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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to exhibition booths and, more particularly, to inflatable canvas tops for booths. 
     2. Description of Related Prior Art 
     State fairs, outdoor exhibitions, sporting events and the like, are usually populated by exhibitors exhibiting their wares for demonstration and/or sales purposes. Particularly at state fairs, such booths are used for games of skill and the like. Because such uses of the booths are temporary, ease of erection and dismantling is a requisite. Potential inclement weather and/or protection from the sun dictate that the framework includes supported elements for a cover. 
     Generally, the framework defines a width and depth equivalent to a square or rectangle as a function of the size of the booth. Usually four uprights are interconnected by rods at the top to provide stability and rigidity. To support a cover, orthogonally aligned diagonal cross-members interconnect opposing top corners of the framework and support at the center a vertical post. The cover may be pyramidal shaped supported at the top by the post extending upwardly from the cross-members extending between the uprights. The attachment of the cover to the rods may be via straps secured about the rods by snaps or various configurations of hook-and-loop fastening members, such as the type sold under the trademark VELCRO® (hook and loop fastener). 
     Except for coloring or graphic designs on the cover, there is little distinction between the covers of adjacent booths. Thus, the covers are seldom memorable to visitors at state fairs, exhibitions, or sporting events. 
     SUMMARY OF THE INVENTION 
     An inflatable canopy for mounting on a conventional framework for a booth includes an interior membrane and an exterior membrane. The interior membrane is generally of a pyramidal shape. However, the exterior membrane may be configured to replicate a unique configuration that is highly memorable and may be reflective of the purpose or function of the booth. A post extending upwardly from diagonal members secured to the framework supports the interior membrane and may also support the exterior membrane. The inflatable canopy includes a skirt detachably attached to rods extending between uprights of the framework to provide stability for the inflatable canopy and yet afford ease of mounting and demounting the canopy. A source of air under pressure, such as a conventional air pump, inflates the canopy and maintains it inflated during the period of use. 
     It is therefore a primary object of the present invention to provide a uniquely shaped canopy mountable on a framework for a booth. 
     Another object of the present invention is to provide an inflatable canopy for a booth used outdoors. 
     Yet another object of the present invention is to provide an easily mountable and demountable inflatable canopy for the framework of a booth. 
     Still another object of the present invention is to provide an inflatable canopy for a booth to insulate an interior membrane of the canopy from solar radiation. 
     A further object of the present invention is to provide a framework for a booth having support elements for supporting the interior and exterior membranes of an inflatable canopy. 
     A yet further object of the present invention is to provide an inflatable canopy for use with a conventional framework for a booth. 
     A still further object of the present invention is to provide an easily erectable and dismantleable inflatable canopy having a uniquely configured exterior membrane for use with the framework of a booth. 
