Patent Publication Number: US-9428919-B2

Title: Mechanical locking system for floor panels

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 13/577,042, filed on Sep. 27, 2012, which is a U.S. National Stage of International Application No. PCT/SE2011/050116, filed on Feb. 3, 2011, which claims the benefit of Swedish Application No. 1050111-2, filed on Feb. 4, 2010. The entire contents of each of U.S. application Ser. No. 13/577,042, International Application No. PCT/SE2011/050116, and Swedish Application No. 1050111-2 are hereby incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments of the invention generally relate to the field of mechanical locking systems for floor panels and building panels especially floor panels with mechanical locking systems, which are possible to lock with a vertical folding. 
     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, solid powder based surfaces, decorative plastic material and similar surfaces, 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 technology, problems of known systems and objects and features of the invention will therefore, as a nonrestrictive example, be aimed above all at this field of application and in particular at floating flooring formed as rectangular floor panels with long and shorts sides intended 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 can be squared and can have more than four sides, which are not parallel or perpendicular to each other. 
     It should be emphasized that the invention can be applied to any floor panel and it could be combined with all types of known locking system, where the floor panels are intended to be joined using a mechanical locking system connecting the panels in the horizontal and/or vertical directions on at least two adjacent sides. The invention can thus also be applicable to, for instance, solid wooden floors, parquet floors with a core of wood or wood fibre based material and a surface of wood or wood veneer and the like, floors with a printed and preferably also varnished surface, floors with a surface layer of plastic or cork, linoleum, rubber or similar and with core material that do not comprise wood material for example plastic or mineral fibres and similar. Even floors with hard surfaces such as stone, ceramics and similar are included and floorings with soft wear layer, for instance needle felt glued to a board. The invention can also be used for joining building panels which preferably contain a board material for instance wall panels, ceilings, furniture components and similar. 
     BACKGROUND OF THE INVENTION 
     Laminate flooring usually comprises a core of 6-12 mm fibreboard; a 0.1-0.8 mm thick upper decorative surface layer of laminate and a 0.1-0.6 mm thick lower balancing layer of laminate, plastic, paper or like material. A laminate surface may comprise a melamine impregnated paper. Recently printed surfaces and wood fibre based paper free laminate surfaces have been developed. The most common core material is fibreboard with high density and good stability usually called HDF—High Density Fibreboard. Sometimes also MDF—Medium Density Fibreboard—is used as core. 
     Floating laminate and wood 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. The mechanical locking systems are usually formed by machining the core of the panel. Alternatively, parts of the locking system can be formed of separate materials, which are integrated with the floor panel, i.e. joined with the floor panel in connection with the manufacture thereof. 
     The main advantages of floating floors with mechanical locking systems are that they are easy to install. They can also easily be taken up again and used once more at a different location. Although many improvements of production cost and function have been accomplished over the years, there is still a need for further improvements. 
     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 “groove panel” is meant a panel with a locking groove intended to cooperate with a locking element for horizontal locking. 
     KNOWN TECHNOLOGY AND PROBLEMS THEREOF 
     The description of the known technology 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 could 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 and locked by angling. The panel is then displaced, while in the 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 can be joined with just an angling of the long edges. This installation method generally referred to as vertical folding, is described in  FIGS. 1 a   - 4   b.    
     A new panel  1   c  is locked to a previously installed first panel  1   a  with angling. This angling action connects automatically one short edge of the new panel  1   c  with an adjacent short edge of a second panel  1   b , which is installed and locked to the first panel  1   a . The vertical and horizontal locking of the short edges of the panels  1   b ,  1   c  takes place with a vertical turning scissors like motion where a flexible tongue  30  is displaced inwardly gradually from one edge to the other edge when a long side of a new panel  1   c  is connected by angling to a long edge of a first panel  1   a  previously installed in an adjacent row. The flexible tongue, which in most cases is made of a plastic section, snaps and locks automatically during folding of the new panel  1   c  when it is angled down to the subfloor. The displaceable tongue is displaced twice, first inwardly into a displacement groove  32  and then outwardly into a tongue grove  31 . The flexibility is caused by a horizontal bending of the tongue along the joint. A part of the flexible tongue is during folding pressed to its inner position, as shown in  FIGS. 2 a  and 2 b    and other parts are in a completely unlocked position. The flexible tongue snaps into a final locked position when both edges of the panels  1   b ,  1   c  are in the same plane as shown by  FIGS. 3 a  and 3 b    and locks vertically. A strip  6  with a locking element  8  cooperates with a locking groove  14  and locks the panels horizontally. 
