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[0001]    This application is a continuation of U.S. patent application Ser. No. 13/596,301, filed Aug. 28, 2012, the entire disclosure of which is incorporated herein by reference. 
     
    
       [0002]    The present invention relates to portable shelters, including lightweight tents, configured for heating, ventilation and/or air conditioning (HVAC). The shelters may be adapted for use in hot, remote locations, including but not limited to deserts and jungles. The shelters may also be used in cold climates with a heated interior. The remote locations at which the shelters may be constructed and operated with HVAC may be, for example, a mile or more from any well-maintained road or airport. 
         [0003]    Insulation systems that have been employed in prior art shelters are bulky, heavy and/or expensive. The present invention employs multi-layer fabric that is sufficiently lightweight to be easily transportable to a remote location, and sufficiently thermally-insulative to support efficient air conditioning (or other HVAC operations). The latter is especially important where the power source and/or fuel for the HVAC unit must itself be transported to the remote location. 
         [0004]    The disadvantages of the prior art can be overcome to a great extent by the present invention, which may be in the form of a portable shelter that has a lightweight, rigid support structure and a cover made of flexible, multi-layer, thermally-insulative fabric. According to a preferred embodiment of the invention, at least one of the outermost layers of the fabric blocks radiant thermal energy from being absorbed into the shelter in hot exterior temperatures and/or blocks thermal energy from escaping the shelter in cold exterior temperatures. 
         [0005]    According to a preferred embodiment, the flexible fabric does not rely solely on the density of an insulating material to decrease the mean free path by which photons can travel and radiate. Moreover, the fabric does not rely exclusively on eliminating convective air movement. That is, the fabric does not rely solely on the creation of air cells, pockets or tortuous pathways. 
         [0006]    According to the present invention, heat energy can be prevented from entering or escaping the system by a radiation barrier located among the outermost layers of the fabric. Most or all radiant thermal energy that would otherwise enter the shelter through the fabric is prevented from being absorbed by and passing through the fabric. In addition, layers for reducing heat convection and conduction may be provided to inhibit the transfer of any thermal energy that is absorbed (not reflected) by the outermost layer or layers. 
         [0007]    According to another aspect of the invention, an interior-facing portion of a vinyl layer is coated with a thin, metallized, protected surface. The vinyl layer may be the outermost layer of the multi-layer fabric. The resulting low emissivity (low c) vinyl allows for only a reduced amount of incident thermal radiation to pass through. Consequently, less heat energy is transmitted through the initial (outermost) layers of the shelter. Less heat energy is transferred to the anti-conductive/convective insulating layers, thereby eliminating or reducing the need for bulky batting to achieve the same degree of thermal protection. 
         [0008]    The invention may contribute to a lower air conditioning (or other HVAC) load for the shelter. The unique configuration of the improved shelter, with its low-emissivity (low c) multi-layer fabric, can provide energy savings that are equal to or greater than bulkier, more-expensive systems. 
         [0009]    The reduced weight and volume of the materials required for the total insulation package may enable a smaller and more convenient pack out for easier transportation, for example, by hand, by helicopter, or by air transport, and result in lower cost due to less use of material. For certain applications, if desired, the components of the shelter can be sufficiently lightweight to be easily stored and/or transported to a remote location. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]      FIG. 1  is a partially broken-away, perspective view of a shelter constructed in accordance with a preferred embodiment, showing the cover and the covered frame. 
           [0011]      FIG. 2  is a partial cross-sectional view of the cover of  FIG. 1 , taken along line II-II of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Turning now to the drawings, where like reference numerals designate like elements, there is shown in  FIG. 1  a portable shelter  10  that is constructed in accordance with a preferred embodiment of the present invention. The shelter  10  has a front wall  12 , a back wall (not shown), a roof  14 , and side walls  16 . The left side wall (not shown) is the mirror image of the right side wall  16 . The front and back walls  12 , the roof  14 , and the side walls  16  are supported by a suitable frame  18  made of lightweight aluminum (or steel) tubes, wooden poles, or the like. In an alternative embodiment, the frame for supporting the shelter may be formed by suitable inflated air beams, or by a suitable combination of air beams and metal or wood support devices. The present invention should not be limited to the exemplary configurations and structures described herein, except as provided for in the appended claims. Depending on expected wind and other conditions, the shelter  10  may be tied down by wires or ropes, stakes, or the like. 
         [0013]    In operation, the frame  18  is constructed at the remote location, and then the front and back walls  12 , the roof  14 , and the side walls  16  are pulled over the frame  18 . An air conditioning or heating unit  20  may be installed after the walls  12 ,  16  and the roof  14  are secured in their desired locations. The manner in which the frame  18  is constructed, the walls  12 ,  16  and the roof  14  (collectively, the flexible cover for the shelter  10 ) are pulled into place over the frame  18 , and connected to the frame  18 , and the air conditioning/heating unit  20  is installed, may be as described in U.S. patent application Ser. No. 13/283,772, filed Oct. 28, 2011, and/or U.S. Provisional Patent Application No. 61/598,194, filed Feb. 13, 2012. 
