Abstract:
Various embodiments of the present invention provide an insulated structural panel including a superinsulating, desiccant-filled, vacuum-sealed insulating panel sandwiched between a pair of composite panels. The composite panels are configured to impart structural strength to the panel without introducing heat transfer pathways through the vacuum-sealed insulating panel. The desiccant material disposed within the vacuum-sealed insulating panel is capable of absorbing moisture within the vacuum established within the vacuum-sealed insulating panel and thereby reducing the degradation of the vacuum-sealed panel&#39;s insulating capacity.

Description:
FIELD OF THE INVENTION 
     Various embodiments of the present invention are directed to a super-insulated composite structure for use as a component of a refrigerated truck body. 
     BACKGROUND OF THE INVENTION 
     The temperature regulation of refrigerated containers such as, for example, refrigerated truck bodies and trailers, is managed by providing a combination of cooling elements (such as refrigeration units and/or “cold plate” devices, for example) and insulated structural elements. The required cooling capacity of the cooling elements is largely dependent on the difference in temperature that must be maintained between the interior and exterior of the refrigerated container. Furthermore, the cost and complexity of the cooling system may be substantially reduced if the structure is thermally efficient (as quantified, for example, by a high “R” value). Thus, refrigerated containers are often constructed from components that serve both as structural components and insulating elements. 
     Conventional insulated structural elements utilized in refrigerated containers include a metal frame sandwiched between fiberglass layers. In order to provide insulation to the structure, foam is injected or blown into the space defined between the fiberglass layers. Such conventional insulated structures suffer from several technical deficiencies. First, the metal frame adds considerable weight to the assembly. The metal frame also creates significant heat transfer pathways or “thermal shorts” between the fiberglass layers that may degrade the overall R value of the structural element. In addition, conventional insulated structures also suffer from durability problems that cause the degradation of the structure&#39;s insulating capacity over time. For example, as conventional insulated structures are subjected to the everyday rigors of use and transport, the injected and/or blown foam layer tends to break apart, which may result in serious degradation of the R value of the structure. 
     Although conventional insulated structures suffer from the disadvantages outlined above, their use is still prevalent in refrigerated cargo and storage applications primarily due to availability, relative ease of assembly and low cost, and because the use of metal-reinforced fiberglass panels (having blown foam insulating filler) is relatively consistent and well-known. However, in light of the shortcomings of these conventional insulated structures, there exists a need in the art for an insulated structural element for use in refrigerated containers (such as, for example, refrigerated truck bodies and trailers) that is lightweight, durable, and provides a robust and thermally-efficient insulating capacity. 
     BRIEF SUMMARY OF THE INVENTION 
     Certain embodiments of the present invention satisfy the needs listed above and provide other advantages as described below. Embodiments of the present invention may include an insulated composite panel assembly for a refrigerated truck body (and/or other refrigerated container). According to one embodiment, the assembly comprises a first composite panel and a second composite panel disposed substantially parallel to and spaced apart from the first composite panel. The assembly also comprises a vacuum-sealed insulating panel operably engaged between the first composite panel and the second composite panel. The vacuum-sealed insulating panel comprises a desiccant material disposed within the vacuum-sealed insulating panel. Some embodiments may further comprise a polyurethane coating material disposed on an outer side of at least one of the first composite panel and the second composite panel. 
     In some embodiments, the vacuum-sealed insulating panel comprises a plurality of vacuum-sealed component elements. Furthermore, according to some such embodiments, each of the plurality of vacuum-sealed component elements may define at least one channel and at least one tab, such that the vacuum-sealed component elements may be operably engaged with one another to form a larger vacuum-sealed insulating panel. For example, in some embodiments, the tab of a first vacuum-sealed component element may be inserted into a corresponding channel of a second vacuum-sealed component element for form a substantially continuous and/or interconnected vacuum-sealed insulating panel. 
