Abstract:
A polymeric foam structure for use as a supporting pad for floor surface layers made from laminated flooring, carpet, tile, or other functional materials. The polymeric foam structure comprises a continuous band having increased density and consistent width along each side of the polymeric foam structure. The bands may have a flat surface or they may be optionally equipped with a plurality of peaks and valleys continuing along the band in an alternating grid pattern. The bands may be oriented so that the thickness step occurs from the same surface or that the thickness step occurs on opposite surfaces. The bands of increased foam density on the polymeric foam structure may be produced by a batch thermoforming process or continuous process comprising an apparatus having heated cylindrical rollers.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention is directed to a polymeric foam structure suitable for installation on floors as a supporting pad for the floor surface layer made from laminate flooring, carpet, tile, or other functional material.  
         [0002]     Modern floors for commercial and residential buildings generally comprise three layers. The lower layer is typically a permanent sub-floor with a raw, unfinished surface. This sub-floor may be made of concrete, wood, or other solid material. The center layer is typically a padding material called an “underlayment”. Underlayment in common use has been composed of a variety of flexible, resilient materials, such as cork, polymeric foams, felt, and rubber. The top flooring layer typically has a decorative finished exterior surface. The top layer may be laminate flooring, carpet, asphalt tiles, linoleum, or other solid materials. Depending upon the needs and desires of the trustee of the building, the underlayment and the decorative upper layer may be changed many times over the useful life of the building. Thus, it is desirable that the underlayment be readily removed and easily installed.  
         [0003]     The primary function of floor underlayment is to maximize the useful life of the decorative surface layer by absorbing shock in order to minimize wear. Additionally, the underlayment may serve to avoid impressing the unattractive surface pattern of a raw, unfinished sub-floor upon the top decorative floor surface.  
         [0004]     Floor underlayment has generally been supplied in roll form or in sheets of a particular length, dependent upon the underlayment manufacturer. Although there have been recent reports of additions of attached films to some underlayment structures made from polymeric foam, the shape of essentially all floor underlayment can be described as basically a rectangular parallelepiped.  
         [0005]     Floor underlayment is utilized in commercial and residential applications. In commercial applications, professional installers that have installation experience generally install floor underlayment. In residential applications, installers of floor underlayment may not have such prior experience. For both cases, ease of installation of the floor underlayment is a contributing factor to the cost and quality of the completed floor installation.  
         [0006]     A disadvantage of the simple rectangular parallelepiped floor underlayment structure is that its installation requires very precise positioning to avoid gaps between or overlaps of adjacent pieces of the underlayment. Precise positioning of the floor underlayment increases the installation time and the overall cost of the floor. Even small misalignment of the floor underlayment can produce unattractive seams, depressions, or bulges on the decorative flooring upper layer. Also, several manufacturers of decorative upper layer flooring materials state in the warranty the installation conditions and materials. When gaps in the underlayment are present, many warranties are null and void.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     It is an object of the present invention to produce a polymeric foam structure that is light in weight and easy to handle.  
         [0008]     It is another object of the present invention to produce a polymeric foam structure that has a useful life of many years.  
         [0009]     It is further object of the present invention to produce a polymeric foam structure with conventional foaming machinery.  
         [0010]     Lastly, it is an object of the invention to produce a resilient, non-brittle, low cost polymeric foam structure that is easy to install in the flooring application as underlayment.  
         [0011]     The polymeric foam structure of the present invention comprises two continuous bands of increased density and consistent width with a band along each side of the polymeric foam structure. The density of the foam within each band of increased density is about 150% to 300% of the mean density of the foam between the bands. The bands may have a flat surface or they may be optionally equipped with a plurality of peaks and valleys continuing along the band in an alternating grid pattern. The bands may be oriented so that the thickness step occurs on only one surface or so that the thickness steps occur on the opposite surfaces.  
         [0012]     The polymeric foam structure may be produced in a continuous or batch process. The two bands of increased foam density on each side of the polymeric foam structure may be imparted simultaneously or separately. Each band of increased foam density is produced by passing the desired width of the polymeric foam sheet through the foam density-increasing apparatus. The preferred foam density-increasing apparatus comprises two heated rollers equipped with annular rings. The heated rollers are maintained at a temperature that provides sufficient heat to produce the bands permanently on the polymeric foam structure. The heated surface of the annular rings may optionally be provided with a grid pattern comprising a plurality of alternating peaks and valleys. The gap between the rollers is set to be about 40% to 60% of the thickness of the sheet. Each roller set is positioned so that only the desired width of the increased density band of the polymeric foam structure is contacted by the heated roller surface. The resulting polymeric foam structure can be collected in roll form or sheets of a predetermined length.  
