Patent Publication Number: US-8113604-B2

Title: Modular insulation system for an environmentally controlled cabinet

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an insulated cabinet in which insulation is provided by modular panels which are attached to the exterior of the cabinet. 
     2. Description of the Related Art 
     Food service cabinets for heating, holding or proofing food are commonly used in the food service industry, for example in eateries such as restaurants or bakeries. These cabinets can control the temperature and/or humidity within the cabinet, and may be used to cook food, to keep prepared food at a certain temperature, or to provide the necessary heat and humidity for yeast products to rise, among other functions. 
     Conventional food service cabinets could benefit from improvements in a number of respects. For example, a food service cabinet may commonly be manufactured from aluminum as a lightweight and inexpensive material. However, in cabinets without special provision for insulation, the insulating properties of a material such as aluminum are not ideal. Consequently, an uninsulated cabinet may suffer from heat loss, resulting in inefficient energy consumption and deterioration of food quality, such as food being served at temperatures lower than desired. In addition, inadequate insulation may result in the exterior surface of the cabinet being hotter to the touch, making usage and movement of the cabinet less practical and potentially dangerous. 
     Moreover, if the cabinet is not properly or adequately insulated, the cabinet loses heat or cold at a greater rate, and therefore requires more energy to maintain a given temperature. This leads to additional expense on the operator of the cabinet, in addition to negative effects on the environment. 
     One potential method to address this problem is simply to manufacture the cabinet with insulation already provided. Conventionally, insulated cabinets are constructed by providing fiberglass insulation between the spaced wall panels of the cabinet. 
     However, this method may drive up manufacturing costs and the resultant cost to the consumer, since separate manufacture is required for non-insulated and insulated cabinets. In other words, since such insulated and non-insulated cabinets do not share a common core set of components, different machinery and processes may be needed to manufacture each body of the cabinet, leading to increased cost to the consumer. 
     Furthermore, conventional insulation methods may not provide protection from physical damage to the cabinet. For example, a cabinet with insulation interior to the cabinet walls will still be vulnerable from scratches, dents, and other physical damage to the exterior of the cabinet, particularly in the foodservice industry, where frequent contact with other objects (such as during cleaning or movement) may occur. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the foregoing by providing a cabinet with insulation panels attached to an exterior thereof, wherein the panels provide both insulation and protection to the cabinet. The panels are preferably formed in a double-wall construction with an insulating layer (such as air) therebetween, and are preferably formed of a sturdy material (such as a polyethylene or other plastic) able to withstand wear and tear that might otherwise damage an unprotected cabinet. 
     In one embodiment, the invention provides a modular insulation panel for insulation of a cabinet having lateral side walls, a back wall and a top wall. A main panel assembly is adapted to insulate a lateral side wall, and the main panel assembly is comprised of a framed double wall structure with a space therebetween for providing insulation to the lateral side wall. An auxiliary panel assembly is adapted to insulate the back wall, and the auxiliary panel assembly is comprised of a framed double wall structure with a space therebetween for providing insulation to the back wall. A hinge hingedly attaches the frame of the main panel assembly to the frame of the auxiliary panel assembly. 
     The foregoing provides an uninsulated cabinet with insulation. Moreover, the expense on the consumer may be reduced, and additional options in cabinet purchase may be made available to the consumer. It may also be possible to reduce the energy consumption of the cabinet, since the insulating walls may reduce the amount of heat (or cold) lost from the cabinet interior. Furthermore, it may be possible to replace panels in the field that are already in usage, as well as adding or subtracting panels if the consumer&#39;s needs change or if damage occurs to an original set of panels. Additionally, it may also be possible to reduce wear and tear on the cabinet walls, since the panels cover portions of the cabinet which would otherwise be exposed. 
     In another embodiment, the invention provides a modular insulation system, including a pair of modular insulation panels of the type described above, along with a top panel comprised of a framed double wall structure with a space therebetween for providing insulation to the top wall. 
