Patent ID: 7596920

Claim:
A floor panel comprising a rectangular plate which, at least at two opposite sides, is provided with coupling parts in the form of a tongue at the one side and a groove at the opposite side, the coupling parts comprising integrated mechanical locking means in the form of a protrusion shaped on the tongue and a tip bordering the groove which is formed by the extraction of the material along a longer arm of the groove, a bearing surface ( 9 ) of the lip being inclined to a center of the floor panel and downwards, the bearing surface ( 9 ) of the lip ( 8 ) at the longer arm of the groove ( 5 ) being concave on an arc with a first radius (r1), the first radius having a point of engagement which is situated at an upper border of the floor panel ( 1 ), the protrusion ( 7 ) of the tongue ( 6 ) having, in cross-section, the form of a circular section with a third radius (r3) which is shorter than the first radius, and a lower part of the lip ( 8 ) and at a lower part of the floor panel ( 1 ) from a side of the circular protrusion ( 7 ) having second bearing surfaces ( 9 ′) inclined in relation to a vertical plane into one direction, at a first acute angle (α); each of said second bearing surfaces ( 9 ′) being substantially parallel to each other; an internal surface ( 10 ) of a recess along the longer arm of the groove, situated close to the lip ( 8 ), is concave on an arc with a second radius (r2), which is longer than the first radius (r1); the bearing surface, the first radius, the third radius and the first acute angle being selected to ensure that, when one floor panel is coupled to another floor panel, said one floor panel and said another floor panel can displace freely when changes in humidity occur; whereby possibility of warping of a floor or the destruction of the couplings is substantially eliminated.