Abstract:
A floating floor assembled from an array of interconnected subunits, each of which includes a stone, ceramic or porcelain tile and a one-piece polymeric plastic substrate to which the stone, ceramic, or porcelain tile is bonded. Each substrate is injection molded from certain polyolefin polymers and incorporates the interlock structure and certain other features of the modular sports tiles of U.S. Pat. No. 4,930,286. The substrates of the present invention, however, differ in that the plastic support grid is formed by three sets of mutually intersecting walls, with each set being angularly offset from the other two by 120 degrees, and each substrate is sized to precisely fit a stone, ceramic or porcelain tile, which is accurately positioned by tile locator tabs on a pair of intersecting sides of the substrate.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to floating floors, tile floors and, more particularly, to floating floors assembled from an array of interconnected subunits, each of which includes a ceramic or stone tile bonded to an injection molded plastic substrate, as well as to a method for manufacturing such subunits. 
         [0003]    2. Description of the Prior Art 
         [0004]    Several attempts have been made in recent years to create floating floors using ceramic tile as the wearing surface. The applicant is aware that, for a short time, Costco Wholesale Corporation sold boxes of ceramic tile flooring which interlocked to form a floating tile floor. However, after consumers experienced severe problems related to tile delamination, poor interlocking performance, dirt build-up between adjoined pieces of tile units, and inability to accommodate significant thermal expansion, Costco recalled the product and wrote off as a loss a large inventory of product. 
         [0005]    Probably the most successful floating tile floor system developed to date is covered by U.S. Pat. No. 4,930,286 (hereinafter the &#39;286 patent), which is titled MODULAR SPORTS TILE WITH LATERAL ABSORPTION. This patent, in its entirety, is incorporated in this patent application by reference. Developed by Daniel Kotler as a continuous flat athletic floor covering, the floating floor is assembled from interlocking, injection-molded, modular plastic tiles. Each tile includes a plastic support grid made of two sets of mutually-perpendicular intersecting walls. The intersecting wall structure produces an array of interstitial openings that is bounded by a perimetral wall. A support leg, positioned at each wall intersection point, provides structural reinforcement and stress reduction where the walls intersect. A continuous sheet of plastic material, which overlies the support grid, functions as a playing surface. A peripherally-positioned interlock structure, having both male and female components, enables the coupling of any tile to adjacent tiles. The support grid, the support legs, the continuous sheet of plastic material, and the interlock structure is all injection molded as a unitary piece. The interlock structure provides a continuous, uniform displacement gap between adjacent tiles, and also provides a yielding and resilient response to lateral mechanical forces, as well as to forces produced by thermal expansion. The tiles are preferably molded from a tough polymeric thermoplastic compound. It is suggested that low-density polyethylene and polypropylene copolymer are ideally suited for the application, as both polymers are very tough materials having high impact strength, high resistance to corrosive chemicals, and high resistance to abrasion. 
         [0006]    As the athletic floor tiles of the &#39;286 patent are preferably injection molded from polyolefin polymer plastics, a detailed description of polyolefin polymers is in order. Polyolefins are generally considered to be the most useful class of synthetic polymers. They are certainly the most widely-used polymers. Also known as polyalkenes, according to nomenclature established by the International Union of Pure and Applied Chemistry (IUPAC), polyolefins are generally prepared using organometallic catalysts, either in solution or supported on a solid surface. In the 1950s, the German chemist Karl Ziegler developed a catalyst for ethylene (ethene is its IUPAC name) polymerization based on a catalyst formed by the reaction of TiCl4 with Al(C2H5)3. Soon thereafter Giulio Natta of Italy made use of this type of catalyst for the polymerization of propylene (propene is its IUPAC name) to produce polymers with highly regular structures. The intimate details of the reactions of these commercial catalytic processes are not entirely understood, but there are strong indications from more easily studied soluble organometallic catalysts that alkenes coordinate to a metal center and then insert into a hydrocarbon chain, producing a longer-chain hydrocarbon attached to the metal center. Repetition of this process leads to extremely-long-chain hydrocarbon polymers. Polyethylene and polypropylene are the most well-known of this genre of polymers, as these plastics are used in consumer items ranging from milk containers and plastic bags to artificial limbs and car bumpers. Polyolefins, the only plastics that are lighter than water, are also break-resistant, non-toxic, and non-contaminating. Polyolefins are relatively inert. In fact, there is no known solvent for polyolefins at room temperature. They easily withstand exposure to nearly all chemicals at room temperature for up to 24 hours, although strong oxidizing agents eventually cause oxidation and embrittlement. Polyolefins are also damaged by long-term exposure to light. 