     In another embodiment, a modular insulation panel is constructed for insulation of a cabinet having lateral side walls, a back wall and a top wall. A main panel assembly adapted to insulate a lateral side wall is molded, with the main panel assembly comprised of a framed double wall structure with a space therebetween for providing insulation to the lateral side wall. In addition, an auxiliary panel assembly adapted to insulate the back wall is molded, with the auxiliary panel assembly comprised of a framed double wall structure with a space therebetween for providing insulation to the back wall. A hinge is also molded for hingedly attaching the frame of the main panel assembly to the frame of the auxiliary panel assembly. 
     In still another embodiment, a cabinet having lateral side walls, a back wall and a top wall is insulated. A pair of modular insulation panels and a top panel are provided, wherein the top panel is integral with the first and second modular insulation panels and is comprised of a framed double wall structure with a space therebetween for providing insulation to the top wall. The respective auxiliary panel assemblies of the first and second modular insulation panels are connected to the back wall, and the top panel is connected to the top wall. 
     The main panel assembly may comprise plural tack-offs between the double walls for providing rigidity to the main panel. Additionally, the auxiliary panel assembly may comprise plural tack-offs between the double walls for providing rigidity to the auxiliary panel, and the top panel may comprise plural tack-offs between the double walls for providing rigidity to the top panel. 
     The space between the inner and outer wall of each framed double wall structure may be filled substantially with air, or the space between the inner and outer wall of each framed double wall structure may be filled at least in part by an insulative material. 
     The main panel assembly may cover substantially all of the lateral wall. The auxiliary panel assembly may cover substantially less than all of the back wall, and in one embodiment may cover approximately one half of the back wall. 
     The main panel assembly may include exterior recesses for mounting to other structures. 
     The hinge may be a living hinge, and the hinge may flex inwardly such that the angle between the main panel assembly and the auxiliary panel assembly is reduced. Additionally, the hinge can be constructed to bend by 90° around the lateral wall and back wall of the cabinet, and the hinge can be constructed to also lay flat. The hinge may or may not extend the full length of the interface between the lateral side wall and the back wall of the cabinet. 
     The modular insulation panel may include fastener bosses or other receptor mountings for receiving fasteners inserted through the cabinet to fix the modular insulation panel to the cabinet. 
     The modular insulation panel may be fabricated from plastic. An inner wall of each double wall structure may be made of the same material as an outer wall of the double wall structure, or an inner wall of each double wall structure may be a different material than an outer wall of the double wall structure. In one embodiment, an inner wall of each double wall structure can be comprised of a material more resistant to heat than the material of the outer wall of the double wall structure. 
     In another aspect, a modular insulation system may include one or more bumpers for the base of the cabinet. Each bumper may comprise a double wall structure with a space therebetween for providing insulation to the base of the lateral side wall, and plural tack-offs between the double walls for providing rigidity to the bumper. 
     In a modular insulation system, the frame of the main panel assembly may be integral with the face of the top panel. 
     The modular insulation system may include a second pair of modular insulation panels on top of a first pair modular insulation panels, for insulation of taller cabinets. 
     The modular insulation system may also include channel brackets which attach to the modular insulation panels. 
     The method of molding the modular insulation panel may be blow molding. 
     The cabinet may include a heating element for providing heat to the cabinet. 
     Additional objects, advantages, and features of the invention will become apparent to those skilled in the art upon examination of the following detailed description of preferred embodiments taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a perspective view of a modular insulation panel in accordance with one embodiment of the present invention. 
         FIG. 2  illustrates another perspective view of the modular insulation panel. 
         FIG. 3  illustrates a perspective view of the modular insulation panel in which the modular insulation panel lies substantially flat. 
         FIG. 4  illustrates a side elevational view of the modular insulation panel. 
         FIG. 4A  illustrates a partially cutaway perspective view of a hinge of the modular insulation panel. 
         FIG. 5  illustrates a front elevational view showing the outer side of a modular insulation panel. 
         FIG. 6  illustrates a back elevational view showing an inner side of the modular insulation panel. 
         FIG. 7  illustrates one cross-section of the modular insulation panel. 
         FIG. 8  illustrates another cross-section of the modular insulation panel. 
         FIG. 9  illustrates another cross-section of the modular insulation panel, taken from a side view of the main panel assembly. 
