The present invention relates to a panels such as a building panels, floorboard, wall panels, ceiling panels, furniture components or the like, which is provided with a mechanical locking system.

Technical background

Building panels provided with a mechanical locking system comprising a displaceable and resilient tongue cooperating with a tongue groove for vertical locking is known and disclosed in, e.g., WO2006/043893, WO2007/015669 and WO2009/066153. The tongue is a separate part and is made of, e.g., plastic and inserted in a displacement groove at an edge of a panel. The tongue is pushed into the displacement groove during an assembling of the panels when the panels are moved vertically with respect to each other, and springs back into the tongue groove of an adjacent panel when the panels have reached a locked position.

Although most of the description relates to floor panel, the description of techniques and problems thereof is applicable also for other applications, such as panels for other purposes, for example wall panels, ceiling panels, furniture, etc.

A drawback with the known locking system is that the tongue may spring back with a lower force than desired.

The above description of various known aspects is the applicant's characterization of such, and is not an admission that any of the above description is considered as prior art.

Summary

It is an object of certain embodiments of the present invention to provide an improvement over the above described techniques and known art.

Particularly, the strength of the known locking system is improved by

embodiments of the invention. A further object of embodiments of the invention is to provide panels with a locking system comprising a displaceable tongue that springs back with a greater force, without making the assembling of the panels more difficult.

At least some of these and other objects and advantages that will be apparent from the description have been achieved by a set of essentially identical panels provided with a mechanical locking system comprising a displaceable tongue, which is arranged in a displacement groove at a first edge of a first panel. The displacement groove is preferably open in a horizontal direction. The displaceable tongue is configured to cooperate with a first tongue groove at a second edge of an adjacent second panel, for locking the first and the second edge in a vertical direction. The displaceable tongue is of a

longitudinal shape and resilient with a spring constant that varies in the longitudinal direction of the displaceable tongue. A middle section in the longitudinal direction of the displaceable tongue has a higher spring constant than a first edge section of the tongue.

The lower spring constant at the first edge section may facilitate

assembling of the first and second panel at the first and the second edges while the higher spring constant at the middle section may provide an improved locking. The higher spring constant may also provide a higher click sound when the displaceable tongue enters into the tongue groove. The higher click sound may be an indication to an assembler of the panels that the panels are properly assembled. The spring constant at the middle section may be in a range of about 1 , 1 to about 5, preferably in the range of about 1 ,5 to about 3, times higher than the spring constant at the first edge section.

The displaceable tongue may function in a similar manner as a spring.

When a spring is compressed, the force it exerts is essentially proportional to its change in length. The rate or spring constant of a spring is the change in the force it exerts, divided by the change in deflection of the spring. An extension or compression spring has units of force divided by distance, for example N/m. The displaceable tongue may be compressed in its width direction.

The displaceable tongue may also be provided or function in a similar manner as a torsion spring that has units of torque divided by angle, such as Nm/rad. The displaceable tongue may alternatively function as a combination of a spring and a torsion spring. Depending on the design and required operating environment, any material may be used to construct a spring, as long as the material has the required combination of rigidity and elasticity.

The spring constant of the middle section may also be higher than a spring constant of a second edge section of the tongue.

The displaceable tongue may be displaced about 0,5 mm to about 3 mm during assembling.

An inner long edge of the tongue may comprise protrusions arranged in the displacement groove, wherein the protrusions are bendable. A first of the protrusions may be arranged at the middle section and a second of the protrusions may be arranged at the first edge section, wherein the bending resistance of the first of the protrusion is greater than the bending resistance of the second protrusion. A third of the protrusions may be arranged at the second edge section, wherein the bending resistance of the first of the protrusion may be greater than the bending resistance of the third protrusion. A thickness of the first protrusion may be greater than a thickness of the second protrusion. A thickness of the first protrusion may be greater than a thickness of the third protrusion.

The displaceable tongue may be provided with a symmetrical outer edge. An upper and a lower side of the outer edge are preferably both provided with a surface and a surface that may function as either a locking surface or a guiding surface. This embodiment may have the advantage that the displaceable tongue may be turned upside-down with the same guiding and locking function. The mechanical locking system may comprise a first locking strip, at the first or the second edge, provided with a first locking element configured to cooperate with a first locking groove at the other of the first or second edge for locking the first and the second edge in a horizontal direction. The panels may be rectangular and the mechanical locking system may comprise a second locking strip, at a third or fourth edge, provided with a second locking element configured to cooperate for horizontal locking with a locking groove at the other of the third of fourth edge of an adjacent third panel. The third or the fourth edge is preferably provided with a second tongue configured to cooperate for vertical locking with a second tongue groove at the other of the third of fourth edge of an adjacent third panel.

The mechanical locking system at the third and the fourth edge may be configured to be assembled by an angling motion.

The mechanical locking system at the first and the second edge may be configured to be assembled by a vertical motion.

The panels may be floorboards, wall panels, ceiling panels, a furniture component, or the like.

