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FIELD OF THE INVENTION 
     The present invention relates to shelters, such as tents and canopies, formed from flexible membranes. In particular, the present invention relates to an inflatable shelter that has few parts, that is simple to manufacture and that is to easy to set up and repair. 
     BACKGROUND OF THE INVENTION 
     Portable shelters, such as tents and canopies, are employed to provide cover and protection from the elements such as sun, rain and wind. Such portable shelters generally include a flexible lightweight membrane, such as canvas, which is supported by poles or inflated members. Although more easily erected as compared to pole supported shelters, inflatable shelters are typically more expensive to manufacture, are more subject to failure and are more difficult to repair. Conventional inflatable shelters utilize either a single extremely complex shaped inflatable member or multiple tubes that have axial ends that converge at the apex of the shelter or that overlap one another at the apex of the shelter. Shelters that employ a single inflatable member are extremely complex and difficult to manufacture. Moreover, once damaged, the entire shelter must be replaced. Shelters employing multiple tubes that have axial ends converging at the apex of the structure require a greater number of parts, are time consuming to assemble and are subject to leakage. Shelters employing multiple tubes that overlap one another at the apex of the structure result in the outer perimeter of the shelter being multi-tiered such that the shelter is difficult to cover with a fly. Moreover, such shelters are unattractive due to the outer surface discontinuity. 
     As a result, there is a continuing need for an inflatable structure or shelter that is easy to manufacture, requires fewer parts, is easy to assemble, is easily erected and is easily repaired. 
     SUMMARY OF THE INVENTION 
     The present invention provides an inflatable shelter that includes a flexible membrane, a first elongate inflatable tube supported by the flexible membrane and a second elongate inflatable tube supported by the flexible membrane. The first tube has first and second axial ends and a first intermediate portion between the first and second axial ends. The second tube has third and fourth axial ends and a second intermediate portion between the third and fourth axial ends. The first, second, third and fourth axial ends terminate in a plane. The first and second intermediate portions converge towards one another such that the first and second tubes form four legs supporting the membrane. 
     The present invention also provides for an inflatable shelter including a first sleeve defining a first lumen, a second sleeve defining a second lumen, a first inflatable tube received within the first lumen, and a second inflatable tube received within the second lumen. The first sleeve has first and second axial ends and a first intermediate portion between the first and second axial ends. The second sleeve has third and fourth axial ends and a second intermediate portion between the third and fourth axial ends. The first and second intermediate portions converge. The first and second lumens are separated by at least one divider panel extending parallel to the first and second lumens. 
     The present invention also provides an inflatable shelter including a plurality of sleeves defining a plurality of lumens, a plurality of wall panels coupled to and extending between the plurality of sleeves and a plurality of elongate inflatable tubes disposed within the plurality of sleeves, respectively. Each of the plurality of tubes are insertable into and removable from the plurality of sleeves such that each of the plurality of tubes may be replaced. 
     The present invention also provides a shelter shell for being supported by a plurality of inflatable tubes, whereby inflation of the tubes supports the shell. The shelter shell includes a plurality of sleeves providing a plurality of lumens configured to removably receive the plurality of inflatable tubes, respectively, and a plurality of wall panels coupled to and extending between the plurality of sleeves. Each of the sleeves is preferably air permeable and is configured to completely surround a circumference of the tube disposed therein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view schematically illustrating an inflatable shelter supported by a plurality of inflatable tubes in an inflated state. 
     FIG. 2 is a fragmentary perspective sectional view of the shelter of FIG. 1 taken along lines  2 — 2 . 
     FIG. 3 is a fragmentary sectional view of the shelter of FIG. 2 taken along lines  3 — 3 . 
     FIG. 4 is a sectional view of a first axial end of one of the inflatable tubes of FIG.  1 . 
     FIG. 5 is a sectional view of a second axial end of the inflatable tube of FIG.  4 . 
     FIG. 6 is a fragmentary top elevational view of an exemplary manifold and set of air lines of the shelter of FIG.  1 . 
