  17  and  25  are coated with an agent which is adhesive, locking, elastic or resilient and which, for example, may consist of neoprene, resin, colophony (rosin) or a non-setting acrylic-based or silicon based sealant. Another coating with the same purpose may be realized if either or both of the surfaces are coated with a layer of binder, in which grains or small particles of sand, stone, glass or metal are then embedded. 
     In the embodiment according to FIGS. 3-5, the slip-preventing or slip-impeding treatment or coating is shown as a flock which is disposed on either or both of the surfaces  17  and  25 . In this context, the term flock is taken to signify a surface coating which includes a base layer of a suitable binder in which a large number of short fibers are secured so that they extend out from the base layer, in certain cases at right angles thereto. Such a flock can be achieved if the surface is coated with a tacky layer of the base coating, the fibers are charged electrostatically and applied, for example, by blowing, on the binder layer, whereafter the electrostatic charge is maintained so that the fibers extend out from the binder layer while this dries or sets. 
     In the embodiment according to FIGS. 3-5, the distance between the upper surface  17  of the projection  16  and the upper defining surface  25  of the recess  23  is sufficiently great to accommodate both the fibers included in the flock and its bonding layer. A suitably adapted tolerance is such that a certain normal force prevails between the two surfaces in the joined position of the flooring pieces  1  and  5 . This normal force also gives rise to a normal force between the upper surface  11  of the groove and the upper surface  21  of the tongue. The same tolerances are also suitable in the other described embodiments. 
     It will further be apparent from FIG. 5 that the outer edge  27  of the tongue has a slight distance to the inner defining surface  13  of the groove, and that there is further, between the lower edge surfaces  15  and  22 , a small gap, as also applies between the outermost edge surface  18  and the inner edge surface  24 . These gaps have been provided with a view to guaranteeing a tight joint  28  between the upper surfaces  2  and  6  of the flooring pieces. 
     It was mentioned above that the inclination of the upper surface  17  of the projection  16  and the upper defining surface  27  of the recess  23  gives an interlocking mechanical engagement between two joined pieces  1  and  5  as long as these lie flat on a substrate  4 . In order to realize convenient laying of the pieces, the tongue  10  has, on its underside, a bevel or rounding so that, in the vertical direction, it is thinner at its outer end  27  than is the case at its root between the edge surfaces  20  and  22 . This implies that, in the mounted state (FIG. 5) under the tongue  10 , there is still a cuneiform space  29  in the groove  9  on the underside of the tongue  10 . In the Figures, the underside  30  of the tongue  10  has been shown as approximately planar and directed with an angle of inclination which is approximately equal to the angle of inclination of the upper defining surface  25  of the recess  23  but counter-directed. Another way of expressing the bevelling or rounding would imply that the lower defining surface  30  of the tongue, for the greater part, is to be located over an arc with the center in the joint  28  and a radius which extends down to the line of intersection between the lower defining surface  12  of the groove and the upper edge of the lower edge surface  15 . 
     In that the lower surface  30  of the tongue  10  has been beveled or rounded in the described manner, the second flooring piece  5  may be simply joined together with the first when this is lying flat on a substrate  4  if the second piece is angled upwards somewhat as shown in FIGS. 3 and 4. The reverse naturally also applies, in that the second piece may readily be removed from the first by its one edge being lifted so that the second flooring piece is angled upwards. 
     It is to be understood that the invention is not limited to the illustrations described and shown herein, which are deemed to be merely illustrative of the best modes of carrying out the invention, and which are susceptible of modification of form, size, arrangement of parts and details of operation. The invention rather is intended to encompass all such modifications which are within its spirit and scope as defined by the claims.