     Furthermore, according to some embodiments, the vacuum-sealed insulating panel may comprise a foam core material defining an aperture for retaining the desiccant material. The foam core material may comprise insulating materials that may include, but are not limited to: open cell polyurethane foam; polystyrene foam; carbon/silica aerogel; and combinations of such insulating materials. Furthermore, the desiccant material may comprise, for example, one or more silica gel packets. The vacuum-sealed insulating panel may also comprise a cover material configured to surround the foam core material. The cover material may comprise a variety of substantially gas-impermeable materials that may include, but are not limited to: a metallic film; a polymer laminate; and combinations of such substantially gas-impermeable materials. 
     The first composite panel and the second composite panels of the insulated composite panel assembly may comprise various types of structural composites that may include, but are not limited to: fiber reinforced polymer materials; fiber reinforced polymer composites; solid laminates; and combinations of such materials. In embodiments wherein at least one of the first and second composite panels comprise a fiber reinforced polymer composite, the fiber reinforced polymer composite may include, but is not limited to: a pultruded sandwich panel comprising an upper skin and a lower skin and a core disposed substantially between the upper and lower skins; a vacuum-infused sandwich panel comprising an upper skin and a lower skin and a core disposed substantially between the upper and lower skins; a pultruded panel comprising an upper skin and a lower skin and a web material disposed substantially between the upper and lower skins; and combinations of such fiber-reinforced polymer composites. 
     In order to securely and operably engage the various components of the insulated composite panel structure, some embodiments may further comprise an adhesive layer disposed between the vacuum-sealed insulating panel and at least one of the first composite panel and the second composite panel. The adhesive layer may include, but is not limited to a methacrylate adhesive and a contact adhesive (such as a spray-on contact adhesive, for example). Furthermore, in some embodiments, the insulated composite panel assembly further comprises at least one bracket extending substantially perpendicularly from at least one edge of the insulated composite panel assembly for receiving a side wall adapted to extend substantially perpendicularly from the insulated composite panel assembly. The bracket may, in some embodiments, be integrally formed with the insulated composite panel assembly. The bracket may comprise one or more composite materials that may include, but are not limited to: pultruded tubing materials; extruded composite tubing materials; composite tubing materials comprising a polyurethane matrix and a plurality of E-glass fibers disposed within the polyurethane matrix; and combinations of such materials. Furthermore the bracket may, in some embodiments, allow multiple insulated composite panel assemblies to be formed together to form a refrigerated truck body and/or other refrigerated container as part of a cargo vehicle. For example, some embodiments of the present invention provide an insulated structure comprising a floor comprising, for example, the insulated composite panel assembly described herein. Such insulated structure embodiments may further comprise a wall member comprising the insulated composite panel assembly described herein, wherein the wall member is operably engaged with the floor to form an integrated insulated structure. 
     Thus, the various embodiments of the insulated composite panel assembly of the present invention provide many advantages that may include, but are not limited to: providing an insulated structural assembly that is durable and lightweight; providing a insulating structural panel assembly having an insulating capacity (and/or R value) that degrades minimally during the product life of the assembly; and providing an insulated structural panel assembly that includes robust, vacuum-sealed insulating components that are less likely to decompose and/or break down during the rigors of use and transport. 
     These advantages, and others that will be evident to those skilled in the art, are provided in the various embodiments of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1  is a cross-sectional schematic of an insulated composite panel assembly according to one embodiment of the present invention; 
         FIG. 2  is a cross-sectional schematic of a pair of interlocking vacuum-sealed component elements connected to form at least a portion of the vacuum-sealed insulating panel, according to one embodiment of the present invention; and 
         FIG. 3  is a cross sectional schematic of two insulated composite panel assemblies operably engaged with one another via at least one bracket, according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. 
     Although the preferred embodiments of the invention described herein are directed to an insulated composite panel assembly for a refrigerated truck body, it will be appreciated by one skilled in the art that the invention is not so limited. For example, aspects of the insulated composite panel assembly design of the present invention can also be incorporated into refrigerated trailers, refrigerated containers, refrigerated boxcars, mobile refrigerated storage units, and/or other insulated structures. 
