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FIELD OF THE INVENTION 
     The present invention relates to shutters for use in buildings and, in particular, to inflatable shutters for protection of windows, doors and other exterior openings in a building. 
     Temporary shutters are commonly used to protect windows, doors, skylights, vents and other exterior openings in buildings from storm damage caused by high velocity winds and impacts from windborne debris. Conventional shutter systems include plywood panels and corrugated panels of steel, aluminum and plastic. The installation and removal of such conventional shutter systems is often labor intensive and may itself damage or mar the appearance of the building exterior. Plywood panels are typically nailed or screwed directly to the building structure. Installation of corrugated panels often involves the attachment of a rigid frame or other hardware to the building structure. In some cases, reinforcement bars may be required to hold the shutters in place. 
     Requirements for the protection of openings from hurricane damage are becoming more stringent. Different zones and ratings for temporary shutters have been designated by codes locally, nationally, and internationally. Each zone and rating has different standards and specification requirements. In Florida, for example, there are two zones, the HVHZ (High Velocity Hurricane Zone) and the NHVHZ (Non-High Velocity Hurricane Zone), each of these zones have distinct specifications under which the shutters must perform. 
     For example, in the NHVHZ, the shutter can deflect debris, even if it interferes with the window glazing (the glass or plastic portion of the window), so as long as the opening being protected is not compromised. Therefore, each shutter manufactured for use under a NHVHZ code district may be tested with, or without, any substructure and is found to pass the requirements as long as the shutter protects the opening completely by itself. That is, if the shutter protects the opening, with or without glass, the shutter passes the NHVHZ requirements. 
     In a HVHZ district, the shutter can not interfere with the window glazing. The HVHZ requirements were originally designated by Miami-Dade county in the 1990&#39;s after Hurricane Andrew caused severe structural damage and local building authorities were held, at least in part, accountable for the failure of the protective shutters. Dade county continues to maintain these requirements, even though from an engineering stand-point they make little sense. 
     In a HVHZ district, the most difficult test to meet is that the protective shutter cannot deflect debris into the opening that could cause damage to the window glazing. It is a well understood phenomena that deflection increases during a storm as pressure increases and the size of the opening sought to be protected increases. 
     Strong, lightweight products have been engineered, tested, and approved for areas covered by the NHVHZ regulations. Unfortunately, these same products fail to qualify in areas governed by HVHZ regulations because of how they deflect debris. To overcome this problem, shutters have been manufactured with a rigid framing. However, rigid framed shutters significantly increase the overall system&#39;s prices, as well as creating additional engineering problems. 
     Conventional shutters are heavy and cumbersome due to the size and weight of the materials utilized in their manufacture. Conventional shutters may weigh 50 lbs or more, making them difficult to handle during installation and removal, particularly when only one person is available for installation or removal. Furthermore, conventional shutters are bulky and require significant storage space when not in use. Thus, there is a need for an inflatable shutter that is simple to install and remove, is lightweight, and requires minimal storage space when not in use. 
     SUMMARY OF THE INVENTION 
     These needs and other needs are satisfied by the present invention, which comprises an inflatable shutter for covering an opening in a building structure. The inflatable shutter comprises a protective layer sized and shaped to cover the opening and at least one air bladder positioned between the protective layer and the building structure providing a protective cavity between the protective layer and the opening. 
     In an alternative embodiment, the inflatable shutter comprises a protective layer sized and shaped to cover the opening, at least one air bladder positioned between the protective layer and the building structure providing a protective cavity between the protective layer and the opening, and a fastener connected to the air bladder for mounting the shutter over the opening on the building structure. 
     In yet another alternative embodiment, the inflatable shutter comprises a protective layer sized and shaped to cover the opening, at least one air bladder positioned between the protective layer and the building structure providing a protective cavity between the protective layer and the opening, and a fastener connected to the protective layer for mounting the shutter over the opening on the building structure. 
     In yet another alternative embodiment, the inflatable shutter comprises two air bladders positioned along either the longitudinal edges or the horizontal edges of the building structure adjacent to the opening in the structure. 