     FIG. 7 is a side elevational view of the manifold of FIG. 6 with the air lines shown in section. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a perspective view schematically illustrating an inflatable shelter  10  in an inflated state. As shown by FIG. 1, shelter  10  generally includes cover or membrane  12 , inflatable tubes  14 ,  16 ,  18 , manifold  20 , inflation lines  24 ,  26 ,  28  and pump  30 . Membrane  12  comprises a flexible sheet or a series of sheets stitched, bonded or otherwise connected together to form sleeves  32  and panels  33 . Sleeves  32  comprise fabric tubes sized to receive inflatable tubes  14 ,  16  and  18 . Sleeves  32  extend between and are interconnected to panels  33 . Sleeves  32  provide a flexible and collapsible framework for panels  33  and the remainder of shelter  10 . Upon inflation of tubes  14 ,  16  and  18  within sleeves  32 , sleeves  32  rigidify to support panels  33 . 
     Panels  33  comprise single sheets which are stitched or otherwise affixed to and between sleeves  32 . Panels  33  provide a majority of the covering provided by shelter  10 . Panels  33  are preferably formed from a water resistant, yet breathable imperforate fabric. Alternatively, panels  33  may be at least partially formed from a perforated fabric. For example, when used as a tent shelter, panels  33  may include portions which are perforated to provide increased ventilation to the interior of shelter  10 . In such embodiments, imperforate or water resistant or panels may be additionally positioned over the perforated portions of panels  33  to prevent the ingress of water and moisture. In the exemplary embodiment, panels  33  are formed from a typical tent material having a relatively large degree of flexibility such as breathable nylon. 
     Tubes  14 ,  16  and  18  (schematically shown in FIG. 1) are substantially identical to one another and comprise individual inflatable members having axial ends  34 ,  36  and intermediate portions  38 . Axial ends  34  and  36  of each tube  14 ,  16 ,  18  terminate in a single plane  42 . Depending upon the particular application of shelter  10 , plane  42  will either extend along the ground or other surface supporting shelter  10  or will comprise a lower most extending portion of a roof or cover which is elevated above the ground by poles or additional inflatable structures. 
     As further shown by FIG. 1, each tube  14 ,  16 ,  18  extends along a generally arcuate path such that intermediate portions  38  converge towards one another above plane  42 . As a result, tubes  14 ,  16 ,  18 , upon being inflated, form a self-supporting framework which is stronger at the junctions of intermediate portions  38  to better carry loads placed upon shelter  10 . In addition, each individual tube  14 ,  16 ,  18  provides multiple legs of the framework. As a result, shelter  10  requires fewer parts, is less expensive to manufacture, is easier to assemble and is less prone to damage or leakage. 
     Manifold  20  directs pressurized air via inflation lines  24 ,  26 ,  28  to each of tubes  14 ,  16 ,  18  to inflate tubes  14 ,  16 ,  18 . Manifold  20  is configured to simultaneously inflate tubes  14 ,  16  and  18 . Alternatively, manifold  20  may be configured to provide selective and independent inflation of tubes  14 ,  16  and  18 . Although less desirable, manifold  20  may be omitted, whereby tubes  14 ,  16  and  18  would have to be individually inflated one at a time. 
     Pump  30  is conventionally known and provides pressurized air to manifold  20 . Pump  30  preferably comprises an electrically powered air pump. In the exemplary embodiment, pump  30  includes a conventionally known electrical connector  46  configured for being plugged into a conventional vehicle cigarette lighter  48 . As a result, shelter  10  may be easily inflated at a remote location where electrical outlets are not available by simply plugging pump  30  into cigarette lighter  48  of a vehicle. Alternatively, shelter  10  may be provided with other mechanisms for providing pressurized air to manifold  20  and tubes  14 ,  16  and  18 . For example, pump  30  may alternatively comprise a manually actuated air pump or an air compressor. 
