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BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates generally to methods for the manufacture of multiple-pane sealed glazing units and more particularly of units that incorporate decorative features that simulate the appearance of leaded or stained glass panels, and also to units products by such methods. 
     2. 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 the energy efficiency and condensation resistance of multiple-glazed sealed units. These improvements include: low-e coatings, argon or krypton gas fill, narrow width cavities and insulating spacing-and-desiccant systems for perimeter edge seals. 
     As noted in the U.S. Pat. No. 5,494,715, there is also a growing consumer interest in heritage window features with one popular feature being leaded or stained glass panels. Traditionally, these panels have been made by hand using grooved lead strips or cames. In the past because these handcrafted panels were very labor intensive to produce, various efforts have been made to simplify traditional production techniques and these efforts have been documented in the patent literature. 
     U.S. Pat. No. b  3 , 226 , 903  issued to Lillethun describes a triple-glazed sealed unit with a traditional stained-glass panel being incorporated as the center glass lite. 
     U.S. Pat. Nos. 4,335,170 and 4,438,165 issued to Butler describe a stained glass panel fabricated from a single glass pane where lead profiles are adhered in coincidental alignment to either side of a flat glass sheet. The extruded lead profiles are manually applied and are approximately 0.022 inches in thickness. Because of the stiffness and thickness of the lead profiles, the top lead profile has to be stretched and bent around the bottom lead profile and as a result, the process has to be carried out manually with each lead profile being individually applied. 
     U.S. Pat. No. 5,494,715 issued to Glover describes a triple pane unit with the center glass pane located only ⅛″ away from the front glass lite. To create the visual illusion of a solid lead came, three thin stripes are applied. One stripe is applied to the cavity face of the front glass sheet and the other two stripes are applied to either side of the center glass sheet. Traditional lead cames are grey in color, and if all three decorative stripes are colored grey, experience has shown that because of various optical and shadow effects, the visual illusion of a traditional leaded pane window is not always convincingly created. 
     For the triple stripe method described in U.S. Pat. No. 5,494,715, one key potential advantage is that the production process can be automated with the objective of producing over a 1000 decorative glass units per eight hour shift. However, the horizontal production equipment described involves glass sheets moving below a multi-head bridge assembly and no automated method or technique is given for applying the stripes to the opposite side of the glass. 
     SUMMARY OF THE INVENTION 
     The invention provides a method of applying decorative thin strips to a flat glazing sheet, said method comprising: applying a set of decorative thin strips on one side of a flat glazing surface; rotating said glazing sheet through a given angle and applying a second set of decorative thin strips at said given angle to first set of strips, said strips of the second set crossing and overlying said strips of the first set at points of intersection; wherein at least one of said sets of thin strips is applied in stages and each stage involves simultaneously applying two more thin strips. 
     The method may also include the further steps of flipping over the glass sheet and applying on the other side third and fourth sets of decorative thin strips in coincidental alignment with the thin strips of the first and second sets. 
     The given angle of intersection of the strips of different sets is chosen to suit the particular circumstances, e.g. at 90° where a rectilinear muntin bar appearance is to be achieved, or 60° where a diamond pattern is sought. 
     The strips can be applied with the glass sheet in a generally horizontal position, but preferably will be applied with the glass sheet in a generally upright position as providing a more convenient attitude in which the glass sheet can be flipped over or reversed, e.g. by the use of a turntable swivelling on a vertical axis, when the second side of the sheet is to be operated on. 
     The method described lends itself to automation through the use of air float/suction table surfaces to support the glass, and automatically guided and operated tape heads for applying tape to the glass to form the desired strip patterns. 
     From another aspect the invention provides a system of apparatus for carrying out the above discussed methods. 
     From another aspect the invention provides a sealed glazing unit that simulates the appearance of traditional metal came panels, said sealed glazing unit comprising: two or more parallel coextensive glazing sheets; peripheral seals extending continuously between the edges of said glazing sheets to define one or more glazing cavities between said sheets; decorative thin strips located on both flat surfaces of one of said glass sheets, said thin strips on respective surfaces being in mutually aligned registration with each other; wherein said decorative thin strips have one side that is of a relatively light shade and an opposite side that is of a relatively dark shade, said strips being attached to said glazing sheet in an orientation such that the side of relatively light shade is presented toward the adjacent exterior side of the glazing unit, whereas the side of relatively dark shade to is presented towards the interior side; wherein said strips are less than 0.005″ in thickness and arranged on each side of said one glass sheet in sets of parallel strips, said sets being arranged at a predetermined angle to each other to create a decorative grid pattern. 