     In yet another alternative embodiment, the inflatable shutter comprises a plurality of air bladders positioned along both the longitudinal and the horizontal edges of the building structure adjacent to the opening in the structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be explained in further detail by way of example only with reference to the accompanying figures, in which: 
         FIG. 1  is front section view of an inflatable shutter installed over an exterior window of a building; 
         FIG. 2  is a horizontal section view of the inflatable shutter of  FIG. 1 , taken across lines A-A; 
         FIG. 3  is a horizontal section view of the inflatable shutter of  FIG. 1 , showing unexpanded air bladders; 
         FIG. 4  is a horizontal section view of the inflatable shutter of  FIG. 1 , showing the inflatable shutter receiving wind pressure; 
         FIG. 5  is a detailed view of a fastener of the inflatable shutter of  FIGS. 1-4 ; 
         FIG. 6  is a horizontal section view of an alternative inflatable shutter installed over an exterior window of a building; 
         FIG. 7  is a detailed view of a fastener of the inflatable shutter of  FIG. 6 ; 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-4 , an inflatable shutter is shown installed by a fastener over the opening of a building structure. In the embodiment shown in  FIG. 1 , the inflatable shutter  2  is secured over a window  10  of a building structure  11 . Inflatable shutter  2  comprises a protective layer  4 , stretched over a plurality of air bladders  6 . Air bladders  6  abut building structure  11  on the longitudinal  13  and/or horizontal  15  edges of the structure, thereby providing a protective cavity  16  (shown in  FIG. 2 ) between protective layer  4  and window  10 . 
     Referring to  FIG. 1 , protective layer  4  of inflatable shutter  2  directly receives strong winds and windborne debris. Therefore, it must be dimensioned such that it covers the perimeter of window  10 , defined by a height  20  and length  22 . As a result, no part of window  10  is exposed. Although inflatable shutter  2  covers a window  10 , those of ordinary skill in the art will understand that such a shutter may also be useful over other openings, such as doorways and vents. 
     Protective layer  4  can be made of any suitable sheeting, woven or nonwoven fabric, composite, or other material known in the art capable of withstanding strong winds and windborne debris. Examples of such materials include Kevlar® and Nylon. Materials used in the construction of commercially available trampolines may also be utilized in the present invention (See, for example, denier polyester and PVC vinyl). The material should be provided with a weight and thickness sufficient to withstand high winds and windborne debris without breaking. Preferably, the material used to make protective layer  4  is translucent to allow light through window  10  when inflatable shutter  2  is in use. 
     The size and shapes of protective layer  4  can vary.  FIG. 1  shows a protective layer  4  of a hexagonal shape. However, different shapes and sizes may be used. Depending on the size and shape of the opening being covered by inflatable shutter  2 , it may be advantageous to deviate from the embodiment shown, such as by the use of a square or round protective layer. 
     Referring to  FIG. 2 , inflatable shutter  2  includes air bladders  6  which have inflatable air chambers  7 . Dependent on the size of the opening to be protected, inflatable shutter  2  comprises either a pair of air bladders  6  located on the longitudinal  13  or horizontal  15  edges of the structure  11  or multiple pairs of air bladders  6  located on both the longitudinal  13  and horizontal  15  edges of the structure. Air bladders  6  lie between protective layer  4  and building structure  11 , thereby providing a protective cavity  16  forming a distance  24  between protective layer  4  and window  10 . The size of protective cavity  16  is established based on the deflective and impact properties of the shutter  2 . Therefore, when air bladders  6  are inflated to form protective cavity  16 , inflatable shutter  2  does not deflect into the window glazing while the shutter protects window  10  from flying debris. Additionally, air bladders  6  absorb the impact of windborne debris during a storm and reduce the pressure applied to fasteners  9 , described below. 
     Air bladders  6  may be formed of any suitable flexible sheeting, woven or nonwoven fabric, composite, or other material known in the art capable of forming an airtight chamber. Rubber modified polypropylene is one example of such a material. Although protective layer  4  directly receives the winds and windborne debris, air bladders  6  should also be able to withstand high velocity winds and windborne debris without failing. 