     These and other objects of the present invention will become apparent to those skilled in the art as the description thereof proceeds. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described with greater specificity and clarity with reference to the following drawings, in which: 
         FIG. 1  illustrates an inflatable canopy supported upon the framework for a booth; 
         FIG. 2  is a detail view of the corner attachment of a skirt extending from the inflatable canopy; 
         FIG. 3  illustrates a post mounted adjustable strap for drawing down the corner of the skirt; 
         FIG. 4  is a detail view of the strap shown in  FIG. 3 ; 
         FIG. 5  is a side view of the inflatable canopy mounted on a framework and depicting the interior mechanical support and the interior membrane of the inflatable canopy; 
         FIG. 6  illustrates the basic components of the framework for supporting the inflatable canopy; 
         FIG. 7  illustrates a center post mounted bracket for supporting lights and other elements within the inflatable canopy; 
         FIG. 8  is a view of the interior membrane; 
         FIG. 9  is a cross-sectional view taken along lines  9 - 9 , as shown in  FIG. 8 ; 
         FIG. 10  illustrates a collar mounted on the interior membrane for engaging the central post; 
         FIG. 11  is a view looking upwardly toward the inflatable canopy; 
         FIG. 12  illustrates a representative air pump and mounting therefor; 
         FIG. 13  illustrates the inlet for inflating the inflatable canopy; 
         FIG. 14  is an end view taken along lines  14 - 14 , as shown in  FIG. 13 ; 
         FIG. 15  is a view of the underside of the inflatable canopy showing optional access slots; 
         FIG. 16  illustrates a zipper closeable access slot and a cover therefor to reduce air leakage; and 
         FIG. 17  is a side view of the slot, zipper and cover shown in  FIG. 16 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Vendors at state fairs, exhibitions and promotions generally display their wares or advertise their services under framework supported canopies. Additionally, and more particularly at state fairs, various entities provide games of skill under framework supported canopies. Generally, the canopies are pyramid-like configurations supported upon four posts or uprights. The footprint for the framework may be square or rectangular depending upon the size and configuration sought to provide sufficient space for the activity undertaken. The covers are generally of canvas or plastic supported upon a center post to provide a pyramidal configuration. They are detachably attached to the framework to facilitate erection and dismantling. Additionally, the framework is of the knock-down type to facilitate erection and dismantling. Because the covers are generally of a single pyramidal configuration, there is little distinction between booths and the only distinguishing features that can be incorporated are either colors, patterns, or graphics. 
     Referring to  FIG. 1 , there is illustrated a framework  10  supporting a canopy  12 . The framework may include four stanchions or uprights  14 ,  16 ,  18  and  20 . A plate  22 ,  24 ,  26 ,  28  may be disposed at the lower end of each of uprights  14 ,  16 ,  18  and  20 , respectively, to prevent the uprights from sinking into the ground or surface  30 . Canopy  12  includes an exterior membrane  40  that may be pyramidal shaped, as illustrated. Alternatively, it can be of any configuration commensurate with the desires of a user. As illustrated, exterior membrane  40  may extend laterally in one or more directions to provide an overhang extending laterally from two or more pairs of adjacent uprights. A skirt  44  extends about the perimeter defined by uprights  14 ,  16 ,  18  and  20  to secure the canopy to framework  10 . As illustrated, a pennant  45  may be attached to a pole  46  extending upwardly from the exterior membrane. 
     Referring jointly to  FIGS. 2 ,  3  and  4 , apparatus for securing skirt  44  to each of the uprights will be described. The skirt includes four sections  50 ,  52 ,  54  and  56  extending downwardly from canopy  12 . For illustrative purposes, only upright  14  and the adjacent skirt sections will be described with respect to  FIGS. 2 ,  3  and  4 . It is to be understood that similar structure is present at each of the remaining uprights. A ring  60  is attached to a corner of section  56 ; a similar ring  62  is attached to the corner of section  50 . An adjustable strap  64  may include a hook  66  for engagement with an aperture  68  in upright  14  and a hook  70  for engagement with each of rings  60 ,  62 . The strap includes an adjustment mechanism  72  to draw rings  60 ,  62  downwardly and thereby secure sections  50 ,  56  of skirt  44  to upright  14 . A similar strap engages the corners of the pair of sections attendant each of the remaining uprights to secure canopy  12  and prevent disengagement of the canopy from framework  10 . 
     Referring jointly to  FIGS. 5 and 6 , further details attendant framework  10  and its support for canopy  12  will be described. The upper ends of pairs of uprights  14  and  16 ,  16  and  18 ,  18  and  20 ,  20  and  14 , are interconnected by rods  80 ,  82 ,  84 , and  86 , respectively. To render the frame rigid, diagonal cables  88  and  90  interconnect the upper ends of uprights  14  and  18 ,  16  and  20 , respectively. The tension exerted by these cables retains the box-like configuration of framework  10 , whether this configuration is square or rectangular. To support at least the interior membrane of canopy  12 , a post  92  is supported at the intersection of cables  88 ,  90  by inserting the cables in respective pairs of orthogonal slots at the lower end of the post. The post includes a pipe  94 , or the like, of a first diameter. A second pipe  96 , or the like, extends upwardly from pipe  94  and is of lesser diameter, as illustrated. A pole  46  (see  FIG. 1 ) may extend from pipe  96 . It is to be understood that pipes  94 ,  96  and pole  46  may be hollow or solid and each is of reduced diameter with respect to the lower one. A platform  100  is secured to one of the corners of framework  10 . As shown, the platform is supported by rods  82  and  84  and will be described in further detail below. 
