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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to structure venting, in particular, to a flood vent that opens to permit the flow of water in or out of a structure, such a house or garage, when the water level rises thereby avoiding an excessive pressure differential to develop between the interior and exterior of the structure as well as damage or failure of the structure. 
         [0003]    2. Description of the Related Art 
         [0004]    To eliminate or at least reduce damage due to flooding, several building code entities as well as the federal government have developed rules and regulations requiring structures with enclosed spaces located below defined flood plain levels to include automatic equalization of interior and exterior hydrostatic pressure caused by floodwaters. The rules and regulations require structures to be designed and built to allow floodwaters to move in and out of a structure freely. The Federal Emergency Management Agency (FEMA) requires compliance with FEMA Technical Bulletin 1-93. Other governmental agencies required compliance with the International Building Code and/or ASME 24-05 and 24-98. 
         [0005]    A number of devices have been developed to reduce or eliminate the pressure differential that may develop between the interior and exterior of a structure. In 1935, Hodge developed and was issued in 1938, U.S. Pat. No. 2,105,735 for a device that would relieve pressure that may develop within a closed chamber. The device focused upon the release of gas pressure from within the structure but provided for no means to reduce the pressure differential that could develop when the internal pressure of the closed chamber was less than the surrounding pressure. In 1954, Wolverton filed an application for a double acting relief valve and was issued a U.S. Pat. No. 2,774,116 in 1956. Wolverton&#39;s double acting relief valve addressed the shortfall for Hodge&#39;s device by double hinging a plate mounted in a structure&#39;s door that would activate to equalize the pressure differential, if any, between a storm door and main door. The Wolverton device did not address the issues associated with pressure differentials created by floodwaters, nor did the Wolverton device address ventilation. 
         [0006]    In 1993, Wagedes filed an application for an improved louvered basement vent and was issued U.S. Pat. No. 5,293,920 in 1994. Wagedes&#39; improved louvered basement vent included a frame and a screened opening. The louvers could be held open by engaging louver detents against frame tabs. The louvers open automatically to relieve excessive pressure in the structure and would remain open if the louvers engaged the frame tabs. While the Wagedes improved louvered basement vent was screened—where the prior discussed patents were not, it was limited to addressing only one type of pressure differentials—namely over pressurization of the structure. Furthermore, the Wagedes improved louvered basement vent required human intervention to reset the louvers in a closed position if the detents were engaged. 
         [0007]    In 1994, Schedegger and others filed a patent application for a plastic foundation vent and were issued U.S. Pat. No. 5,487,701 in 1996. The Schedegger device is similar in construction to the Wagedes device, in that it comprised independent louvers that could be held in an open position as well as a screened opening. Like Wagedes&#39; device, Schedegger&#39;s device was limited to addressing only one type of pressure differential and required human intervention to release opened louvers. 
         [0008]    In 1999, Montgomery filed a patent application for a device and method for relieving flooding from an enclosed space. He was issued U.S. Pat. No. 5,944,445 in 1999. The Montgomery device includes a swinging door capable of swinging both in and out of the structure to permit tidal water flow in and out of the structure. The swinging door has a spring loaded hinge and is held in a closed position by a catch assembly. The catch assembly includes an adjustable screw, a catch spring, a ball bearing and threaded sleeve. The automatic opening of the device in response to floodwaters pressing against the door is a function of adjusting the catch assembly. Improper adjustment of the catch assembly could range from a premature door opening (by animals) to failure of the door to open. Furthermore the manufacturing and assembly of such a device require skilled labor. In the same year, Montgomery and other filed a patent application for a foundation flood gate with ventilation. U.S. Pat. No. 6,287,050 was issued in 2001 for the device. Like his previous device, the foundation flood gate with ventilation included a swinging door capable of swinging in both directions to allow water to flow in or out of the structure. Automatic activation of the door is performed by a catching assembly. The catching assembly included a float for sensing the level of the water and releasing the door when the level exceeds a preset height. Automatic opening of the door requires an intact and freely movable float within the device. While requiring fewer parts than his previous device, the catching assembly still requires skilled labor to manufacture and assemble. In 2001, Montgomery and others filed a similar application for a foundation flood gate with ventilation but the latch assembly senses fluid force acting upon the door rather than relying upon a float to sense water level. In 2002, the United States Patent and Trademark Office issued U.S. Pat. No. 6,485,231 for the device. The device included a latching assembly which requires skilled labor to manufacture and assemble for proper operation. 
         [0009]    Sprengle and other filed an application in 2002 for a flood gate for a door. In 2004, U.S. Pat. No. 6,692,187 was issued for the device. The Sprengle device incorporated both the pressure and float sensing features of Montgomery&#39;s devices and further allowed for the gate to be used in an overhead door application without the door automatically swinging open when the overhead door is opened. Like the Montgomery devices, the Sprengle device requires skilled labor to manufacture and assemble for proper operation. 
