Abstract:
A novel impact and blast resistant window is presented. A surface of a glazing pane has a durable transparent polymer film coated or adhered thereto. The surface of the window pane having the film is sealed to the sash by double sided tape. The resulting window produces an unexpected ability for the durable transparent polymer film to retain pieces of broken glass driven toward the interior of the building by a missile striking an exterior of the window, without the durable transparent polymer film pulling loose from the window sash.

Description:
[0001]    This application is a continuation in part of and claims priority of application Ser. No. 12/694,467, filed Jan. 27, 2010, which is a continuation in part and claims priority of application Ser. No. 12/217,425, filed Jul. 3, 2008, which is a continuation in part and claims priority of application Ser. No. 12/077,113, filed Mar. 17, 2008, which is a continuation in part and claims priority of application Ser. No. 12/070,687, filed Feb. 20, 2008, which is a continuation in part and claims priority of application Ser. No. 11/705,979, filed Feb. 13, 2007. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to windows, and more particularly to windows that are impact resistant. 
       BACKGROUND OF THE INVENTION 
       [0003]    Windows and glass panes in doors, panels and the like are a major source of unwanted heat loss and gain in a structure. With increased cost of fuel and energy, the moderation of unwanted energy losses on account of these structures has become of increasing importance. 
         [0004]    One method of reducing heat transfer through windows has been through the use of double glazed, and even triple glazed windows. Double glazed windows make use of two panes of glass that are attached together by a spacer. In some instances, the space between the two panes is hermetically sealed and can be filled with dry air, or with a dry inert gas such as argon or nitrogen. 
         [0005]    Although double glazing successfully reduces the energy transfer through a window, the use of two panes of glass substantially increases the weight of the window. Increased weight in windows is normally unwanted because of the need for heavier frames and sashes, heavier mounting hardware, and more rigid sash materials. Moreover, construction of double glazed windows is more complex than normal window construction, because the double glazed pane unit is constructed separately from the sash unit and then the sealed double glazed pane unit is mounted into the sash to assemble the insulated window. 
         [0006]    An alternative to the normal method of assembling a double glazed window makes use of a sash unit that has the spacer for the glazing panes formed integrally with the sash. This innovation avoids the separate construction of the sealed double glazed pane unit, because the panes are mounted into a sash that has been formed from sash elements that include the integral spacer. 
         [0007]    During the past several years, it has also become important to provide windows that are impact resistant. Many building codes, especially in areas that are at risk for hurricanes and major storms, now require impact resistant windows. In addition, blast resistance and shatter resistance has come to be important for windows in selected locations. A conventional method for the provision of impact and shatter resistance for windows has been the construction of safety glass. In this method of construction, a layer of durable transparent material, which may be a polymer, such as a polyurethane or polyvinyl butyral (PVB), is inserted between and adhered to two panes of glass to make a layered structure having glass on the outside and the polymer on the inside. Uvekol® may be used as the durable transparent material. When the window absorbs a blow that is powerful enough to break the glass, the presence of the durable polymer inhibits pieces of glass from flying in the direction of travel of the blow. 
         [0008]    However, in many cases, the pane of glass separates from the sash. As the pane of glass is shattered by a missile, it tends to separate from the sash. The now shattered pane of glass separates from the sashes and enters the structure in the direction of travel of the missile, creating a hazard. There is a need to reduce the tendency of the pane of glass to separate from the sash, and also to reduce the tendency of the pieces of shattered glass from separating. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is directed to a novel multiple glazed impact resistant window and a method of making the multiple glazed impact and blast resistant window. The method includes forming a window sash that delineates a mounting space for mounting a first pane and a second pane opposite and parallel to and spaced apart from each other. A durable transparent or translucent polymer film is attached to a surface of a glazing pane that is mounted in the window sash. The film inhibits pieces or shards of glass and missiles from entering the structure if the glass is broken by an impact or a blast. Double sided tape adheres the film to the window sash so that the film is inhibited from pulling away from the window sash during impact. The resulting window will pass applicable missile tests. The resulting window also provides additional security protection for the building in which it is installed, and for the building&#39;s inhabitants. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  shows a perspective view (C) of an embodiment of an impact resistant multipane window, such as a double glazed or triple glazed window, according to the present invention; and 
           [0011]      FIG. 2  shows a cross-section of an embodiment of a double glazed glass pane window with a protective layer of durable transparent or translucent polymer film on in accordance with the present invention, wherein the interior pane is fixed to the sash  16  with double sided tape that contacts a durable polymer film attached to the pane. 
           [0012]      FIG. 3  shows a cross-section of an embodiment of a triple glazed glass pane with a protective layer of durable transparent or translucent polymer film on in accordance with the present invention, wherein the interior pane is fixed to the sash  116  with double sided tape that contacts a durable polymer film attached to the pane. 