     As particularly shown in  FIG. 5 , interior membrane  102  includes a ring  104  for penetrable engagement with pipe  96  and supported by end  106  of pipe  94 . Exterior membrane  40  may include a ring  108  penetrated by pole  46  and supported by end  110  of pipe  96  if the exterior membrane is to receive support from the post. 
       FIG. 7  illustrates pipes  94 ,  96  and pole  46  forming post  92 . As illustrated more clearly in this drawing, lower end  112  of pipe  94  includes two pairs of slots  114 ,  116  and  118 ,  120  (not shown), which pairs are diametrically opposed to engage cables  88 ,  90  (see  FIG. 6 ). A bracket  122  may be mounted on pipe  96  to position the bracket within the space defined by exterior membrane  40  and interior membrane  102 . The bracket includes two straps  124 ,  126  having semi-circular sections for jointly enveloping pipe  96 . Bolts  128 ,  130  and their corresponding nuts  132  secure the straps to one another and capture pipe  96  therebetween. The bracket may include a plurality of apertures  134  or the like for suspending lights or other elements therefrom and within the envelope defined by exterior membrane  40  and interior membrane  102 . 
     Referring jointly to  FIGS. 8 ,  9  and  10 , further details attendant supporting interior membrane  102  on pipe  94  will be described. The configuration of interior membrane  102  may be essentially pyramidal and formed by four essentially triangular sheets  140 ,  142 ,  144  and  146 . Ring  104  is attached at the apex of each of these sheets. 
     This ring, as shown in  FIGS. 5 and 8 , is formed by multiple elements, as will be described with respect to  FIGS. 9 and 10 . Ring  104  is formed by a first ring  150 , which may be metal and a second ring  152 , which also may be metal. An annular gasket  154  is disposed between first ring  150  and sheets  140 ,  142 ,  144  and  146 . A further annular gasket  156  is disposed between second ring  152  and sheets  140 ,  142 ,  144  and  146 . The tips at the apex of each of sheets  140 ,  142 ,  144  and  146  have been removed, which removal is essentially commensurate with the inner circumference of first and second rings  150 ,  152  to permit penetration therethrough of pipe  96 . The rings, annular gaskets, and sheets are clamped together through bolts  158 , washers  160 , and nuts  162 . As shown in  FIG. 10 , six nut and bolt combinations may be used to ensure that the ends of sheets  140 ,  142 ,  144  and  146  are firmly clamped therebetween and the gaskets ensure that there is minimal leakage of air intermediate the sheets and first ring  150 . 
     As shown in  FIG. 8 , interior membrane  102  includes an opening  164  for injecting air under pressure into the space intermediate exterior membrane  40  and interior membrane  102 . 
     The air pump and related structure for inflating envelope  210  (see  FIG. 5 ) defined by exterior membrane  40  and interior membrane  102  will be described with joint reference to  FIGS. 11 ,  12 ,  13  and  14 .  FIG. 11  is a bottom view of the canopy similar to the view shown in  FIG. 8  and corresponding elements will be identified by the same numerals. 
