Abstract:
A wind shield is provided for a projection screen or imaging surface wherein a sheet of material is included behind the projection screen to reduce the impact of wind on the projection screen.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     None. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     FIELD OF THE INVENTION 
     This invention relates to inflatable devices that hold or include projection or imaging screens. 
     BACKGROUND OF THE INVENTION 
     Portable, temporary projection screens are known in the art. These screens can be quite large and are often used in outdoor environments. Therefore, the stability of the projection screen is important. 
     In an outdoor environment, the projection screen surface may billow outwardly or inwardly under the influence of wind. It is highly desirable for the screen projection surface to remain flat during use so that the projected images appearing on the screen are not distorted. Prior art screens typically secure the screen surface to the framework with a series of ties that serve to stretch the screen flat. However, for larger screens in particular, wind blowing toward the front of the screen can cause it to billow in like a sail. Wind blowing toward the back of the screen likewise can cause the screen to billow out. Such effects are undesirable for a projection screen. 
     Therefore, a need exists for a means of reducing the effects of wind on projection screens. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a wind shield for a projection screen held up by a framework that serves to reduce the effect of wind on the projection screen. The wind shield is a sheet of material of a similar size to the projection screen that is attached to the back of the framework behind the projection screen such that the wind shield forms a plane that is approximately parallel to the plane of the projection screen. 
     It is a further object of the invention to include a lower panel below the projection screen if a gap exists between the bottom of the projection screen and the lower portion of the framework. 
     It is a further object of the invention that the area contained within the framework, screen surface, and wind shield be partially airtight. 
     It is a further object of the invention that the wind shield be easily detached from the inflatable screen structure. 
     It is a further object of the invention that the wind shield be capable of serving as a projection screen. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1   a  depicts an example of a prior art inflatable structure with a projection screen. 
         FIG. 1   b  is a side view of a prior art inflatable structure under the influence of wind from the rear. 
         FIG. 1   c  is a cutaway view of a prior art inflatable structure under the influence of wind from the front. 
         FIG. 2  is a perspective view showing the front side of an embodiment of the invention. 
         FIG. 3  is a perspective view showing the rear side of an embodiment of the invention. 
         FIG. 4  is a cutaway view of an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1   a  shows an inflatable structure  1  for holding and mounting a projection screen  2  according to the prior art. The inflatable device  1  can be erected on a temporary basis, including in outdoor environments. The inflatable device  1  includes an inflatable framework  3  that can include a top  4 , bottom  5 , and side ( 6   a ,  6   b ) portions. A blower  7  is used to inflate the framework  3  and a series of guy wires (not shown) can be attached to the framework  3  in order to hold the framework  3  in place. The screen  2  is attached to the framework  3  by any suitable means that are designed to stretch the screen  2  and hold the screen  2  in a flat position. Once the framework  3  is fully inflated and secured, a movie, video, or other images can be displayed on the screen  2 . Other types of frameworks can be used to hold projection screens, such as aluminum frameworks. 
       FIG. 1   b  shows the prior art structure of  FIG. 1   a  under the influence of wind  8  blowing toward the back of the projection screen  2 , causing the screen  2  to billow outward (toward the audience). 
       FIG. 1   c  is a cutaway view of the prior art structure of  FIG. 1   a  under the influence of wind blowing toward the front of the projection screen  2 , causing the screen  2  to billow inward (away from the audience). The billowing of screen  2  in either direction is undesirable as it can cause distortion of images shown on the screen  2 . 
     A prior art strategy for reducing the effect of wind on screens is to stretch the screen and secure it tightly to the framework. However, screens and frameworks cannot be stretched so tightly that they distort or rip. Moreover, projection screens, especially larger projection screens, can catch wind so that they distort in shape, even when stretched as tightly as possible. 
       FIG. 2  depicts an embodiment of the present invention. The framework  30  of an inflatable structure  10  can be made of plastic vinyl material or other suitable material that can be sewn or heat welded together. The framework  30  is inflated using a blower  70  or other known method of inflation. Framework  30  comprises a top  40 , bottom  50 , and side ( 60   a ,  60   b ) portions. A screen  20  can be attached to framework  30  on a front side of the framework (the side from which images are viewed) and stretched flat. The screen can be attached with a suitable number of ties, which can consist of a series of bungee cords or ties stretched between rings or holes in the screen and grommets on the framework. A series of guy wires (not shown) can be attached to framework  30  in order to hold it in place during inflation and after inflation. If the projection screen  20  does not extend substantially down to the framework bottom  50 , a lower panel (not shown) can be added to cover the front of the framework  30 . Inflatable frameworks are common for use with temporary outdoor projection screens but other types of frameworks, such as aluminum frameworks, can be used with the present invention. 
       FIG. 3  is a rear view of the inflatable structure shown in  FIG. 2 . A wind shield  33  is attached to the rear side of the framework  30 . The wind shield  33  can be made of any suitable fabric and can be attached to the framework in a manner similar to that used for the screen  20  and preferably is attached to the framework in a manner such that a partially airtight seal is formed. A partially airtight attachment can be accomplished in any suitable manner, for example by having the shield be slightly larger than the opening of the framework and having the grommets positioned on the framework such that when the wind shield is stretched and attached to the framework there can be an area of snugly fitting overlap between the framework and the wind shield. 
     The wind shield  33  is preferably of a similar shape as screen  20  and of a similar size. Screen  20  is preferably attached to the front of the framework in a similar manner such that a partially airtight seal is formed between the screen  20  and the framework as well. 
     When in place, wind shield  33  serves to reduce the effects of wind on screen  20 . The effects of wind on screen  20  are reduced because wind shield  33  can serve to absorb much of the force exerted by the wind. As shown in  FIG. 4 , an area  34  exists between screen  20  and wind shield  33 . This gap  34  is preferably about the distance between the front of the framework  30  and the rear of the framework  30 . Wind blowing toward the rear of the screen  20  may be blocked by wind shield  33 , which diminishes the impact of such wind on screen  20 . In addition, wind blowing toward the front of screen  20  will not impact screen  20  as much as it otherwise would if a wind shield  33  were not in place because of the cushion of air formed within area  34  formed by screen  20 , framework  30  and wind shield  33 . Preferably, the area  34  within screen  20 , framework  30  and wind shield  33  is made partially airtight by the manner of attachment of wind shield  33  and screen  20  to framework  30  to enhance the effectiveness of the cushion of air in reducing the effect of wind blowing toward the front of the projection screen. Thus, when wind direction is from the rear of the framework the wind shield can absorb some of the impact of the wind. This shields the projection screen surface from distortion. When wind direction is from the front of the framework and presses against the projection screen surface, the air trapped between the screen surface, the framework and the wind shield forms a cushion of air that can serve to reduce distortion of the screen surface. In the event that the screen is sized such that a significant gap is left between the screen and the bottom of the framework, a panel of material can be added to allow area  34  to be partially airtight. 
     In another embodiment, the wind shield can also serve as a projection screen. In this way, either side of the inflatable structure can serve as the projection screen and the opposite side can serve as the wind shield, depending on current conditions. 
     In another embodiment, a wind shield of the invention can be included on an aluminum framework device in order to reduce the effects of wind on a projection screen attached to the framework.