           [0013]      FIG. 4  illustrates a partial cross-section view of an embodiment of an impact resistant multipane insulating window of the present invention. 
           [0014]      FIG. 5  illustrates a partial cross-section view of another embodiment of an impact resistant multipane insulating window of the present invention. 
           [0015]      FIG. 6  shows a partial cross-section of an embodiment of an impact resistant multipane window of the present invention wherein the sash is a polymer extrusion having a stiffener and wherein the panes are sealed to the sealing surfaces of the integral spacer with glazing tape; optional snap-in glazing beads are omitted in this figure 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    In one embodiment of the present invention, a double glazed impact resistant window is produced by forming a window sash that delineates a mounting space for mounting a first pane and a second pane opposite and parallel to and spaced apart from each other.  FIG. 2 . The double glazed window has four window pane surfaces designated as 1, 2, 3 and 4, as shown in  FIG. 2 . One pane of the window is provided with a durable translucent or transparent polymer film on what is designated as surface four (4) of the glazing. The film can be formed by coating or adhering the durable transparent polymer film to surface four (4) of the pane. The film can be applied to the pane either before or after it is conformed to the size required for the mounting space. The first pane is mounted in the mounting space, and the second pane is mounted in the mounting space to form a double glazed impact resistant window. Double sided tape adheres the pane comprising surface 4 to the sash. 
         [0017]    In use, if a missile or similar object impacts the window, the glazing of the first pane  11  and the second pane  12  may be broken. The polymer film  10 , by being present on surface 4, acts as a “net” or barrier between the glazing and the interior of the building to inhibit debris from entering the building. The polymer film retains the shards and pieces of broken glazing material caused by missile impact. However, empirical observation teaches that the polymer film will pull away from the sash due to the energy applied to the polymer film from impact of the missile or similar object. Unexpectedly, the use of double sided tape  14 , with one side of the tape adhered to surface 4 and the opposite side of the tape adhered directly adjacent the sash as show in  FIG. 2 , materially retards the polymer film from pulling away from the sash, so that the polymer film retains the broken glazing and prevents broken glazing from entering the structure. The resulting window will pass current impact resistance testing for windows according to applicable building codes for ASTM E1886-02, ASTM E1996-03, and Wind Zone 3, small missile and large missile. 
         [0018]    The double sided tape  14  is adhered to the durable transparent film, which is adhered to the portions of surface 4 of the second pane that are in close proximity of the sash.  FIG. 2 . As shown in the drawing figure, the double sided tape is positioned within and relative to the sash so that it is not visible to the casual observer of the window. 
         [0019]      FIG. 3  shows a triple glazed window. The triple glazed window has six window pane surfaces, designated in  FIG. 3  as 1, 2, 3, 4, 5 and 6. If a missile or similar object impacts the window, the glazing of the first pane  111  the second pane  113  and the third pane  112  may be broken. The polymer film  110 , by being present on surface 6, acts as a “net” or barrier between the glazing and the interior of the building to inhibit debris from entering the building. The polymer film retains the shards and pieces of broken glazing material caused by missile impact. However, empirical observation teaches that the polymer film will pull away from the sash due to the energy applied to the polymer film from impact of the missile or similar object. Unexpectedly, the use of double sided tape  114 , with one side of the tape adhered to surface 6 and the opposite side of the tape adhered directly adjacent the sash as shown in  FIG. 3 , materially retards the polymer film from pulling away from the sash, so that the polymer film retains the broken glazing and prevents broken glazing from entering the structure. 
         [0020]    Double sided tape  114  is adhered to the durable transparent film, which is adhered to the portions of surface 6 of the interior pane that are in close proximity of the sash.  FIG. 3 . As shown in the drawing figure, the double sided tape is positioned within and relative to the sash so that it is not visible to the casual observer of the window. 
         [0021]    As used herein, the terms “directly adjacent the sash” means the side of the pane is abutting an inner edge of the sash, wherein the outer edge of the sash directly opposite the inner edge will form either the front or back side of the window sash. 
         [0022]    In an embodiment of the invention, the sash can be formed from extruded PVC members. The parts of the sash, commonly the top and bottom rails and the left and right stiles, can then be cut and assembled from the PVC extrusion to form one or more mounting spaces for panes. The sash may optionally include a spacer  18 , providing mounting surfaces for the panes. Surface 4 can be coated with the durable transparent polymer film anytime prior to assembly, and assembly can be completed by attaching double-sided glazing tape to the mounting surfaces and sealing the panes to the glazing tape. Snap-in glazing beads can be installed if desirable. 
         [0023]    When a polymer extrusion is used for the sash construction, the resulting window requires very little maintenance and is very resistant to environmental damage. 
