Patent Application
20190161975
The invention generally relates to a synthetic (also called polymer-based or polymeric) floor covering composed of individual floor panels (in the form of tiles, planks, strips or the like), which are laid out, side by side, on the underfloor (the floor to be covered). The floor covering according to the invention may be installed as a floating floor covering (without direct attachment to the subfloor) or as a glued floor covering.
Synthetic surface coverings are well known. Generally they are made of rubber, polyolefins, polyesters, polyamides or PVC. They present specific mechanical properties, particularly in terms of mechanical resistance, wear and indentation resistance, but also in terms of comfort, softness, sound and heat insulation.
In the context of the present document, laminate floor coverings with a fibreboard core are not considered synthetic floor coverings.
Among polymer-based surface coverings, two main categories can be identified. Homogenous surface coverings are coverings comprising agglomerated particles, generally obtained by cutting or shredding a sheet made from a composition which comprises a polymer-based material, and wherein no bottom layer, or backing, conferring structural stability to the surface covering, is used. Heterogeneous or multilayer surface coverings are coverings comprising one or more lower layers and one or more transparent upper layers (wear layer and, possibly, a hard top varnish). These coverings may comprise a decorative pattern imitating the aesthetic appearance of natural floorings such as wood or stone floorings. Such decorative pattern may be printed on the bottom face of the wear layer, on the top face of a core or support layer or on an additional layer (print layer) that is inserted between the core or support layer and the wear layer.
Floor covering elements (hereinafter: floor panels) with conjugate connection profiles are known in the art. One of their simplest embodiments comprises a tongue profile (or male profile) and a groove profile (or female profile). Each floor panel has one or two edges (lateral faces) with a tongue profile and the opposite one or two edges are provided with respectively complementary groove profiles. While such profiles have first been used on wood floor panels, they have meanwhile also been applied to laminate floor panels. For instance, WO 97/47834 discloses a floor covering, consisting of hard floor panels (i.e. laminate panels with a fibreboard base or wood panels) which, at least at the edges of two opposite sides, are provided with coupling parts, cooperating with each other, substantially in the form of a tongue and a groove. The coupling parts, which are integrated into the floor panels, mechanically interlocking in order to prevent two coupled floor panels from drifting apart into a direction perpendicular to the adjacent edges and parallel to the underside of the coupled floor panels. In the engaged state of two floor panels, the coupling parts are slightly elastically deformed in such a way that they exert on each other a tension force that urges the floor panels toward each other.
A first aspect of the invention relates to a synthetic multilayer floor covering, comprising floor panels, each of which comprises at least a first and a second edge with a first and a second connecting profile, respectively. The first and second connecting profiles are complementarily shaped in such a way that adjacent floor panels may be coupled to one another via the first and second connecting profiles. The shapes of the first and second connecting profiles are such that at least one of the first connecting profile of a first floor panel and the second connecting profile of a second floor panel is deformed when the first and second connecting profiles become coupled with each other. The deformation comprises a component that persists (i.e. at least part of the deformation persists) as the first and second connecting profiles remain coupled, the persistent component resulting in stress within the first and/or the second connecting profile. An advantageous feature is that the first and/or the second connecting profiles are made of viscoelastic material, which undergoes significant stress relaxation. Specifically, at standard ambient temperature and pressure, the stress within the first and/or the second connecting profile decreases by at least 40% within 12 hours after the first and the second connecting profiles have become coupled.
As used herein, the conditions of “standard ambient temperature and pressure” mean room temperature (i.e. 25 C) and normal atmospheric pressure (i.e. 1013.25 hPa). The reduction of stress is indicated relative to the value which is reached immediately (at most 5 s) after two previously unused connecting profiles are connected to each other. It is worthwhile noting that due to the viscoelastic properties of the material(s) of the connecting profiles, the deformation persists permanently or for a long time after two connecting profiles have been separated and that, hence, the same stress relaxation will not be measured on connecting profiles that have been in use before. From this consideration, it is also apparent that there are at least two factors that have an impact on stress relaxation, in particular the initial strain (which depends on the geometry of the first and second connecting profiles) and the type of viscoelastic material used.
Unlike in hard floor panels (such as fiberboard laminate or wood panels), the restore forces that the coupled connecting profiles exert upon each other (due to their elasticity) fade away very quickly. Contrary to what one would have readily expected, that phenomenon has no serious detrimental effects on the durability of the floor covering. In particular, it was not observed that the floor panels of a floating floor covering became loose over time. One may speculate that friction forces take over the role of the tension but there may be other theoretical explanations, which, accordingly, shall not limit the present invention.