         [0014]    The entire disclosures of application Ser. No. 13/283,772 and 61/598,194 are incorporated herein by reference. The present invention should not be limited, however, to the configurations illustrated in application Ser. No. 13/283,772 and 61/598,194. 
         [0015]    According to one aspect of the invention, the flexible cover  12 ,  14 ,  16  may be formed entirely of the multi-layer flexible fabric  30  that is illustrated in  FIG. 2 . The fabric  30  includes an outer layer  32 , a metallized inner layer  34 , an insulation layer  36 , and a liner layer  38 . When the shelter  10  is fully constructed, the outer layer  32  faces the outside  40 , whereas the liner layer  38  faces the air-conditioned or heated interior  42  of the shelter  10 . 
         [0016]    The outer layer  32  may be formed of a flexible material that is tough, durable, rugged, and weather-resistant. The preferred material ( 32 ) is water-proof, mildew-resistant, ozone-resistant, and resistant to degradation that could otherwise be caused by high temperature, changes in temperature, rough handling, and sunlight, including ultraviolet light. In a preferred embodiment of the invention, the outer layer  32  includes a vinyl material, preferably a material formed of a synthetic polyvinyl chloride resin. If desired, the outer layer  32  may be formed of flexible, vinyl-coated polyester fabric. If desired, one or more outer vinyl layers  32  may be coated on the metallized layer  34  (or coated on another layer of the cover). In an alternative embodiment, one or more outer vinyl layers  32  may be laminated onto the metallized layer  34  (or laminated onto another layer of the cover). 
         [0017]    In a preferred embodiment, the outer layer  32  can be used to conceal the metallized layer  34 , and thereby help to conceal the shelter  10 , for example, from optical detection (camouflage) and/or from detection by radar. 
         [0018]    The metallized inner layer  34  may be formed of a material that reflects thermal radiation. The material ( 34 ) may be, for example, a metallic coating applied to the inside surface  46  of the outer layer  32 . The metallic coating ( 34 ) may be formed of aluminum and/or an alloy of aluminum and silver. The coating ( 34 ) may be painted on the surface  46  of the outer layer  32 . Alternatively, the coating ( 34 ) may be chemically deposited or vapor-deposited onto the inside surface  46  of the outer layer  32 . If desired or required to prevent corrosion of the metallic layer  34 , the inner surface  48  of the coating ( 34 ) may be treated or provided with a protective resin coating (not shown). 
         [0019]    In operation, the inner layer  34  reflects incident thermal radiation  50  that is transmitted onto and through the outer layer  32 . The reflective layer  34  causes the thermal radiation  52  to be re-transmitted back out through the outer layer  32 , away from the shelter. Thus, the outer layer  32  and the metallized inner layer  34  cause the shelter to have low emissivity. Emissivity (ε) is inversely related to reflectivity and is the value given to a material based on the ratio of heat emitted compared to a blackbody, on a scale of 0 to 1, where a blackbody has an emissivity of 1 and a perfect reflector has an emissivity of 0. The shelter  10  shown in  FIG. 1  may have an emissivity ε that is less than or equal to 0.5 (ε≦0.5). 
         [0020]    The insulation layer  36  ( FIG. 2 ) may include one or more layers of a felt material, foam, or other multi-cellular heat-insulating material. The insulation material  36  may include air cells, pockets and tortuous paths for preventing conductive and convective heat transfer through the flexible material  30 . 
         [0021]    The liner layer  38  may be attached to the insulation layer  36 . The liner layer  38  may be chemically adhered to the insulation layer  36 , or the liner layer  38  may be attached to the insulation layer  38  by quilting or the like (not shown). Alternatively, the liner layer  38  may be separate from (not attached to) the insulation layer  36 . 
         [0022]    The illustrated shelter  10  ( FIG. 1 ) may be, for example, an emergency medical tent that is on the order of thirty-two feet long, with an installed rigid floor (not shown). The shelter  10  has improved portability (it is easy to transport and quick to set up), and the shelter  10  may be less expensive to produce and deploy than known shelters. The invention is not limited to the shelter shown in the drawings. Among other things, the invention also relates to a tent, a semi-permanent home, and the like. 
         [0023]    In an alternative embodiment, the air conditioning unit  20  may be replaced or supplemented by a heating unit that supplies heated air, or a unit for providing ventilation, or a unit that provides heat, ventilation, and/or air conditioning (cool air) (HVAC). The illustrated portable shelter may be deployed in a wide variety of climates and locations, including cold or very cold locations, where the cover described herein provides suitable insulation for efficiently retaining heat within the portable shelter. 
         [0024]    The invention is not limited to the structures, methods and instrumentalities described above and shown in the drawings. The invention is defined by the claims set forth below.

Summary:
A portable shelter with low emissivity is provided for sheltering materials or human occupants at a remote location. The shelter has a flexible, multi-layer cover, including a vinyl material, reflective material located inside and immediately adjacent to the vinyl material, and insulation material located inside the reflective material. The low-ε vinyl cover is lightweight and thermally efficient. The shelter may be adapted for use with interior-climate control equipment at the remote location.