         [0024]    As used herein, the term “window” means a sash with one or more transparent or translucent glazing panes that can be used to cover any opening in a structure. Commonly, a window is installed in a window frame. The term window includes all windows, such as single hung windows, double-hung windows, bay windows, bow windows, casement windows, fixed windows, and the like; door panels having transparent or translucent glazing; wall panels having transparent or translucent glazing; and similar structures. 
         [0025]    As used herein, the term “sash” means the framework that holds the glazing in a window. 
         [0026]    As used herein, the terms “mounting space” mean the space in a sash into which a glazing pane is to be mounted. Commonly the mounting space is delineated by the parts, or elements, of the sash, which are cut to the proper size that when attached together form a mounting space of approximately the same shape and slightly larger size than the glazing pane that is to be mounted therein. The mounting space can be of any shape and size, including round, oval, oblong, rectangular, square, triangular, pie-shaped, or of any other shape. Commonly, the mounting space is square, rectangular, or round. 
         [0027]    As used herein, the terms “sealing surface” mean a surface, such as a surface of a spacer or a surface of a sash against which the glazing pane is mounted. The sealing surface is commonly a flat surface that is parallel to the plane of the glazing pane. 
         [0028]    As used herein for double glazed windows, the first pane  11  is the pane closest to the exterior of the building in which the window is mounted, and the second pane  12  is the pane closest to the interior of the building in which the window is mounted. Surfaces 1, 2, 3 and 4 of the first and second panes, respectively, are as shown in  FIG. 2 . Surface 1 is on the first pane and is adjacent to the exterior of the building in which the window is mounted, and surface 2 is present on the first pane on an interior of the window adjacent to the spacing between panes. Surface 3 is present on the second pane and is adjacent to the spacing between panes. Surface 4 is present on the second pane and is adjacent to the interior of the building in which the window is located. 
         [0029]    As used herein for triple glazed windows, the first pane  111  is the pane closest to the exterior of the building in which the window is mounted, and the third pane  112  is the pane closest to the interior of the building in which the window is mounted. Surfaces 1, 2, 3, 4, 5 and 6 of the first, second and third panes, respectively, are as shown in  FIG. 3 . Surface 1 is on the first pane and is adjacent to the exterior of the building in which the window is mounted, and surface 2 is present on the first pane on an interior of the window adjacent to the spacing between panes. Surfaces 3 and 4 are present on the second pane and adjacent to the spacing between panes. Surfaces 5 and 6 are present on the third pane, and Surface 6 is adjacent to the interior of the building in which the window is located. 
         [0030]    In some embodiments, the present sash may be free of an integral spacer. 
         [0031]    As shown in  FIG. 2 , the first pane and the second pane of the double glazed window are spaced apart by a distance that is determined by the width of the sash or, where present, the spacer  18 . The glazing panes may comprise a first glazing pane  11  and a second glazing pane  12 , the second glazing pane having a durable transparent polymer film  10  attached to surface 4. Double sided tape  14  is used to further seal the second glazing pane to the sash, with the double sided tape adhered to the polymer film and to the sash. The first pane and the second pane may be attached to the sealing surfaces of the spacer by use of one or more sealants. 
         [0032]    The window may comprise a setting  20  block, a sash frame  22 , a glazing stop  24 , and panes formed of glass  26 . 
         [0033]    As shown in  FIG. 3 , the first pane, second pane and the third pane of the triple glazed window are spaced apart by a distance that is determined by the width of the sash or, where present, the spacer  118 . The glazing panes comprise a first glazing pane  111  and a second glazing pane  113 , and a third glazing pane  112 , the third glazing pane having a durable transparent polymer film  110  attached to surface 6. Double sided tape  114  is used to further seal the second glazing pane to the sash. The first pane and the second pane may be attached to the sealing surfaces of the spacer by use of one or more sealants. 
         [0034]    The window may comprise a setting  120  block, a sash frame  122 , a glazing stop  124 , and panes formed of glass  126 . 
         [0035]    In some embodiments, the enclosed space formed between glazing panes can be hermetically sealed from the surrounding atmosphere, and if desired, filled with a gas, such as dry air, or with an inert gas such as argon or nitrogen. In some embodiments, it is useful to provide a desiccant, such as sodium silicate, for example, (not shown in the figures) that is in communication with the enclosed space and is useful to absorb any moisture that may enter the enclosed space in order to avoid or reduce condensation. A desiccant is particular useful where film  210 ,  220  is applied to surface 2 and/or surface 3 ( FIG. 4 ,  FIG. 5 ,  FIG. 6 ) within the enclosed space, since the film tends to outgas, and a desiccant can reduce the harmful effects of outgassing. 
