Abstract:
A cargo container that includes a U-shaped panel, and/or an L-shaped panel is disclosed. The cargo container has a top, bottom, and two sides, each U-shaped and/or L-shaped panels forms part of the top and a side, or the bottom and a side. The cargo container may further include doors with hinges and/or doors that slide. Landing gear may support the container when not in transit. The U-shaped and/or L-shaped panels may be inhomogeneous in size and thickness to reinforce the areas of highest stress concentration such as the container edges or the attachment location of the landing gear. The cargo container may also have a bottom floor with a greater thickness than each of the significantly parallel sides, or a bottom floor with parallel or interconnected support protrusions. The U-shaped and/or L-shaped panels may include internal support structures. Also disclosed is a method of manufacturing U-shaped and/or L-shaped panels.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to provisional application Ser. No. 60/961,165, entitled “Cargo Container with U-shaped Panels” filed Jul. 19, 2007 to Mark Roush, the contents of which are herein incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to cargo containers. More specifically, it relates to cargo containers that include U-shaped and/or L-shaped panels. 
       BACKGROUND OF THE INVENTION 
       [0003]    Cargo containers are well known, and are typically transported by ships, trains, and trucks. Containers may also be transported by air, and certain containers have been specially shaped to fit into the curved hulls of airplanes. In most instances it is desirable to reduce the weight of the cargo container to conserve fuel and, in some applications, increase the weight of the cargo that may be carried. For example, Federal Truck Size and Weight limitations restrict gross vehicle weight to less than 80,000 pounds on the U.S. Interstate system. If the weight of the container can be decreased, the maximum transportable cargo weight is increased. Thus, it is desirable to have a cargo container with a minimal weight so that cargo weight can be maximized. 
         [0004]    The use of polymer materials in lieu of metal components in container construction can reduce the total weight of the container. However, polymers may fracture when a force is exerted upon the material. Fractures in polymers cannot usually be repaired as easily as dents in metal, and complete replacement of the fractured polymer is often required. Thus, it is desirable to minimize the size of complete polymer sections so that, if replacement becomes necessary, the amount of material being replaced is minimized when repair is required. 
         [0005]    The complexity of panel joints often results in structural weakness due to a greater likelihood of a defective or improperly assembled portion. In contrast, panel fabrication is commonly a simpler, more automated process producing a product of more consistent quality. Joints that utilize multiple materials, such as bolts and clips, are further subjected to increased corrosion, uneven wear, and uneven thermal expansion and contraction. Also, since joints are typically at the very ends of panels, forces acting upon a jointed panel will commonly exert the greatest torque at the joint. 
         [0006]    Cargo container joints often require significant reinforcement so that the joint can withstand the compressive and tension load exerted upon them. Joint reinforcement increases the total weight of the container, often reducing the amount of cargo that can be legally carried. The size of the joint reinforcements may even reduce the total cargo volume carryable. Cargo containers with rounded edges have the advantage of providing a substantially continuous load path where the force of the load is substantially spread between the vertical and horizontal portions of the container. Even if the amount of cargo is not limited by the reinforcements, the additional weight will often increase the cost of transporting the container. 
         [0007]    Cargo containers and panels wear out with time and must eventually be replaced, thus it is desirable to have a cargo container that is easily manufactured with small replaceable panels. Additionally, expensive machinery is often required to produce large polymer panels while smaller pieces can be produced by smaller, cheaper, machinery. Also, the use of a segmented cargo container allows for the parallel production of several components at once. 
         [0008]    There are many problems associated with cargo container joints, joint reinforcement, container construction, and the forces exerted upon the edges of cargo containers. Thus, it is desirable to have a cargo container with rounded edges made from a plurality of panels where the panel joints and rounded edges of the container are spatially separated. 
         [0009]    There have been attempts to solve these problems, however none have yielded a solution capable of solving all of the disclosed problems. For example, U.S. Pat. No. 5,289,933 that issued to Streich et al. discloses a collapsible cargo container that is jointed together in the corner regions of the container. The &#39;933 patent fails to disclose the use of highly curved panels capable of distributing torsional forces over a large area of the joint. 
         [0010]    U.S. Pat. No. 4,214,669 that issued to McQuiston discloses a collapsible cargo container with joints that are not located at the edges of the container. As with the &#39;933 patent, the &#39;669 patent fails to disclose rounded edges, and shows reinforced corners. 
