Patent ID: 7003925

Claim:
A locking system for mechanical joining of floorboards having a core and a first joint edge portion and an opposite second joint edge portion, adjoining floorboards in the mechanically joined position having the first joint edge portion and the second joint edge portion joined at a vertical joint plane, said locking system comprising: a) for vertical joining of the first joint edge portion of a first floorboard and the second joint edge portion, of an adjoining second floorboard, a first mechanical cooperating locking device, and b) for horizontal joining of the first joint edge portion and the second joint edge portion, a second mechanical cooperating locking device which comprise a locking groove formed in the underside of said second floorboard and extending parallel with and at a distance from the vertical joint plane at said second joint edge portion and having a downward directed opening, and a strip integrally formed in one piece with the core of said first floorboard, which strip at said first joint edge portion projects from said vertical joint plane and at a distance from the joint plane has a locking element which projects towards a plane containing the upper side of said first floorboard and which has at least one operative locking surface for coaction with said locking groove, wherein: at least one operative locking surface of the locking element is essentially plane and located at the upper part of the locking element at a distance from the upper side of the projecting strip and faces the joint plane, the locking groove has at least one essentially plane operative locking surface which is located in the locking groove at a distance from the opening of the locking groove and which is designed to cooperate with said locking surface of the locking element in the joined position, the locking groove at the lower edge closest to the joint plane has an inclined or rounded lower groove part which extends from the locking surface of the locking groove and to the opening of the locking groove there is an intermediate surface between the upper side of the locking strip and the lower part of the locking surface of the locking element, and there is a space between the lower groove part and the intermediate surface.