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CROSS REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to portable structures and particularly multi-level portable structures. 
     2. Description of Related Art 
     Tents have been used for centuries as temporary shelters for travelers or for semi-permanent housing units in warmer climates. Tents have been designed in many styles and with many features. However, virtually all tents have been designed as single-story structures. This makes living in tents uncomfortable at best and miserable at worst. All sleeping, eating and cooking must be carried out at the same level. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is a large multi-level tent that has an interior divided into two levels. A platform system is included within the tent to divide it into the levels. The tent is built up around the platform. The tent has an outer covering made of canvas and a set of frame elements that make assembly of the tent easy. The tent is a ¾ sphere that is supported by shaped tubes, a set of braces, and a top band. 
     The platform is a combination of wood, metal and plastic. Polyvinylchloride (PVC) posts are used to secure the platform to the ground. They have an auger base to anchor then securely. Each post extend upward to the full desired height for a two level living space. Metal brackets are secured to the vertical posts at each floor location. These brackets hold 2×4 horizontal wooden frame members. The frame members are reinforced with additional wood framing, similar to deck construction. Each deck is then covered with plywood sheathing to form a “floor” surface. 
     After the platform is built, the tent is constructed around it. The tent has a number of lower frame elements, a number of vertical elements and a top ring. The lower frame elements are joined in a circle. The vertical elements are attached to the lower frame elements at the connection joints. These vertical elements are secured by the top ring to form a semi-spherical frame. This frame is covered by a canvas outer covering that is attached to all the tent frame elements. Stakes are used to secure the tent to the ground. The tent has openings for doors and ventilation. The top ring is also fitted with a cover to prevent water from entering the tent. 
     Once assembled, the structure has two living levels. The upper level can be used for sleeping and the lower level can be used for living. In this way, bedding and other supplies do not have to be moved or stored while doing different activities. 
     Thus, this tent system makes a comfortable long term camp for doing fieldwork of any kind. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial cut-away view of the tent showing the interior two-level platform in place. 
     FIG. 2 is a perspective view of the invention with the tent fully closed. 
     FIG. 3 is a detail view of a vertical support post, showing the auger base. 
     FIG. 3 a  is a detail view of the vertical support and auger base, showing a threaded connection. 
     FIG. 4 is a detail view of a vertical support post with the base plate, and corner brackets installed, and showing two 2×4 frame members in the lower corner bracket. 
     FIG. 4 b  is a detail of an alternative base plate connection. 
     FIG. 5 is a top view of a corner bracket. 
     FIG. 6 is a side view of a spacer portion of the corner brackets. 
     FIG. 7 is a perspective view of the corner brackets showing the 2×4 framing in place. 
     FIG. 8 is a top view of a platform showing the placement of the vertical posts, the corner brackets, the 2×4 framing and the plywood decking. 
     FIG. 9 is a detail view of the top ring showing four vertical elements in place. 
     FIG. 10 is a detail view of the lower frame members being temporarily assembled with the vertical elements. 
     FIG. 11 is a detail view showing the frame in place around the platform and the tent covering being installed. 
     FIG. 12 is a detail view showing the final assembly of the frame elements and the tent fabric. 
     FIG. 13 is a side view of a tent stake. 
     FIG. 14 is a detail view showing a stake being positioned in a lower frame element. 
     FIG. 15 is a side view of a vertical frame element. 
     FIG. 16 is a top view of a lower frame element. 
     FIG. 17 is an outside view of the first section of canvas covering. 
     FIG. 18 is an inside view of a typical section of canvas covering. 
     FIG. 19 is an inside view of the final canvas section. 
     FIG. 20 is a bottom view of the canvas top cap. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1, the tent  1  and platform  2  are shown. In the preferred embodiment, the tent has an overall diameter of 16 feet and a height of 10 feet. The internal platform is 12 feet long by 8 feet wide. The lower floor  3  of the platform is designed to lie about 1 foot above the ground. The upper floor  4  of the platform is designed to be five feet above the top of the lower floor  3 . 
     FIG. 2 shows the tent fully assembled and closed. The platform  2  is entirely within this tent structure. 
     The platform is installed using four vertical members  5 . FIG. 3 shows one form of the vertical members. Each vertical member has a number of components. The bottom  6  of each vertical member  5  has an auger portion  7 . This portion is used to screw the vertical member into the ground. In the preferred embodiment, the auger portion  7  is approximately 1 foot long. The vertical members are made of 4-inch pipe. In the preferred embodiment, the vertical members are made of schedule  40  Polyvinylchloride (PVC) pipe. A number of holes are drilled in this pipe. A lower set of holes  8  and an upper set of holes  9  are used to secure the floor brackets (discussed below). A center hole  10  is used to pass a rod through. The rod is used to help screw the vertical member into the ground. 