     Inflatable shutter  2  is installed on a building structure  11  by fasteners  9 . Referring to  FIG. 5 , an embodiment is shown in which fasteners  9  comprise a receiving member  17  and an attachment member  18 . Receiving member  17  is mounted on building structure  11  and cooperates with attachment member  18  to secure inflatable shutter  2  to the building. In this embodiment, receiving member  17  is a ring, and attachment member  18  is a hook. In some situations, receiving member  17  may be unnecessary. One may prefer to simply attach attachment member  18  to an appendage of structure  11  rather than to a receiving member  17 , if such an appendage is available. Alternatively, instead of a ring and hook, one may desire to install bolts, clamps, latches, locks, buckles or any other suitable connection method known in the art to the building structure and/or the ends of the tethers so that the shutter may be quickly installed before a storm. 
     Referring to  FIGS. 6-7 , an alternative embodiment of an inflatable shutter  30  is shown in which each fastener  32  comprises a tether  34 , a receiving member  37 , an attachment member  38  and preferably a pressure relief section  39 . The main difference between this embodiment and the embodiment of  FIG. 5  is that, in this embodiment, tether  34  and pressure relief section  39  connect attachment member  38  to the rest of shutter  30 , rather than attachment member  38  being directly attached. The addition of tether  34  and pressure relief section  39  provide added support to shutter  30  to allow it to withstand increased amounts of wind pressure. Like the embodiment of  FIG. 5 , receiving member  37  is mounted on building structure  11  and cooperates with attachment member  38  to secure inflatable shutter  30  to the building. 
     Tethers  34  can be made of any suitable material strong enough to hold the shutter in place during periods of high velocity winds. In one embodiment, tethers  34  are cords made out of polypropylene fibers. Tethers  34  should be flexible, but at the same time should be stiff enough that shutter  30  resists separation from building structure  11  as it receives high velocity winds and windborne debris during a storm. 
     Pressure relief section  39  links tether  34  to attachment member  38 . In one embodiment, pressure relief section  39  is an elastic cord composed of one or more elastic strands forming a core, which are covered in a woven sheath of nylon or cotton. The elasticity of pressure relief section  39  allows it to absorb negative pressure during inflation of air bladders  36  without transferring direct pressure to attachment member  38 . As inflatable shutter  30  is installed, positive pressure will build up between the shutter and the building structure  11 . Pressure relief section  39  releases this pressure, as do the air bladders  36 . 
     Referring back to  FIGS. 2-4 , inflatable shutter  2  is preferably attached to building structure  11  by first attaching attachment member  18  to receiving member  17 , and then inflating the air bladders  6 .  FIG. 3  shows inflatable shutter  2  after attachment to building structure  11 , but before inflation of the air bladders  6 . At this stage in the installation, there is a distance  14  between inflatable shutter  2  and window  10 . Air bladders  6  are then inflated until protective cavity  16  of distance  24  is formed between shutter  2  and window  10 , as shown in  FIG. 2 . Referring to  FIG. 4 , as inflatable shutter  2  absorbs pressure from wind and windborne debris, air bladders  6  form an oblong shape and protective cavity  16  decreases to a distance  25  between shutter  2  and window  10 . By absorbing the wind pressure, air bladders  6  reduce the pressure applied to fasteners  9 . 
     Inflatable shutter  2  is preferably removed from a building structure after use by deflating air bladders  6  before fasteners  9  are unfastened. This removal method allows the tension in fasteners  9  to decrease before they are unfastened, thereby simplifying removal of inflatable shutter  2 . 
     Since shutter  2  is inflatable and does not contain a rigid frame, installation and subsequent storage of the shutter is relatively simple. When not in use, shutter  2  can be deflated and folded or rolled-up for compact storage. Then, when a storm approaches, shutter  2  can simply be unfolded or unrolled and installed. 
     Modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting on the scope of the invention.

Summary:
An inflatable shutter is provided. The shutter comprises a protective layer and at least one air bladder, and is attached to the outside of a building structure. The shutter is positioned outside the building structure adjacent a window or other opening in order to protect the window or other opening from high velocity winds and flying debris during storms. The shutter may be removed from the outside of the building and compactly stored during periods of nonuse.