     Referring to  FIG. 1 , one embodiment of the present invention provides an insulated composite panel assembly  1  comprising, a first composite panel  10   a  and a second composite panel  10   b  disposed substantially parallel to and spaced apart from the first composite panel  10   a . The assembly  1  further comprises at least one vacuum-sealed insulating panel  12  operably engaged between the first composite panel  10   a  and the second composite panel  10   b . As shown in  FIG. 1 , the vacuum-sealed insulating panel  12  comprises a desiccant material  14  (such as, for example, at least one silica gel packet) disposed therein such that an insulating capacity of the vacuum-sealed insulating panel  12  is less likely to degrade substantially over the course of the product life of the panel  12 . The desiccant material  14  may also comprise one or more getter elements configured to be capable of absorbing a variety of gasses within a substantially evacuated environment established within the vacuum-sealed insulating panel  12  so as to reduce and/or minimize the degradation of the insulating capacity of the vacuum-sealed insulating panel  12 , as discussed further herein. The desiccant material  14  may comprise a variety of materials including, but not limited to: silica gel, indicating silica gel, molecular sieve, clay (montmorillonite, for example), activated carbon, and combinations thereof. 
     In some embodiments, the vacuum-sealed insulating panel  12  may comprise a plurality of discrete desiccant material  14  units (such as a plurality of silica gel packets, for example) disposed within a foam core material  13  as shown in  FIG. 1  and described herein. In some embodiments, the desiccant material  14  may be disposed within the vacuum-sealed insulating panel  12  at selected intervals such that the desiccant material  14  is present within the insulated composite panel assembly  1  at a corresponding selected density so as to be capable of absorbing a selected amount of fluid and/or gas within the vacuum-sealed insulating panel. In some embodiments, the desiccant material  14  may be disposed within the vacuum-sealed insulating panel  12  at a density of about 1 packet (or unit) of desiccant material  14  per each 12 inch by 12 inch vacuum-sealed insulating panel  12 . Furthermore, in some embodiments, the desiccant material  14  may be disposed within the vacuum-sealed insulating panel  12  at a density of about 2 packets of desiccant material  14  per each 12 inch by 12 inch vacuum-sealed insulating panel  12 . Each packet of desiccant material  14  may comprise, for example, a commercially-available blend desiccant packet such as a MiniPax® “sorbent” packet available from Multisorb Technologies, Inc. of Buffalo, N.Y. In some embodiments, the desiccant material  14  may comprise a series of individual desiccant packs connected in a “strip” configuration, such as the “Packet Strip” disclosed in U.S. Pat. No. 4,957,521, which is hereby incorporated herein by reference in its entirety. Such “packet strip” embodiments of the desiccant material  14  may comprise commercially-available products including, but not limited to, StripPax® “sorbent” packets also available from Multisorb Technologies. 
     According to some embodiments, the vacuum-sealed insulating panel  12  comprises a foam core material  13  defining an aperture (such as an elongated channel, for example) for retaining the desiccant material  14 , and a cover material  15  surrounding the foam core material  13 . The foam core material  13  may include, but is not limited to: open cell polyurethane foam; polystyrene foam; carbon/silica aerogel; and combinations of such materials. Furthermore, the cover material  15  may comprise a substantially gas-impermeable material that may include, but it not limited to: a metallic film; a polymer laminate; and combinations of substantially gas-impermeable materials. 
     Thus, according to such embodiments, the substantially gas-impermeable material of the cover material  15  may allow for the establishment and/or maintenance of a substantial vacuum within the vacuum-sealed insulating panel  12 . As one skilled in the art will appreciate, the insulation value (denoted, for example, by an R value) of some materials (such as a foam core material  13 , for example) may be increased substantially by maintaining the material in an evacuated environment. Furthermore, as described herein, embodiments of the assembly  1  comprise a desiccant material  14  disposed within the foam core material  13  that is capable of absorbing moisture and/or gases within the evacuated environment established by the cover material  15  so as to prevent (and/or delay) an elevation of an internal pressure within the confines of the cover material (which may, in turn, degrade the insulating capacity (and/or R value) of the vacuum-sealed insulated panel  12 ). Thus, as described herein, the construction and materials of the vacuum-sealed insulating panel  12  may thus reduce and/or minimize the degradation of an insulating capacity of the vacuum-sealed insulating panel  12  over a selected period of time. For example, in some embodiments, wherein the initial R value of the vacuum-sealed insulating panel  12  may initially be substantially about 40R per inch of thickness, the R value may degrade only to substantially about 30R per inch over about 25 years. 