         [0007]    The polymerisation of ethylene results in an essentially straight chain, high molecular weight hydrocarbon. The polyethylenes are classified according to the relative degree of branching (side chain formation) in their molecular structures, which can be controlled with selective catalysts. Aggressive solvents will cause polyethylene to soften and swell, but these effects are normally reversible. Low-density polyethylene (LDPE) has more extensive branching, resulting in a less compact molecular structure. High-density polyethylene (HDPE) has minimal branching, which makes it more rigid and less permeable than LDPE. Linear low-density polyethylene (LLDPE) combines the toughness of low-density polyethylene with the rigidity of high-density polyethylene. Cross-linked high-density polyethylene (XLPE) is a form of high-density polyethylene wherein the individual molecular chains are bonded to each other (using heat, plus chemicals or radiation) to form a three-dimensional polymer of extremely high molecular weight. This structure provides superior stress-crack resistance and somewhat improves the toughness, stiffness and chemical resistance of HDPE. XLPE is a superior material for moulding very large storage tanks. Ultra high molecular weight polyethylene (UHMWPE), also known as high modulus polyethylene (HMPE) or high performance polyethylene (HPPE), is a thermoplastic. It has extremely long chains, with molecular weight numbering in the millions, usually between 2 and 6 million. The longer chain serves to transfer load more effectively to the polymer backbone by strengthening intermolecular interactions. This results in a very tough material, with the highest impact strength of any thermoplastic presently made. It is highly resistant to corrosive chemicals, with exception of oxidizing acids. It has extremely low moisture absorption, very low coefficient of friction, is self lubricating and is highly resistant to abrasion (15 times more resistant to abrasion than carbon steel). Its coefficient of friction is significantly lower than that of nylon and acetal, and is comparable to teflon, but UHMWPE has better abrasion resistance than teflon. 
         [0008]    Polypropylene (PP) is structurally similar to polyethylene, but each unit of the chain has a methyl group attached. It is translucent, autoclavable, and slightly more susceptible than polyethylene to strong oxidizing agents. It offers the best stress-crack resistance of the polyolefins. Products made of polypropylene are brittle at 0° C. and may crack or break if dropped from a height of more than several feet. 
         [0009]    Polypropylene copolymer (PPCO), which is also known as polyallomer (PA), is an essentially linear copolymer with repeated sequences of ethylene and propylene. It combines some of the advantages of both polymers. PPCO is autoclavable, and offers much of the high-temperature performance of polypropylene. It also provides some of the low-temperature strength and flexibility of polyethylene. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention provides a floating floor assembled from an array of interconnected subunits, each of which includes a stone, ceramic or porcelain tile and a one-piece polymeric plastic substrate to which the stone, ceramic, or porcelain tile is bonded. Each substrate is injection molded from certain polyolefin polymers and incorporates the interlock structure and other features of the modular sports tiles of &#39;286 patent. The substrates of the present invention, compared to the sports tiles, are modified in several ways. Firstly, the plastic support grid is formed by three sets of mutually intersecting walls, which are unitary with an upper laminar sheet that is coextensive with the support grid. Each set is angularly offset from the other two by 120 degrees, resulting in an array of interstitial openings having the shape of equilateral triangles. At the intersection of each pair of walls, there is a generally cylindrical support leg. Each support leg reduces stresses at the acute-angle intersections of the walls and, together, the multiple support legs provide additional support, thereby reducing the tendency of the support grid to collapse under load. The support grid is bounded by a perimetral wall, which forms the sides of the substrate. Secondly, each substrate is sized to precisely fit a stone, ceramic or porcelain tile. Each substrate incorporates an interlock structure about the outer perimeter, which includes both female and male components, and enables multiple subunits to be interconnected in an unbroken expanse. Each substrate may also incorporate tile locator tabs on a pair of intersecting sides. The locator tabs facilitate the uniform positioning of a tile on each substrate. Use of the locator tabs not only ensures that each stone or ceramic tile is square with its substrate, but that the tile will not shift on the substrate as the bond between the tile and the substrate sets up and cures. After an adhesive layer has been applied to the upper surface of the substrate and a stone, ceramic, or porcelain tile has been placed on top of the adhesive layer, the assembly is positioned on a slant so that gravity and the locator tabs can work in concert to maintain correct positioning of the tile until the adhesive is cured. Alternatively, pick and place equipment employing optical scanning sensors, can accurately position a stone, ceramic, or porcelain tile on each substrate. Small amounts of hot melt glue applied at the edges of the tile can be used to maintain proper positioning of the tile until the adhesive layer has cured sufficiently to prevent movement of the tile on the substrate. Hot melt glue is generally formulated from amorphous polypropylene, and is known to bond well to other polyolefin materials. The invention may be practiced with tiles of different shapes, including those having rectangular and hexagonal configurations. 