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0013]     Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawing.  
         [0014]      FIG. 1  is a perspective view illustrating an embodiment of the present invention with interlocking bands on opposing faces of the underlayment structure.  
         [0015]      FIG. 2  is a perspective view illustrating an embodiment of the present invention with interlocking bands on the same face of the underlayment structure.  
         [0016]      FIG. 3  is a cross-sectional view illustrating a cylindrical roller apparatus that could be utilized to prepare the present invention having interlocking bands on the opposing faces of the underlayment structure. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     In general usage the term “polymer” is accepted to mean naturally occurring or synthetic compounds consisting of large molecules made up of a linked series of many smaller identical molecules. These smaller molecules are referred to as monomers. The list of polymers in everyday use is extensive. Polymers in everyday use include polystyrene, such as in plastic beverage cups; polypropylene, such as in plastic utensils; polyethylene terephthalate, such as in carbonated beverage bottles; high density polyethylene, such as in plastic milk jugs; and linear low polyethylene, such as in plastic garbage bags.  
         [0018]     As referred herein, the term “polymeric foam” refers to materials that are comprised of a uniform and consistent mixture of one or more solid polymers and a gaseous material wherein the two phases are arranged so that the solid phase continuously encapsulates small cells of the gas throughout the domain of the material.  
         [0019]     As referred herein, the term “polymeric foam structure” refers to a physical object that is comprised of polymeric foam.  
         [0020]     As referred herein, the term “underlayment” refers to a physical object that is designed to be placed upon a floor between a sub-floor lower layer and a decorative flooring upper layer.  
         [0021]     As referred herein, the terms “bottom” and “top” of the polymeric foam structure refer to the relative vertical position of the surfaces when the structure is placed into service as a floor underlayment. The bottom surface of the underlayment contacts the sub-floor lower layer and the top surface supports the decorative flooring upper layer. The measurable dimension between the “bottom” and “top” surfaces is the thickness of the polymeric foam structure.  
         [0022]     As referred herein, the term “side” of the polymeric foam structure refers to the surfaces that are positioned perpendicular to the floor and extend in the major, or length direction of the structure. The measurable dimension between the two side surfaces is the overall width of the polymeric foam structure.  
         [0023]     As referred herein, the term “end” of the polymeric foam structure refers to the surfaces that are positioned perpendicular to the floor and extend in the minor, or width direction of the structure. The measurable dimension between the two end surfaces is the length of the polymeric foam structure.  
         [0024]     As referred herein, the term “band” refers to smaller intermediate surfaces that are essentially parallel to and between the top and bottom surface layers.  
         [0025]     The polymeric foam structure of the present invention comprises two continuous bands of increased density and consistent width with a band along each side of the polymeric foam structure. In general, the overall width of the polymeric foam structure of the present invention is between 0.2 m and 2.0 m. Preferably, the overall width of the polymeric foam structure is between 0.3 m and 1.5 m. Most preferably, the overall width of the polymeric foam structure is between 0.6 m and 1.3 m. In general, the thickness of the polymeric foam structure of the present invention is between 1.5 mm and 16 mm Preferably, the thickness of the polymeric foam structure is between 2.0 mm and 12 mm. Most preferably, the thickness of the polymeric foam structure is between 2.2 mm and 6.5 mm.  
         [0026]     In general, the width of a band of increased foam density should be between 1.5% and 15% of the overall width of the polymeric foam structure. Preferably, the width of a band of increased foam density should be between 2.5% and 10% of the overall width of the polymeric foam structure. Most preferably, the width of a band of increased foam density should be between 4.5% and 6.5% of the overall width of the polymeric foam structure.  
         [0027]     The most preferred embodiment consists of a base shape in which the continuous bands of increased density and consistent width are directed in opposing directions along the vertical thickness axis. An alternative preferred embodiment consists of a base shape in which the continuous bands of increased density and consistent width are directed in the same direction along the vertical thickness axis. The bands on the polymeric structure of either base shape may optionally be equipped with a pattern consisting of one-dimensional or two-dimensional arrangement of alternating peaks and valleys.  