Further to the surprisingly good coherence of the floor covering, it was discovered that mechanical strain distributes more easily and more evenly over larger areas (i.e. over several neighboring floor panels), thereby reducing mechanical stress within the individual floor panels. Strong tension between engaged connecting profiles may prevent small movements (in the sub-millimeter range) of the individual panels relative to each other, leading to a local build-up of stress (e.g. as a consequence of temperature and/or humidity variations). The effect may be more pronounced in some areas than in others e.g. due to production tolerances of the connecting profiles. Indeed, small variations in the dimensions of the connecting profiles may lead to important variations in the tensions between adjacent panels a in their ability to dissipate stress, in particular shearing stress in the directions of the edges. One may consider interlocking flooring systems as a small-scale system of tectonic plates. In severe cases, the build-up of stress may lead to noticeable strain of the floor covering (e.g. in the form of bulging) and/or to sudden (but still small) lateral displacements of the floor panels. Such extreme phenomena were not observed on floor coverings according to the first aspect of the invention. With floor coverings according to the first aspect of the invention, no significant build-up of mechanical stress was observed.
Preferably, the mechanical stress within the first and/or the second connecting profile decreases more and/or more quickly. According to a preferred embodiment, at standard ambient temperature and pressure, the stress within the first and/or the second connecting profile decreases by at least 50%, preferably by at least 60% and more preferably by at least 70%, within 12 hours after the first and the second connecting profiles have become coupled. Additionally or alternatively, at standard ambient temperature and pressure, the stress within the first and/or the second connecting profile may decrease by at least 40% within 6 hours, preferably within 2 hours and more preferably within 1 hour, after the first and the second connecting profiles have become coupled. According to a particularly preferred embodiment of the invention, at standard ambient temperature and pressure, the stress within the first and/or the second connecting profile decreases by at least 60% within 1 hour after the first and the second connecting profiles have become coupled. Preferably also, the mechanical stress within the first and/or the second connecting profile decreases to tend towards an asymptotic value at least 70% lower than the initial value.
Preferably, the floor panels comprise a backing substrate, one or more core layers, a decorative print layer on top of the core layers and at least one transparent wear layer on top of the print layer. The core layer is preferably polymer-based (preferably PVC-based and/or thermoplastic) core layer laminated between the backing layer(s) and the wear layer(s). The core layer may comprise a material having a lesser shore hardness than the materials of the backing layer(s) and the wear layer(s). The core layer may itself be composed of one or more layers (hereinafter termed “core sub-layers”). The core sub-layers are preferably consisting of thermoplastic material and/or PVC-based. Preferably, the core layer has a coefficient of dynamic friction comprised in the range from 0.50 to 0.65, more preferably in the range from 0.55 to 0.60, when determined according to European Standard EN 13893.
The floor panels are flexible floor panels. As used herein, the term “flexible” designates a floor panel that can be bent to a radius of curvature of 75 cm, preferably to a radius of curvature of 50 cm, or even to a smaller radius of curvature (e.g. 25 cm or less), without visible deterioration. It will be understood, however, that a synthetic floor panel used in the context of this invention is not totally soft (such as a carpet with a foam backing) but has a firmness or rigidity that makes the floor panel suitable for the secure installation of a floating floor covering by interconnecting the floor panels via their connection profiles.
The synthetic multilayer floor covering (and, hence, each floor panel) preferably has a thickness in the range from 3 mm to 8 mm, more preferably in the range from 3 to 5 mm.
The floor panels may, e.g., be vinyl floor tiles and/or planks, preferably vinyl composition tiles, solid vinyl tiles or luxury vinyl tiles. The floor panels may be PVC-based or PVC-free. Such vinyl floor panels may comprise a urethane wear layer.
The synthetic multilayer floor covering has a decorative top face, which comprises a decorative pattern. The decorative pattern may be of any type, e.g. of the type imitating natural flooring such as wood flooring, bamboo flooring, stone flooring, ceramic flooring or cork flooring. Any other decorative pattern, e.g. a photograph, a drawing or an abstract design, could of course also be used on the top face.
The floor tiles are preferably arranged in rows. The floor tiles of the different rows may be arranged in a staggered manner or be aligned perpendicular to the rows.
Preferably, the first and second connecting profiles are integral with the floor panels. The first and second connecting profiles may e.g. be machined into the first and second edges, respectively. As used herein, “machining” implies the removal of matter (e.g. by cutting away, abrading or the like) from the edges of a blank floor panel using one or more machines.