     FIG. 3 a  shows an alternative form of the vertical member  5  and auger portion  7 . Here, the vertical member and auger portion are made in two pieces. The auger portion has a set of female threads  7   b  and the vertical member  5  has a set of male threads  7   a.  In this way, the two parts can be installed separately. In this design, the center hole  10  is relocated to the auger portion  5  as shown. Four mounting holes  6   a  are provided around the perimeter of the lower portion of the vertical member  6  as shown. 
     FIG. 4 shows the vertical member  6  with a base plate  11  placed on the bottom. This plate covers the auger portion and provides some lateral stability for the vertical members. Two floor brackets  12  are used on each vertical member. The floor brackets are made of lightweight metal. Each floor bracket has two triangular mounting plates  13 . FIG. 5 shows a top view of one mounting plate  13 . The two plates  13  are separated by a spacer  14 . The spacer has a diameter slightly larger than the diameter of the vertical member. FIG. 6 shows the spacer  14 . Note too that the mounting plates have central holes  15  of the same size as the spacer. The spacer is designed to provide room for a standard 2×4 piece of dimensional lumber. The floor brackets are place over the top of the vertical member and are slid down until they align with the holes  8  or  9 . Once aligned with the proper sets of holes, the floor brackets are bolted to the vertical member using fasteners common to the art. 
     With the threaded auger and vertical members, the base plate  11  can be installed with a hole to allow the auger and vertical member to be screwed together. Alternatively, The base plate  11   a  of FIG. 4 b  may be used. Here, two wooden blocks  11   b  are attached to the base plate  11   a  as shown. The auger and vertical member fit over the blocks as shown. Once in place the auger and vertical member can be secured to the blocks using the mounting holes  10  for the auger and  6   b  for the vertical member  5 . In this way, it is possible to assemble the platform without the augers. 
     The platform requires four vertical members set in a rectangular pattern. Once the first vertical member is placed, the other members are positioned according to the steps discussed below. After the vertical members are in place, the horizontal framing can be added. This framing used standard 2×4 lumber. As shown in FIG. 5, the floor bracket plates have a number of holes  16  formed in them. These holes are used to secure the 2×4 lumber to the floor brackets. Nails or similar fasteners may be used to secure them in place. FIG. 7 shows how the 2×4s  20  and  21  are placed to align in the brackets without having to miter or cut the ends. 
     FIG. 8 shows the framework and the vertical members. The outer 2×4s,  20 ,  21 ,  22 , and  23  are placed as shown. Note how the holes  16  align with the 2×4s. Once the perimeter has been framed, addition joists  24  are placed within the frame as shown and secured with fasteners to the perimeter frame. The frame is then covered with plywood sheeting  25 . The plywood ends are notched to fit around the vertical members as shown. Typically, the plywood is cut prior to locating the unit in the field. 
     Both the lower and upper floors are built in the same manner. Once the platform is finished, the outer tent can be built. 
     The tent portion is assembled from a number of components. FIGS. 9-20 show the tent&#39;s structural components the tent framework components. The base of the tent is formed using a number of lower frame brace  30 . FIG. 16 shows a top view of a lower frame brace  30 . In the preferred embodiment,  10  of the braces  30  are used. Each frame brace  30  has a pair of eyebolts  31  secured in the ends of the brace  30  as shown. The brace is a square piece of wood. In the preferred embodiment, each brace is five feet long from eyebolt center to eyebolt center and made from 2×2 dimensional lumber. At the center of each brace is a hole  32 . The hole  32  is approximately ½-inch in diameter. However, the hole  32  can be any reasonable size. The holes  32  are used for stakes  34 , shown in FIG.  13 . FIG. 14 shows the placement of the stakes  34  in the holes  32 . This procedure is also described in more detail below. Finally, each brace  30  has a small strip of VELCRO  39 , a hook and loop fastener, attached to one side of the outer face of the brace as shown. 
     The tent frame has a number of bent poles  35 . The poles are shown in FIG.  15 . The poles may be made of 1-inch tubing, or may be lighter weight flexible tubing. The bent poles  35  are approximately 14 feet long. As discussed below, one end of the poles fits in the eyebolts  31  at the base of the tent. Two holes  36  are provided to secure the poles to the lower tent frame braces. This procedure is discussed below. The tops of the poles  35  have a hole  37  that is used to secure the pole into a band  40 , as shown in FIG.  15 . The band  40 , in the preferred embodiment is metal. The band  40  is approximately 2 feet long and 2 inches wide. A number of holes  41 , corresponding to the number of poles, are cut into the band as shown. The band is formed into a circle, as shown. The poles  35  pass through the holes  41 . Pins  42  are placed through the holes  37  to secure the tops of the poles within the band  40 . See FIG.  9 . 
