Abstract:
A sealed glazing unit simulating the appearance of a traditional divided-lite window has spaced apart parallel co-extensive glazing sheets interconnected by a peripheral seal. Muntin grid elements are located on at least two surfaces of the glazing sheets in mutually aligned registration, the elements being of a width sufficient to create a visual illusion of solid muntin bars within the glazing sheet cavity. Each of the muntin grid elements has on one side a relatively dark shade facing interiorly of the glazing unit and in the opposite side a relatively light shade facing exteriorly of the glazing unit, the combination of these shades creating the visual appearance of solid muntin bars within the cavity. Muntin grid elements within the glazing unit are preferably in the form of strips of plastic material adhered to the cavity glass surfaces, whereas muntin grid elements on the exterior surfaces of the unit can alternatively be formed as relatively thick members e.g. of wood, or of hollow aluminum or plastic.

Description:
BACKGROUND OF THE INVENTION 
     a) Field of Invention 
     This invention relates generally to multiple-pane sealed glazing units and more particularly to units that incorporate decorative features that simulate the appearance of traditional divided-lite windows. 
     b) Description of the Prior Art 
     In U.S. Pat. No. 5,494,715, issued to Glover, there is a description of the various efforts that have been made in recent years to improve both the energy efficiency and condensation resistance of multiple glazed sealed units. These improvements include: low-e coatings, argon or krypton gas fill, insulating spacingand-desiccant systems for perimeter edge seals and narrow-width cavities (approximately ⅜″ spacing for argon gas filled units). 
     As also noted in U.S. Pat. No. 4,494,715, there is a growing consumer interest in heritage window features. Perhaps the most popular of these features is the addition of muntin bars that create the appearance of colonial style divided-lite windows. In the past, various efforts have been made to simplify the assembly of these divided-lite windows and these efforts have been documented in the patent literature. 
     U.S. Pat. No. 4,598,520 issued to Ellstrom describes the use of two separate but aligned wood muntin grid assemblies that are permanently adhered to either side of a multiple-pane sealed unit using double-sided adhesive foam tape. When viewed at a somewhat inclined angle, the visual illusion is created of a solid muntin-grid assembly. However, when viewed at a more oblique angle, this visual illusion is lost because daylight can be seen between the two muntin grid assemblies. 
     U.S. Pat. No. 4,738,938 issued to Palmer describes a muntin-grid window assembly similar to the assembly described in the Ellstrom patent but where an additional metal muntin-grid is also incorporated within the sealed unit. However, although the addition of a metal spacer muntin-grid better simulates the appearance of a divided-lite window, window energy efficiency is reduced because of increased heat loss through the muntin grid assembly. 
     U.S. Pat. No. 5,345,743 issued to Baier describes a muntin grid window assembly similar to the assembly described in the Palmer patent but where a flexible foam spacer with pre-applied adhesive is substituted for the metal spacer grid. Although more energy efficient than a simulated divided-lite window with a metal spacer muntin-grid, the double muntin grid assembly method still remains a labour intensive manufacturing process and the grid assembly is still a weak link in the thermal envelope. 
     U.S. Pat. No. 5,494,715 issued to Glover describes how the visual illusion of a muntin grid window is created by means of decorative stripe patterns that are applied to the three separate glazing sheets of a triple glazed unit with the glazing sheets being typically located no more than ⅜″ apart. 
     Traditional wood muntins are typically colored white, and when all three muntin stripes are colored white, experience has shown that because of various shading and optical effects, a convincing visual illusion of a divided lite window is not always created. The decorative surface patterns can be fabricated from a wide range of materials, including inks and paints. Because of potential durability problems, the stripe material must be non-outgassing and with high volume production methods, experience has again shown that for typical coating materials, this is a very demanding technical requirement. 