         [0000]     Preferred Base Shape  
         [0028]     The illustration of  FIG. 1  depicts a three-dimensional perspective view of the Preferred Base Shape of the polymeric foam structure. This illustration is a schematic and the dimensions of thickness, width, and length are not in relative scale. The solid lines depict the junctions of the polymeric foam structure surfaces that would be visible if the actual physical object were viewed from the perspective angle. The dashed lines depict the junctions of the polymeric foam structure surfaces that would not be visible if the actual physical object were viewed from the perspective angle.  
         [0029]     Bottom Surface  20  of the polymeric foam structure will be placed in contact with the sub-floor lower layer. Top Surface  10  of the polymeric foam structure will be placed in contact with the decorative flooring upper layer. The vertical distance between Top Surface  10  and Bottom Surface  20  defines the thickness of the polymeric foam structure. The horizontal distance between Side Surface  16  and Side Surface  28  defines the width of the polymeric foam structure. The horizontal distance between End Surface  18  and End Surface  22  defines the length of the polymeric foam structure.  
         [0030]     Surface  14  constitutes one band of the polymeric foam structure. For this Base Shape, Surface  14  is referred herein as the “Top-Facing Band”. Surface  12  is also formed in the process of making Surface  14 . The horizontal distance between Surface  12  and Side Surface  16  is the width of the Top-Facing Band. The vertical distance between Top-Facing Band Surface  14  and Bottom Surface  20  is the thickness of the Top-Facing Band of the polymeric foam structure.  
         [0031]     Surface  26  constitutes the second band of the polymeric foam structure. For this Base Shape, Surface  26  is referred herein as the “Bottom-Facing Band”. Surface  24  is also formed in the process of making Surface  26 . The horizontal distance between Surface  24  and Side Surface  28  is the width of the Bottom-Facing Band. The vertical distance between Top Surface  10  and Bottom-Facing Band Surface  26  is the thickness of the Bottom-Facing Band of the polymeric foam structure.  
         [0032]     The thickness of the Top-Facing Band in general should be within 33 to 67% of the thickness of the polymeric structure. Preferably, the thickness of the Top-Facing Band is within 45% and 55% of the thickness of the polymeric structure. Most preferably, the thickness of the Top-Facing Band is within 48% and 52% of the thickness of the polymeric structure. The sum of the thickness of the Bottom-Facing Band and the thickness of the Top-Facing Band in general should be within 90% to 110% of the thickness of the polymeric structure. Preferably, the sum of the thickness of the Bottom-Facing Band and the thickness of the Top-Facing Band is within 95% to 105% of the thickness of the polymeric structure. Most preferably, the sum of the thickness of the Bottom-Facing Band and the thickness of the Top-Facing Band is within 98% to 102% of the thickness of the polymeric structure.  
         [0033]     The width of Bottom-Facing Band in general should be within 90% and 110% of the Top-Facing Band. Preferably, the width of Bottom-Facing Band is within 95% and 105% of the Top-Facing Band. Most preferably the width of Bottom-Facing Band is within 98% and 102% of the Top-Facing Band.  
         [0034]     The mean density of the polymeric foam structure between Top Surface  10  and Bottom-Facing Band Surface  26  and the mean density of the polymeric foam structure between Bottom Surface  20  and Top-Facing Band Surface  14  will generally be about 150% to 300% of the mean density of the polymeric foam structure for the volume bounded by the extension of the planes of Surface  12  and Surface  24  and Top Surface  10  and Bottom Surface  20 . Preferably, the mean density of the polymeric foam structure between Top Surface  10  and Bottom-Facing Band Surface  26  and the mean density of the polymeric foam structure between Bottom Surface  20  and Top-Facing Band Surface  14  is between 180% to 220% of the mean density of the polymeric foam structure for the volume bounded by the extension of the planes of Surface  12  and Surface  24  and Top Surface  10  and Bottom Surface  20 . Most preferably, the mean density of the polymeric foam structure between Top Surface  10  and Bottom-Facing Band Surface  26  and the mean density of the polymeric foam structure between Bottom Surface  20  and Top-Facing Band Surface  14  is between 195% to 205% of the mean density of the polymeric foam structure for the volume bounded by the extension of the planes of Surface  12  and Surface  24  and Top Surface  10  and Bottom Surface  20 .  