A second aspect of the invention relates to a rectangular synthetic multilayer floor panel for laying a floor covering. The floor panel according to the second aspect of the invention has a decorative top face and a bottom face for contacting an underfloor, and further:
The shapes of the first and second connecting profiles are such that at least one of the first connecting profile of a first floor panel and the second connecting profile of a second floor panel is deformed when the first and second connecting profiles become coupled with each other, the deformation comprising a component persistent as the first and second connecting profiles remain coupled, the persistent component resulting in stress within the first and/or the second connecting profile. The first and/or the second connecting profiles are made of viscoelastic material such that, at standard ambient temperature and pressure, the stress within the first and/or the second connecting profile decreases by at least 40% within 12 hours after the first and the second connecting profiles have become coupled.
The terms “long” and “short” are used herein to distinguish between the longer and the shorter edges of a rectangular floor panel; they do not imply any particular dimensions in absolute figures.
Preferably, the shapes of the first and second connecting profiles is such that the deformation undergone by the first and/or the second connecting profile during the coupling process also comprises a transient component (i.e. a part of the deformation is only temporary and can be observed only during the coupling process.)
Preferably, the first and second connecting profiles define so-called angling-type connectors. Connecting profiles of this type require the tongue of the first connecting profile (on the panel to be installed) to be angled into the groove of the second connecting profile (of a panel already laid on the floor) whereupon the newly added floor panel is hinged down to the floor. During this movement, the connection profiles deform resiliently and then “snap” into place. The tongue thus becomes locked in the groove such that a separation thereof requires a higher amount of force or a specific relative movement of the profiles. When angling-type connectors are provided on the four edges of each floor panel, the new floor panel to be laid is first angled into the element on the left already in place. Then, the new panel is declined towards the rear and angled into the row behind (as seen from the person who install the floor covering). The latter step requires that the panel(s) on the left follow the movement of the new panel. They are thus also raised at their front and hinged down. Installing such “double-angling-type” floor panels requires some coordination, which is however easily acquired through some practice.
According to a possible embodiment of a floor panel according to the second aspect of the invention, when looking at the floor panel from above the top face, the edges are arranged in the following order in the clockwise direction: 1) the first long edge, 2) the second short edge, 3) the second long edge and 4) the first short edge (hereinafter: the first edge arrangement order). All references to clocks used herein are references to “normal” clocks, i.e. the clockwise sense of rotation is the one indicated by the fingers of a loosely clenched left hand with the thumb pointing towards the observer.
According to a more preferred embodiment of a floor panel according to the second aspect of the invention, when looking at the floor panel from above the top face, the edges are arranged in the following order in the clockwise direction: 1) the first long edge, 2) the first short edge, 3) the second long edge and 4) the second short edge (hereinafter: the second edge arrangement order). It was discovered that the second edge arrangement order greatly facilitates the installation of flexible rectangular floor panels of the double-angling type. Indeed, with flexible floor panels having the mirrored, i.e. the first, edge arrangement order, the installation of a new floor panel on the right of an already installed floor panel frequently led to a partial loosening of the row being installed from the row behind. That risk could be considerably reduced with floor panels having the second edge arrangement order. When investigating the reasons for the unexpected increase in terms of laying comfort, it was found that the protrusion on the bottom side of the second short edge provided better support for the floor panel on the left of the element being installed, whereby the second angling step became much easier.
Preferably, at standard ambient temperature and pressure, the stress within the first and/or the second connecting profile decreases by at least 50%, preferably by at least 60% and more preferably by at least 70%, within 12 hours after the first and the second connecting profiles have become coupled. Additionally or alternatively, at standard ambient temperature and pressure, the stress within the first and/or the second connecting profile decreases by at least 40% within 6 hours, preferably within 2 hours and more preferably within 1 hour, after the first and the second connecting profiles have become coupled.