         [0010]    Finally, in 2007 Albanese was issued U.S. Pat. No. 7,270,498 for a flood vent which relies upon a door with floatation slideably mounted to a frame which automatically opens (or closes) based upon the level of the floodwaters. While Albanese reduces the number of moving parts and thereby reduces the need for skilled labor, the device still requires proper manufacturing tolerances and assembly to ensure free sliding movement of the door within its tracks. Furthermore the Albanese device has no means to automatically open in response to force upon the door. 
         [0011]    As can be seen above the need for a flood vent that can open automatically, provide ventilation, yet have a minimal number of moving parts is desirable. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention is directed to a flood vent  10  comprising a shuttered duct  15 , with an upper and lower region, formed in a housing  20  fixed in a structure, such as a house, building, wall, door or overhead door at an elevation above ground level. See  FIGS. 1 ,  4 , and  6 . A lower region of duct  15  is angled down between two degrees)(2°) and eight degrees (8°) from a horizontal plane to form a sill  28  that sheds water to an exterior of the structure. See  FIGS. 1 ,  4 , and  6 . The present flood vent  10  includes a shutter  30  which is pivotally fixed in duct  15 . Duct  15 , sill  28  and shutter  30  are configured to allow the unimpeded movement of floodwaters in and out of the structure, when present; and further deter animals from using the flood vent  10  as a passageway in and out of the structure. Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]    The present invention is further described in connection with the accompanying drawings, in which: 
           [0014]      FIG. 1  is an exploded isometric view of an embodiment of the flood vent. 
           [0015]      FIG. 2  is an isometric view of a hood for said flood vent. 
           [0016]      FIG. 3  is an isometric view of an embodiment of a flood vent shutter. 
           [0017]      FIG. 4  is an isometric view of an embodiment of a flood vent housing. 
           [0018]      FIG. 5  is an isometric detail view of another embodiment of a flood vent shutter. 
           [0019]      FIG. 6  is an isometric view of an embodiment of a flood vent. 
           [0020]      FIG. 7  is an isometric view of an embodiment of a flood vent. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0022]    Certain terminology will be used in the following description for convenience and reference only and not for purposes of limitation. For example, the words “rightwardly”, “leftwardly”, “upwardly” and “downwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the structure being referred to. This terminology includes these words, specifically mentioned derivatives thereof, and words of similar import. Furthermore, elements may be recited as being “coupled”; this terminology&#39;s use anticipates elements being connected together in such a way that there may be other components interstitially located between the specified elements, and that the elements may be connected in fixed or movable relation one to the other. Certain components may be described as being adjacent to one another. In these instances, it is expected that such a relationship so described shall be interpreted to mean that the components are located proximate to one another, by not necessarily in contact with each other. Normally there will be an absence of other components positioned there between, but this is not a requirement. Still further, some structural relationships or orientations may be designated with the word “substantially”. In those cases, it is meant that the relationship or orientation is as described, with allowances for variations that do not effect the cooperation of the so described component or components. 
         [0023]    The present flood vent  10  comprises a bezel  26  connected to two opposing walls  22 , an upper wall  22  and a sill  28  to form a duct  15  within a housing  20 . See  FIGS. 1 ,  4  and  6 . The flood vent  10  has an interior duct opening  17  on the inside of the structure and an exterior duct opening  19  on the outside of the structure. See  FIG. 4 . Duct  15  allows fluid communication between the interior and exterior of the structure when floodwaters rise above sill  28 . 
         [0024]    Bezel  26  surrounds a periphery of an exterior duct opening  19  and serves to attach housing  20  to structure by fasteners or adhesive. Housing  20  can have outer dimensions that correspond with the nominal dimensions of concrete masonry units (CMU). In a preferred embodiment, housing  20  has outer nominal dimensions that correspond to a CMU-8, namely eight inches (8″) high, sixteen inches (16″) long and eight (8″) wide (all nominal dimensions). Housing  20 , walls  22 , bezel  26 , and sill  28  can be constructed of materials such as metal, plastic, concrete, cement, composites or a combination thereof. 
         [0025]    A shutter  30  is pivotally fixed to an upper region of duct  15  so that shutter  30  is capable of swinging in two directions, namely in and out of the structure. It is contemplated that shutter  30  can move about a swing arc that can be approximately one hundred and sixty degrees)(160°) to approximately two hundred and twenty five degrees (225°). 