         [0035]     Top-Facing Band Surface  14  and Bottom-Facing Band Surface  26  can be flat, or they can optionally be formed with an embossed pattern. The embossed pattern can be of any combination of useful shapes that is repeatable throughout the band and which allow Top-Facing Band Surface  14  and Bottom-Facing Band Surface  26  to mate together without interference.  
         [0036]     Preferred embossed patterns consist of the following three-dimensional shapes: triangular grooves that extend in the width direction, triangular grooves that extend in the length direction, rectangular grooves that extend in the width direction, rectangular grooves that extend in the length direction, alternating pyramidal peaks and valleys wherein the height of the peaks is within 20% of the depth of the valleys, alternating conical peaks and valleys wherein the height of the peaks is within 20% of the depth of the valleys, and alternating frustoconical peaks and valleys wherein the height of the peaks is within 20% of the depth of the valleys.  
         [0037]     The most preferred embossed patterns consist of triangular grooves that extend in the length direction and alternating frustoconical peaks and valleys wherein the height of the peaks is within 10% of the depth of the valleys.  
         [0038]     In general, the vertical distance between the top of the peak of the embossed pattern and the bottom of the valley of the embossed pattern for the bands should not exceed 33% of the thickness of the polymeric foam structure. Preferably, the vertical distance between the top of the peak of the embossed pattern and the bottom of the valley of the embossed pattern for the bands should not exceed 25% of the thickness of the polymeric foam structure. Most preferably, the vertical distance between the top of the peak of the embossed pattern and the bottom of the valley of the embossed pattern for the bands should not exceed 15% of the thickness of the polymeric foam structure.  
         [0039]     For installation as floor underlayment, the length of the polymeric foam structure is aligned with the length of the floor. Generally, the Bottom-Facing band at the edge of the floor would be removed from the structure for the first piece to start the installation. Then, the Top-Facing Band Surface  14  of the First Piece A of the polymeric foam structure is optionally coated with any useful adhesive. Next, the Bottom-Facing Band Surface  26  of a Second Piece B of the similar polymeric foam structure is forced into contact to interlock with the Top-Facing Band Surface  14  of First Piece A. Continuing the Bottom-Facing Band Surface  26  of a Third Piece B of the similar polymeric foam structure is forced into contact to interlock with the Top-Facing Band Surface  14  of Second Piece B. In a similar fashion, each additional piece is added across the width of the floor, as needed. The Bottom-Facing Band Surface of each successive piece of polymeric foam structure is placed upon the corresponding Top-Facing Band Surface of the preceding piece of polymeric foam structure. To end the installation, the final piece is cut to the width of the floor.  
         [0000]     Alternate Base Shape  
         [0040]     The illustration of  FIG. 2  depicts a three-dimensional perspective view of an Alternate Base Shape of the polymeric foam structure. This illustration is a schematic and the dimensions of thickness, width, and length are not in relative scale. The solid lines depict the junctions of the polymeric foam structure surfaces that would be visible if the actual physical object were viewed from the perspective angle. The dashed lines depict the junctions of the polymeric foam structure surfaces that would not be visible if the actual physical object were viewed from the perspective angle.  
         [0041]     In this Base Shape, Surface  20  and Surface  10  will alternate as top and bottom surfaces in actual usage as underlayment. For approximately one-half of the underlayment installation, Surface  20  of the polymeric foam structure will be placed in contact with the sub-floor lower layer and thus Surface  10  of the polymeric foam structure will be placed in contact with the decorative flooring upper layer. For the balance of the underlayment installation, Surface  10  of the polymeric foam structure will be placed in contact with the sub-floor lower layer and thus Surface  20  of the polymeric foam structure will be placed in contact with the decorative flooring upper layer. The vertical distance between Surface  10  and Surface  20  defines the thickness of the polymeric foam structure. The horizontal distance between Side Surface  12  and Side Surface  28  defines the width of the polymeric foam structure. The horizontal distance between End Surface  18  and End Surface  22  defines the length of the polymeric foam structure.  
         [0042]     Surface  14  constitutes the first band of the polymeric foam structure for this Base Shape. Surface  12  is also formed in the process of making Surface  14 . The horizontal distance between Side Surface  12  and Surface  16  is the width of the Surface  14 .  
         [0043]     Surface  26  constitutes the second band of the polymeric foam structure for this Base Shape. Surface  24  is also formed in the process of making Surface  26 . The horizontal distance between Side Surface  24  and Surface  28  is the width of the Surface  26 .  