     The flexible tongue is generally connected to an edge of the strip panel  1   b . It could also be connected to the groove panel  1   c . One of the most used tongues on the market is a bristle tongue  30 , as shown in  FIGS. 4 a  and 4 b   , that has an inner part comprising several flexible protrusions  10  and an outer rigid part  30 ′. 
     The main problems with known flexible tongues are that the tongue must be made of materials that are rather flexible, that the snapping creates a resistance during folding and that the major part the tongue must be displaced in a groove during locking. 
     The function of a fold down locking system of the kind described above could be improved if locking could be made without a two-ways snapping action described above and with only limited displacement and material bending. It would be an advantage if the tongue could be connected into a groove in a rather fixed manner. 
     There are known systems that could be locked with vertical turning combined with twisting as shown in for example WO 2008/004960, FIG. 6 (Välinge Innovation AB). There are several disadvantages related to such locking systems. The tongue is difficult to connect into a groove since the whole tongue must turning vertically during locking. A major part of the tongue is exposed towards an open groove. This makes the whole locking system very sensitive to cutting of the panel across the joint and the tongue could easily be damaged or fall out from the groove. The tongue could also turn during transportation and material handling. A considerable amount of material must be removed in order to form cavities or groove that could house such turn snap systems. This affects the stability of the edge in a negative way. 
     SUMMARY OF THE INVENTION 
     A basic objective of embodiments of the present invention is to provide an improved mechanical locking system comprising a tongue that locks automatically during folding without any snapping parts that are displaced inwardly and outwardly during locking. 
     A first specific objective of embodiments is to create a non-snapping tongue with a simple cross section that could be connected in a horizontally extending fixation groove with limited depth, which surrounds and protects a major part of the tongue. 
     A second specific objective of embodiments is to create a tongue where the main part of the tongue could be fixed firmly into a groove and were only parts of the tongue are displaced inside and/or outside the fixation groove. 
     The above objects of embodiments of the invention are achieved wholly or partly by a mechanical locking systems and floor panels, according to the independent claim. Embodiments of the invention are evident from the dependent claims and from the description and drawings. 
     According to a first aspect of the invention, a set of floor panels are provided which are mechanically connectable to each other along one pair of adjacent edges by a vertical turning motion, so that upper joint edges of said floor panels in the connected state define a vertical plane. Each of said floor panels comprising a tongue on a first edge of a panel having a length direction extending parallel with the first edge and a tongue groove on a second opposite edge of the panel for receiving the tongue of an adjacent panel for mechanically locking together said adjacent edges in a vertical direction. The tongue has an inner part mounted in a sideward open fixation groove in the first edge and an outer part extending beyond the vertical plane. The inner part is fixed in the sideward open fixation groove. The tongue comprises one or several rocker arms extending in the length direction of the tongue. Each rocker arm comprises a displaceable pressing protrusion that during locking is in contact with the second edge and a displaceable locking protrusion that in locked position cooperates with the tongue groove. The locking protrusions is displaced outwardly away from the main tongue body when the pressing protrusion is pressed and displaced inwardly towards the inner part of the tongue. 
     Said floor panels may further comprise a locking element formed in one piece with the panel at the first edge and a locking groove at the opposite second edge. The locking groove is open towards a rear side of the panel that faces a subfloor. The locking element and the locking groove form a horizontal mechanical connection perpendicularly to the vertical plane. The tongue preferably comprises resilient parts, formed of a separate material than the core. The panels may be mechanically joined together with vertical folding by displacement of said two panels towards each other with a combined vertical and turning motion. The pressing and the locking protrusion of each rocker arm are preferably positioned at different vertical and horizontal positions. 
     According to a second aspect of the invention a tongue is provided comprising a main tongue body having an elongated shape and a length direction. The tongue is intended to be connected into a groove formed in a building panel wherein the tongue comprises one or several rocker arms located along its length and extending in the length direction of the tongue. One part of the rocker arm is displaced outwardly away from the main tongue body when the another part of the rocker arm is pressed and displaced inwardly towards the main tongue body. 
     The above described locking system and the tongue allows that panels could be locked automatically during vertical folding or vertical displacement without any snapping parts that are active and that create snapping resistance. A strong locking could be obtained with a tongue that has limited flexibility and that is fixed into the fixing groove during production, transport and installation. Only a rather limited horizontal turning of the rocker arms is required to lock the panels vertically. 