         [0011]    U.S. Pat. No. 5,690,378 issued to Romesburg discloses a monocoque cargo container that with a top and bottom piece jointed together. The &#39;378 patent, however, fails to disclose the use of many separate panels in the construction of the cargo container. Such a design is not easily manufacturable or repairable due to the use of very large component pieces. 
         [0012]    U.S. Pat. Nos. 5,041,318, 5,472,290, and 6,095,715 that issued to Hulls disclosed the use of joints between the top and side of a cargo container that provide “a substantially continuous load path.” The Hulls patents disclose the advantages of a cargo container with curved edges, but fail to disclose a joint that is distant from the cargo container edges. The Hulls patents also do not disclose the use of multiple individual panels that can be easily manufactured or replaced when damaged. 
       SUMMARY OF THE INVENTION 
       [0013]    In accordance with preferred embodiments of the present invention, many of the problems associated with cargo containers are overcome. A light weight cargo container with U-shaped and/or L-shaped panels is presented. 
         [0014]    The cargo container includes a top roof, a bottom floor, and two significantly parallel sides. The cargo container includes U-shaped panels, and/or L-shaped panels, that form part of the top roof and parallel sides, or the bottom floor and parallel sides. The cargo container may further include doors with hinges and/or doors that slide. Landing gear may support the container when the container is not in transit. The U-shaped, and/or L-shaped panels may be non-uniform in size and thickness to reinforce the areas of highest stress concentration. The cargo container may further include a bottom floor with greater thickness than each of the significantly parallel sides, or a bottom floor with parallel or interconnected support features. The U-shaped, and/or L-shaped panels may include internal support structures. Also presented is a method of manufacturing U-shaped and/or L-shaped panels. 
         [0015]    The foregoing and other features and advantages of the preferred embodiments of the present invention will be more readily apparent from the following detailed description. The detailed description proceeds with references to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Preferred embodiments of the present invention are described with reference to the following drawings, wherein: 
           [0017]      FIG. 1  is a schematic view of machinery continuously manufacturing U-shaped panels where not all the panel material passes through a final forming means; 
           [0018]      FIG. 2  is a second schematic view of machinery continuously manufacturing U-shaped panels where not all the panel material passes through a final forming means; 
           [0019]      FIG. 3  is a schematic view of machinery continuously manufacturing U-shaped panels where all the panel material passes through a final forming means; 
           [0020]      FIG. 4  is a flow diagram illustrating a method for creating U-shaped panels and a cargo container including the panels; 
           [0021]      FIG. 5  is a flow diagram illustrating a method for creating U-shaped panels and a cargo container using exemplary embodiments of fiber, resin, and structural supports; 
           [0022]      FIG. 6  is a perspective view of a cargo container that comprises a plurality of U-shaped panels, a wheel assembly, and landing gear; 
           [0023]      FIG. 7  is a rear sectional view of a cargo container that comprises a plurality of U-shaped panels, joint connectors, flat side panels, and a wheel assembly; 
           [0024]      FIG. 8  is an exploded rear sectional view of a cargo container that comprises a plurality of U-shaped panels, joint connectors, flat side panels, and a wheel assembly; 
           [0025]      FIG. 9  is a rear sectional view of a cargo container that comprises a plurality of U-shaped panels, joint connectors, and a wheel assembly; 
           [0026]      FIG. 10  is a rear sectional view of a cargo container that comprises a top U-shaped panel, joint connectors, a wheel assembly, and a bottom U-shaped panel that significantly defines the sides of the cargo container; 
           [0027]      FIG. 11  is a rear sectional view of a cargo container that comprises a bottom U-shaped panel, joint connectors, a wheel assembly, and a top U-shaped panel that significantly defines the sides of the cargo container; 
           [0028]      FIG. 12  is a rear sectional view of a cargo container that comprises two top L-shaped panels, two bottom L-shaped panels, joint connectors, and a wheel assembly; 
           [0029]      FIG. 13  is a partial rear sectional view of a cargo container, where a structural support is integrally formed into part of a U-shaped panel; 
           [0030]      FIG. 14  is a partial rear sectional view of a cargo container, where a plurality of structural gaps are in a top U-shaped panel; 
           [0031]      FIG. 15  is a partial rear sectional view of a cargo container, where a plurality of honeycomb and rod-like structural supports are in the structural gaps of a U-shaped panel; 