         [0044]     The width of Surface  26  in general should be within 90% and 110% of the Surface  14 . Preferably, the width of Surface  26  is within 95% and 105% of the Surface  14 . Most preferably the width of Surface  26  is within 98% and 102% of the Surface  14 .  
         [0045]     The mean density of the polymeric foam structure between Surface  10  and Band Surface  26  and the mean density of the polymeric foam structure between Surface  10  and Band Surface  14  will be generally be about 150% to 300% of the mean density of the polymeric foam structure for the volume bounded by the extension of the planes of Surface  16  and Surface  24  and Surface  10  and Surface  20 . Preferably, the mean density of the polymeric foam structure between Surface  10  and Band Surface  26  and the mean density of the polymeric foam structure between Surface  10  and Band Surface  14  is within about 180% to 220% of the mean density of the polymeric foam structure for the volume bounded by the extension of the planes of Surface  16  and Surface  24  and Surface  10  and Surface  20 . Most preferably, the mean density of the polymeric foam structure between Surface  10  and Band Surface  26  and the mean density of the polymeric foam structure between Surface  10  and Band Surface  14  is within about 195% to 205% of the mean density of the polymeric foam structure for the volume bounded by the extension of the planes of Surface  16  and Surface  24  and Surface  10  and Surface  20 .  
         [0046]     Surface  14  and Surface  26  can be flat, or they can optionally be formed with an embossed pattern. The embossed pattern can be of any combination of useful shapes that is repeatable throughout the band and which allow Surface  14  and Surface  26  to mate together without interference.  
         [0047]     Preferred embossed patterns consist of triangular grooves that extend in the width direction, triangular grooves that extend in the length direction, rectangular grooves that extend in the width direction, rectangular grooves that extend in the length direction, alternating pyramidal peaks and valleys wherein the height of the peaks is within 20% of the depth of the valleys, alternating conical peaks and valleys wherein the height of the peaks is within 20% of the depth of the valleys, and alternating frustoconical peaks and valleys wherein the height of the peaks is within 20% of the depth of the valleys.  
         [0048]     The most preferred embossed patterns consist of triangular grooves that extend in the length direction and alternating frustoconical peaks and valleys wherein the height of the peaks is within 10% of the depth of the valleys.  
         [0049]     In general, the vertical distance between the top of the peak of the embossed pattern and the bottom of the valley of the embossed pattern for the bands should not exceed 33% of the thickness of the polymeric foam structure. Preferably, the vertical distance between the top of the peak of the embossed pattern and the bottom of the valley of the embossed pattern for the bands should not exceed 25% of the thickness of the polymeric foam structure. Most preferably, the vertical distance between the top of the peak of the embossed pattern and the bottom of the valley of the embossed pattern for the bands should not exceed 15% of the thickness of the polymeric foam structure.  
         [0050]     For installation as floor underlayment, the length of the polymeric foam structure with the Alternate Base Shape is aligned with the length of the floor. First Piece A of polymeric foam structure is positioned so that its Surface  10  is in contact with the sub-floor lower layer. Generally, at the edge of the floor, Surface  26  and the volume of material associated with it would be removed from the structure of this piece to start the installation. Then, Surface  14  of the First Piece A of the polymeric foam structure is optionally coated with any useful adhesive. Next, Second Piece B of polymeric foam structure is positioned so that its Surface  20  is in contact with the subfloor lower layer. Surface  26  of a Second Piece B of the similar polymeric foam structure is forced into contact to interlock with Surface  14  of First Piece A. Continuing, Third Piece C is inverted in a manner to First Piece A so that its Surface  10  is in contact with the sub-floor lower layer. Surface  26  of Third Piece C of the similar polymeric foam structure is forced into contact to interlock with the Surface  14  of Second Piece B. In a similar fashion, additional pieces are added across the width of the floor, as needed, after placement of each Surface of each successive piece of polymeric foam structure on the corresponding surface of the preceding piece of polymeric foam structure. To end the installation, the final piece is cut to the width of the floor.  