         [0036]    The glazing panes that are useful in the present invention can each separately comprise a material selected from the group consisting of glass, fiberglass and plastic. If plastic is used, it can be a polycarbonate, a polyurethane, LEXAN, Plexiglas, or the like. In some embodiments, it is preferred that the first pane and the second pane each comprise glass. The glass can be annealed glass, tempered glass, heat strengthened or untempered glass. Due to reduced cost, in some embodiments untempered glass is preferred for the glazing panes. The benefits of the present invention of improving impact, blast and shatter resistance are available for both double glazed and triple glazed windows. 
         [0037]    The durable transparent polymer film that is useful in the present invention can comprise any polymer, including polyamides, such as nylon; polyolefins such as polypropylene and polyethylene; polyester such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polyacetal; polycarbonate; copolyesters such as polyethylene terephthalate isophthalate; and the like. 
         [0038]    It is preferred that the durable transparent polymer film is at least translucent to visible light and may be transparent. In particular, it is preferred that the polymer film have a percent transmission of visible light of at least about 30%, at least about 40% is more preferred, at least about 50% is yet more preferred, at least about 60% is even more preferred, at least about 70% is yet more preferred, at least about 80% is even more preferred, and a visible light transmission of at least about 82% is yet more preferred. 
         [0039]    The polymer film should also be durable. When it is said that the polymer film is durable, it is meant that the polymer is one that has a tensile strength of at least about 15,000 psi, at least about 20,000 psi is more preferred, at least about 25,000 psi is even more preferred, and at least about 30,000 psi is yet more preferred. 
         [0040]    It is also preferred that the polymer film is one that has a break strength of at least about 50 lbs/in, and at least about 100 lbs/in is even more preferred, at least about 150 lbs/in is yet more preferred, and at least about 200 lbs/in is even more preferred. 
         [0041]    The polymer film can be single thickness, or it can be laminated. Laminated films of this type are described, for example, in U.S. Pat. No. 6,951,595. Films suitable for the present invention are available commercially from Madico, Inc., Woburn, Mass.; 3M, Minneapolis, Minn., and Mitsubishi Polyester Film, LLC, among others. 
         [0042]    The durable transparent polymer film of the present invention normally has a uniform thickness, which can be any thickness that is sufficient to provide the features required. Films that are useful in the present invention normally have a thickness within a range of about 0.25 mil to about 50 mil. A thickness from about 5 mil to about 30 mil is preferred, and a thickness of from about 8 mil to about 22 mil is more preferred. Generally, the larger the missile against which protection is desired, the thicker the material to be used. 
         [0043]    It may useful for the durable transparent polymer film to be supplied with, or to be prepared to have, a pressure sensitive adhesive on one side that is suitable for adhering the film to the pane. In particular, it is useful for the film to have a pressure sensitive adhesive suitable for forming a tight bond with a clean glass surface. The present polymer film can be provided with a hard coat, such as is described in U.S. Pat. No. 7,101,616, for example, or without such a hard coat. 
         [0044]    A preferred durable transparent polymer film is a three layer scratch resistant film having an acrylic adhesive coated on one side thereof for adhering the film to window glazing. The elongation/stretch characteristics of the film may be about 150% machine direction and 100% transverse direction. Tensile strength may be about 36,000 pounds per square inch of each layer. The layers may be formed of polyethylene terephthalate. 
         [0045]    The first pane  11 ,  111  and the second pane  12 ,  113 , and if used, the third pane,  112 , are spaced apart by a certain distance. The distance between the panes is determined by the distance between the sealing surfaces of the spacer  18 ,  118 , plus the thickness of the sealant that is used to adhere the panes to the integral spacer. Although the panes can be spaced apart by any distance that will provide the advantages of the invention, it is preferred that the first pane and the second pane are spaced apart by a distance of from about 6 mm to about 20 mm, a distance of from about 9 mm to about 16 mm is more preferred. 
         [0046]    The sash may be formed of any material that is conventionally used for the construction of window sashes. In embodiments of the present invention, the sash comprises a material that is selected from one or more of the group consisting of wood, metal and plastic. 
         [0047]    It has been found to be particularly useful for the sash to be formed from polymer extrusions.  FIG. 6 . Examples of extruded sash material are shown in U.S. Pat. Nos. 5,622,017 and 6,286,288, among others. Various types of extruded window and door sash material are available from Chelsea Building Products, Oakmont, Pa., and other manufacturers. 
         [0048]    Extruded sashes may be produced from any polymer, copolymer, or polymer blend that is suitable to provide the advantages of the invention. The polymer can be filled or unfilled. Examples of materials that are suitable for the production of polymer sash extrusions include polyvinyl chloride, polycarbonate, polyvinyl, and Extrudable Thermal Plastics available from Geon division of the B. F. Goodrich Co., as well as the materials described in U.S. Pat. Nos. 4,430,478 and 5,783,620, among others. 