           [0032]      FIG. 16  is a partial rear sectional view of a cargo container, where a plurality of I-beam and rod-like structural supports are in the structural gaps of a U-shaped panel; 
           [0033]      FIG. 17  is a rear perspective view of a cargo container with that includes a plurality of flat side panels, top U-shaped panels, and bottom U-shaped panels, where a single panel has been damaged; 
           [0034]      FIG. 18  is a bottom perspective view of a trailer made from U-shaped panels where a non-integral structural support is connected to the floor of the trailer; 
           [0035]      FIG. 19  is a side view of a trailer made from U-shaped panels, where panels of increased thickness connect to the trailer landing gear and wheel assembly; 
           [0036]      FIG. 20  is a rear perspective view of a cargo container made from U-shaped panels, where the trailer has a side door and a rounded rear section that also has a door; 
           [0037]      FIG. 21  is a front perspective view of a cargo container made from U-shaped panels that has a flat front section; 
           [0038]      FIG. 22  is a partial sectional view of two panels connected at a flat joint by an adhesive; 
           [0039]      FIG. 23  is a partial sectional view of two panels connected at a T-joint by an adhesive; 
           [0040]      FIG. 24  is a partial sectional view of two panels connected at a T-joint by a cross bolt and an adhesive; 
           [0041]      FIG. 25  is a partial sectional view of two panels connected with an H-shaped connector by an adhesive; 
           [0042]      FIG. 26  is a partial sectional view of two panels with routed edges connected with an H-shaped connector by an adhesive; and 
           [0043]      FIG. 27  is a partial sectional view of a panel with a convex section connected to a panel with a concave section by an adhesive. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0044]    Referring to the figures, exemplary embodiments of the invention will now be described. The exemplary embodiments are provided to illustrate aspects of the invention and should not be construed as limiting the scope of the invention. The exemplary embodiments are primarily described with reference to the figures. 
         [0045]    Exemplary Panel Manufacturing Machine 
         [0046]      FIGS. 1 and 2  illustrate an exemplary embodiment of machinery continuously manufacturing U-shaped panels. Fiber material  102  drawn from a fibrous material source  101  is fed into a pre-forming device  103  that creates a fiber sheet of substantially parallel fibers. Resin applicators  104  apply resin to the fiber sheet creating a resin impregnated sheet where substantially all of the fibers are oriented parallel to each other. Computer controlled heated and cooled forming guides  105 , further shape the resin impregnated fiber sheet  106 . The sheet is drawn through a pulling means  107 , and passed through a U-shaped shaping means with an outer forming means  109  and an inner forming means  110 . At predetermined intervals, a cutting means  108  segments the U-shaped sheets into U-shaped panels  112  with fibers that are locally oriented substantially parallel to each other despite macro-scale changes in orientation due to the U-shape curvature of the panel. The panels are transported away from the machinery by a moving means  111 . In another embodiment of the invention, L-shaped panels are formed by cutting the sheets before a second bend is put into the panels. 
         [0047]      FIG. 3 , illustrates a second exemplary embodiment of machinery continuously manufacturing U-shaped panels. Fiber material  102  drawn from a fibrous material source  101  is fed into a pre-forming device  103  that creates a sheet of substantially parallel fibers. Resin applicators  104  apply resin to the fiber sheet creating a resin impregnated sheet. Computer controlled heated and cooled forming guides  105  further shape the resin impregnated fiber sheet  106 . The sheet is drawn through a pulling means  107 , and passed through a U-shaped shaping means  300 . The U-shaped sheet  301  is cut by a cutting means at predetermined intervals to create U-shaped panels. In this embodiment of the invention, the fibers are oriented parallel to each other on both the micro and macro scale since the fibers extend perpendicular to the U-shaped curvature. In another embodiment of the invention, the U-shaped shaping means is replaced by an L-shaped shaping means. 
         [0048]    Exemplary Panel Method of Manufacture 
         [0049]      FIG. 4  is a flow diagram illustrating a method for creating a U-shaped panel from a pultrusion process. At Step  402  a length of fibrous material is impregnated with a resin. At Step  404  the impregnated fibrous material is combined with other impregnated fibrous materials. At Step  406  the resin impregnated fibrous materials are passed through at least one heating zone. At Step  408 , the heated resin impregnated fibrous materials are passed through a shaping die assembly to create a formed material. At Step  410 , the formed material is drawn through a second shaping die creating a U-shaped material. At Step  412 , the U-shaped material is cut to create a manufactured U-shaped panel. At Step  414 , multiple U-shaped panels are connected to create a cargo container. 