     FIGS. 2 and 3 illustrate sleeves  32  of membrane  12  and intermediate portions  38  of tubes  14  and  16  in greater detail. FIG. 2 is a fragmentary perspective view of shelter  10  taken along lines  2 — 2  of FIG.  1 . FIG. 3 is a fragmentary sectional view of shelter  10  taken along lines  3 — 3  of FIG.  2 . As shown by FIGS. 2 and 3, sleeves  32  are generally tubular walls which define inner lumens  52  that receive tubes  14 ,  16  and  18  (shown in FIG.  1 ). Sleeves  32  are preferably formed from a non-stretchable material. In the exemplary embodiment, sleeves  32  are formed from sail cloth or Dacron. Each lumen  52  has a diameter less than or equal to the maximum diameter of each of tubes  14 ,  16 ,  18  when inflated. As a result, sleeves  32  prevent tubes  14 ,  16 ,  18 , which preferably comprise bladders, from being over-inflated. Sleeves  32  also protect tubes  14 ,  16  and  18  from abrasion and other damage. Moreover, because sleeves  32  are not required to be airtight, sleeves  32  are still functional despite minor abrasion and wear over time. When normally and safely inflated, tubes  14 ,  16  and  18  have maximum outer diameter greater than the inner diameter of sleeves  32 . Although not shown in a fully inflated state, tubes  14 ,  16  and  18 , upon being sufficiently inflated, expand against the tubular walls forming sleeves  32  to place sleeves  32  and panels  33  in tension for increased strength and load capacity. Although sleeves  32  are illustrated as being formed from fabric sheet sewn together and further sewn to panels  33  extending between sleeves  32 , sleeves  32  may alternatively be formed as part of a single fabric sheet or may be independently formed and secured to membrane  12  by various other attachment methods such as stitching, heat welding, adhesives or fasteners. Although less desirable, inflatable tubes  14 ,  16  and  18  may alternatively have a maximum outer diameter less than or substantially equal to the inner diameter of sleeves  32 , whereby the tubes, upon being inflated, support sleeves  32  and panels  33  without placing sleeves  32  and panels  33  in great tension. 
     As best shown by FIG. 3, sleeves  32  preferably include multiple branches or segments  56 . Each segment  56  extends between the junctions of intermediate portions  38  at which the segments  56  angle away from one another. For example, at the junction of intermediate portions  38  of tubes  14  and  16 , shelter  10  includes four sleeve segments  56   a ,  56   b ,  56   c  and  56   d . Sleeve segments  56   a  and  56   b  provide an elongate continuous lumen  52  which receives tube  14 . Sleeve segments  56   c  and  56   d  provide an elongate continuous lumen  52  which receives tube  16 . As shown by FIG. 3, segments  56   a ,  56   b ,  56   c  and  56   d  are interconnected with one another in a generally X-shaped configuration such that the continuous lumens  52  provided by segments  56   a ,  56   b  and segments  56   c  and  56   d  converge towards one another. As a result, intermediate portions  38  of tubes  14  and  16  converge towards one another. More importantly, segments  56   a  and  56   b  retain tube  14  along a non-linear axis while segments  56   c  and  56   d  retain tube  16  along a non-linear axis. As a result, tubes  14  and  16  may comprise inexpensive elongate linear bladders or tubes which are inserted through the sleeves prior to inflation. In addition, tubes  14  and  16  may be easily removed from sleeves  32  for replacement or repair. 
     As further shown by FIG. 3, sleeves  32  include a divider panel  60  extending between the lumens  52  provided by segments  56   a ,  56   b ,  56   c ,  56   d . Divider panel  60  preferably extends parallel or tangent to adjacent portions of tubes  14  and  16 . Divider panel  60  is preferably formed from the same material as that of sleeves  32  and membrane  12 . In particular, divider panel  60  is formed from a flexible sheet of material which is generally unstretchable. Alternatively, divider panel  60  may be formed from a variety of alternative materials. Divider panel  60  serves as a partition between the lumen  52  provided by segments  56   a ,  56   b  and the lumen provided by segments  56   c ,  56   d  to prevent over-inflation of either of tubes  14  and  16  while permitting tubes  14  and  16  to extend as close as possible to one another so as to produce a stronger, more rigid and more visually appealing junction. In addition, because tubes  14  and  16  extend adjacent one another in a side-by-side relationship without vertically overlapping one another, the outer perimeter of shelter  10  is cleaner such that supplemental covers such as flys may be more easily positioned over shelter  10 . Although sleeves  32  are illustrated as including a single divider panel  60  at the junction of segments  56   a ,  56   b ,  56   c  and  56   d , sleeves  32  may alternatively include more than one divider panel  60 . For example, segments  56   a ,  56   b  may be continuously joined and segments  56   c ,  56   d  may be continuously joined, wherein the wall joining segments  56   a ,  56   b  is fastened to the wall joining segments  56   c ,  56   d  such that the two walls partition the side-by-side lumens from one another. 