         [0000]     Polymeric Foam Structure Material Composition  
         [0051]     The polymeric foam structure of the present invention can be composed of any useful polymeric foam material. In general, the particular polymeric foam chosen for the polymeric foam structure should have a Vertical Compression Set at 25% compression of less than 25%, as measured in accordance with ASTM D-3575. Although ASTM D-3575, entitled “Standard Test Methods for Flexible Cellular Materials Made from Olefin Polymers”, is specifically designed for polyolefins, such as low density polyethylene (LDPE) and polypropylene, application of the measurement procedures for this test produce reasonable results for certain polymeric foams that are not specifically polyolefins.  
         [0052]     Suitable polymeric foams for the present invention will generally have a foam density between 10 and 300 kg/m 3 . Suitable polymer foams for material composition of the polymeric foam structure include, but are not limited to: polyurethane, polypropylene, low density polyethylene, two-polymer blend foams comprising low density polyethylene and an ethylene copolymer, two-polymer blend foams comprising polypropylene and a thermoplastic elastomer, two-polymer blend foams comprising high density polyethylene and polystyrene, three-polymer blend foams comprising high density polyethylene, polystyrene, and low density polyethylene, and three-polymer blend foams comprising high density polyethylene, polystyrene, and linear low density polyethylene.  
         [0053]     Preferred polymeric foams for the present invention have a foam density between 20 and 100 kg/m 3 . Most preferred polymeric foams for the present invention have a foam density between 25 and 65 kg/m 3 .  
         [0000]     Process of the Present Invention  
         [0054]     The polymeric foam structure of the present invention can be made by a batch process, such as by thermoforming, or by a continuous process. Preferably, the polymeric foam structure is made in a continuous process.  
         [0055]     According to one batch process for the present invention, sheet lengths of the polymeric foam sheet are placed in a thermoforming oven with localized heating elements and heated to the softening point of the polymeric foam sheet. The band and the desired embossed pattern are impressed upon the softened area by the platens of the thermoforming apparatus.  
         [0056]     According to one continuous process of the present invention, polymeric foam sheet either from roll stock or from continuous foam sheet manufacturing equipment is drawn continuously through a rotating roller stand containing at least two heated cylindrical rolls. The heated cylindrical rolls are heated to a temperature that is sufficient to permanently deform the polymeric foam after the sheet comes in contact with the rolls.  FIG. 3  depicts the cross sectional of one configuration for the heated roller apparatus that could be utilized to prepare the polymeric foam structure with the band surfaces in the opposing direction.  
         [0057]     In  FIG. 3 , Top Cylindrical Roll  12  is equipped with Top Annular Ring  10 . Top Annular Ring  10  is affixed with the inverse of the embossed pattern, if any, to be placed upon the Top-Facing Band. Bottom Cylindrical Roll  16  is equipped with Bottom Annular Ring  20 . Bottom Annular Ring  20  is affixed with the inverse of the embossed pattern, if any, to be placed upon the Bottom-Facing Band. The horizontal distance between the Top Annular Ring  10  and Bottom Annular Ring  20  is configured to be the overall width of the polymeric foam structure diminished by the sum of the widths of the Top-Facing Band and Bottom Facing Band. The distance between the Cylindrical Roll  12  and Cylindrical Roll  16  is Roll Gap  18 . The measurement of Roll Gap  18  is configured to be 105% to 110% of the thickness of the polymeric foam structure. The distance between the Top Annular Ring  10  and Bottom Cylindrical Roll  16  forms Top-Facing Band Gap  14 . Top-Facing Band Gap  14  is configured to be 98% to 102% of the thickness of the Top-Facing Band of the polymeric foam structure. The distance between the Top Cylindrical Roll  12  and Bottom Annular Ring  20  forms Bottom-Facing Band Gap  22 . Bottom-Facing Band Gap  22  is configured to be 98% to 102% of the thickness of the Bottom-Facing Band of the polymeric foam structure. In operation, polymeric foam sheet is aligned and continuously drawn through the rotating heated roller apparatus, so as to produce the polymeric foam structure with the desired dimensions.  
         [0058]     One skilled in the art can determine that a heated roller apparatus could similarly be made to produce the polymeric foam structure having the Alternate Base Shape with the bands on the same surface. In this case Annular Ring  10  and Annular Ring  20  would be placed upon the same cylindrical roller.  
         [0059]     While the present invention has been described with reference to one or more particular embodiments, those skilled in the art will recognize that many changes may be made thereto without departing from the spirit and scope of the present invention. Each of these embodiments and obvious variations thereof is contemplated as falling within the spirit and scope of the claimed invention, which is set forth in the following claims.