         [0050]    The method illustrated is an exemplary embodiment. However, the present invention is not limited to such an embodiment and other embodiments can also be used to practice this invention. 
         [0051]    In such an exemplary embodiment, at step  402  a length of fibrous material is impregnated with a resin. Examples of fibrous materials include injected molded glass, fiberglass, nylon™, glass material, stamped steel, stamped aluminum, carbon/nylon™ reinforced textile sheets, amarid, polyester, and carbon fiber. 
         [0052]    Examples of resins include epoxy, unsaturated polyester, urethane acrylate, vinyl ester, phenol, polyurethane, a thermoplastic resin (such as nylon 6, nylon 66, nylon 12), PBT, PET, polycarbonate, polyacetal, polyphenylene sulfide, polyether ether ketone, polyether sulfide, polyphenylene oxide, modified polyphenylene oxide, polypropylene, polyvinyl chloride, ethylene-vinyl acetate copolymer; polystyrene, acrylonitrile-butadiene-styrene copolymers (ABS), 6, 11, 12, 6-6 and 6-10 polyamides, poly(ether amide) sequenced copolymer, fluorinated polymers, polysulfone, polyethersulfone, polycarbonate, polyetheretherketone, polyphenylene sulfur, polyetherimide, and polyphenylene ether. 
         [0053]    At step  404  resin impregnated fibrous material is combined with other impregnated fibrous materials in a process that may include passing the resin impregnated material through a die to compress them, thus forcing the molten resin to penetrate between the fibers. 
         [0054]    At step  406  the resin impregnated fibrous materials are passed through at least one heating zone. Examples of heating zones include a heated tunnel, a heated die, and a heated solution bath. At Step  408 , the heated resin impregnated fibrous materials are passed through a shaping die assembly to create a formed material. In one exemplary embodiment of the invention, the shaping die includes both a heating means and a cooling means. At Step  410 , the formed material is passed through a second shaping die forming a material in the general shape of a U-shaped panel. At Step  412 , the material is cut to form a U-shaped panel. At Step  414 , multiple U-shaped panels are connected together to form a cargo container. Doors, hinges, a landing gear assembly that supports the front of the container during parking and storage, a king pin, and a wheel assembly are optionally connected to the cargo container. Post manufacture modifications to the cargo container may further include connecting additional structural supports, smoothing the outer surfaces, rounding off of one or both ends, connecting doors, and creating structural gaps in the floor, roof, and sides of the cargo container. Structural supports may be inserted into any structural gaps created. 
         [0055]    In another exemplary embodiment,  FIG. 5  illustrates a Method  500  for creating a cargo container. At Step  502 , a length of glass, carbon, amarid, or polyester fiber material is combined with other lengths of fibrous material. At Step  504 , the fibrous materials are impregnated with an unsaturated polyester, a vinyl ester, an epoxy, a methyl methalcrylate based, a phynolic, or a thermoplastic resin. At Step  506 , the resin impregnated fibrous materials are passed through a heated shaping die to create a shaped material. At Step  508 , two or more shaped materials are combined creating a U-shaped material. At Step  510 , the U-shaped material is drawn through a second heated shaping die creating a U-shaped material with structural voids. At Step  512 , the U-shaped material is cut substantially perpendicular to the direction the material is drawn, thereby creating a panel. At Step  514 , material is removed from the panel to reduce mass and/or improve aerodynamics. At Step  516 , structural supports are inserted into the structural voids of the U-shaped panel. Structural supports include I-beams, braces, and honeycomb supports made from carbon fiber, steel and/or aluminum alloys. At Step  518 , multiple panels are connected forming a cargo container. At Step  520 , two door assemblies are connected to at least one end of the cargo container, a wheel assembly is attached to the floor of the cargo container, and trailer landing gear assembly is connected to the floor of the cargo container. Post manufacture modifications to the cargo container may further include adding additional structural supports, smoothing the outer surfaces, rounding off of one or both ends, connecting additional doors, and creating structural gaps in the floor, roof, and sides of the cargo container. Structural supports may be inserted into any structural gaps created. 