     SUMMARY OF THE INVENTION 
     The present invention provides a sealed glazing unit that simulates the appearance of a traditional divided-lite window, said sealed glazing unit comprising: two spaced apart parallel co-extensive glazing sheets; a peripheral seal extending continuously between the edges of said glazing sheets to define an insulating cavity between said two glazing sheets; muntin grid elements located on at least two surfaces of said glazing sheets, said muntin grid elements on respective surfaces being in mutually aligned registration with each other and of a width parallel to the glazing sheet surfaces that is sufficient to create the visual illusion of solid muntin bars within said cavity; wherein each said muntin grid element has one side that is of a relatively light shade and an opposite side that is of a relatively dark shade, said elements being attached to said glazing sheets in an orientation such that the side of relatively light shade is presented towards the adjacent exterior side of the glazing unit whereas the side of relatively dark shade is presented towards the opposite side; wherein at least one of said two surfaces is located within said cavity, the muntin grid elements on said at least one surface comprises a decorative grid pattern that is in the form of thin strips applied to said one surface. 
     The thin strips are preferably made from a flexible tape that carries a pre-applied pressure sensitive adhesive thereon, the tape most preferably being of plastic sheet material such as polyethylene terephthalate. The adhesive may be at least partially of acrylic material. The strips incorporate a dark shade coating on one side, the other side being of a light shade to create the above discussed appearance. 
     Instead of strips of plastic material, the muntin grid elements could be formed by applying a layer of ceramic frit material, and this material can readily be formulated to be dark on one side and light on the other. 
     The muntin grid elements or muntin pattern elements on both of the glazing sheets may both be within the insulating cavity, but since all of the strips are relatively thin, they do not significantly detract from the heat insulation properties of the cavity. The glass sheets are preferably spaced no more than about 10 mm apart, and the cavity filled with argon gas or the like. 
     The invention also provides a sealed glazing unit that simulates the appearance of a traditional divided-lite window, said sealed glazing unit comprising: 
     three spaced apart parallel co-extensive glazing sheets; a peripheral seal extending continuously between the edges of said glazing sheets to define a respective insulating cavity between each adjacent pair of said glazing sheets; first muntin grid elements located on the outer surfaces of the outer two of said glazing sheet, secondary muntin grid elements being in the form of thin strips attached to the central one of said glazing sheets, said muntin grid elements on respective surfaces being in mutually aligned registration with each other and of a width parallel to the glazing sheet surfaces that is sufficient to create the visual illusion of solid muntin bars within said cavity; wherein each of said first muntin grid elements has one side that is of a relatively light shade and an opposite side that is of a relatively dark shade, said elements being attached to said glazing sheets in an orientation such that the side of relatively light shade is presented towards the adjacent exterior side of the glazing unit whereas the side of relatively dark shade is presented towards the opposite side; and wherein said secondary muntin grid elements have opposite sides that are both of a shade corresponding to said relatively dark shade. 
     The secondary muntin grid elements may take any of the forms discussed in the foregoing. The first muntin grid elements may be in the form of thin strips attached to the cavity faces of said outer glazing sheets. Alternatively they may comprise bulky profile members, but in either case they include outwardly presented surfaces that are of the relatively light shade and surfaces presented towards the interior of the cavity having the appearance of the relatively dark shade. The bulky profiles can be adhered to the glazing sheets by the use of adhesive foam tapes, and may for example be formed by co-extruded PVC profiles. In this case the PVC profile will comprise a rigid hollow PVC profile with flexible longitudinal edge fins to engage against the glass surface. These fins, as well as the adhesive foam tape securing the profile to the glass, will be of the dark shade. 
     Alternatively the bulky profile members may be of wood or they comprise aluminum extrusions. 
     The central glazing sheet may comprise a tensioned flexible film incorporating pre-applied secondary grid elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following is a description by way of example of certain embodiments of the present invention, reference being made in the accompanying drawings, in which: 
     FIG. 1 shows a fragmentary perspective view of a double glazing assembly that simulates the appearance of a muntin grid window. 
