# Patent

## Title
Mechanical locking system for floor panels

## Abstract

Floor panels provided with a mechanical locking system comprising a separate material in order to reduce snapping resistance during vertical displacement. For example, a separate flexible tongue, the flexible tongue including an inner part, which is connected to a holding groove at a second edge, and an outer flexible snap tab that extends upwardly and in the connected state into a cavity under a protruding tongue for locking a first and a second floor panel to each other in a vertical direction.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
The present application is a continuation of U.S. application Ser. No. 14/646,567, filed on May 21, 2015, which is a U.S. National Stage of International Application No. PCT/SE2013/051374, filed on Nov. 21, 2013, which claims the benefit of Swedish Application No. 1251322-2, filed on Nov. 22, 2012. The entire contents of each of U.S. application Ser. No. 14/646,567, International Application No. PCT/SE2013/051374, and Swedish Application No. 1251322-2 are hereby incorporated herein by reference in their entirety.


TECHNICAL FIELD
The invention generally relates to the field of mechanical locking systems for floor panels and building panels especially floor panels with mechanical locking systems, which may be locked by a vertical displacement.
FIELD OF APPLICATION OF THE INVENTION
Embodiments of the present invention are particularly suitable for use in floating floors, which are formed of floor panels which are joined mechanically with a locking system integrated with the floor panel, i.e. mounted at the factory, that are made up of one or more upper layers of veneer, decorative laminate, powder based surfaces or decorative plastic material, an intermediate core of wood fibre based material or plastic material and preferably a lower balancing layer on the rear side of the core. The following description of known technique, problems of known systems and objects and features of the invention will therefore, as a nonrestrictive example, be aimed at this field of application and in particular at paper based or paper free laminate flooring formed as rectangular floor panels with long and shorts sides adapted to be mechanically joined on both long and short sides. The long and short sides are mainly used to simplify the description of the invention.
The panels may be squared and may have more than four sides, which are not parallel or perpendicular to each other.
It should be emphasized that embodiments of the invention may be applied to any floor panel preferably at the short edges and it may be combined with all types of known locking system on the long edges, where the floor panels are adapted to be joined using a mechanical locking system connecting the long edges in a vertical and/or horizontal direction. Embodiments of the invention may also be used for joining building panels, which preferably comprise a board material, such as wall panels, ceilings, and furniture components and similar.
BACKGROUND OF THE INVENTION
Floating floor panels such as laminate floor panels are generally joined mechanically by means of so called mechanical locking systems. These systems comprise locking means, which lock the panels horizontally and vertically on all edges.
The main advantages of floating floors with mechanical locking systems are that they are easy to install. Several versions of locking systems are used on the market and there is a continuous demand for improvements related to production costs and function.
DEFINITION OF SOME TERMS
In the following text, the visible surface of the installed floor panel is called “front side”, while the opposite side of the floor panel, facing the sub floor, is called “rear side”. The edge between the front and rear side is called “joint edge”. By “horizontal plane (HP) or principal plane” is meant a plane, which extends parallel to the outer part of the surface layer. Immediately juxtaposed upper parts of two adjacent joint edges of two joined floor panels together define a “vertical plane (VP)” perpendicular to the horizontal plane. By “horizontally” is meant parallel to the horizontal plane and by “vertically” parallel to the vertical plane. By “up or upwardly” is meant towards the front side and by “down or downwardly” is meant towards the rear side. By “inwardly” is meant essentially horizontally towards the inner part of the panel and by “outwardly is meant essentially horizontally and away from the inner part of the panel. By “strip panel” is meant a panel comprising a strip and a locking element. By “fold panel” is meant a panel, with a locking groove configured to cooperate with a locking element for horizontal locking that is adapted to be angled and displaced vertically during locking.
KNOWN TECHNIQUE AND PROBLEMS THEREOF
The description of the known art below is in applicable parts also used in embodiments of the invention.
For mechanical joining of long sides as well as short sides in the vertical and horizontal direction several methods and locking systems may be used. One of the most used methods is the angle-snap method and one of the most used locking systems is a system made in one piece with the core. The long sides are installed by angling. The panel is then displaced in locked position along the long side. The short sides are locked by horizontal snapping.
An alternative method is the so-called angling-angling method whereby long and short sides are locked with angling.
Recently a new and simpler method has been developed where all floor panels may be joined with just an angling of the long edges. This installation method generally referred to as “fold down” installation. An example of such a known “fold down” installation method is shown in FIGS. 18 and 19 of WO 03/016654. A problem with this method is that a flexible snap tab, arranged at an edge of a first panel, must be pressed inwardly by a sharp upper edge of an adjacent edge of a second panel.