         [0056]    Other machinery and methods for producing U-shaped and L-shaped panels may be utilized and are within the scope of the invention. For example, standard flat panels commonly used in cargo container construction may be bent into a U-shape or an L-shape. The materials that may be used in construction of the panels include, but are not limited to, polymers, metals such as aluminum and steel, stone and other minerals, wood, carbon fiber, and reinforced fabrics. Other materials and methods of manufacture will be obvious to those of reasonable skill in the art and are within the scope of the invention. 
         [0057]      FIG. 6 , illustrates a cargo container comprising an interior storage space defined by a plurality of top U-shaped panels  601 , side panels  602 , bottom U-shaped panels  602 , a top horizontal connection  604 , a bottom horizontal connector  605 , and a plurality of vertical connectors  606 . The cargo container also has a wheel assembly  620  and landing gear  630  connected to the bottom U-shaped panels. The U-shaped panels have vertical sidewalls located at the side of the trailer and horizontal sections forming either the roof or floor of the trailer. Connecting the vertical sidewalls to the horizontal sections are curved sections with the U-shaped panel. The horizontal connectors connect the U-shaped panels and the side panels. The vertical connectors are similarly shaped so as to provide a substantially watertight seal. In one embodiment of the invention, the cargo container has a length of 43 to 63 feet, a width of 95 to 107 inches, and a height of 100 to 120 inches (not including landing gear and the wheel assembly). In another embodiment of the invention, the U-shaped panels have a width (parallel to the wheel axis) of 90 to 107 inches that is substantially similar to the width of the wheel assembly. In an exemplary embodiment of the invention, the cargo container has a length of 53 feet, a width of 102 and 5/16ths inches, and a height of 110 inches (not including landing gear and the wheel assembly). In an exemplary embodiment of the invention, the cargo container has a height of 13 feet 6 inches (including landing gear and the wheel assembly), a width of between 98 and 105 inches, and a length of between 43 and 63 feet. 
         [0058]    U.S. Provisional Patent Application 60/930,926 titled “Cargo Tube” filed May 18, 2007 and U.S. Utility application Ser. No. 12/121,994 titled “Cargo Tube” filed May 16, 2008 by Mark Roush of Lafayette, Ind. are hereby incorporated by reference. The cargo container constructed from U-shaped panels may further include features disclosed in the &#39;926 and &#39;994 applications. For example, the cargo container constructed from U-shaped panels may have cross hatched structural supports as shown in  FIG. 11  of provisional “Cargo Tube,” or the cargo container may have a rounded rear section as shown in  FIG. 25  of provisional “Cargo Tube.” 
         [0059]      FIGS. 7 and 8  illustrate condensed and exploded rear sectional views of a cargo container comprising a top U-shaped panel  601 , two side panels  602 , and a bottom U-shaped panel  603 . The top and bottom U-shaped panels are connected to the side panels  602  by top connectors  604  and bottom connectors  605 , respectively. The bottom U-shaped panel has a greater thickness than the top U-shaped panel to support a load carried within the container. Additionally, in the top U-shaped panel, the network of parallel resin impregnated fibers extends uninterrupted from one top connector  604 , across the width of the panel, to the distant top connector on the other side of the trailer. Similarly, in the bottom U-shaped panel, the network of parallel resin impregnated fibers extends uninterrupted from one bottom connector  605 , across the width of the panel, to the distant bottom connector on the other side of the trailer. 
         [0060]      FIGS. 9 ,  10 , and  11  illustrate rear sectional views of cargo containers with connected upper and lower U-shaped panels. In  FIGS. 9 ,  10 , and  11  both the top U-shaped panel has sidewalls that are adjacent to the sidewalls of the bottom U-shaped panel. Specifically,  FIG. 9  shows a cargo container where the top U-shaped panel  901  and bottom U-shaped panel  903  are similar in dimensions. Such a design would maximize the distance between the edges of the container and the joints. Additionally, similarly dimensioned top and bottom U-shaped panels would facilitate manufacture since fewer modifications to the panel making machinery would be required to change between similarly shaped panels.  FIG. 10  shows a cargo container with a bottom U-shaped panel  1003  with sidewalls that are significantly taller than the sidewalls of the top U-shaped panel  1001 . The heights of the bottom sidewalls are substantially similar to the total height of the interior space since the sidewalls of the top U-shaped panel are quite short. The forces exerted upon the bottom edges are likely to be significantly greater than the forces exerted upon the top edges. 