         FIG. 10  illustrates another cross-section of the modular insulation panel, taken from a side view of the auxiliary panel assembly. 
         FIG. 11  illustrates a front elevational view of a top panel, showing the outer side of the top panel. 
         FIG. 12  shows a cross-section of the top panel. 
         FIG. 13  illustrates an back elevational view of a top panel showing the inner side of the top panel. 
         FIG. 14  illustrates another cross-section of the top panel. 
         FIG. 15  illustrates a side elevational view of the top panel. 
         FIG. 16  depicts an exploded view of the exterior of a holding cabinet and a modular insulation system in accordance with one embodiment of the present invention. 
         FIG. 17  illustrates a perspective view of a cabinet equipped with a modular insulation system in accordance with one embodiment of the present invention. 
         FIG. 18  illustrates another perspective view of the cabinet equipped with the modular insulation system. 
         FIG. 19  illustrates one environment in which the present invention may be practiced. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a perspective view of a modular insulation panel, and  FIG. 2  illustrates a perspective view of the modular insulation panel rotated about 90° clockwise from the view of  FIG. 1 . In this regard,  FIG. 1  illustrates more of the outer side of the panel that would be visible to an observer of the cabinet, whereas  FIG. 2  illustrates more of the inner side of the panel which would contact the holding cabinet. 
     Briefly, modular insulation panel  100  is comprised of main panel assembly  110 , auxiliary panel assembly  120 , and hinge  130 . In a preferred embodiment, the entire modular insulation panel  100  is formed as one piece, for example by molding. In other words, while main panel  100  is comprised of main panel assembly  110 , auxiliary panel assembly  120 , and hinge  130 , it is preferred that the entire panel is manufactured at the same time and as a single piece. 
     Main panel assembly  110  is connected to auxiliary panel  120  by hinge  130 . Hinge  130  flexes inwardly such that the angle between main panel assembly  110  and auxiliary panel assembly  120  is reduced, forming the 90° angle between main panel assembly  110  and auxiliary panel assembly  120 . 
     Main panel assembly  110  is comprised of a double wall structure  117  with a space  118  therebetween, and plural tack-offs  112  are provided between the double walls of double wall structure  117  for providing rigidity to the main panel assembly  110 . A frame  119  runs around the outer wall of main panel assembly  110  near the edge of the main panel assembly. The space  118  between the inner and outer walls of the double wall structure  117  may be filled substantially with air, or may be filled at least in part by an insulating material. 
     As used in this description, “tack-off” refers a point or location where the inner and outer wall of the double wall approach each other or fuse together, such that there is less space or no space between the inner and outer walls of the double wall structure at the tack-off. Tack-offs can take many shapes. Some of the more common shapes are truncated cones or pyramids. Typically, it is preferable to have as much taper on the tack-off as possible, and to have a small contact area, such that there are not dimples or other marks on the visible exterior of the panel. Other variations on the dimensions and characteristics of tack-offs are of course possible. 
     In a preferred embodiment, the inner and outer walls of the panel are fused at the location of a tack off, in order to provide increased rigidity, as well as providing spacing between the inner and outer walls. In another embodiment, however, the walls may simply contact, if rigidity and other structural factors are not an issue. Such an embodiment would still provide spacing between the inner and outer walls of a panel, but would be less effective in increasing the rigidity of the panel. 
     Thus, the tack-offs are used to provide rigidity to a panel assembly. In particular, since main panel assembly  110  and auxiliary panel assembly  120  may be comprised of plastic or another lightweight material, and since the space between the inner and outer walls of the double walled structure of the panels may be filled with air (or another lightweight material), the panel may otherwise be less rigid than desired. Moreover, without tack-offs to space the inner and outer walls, the inner and outer walls of the panel may bounce or collapse against each other, creating an undesirable “drum-heading” effect. Therefore, in one aspect, tack-offs are a means of reducing cost and weight, while still maintaining stiffness between the panels. Specifically, the tack-offs provide additional rigidity and strength to the panel and avoid “drum-heading”, while still allowing these panels to be constructed of a lightweight material with little or no solid matter between the panel walls. 