WO 2006/043893 (Välinge Innovation AB) FIG. 13d describes a fold down locking system comprising a flexible tongue on the fold panel that locks against a rigid tongue formed in the edge of the adjacent strip panel. The flexible tongue has an inclined sliding surface at its outer and lower part that during folding slides against the rigid tongue and presses the flexible tongue inwardly into a sliding groove. The size of the sliding surface is limited by the thickness of the flexible tongue. This thickness is not possible to increase since such an increased thickens will also increase the thickness of the displacement groove and this will have a negative impact of the strength of the locking system.
SUMMARY OF THE INVENTION
An objective of certain embodiments of the present invention is to provide an improved mechanical locking system, which may by locked by vertical folding, comprising a flexible tongue with an outer flexible snap tab connected to an edge of a fold panel.
More specifically the object is to provide a vertical snap locking system, which creates less snapping resistance during locking.
The above objects of certain embodiments of the invention are achieved wholly or partly by a mechanical locking systems and floor panels, as described herein. Further embodiments of the invention are evident from the claims, description and drawings.
A first aspect of the invention comprises a set of floor panels that are mechanically connectable to each other at a first and a second edge of a first and a second floor panel respectively, wherein upper edges of said first and second edge in a connected state define a vertical plane. The first edge is provided with a protruding tongue formed in one piece with the core of the first floor panel. Said protruding tongue extends beyond the vertical plane. The second edge is provided with a separate flexible tongue comprising an inner part, which is connected to a holding groove at the second edge, and an outer flexible snap tab that extends upwardly and in the connected state into a cavity under the protruding tongue for locking the first and the second floor panel to each other in a vertical direction. The first edge comprises a strip with a locking element. The second edge comprises a locking groove, which is open towards a rear side of the second floor panel that faces a subfloor. A locking surface of the locking element is configured to cooperate, in the connected state, with a locking surface of the locking groove for locking the first and the second floor panel to each other in a horizontal direction, which is at right angles to the first and second edge. The first and the second floor panel are mechanically connectable by a vertical displacement towards each other, wherein the flexible snap tab and the protruding tongue are configured to cooperate during said displacement such that at least a part of the flexible snap tab is, in a first stage, resiliently displaced, towards the second edge, by the protruding tongue, and that the flexible snap tab is, in a second stage, displaced towards the first edge to obtain the connected state.
The invention provides the advantages that the flexible snap tab may be displaced by an inclined guiding surface located on a rather soft tongue made of the same material as the core and such displacement may be made without contact with the hard upper panel surface.
The protruding tongue is preferably arranged above the strip. The protruding tongue may be arranged at the vertical plane and extend from the vertical plane.
The separate flexible tongue with the snap tab requires a smaller holding groove as compared to the displacement groove shown in WO 2006/043893 (Välinge Innovation AB) FIG. 13d. The smaller holding groove makes the connection stronger since the distance between the holding groove and the locking groove may be increased.
The protruding tongue preferably comprises an inclined or rounded guiding surface at its upper and outer part.
The protruding tongue and the snap tab are preferably configured such that the initial contact, during said vertical displacement, between the protruding tongue and the snap tab is at an upper part of the snap tab. The initial contact at the upper part decreases the force needed for the displacement of the snap tab, or a part of the snap tab. The decreased force makes it easier to connect the floor panels.
There may be a space between the upper parts of the protruding tongue and the second edge.
There may be is a space between the upper part of the strip and the second edge.
The protruding tongue preferably comprises a locking surface at its lower part that is inclined and in locked position in contact with the flexible snap tab.
The locking surface of the protruding tongue is preferably arranged above the strip.
The flexible tongue may be glued into the holding groove.
The holding groove may comprise an upper wall and a lower wall and an inner wall extending between the upper and the lower wall. A glue is preferably provided at the upper, the lower and the inner wall. The flexible tongue may be glued to the upper, the lower and the inner wall.
The locking surface of the locking element and/or the locking surface of the locking groove preferably extend in an essentially vertical direction or at angle in a range of about 0 to about 45 degrees to the vertical plane.



BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will by way of example be described in more detail with reference to the appended schematic drawings, which shows embodiments of the present invention.
FIGS. 1-5b illustrate known systems.
FIGS. 6a-6c illustrate a first embodiment of the invention.
FIGS. 7a-7b illustrate a second embodiment of the invention.
FIGS. 8a-8b illustrate a third embodiment of the invention.