     As shown generally in  FIG. 2 , in some assembly  1  embodiments, the vacuum-sealed insulating panel  12  may comprise a plurality of discrete vacuum-sealed component elements  12   a ,  12   b . The vacuum-sealed component elements  12   a ,  12   b  may comprise, for example, a plurality of superinsulator “bricks” having a selected R value that may include, but is not limited to: R10, R15, R20, R25, R30, R35, R40, R45 and R50 wherein the R value is provided on a per inch of panel  12  thickness. For example, the vacuum-sealed insulating panel  12  (and/or component elements  12   a ,  12   b , thereof) may comprise ThermoCor insulating panels, commercially available from AcuTemp of Dayton, Ohio. In some embodiments, the vacuum-sealed insulating panel  12  (and/or component elements  12   a ,  12   b , thereof) may comprise vacuum insulating panels commercially available from Thermal Visions, Inc. of Granville, Ohio. Such panels may be characterized by an R value of substantially about 45R per inch of panel  12  thickness. 
     In some assembly  1  embodiments, the R value of various points within the panel assembly  1  may be varied by utilizing vacuum-sealed component elements  12   a ,  12   b  having a variety of different individual R value ratings. As one skilled in the art will appreciate, the R value of independent vacuum sealed components  12   a ,  12   b  may be effectively varied by selecting: different foam core materials  13 ; different relative thicknesses of the foam core materials  13 , different desiccant materials  14 , different relative amounts of desiccant materials  14 ; and/or combinations of such selections. Also, as shown in  FIG. 2 , each of the plurality of vacuum-sealed component elements  12   a ,  12   b  may define at least one channel and at least one tab  21   a ,  21   b  such that the plurality of vacuum-sealed component elements  12   a ,  12   b  may be operably engaged to form the vacuum-sealed insulating panel  12  by inserting the at least one tab  21   a ,  21   b  of a first vacuum sealed component  12   a  into a corresponding channel of a second vacuum sealed component  12   b . Thus, each of the plurality of vacuum-sealed component elements  12   a ,  12   b  may be interlocked to form a substantially-continuous vacuum-sealed insulating panel  12 . 
     According to various embodiments of the present invention, the first composite panel  10   a  and the second composite panel  10   b  may comprise various types of composite structural materials that may include, but are not limited to: fiber reinforced polymer materials; fiber reinforced polymer composites; solid laminates; pultruded or vacuum-infused sandwich panels (e.g., a panel having upper and lower skins with a core therebetween); pultruded panels (e.g., a panel having upper and lower skins with vertical or diagonal webs therebetween) and combinations of such composite structural materials. Exemplary core materials may include, but are not limited to: wood, foam, and various types of honeycomb. Exemplary polymer resin materials may include but are not limited to: thermosetting resins (such as unsaturated polyesters, for example), vinyl esters, polyurethanes, epoxies, phenolics, and mixtures thereof. The fiber reinforcing elements may comprise E-glass fibers, although other reinforcing elements such as S-glass, carbon aromatic polyamides, polybenzamidazoles, and aromatic polyimides), and other organic fibers (e.g., polyethylene and nylon) may also be used. Blends and hybrids of such materials may also be used as reinforcing elements. Other suitable composite materials that may be used as the reinforcing element include whiskers and fibers constructed of boron, aluminum silicate, or basalt. Exemplary composite panels  10   a ,  10   b  and methods of making such panels are disclosed in the following U.S. patents: U.S. Pat. Nos. 5,794,402; 6,023,806; 6,044,607; 6,108,998; 6,645,333; and 6,676,785, all of which are incorporated herein in their entirety. In addition, according to some embodiments, the structural components of the present invention (such as the first and second composite panels  10   a ,  10   b , for example) may also comprise a pultruded sandwich panel having a core and two laminated skins secured to opposite sides of the core. An exemplary commercial embodiment of a suitable sandwich panel is the TRANSONITE® composite panels available from Martin Marietta Composites of Raleigh, N.C. According to some embodiments, the core of the sandwich panel may be formed of a foam material with a plurality of fibers extending through the foam and connecting the two laminated skins secured to each opposing surface of the foam core. Furthermore, some assembly  1  embodiments of the present invention may further comprise a polyurethane coating material  17  disposed on an outer side of at least one of the first composite panel  10   a  and the second composite panel  106  for substantially sealing the assembly  1  and to reduce the chance of fluid ingress into the assembly  1 . 
