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CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    Statement as to Rights to inventions made under Federally sponsored research and development: Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention. 
         [0003]    This present invention relates generally to shelters and to anchoring devices for shelters. 
         [0004]    2. Background Information. 
         [0005]    Temporary shelters are commonly used for recreation, community events as well as in emergencies. In emergencies it is desirable to be able to quickly erect shelters for a variety of purposes. Often emergency shelters are inflated on site. Inflatable shelters have the advantage of being quick to erect and do not require a separate heavy frame. Shelters with inflatable beams give shelter that is quick to erect, strong and that have a maximum area of covered space for the transportation weight. However, inflatable shelters do have problems. The light weight of the shelters gives a shelter that can move easily. One problem with inflatable shelters is that they tend to fill into the shape of a sphere or cylinder like a balloon. Such a shelter has a minimum of usable floor space. Even if heavy objects are placed on the floor of an inflatable shelter to hold the floor down, the upward force of the shelter combined with movement of people in the shelter can cause movement of even fairly heavy objects. Another problem with inflatable shelters is the need for destructive stakes. Stakes are used to tie the structure down to force the inflated structure to have a flat section of floor. This can require a tremendous amount of force and requires a very substantial staking process. Even when staked, there tends to still be unusable space near the walls where the floor still lifts up into a non-flat configuration. Another problem with inflatables is that they can be damaged during the inflation process when they are typically not yet tied down. If inflated on a parking lot, a wind can rake havoc. Another problem with existing inflatable shelters is that the movement of the floors and walls can cause motion sickness to those inside. To solve these problems, the prior art has used tie downs and stakes to secure temporary shelters. However, in emergency situations it is common to erect shelters on pavement such as in a parking lot or even inside a larger building such as a warehouse, gymnasium or sports stadium. In these cases driving stakes into concrete or other floor surfaces is destructive to the facility and also eliminates much of the benefit of an easy to erect building. 
         [0006]    A further problem with positively pressured inflatable structures is the tendency for an inflatable shelter to form rounded edges instead of square edges. This tends to yield a floor that does not lay flat all the way to the edges of the floor, rather the edges curl up and as a result usable floor area is reduced. There is often a trip hazard in doorways where the floor of the shelter tends to lift off the underlying surface. Personnel movement on lifted areas result in shelter motion. To correct this problem with the prior art, more staking has been used. To get a truly flat floor it is necessary to stake frequently around the entire perimeter of the structure which greatly increases the time and cost of installation as well as the destructive aspect to the existing concrete surface, floor or pavement. Stake loads increase dramatically with internal pressure on an inflatable shelter. Stresses in the shelter material increase dramatically as the floor/wall interface approaches a sharp corner. 
         [0007]    Accordingly, there is a need for an improved method and apparatus to affix a flexible fabric shelter to a surface. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention solves the problems outlined above. The invention anchors the shelter to the deployment surface by applying vacuum beneath the shelter floor causing atmospheric pressure bearing on the shelter floor to hold it against the deployment surface. 
         [0009]    In one aspect of the invention a shelter for use on a deployment surface has a flexible wall and a skirt surrounding the flexible wall and connected to a bottom edge of the wall. A source of vacuum supplied to a plurality of points beneath the skirt to hold the entire flexible skirt and the bottom edges of the wall flat on the surface. The atmosphere can exert a net hold down force upon the shelter being equal to the vacuum pressure multiplied by the shelter floor area. Additional features and benefits will become apparent from the detailed disclosure and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a view of the shelter; 
           [0011]      FIG. 2  shows details of the invention; 
           [0012]      FIG. 3  shows additional details of the invention; 
           [0013]      FIG. 4  shows details of the prior art; and 
           [0014]      FIG. 5  shows an alternate embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]      FIG. 1  illustrates a preferred embodiment of the shelter  100 . The shelter  100  is supported by air pressure in the shelter  100  such that the shelter  100  can be erected in the field simply by inflating the shelter  100 . The shelter could also be supported by positive pressure filling air beams  102  or alternatively the shelter could be supported by a frame. The shelter includes a flexible skirt  104  connects to the wall ( 120  in  FIG. 2 ) along the perimeter of the wall. A peripheral border having a width ‘W’ is formed around the interior portion of the shelter  100 . A source of vacuum  106  is supplied under the flexible sealing skirt  104 . The shelter  100  can include openings such as a door  110 . The source of vacuum  106  vacuums the flexible sealing skirt  104  down to a deployment surface ‘S’ that the shelter  100  is erected upon. The surface ‘S’ can be a concrete floor inside a building, asphalt, a wood floor or a composite gymnasium floor for example. The device has been tested and shown to be successful on concrete, asphalt, wood, or carpet surfaces. The system also works on other surfaces. The skirt  104  material is important. Some fabric materials are relatively rigid or stiff, these con be strong but will not conform to a deployment surface as well as a soft material that easily conforms to a surface. 