DETAILED DESCRIPTION
To facilitate understanding, several locking systems in the figures are shown schematically. It should be emphasized that improved or different functions may be achieved using combinations of the preferred embodiments.
A known “fold down” installation method is described in FIGS. 1-4. Locking of short edges 1b, 1c takes place with a scissors like movement where a flexible tongue 30 is displaced inwardly gradually from one edge to the other edge when a long side of a panel 1c in one row is connected by angling to an adjacent panel 1a in a previously installed row. A flexible snap tab 33, which in most cases is made of a plastic section, is during folding bended horizontally along the joint. A part of the snap tab is during folding pressed inwardly, as shown in FIG. 1, and other parts are in contact with the adjacent edge, FIG. 2, or in an completely unlocked position, as shown in FIG. 4. The horizontal locking takes place when a locking element 8 located on a strip 6 on a first panel 1b, hereafter referred to as strip panel, cooperates with an adjacent second panel 1c, hereafter referred to as fold panel, such that the locking element 8 is inserted into a locking groove 14.
FIGS. 5a and 5b show that the flexible tongue 30 may be connected to an edge of the fold panel 1c or the strip panel strip panel 1b. 
From a production perspective it is an advantage if the flexible tongue 30 is connected to a fold panel 1c because it is easy to insert such a flexible tongue into a holding groove 32. There is no protruding strip 6 and the insertion of the flexible tonged may be made with an inserting equipment comprising rather simple guiding devices that guide the tongue into the holding groove 32. A problem with such a flexible tongue 30, as shown in FIG. 5a, is that the locking system is difficult to lock since the snap tab must be pressed inwardly by a sharp upper edge.
FIGS. 6a-6c show an embodiment of the invention. A strip panel 1b comprising a strip 6 and a locking element 8 which cooperates with a locking groove 14 in a fold panel 1c for horizontal locking of two adjacent edges of the fold panel 1c and the strip panel 1b is provided. The strip panel comprises a protruding tongue 10 with an upper inclined or rounded guiding surface 11 and a lower locking surface 12. The fold panel 1c comprises a flexible tongue 30 in a holding groove 32, which is open towards the vertical plane VP. The flexible tongue 30 has an inner part 34 connected into the holding groove 32 and a flexible snap tab 33 with a sliding surface 35 extending outwardly and upwardly. The sliding surface 35, that preferably is located at an upper part of the flexible snap tab, cooperates with the guiding surface 11 during a vertical displacement of the fold panel 6c and causes a pressure force that bends the flexible snap tab 33 inwardly towards the holding groove 32 as shown in FIGS. 6a-6b. The snap tab 33 snaps back toward its initial position and into the cavity 31 when the edges 1b, 1c are aligned horizontally and the lower locking surface 12 on the lower part of the protruding tongue 10 locks against the upper part of the snap tab 33 as shown in FIG. 6c. The flexible snap tab 33 and the protruding tongue 10 lock the edges vertically parallel to the vertical plane VP. The locking element 8 and the locking groove 14 lock the edges in a horizontal direction perpendicular to the vertical plane VP. The strip 6 and the protruding tongue 10 form a cavity 31 that in connected state accommodates an outer part of the flexible snap tab 33. The protruding tongue is preferably arranged above the strip, at the vertical plane and extends from the vertical plane. The locking surface of the protruding tongue is preferably arranged above the strip.
The inclined guiding surface 11 facilitates an easy locking since the flexible snap may not be in contact during locking with the upper sharp edge of the panel surface. The guiding surface may be used to facilitate an easy locking even in the case that a contact may exist during folding between the upper edge and the flexible snap tab 11.
The lower locking surface 12 may be inclined and the locking may be made with a pre tension such that the snap tab 11 in locked position is pressed against a lower part of the protruding tongue 10.
FIG. 7a shows that there may be a space S1 between the upper part of the tongue 10 and the adjacent panel edge. The vertical locking is accomplished with an upper contact point A between the protruding tongue 10 and the flexible snap tab 33, and a lower contact point B between the strip 6 and a lower edge of the fold panel 1c. The snap tab may be flexible or rigid depending on the design and material composition. Polymer materials are preferred and the flexible tongue may comprise several different materials in for example the inner part or in the snap tab. The flexible tongue 30 may comprise a knee joint 36 with increased flexibility that facilitates bending and/or displacement of the snap tab. The locking groove 14 and the holding groove 32 are preferably horizontally displaced, in order to obtain a strong locking system, and preferably with a distance D1 that is at least about 30% of the floor thickness T. The upper part of the locking groove 14 and the inner part of the holding groove 32 are preferably also displaced vertically with a distance D2.
FIG. 7b shows that there may be a space S2 between the upper part of the strip 6 and the lower edge of the adjacent fold panel 1c. The vertical locking is in this embodiment accomplished with a lower contact point B between the protruding tongue 10 and the flexible snap tab 33, and an upper contact point A between the protruding tongue 10 and an upper part of the fold panel 1c that overlaps the protruding tongue.
FIG. 8a shows an embodiment where the upper edges of the panels are in contact with each other and the guiding surface 11 extends downwardly from the panel surface. The knee joint 36 comprises a flexible material 37 that is softer than the inner part 34 and the snap tab 33. The flexible tongue 30 comprises an inner part 34 that comprises a lower part 34a located under the flexible snap tab 33.
FIG. 8b shows an embodiment where the holding groove 32 comprises glue 38 and the flexible tongue 30 is glued into the holding groove. This gives a stronger locking system and cracks C extending primarily between the holding groove 32 and the locking groove 14 may be avoided. The lowest part of the flexible tongue 30 may be located essentially on the same horizontal plane as the lower and outer part 39 of the fold panel 1c. The holding groove may comprise an upper wall and a lower wall and an inner wall extending between the upper and the lower wall. The glue is preferably provided at the upper, the lower and the inner wall. The flexible tongue is preferably glued to the upper, the lower and the inner wall.