     FIG. 2 shows a cross sectional bottom-edge detail of a double glazing assembly that simulates the appearance of a muntin grid window. 
     FIG. 3 shows a fragmentary perspective view of a triple glazing assembly that simulates the appearance of a muntin grid window. 
     FIG. 4 shows a cross section bottom edge detail of a triple glazing assembly that simulates the appearance of a muntin grid window. 
     FIG. 5 shows a fragmentary perspective view of a triple glazing unit that simulates the appearance of a divided-lite window with co-extruded PVC plastic muntin profiles adhered to the outer surface of the glazing unit. 
     FIG. 6 shows a cross sectional detail of a triple glazing unit that simulates the appearance of a divided-lite window with PVC plastic muntin profiles adhered to the outer surfaces of the glazing unit. 
     FIG. 7 shows an elevational view of a triple glazing unit that simulates the appearance of a simulated divided-lite window with an Austrian-pattern decorative border trim. 
     FIG. 8 shows a cross sectional, bottom edge detail of a triple glazing unit that simulates the appearance of simulated divided- lite window with an Austrian pattern decorative border trim. 
     FIG. 9 shows a fragmentary perspective view of a triple glazing unit that simulates the appearance of a divided-lite window and features wood muntin profiles adhered to the glazing unit. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a fragmentary perspective view of a double glazing assembly that simulates the appearance of a traditional divided-lite window. The double glazed unit  20  consists of an inner and outer rigid glazing sheets  21  and  22  which are typically spaced less than 10 mm apart (⅜″ approx.). The rigid glazing sheets are typically made from glass although plastic and other transparent sheet materials can also be used. 
     A vertical strip of adhesive tape material  23  is applied to the cavity surface  24  of the inner glazing sheet  21 . To create a grid pattern, horizontal strips  25  and  26 , are applied at right angles to the vertical strip  23 . At the intersection points  27  and  28  between the vertical and horizontal strips, the horizontal strips  25  and  26  are simply laid over the vertical strip  23 . With ⅜″ cavity, the width of the adhesive tapes  23  material is preferably about ⅝″, but could be anywhere from ½″ to ¾″ or even longer. A minimum width of about ½″ is required to provide the desired visual effect. 
     The adhesive tape material is typically made from plastic sheet materials with a pre-applied pressure sensitive adhesive. One preferred material option for the plastic sheet material is polyethylene terephthalate (PET), and acrylic is the preferred material option for the pressure sensitive adhesive. The outer adhesive surface  29  of the tape is coloured a relatively light shade while the inner surface  30  of the tape is coloured a relatively dark shade. For muntin grid windows, the lighter shade is typically white while the darker shade is typically black. 
     For ease of application, and so there is no need to bend or stretch the tape at the intersection points  27  and  28 , the sheet material thickness should be less than 0.005″ and preferably 0.002″ or less. The thickness of the adhesive material is typically about 0.001″ in thickness. 
     A second vertical adhesive tape strip  32  is applied to the cavity surface  33  of the outer glazing sheet  22 . The second strip  32  is generally in coincidental alignment with the first strip  23 . A second set of horizontal strips  34  and  35  are similarly applied to the cavity surface  33  of the outer glazing sheet  22  and again this second set of horizontal stripes is in coincidental alignment with the first set. 
     When viewed at an oblique angle as seen in FIG. 1, the eye sees both the light-color surface  29  of adhesive tape  31  on the inner glazing sheet  21  as well as part of the inner dark surface  30  of the adhesive tape  31  on the outer glazing sheet  22 . Because of the narrow spacing between the glazing sheets  21  and  22 , and the width of the adhesive tape  23  and the dark colored inner surface  30 , the visual illusion is created of a solid muntin profile. 