     FIGS. 4 and 5 illustrate opposite axial ends  34 ,  36  of tube  14  in greater detail. As shown by FIG. 4, axial end  34  of tube  14  is axially sealed by cap  62  but includes an inflation port  73  through which the interior  66  of tube  14  is inflated. As shown by FIG. 5, axial end  36  of tube  14  is completely sealed by cap  64 . In the exemplary embodiment, cap  62  generally includes plug  68 , closure  70  and fastener  72 . Plug  68  comprises a member having an outer diameter sized for being received in the axial end of tube  14 . Plug  68  defines inflation portion  64  and includes a nipple  77  adapted for being connected to inflation line  24 . 
     Closure  70  is a generally cup-shaped member having a bottom  74 , an annular portion  76  and a passage  78  through which inflation line  24  extends to be connected to nipple  77  of plug  68 . Annular portion  76  has an inner diameter greater than the outer diameter of tapered plug  68 . As shown by FIG. 4, annular portion  76  and plug  68  cooperate to capture the wall of tube  14  therebetween. In the exemplary embodiment, plug  68  is tapered so as to have an enlarged diameter at end  75  such that as plug  68  is drawn towards bottom  74  of closure  70 , tube  14  is compressed between plug  68  and annular portion  76 . As will be appreciated, annular portion  76  or both annular portion  76  and plug  68  may alternatively be tapered or otherwise provided with an enlarged diameter at one end such that tube  14  is compressed between plug  68  and annular portion  76  as plug  68  and closure  70  are drawn towards one another. 
     Fastener  72  interconnects plug  68  to closure and draws plug  68  towards closure  70 . Fastener  72  preferably comprises a threaded member which is threadably received within plug  68  and which upon being rotated draws plug  68  towards bottom  74 . 
     FIG. 5 illustrates axial end  36  of tube  14 . As shown by FIG. 5, axial end  36  includes cap  64 . Cap  64  is identical to cap  62  except that cap  64  includes plug  88  in lieu of plug  68  closure  90  including annular portion  96  in lieu of annular portion  76 . Plug  88  and closure  90  are identical to plug  68  and closure  70  except that plug  88  is generally imperforate so as to completely occlude the axial end of tube  14 . Annular portion  96  omits passage  78 . 
     As further shown by FIGS. 4 and 5, sleeve  32  receives axial ends  34  and  36  of tube  14  as well as a majority of closure  70 . Each end of sleeve  32  includes an end flap  92  which extends across axial ends of sleeve  32 . Each end flap  92  is preferably made of the same material as the remainder of sleeve  32  and is secured by stitching to the remainder of sleeve  32 . Each end flap  92  includes an opening  94  sized to enable tube  14  with either plug  68  and annular portion  76  or plug  88  and annular portion  96  to be inserted therethrough. During insertion, plug  68  and  88  and annular portion  76  and  96  are turned sideways. Once inserted plug  68 ,  88  and annular portion  76 ,  96  are reoriented to face bottom  74  with flap  92  captured between bottom  74  and annular portion  76  at end  34  or annular portion  96  at end  36 . As a result, as fastener  72  draws either plug  68  or  88  towards bottom  74 , fastener also secures flap  92  and sleeve  32  to closures  70  and  90 . End flaps  92  assist in maintaining the shape of sleeve  32  when tube  14  is fully inflated against sleeve  32  to place sleeve  32  in tension. End flaps  92  further prevent tube  14  from extending past the axial ends of sleeves  32  when fully inflated. 
     Overall, caps  62  and  64  enable shelter  10  to utilize elongate inflatable tubes or hoses having open axial ends. Consequently, the manufacture of shelter  10  is simpler and less expensive. Moreover, because caps  62  and  64  may be easily disconnected from tube  14 , caps  62  and  64  may be reused when tube  14  is replaced. Although not illustrated in detail, the axial ends  34  and  36  of tubes  16  and  18  are identical to the axial ends  34  and  36  of tube  14 , respectively. 