     Platform  100  will be described primarily with reference to  FIGS. 12 ,  13  and  14 . The platform includes channels  166 ,  168  for receiving and resting upon rods  84 ,  82 , respectively, and provide the requisite support for the platform. An air pump  170  is mounted on the platform and includes an exhaust port  172 . A source of electricity for the air pump is obtained through electrical conductor  174 . The tube  176  (see also opening  164  in  FIG. 8 ) is secured to sheet  140  of interior membrane  102  and extends downwardly to receive exhaust port  172 . A tie strap  178  may be used to secure tube  176  with the exhaust port to prevent leakage therebetween. As shown in  FIG. 13 , an electrical conductor  180  may extend through tube  176  to provide electrical power to any lights or other elements supported from bracket  122  (see  FIG. 7 ).  FIG. 14  illustrates inlet  182  for receiving exhaust port  172 . 
     Access to the envelope defined by exterior membrane  40  and interior membrane  102  may be provided by the zippered openings illustrated in  FIGS. 15 ,  16  and  17 . Again, common reference numerals will be used for elements previously described. Two access ports  190 ,  192  may be formed in interior membrane  102  to provide access to the interior and, more particularly, to any elements supported from bracket  122  within envelope  210 . Each access port includes a zipper  194  to open and close the inlet. To provide a relatively leak-free access port, a hinged cover  196  is pivotally attached to interior membrane  102  and of a width and length to overlie zipper  194 . Hook and loop fastening means, such as that sold under the trademark VELCRO® (hook and loop fastener), is employed to secure the cover to the interior membrane. For example, a strip  198  of loop fasteners may extend about the perimeter of zipper  194  and secured to interior membrane  102 . Similarly, a strip  200  of hook fasteners may be attached to cover  196  to mate with the loop fasteners strip. Thereby, cover  196  is retained adjacent interior membrane  102  to minimize air leakage through zipper  194 . To facilitate opening and closing of cover  196 , a tab  202  may extend from cover  196 . As shown, edge  204  of cover  196  may be sewn by threads  206  to interior membrane  102 . 
     After erection of framework  10 , canopy  12  is attached thereto and its interior membrane is supported at its center by post  92 . This post provides support for interior membrane  102  separate from any support for exterior membrane  40  and produces envelope  210  defining a space (see  FIG. 5 ). Depending on the configuration of exterior membrane  40  it may be self-supporting as a function of inflation of envelope  210  or may be configured to receive support from post  92  (as illustrated). Platform  100  and the associated air pump is mounted at one corner of framework  10 . Tube  176  extending from interior membrane  102  is brought into sealed engagement with exhaust port  172 . If lights or other elements are to be supported from bracket  122 , they may be mounted by access through access ports  190  and/or  192 . Electrical power for the lights or other elements is provided by electrical conductor  180  extending into envelope  210 . Upon energizing air pump  170 , the space within the envelope defined by exterior membrane  40  and interior membrane  102  will be pressurized to urge expansion of exterior membrane to its intended configuration. 
     As noted above, the configuration of the exterior membrane may be essentially pyramidal as illustrated and supported in part by post  92 . However, the exterior membrane does not have to be supported by a post or other structure as the pressure provided by the air pump will inflate the canopy and it will retain its pre-determined shape. It can be of any shape, such as a beer can, a cartoon figure, lettering, etc. Additionally, the exterior membrane may be colored to depict a design or graphics may be formed thereon. 
     While framework  10  has been described as defining a rectangular/square footprint, it may be of any shape; such as circular/semi-circular/oblong, etc. The shape of canopy  12  would be commensurate with that of the framework. 
     It is therefore apparent that not only does the framework and supported canopy provide shade and an enclosure suitable for its location, whether it be a state fair, exhibition or simply a display but it is also capable of having a visual impact due to the size and shape of the canopy that may be selected. Hence, it will draw attention much more effectively than a conventional framework mounted canopy.

Summary:
A framework of uprights interconnected by rods defines a rectangular area to support an inflatable canopy. The canopy includes an interior membrane and an exterior membrane to define an envelope. A skirt depending from the canopy is secured to the framework to retain the canopy in place. A framework mounted air pump provides a flow of air to inflate the envelope. A framework supported pole engages and supports at least the interior membrane.