         [0016]      FIG. 2  shows a partial cross section of the shelter  100  revealing details of the invention. The shelter  100  includes a flexible wall  120  and a floor  130 . The wall  120  is connected to a skirt  104  that surrounds the floor  130  and living space within the shelter  100 . The shelter  100  sits on a deployment surface ‘S’ such as a floor or parking lot for example where the temporary shelter  100  might be required. Vacuum channel  140  propagates vacuum beneath the entire perimeter of the skirt  104 . The skirt  104  is sealed to the deployment surface S by the crushing force of atmospheric pressure. Additional seals  150  may be applied beneath the skirt  104  where discontinuities exist on the deployment surface S for example. Additional sealing may consist of compressible seal  150  for example and seal enabler  160 . The compressible seal  150  can be any light weight compressible material such as foam rubber. The auxiliary seal  160  can be any weight and could consist of sand or sand bags for example. 
         [0017]    The cross section of  FIG. 2  shows a vacuum channel  140  that carries the vacuum to areas covered by the skirt  104 . The skirt  104  can be sealed by a flexible seal  150  and an auxiliary seal enabler material  160  as an option to improve anchoring. The auxiliary seal enabler material  160  could be loose sand or sand bags stacked along the edge of the skirt  104  to improve sealing. When vacuum is applied, vacuum will communicate with the spiral openings  144  ( FIG. 3 ) in the channel  140  and the skirt  104  will pull down around the vacuum channel  140  and the seal  150 , which can be a flexible material such as a sponge like foam for example, will flatten. It will be understood by those in the art that the skirt can be attached to the floor surface of the shelter interior. It will also be understood that the vacuum could be applied under the floor of the shelter instead of using a perimeter skirt. The channel  140  could be a part of the skirt  104 , it is known to supply material that includes channels to communicate vacuum. 
         [0018]      FIG. 3  shows that the vacuum channel  140  receives vacuum source  142  connected to a source of vacuum  106 . The vacuum channel  140  propagates vacuum to the under surface of the skirt  104  which is shown partially cutaway in  FIG. 3 . The seal  150  is shown as it will appear when vacuum is applied, the skirt has wrapped tight around the vacuum channel  144 . The purpose of the vacuum channel  144  is to provide a conduit around the entire perimeter of the wall  120 . In this case the vacuum channel  140  is shown as a plastic spiral conduit material with openings  144 . The channel  140  provides a skeleton that will not collapse under the force of the vacuum and atmospheric pressure and yet allows is porous and allows a portion of the vacuum to be applied at regular intervals around the shelter perimeter. The spiral wrap shown has a diameter of about ½ inch and a wall thickness of about 1/16 th  inch and a 1/16 inch spiral opening at about ½ inch intervals over the entire length of material. When covered with the skirt  104  the vacuum channel  140  forms a vacuum conduit. 
         [0019]      FIG. 4  shows a portion of a prior art shelter  1000  including a door  1002  The shelter  1000  can have stakes  1006  at multiple points along its length to the surface ‘S’. The stakes  1006  can support ropes  1007  that exert tremendous pressure on the shelter  1000  to hold it in a near half cylinder shape against internal positive pressure. As can be seen, edges and corners  1008  still curl up off the deployment surface. Going inside the shelter  1000  and stepping on one of these corners  1008  will cause the entire shelter  1000  structure to move and will cause other parts of the shelter floor to lift up. The raised areas substantially reduce the useful area inside the prior art shelter  1000  and as can be seen can create walking problems such as the trip hazard at the door  1002  where the bottom of the door  1002  can be raised up off the ground. 
         [0020]      FIG. 5  shows an alternate embodiment of the shelter  200 . In this case a flexible wall  220  sits on top of a flexible skirt  230  that extends to both sides of the wall  220 . Vacuum is supplied through a channel  240  that runs along the length of the wall  220  just beneath the wall  220 . An optional seal  250  and  252  is provided on each side of the vacuum channel  240  and runs the length of the wall  220  and channel  240 . An additional seal enabler  260 ,  262  can be provided at the edge of or on top of the skirt  230  furthest removed from the wall  220 . The additional seal enabler  260 ,  262  might, for example be a material used to enhance the seal on rough concrete or grass for example. For example, the additional seal material could be a liquid material or sand or sand bags or gravel or dirt for example. Many materials would work. It will be understood that the wall  220  might separate the interior of a shelter from the exterior for example such that the vacuum is applied both under a skirt and a floor of the shelter  200 .  FIG. 5  also shows that the skirt  230  can have an optional seal formed by fabric overlap  270  formed along its length. It has been found that this overlap  270  can also help in forming the seal. 
         [0021]    It will be obvious to those skilled In the art that modifications may be made to the embodiments described above without departing from the scope of the invention. Thus the scope of the invention should be determined by the claims in the formal application and their legal equivalents, rather than by the examples given.

Summary:
An air supported positively pressurized flexible material shelter for use on a surface comprising a flexible wall and a skirt connected to the wall and surrounding the flexible wall. A source of vacuum being propagated beneath the skirt along the flexible wall, to vacuum the skirt down to the surface to secure the temporary shelter to the surface. The skirt forms a continuous connection with the surface around the entire perimeter of the shelter. An optional flexible seal is provided essentially parallel to a vacuum channel and on an exterior edge of the skirt spaced from the flexible wall.