         [0061]      FIG. 11  illustrates an embodiment of the invention with two U-shaped panels where the top panel  1101  has sidewalls that are similar in height to the total interior cargo space. Since the top sidewalls are tall, the sidewalls of the bottom U-shaped panel  1103  are short. Such a design is advantageous in that removal of the top U-shaped panel creates a cargo container that is substantially similar to a flat bed trailer.  FIG. 11  also illustrates a geometric plane  1104  about which both the top and bottom U-shaped panel are symmetrical. The geometric plane is substantially vertical, extends the length of the trailer, and intercepts a middle of the landing gear assembly, wheel assembly, and a kingpin of the trailer. Since the resin impregnated fibers are substantially parallel, the U-shaped panels may be substantially symmetrical about the geometric plane on a micro(individual fibers) and macro scale(general curvature of the panel). 
         [0062]      FIG. 12 , illustrates a rear cross section of a cargo container comprising a plurality of L-shaped top panels  1201 , a plurality of flat side panels  602 , and a plurality of L-shaped bottom panels  1203 . The L-shaped panels are connected to other panels by connectors. In  FIG. 12 , the top L-shaped panels form a non-planar cargo container roof. Such a design may be beneficial in reducing wind resistance on the container, and/or reducing mechanical stress. L-shaped panels are smaller in size than U-shaped panels thereby facilitating manufacture and replacement when necessary. 
         [0063]      FIG. 13  illustrates a partial sectional rear view of a U-shaped panel with structural supports. An integral structural support  1301  reinforces the curvature of the U-shaped panel without changing its dimensions. Although there are structural supports in the U-shaped panel, the structural network/lattice of resin and fibers extends uninterrupted from the horizontal section of the panel, through the curved section of the panel, to the vertical sidewall of the U-shaped panel. Despite a structural support, a continuous unbroken path of fiber impregnated resin extends from the horizontal section to the vertical sidewall. 
         [0064]      FIG. 14  illustrates a partial sectional rear view of a U-shaped panel and connector. Structural gaps  1402  are included in the U-shaped panel. The structural gaps may include pitched truss, parallel chord truss, truncated truss, and Vierendeel truss formations. The structural gaps reduce the weight of the U-shaped panel which can decrease the cost of transporting a cargo container made from U-shaped panels. The structural gaps  1402  may be formed during the manufacture process, added after the manufacture process by the removal of material, or added after the manufacture process by adding material to the U-shaped panel. Additionally, the curvature of the outer edge of the panel  1404  is not the same as the curvature of the inner edge of the panel  1406 . Increased panel thickness at locations of curvature can increase the structural integrity of the cargo container without an increase in the height and/or width. Although there are structural gaps in the U-shaped panel, the structural network/lattice of resin and fibers extends uninterrupted from the horizontal section of the panel, through the curved section of the panel, to the vertical sidewall of the U-shaped panel. Despite structural gaps, a continuous unbroken path of fiber impregnated resin extends from the horizontal section to the vertical sidewall. 
         [0065]      FIG. 15 , indicated generally at  1500  illustrates a partial sectional rear view of a U-shaped panel and connector. Weight reducing structural gaps  1502  included in the U-shaped panel. The structural gaps may include pitched truss, parallel chord truss, truncated truss, and Vierendeel truss formations. The structural gaps  1502  may be formed during the manufacture process, added after the manufacture process by the removal or addition of material. Additionally, the curvature of the outer edge of the panel  1504  is not the same as the curvature of the inner edge of the panel  1506 . Increased panel thickness at the curved portions can increase the structural integrity of a cargo container made from panels without an increase in the height and or width of the container. Rod shaped  1502  and honeycomb shaped  1504  support materials are included in the weight reducing structural gaps. 
         [0066]      FIG. 16  illustrates a partial sectional rear view of a bottom U-shaped panel. Rod shaped and I-beam shaped  1601  support materials are included in the weight reducing structural gaps. In  FIG. 16 , substantially all of the resin impregnated fibers are oriented parallel to each other and extend perpendicular to the plane of the image. 
         [0067]      FIG. 17  illustrates a rear perspective view of a cargo container that has been impacted in a vehicle collision. As a result of the vertical connectors  606 , and horizontal connectors, the force of the impact was confined to a single panel  1701 , thus causing greater trauma to a single panel while preventing damage to the other panels. The damaged panel can be replaced without having to replace a significant amount of undamaged material. 