     Although a simple grid pattern is shown in FIG. 1, it can be appreciated by those skilled-in-the-art that a wide variety of different strip patterns can be created. These traditional muntin grid patterns can include: Gothic, Victorian, Georgian, Queen Anne, Cathedral, Tudor, Arch, Sunburst, Sunray and Austrian patterns. 
     FIG. 2 shows a bottom edge cross sectional detail of the double glazing assembly shown in FIG.  1 . The two glazing sheets  21  and  22  are conventionally sealed at the perimeter edge  36 . 
     Although different types of perimeter edge seals can be used, one preferred option is the combination of an insulating foam spacer  37  and thermoplastic sealant  38 . The insulating foam spacer  37  is made from silicone or EPDM rubber-sponge material that incorporates desiccant fill. A vapour barrier backing  39  is laminated to the back face of the spacer and a pressure sensitive acrylic adhesive is incorporated on the spacer sides  40 . The front face  44  features a smooth non-reflective finish that can be color matched with the dark shade color of the adhesive tape strip  31 . Marketed under the name of Super Spacer®, the insulating foam spacer  37  is manufactured by Edgetech IG of Cambridge, Ohio. 
     As previously described, a light-and-dark adhesive tape  31  is applied to the glazing cavity surfaces  24  and  33 . The light-and-dark adhesive tape  31  is adhered to the glazing sheets with a pre-applied pressure sensitive adhesive  43 . Although various adhesive materials can be used, one preferred option is to use an acrylic pressure sensitive adhesive. The light-and-dark tape  31  can be made from various sheet materials with plastic film being the preferred option. Different plastic sheet materials can be used with polyethylene terephthalate (PET) being one preferred material option. 
     As shown in FIG. 2, the light-and-dark adhesive tape is made from white PET film material  42  that is finished with a black paint or coating  46 . Alternatively, the light-and-dark color tape material can be made from separate white and black PET film sheet materials that are laminated together. A further option is for the light-and-dark adhesive tape to be made from PET sheet material that is dark in color with a pre-applied adhesive layer that is light in color. 
     Because the adhesive tape is located within a sealed unit, both the plastic sheet and adhesive must be non-outgassing and pass the demanding test requirement of the Canadian CGSB 12.8 volatile fogging test procedure. The tape material must also be color stable and not fade or yellow over time. 
     Although the strips illustrated in FIG. 2 are made from adhesive tape, it can be appreciated by those skilled-in-the-art that the light-and-dark stripes can be made from various materials including: multi-layers of UV paints, inks and ceramic frit material. 
     Compared to inks or paints the main advantage of using adhesive tape is that the material is fully cured and potential problems with volatile outgassing can be minimized. Also, compared to paints and inks, the two color tone adhesive tape can be applied both at high speeds and in a single pass operation. 
     In case of ceramic frit material, a two tone, heat transfer decal can be used and this allows for a single pass operation. The ceramic frit material is fused to the glass at high temperatures and as a result, there is no volatile outgassing or color fading. A strip or material element that forms the pattern on a single glazing sheet can be referred to generically as a muntin pattern element. 
     FIG. 3 shows a fragmentary perspective view of a triple glazing assembly that simulates the appearance of a traditional muntin grid window. The triple glazed unit  47  consists of an inner and outer rigid glazing sheet  21  and  22 , and also a center glazing sheet  48 . The three glazing sheets are typically spaced less than 10 mm (⅜″) apart. Generally all three glazing sheets are fabricated from flat glass sheet material although the center glazing sheet  48  can also be made from a tensioned, flexible plastic film. 
     As with the double glazing unit shown in FIG. 2, a vertical light-and-dark strip  23  and horizontal strips  25  and  26  are applied in a grid pattern to the cavity side of inner glazing sheet  21 . A vertical light-and-dark strip  32  and horizontal strips  34  and  35  are also applied to the cavity side of outer glazing sheet in coincidental alignment with the first grid pattern. Both sets of light-and-dark strips are about ⅝″ in width. 