The core of the panels may be a wood-based core, preferably made of MDF, HDF, OSB, WPC, plywood or particleboard. The core may also be a polymer-based core comprising thermosetting plastic or thermoplastic, e.g., vinyl or PVC. The plastic core may comprise fillers.

The front face of the panels is preferably provided with a decorative layer and the back face is preferably provided with a balancing layer.

The edge of the panels, of which parts of the locking system, such as the first and the second locking strip, the first and the second locking element, the first and the second locking groove and the first and the second tongue groove, may be made, may comprise the core material.

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 show several embodiments of the present invention.

FIG 1 shows assembling of floorboards provided with a locking system comprising a displaceable tongue.

FIGS 2A-2B show cross sections of embodiments of the locking system.

FIGS 3A-3B show cross sections of embodiments of the locking system.

FIGS 4A-4B show two perpendicular assembled panels provided with

embodiments of the locking system.

FIGS 5A-5F show embodiments of the displaceable tongue.

FIGS 6A-6D show cross sections of embodiments of the locking system. Detailed description

An embodiment of a mechanical locking system for building panels, which comprises a displaceable tongue 30 cooperating with a first tongue groove 20 for vertical locking of a first edge of a first panel 1 with a second edge of a second panel 1 ', is shown in FIG 1 . The displaceable tongue 30 is a separate part and is made of e.g. a polymer material, and is inserted in a displacement groove 40 at the first edge of the first panel 1. The displaceable tongue 30 is pushed into the displacement groove 40 during a vertical assembling of the first and the second edges of the panels, and springs back into the first tongue groove 20 at the second edge of the second panel 1 ' when the panels have reached a locked position. The displaceable tongue 30 is of a longitudinal shape and has a spring constant that varies in the longitudinal direction of the displaceable tongue 30. A third and a fourth edge of the panels are provided with a locking system, which enables assembling to an adjacent panel 1 " by an angling movement, to obtain a simultaneous assembling of the first and the second edges and the third and the fourth edges.

FIGS 2A-2B and 3A-3B show in a locked position cross sections of different embodiments of the mechanical locking system provided at the first and second panels 1 , 1 '. A displaceable tongue 30 is arranged in a displacement groove 40 at the first edge of the first panel 1. The displaceable tongue 30 cooperates with a first tongue groove 20, which is formed at the second edge of the second panel 1 ', for vertical locking of the panels 1 , 1 '. A first locking strip 6 with a vertically protruding first locking element 8 is formed at the first edge of the first panel 1 . The locking element 6 cooperates with a first locking groove 14, formed in the edge of the second panel 1 ', for horizontal locking of the panels 1 , 1 '.

An embodiment of the displaceable tongue 30, which is shown in FIG 3A- 3B, is provided with a recess 31 at an outer tip of the displaceable tongue. The recess 31 makes it possible to have a smaller first tongue groove 20 and an increased distance 50 between the first tongue groove 20 and the locking groove 14. The increased distance may improve the strength of the mechanical locking system. Embodiments of the mechanical locking system may have a

displacement groove 40 that extends in a direction essentially parallel to an upper surface of the panels, as is shown in FIG 2A and FIG 3A. The displacement groove may alternatively extend at an angle to the upper surface of the panels, as is shown in FIG 2B and 3B. The angled displacement groove 40 may have the advantage of the increased distance 50 between the first tongue groove 20 and the locking groove 14.

Embodiments of the mechanical locking system may be used to lock together a first panel 2 and a second panel 4 that are arranged essentially perpendicular to each other. An edge section 22 of the first panel 4 may be arranged in an edge section groove 21 of the second panel 2. FIG 4A shows an embodiment with the displacement groove 40 arranged in the edge section groove 21 and the tongue groove 20 arranged at the edge section 22. FIG 4B shows an embodiment with the displacement groove 40 arranged at the edge section 22 and the tongue groove 20 arranged in the edge section groove 21.

Preferred embodiments of the displaceable tongue 30 comprise

protrusions 24 at a long edge of the displaceable tongue 30. The protrusions 24 are bendable and preferably arranged in the displacement groove 20. The protrusions 24 are configured to bend when the displaceable tongue 30 is pushed into the displacement groove 40 and to spring back to obtain the locked position. The displaceable tongue may be displaced about 0,5 mm to about 3 mm during the assembling. FIGS 5A-5D show embodiments of the displaceable tongue 30 that is provided with a recess 25 at each of the protrusions. Each of the protrusions 24 is configured to be bent into a respective one of the recesses 25. FIG 5B shows a cross section of the displaceable tongue 30 and the displacement groove 20 shown in FIG 5A. The displaceable tongue 30 may comprise an upper and a lower displacement surface 26, 27 that is/are