         [0026]    A lower region of shutter  30  is releasably coupled to a portion of sill  28  by a fin  50 . A coupling region is that portion of shutter  30  swing arc where fin  50  is in contact with a portion of sill  28 , at least one tab  40  fixed to and projecting away from sill  28 , or a combination of both. Movement of shutter  30  to, from or through a coupling region is hampered by the releasable coupling of shutter  30  to sill  28  by fin  50 . The presence of at least one tab  40  fixed to and projecting away from sill  28  hampers movement of shutter  30  to, from, or through a coupling region. The size of a coupling region varies with the width of fin  50 , angle of sill  28  and the presence of at least one tab  28 . It is contemplated in one embodiment, that when fin  50  is within a coupling region, shutter  50  is in a closed position that substantially obstructs duct  15  and deters animal use of flood vent  10  as a passage through the structure. Movement of shutter  30  about a swing arc can be in response to a floodwater pressure differential in or across duct  15 , movement of floodwater against shutter  30 , floatation of shutter  30 , or a combination thereof. 
         [0027]    Shutter  30  can be pivotally fixed to an upper region of duct  15  by a variety of pivoting mechanism known to those skilled in the art of flood vents. In a preferred embodiment, a pair of opposing pin holes  24  is formed in an upper region of shutter  30  to receive a corresponding pin  32  fixed and projecting away from an upper region of duct  15 . See  FIGS. 1 ,  3 ,  4 ,  5 , and  7 . This arrangement allows a shutter  30  to rotate freely about a substantially horizontal axis above sill  28 . 
         [0028]    Fin  50  can be fixed to shutter  30 , sill  28  or neither as set forth in the following descriptions. In a first embodiment, fasteners  07  fix fin  50  to a lower region of shutter  30  so that it projects away from a lower region of shutter  30 . See  FIGS. 1 and 3 . In such an embodiment, fin  50  can be fixed to a lower region of shutter  30  by fasteners  07  or slidably fixed to a lower region of shutter  30  by fasteners  07  passing through corresponding slots  52  formed in fin  50 . See  FIGS. 3 and 5 . As the reader can appreciate, a slideably fixation of fin  50  to a lower region of shutter  30  alters the coupling region without altering the width of fin  50 . In a preferred embodiment, at least one tab  40  is fixed to and projects away from sill  28  to releasably couple with fin  50  to hamper movement of shutter  30  to, from or through a closed position or a coupling region. See  FIGS. 1 and 4 . In a second embodiment, fin  50  is fixed to and extends away from sill  28  to releasably couple with a receiver  42  formed in a lower region of shutter  30 . See  FIGS. 6 and 7 . In such an embodiment, the size of a coupling region is a function of the cross sections of fin  50  and receiver  42  as well as the angle of sill  28 . In a third embodiment, fin  50  is releasably coupled to both shutter  30  and sill  28  by a first receiver  42  formed in a lower region of shutter  30  and a second receiver  42  formed in sill  28 . It is contemplated that such an embodiment would require a user to couple or re-couple shutter  30  with sill  28  after movement of shutter  30  beyond a coupling region. 
         [0029]    It is contemplated that duct  15  and shutter  30  can be circular, arcuate, polygonal or a combination thereof in shape when viewed from a duct opening  17  or  19 . 
         [0030]    In another embodiment, a plurality of holes  34  is formed in shutter  30  to allow movement of fluid through shutter  30 . Such holes  34  allow ventilation between the interior and exterior of the structure when shutter  30  is in a closed position. It is further contemplated that a hood  36  can be removably fixed to shutter  30  to impede the movement of fluid through shutter  30 . 
         [0031]    It is contemplated that shutter  30  and hood  36  can be constructed from metal, plastic, composites or a combination thereof. Furthermore, shutter  30  can be constructed with material(s) with a low density such that at least a portion of shutter  30  is buoyant in floodwater of a sufficient depth within said duct  15 . 
         [0032]    In any of the embodiments described above, the presence of a substantial amount of floodwater within at least a portion of duct  15  causes shutter  30  to move about its swing arc and allows the flow of floodwater between an interior and exterior of the structure. In the absence of a substantial amount of floodwater within duct  15 , shutter  30  is in a closed position or within a coupling region to substantially obstruct duct  15  and deter animal use of flood vent  10  as a passage through the structure. Finally, the number of parts used in the different embodiments of the present flood vent  10  is greatly reduced over existing devices which in turn reduces the cost of manufacturing and assembly. Likewise, the reduction in parts eliminates or reduces the likelihood of failure. 
         [0033]    A flood vent  10  and its components have been described herein. These and other variations, which will be appreciated by those skilled in the art, are within the intended scope of this invention as claimed below. As previously stated, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various forms.

Summary:
A flood vent is provided that allows the unimpeded flow of floodwater in a shuttered duct formed in a housing installed in a structure such as a building. A lower region of the duct is angled down between two and eight degrees from a horizontal plane to form a sill that sheds water to an exterior of the structure, and an upper region of the duct is pivotally fixed to a shutter positioned within the duct. The shutter is capable of swinging between a closed position and an open position in response to the presence of floodwater within at least a portion of the duct. Movement of the shutter to, from or through a closed position is hampered by a releasable coupling of the shutter to the sill by a fin.