     The embodiments and principles related to vertical locking could also be used to connect building panels with a horizontal displacement. 
     The tongue is preferably factory connected but it could of course be delivered separately in blanks or as a separate loose component and inserted into a groove during installation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 a -4 b    illustrate known art. 
         FIGS. 5 a -5 f    illustrate embodiments of the invention. 
         FIGS. 6 a -6 i    illustrate vertical folding with rotating tongue parts. 
         FIGS. 7 a -7 e    illustrate a tongue blank and a second embodiment with an inclined displacement groove. 
         FIG. 7 f    illustrates a locking system that locks the edges with a horizontal motion. 
     
    
    
     DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     To facilitate understanding, several locking systems in the figures are shown schematically. It should be emphasized that improved or different functions can be achieved using combinations of the preferred embodiments. 
       FIGS. 5 a -5 f    show a tongue  30  according to an embodiment of the invention.  FIGS. 5 a , 5 b  and 5 e    show a tongue  30 , which is inserted into a fixation groove  32  of a panel  1   b , comprises an inner part IP with a main tongue body  29  and a rocker arm  20  which is connected with a fastening device  21  to the main tongue body  29 . 
       FIG. 5 c    shows that the rocker arm comprises a pressing protrusion  22  located on a pressing arm  26  and a locking protrusion  23  located on a locking arm  27 . The rocker arm is designed such that the locking protrusion  23  is displaced outwardly away from the main tongue body  29  when the pressing protrusion  22  is pressed and displaced inwardly towards the main tongue body  29 . The rocker arm is preferably designed such that it could turn horizontally about 3-10 degrees during locking. The turning is facilitated by a cavity  51 , which is formed between the main tongue body  29  and the pressing arm  26  allowing the pressing arm to be turned and displaced inwardly towards the main tongue body. A cavity  52  is preferably also formed between the locking arm  27  and the main tongue body  29   
     Several rocker arms are preferably located along the length direction L of the tongue as shown in  FIGS. 5 b  and 5 d   . The rocker arms could have different shapes and lengths and some could be mirror shaped and oriented in different directions along the tongue. It is preferred that the rocker arms have a length, which exceeds the depth of the fixation groove  32 . 
     The tongue is preferably connected to the fixation groove  32  with friction connections  28 . Several tongues could be connected into a groove along the edge but also over and under each other. The friction connections  28  could be designed such that the tongue is connected in a rather loose way or in a rather fixed way with firm friction. Even glue or snapping connections, where the core material is bended or compressed, could be used to fix the tongue into the fixation groove  32 . The friction  28  connections could be located on protruding parts that could flex vertically in order to eliminate production tolerances. 
       FIGS. 6 a -6 i    show vertical folding and a connection of two adjacent edges of the panels  1   b ,  1   c  with a combined vertical and turning motion. The tongue is preferably connected to the strip panel  1   b  comprising a strip  6  with a locking element  8  that cooperates with a locking groove  14  in an adjacent panel edge for horizontal locking of the edges. The tongue could also be connected to the groove panel comprising the locking groove  14  and a tongue groove  31 .  FIGS. 6 d  and 6 g    show two cross sections A-A and B-B of two adjacent edges of the panels  1   b  and  1   c  in an unlocked position. A-A is a cut at the locking protrusion  23  and B-B is a cut at pressing protrusion  22  that is also shown in  FIGS. 6 b  and 6 c   . The locking protrusion  23  is in its inner position and the pressing protrusion  22  is in its outer position and protrudes beyond the vertical plane VP. The groove panel  1   c  comprises preferably a lower sliding surface  41 , preferably formed as a bevel, that cooperates with a preferably inclined or rounded upper surface  42  of the pressing protrusion  22 . 
       FIGS. 6 e  and 6 h    show that the pressing protrusion  22  is pressed inwardly by a lower part of the grove panel  1   c , preferably the lower sliding surface  41  and causes a turning motion of the rocker arm  20 , as shown in  FIGS. 6 b  and 6 c   , such that the locking protrusion  23  is displaced outwardly towards a tongue groove  31  formed in the adjacent edge. The turning is mainly accomplished with a bending of the resilient fastening device  21 . 
       FIGS. 6 f  and 6 i    show cross sections of the edges in the locked position when the locking protrusion  23  is in contact with the tongue groove  31  and locks the edges in a vertical direction parallel to the vertical plane VP. The pressing protrusion  22  is locked horizontally against a locking edge  45  of the groove panel  1   c . The outer part  46  of the pressing protrusion  22  is preferably located below the outer part  47  of the locking protrusion  23 . 