         [0011]    The toughness, rigidity, room-temperature resistance to chemicals, and abrasion resistance of certain polyolefin polymers that make them ideal materials for floor tiles also make adhesive bonding to those materials difficult. Polyolefins are known as “low energy” or “non-stick” plastics. The basically inert or inactive molecular structure of those materials is attributable to its “low energy state”. It is difficult to seal or bond such materials using commonly available sealant adhesives. Cyanoacrylate, epoxy, polyurethane, RTV silicone, and most acrylic adhesives simply will not stick to untreated polyethylene, polypropylene, or polypropylene copolymer. In the past, it has been necessary to treat the surface of polyolefin materials in order to convert their low-energy state to a higher-energy state. Surface treatments included oxidation, plasma treatment, corona treatment, flame treatment, and use of a high-surface-energy primer. 
         [0012]    Recently, 3M Corporation introduced a solvent-free, two-part, acrylic-based, structural plastic adhesive bearing the trademark Scotch-Weld® DP-8005 that allows structural bonding of polyolefins to themselves and to many other substrates. It uses a one-step process that requires no pre-treatment of the substrates other than removal of dirt and oil and a light sanding. A number of other companies have introduced similar products, and it is expected that even more adhesives for bonding polyolefins in a one-step process will be available in the future. 
         [0013]    As a consequence of the low-energy characteristics of polyolefin thermoplastic materials, the bonding surface of each of the substrates is treated by oxidation, plasma, corona, flame, or sprayed with a high-surface-energy primer prior to the application of an adhesive layer to the surface and positioning of a tile on top of the adhesive layer. It has been determined that the use of epoxy adhesive, applied after flame treatment of the upper surface, works well. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a bottom plan view of an injection molded, square polymeric plastic substrate fabricated in accordance with the present invention; 
           [0015]      FIG. 2  is a partial bottom plan view of four interconnected, square polymeric plastic substrates; 
           [0016]      FIG. 3  is enlarged partial bottom plan view of the four interconnected, square polymeric plastic substrates of  FIG. 2 ; 
           [0017]      FIG. 4  is a top plan view of a single square polymeric plastic substrate; 
           [0018]      FIG. 5  is a top plan view of the square polymeric plastic substrate of  FIG. 4 , following the application of adhesive to the upper surface thereof; 
           [0019]      FIG. 6  is a top plan view of a square tile subunit, which includes a substrate on which has been adhesively bonded a square stone, ceramic, or porcelain tile; 
           [0020]      FIG. 7  is bottom plan view of an injection molded, hexagonal polymeric plastic substrate fabricated in accordance with the present invention; 
           [0021]      FIG. 8  is a bottom plan view of four interconnected, hexagonal polymeric plastic substrates; 
           [0022]      FIG. 9  is enlarged partial bottom plan view of the four interconnected, hexagonal polymeric plastic substrates of  FIG. 8 ; 
           [0023]      FIG. 10  is a top plan view of a single hexagonal polymeric plastic substrate; 
           [0024]      FIG. 11  is a top plan view of the hexagonal polymeric plastic substrate of  FIG. 10 , following the application of adhesive to the upper surface thereof; and 
           [0025]      FIG. 12  is a top plan view of a tile subunit, which includes a hexagonal substrate on which has been adhesively bonded a hexagonal stone, ceramic, or porcelain tile. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    The invention will now be described with reference to the attached drawing figures. It should be understood that the drawings are not necessarily drawn to scale and are meant to be merely illustrative of the invention. The invention may be practiced using tiles of different shapes, including those having rectangular and hexagonal configurations.  FIGS. 1 through 6  disclose the manufacture and assembly of tiles having a rectangular configuration.  FIGS. 7 through 12  disclose the manufacture and assembly of tiles having a hexagonal configuration. 