configured to cooperate with an upper and lower surface 28, 29, respectively, of the displacement groove 20. FIG 5A shows a first protrusion 24 and a second protrusion 24' with different thicknesses. The thickness of the second protrusion 24' is larger than a thickness of the first protrusion 24 in order to obtain a larger spring constant of the second protrusion 24'. In addition, or alternatively, the length of the first protrusion may also be longer than the length of the second protrusion 24' in order to obtain a lower spring constant of the first protrusion 24. The first protrusion 24 is preferably arranged at a first edge section of the displaceable tongue 30 and the second protrusion 24' is preferably arranged at a middle section of the displaceable tongue 30. The spring constant of the first protrusion 24 may be in a range of about 0, 1 N/mm to about 10 N/mm, preferably in the range of about 1 N/mm to about 4N/mm. The spring constant of the second protrusion 24 ^' may be in a range of about 1 ,1 to about 5 times as large as the spring constant of the second protrusion 24, preferably in the range about 1 ,5 to about 3 times. The spring constant of the second protrusion 24 ^' is preferably about two times the spring constant of the first protrusion 24. An advantage with a lower spring constant at an edge section may be that the force required for assembling is initially lower if panels are installed, e.g., as is shown in FIG 1 . An advantage with a high spring constant at the middle section may be that the spring force that forces the panels together is higher and a difference in level at the middle section of the first and the second edge, due to e.g. warped panels, may be levelled out. Differences in level at the edge sections of the first and second edge may be levelled out by the locking system at the third and forth edge.

FIG 5C shows an embodiment of the displaceable tongue 30 comprising protrusions 24 ^' with a first spring constant C1 at the middle section of the displaceable tongue 30 and protrusions 24 at the first and the second edge sections with a second spring constant C2. The first spring C1 constant is larger than the second spring constant C2. The first spring constant may be in a range of about 1 , 1 to about 5 times as large as the second spring constant, preferably in the range about 1 ,5 to about 3 times. The first spring constant is preferably about two times the second spring constant.

FIG 5D shows that the displaceable tongue may comprise protrusions with a spring constant C3 that is between the first and the second spring constant.

FIGS 5E and 5F show that the displaceable tongue 30 may comprise an inner flexible part 38 and an outer stiffer part 39. The spring constant may be varied in the longitudinal direction of the displaceable tongue by having different thickness of the flexible part or by having different material of flexible part. FIG 5E shows a cross section of the displaceable tongue shown in FIG 5D.

FIG 6A-6B show embodiments of the displaceable tongue in a cross section during assembling of a first and a second panel. The embodiments of the displaceable tongue comprise three sections, an inner section 34, an outer section 33 and a middle section 35 connected to each other. The sections comprise preferably a polymer material. The outer and inner sections 33 and 34 are formed from a more rigid material than the middle section 35, which provides the major flexibility to the displaceable tongue 30. The middle section may be of a rubber like material and may also be used as a friction connection in order to prevent the flexible tongue from falling out of the displacement groove 40. The middle section 35 may function as a torsion spring. The outer section 33 preferably protrudes outside a vertical plane VP at the upper adjacent joint edges of the panels 1 , 1 '. The material and/or thickness of parts of the

displaceable tongue may vary in the longitudinal direction of the displaceable tongue 30 to obtain the desired variation of the spring constant in the longitudinal direction of the displaceable tongue 30. The inner section 34 may comprise a fixing edge that may be located at an upper or a lower part.

An embodiment of the displaceable tongue 30 may be of a V-shaped form as is shown in a cross section during assembling of a first and a second panel 1 , 1 ' in FIG 6C. An outer and first leg 61 of the displaceable tongue 30 may protrude outside an edge of the first panel 1 . An inner and second leg 62 of the displaceable tongue 30 may be arranged in a fixation groove 63 at a first edge of the first panel 1 . A second edge of the second panel is provided with a tongue groove 20. The first leg 61 is configured to cooperate with the tongue groove 20 for locking in a vertical direction. The thickness of the first leg 61 may vary in the longitudinal direction of the displaceable tongue 30 to obtain the desired variation of the spring constant in the longitudinal direction of the displaceable tongue 30. The first leg 61 may point downwards when the flexible tongue 30 is provided at an edge of a panel comprising a strip 6 and a locking element 8. The first leg 61 is pushed downward during assembling of the first and second panels 1 , 1 '.

Alternatively, the first leg 61 may point upwards when the flexible tongue 30 is provided at an edge of panel comprising a locking groove.

An embodiment of the displaceable tongue 30 with a symmetric outer edge 64 is shown if FIG 6D. An upper and a lower side of the outer edge are both provided with a surface that may function as either a guiding surface and a locking surface. The guiding surface of the upper side of outer edge 64

cooperates with a guiding surface of the second edge of the second panel 1 ' during assembling of the first and the second panel 1 , 1 '. The locking surface of the upper side of outer edge 64 cooperates with a locking surface of the tongue groove 20 at the second edge of the second panel 1 ' in a locked position of the first and the second panel. The symmetric outer edge 64 may have the advantage that the displaceable tongue 30 has the same guiding and locking function also when the displaceable tongue is turned upside-down. An

embodiment of the displaceable tongue with a first spring constant at the first edge section and a second spring constant and the second edge section may be turned upside down to change the position in the displacement groove of the first and the second edge section. The displaceable tongue is preferably positioned such that the edge section with lowest spring constant is the edge section with the earliest cooperation with the guiding surface of the second edge of the second panel V during assembling of the first and the second panel 1 , 1 '.

Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.