     The tent material is made of canvas or other waterproof material. The tent wall  50  is made up of several tent panels  51 . The tent panels  51  have similar characteristics, except for the first and last panels. All the panels are sewn together except for the first and last panels, where one end of those panels are left open to allow the tent material to be placed over the frame. FIG. 17 shows the outer surface of the first panel  51   a  . This panel is generally shaped as shown. On the right side, a strip of VELCRO  52 , a hook and loop fastener is attached as shown. At the top, a second loop of VELCRO  53  is attached as shown. Two pairs of grommets  55  are placed at the bottom corners as shown. Finally, a number of ties  56  are placed on the right side of the first panel as shown. The second panel is then sewn to the left side of the first panel (from the perspective of the outside of the panel as shown in FIG.  17 ). FIG. 18 shows the inside face of the first panel  51   a  . This face has a strip of VELCRO  57  as shown. All of the remaining panels, with the exception of the last panel, have the same shape as the first panel. All the intermediate panels have a strip of VELCRO  53  secured to the outer face at the top and a second strip of VELCRO  57  at the bottom of the inner face. FIG. 19 shows the inner face of the last panel  51   b  . This panel is sewn to the last intermediate panel on one side  60 . On the other side, are strips of VELCRO  61  as shown. This panel has a small slit  62  cut into the outer edge as shown. Like the other panels, this panel also has the two pairs of grommets  55  and an outer strip of VELCRO  53 . 
     FIG. 20 is an inner view of a top cap  70  that is used to cover the ring  40 . The top cap  70  has a continuous strip of VELCRO  71  within the inner perimeter. This strip  71  engages with the VELCRO strips  53  at the top of the tent panels to seal the top of the tent. 
     Referring now to FIGS. 10-12, the tent and platform are installed as follows: first, find a level ground surface. Then position the first corner post and screw it into the ground to a one-foot depth. Use a level to make sure the post is plumb. Place a platform bracket on the post and measure for the second support post location. At that location, screw in the second post. Repeat this procedure for the remaining posts, placing the posts in a rectangular pattern. Once the posts are set and plumb, secure the platform brackets to the posts using screws, nuts, bolts or other common fasteners. Next, secure the vertical and horizontal 2×4 frame members for the lower platform, securing them to the platform brackets. Once these are secure, add joists at 16 inches on center. Next place a sheet of plywood on the lower platform and secure it to the framework. Then, install a second set of platform brackets at the top of the vertical 2×4 members. Repeat the placement of horizontal members and joists, cover the top platform with plywood, and secure it to the joists as before. FIG. 8 shows this assembly. 
     Once the platform is completed, place the tent braces in a circle. The diameter of the preferred embodiment is sixteen feet. The platform is in the center of the circle. Assemble four vertical tent tubes and the top band on the top platform. The tubes are positioned at 90-degree increments and are installed on the top band with hardware. See FIG.  10 . The bottom end of each tube is placed through two of the eyebolts found at the ends of the braces. In this way, the braces are interlocked with the tubes. Temporarily secure the tubes to the braces using a nail  100  as shown. This step is shown in FIG.  10 . Install the remaining braces using the same techniques. Tie the end of the first panel of rolled canvas tent material to the top band, the middle of one tube and the bottom of the same tube. See FIG.  11 . Proceed to unroll the canvas around the frame. At each tube position, replace the nail with a “U” bolt that is placed through grommets  55  in the canvas. As shown in FIG. 13, a “U” bolt  70  then passed through two holes  36  in the tube (one above the eyebolts  31  and one below). The “U” bolts are secured with nuts  75  and lock washers  75 . See FIG.  12 . The VELCRO strips  57  are secured to the VELCRO strips  39  on the frame braces, as each panel is unrolled. When the entire canvas is unrolled, the last panel is mated with the first panel using the VELCRO strips, as discussed above. Finally, the tent cap is secured over the ring to seal the tent and make it weather tight. 
     Once the canvas is secured to the frame, a stake is driven through holes in each of the braces to secure the tent to the ground. The tent is then ready to use. 
     The present disclosure should not be construed in any limited sense other than that limited by the scope of the claims having regard to the teachings herein and the prior art being apparent with the preferred form of the invention disclosed herein and which reveals details of structure of a preferred form necessary for a better understanding of the invention and may be subject to change by skilled persons within the scope of the invention without departing from the concept thereof.

Summary:
A large multi-level tent that has an interior divided into two levels. The tent is a ¾ sphere that is supported by shaped tubes, a set of braces, and a top band. The platform has polyvinylchloride (PVC) posts to secure the platform to the ground. Each post extends upward to the full desired height for a two level living space. Metal brackets are secured to the vertical posts at each floor location. These brackets hold 2×4 horizontal wooden frame members. The frame members are reinforced with additional wood framing, similar to deck construction. Each deck is then covered with plywood sheathing to form a “floor” surface. After the platform is built, the tent is constructed around it. The tent has frame, which is covered by a canvas outer covering that is attached to all the tent frame elements.