Patent ID: 6898913

Claim:
A locking floorboard system for mechanical joining of floorboards, each of the floorboards having a body and an upper side of the body and a balancing layer on a rear side of the body, said system comprising: a first floorboard; a second floorboard; for horizontal joining of a first joint edge of the first floorboard to a second joint edge of the second floorboard at a vertical joint plane, a locking groove which is formed in an underside of said second floorboard and extending parallel with and at a distance from said vertical joint plane at said second joint edge and, a strip integrally formed with the body of said first floorboard, which strip at said first joint edge projects from said vertical joint plane and supports a locking element, which locking element projects towards a plane containing the upper side of said first floorboard and which locking element has a locking surface for coaction with said locking groove, wherein the strip is formed in one piece with the body of the first floorboard and for vertical joining of the first joint edge and the second joint edge, a tongue on the second floorboard which at least partly projects and extends from the vertical joint plane and, a tongue groove in the first floorboard adapted to coact with said tongue, the first and second floorboards having coacting upper and coacting lower contact surfaces, the upper and lower coacting contact surfaces comprise surface portions in said tongue groove and on said tongue, the upper and lower contact surfaces are essentially plane-parallel and extend essentially parallel with a plane containing the upper side of the floorboards, and the upper edge of the locking element is located in a horizontal plane, which horizontal plane is positioned below the upper contact surface and above the lower contact surface.