     FIGS. 6 and 7 illustrate an exemplary embodiment of manifold  20  and air supply lines  24 ,  26  and  28  in greater detail. As shown by FIGS. 6 and 7, manifold  20  generally includes housing  100 , valve actuator  102 , and connectors  104 . Housing  100  forms the main body of manifold  20  and defines an inlet port  106  and three outlet ports  108 ,  110  and  112  which communicate with an internally defined and conventionally known valve mechanism (not shown) situated between port  106  and ports  108 ,  110 ,  112 . Port  106  receives air intake line  31  extending from pump  30  (shown in FIG.  1 ). Ports  108 ,  110  and  112  provide openings by which air lines  24 ,  26  and  28  are connected. 
     Actuator  102  preferably comprises a large ergonomic knob connected to the internal valve. Rotation of actuator  102  about axis  116  moves the internal valve between a closed position in which pressurized air flowing through line  31  from pump  30  as indicated by arrow  118  is sealed or closed off from air lines  24 ,  26  and  28 , and an opened position in which air line  31  pneumatically communicates with each of air lines  24 ,  26  and  28  such that pressurized air provided by pump  30  through line  31  further flows through air lines  24 ,  26  and  28  as indicated by arrows  124 ,  126  and  128 , respectively, to simultaneously inflate each of tubes  14 ,  16  and  18 , respectively. Although actuator  102  and the internally formed, conventionally known valve are illustrated and described as being configured for providing the aforementioned closed and opened states wherein pressurized air is simultaneously supplied to each of air lines  24 ,  26  and  28 , actuator  102  and the internally formed valve may alternatively be configured, in a conventionally known manner, to have multiple positions wherein pressurized air may be supplied to air lines  24 ,  26  and  28  simultaneously as well as independently of one another. 
     As best shown by FIG. 7, housing  100  of manifold  20  preferably has a concave side  132  such that housing  100  conforms to the diameter of one of sleeves  32  when one of tubes  14 ,  16  or  18  is inflated. As a result, manifold is more visually appealing when positioned adjacent to shelter  10 . In addition, manifold  20  may be more easily secured and reliably mounted to shelter  20  by connectors  104 . 
     Connectors  104  secure manifold  20  to shelter  10 . At the same time, connectors  104  enable manifold  20  to be disconnected from shelter  10  such as when shelter  10  is being collapsed for storage or transportation or such as when either shelter  10  or manifold  20  requires repair or replacement. Connectors  104  preferably comprise conventionally known shock cords which are snapped inside housing  100 . As a result, connectors  104  releasably secure manifolds  20  to shelter  10  regardless of whether shelter  10  is in an inflated or a deflated state. Furthermore, because connectors  104  preferably comprise shock cords, connectors  104  reliably connect manifold  20  to shelter  10  without any rigid or sharp protruding edges which could puncture membrane  12  and without the need for rigid fasteners or other adhesives. Although less desirable, manifold  20  may be otherwise secured to shelter  10  utilizing adhesives, fasteners or other mounting mechanisms. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. The present invention described with reference to the preferred embodiments and set forth in the following claims is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the claims reciting a single particular element also encompass a plurality of such particular elements.

Summary:
An inflatable shelter includes a flexible membrane, a first elongate inflatable tube supported by the flexible membrane and a second elongated inflatable tube supported by the flexible membrane. The first tube has first and second axial ends and a first intermediate portion between the first and second axial ends. The second tube has third and fourth axial ends and a second intermediate portion between the third and fourth axial ends. The first, second, third and fourth axial ends terminate in a plane. The first and second intermediate portions converge towards one another such that the first and second tubes form four legs supporting the membrane. The flexible membrane preferably includes first and second sleeves defining first and second lumens receiving the first and second inflatable tubes, respectively, and a plurality of wall panels coupled to and extending between the first and second sleeves. The first and second lumens of the first and second sleeves are separated by at least one divider panel extending substantially parallel to the first and second tubes. The first and second tubes are insertable into and removable from the first and second sleeves, respectively, such that the first and second tubes are replaceable.