     Where the strips are applied in the form of thin plastic strips with pressure sensitive adhesive securing them to the glass, then on each side of the glass the strips of one set overlap and overlie the strips of the other set at the points of intersection, the thickness of the strips being sufficiently small (less than 0.005″, and preferably about 0.002″) to enable this overlap to be accomplished without difficulty. 
     The plastic sheet material could conveniently be polyethylene terephthalate (PET), or the plastic tape could be made from a double lamination of plastic sheet material one side of which has a light shade and the other a dark shade. The light shade for example may simulate the appearance of lead or brass. 
     Alternatively the thin strips applied to the glass may be made of ceramic frit material which may be applied using heat release decals. 
    
    
     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 triple glazing unit that simulates the appearance of a leaded or stained glass window. 
     FIG. 2 shows an enlarged cross section detail of the triple glazing unit shown in FIG.  1  and featuring a double assembly of coated plastic film adhesive tapes on the center glass lite. 
     FIG. 3 shows an alternative cross section detail of the triple glazing is unit shown in FIG.  1  and featuring a double assembly of dual laminated plastic film adhesive tapes on the center glass lite. 
     FIG. 4 shows an alternative cross section detail of a double glazed glazing unit featuring a double assembly of dual-tone ceramic frit material on a single glass pane. 
     FIG. 5 shows plan views of the production steps for horizontal application of decorative adhesive tapes to one side of a glass sheet that is intended to be the center sheet of a stained or leaded glass panel. 
     FIG. 6 shows elevational views of the production steps for vertical application of decorative adhesive tapes to create a rectangular grid pattern. 
     FIG. 7 shows elevational views of the production steps for vertical application of decorative adhesive tapes to create a diamond grid pattern. 
     FIG. 8 shows a partial perspective view of an automated glass flipping station. 
     FIG. 9 shows plan views of the production steps for automated glass flipping. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a fragmentary perspective view of a triple glazing unit that simulates the appearance of a leaded or stained glass window. The glazing unit  20 , consists of three glazing sheets; an inner glazing sheet  21 , an outer glazing sheet  23 , and a center glazing sheet  22 . A vertical strip  25  of adhesive tape material  24  is applied to the inner surface  26  of said center glazing sheet  22 . 
     To create a grid pattern, horizontal strips  28  and  29  are applied at right angles to the vertical strip  25 . At the intersection points  33  and  34  between the vertical and horizontal stripes, the horizontal stripes  28  and  29  are simply laid on top of the vertical stripe  25 . 
     The adhesive tape material is typically made from a plastic sheet material with a pre-applied pressure sensitive adhesive. One preferred material option for the plastic sheet material is polyethylene terephthalate (PET) and one preferred material option for the pressure sensitive adhesive is acrylic. 
     The outer surface  30  of the tape is a relatively light shade while the inner adhesive surface  31  of the tape which contacts the glass is a relatively dark shade. For simulated leaded glass panels, the lighter shade is typically grey while the darker shade is black. For simulated brass came panels, the light shade is typically a metallized brass finish while the darker shade is black. 
     For ease of application, and so that there is no need to bend or stretch the tape at the intersection points  33  and  34 , the sheet material should be less than 0.005″ in thickness and preferably less than 0.002″ in thickness. 
     A second vertical strip  35  is applied to the outer surface  27  of the center glass sheet  22 . The second strip  35  is in coincidental alignment with the first strip  25 . Similarly, a second set of horizontal strips  34  and  32  are applied to the outer surface  27  of the center glass sheet. This second set of horizontal stripes are also in coincidental alignment with the first set. 
     FIG. 2 shows a cross section detail of a triple glazed unit  20  featuring a double assembly of coated plastic film adhesive tapes  37  and  36  on the center glass sheet  22 . The adhesive tapes are made from black PET sheet film material  38  with a pre-applied pressure sensitive acrylic adhesive  39 . The black PET features a UV stable, metallized coating  40 , with a shiny brass appearance. 