         [0049]    When the sash material is a polymer extrusion, it is optional to include a metal, fiberglass or plastic stiffener, such as stiffener  601 . Such stiffeners are sometimes used when a long sash length is required, or when exceptionally heavy glass must be supported. One or more metal stiffeners can be used in a window sash. 
         [0050]    The first pane and the second pane and if used, the third pane, may be sealed to the sealing surfaces of the spacer, by the use of an additional sealant, since surface 6 will be secured to the sash by double sided tape in this embodiment. The sealant can be any material or device that is used to seal glazing panes to a window sash, and can be selected from glazing tape, silicone sealant, butyl sealant, or a combination of any two or more of these techniques. 
         [0051]    The double sided tape may be a polymer tape having pressure sensitive adhesive on both sides. Some tapes are formed from closed cell polyolefin foam with a glass adhesive on one side and a sash/frame adhesive on the other. See, e.g., Glazing Tape VG 100, or VG-300, available from Venture Tape, Rockland, Mass. Tape suitable for use in some embodiments of the present application is also available from Lamatek, Inc., West Deptford, N.J., and Press-On Tape and Gasket Corp., Addison, Ill. The preferred double sided tape is 3M brand VHB 4991, which is a general industrial tape formed of closed cell acrylic foam, having a thickness of about 2.3 mm, or an equivalent double sided tape, or a double sided acrylic foam tape from HI-BOND TAPES, INC., which may be VST 6200G. The acrylic foam tape should have a thickness of not less than 1.8 mm, and the thickness will usually be up to 3.0 mm. It is preferred to apply a primer prior to the mating surfaces when applying the double sided tape to optimize the holding power and achieve the goal of the invention of holding the broken or shattered glass within the film. 
         [0052]    While the use of double sided tape as described has been proven to meet the standards of missile tests as described, adhesives without a substrate and having similar properties may be used. The adhesive must be able to bond to the durable polymer film and the sash and hold the film during missile tests identified above, as well as cyclic static air pressure loading testing protocols, with at least the same degree of strength as the double sided tape. Materials such as SikaFlex or butyl adhesives may be useful. 
         [0053]    It is preferred to use double sided tapes having closed cell acrylic foam, such as 3M brand VHB 4991. One side of the tape adheres to the sash ( FIG. 2 ;  FIG. 3 ) or the spacer bar ( FIG. 4 ;  FIG. 5 ), and the other side adheres to the film. The foam allows limited movement of the film coated or covered glazing relative to the window sash, and absorbs energy, during missile impact. 
         [0054]    When the present window is assembled, the panes  11 ,  12  and the sash  16  provide an enclosed space that serves as an insulating feature of the window. In some embodiments, the enclosed space is hermetically sealed from the outside environment, and if desired, the gas in the enclosed space can be dry air, or can be an inert gas, such as argon or nitrogen. 
         [0055]    In order to minimize the moisture content of the gas in the enclosed space, a desiccant is optionally provided that is in contact with the enclosed space. The desiccant can be placed into an aperture of an extruded sash, if desired, so that it communicates with the gas in the enclosed space. 
         [0056]    The present invention encompasses a method of making a double glazed or triple glazed impact resistant window. The method comprises forming a window sash that delineates a mounting space for mounting a first pane and a second pane opposite and parallel to and spaced apart from each other. Optionally, a third pane may be mounted in a similar manner. The mounting space is typically formed by constructing a frame of sash members, often pieces cut to length from a long extrusion or molding, as described above, where the frame encloses a space that is slightly larger than and approximately the same shape as the pane that is to be mounted therein. The mounting space is bounded on each side by the sash  16  and on the surface to which the pane is to be mounted. The mounting space may be sized so that the pane will fit therein without touching any side of the mounting space, but will rest on all parts of the respective sealing surface. 
         [0057]    At an appropriate time during the fabrication process, the durable transparent polymer film  10  is adhered to a surface of a glazing pane, such as surface 4 of the second pane  12 , or the transparent polymer film  110  may be adhered to surface 6 of the triple glazed window, for example. The film can be adhered to a large piece of glass, and then the panes, with film attached, can be cut from the larger sheet to conform to the size and shape of the mounting space, or alternatively, the film can be adhered to the pane after the larger sheet has been cut to conform to a suitable size. The film may be attached to other surfaces, such as surfaces 2 and/or 3 of the double glazed window, and surfaces 2, 3, 4, and/or 5 of the single glazed window. 
         [0058]    The polymer film is commonly adhered to the pane by the use of a pressure sensitive adhesive that coats one side of the film and adheres tightly to the pane. When the film is obtained from a supplier, it optionally already has the adhesive applied to one side of the film, and provides a protective film, often silicone, over the adhesive. The protective film can be removed and the film can be adhered to the pane. 