         [0027]    Referring now to  FIG. 1 , a square polymeric plastic substrate  100 , fabricated in accordance with the present invention, is sized to accommodate the attachment on an upper surface thereof of a square stone, ceramic or porcelain tile. The substrate  100  is injection molded as a single piece thermoplastic material having the characteristics of exceptional toughness, stress-crack resistance, chemical resistance, and stiffness. Although these characteristics are typical of polyolefin thermoplastic materials in comparison to other thermoplastic polymers, the following polyolefins are considered the preferred materials for the application because they possess exceptional levels of the desired characteristics: low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), cross-linked high-density polyethylene (XLPE), ultra-high-molecular-weight polyethylene (UHMWPE), and polypropylene copolymer (PPCO). It will be noted that the underside of the substrate  100  incorporates support grid  101  formed by first, second and third sets of mutually intersecting walls ( 102 A,  102 B and  102 C, respectively). Each set is angularly offset from the other two by 120 degrees, resulting in an array of interstitial openings  103  having the shape of equilateral triangles. At the intersection of each pair of walls, there is a generally cylindrical support leg  104 . Each support leg  104  reduces stresses at the acute-angle intersections of the walls and, together, the multiple support legs provide additional support, thereby reducing the tendency of the support grid to collapse under load. The support grid  101  is capped with a square laminar sheet  105  that is unitary and coextensive with the support grid  101 , and covers an upper end of each interstitial opening  103 . The support grid  101  also has a square perimetral wall  106 , which is also unitary with the laminar sheet, and forms the four sides A, B, C and D of the substrate  100 . The substrate  100  incorporates an interlock structure about the outer perimeter, which enables removable interconnection of the substrate  100  to other identical substrates and to other substrates of compatible shape having the same interlock structure and interlock structure spacing. The interlock structure includes both female components  107 A- 107 H ( 107 , generally) and male components  108 A- 108 H ( 107 , generally). It will be noted that each of the female components  107  includes a U-shaped member  109  that is intersected by the perimetral wall  106 . Each of the male components  108  includes an arcuate member  110  and an associated locking tab  111 . When an arcuate member  110  and its associated locking tab  111  are inserted into a receiving female component  107 , the locking tab  111  clips over a bridging section  112  of the perimetral wall  106  which spans the U-shaped member  109 . So that the locking tab  111  may clip over the bridging section  112 , the bridging section  112  between each U-shaped member  109  is lower in height than the support grid  101  and the other portions of perimetral wall  106 . The interlock structure enables multiple substrates  100  to be interconnected in an unbroken expanse. It should be clear that an interlock structure where interlock components of like sex are on opposite sides of the substrate  100  is also a workable arrangement for enabling multiple substrates  100  to be interconnected in an unbroken expanse. For a presently utilized embodiment of the substrate, sized for 33 cm-square (13-inch-square) tile, substrate is about 0.375 inch thick, the interstitial openings are about 0.3125 inch deep, the laminar sheet  104  is about 0.0625 inch thick, the walls are about 0.625 inch thick, the support legs are about 0.155 inch in diameter, and the U-shaped members  109  of the female interlock components are about 0.625 inches in width, about 0.12 inch thick, about 0.20 inches in height, and project about 0.460 inch from the perimetral wall  106 . 
         [0028]    Referring now to  FIG. 2 , four square polymeric plastic substrates  100 -A,  100 -B,  100 -C and  100 -D have been interconnected by engaging the male components  108  of the interlock structure with the female components  107  thereof. 