     A vertical dark strip  49  is applied to the interior cavity surface  50  of the center glazing pane  48  and this strip  49  is generally in coincidental alignment with the outer two strips  23  and  32 . Similarly, horizontal dark strips  51  and  52  are also applied to the interior cavity surface  50  of center glazing sheet  48  and these strips  51  and  52  are also in coincidental alignment with the outer two sets of strips  25 , 34  and  26 , 35 . In combination, the dark strips  49 , 51  and  52  create a grid pattern that is generally in coincidental alignment with the grid patterns on the inner and outer glazing sheets. 
     As shown in FIG. 3, one option is for the center pane strips  49 , 51  and  52  to be about ¼″ larger in width than the two sets of strips  23 , 25 , 26  and  32 , 34 , 35  on the two outer glazing sheets  21  and  22 . 
     When viewed at an oblique angle, the eye sees both the outer light surface  29  of the adhesive tape on the inner glazing sheet  21  as well as part of the dark surface  53  on the center glazing pane  48  and the inner dark surface  30  of the adhesive tape  31  on the outer glazing sheet  22 . Because of the dark colored surfaces  30  and  52 , and also because of the narrow spacing between the glazing sheets  21 ,  48  and  22 , a visual illusion of a solid muntin profile is created. 
     FIG. 4 shows a bottom edge cross sectional detail of the tripleglazed unit  47  shown in FIG.  3 . For improved energy efficiency, the cavity spaces  42  between the glazing sheets  21 , 48  and  22  are typically filled with argon gas. The three glazing sheets  21 , 48  and  22  are conventionally sealed at the perimeter edge and one preferred edge-seal configuration is the combination of desiccant filled, thermoset rubber foam spacers  37  and thermoplastic sealant material  38 . 
     As previously described, light-and-dark adhesive tape material  31  is applied in a grid pattern to the cavity surfaces  24  and  33 . A dark tape  53  is applied in a grid pattern to one of the cavity surfaces of the center glass pane  48 . Although various plastic sheet materials can be used, one preferred option is to fabricate the dark tape  53  from PET film material. 
     FIG. 5 shows a fragmentary perspective view of a triple glazing unit  47  that simulates the appearance of a divided-lite window with co-extruded PVC plastic muntin profiles  54 . The triple glazed unit  47  consists of an inner and outer rigid glazing sheets  21  and  22  and a center glazing sheet  48 . Typically the three glazing sheets  21 ,  22  and  48  are spaced less than 10 mm (⅜″) apart. A decorative grid pattern  55  is applied to the center glazing pane  48  and typically, the decorative grid pattern  55  is made from plastic sheet tape material with a pre-applied pressure sensitive adhesive. As previously noted, the preferred tape material is PET film and the preferred adhesive is acrylic. 
     Linear rigid profiles  56  and  57  are applied to the inner and outer glazing sheets  21  and  22  and the profiles  56  and  57 , are generally in coincidental alignment with the center grid pattern  55 . The rigid profiles can be made from various materials and one preferred option is for the profile to be made from a hollow PVC co-extrusion  61  consisting of a rigid light colored hollow channel  58  and flexible outer dark colored longitudinal perimeter edge fins  59 . Generally, the edge fins  59  are similar in shape and size to the co-extruded glazing seals of the PVC window frame (not shown). 
     The profiles  56  and  57  are applied to the glazing sheets  21  and  22  using adhesive foam tape  60 . Although various material options can be used, one preferred material configuration is a dark colored polyethylene foam with pre-applied pressure sensitive acrylic adhesive. 
     When the composite muntin grid assembly is viewed at an oblique angle, the visual illusion is created of a traditional divided-lite window. This illusion is enhanced if the adhesive foam tapes  60 , the flexible PVC extrusion edge fins  59 , the tape grid strips  53  and the perimeter spacer  37  (FIG. 6) are essentially the same dark color and because of material availability, the preferred color is black. 
