Patent ID: 7516588

Claim:
A locking system for mechanical joining of floorboards, in which locking system the joined floorboards have a horizontal plane which is parallel to a floor surface and a vertical plane which is perpendicular to the horizontal plane, which locking system has mechanically cooperating locks for vertical joining parallel to the vertical plane and for horizontal joining parallel to the horizontal plane of a first and a second joint edge, and in which locking system the vertical lock comprises a tongue which cooperates with a tongue groove and the horizontal lock comprises a locking element with a locking surface which cooperates with a locking groove, each of the first and the second joint edge has upper and lower joint edge portions positioned between the tongue and the floor surface, the upper joint edge portions being closer to the floor surface than the lower joint edge portions, and in which locking system, when the floorboards are joined and pressed towards each other the upper joint edge portion in the first joint edge overlaps the lower joint edge portion in the second joint edge, wherein when the floorboards are joined and pressed towards each other, the two upper joint edge portions are spaced from each other, wherein the floorboards have a surface layer of laminate and a core of fiber-board-based material, and that the upper overlapping joint edge portion is formed in this surface layer and in the upper portions of the core next to the surface layer, and that the vertical extent of the overlapping portion is less than 0.1 times the floor thickness.