         [0068]      FIG. 18  illustrates a bottom perspective view of a cargo container with a non-integral structural support  1801  connected to a cargo container by an attachment means such as rivets, adhesives, nails, screws, welds, or bolts. The structural support is partially located between the wheel assembly and the bottom U-shaped panel. In one embodiment of the invention the structural support extends from about the wheel assembly to about the landing gear assembly (not shown). 
         [0069]      FIG. 19  illustrates a side perspective view of a cargo container with a rounded rear end  1901 . The U-shaped panels of the cargo container connecting to the wheel assembly and landing gear ( 1902  and  1903 ) have non-uniform thicknesses. The increased floor thickness at those locations help to dissipate the force exerted on the cargo container by the landing gear and wheel assembly. Between the landing gear and wheel assembly the floor thickness may be substantially less as shown in  FIG. 19 . The regions of increased floor thickness may be created during a pultrusion process by utilizing a variable cross section method, or by fastening additional material to the cargo container post manufacture. 
         [0070]      FIG. 20  illustrates a partial rear perspective view of a cargo container, made from U-shaped panels, that has a rounded rear section  1901 , a sliding rear door  2001 , and a second door  2002  between the front and read of the cargo container. In another embodiment of the invention, both sides of the cargo container have sliding doors. The additional doors allow for faster loading and unloading of the cargo container, especially when only a portion of the container contents are unloaded. 
         [0071]      FIG. 21  illustrates a front perspective view of a cargo container made with U-shaped panels that include a flat front face  2101  connected to one end of the cargo container. In other embodiments of the invention, the front face is tapered or rounded. 
         [0072]      FIGS. 22-27  illustrate various embodiments of panel joints.  FIG. 22  shows a first and second panel ( 2201  and  2202 ), each with a flat surface bonded together by an adhesive  2203 . The thickness of the adhesive layer has been greatly exaggerated for clarity. The design illustrated in  FIG. 22  has the advantage of simplicity, but lacks bonding strength due to the minimal panel surface area contacting the adhesive.  FIG. 23  illustrates a panel with a protrusion  2301  that fits into a panel with a gap  2302 . The two panels are further bonded by an adhesive. Such a connection increases the surface area of the panels contacting the adhesive  2203  which results in the bonding strength of the joint shown in  FIG. 23  being greater than the joint shown in  FIG. 22 . 
         [0073]      FIG. 24  shows a connection similar to  FIG. 23 , with the addition of a bolt  2401  securing both panels. The addition of a bolt may increase the strength of the panel connection; however, a bolt increases the total weight of the cargo container and increases the thickness of the panels.  FIG. 25  shows two panels similar to those illustrated in  FIG. 22  with the addition of an H-shaped connector  2501  that increases the surface area on to which an adhesive can bond. Like the bolt shown in  FIG. 24 , the H-shaped connector of  FIG. 25  increases the total width of the side of the cargo container. The routed panels  2601  shown in  FIG. 26  have edges routed so that the outer sides of the H-shaped connector are substantially flush with the sides of the panels.  FIG. 27  illustrates another panel joint between a panel with a convex section  2701  and a panel with a concave section  2702 . The use of convex and concave sections allows for a large contact area between panels like the connection shown in  FIG. 23 , while allowing for a slight rotation of the panels which may assist in the fabrication of the cargo container and absorb small impacts on the cargo container. 
         [0074]    Examples of adhesives for bonding panels together include, but are not limited to unplasticized polyvinylchloride (PVC), polyethylene oxide, copolymers of ethylene and acrylic acid (EAA), acrylic materials, rubber base cement, an epoxy based system, and a urethane based system. DP 420™ and SA 8053™ (available from Minnesota Mining and Manufacturing Corporation of St. Paul, Minn.) may also be used as adhesives. 
         [0075]    It should be understood that the programs, processes, methods and systems described herein are not related or limited to any particular type components or materials unless indicated otherwise. Various combinations of general purpose, specialized or equivalent components may be used with or perform operations in accordance with the teachings described herein. 
         [0076]    In view of the wide variety of embodiments to which the principles of the present invention can be applied, it should be understood that the illustrated embodiments are exemplary only, and should not be taken as limiting the scope of the present invention. For example, any object described may comprise other materials not recited, and the steps of the flow diagrams may be taken in sequences other than those described, and more, fewer or equivalent elements may be used in the block diagrams.