     FIG. 3 shows an alternative cross section detail of a triple-glazed unit  20  featuring a double assembly of dual-laminated plastic film adhesive tapes  41  and  42  on the center glass sheet  22 . The adhesive tapes  41  and  42  are made from a dual-lamination of PET sheet film material  43  and  44  and with a pre-applied pressure sensitive adhesive  39 . The PET film  43  adjacent to the glass sheet is typically colored black while the outer sheet  44  is a grey or yellow brass colored PET. 
     FIG. 4 shows a cross section detail of a double glazed unit that simulates the appearance of a leaded or stained glass window. The glazing unit  45  consists of two glazing sheets, an inner glazing sheet  21  and an outer glazing sheet  23 . Thin strips of ceramic material  46  are applied to either side of the inner glazing sheet. The ceramic material is a dark shade on the bottom surface  47  adjacent to said glazing sheet and a light shade on the top surface  48 . 
     The thin strips of ceramic material can be produced either by applying continuous strips of heat release decal transfers to create a grid pattern or by applying large heat release ceramic decals on either side of the glazing sheet  21 . 
     The large size decals incorporate a metal came design and may also incorporate decorative colored areas to simulate the appearance of traditional stained glass windows. After the decal transfers have been applied, the glass sheet is heated to a high temperature and the ceramic material is fused into the glass surface creating a very durable finish that does not degrade or color fade over time. 
     FIG. 5 shows plans views of the production steps for the horizontal application of decorative adhesive tapes  27  to one side of a center glazing sheet  23  that is stationary. 
     The first step is to transfer a glazing sheet  23  to a horizontal tape application table  50 . Key features of the tape application table include: a linear motion system  51 , two or more tape heads  52 ,  53  and an air float/suction surface  54 . The linear motion system  51  consists of a moveable rigid beam  55  that spans between a side activator  56  and a side guide rail  57 . The moveable rigid beam  55  incorporates a positioning rail  65  that allows the tape heads to be accurately positioned either by automated or manual means. The air float surface  54  is activated by a hip bar  58  operation and the glazing sheet  23  is moved into position and held against a popup stop  59 . Again through a hip bar  58  operation, the air flow for the air float surface  54  is reversed and the glass sheet  23  is held firmly in position through air suction. 
     By means of a foot pedal operation  60 , the linear motion system  51  is activated and the rigid beam  55  moves forward from its home position. Through optical sensors (not shown), the top edge  61  of the glazing sheet  23  is identified. 
     The tape heads  52  and  53  are then automatically activated and start to apply tape strips  62  at a specified distance from the top edge of the glass. As the rigid beam  55 , moves across the glazing sheet  23 , two or more adhesive tape strips are applied (See Step  2 ). 
     The bottom edge  63  of the glazing sheet  23  is identified again by means of optical sensors and the tape heads  52  and  53  are automatically deactivated at a specified distance from the bottom edge  63  of the glass sheet  23 . The moveable rigid beam  55  then automatically stops in position in front of the operator  64 . From computer-generated instructions, the operator  64  repositions the tape heads  52  and  53  using either automated or manual means (See Step  3 ). Through a foot pedal operation  60 , the moveable beam  55  is then activated and moves back to its original home position  65 . Depending on the complexity of the grid pattern, the process is again repeated and a further one or more strips are applied to the glazing sheet  23 . 
     When all the strips  62  have been applied in one direction, the air float surface  54  is activated to release the suction and provide an air float and the glazing sheet  23  is rotated through 90° (See Step  4 ). A series of strips  66  are then applied at right angles to the original set  62  (See Step  5 ). After the second set of strips  65  have been applied (See Step  6 ), the glazing sheet  23  is manually flipped and is again positioned against the pop-up stop  59 . A second grid pattern is then applied to the opposite side of the glazing sheet  23  and these strips are coincidentally aligned with the first grid pattern  67 . 
     FIG. 6 shows elevation views of the production steps for vertical application of decorative adhesive tapes  24  to create the rectangular grid pattern. 
     The first production step is to automatically transfer a clear glazing sheet  23  to a vertical tape application station  70 . Key features of the tape application station include: a linear motion system  51 , two or more tape heads  52 , 53  and  69  and a moveable rotating suction cup  71 . The linear motion system  51  consists of a moveable rigid beam  55  that spans between two side activators  56 . The moveable rigid beam  55  incorporates a positioning rail  58  that allows the tape heads  52 , 53  and  69  to be accurately positioned through automated means. 