     The locking could be accomplished essentially with only a turning motion in essentially a horizontal plane. The pressing and locking protrusions are preferably turning in essentially the same plane. Such turning is facilitated if the tongue groove  31  and the locking protrusion  23  preferably have contact surfaces  43 ,  44  that are inclined in relation to the horizontal plane. Such inclination is preferably 10-50 degrees. It is an advantage if the tongue groove locking surface  44  is more inclined than the locking surface  43  of the locking protrusion  23 . 
     The locking could also be combined with bending of the pressing and locking arms. The locking system could also be designed such that the locking protrusion creates a pressure against the adjacent edge during locking whereby the rocker arm is slightly bended during locking and/or in locked position. This pressure is released partly or completely when the tongue groove  31  is in a position that allows the outer part  47  of the locking protrusion to enter into the tongue groove  31 . 
     It is preferred that the final locking is made with horizontal pre tension between the locking protrusion and the tongue groove. Such pre tension is used to overcome production tolerances and to press the adjacent edges of the panels  1   b ,  1   c  vertically towards each other in order to preferably accomplish a tight vertical fit between the strip  6  and the adjacent joint part  53  of the groove panel  1   c.    
     The configuration of the rocking arms could be adapted to the contact angles of the adjacent edges during folding.  FIG. 6 a    shows that a pressing against a pressing protrusion located close to the long side edge of the panel  1   b ′ and at a distance from the other pressing protrusions starts at a higher angel than the pressing against a pressing protrusion located close to the opposite free long side edge of the panel  1   b″.    
     Long and short edges are used to simplify the description. The panels could be square. 
       FIGS. 7 a , 7 b    show a tongue and a tongue blank  50  comprising several tongues. Very advanced tongue shapes could be formed with injection moulded plastic components and each rocker arm could have an individual design. The cross section of a pressing and/or locking protrusion may vary between the rocking arms located along the tongue. 
     It is an advantage if the rocker arms are compacts and located close to each other such that a lot of locking protrusions are active during locking. In small and thick panels only one rocker arm could be sufficient. In most applications several rocker arms should be used. The distance D between the fastening devices  21  should preferably not exceed four times the floor thickness T. Very compact tongues could be made where the distance D between the fastening devices  21  is only about 2 times the floor thickness. This means that a locking system in a 7-10 mm laminate flooring could comprise several locking protrusion with a distance of about 2 cm and this gives a very strong vertical locking. 
     The distance between the fastening devices  21  along the tongue is preferably larger than the distance between the pressing and locking protrusions  22 ,  23 . 
     It is an advantage if the locking protrusion  23  is very compact as shown in  FIG. 7 c   . The length of the pressing protrusion along the edge is preferably smaller than the floor thickness. 
       FIGS. 7 d  and 7 e    show that it could be an advantage if the fixation groove  32  is inclined against the horizontal plane HP. This facilitates the insertion of the tongue into the fixation groove and the turning of the pressing extension could be made with a lower pressing force. This embodiment comprises a locking element  8  and a locking groove  14  that have inclined cooperating locking surfaces. Such an embodiment could also be locked and unlocked with angling. 
     The principles described above could be used to provide locking systems that snaps in the same way as the known systems. The pressing and/or locking protrusion could be formed such that they are displaced inwardly and outwardly during locking such that they snap into a tongue groove. 
       FIG. 7 f    shows that all principles and embodiment described above could be used to lock floor panels horizontally with a horizontal displacement against each other. The tongue  30  is located in a vertically extending fixation groove  32 ′ which could be formed in the groove panel  1 ′ with its opening towards the rear side or on the strip panel  1  with its opening towards the front side. A tongue  10  and groove  9  could be used to lock the panels vertically. The rocker arms will in this embodiment turn or snap in a vertical plane. The fixation groove could be inclined and several rounded or beveled sliding surfaces could be used to facilitate the vertical rotation or snapping of the rocker arms. 
     All known materials that are described and used in fold down systems of the kind described in  FIGS. 1 a -4 b    could be used to form tongues according to the invention. The rocker tongues could be adapted to fit into a displacement groove of the known bristle tongues and the same inserting equipment could be used. 
     The rocker arms could of course be formed with one or two legs and in a way that they could be bended inwardly and outwardly during locking. Such a tongue could be used to connect floor panels with snapping actions where the rocker arms are displace inwardly and are snapping outwardly during locking.