## Claims

1. A set of floor panels comprising a first floor panel and a second floor panel which are mechanically connectable to each other at a first edge of the first floor panel and a second edge of the second floor panel, wherein
a protruding tongue is provided in the first edge, said protruding tongue being formed in one piece with the first floor panel and extending outside of an upper part of said first edge,
a separate flexible tongue is arranged in a holding groove provided in the second edge, and
the first edge comprises a strip with a locking element and the second edge comprises a locking groove, the locking element being provided horizontally outside said protruding tongue,
wherein the first and the second floor panel are mechanically connectable by a vertical displacement towards each other to obtain a connected state in which:
a flexible snap tab of the separate flexible tongue cooperates with the protruding tongue for locking the first floor panel and the second floor panel to each other in a vertical direction,
the locking element cooperates with the locking groove for locking the first floor panel and the second floor panel to each other in a horizontal direction,

wherein the flexible snap tab and the protruding tongue are configured to cooperate during said vertical displacement such that
in a first stage at least a part of the flexible snap tab is displaced towards the second edge by the protruding tongue, and
in a second stage at least a part of the flexible snap tab is displaced towards the first edge to obtain the connected state.

2. The set of floor panels according to claim 1, wherein the protruding tongue is formed in one piece with a core of the first floor panel.

3. The set of floor panels according to claim 1, wherein the flexible snap tab extends upwardly when the separate flexible tongue is arranged in the holding groove.

4. The set of floor panels according to claim 1, wherein the flexible snap tab is an outer part of the separate flexible tongue.

5. The set of floor panels according to claim 1, wherein the flexible snap tab cooperates with the protruding tongue from below for locking the first floor panel and the second floor panel vertically.

6. The set of floor panels according to claim 1, wherein the locking groove is open towards a rear side of the second floor panel that faces a subfloor.

7. The set of floor panels according to claim 1, wherein said at least a part of the flexible snap tab is resiliently displaced towards the second edge by the protruding tongue in the first stage.

8. The set of floor panels according to claim 1, wherein said at least a part of the flexible snap tab is in a position displaced towards the second edge by the protruding tongue in the first stage, and said at least a part of the flexible snap tab is in a position displaced towards the first edge in the second stage to obtain the connected state.

9. The set of floor panels according to claim 1, wherein an outer part of the protruding tongue comprises an inclined or rounded guiding surface at an upper and outer part of the protruding tongue.

10. The set of floor panels according to claim 1, wherein the protruding tongue is arranged above the strip.

11. The set of floor panels according to claim 1, wherein the protruding tongue is arranged at a vertical plane and extends outside of said vertical plane, wherein the vertical plane is provided between or intersects an upper edge of said first edge and an upper edge of said second edge in the connected state.

12. The set of floor panels according to claim 1, wherein a space is provided between an upper part of the protruding tongue and the second edge in the connected state.

13. The set of floor panels according to claim 1, wherein a space is provided between an upper part of the strip and the second edge in the connected state.

14. The set of floor panels according to claim 1, wherein the protruding tongue comprises, at a lower part of the protruding tongue, a locking surface which in the connected state is configured to cooperate with the flexible snap tab.

15. The set of floor panels according to claim 14, wherein the locking surface of the lower part of the protruding tongue is inclined.

16. The set of floor panels according to claim 14, wherein the locking surface of the lower part of the protruding tongue is arranged above the strip.

17. The set of floor panels according to claim 1, wherein the protruding tongue and the flexible snap tab are configured such that an initial contact, during said vertical displacement, between the protruding tongue and the flexible snap tab is obtained at an upper part of the flexible snap tab.

18. The set of floor panels according to claim 1, wherein the separate flexible tongue is glued into the holding groove.

19. The set of floor panels according to claim 1, wherein the separate flexible tongue has an inner part connected to holding groove.