By way of example, a preferred, non-limiting embodiment of the invention will now be described in detail with reference to the accompanying drawings, in which:
In the illustrated embodiment, the structure of the floor panels 12 is as follows. The top face 14 of the floor panels 12 is provided by a transparent wear layer 22, whereas the bottom face 16 is provided by a backing layer 32. The backing layer 32 and the wear layer 22 sandwich a viscoelastic core layer 34. A print layer (not shown) is arranged between the core layer 34 and the wear layer 22. Optionally, one or more barrier layers are provided between the layers so far mentioned in order to reduce migration of chemical compounds (e.g. plasticizers) between the layers. All layers are laminated together to form a multi-layered compound. The PVC-based core layer 34 is softer (i.e. it has a lesser shore hardness) than the backing layer 32 and the wear layer 22 so as to give the floor panel the desired resilience and flexibility. The backing layer 32 and the wear layer 22 balance each other so as to substantially avoid curling of the floor panel 12. Although not shown, the core layer 34 may consist of several sub-layers For instance, the core layer 34 may comprise a fiberglass mat positioned in the mechanically neutral plane of the floor panel 12, which is at least approximately at mid-height of the core layer 34. The fiberglass mat preferably extends into the tongue 26 of the male profile M and/or into the extremity 36 of the substantially L-shaped protrusion 28 of the female profile F. Such a fiberglass mat enhances dimensional stability and strength of the core layer 34. The thickness of such fiberglass mat is preferably comprised in the range from 0.07 to 0.12 mm. Preferably, the fiberglass mat (if any) is coarsely meshed, such that the material of the core layer 34 forms one continuous phase penetrating across the openings and interstices of the fiberglass mat and firmly retaining the latter.
The thickness (or height) of the core layer 34 (including all of its sublayers) preferably amounts to between 0.8 mm and 5.5 mm. The backing layer 32 preferably has a thickness amounting to between 0.4 mm and 1.8 mm. The wear layer 22 preferably has a thickness between 0.2 mm and 1.5 mm. The thickness of the print layer preferably amounts to between 0.05 mm and 0.2 mm. The thicknesses of the different layers are preferably chosen such that the floor panel 12 has a total height of 8 mm or less, e.g. 7 mm, 6 mm, 5 mm, 4 mm, 3.5 mm or 3 mm.
The shapes of the male and female connecting profiles M, F are conjugate to each other meaning that they can be brought into engagement. It should be noted, however, that the contour lines of the male and female profiles are not completely identical in cross section. The male and female profiles can be brought into interlocking engagement. When the tongue 26 of the male profile M is inserted into the groove 30 of the female profile F, a temporary deformation of one or both of the profiles is necessary for the tongue 26 to reach its final position in the groove 30.
As shown in
The samples were pressed with the straight edge against an abutment using an electronic tension meter which recorded the force that was necessary to maintain 1% compressive strain (i.e. the force that was necessary to reduce the distance between the abutment and the point of application of the force by 1% of the initial distance). The force measured 1 s after the desired strain was reached was taken as the initial value. The necessary forces decrease in time and are expressed as a percentage of the initial value (which is 100%). After 16 hours, the residual stress measured in viscoelastic PVC (curve 46) was below 20%, whereas the residual stress in wood (curve 48) and HDF (curve 50) amounted to 86% and 61%, respectively. It is also remarkable that within the first hour of the test, the stress in viscoelastic PVC decreased by about 65%. It may be worthwhile noting that, in absolute figures, the initial stress values may be significantly different. In the test, initial stress in the wood sample amounted to 12.8 N/mm2, in the laminate sample to 11.8 N/mm2 and in the viscoelastic PVC sample to 4.3 N/mm2.
Turning back to
The advantage of that arrangement of the connection profiles can be experienced when laying the floor covering. A floor is typically laid by first laying the rearmost row of floor panels from the left to the right and then installing the next row just in front of it. Except for the first row and the leftmost floor panel in each row, a new floor panel is always added in front and to the right of the panels already in place.
The male and female connectors shown in
It is worthwhile noting that floor panels with the first edge arrangement order present the same advantage when the rows of panels are laid from right to left.
Accordingly, such panels may be regarded as especially well-suited for left-handed persons, who may prefer to install flooring that way.
An exemplary embodiment of a synthetic multilayer floor covering has the following structure and composition. From bottom to top the structure comprises a 0.5 mm thick backing layer, a 3.5 mm thick PVC-based viscoelastic core layer, a 0.1 mm thick print layer and a 0.7 mm thick wear layer. The composition of the different layers is indicated hereinafter.
The composition of the core layer is the following:
The wear layer has the following composition:
The printed layer has the following composition:
The backing layer has the following composition:
The layers are made in respective calendaring processes starting from dry blends. For each layer, a dry blend is made with all the ingredients. The dry blend (powders) is compound into a twin screw extruder or an internal mixer. The internal temperature out of the compounder is in the range of 160-190° C. The hot compound is feeding a 4-cylinders calender at a temperature between 130 and 195° C.
While specific embodiments have been described herein in detail, those skilled in the art will appreciate that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.