         [0059]    When the panes are glass, it is preferred that the glass is very clean before the durable transparent polymer film is attached. Any small particle that is present on the glass when the film is applied will remain in the assembly forever, and can have a negative effect on the strength of adherence of the film to the glass (which may negatively affect the impact resistance of the window) and on the visual quality of the window. Accordingly, it is preferred that the glass is thoroughly cleaned prior to applying the film and that the assembly of the film to the glass be carried out in a clean atmosphere. 
         [0060]    In some embodiments, excess durable transparent polymer film may be present around the edges of the pane after the durable transparent polymer film has been adhered. In these embodiments, the method further includes trimming the excess durable transparent polymer film prior to the mounting step. The trimming can be done by any method known in the art. For example, in some embodiments, the trimming may be done with a blade, such as a knife or box cutter. In other embodiments, the trimming may be done with a laser or water jet. 
         [0061]    In further embodiments where the method includes trimming, the trimming of the excess durable transparent polymer film may be done such that the durable transparent polymer film edge is flush with the edge of either glass pane. In other embodiments where trimming is utilized, an amount of durable transparent polymer film may remain over the edge of the glass pane. In further embodiments where trimming is utilized, the trimming of the durable transparent polymer film may be done such that the film no longer covers the entire glass pane. It is preferred that the durable transparent polymer film cover the entire glass pane of surface 4, so that the durable transparent polymer film is properly bonded to the frame or sash, such as shown in  FIG. 2 , by the double sided tape. 
         [0062]    If trimming of the durable transparent polymer film is utilized, it may be done at any stage of the presently claimed method. In some embodiments, the trimming may be done before the protective layer is provided. In other embodiments, the trimming may be done after the protective layer is provided. In other embodiments, the trimming may be done before mounting the pane in the mounting space. In further embodiments, the trimming may be done after mounting the pane in the mounting space. 
         [0063]    In one embodiment, when film-coated panes of the proper size are prepared, the second pane is mounted in the mounting space with the film covered surface 4 of the pane  12  directly adjacent the sash  16 , which may be adjacent to the interior of the building.  FIG. 2 . The film  114  is similarly applied as shown in  FIG. 3 . 
         [0064]    The use of glazing tape as the sealant prevents or minimizes the amount of “squeeze up” of liquid or semi-liquid sealants into the viewing area of the mounting space. Because the enclosed space is essentially sealed as soon as both panes are mounted in the sash, any liquid or semi-liquid sealant that is squeezed up between the pane and the sealing surface into the viewing area of the mounting space cannot be removed. However, the use of glazing tape having a foam core substantially prevents such squeeze up, but provides a strong and durable bond between the pane and the sash. When glazing tape is used as the sealant, the step of mounting the pane in the sash involves adhering glazing tape to the sealing surface of the mounting space and contacting each pane with the tape so that the film-covered surface of the pane is facing the tape. In some embodiments, it is useful to supplement glazing tape with a deformable type sealant, such as a silicone sealant, in order to improve the integrity of the seal. 
         [0065]    A typical embodiment of a window of the present invention is shown in  FIG. 1 , where (C) shows a perspective view of a window having sashes  16  that have been assembled to form a frame that defines a mounting space, into which panes  11 ,  12  are mounted to form an impact resistant multipane window. 
         [0066]    A particular advantage of applying the film to surface 4 is that the film does not reduce the enclosed space between panes of glazing that acts as an insulator, including double or triple pane windows where the enclosed space is filled with a noble gas such as argon. Note that in the embodiments of  FIG. 4 ,  FIG. 5 , and  FIG. 6  the area of the enclosed space is reduced by the film or films on surface 2 and 3. Further energy improvement may be achieved by treatment of a layer of the laminated film with a thin layer of metal or metallic oxide, such as titanium dioxide, bronze, silver, or stainless steel. By treating the film, rather than the glazing itself, the film lends lend low-emissivity properties to the window without the requirement of maintaining an inventory of low-emissivity glass. 
         [0067]      FIG. 4 ,  FIG. 5 , and  FIG. 6  show partial cross-sectional views of embodiments of a double glazed impact resistant window of the present invention in which the sash  301  has an integral spacer  310  projecting therefrom. The integral spacer  310  provides a first sealing surface  311  and a second sealing surface  312 , for mounting glazing panes opposite to and parallel to each other and spaced apart by a distance that is determined by the width of the integral spacer. The glazing panes comprise a first glazing pane  101  and a second glazing pane  102 , each having a durable transparent polymer film  111  and  112  attached to the surface of the pane that faces the other pane. Each embodiment shown in  FIG. 4  and  FIG. 5  show glazing beads  501 ,  502  that optionally can be used to further seal the glazing panes onto the sash. In  FIG. 6 , the optional glazing beads are omitted. The optional glazing beads  501  and  502  can be pre-formed plastic snap-in type glazing beads, particularly when the sash  301  is an extruded member as shown in  FIG. 6 , or they can be formed from a silicone, butyl, or other sealant material, or both a snap-in glazing bead and a polymeric-type sealant can be used if desirable to form a hermetic seal for the enclosed space  201  and/or to more securely seal the pane into the sash. The first pane  101  and the second pane  102  are attached to the sealing surfaces  311  and  312  of the integral spacer  310  by a first sealant  401  and a second sealant  402 , or, as shown in  FIG. 5 , by a sealant  403  that is unitary: enclosing the spacer and forming sealing surfaces for both panes. 