     In order to form a unitary assembly  1 , some embodiments of the present invention may comprise an adhesive layer (not shown) disposed between the vacuum-sealed insulating panel  12  and at least one of the first composite panel  10   a  and the second composite panel  10   b  for operably engaging the composite panels  10   a ,  10   b  with the vacuum sealed insulating panel  12 . According to some such embodiments, the adhesive layer may comprise a methacrylate adhesive. In other embodiments, the adhesive layer may comprise a layer of contact adhesive (such as a spray-on contact adhesive, for example). Furthermore, such an adhesive layer may be disposed between one or more of the composite panels  10   a ,  10   b , the vacuum-sealed insulating panel  12 , and/or a structural bracket  30  (as described herein with respect to  FIG. 3 , for example) for forming a complete and/or substantially continuous insulated container (such as a refrigerated truck body, for example). 
     As shown in  FIG. 3 , the insulated composite panel assembly may further comprise one or more brackets  30  extending substantially perpendicularly from at least one edge of the insulated composite panel assembly (and/or one or more of the composite panels  10 ,  10   b  thereof) for receiving a side wall member  33  adapted to extend substantially perpendicularly from a complementary insulated composite panel assembly serving as a floor  31 . As shown generally in  FIG. 3 , the side wall member  33  may comprise a corresponding insulated composite panel assembly. According to various embodiments, the bracket  30  may be integrally formed with the insulated composite panel assembly and/or adhered (via a methacrylate and/or contact adhesive layer, for example) to one or more of the assembly components to form a substantially perpendicular junction between two insulated composite panel assemblies. 
     For example, as shown in  FIG. 3 , embodiments of the present invention may provide an insulated structure and/or insulated enclosure including, for example, a floor  31  comprising the insulated composite panel assembly (see  FIG. 1 , for example) and at least one wall member  33  comprising the insulated composite panel assembly. As described herein, the wall member  33  may be operably engaged with the floor member  31  to form a structural junction and/or other portion of an insulated structural assembly. According to some embodiments, a complete insulated structure (such as a truck body or refrigerated trailer) may be formed using various insulated composite panel assemblies as structural components including, but not limited to: floors  31 , wall members  33 , roof members (not shown), front walls (not shown), rear walls (not shown), and/or doors (not shown). As shown in  FIG. 3 , the floor  31  may be provided with composite panels  10  having a thickness that is greater than that of corresponding composite panels  10  forming the outermost layers of the wall member  33  such that the load-bearing capacity of the floor  31  is correspondingly greater than that of the wall member  33 . As shown in  FIG. 3 , the insulated structure may be joined using a bracket  30 . According to various embodiments, the bracket  30  may also comprise a relatively lightweight (compared to metal frames used in conventional insulated structures, for example) composite material that may include, but is not limited to: a pultruded tubing material; an extruded composite tubing; a composite tubing material comprising a polyurethane matrix and a plurality of E-glass fibers disposed within the polyurethane matrix; and combinations of such materials. 
     Various embodiments of the present invention may also provide a substantially complete insulated enclosure comprising a floor  31 , a plurality of wall members (see element  33 , for example) operably engaged with the floor  31 , and a roof (not shown) operably engaged with the wall members  33 . According to some such embodiments, each of the floor  31 , the wall members  33 , and the roof may comprise an insulated composite panel assembly  1 , as shown generally in  FIG. 1 . Furthermore, some embodiments may further comprise a cargo vehicle and/or cargo vehicle component comprising the insulated enclosure described herein, wherein the insulated enclosure may include, but is not limited to: a truck body; a trailer body; a shipping container; a boxcar body; and combinations of such enclosures. 
     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.