     The air float surface  54  is automatically activated and a glazing sheet  23  is automatically transferred by means of a motorized wheel track system  72 . Through a system of electronic controls and sensors, the glazing sheet  23  is centrally positioned on a moveable rotating suction cup  71 . The wheel track system  72  is retracted and the suction cup  71  is automatically activated moving the glazing sheet  21  to a reference location  73  (See Step  2 ). The air flow to the air float surface  54  is deactivated and the glass sheet  23  is held firmly in position through both air suction and the moveable suction cup  71 . 
     The linear motion system  51  is then activated and the rigid beam  55  moves across the glazing sheet automatically applying two or more adhesive strips  62  to the glazing sheet  23  (See Step  3 ). As with horizontal tape application, the process is repeated until all the strips have been applied in one direction. The air float surface  54  is then activated and the glazing sheet  23  rotated through 90° by means of the moveable suction cup  71 . (See Step  4 ). A second set of strips  66  is then applied at right angles to the first set of strips  62  (See Step  5 ). The glass sheet  23  is again rotated so that the longest glass side is perpendicular to the moveable beam  55  and the glass sheet  23  is then repositioned on the wheel track system  72 . 
     FIG. 7 shows elevation views of the production steps for vertical tape application of decorative adhesive tapes to create a diamond grid pattern. As with the production of rectangular grids, the glazing sheet  23  is centered on a moveable suction cup  71 . The suction cup  71  is moved upwards to a reference location and the glass sheet  23  is rotated and positioned at a given angle to the moveable beam  55 . The air float surface  54  is deactivated and the glass sheet is firmly held in place by means of both air suction and the moveable suction cup  71 . The linear motion system is then activated and the rigid beam  55  moves across the glazing sheet automatically applying two or more adhesive strips  62  to the glazing sheet  23 . The process is repeated until all the strips have been applied in one direction. 
     The air float surface  54  is then activated and the glazing sheet is rotated through a given angle by means of the moveable suction cup  71 . A second set of stripes  66  are then applied at a given angle to first set of strips  62 . The glass sheet  21  is again rotated so that the longest glass side  73  is perpendicular to the moveable beam  55  and the glass sheet is repositioned on the wheel track system  72 . 
     FIG. 8 shows an elevation view of an automated vertical glass flipping station  75  that is used in combination with the automated vertical tape application station  70 . 
     After the first adhesive tape grid pattern  67  has been applied to one side of the glazing sheet, the glass sheet is then flipped over prior to application of a second tape grid pattern that is aligned with the first grid pattern. 
     One way of flipping over the glazing sheet is by means of an automated glass flipping station  75  that is similar in function to a traditional steam train turntable. Key features of the automated glass flipping station include: a transfer slot  77 , air floatisuction surfaces  78  and  79  on either side of the transfer slot  77 , a reversible wheel track system  81  and a motorized turn table  82 . 
     FIG. 9 shows plan views of the production steps for automated glass flipping. A glass sheet  23  is transferred to the slot  77  within the automated glass flipping station  75  by means of the motorized wheel track system  81 . Once fully enclosed within the slot  77 , the glass sheet  21  is automatically stopped. The air float surface on the slot face  78  is reversed and the glass sheet is firmly held in position by means of suction. The automated glass flipping station is turned through 180° about a vertical axis until the slot  77  is once more accurately aligned with the wheel track system  72 . The suction is slot face  78  is reversed and the drive direction of the wheel track system  81  is also reversed. 
     The glass sheet  23  exits the slot  77  and proceeds to a second automated tape application station  70  where a second adhesive tape grid is applied in coincidental alignment with the first grid pattern but on the opposite surface of the glass sheet.

Summary:
Simulated heritage windows e.g. in the appearance of leaded or stained glass panels are made by applying strips of material such as plastic tape in predetermined patterns on registering surfaces of the sheets which make up a double or triple glaze window. The strips can be applied in any desired pattern, e.g. rectilinear or diamond shaped and are applied in an automated manner by tape dispensing heads that are moved over the glass surface in parallel. The production system includes a conveyor for transporting the glass sheets as well as a rotary suction cup which grips the sheets and enables its rotation through e.g. 90° when a second set of strips is to be applied at right angles to the first strip. The apparatus also includes a turntable by means of which the glass sheet can be flipped over or inverted when strips are to be applied to both of its sides.