         [0068]      FIG. 4 ,  FIG. 5 , and  FIG. 6  show an enclosed space  201  that is bounded by the spacer that is integral with the sash, the first pane, and the second pane. In some embodiments, the enclosed space can be hermetically sealed from the surrounding atmosphere, and if desired, it can be filled with a gas, such as dry air, or with an inert gas such as argon or nitrogen. 
         [0069]      FIG. 4 ,  FIG. 5 , and  FIG. 6  each show the first pane  101  and the second pane  102  each having a durable transparent polymer film  111  and  112 , respectively attached to the surface of the pane that faces the other pane. 
         [0070]    By locating the durable polymer film on the protected interior surfaces of the panes, in other words, on the surface of each pane that faces the other pane and that seals against the integral spacer of the sash, the free surface of each film is protected from any touch and retains its clear, unmarred visual qualities without the expense of applying a hard coat. 
         [0071]    The first pane  101  and the second pane  102  are spaced apart by a certain distance.  FIG. 4 ,  FIG. 5 , and  FIG. 6 . show the distance as L. The distance between the panes is determined by the distance between the sealing surfaces  311  and  312  of the integral spacer  310 , plus the thickness of the sealant  401  and  402  that is used to adhere the panes to the integral spacer. Although the panes can be spaced apart by any distance that will provide the advantages of the invention, it is preferred that the first pane and the second pane are spaced apart by a distance of from about 1 mm to about 20 mm, a distance of from about 6 mm to about 16 mm is more preferred, and a distance of from about 6 mm to about 12 mm is even more preferred. 
         [0072]    When the sash material is a polymer extrusion, it is optional to include a metal stiffener  601  as shown in  FIG. 6 . Such stiffeners are sometimes used when a long sash length is required, or when exceptionally heavy glass must be supported. One or more metal stiffeners can be used in a window sash. 
         [0073]      FIG. 6  illustrates the use of an extruded sash  301  in the present invention, and shows the inclusion of an optional metal stiffener  601 . The extruded sash  301  includes an integral spacer  310  having two sealing surfaces against which the first pane  101  and the second pane  102  are sealed. The distance between the sealing surface for the first pane and the sealing surface for the second pane determines the distance by which the first pane and the second pane are spaced apart. The panes each have a durable transparent polymer film  111  and  112  adhered to the surface of the pane that faces the other pane. Snap-in glazing beads are optionally useful for this embodiment and could be attached into snap-in glazing bead slots  511  and  512 , such glazing beads are not shown in  FIG. 6 . 
         [0074]      FIG. 4 ,  FIG. 5 , and  FIG. 6  indicate that the first pane  101  and the second pane  102  are sealed to the sealing surfaces  311  and  312  of the spacer  310  by the use of a sealant  401  and  402 , or  403 . The sealant can be any material or device that is used to seal glazing panes to a window sash, and can be selected from glazing tape, silicone sealant, butyl sealant, or a combination of any two or more of these techniques. As described herein, it is preferred to use glazing tape having closed cell acrylic foam as the sealant on any surface of the window glazing that is covered with film, with one side of the tape adhered to the spacer bar or sash and the opposite side adhered to the polymer film. 
         [0075]    If desired, optional glazing beads  501  and  502  can be used to finish the glazing. When the sash comprises a polymer extrusion, the glazing bead can be snap-in glazing bead. 
         [0076]    When a window is assembled, the glazing panes  102  and  103  and the spacer  310  provide an enclosed space  201  that serves as an insulating feature of the window. In some embodiments, the enclosed space  201  is hermetically sealed from the outside environment, and if desired, the gas in the enclosed space can be dry air, or can be an inert gas, such as argon or nitrogen. 
         [0077]    The mounting space is bounded on each side by the sash  301  and on the surface to which the pane is to be mounted by the sealing surface  311  or  312  of the integral spacer  310 . The mounting space is sized so that the pane  101  or  102  will fit therein without touching any side of the mounting space, but will rest on all parts of the respective sealing surface  311  or  312 . The spacing of the pane  101  or  102  from the sash  301  is shown in  FIGS. 4 ,  5 , and  6  and is useful to permit differential expansion of the sash and the pane without causing contact between the pane and the sash, other than at the sealing surface  311  or  312 . 