         [0029]    Referring now to  FIG. 3 , this close-up view of a central portion of the four interconnected square polymeric plastic substrates  100  of  FIG. 2  shows, in more easily visible detail, the interlock interconnections between the four substrates  100 -A,  100 -B,  100 -C and  100 -D. It will be noted that at each male-to-female interlock engagement, the arcuate member  110  and associated locking tab  111  of each male component  108  is positioned within a U-shaped member  109  of a female interlock component  107 , and that the locking tab  111  is clipped over the bridging section  112  of the perimetral wall  106  that spans the gap between the U-shaped member  109 . 
         [0030]    Referring now to  FIG. 4 , a single square polymeric plastic substrate  100  is seen from the top. All that is visible in this view are the upper surface  401  of the laminar sheet  105 , the U-shaped member  109  of each female interlock component  107 , the locking tab  111  of each male interlock component  108 , and four, upwardly projecting locator tabs  402 A,  402 B,  402 C and  402 D ( 402 , generally), which are positioned on a pair of adjacent sides of the substrate  100 . In the past, it has been necessary to treat the surface of polyolefin materials in order to convert their low-energy state to a higher-energy state. Surface treatments included oxidation, plasma treatment, corona treatment, flame treatment, and use of a high-surface-energy primer. ioned at the very edges of a pair of intersecting sides B and C of the substrate  100 . The locator tabs  402  facilitate the uniform positioning of a stone, ceramic or porcelain tile on each substrate, as will be subsequently explained. If the tile is to be bonded to the upper surface  401  of the laminar sheet  105  using a specially-formulated adhesive, such as 3M Scotch-Weld® DP-8005, that allows structural bonding of polyolefins to themselves and to many other substrates, then no preliminary surface treatment of the upper surface  401  is required. However, if the tile is to be bonded to the upper surface  401  of the laminar sheet  105  with a conventional adhesive, such as epoxy, then it is necessary to treat the upper surface  401  in order the convert the surface molecules from a low-energy state to a higher-energy state that is more suitable for adhesive bonding within a normal range for room temperature. Surface treatments include oxidation, plasma treatment, corona treatment, flame treatment, and use of a high-surface-energy primer. Flame treatment has been used successfully for commercially-available product manufactured in accordance with the present invention. Flame treatment can be performed with a flame spreader, and using a flame fueled by propane. The flame includes a blue primary portion and a faint yellow secondary portion. The flame is adjusted so that the primary flame is contained with the spreader, and the secondary flame is about 1½″ beyond the spreader. The entire exposed upper surface  401  of the laminar sheet  105  is subjected to about five gentle strokes, with total exposure to the flame at any point on the surface being about 2 to 3 strokes. Exposure to the flame should not deform or melt the polyolefin surface in any way. Effective treatment of the upper surface  401  can be tested by wetting it with water. If the water runs off immediately, the treatment was not effective. However, if the water effectively wets the surface  401  as an uninterrupted sheet, the surface, one dry, is ready for bonding. 
         [0031]    Referring now to  FIG. 5 , epoxy adhesive has been spread in a striped pattern  501  on the now-treated surface  401 . 
         [0032]    Referring now to  FIG. 6 , a complete square subunit  600  has been created by placing a square stone, ceramic, or porcelain tile  601  atop the striped pattern  502  of applied uncured epoxy. Once the tile  601  has been positioned so that it is approximately centered on the substrate  100 , but within the confines four, upwardly projecting locator tabs  402 , the subunit  600  is placed, with the tile  601  above the substrate  100 , on a rack having a slant within a range of about 30 to 45 degrees for the epoxy adhesive  501  to cure. In this slanted position, the corner A-D of the subunit, which corresponds to the intersection of sides A and D, is at the highest elevation, corner B-C, which corresponds to the intersection of sides B and C is at the lowest elevation, and corners A-B and C-D, which correspond to the intersection of side A with side B and side C with side D, respectively, are generally at the same elevation. When the epoxy adhesive  501  has cured, the force of gravity will ensure that the tiles  601  are uniformly positioned on their associated substrates  100 . Assuming that each tile  601  is perfectly square, uniformly positioned means that each edge of each tile will be parallel to the underlying edge on its associated substrate  100 , and that the edges of the tile which are adjacent the upwardly projecting locator tabs  402 , will be equidistantly spaced from the respective underlying edges of the associated substrate  100  and that the edges of the tile which not adjacent the upwardly projecting locator tabs  402  will also be equidistant from the respective underlying edges of the associated substrate  100 . Because tiles vary slightly in dimension from batch to batch, as well as from manufacturer to manufacturer, the tiles  601  may not be perfectly centered on their associated substrates  100 . However, the slight offset is generally undetectable when the floor is laid. Nevertheless, this effect can be mitigated using pick and place equipment employing optical scanning and measurement sensors to accurately center a tile  601  on a substrate  100 , with the edges of the tile  601  being equidistant from the edges of the substrate  100 . Once pressure has been applied to the tile  601  in order to optimize contact with the striped pattern  502  of epoxy adhesive  501 , small amounts of hot melt glue, which are almost invisible to the naked eye, can be applied at the edges of the tile  601  in order to maintain proper positioning of the tile  601  until the epoxy adhesive  501  has cured sufficiently to prevent movement of the tile  601  on the substrate  100 . Hot melt glue is generally formulated from amorphous polypropylene, and is known to bond well to other polyolefin materials. 
