Patent ID: 6851241

Claim:
A locking system for mechanical joining of floorboards at a vertical joint plane, said floorboards having a core, a front side, a rear side and opposite joint edge portions, of which a first joint edge portion is formed as a tongue groove which is defined by upper and lower lips and has a bottom end, and a second joint edge portion is formed as a tongue with an upwardly directed portion at a free outer end, the tongue groove, seen from the vertical joint plane, having the shape of an undercut groove with an opening, an inner portion and an inner locking surface, and at least parts of the lower lip being formed integrally with the core of the floorboard, and the tongue having a locking surface which is formed to coact with the inner locking surface in the tongue groove of an adjoining floorboard, when two such floorboards are mechanically joined, so that front sides of the floorboards are positioned in a common horizontal surface plane and meet at the vertical joint plane directed perpendicular thereto, wherein at least a major part of the bottom end of the tongue groove, seen parallel with the horizontal surface plane, is positioned further away from the vertical joint plane than is an outer end of the tongue, that the inner locking surface of the tongue groove is formed on the upper lip within the undercut portion of the tongue groove for coaction with the corresponding locking surface of the tongue, which locking surface is formed on the upwardly directed portion of the tongue to counteract pulling apart of two mechanically joined floorboards in a direction (D 2 ) perpendicular to the vertical joint plane, the lower lip has a supporting surface for coaction with a corresponding supporting surface on the tongue at a distance from the bottom end of the undercut groove, said supporting surfaces being intended to coact to counteract a relative displacement of two mechanically joined boards in a direction (D 1 ) perpendicular to the horizontal surface plane, all parts of the portions of the lower lip which are connected with the core, seen from a point where the horizontal surface plane and the vertical joint plane intersect, are located outside a plane which is located further away from said point than a locking plane which is parallel therewith and which is tangent to the coacting locking surfaces of the tongue groove and the tongue where said locking surfaces are most inclined relative to the horizontal surface plane, and the upper and lower lips and tongue of the joint edge portions are designed to enable disconnection of two mechanically joined floorboards by upward pivoting of one floorboard relative to the other floorboard about a pivoting center close to the point of intersection between the horizontal surface plane and the vertical joint plane for disconnection of the tongue of one floorboard and the tongue groove of the other floorboard.