         [0078]    When film-coated panes of the proper size are prepared, the first pane  101  may be mounted in the mounting space with the film-covered surface of the pane facing the sealing surface  311  of the integral spacer  310 . This is then repeated for the second pane  102 . 
         [0079]    Glazing beads  501  and  502  can optionally be added to the window to finish the assembly if desired. 
         [0080]    In an embodiment of the invention, layers of the durable transparent polymer film is adhered to, or coated onto a pane in directions that are not parallel to one another. Without being bound by theory, the inventors believe that the impact resistance is achieved by adhering and/or coating at least two layers of the durable transparent polymer film onto in directions that are not parallel to one another. Such adherence or coating may result in at least some cross-linking between the layers, which may provide enhanced impact resistance over films that are adhered or coated in only one layer and/or are adhered or coated in more than one layer, but in which adjacent layers are parallel to one another. For example, a first layer may be adhered or coated in the machine direction (MD) and a second layer may be adhered or coated to the first layer in the transverse direction (TD). Alternatively, the first layer may be adhered or coated in the TD and the second layer may be adhered or coated in the MD. The layers of the durable polymer transparent film may be adhered or coated at any opposing angles to one another, as long as the at least two layers are not adhered or coated in directions parallel to one another. 
         [0081]    Similarly, more than two layers may be adhered or coated to a pane and to one another, as long as at least two of the layers are adhered or coated in directions that are not parallel to one another. For example, a first layer may be adhered or coated in the MD, a second layer may be adhered or coated in the TD, and a third layer may also be adhered or coated in the TD. In another embodiment, the first layer may be adhered or coated in the MD, the second layer may be adhered or coated in the MD, and a third layer may be adhered or coated in the TD. 
         [0082]    As used herein, the terms “in directions that are not parallel to one another” means the layers are adhered or coated at angles to one another of between about 5 degrees and about 175 degrees. By way of example, in some embodiments, the directions may be offset at angles between about 45 degrees, and about 135 degrees, in other embodiments, between about 75 degrees and about 105 degrees, and in some embodiments, the directions are at angles of about 90 degrees. 
         [0083]    The impact resistant multipane windows of the present invention can be mounted and used in any application in which conventional impact resistant and/or multipane windows are used. Commonly, the novel windows can be mounted in frames in structures such as residential or commercial buildings to serve as strong, energy conserving windows. The novel windows can be components of doors, panels, skylights, and any other similar application. Mounting and use of the present windows is similar to the methods that are well known and are used for conventional impact resistant and/or multipane windows. 
         [0084]    The present invention encompasses a further method of making a double glazed impact resistant window. The method comprises, in some embodiments, forming a window sash that delineates a mounting space for mounting a first pane and a second pane opposite and parallel to and spaced apart from each other, the sash having an integral spacer that forms a sealing surface of the mounting space for each pane; adhering a durable transparent polymer film to a surface of the first pane; attaching a protective layer to at least a portion of the durable transparent polymer film to protect the durable transparent polymer film from damage prior to assembling the double glazed impact resistant window; conforming the pane to the size and shape of the mounting space; removing the protective layer; mounting the first pane in the mounting space with the film covered surface of the pane facing the sealing surface of the integral spacer; and repeating the previous steps for the second pane. 
         [0085]    The impact resistant multipane windows of the present invention can be mounted and used in any application in which conventional impact resistant and/or multipane windows are used. Commonly, the novel windows can be mounted in frames in structures such as residential or commercial buildings to serve as strong, energy conserving windows. The novel windows can be components of doors, panels, skylights, and any other similar application. Mounting and use of the present windows is similar to the methods that are well known and are used for conventional impact resistant and/or multipane windows. 
         [0086]    Other embodiments within the scope of the claims herein will be apparent to one skilled in the art from consideration of the specification or practice of the invention as disclosed herein. It is intended that the specification be considered to be exemplary only, with the scope and spirit of the invention being indicated by the claims. 
         [0087]    All references cited in this specification, including without limitation all papers, publications, patents, patent applications, presentations, texts, reports, manuscripts, brochures, books, Internet postings, journal articles, periodicals, and the like, are hereby incorporated by reference into this specification in their entireties. The discussion of the references herein is intended merely to summarize the assertions made by their authors and no admission is made that any reference constitutes prior art. Applicants reserve the right to challenge the accuracy and pertinency of the cited references. 
         [0088]    In view of the above, it will be seen that the several advantages of the invention are achieved and other advantageous results obtained. 
         [0089]    As various changes could be made in the above methods and compositions by those of ordinary skill in the art without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. In addition it should be understood that aspects of the various embodiments may be interchanged both in whole or in part.