     FIG. 6 shows a bottom-edge cross sectional detail of the triple glazed unit shown in FIG.  5 . The three glazing sheets  21 , 48  and  22  are conventionally sealed at the perimeter edge and as previously noted, one preferred option is to use the combination of desiccant-filled, thermoset rubber foam spacers  37  and thermoplastic sealant material  38 . Dark shade adhesive tape material  53  is applied in a grid pattern to one of the cavity surfaces of the center glass sheet  48 . Linear hollow channel, PVC profiles  56  and  57  are adhered to the outer surfaces of glazing sheets  21  and  23  using adhesive foam tape  60  and the profiles are in coincidental alignment with the dark shade stripe  53  on the center glass pane  48 . Generally, the width of the dark colored center strip  53  is about ⅛″ less than the width of the co-extruded PVC profiles  54 . 
     To create the visual illusion of a single muntin profile, it is important that the dark colored foam tape  60  fully covers the light colored PVC channel  58  and also fully extends between the two flexible dark colored edge fins  59 . 
     FIG. 7 shows an elevational view of a triple glazing unit that simulates the appearance of a divided-lite window with an Austrian pattern, decorative border trim. The traditional Austrian pattern typically consists of a clear center glazing panel  62 , four colored corner panels  63  and four decorative edge, infill panels  64 . The three different panel areas are separated by a muntin profile grid  65  that consists of two vertical profiles  66  and two horizontal profiles  67 . 
     FIG. 8 shows a cross sectional, bottom edge detail of a triple glazing unit  47  that simulates the appearance of a simulated divided lite window featuring an Austrian pattern decorative border trim. The triple glazing unit  47  incorporates a center glazing flexible PET film  65 , with a pre-applied printed pattern. To provide a smooth, wrinkle-free surface, the flexible PET film is tensioned using either heat or cold tensioning processes. The flexible film  65  is held in tension at the perimeter edge by means of a composite edge-seal construction consisting of an insulating foam spacer  37 , a hollow steel spacer  67  and polyurethane thermoset sealant  68 . 
     The pre-applied printed pattern consists of a clear center panel  62 , colored corner panels (not shown), and translucent infill edge panels  64 . The center and infill edge panels  62  and  64  are separated by a dark opaque strip  66  and the different decorative opaque, colored, and translucent patterns are directly applied to the flexible film using conventional printing techniques. 
     Co-extruded PVC profiles  61  are adhered to the inner and outer glazing sheets  21  and  22  with dark adhesive foam tape  60  and the profiles are in coincidental alignment with the printed dark stripe  66 . When viewed at an oblique angle, because of the inner dark surfaces, a visual illusion is created of a single muntin profile. Instead of a flexible film for the center glazing pane, a rigid glass sheet can be substituted and to create the required decorative pattern, various pieces of decorative adhesive film can be laminated to the perimeter edge of the rigid sheet. 
     FIG. 9 shows a fragmentary perspective view of a triple glazing sheet  47  that simulates the appearance of a traditional divided-lite window and features wood muntin profiles  70  adhered to the glazing unit  47 . 
     A decorative grid pattern  55  is applied to the center glazing sheet and typically the decorative grid pattern consists of a series of vertical  49  and horizontal  51  dark stripes made from adhesive plastic film material. Solid wood profiles  70  and  71  are adhered to the external surfaces of the glazing sheets  21  and  22  and the profiles  70  and  71  are generally in coincidental alignment with the center grid pattern  55 . The profiles  70  and  71  are adhered to the glazing sheets  20  and  22  using dark shade adhesive foam tape and it is important that this foam tape fully extends across the bottom face of the wood profile. 
     When the composite muntin grid assembly is viewed at an oblique angle, the visual illusion is created of a traditional divided lite window. Although both profiles in FIG. 9 are made from wood, an alternative option is for the interior profile to be made from wood while the exterior profile that is exposed to the weather is made from a hollow aluminum extrusion.