         [0033]    Referring now to  FIG. 7 , a hexagonal polymeric plastic substrate  700 , fabricated in accordance with the present invention, is sized to accommodate the attachment on an upper surface thereof of a hexagonal stone, ceramic or porcelain tile. Like the square substrate  100  of  FIG. 1 , the hexagonal substrate  700  is injection molded as a single piece preferably from the same polyolefin thermoplastic materials, and the support grid  701  is also formed by first, second and third sets of mutually intersecting walls ( 702 A,  702 B and  702 C, respectively). Also as is the case with the square substrate, each set of walls is angularly offset from the other two by 120 degrees, resulting in an array of interstitial openings  103  having the shape of equilateral triangles, and at the intersection of each pair of walls, there is a generally cylindrical support leg  104 . The support grid  701  is capped with a hexagonal laminar sheet  705  that is unitary and coextensive with the support grid  701 . The support grid  701  also has a hexagonal perimetral wall  706 , which is also unitary with the laminar sheet, and forms the six sides E, F, G, H, I and J of the hexagonal substrate  700 . Also like the square substrate  100 , the hexagonal substrate  700  incorporates an interlock structure about the outer perimeter, which is essentially identical to that of the square substrate  100 . In this case, nine female components  107 A- 107 I ( 107 , generally) are distributed so that three are located on each of three alternating sides E, G and I. Nine male components  108 A- 108 I ( 107 , generally) are located on the other three sides F, H and J. As with the square substrate, each of the female components  107  includes a U-shaped member  109  that is intersected by (in this case) the hexagonal perimetral wall  706 . Each of the male components  108  includes an arcuate member  110  and an associated locking tab  111 . When an arcuate member  110  and its associated locking tab  111  are inserted into a receiving female component  107 , the locking tab  111  clips over a bridging section  712  of the hexagonal perimetral wall  706  which spans the U-shaped member  109 . So that the locking tab  111  may clip over the bridging section  712 , the bridging section  712  between each U-shaped member  109  is lower in height than the support grid  701  and the other portions of perimetral wall  706 . The interlock structure of the hexagonal substrate  700  functions in exactly the same manner as does the interlock structure of the square substrate  100 , thereby enabling multiple hexagonal substrates  700  to be interconnected in an unbroken expanse. The reader should be able to convince himself that an interlock structure where interlock components of like sex are three adjoining sides (for example female components  107  located on sides E, F and G and male components  108  located on sides H, I and J) is also a workable arrangement for enabling multiple hexagonal substrates  700  to be interconnected in an unbroken expanse. For a hexagonal substrate  700  that is, for example, 8.1 inches on a side, the substrate is about 0.375 inch (about 9.5 mm) thick, the interstitial openings are about 0.3125 inch deep, the laminar sheet  104  is about 0.0625 inch thick, the walls are about 0.625 inch thick, the support legs are about 0.155 inch in diameter, and the U-shaped members  109  of the female interlock components are about 0.625 inches in width, about 0.12 inch thick, about 0.20 inches in height, and project about 0.460 inch from the perimetral wall  706 . 
