Locking system, floorboard comprising such a locking system, as well as method for making floorboards

1. A flooring system comprising a plurality of rectangular floorboards having a locking system for mechanical joining of such floorboards, the floorboards have a thickness and exhibit a body, opposite first and second joint edge portions, a balancing layer on the rear side of the body, adjoining floorboards in a mechanically joined position having their first and second joint edge portions 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 portion of an adjoining second floorboard, mechanically cooperating connectors in the form of a tongue groove formed in the first joint edge portion and a tongue formed in the second joint edge portion, and

b) for horizontal joining of the first joint edge portion of the first floorboard and the second joint edge portion of the adjoining second floorboard, mechanically cooperating connectors, which comprise:

a locking groove formed in an underside of said second floorboard and extending parallel to and at a distance from the vertical joint plane at said second joint edge portion and having a downward opening, and

a strip integrally formed with the body of said first floorboard and having a width, said strip projecting at said first joint edge portion from said vertical joint plane and at a distance from the vertical joint plane having 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,

the strip forming a horizontal extension of the first joint edge portion below the tongue groove,

wherein the locking surface of the locking element is inclined relative to a horizontal plane at an angle of at least 45°, and

wherein the tongue groove depth is less than 0.4 times the thickness of the floorboards, and wherein the width of the strip is less than 1.3 times the thickness of the floorboards.

2. The flooring system according to claim 1 , wherein the floorboards have a thickness of about 7-10 mm.

3. The flooring system according to claim 1 , wherein the floorboards comprise a surface layer on an upper side of the body, wherein a thickness of the surface layer is about 0.2-0.8 mm.

4. The flooring system according to claim 1 , wherein a thickness of the body is about 6-9 mm.

5. The flooring system according to claim 1 , wherein the thickness of the balancing layer is about 0.1-0.6 mm.

6. The flooring system according to claim 1 , wherein the tongue groove depth is larger than a width of the tongue as measured outwards from the vertical joint plane to a vertical limiting plane which coincides with a tip of the tongue.

7. The flooring system according to claim 1 , wherein the locking system is adapted such that the tongue is anglable into the tongue groove and the locking element is insertable into the locking groove by means of a mutual angular movement of the first floorboard and the second floorboard while maintaining contact between joint edge portions of the first and second floorboards close to a boundary line between the vertical joint plane and the upper side of the first and second floorboards.

8. The flooring system according to claim 1 , wherein the locking system is adapted such that the floorboards are joinable through a snap action, which is incurred by a horizontal displacement of the first floorboard and the second floorboard towards each other, whereby the strip is forced to move downwards as a direct result of the bringing together of the first and second floorboards and then snaps up and allows the locking element to enter the locking groove.

9. The flooring system according to claim 1 , wherein the floorboards on the upper side of the body have a surface layer, which coacts with the balancing layer.

10. The flooring system according to claim 1 , wherein the locking surface of the locking element has a vertical extent which is at least 0.1 times the thickness of the floorboards.

11. The flooring system according to claim 1 , wherein the tongue groove exhibits an outer part with a vertical height and an inner, narrower part with a vertical height whose average value across the horizontal extent of the inner part is less than 0.8 times the vertical height of the outer part.

12. The flooring system according to claim 10 , wherein the locking surface of the locking element has a vertical extent which is less than 0.2 times the thickness of the floorboards.

13. The flooring system according to claim 1 , wherein the strip, across at least half of a part of the strip which in the horizontal direction is located between the locking surface and the vertical joint plane, exhibits a strip thickness which is less than 0.25 times the thickness of the floorboards.

14. The flooring system according to claim 12 , wherein the floorboards are mechanically joinable to adjoining boards along all four sides by means of said locking system.

15. The flooring system according to claim 6 , wherein the locking groove has a larger width than the locking element.

16. The flooring system according to claim 1 , wherein the floorboards are of a size of about 1.2 m×0.2 m.

17. The flooring system according to claim 1 , wherein the strip, across at least half of the strip which in the horizontal direction is located between the locking surface and the vertical joint plane, exhibits a constant thickness.

18. The flooring system according to claim 1 , wherein the balancing layer comprises a plastic material.

19. The flooring system according to claim 18 , wherein the balancing layer comprises a fibre reinforcement.

20. The flooring system according to claim 1 , wherein at least a part of the first joint edge portion at the rear side of the body is without the balancing layer.