         [0034]    Referring now to  FIG. 8 , four hexagonal polymeric plastic substrates  700 -A,  700 -B,  700 -C and  700 -D have been interconnected by engaging the male components  108  of the interlock structure with the female components  107  thereof. 
         [0035]    Referring now to  FIG. 9 , this close-up view of a central portion of the four interconnected hexagonal polymeric plastic substrates  700  of  FIG. 8  shows, in more easily visible detail, the interlock interconnections between the four substrates  700 -A,  700 -B,  700 -C and  700 -D. It will be noted that at each male-to-female interlock engagement, the arcuate member  110  and associated locking tab  111  of each male component  108  is positioned a U-shaped member  109  of a female interlock component  107 , and that the locking tab  111  is clipped over the bridging section  712  of the perimetral wall  706  that spans the gap between the U-shaped member  109 . 
         [0036]    Referring now to  FIG. 10 , a single square polymeric plastic substrate  700  is seen from the top. All that is visible in this view are the upper surface  1001  of the hexagonal laminar sheet  705 , the U-shaped member  109  of each female interlock component  107 , the locking tab  111  of each male interlock component  108 , and four, upwardly projecting locator tabs  1002 A,  1002 B,  1002 C and  1002 D ( 1002 , generally), which are positioned on a pair of adjacent sides of the substrate  700 . Treatment of the upper surface Bonding of the tile to the In the past, it has been necessary to treat the surface of polyolefin materials in order to convert their low-energy state to a higher-energy state. Surface treatment of the upper surface  1001  of the hexagonal substrate  700  is performed in the same manner as previously detailed for the square substrates  100 . 
         [0037]    Referring now to  FIG. 11 , epoxy adhesive has been spread in a striped pattern  1101  on the upper surface  1001  after flame treatment or other comparable surface treatment. 
         [0038]    Referring now to  FIG. 12 , a complete hexagonal subunit  1200  has been created by placing a hexagonal stone, ceramic, or porcelain tile  1201  atop the striped pattern  1102  of applied uncured epoxy. Once the tile  1201  has been positioned so that it is approximately centered on the substrate  700 , but within the confines four, upwardly projecting locator tabs  1002 , the subunit  1200  is placed, with the tile  1201  above the substrate  700 , on a rack having a slant within a range of about 30 to 45 degrees for the epoxy adhesive  501  to cure. In this slanted position, the corner E-J of the subunit  700 , which corresponds to the intersection of sides E and J, is at the highest elevation, corner G-H, which corresponds to the intersection of sides G and H is at the lowest elevation, and corners E-F and I-J, which correspond to the intersection of side E with side F and side I with side J, respectively, are generally at the same elevation. When the epoxy adhesive  501  has cured, the force of gravity will ensure that the tiles  1201  are uniformly positioned on their associated substrates  700 . Assuming that each tile is perfectly hexagonal, uniformly positioned means that each edge of each tile  1201  will be parallel to the underlying edge on its associated substrate  700 , and that the edges of the tile which are adjacent the upwardly projecting locator tabs  1002 , will be equidistantly spaced from the respective underlying edges of the associated substrate  700  and that the edges of the tile which not adjacent the upwardly projecting locator tabs  1002  will also be equidistant from the respective underlying edges of the associated substrate  700 . Because tiles vary slightly in dimension from batch to batch, as well as from manufacturer to manufacturer, the tiles  1201  may not be perfectly centered on their associated substrates  700 . However, the slight offset is generally undetectable when the floor is laid. Nevertheless, this effect can be mitigated using pick and place equipment employing optical scanning and measurement sensors to accurately center a tile  1201  on a substrate  700 , with the edges of the tile  1201  being equidistant from the edges of the substrate  700 . Once pressure has been applied to the tile  1201  in order to optimize contact with the striped pattern  1102  of epoxy adhesive  501 , at least two small dabs of hot-melt glue, which are almost invisible to the naked eye, can be applied at the edges of the tile  1201  in order to maintain proper positioning of the tile  1201  until the epoxy adhesive  501  has cured sufficiently to prevent movement of the tile  1201  on the substrate  700 . 
         [0039]    Although only several embodiments of the invention have been disclosed herein, it will be obvious to those having ordinary skill in the art that changes and modifications may be made thereto without departing from the spirit and scope of the invention as hereinafter claimed.