     Main panel assembly  110  also includes upper recess  111  and lower recess  113 , for stacking main panel assembly  110  onto other modular panel assemblies. In this regard, the respective recesses leave projections at the edge of the main panel assembly, which may be termed “mating feet”. In more detail, upper recess  111  and lower recess  113  may aid in interlocking with other modular insulation panels to insulate taller cabinets, or to interlock with a bumper which can optionally be provided at the base of a cabinet. The interconnection between these various elements in an insulation system will be described in more detail below. 
     Additionally, main panel assembly  110  includes main panel bosses  114  or other receptor mountings. Main panel bosses  114  are indentations in the panel used for receiving fasteners (such as screws or nails) inserted through the cabinet to fix the main panel assembly to the cabinet. Main panel bosses  114  may be placed at various locations on main panel assembly  110 , and are not limited to the positions shown in any of the figures. Of course, the number of main panel bosses, the dimensions (i.e., size, depth, etc.) of the main panel bosses and other attributes can be varied widely according to application or preference. 
     Additionally, ridges  150  may be added to the outer wall of main panel assembly  110  for aesthetic purposes, and for certain functional advantages such as providing grips for easier movement of the cabinet. 
     Auxiliary panel assembly  120  is connected to main panel assembly  110 . As discussed above, auxiliary panel assembly  120  is connected to main panel assembly  110  via hinge  130 , and hinge  130  flexes inwardly such that main panel assembly  110  and auxiliary panel assembly  120  meet, forming a 90° angle. 
     Generally, auxiliary panel assembly  120  is comprised of a double wall structure  127  with a space  128  therebetween, and plural tack-offs  122  are provided between the double walls of double wall structure  127  for providing rigidity to the auxiliary panel assembly  120 . A frame  129  runs the outer wall of auxiliary panel assembly  120  near frame  130 . The space  128  between the inner and outer walls of the double wall structure  127  may be filled substantially with air, or may be filled at least in part by an insulating material. 
     Auxiliary panel assembly  120  also includes auxiliary panel bosses  124  or other receptor mountings for attaching auxiliary panel assembly  120  to the back wall of a cabinet. These mountings may be of a similar nature as main panel bosses  114 , or may be different dimensions as desired. 
     As with main panel assembly  110 , auxiliary panel assembly  120  may include ridges  150  for aesthetic or other purposes. 
     Hinge  130  attaches the frame of main panel assembly  110  to the frame of auxiliary panel assembly  120 . Although a number of possible hinges could be used, in a preferred embodiment, hinge  130  is a living hinge. A living hinge is a hinge with little or no moving parts, and generally is a thin section of material that bends to allow movement. In a preferred embodiment, hinge  130  is comprised of a plastic with increased fatigue resistance to accommodate repeated bending of the hinge. 
     As discussed above, hinge  130  bends inwardly, in order to allow main panel assembly  110  and auxiliary panel assembly  120  to meet, such that main panel assembly  110  and auxiliary panel assembly  120  form an angle near or at 90°. This function allows the modular insulation panel  100  to wrap around the side of a holding cabinet to the back of the holding cabinet, in a process that will be described in more detail below. In one embodiment, hinge  130  may be constructed such that when closed, the hinge extends across the full length of the interface between the lateral side wall and the back wall of a cabinet. In another embodiment, the hinge may not extend across the full length of this interface. 
     Additionally, hinge  130  may also be configured such that main panel assembly  110  and auxiliary panel assembly  120  lie flat, such as for easier storage and transportation. An example of this configuration is shown in  FIG. 3 . In this regard, manufacturing a living hinge which can also lie flat may allow for the respective parts of modular insulation panel  100  to be processed via blow-molding with less scrap material, simpler and less expensive tooling, and more consistent wall sections. This process will be explained in more detail below. 
     Of course, other hinge designs are possible depending on the particular needs of the consumer. For example, it may be possible to reverse the design of the hinge so that it bends 90° outwardly in the opposite direction. Put another way, using the view of  FIG. 1 , in this alternative embodiment auxiliary panel  120  would end up 180° from its position in  FIG. 1 , such that auxiliary panel  120  is pointed at the viewer instead of away from the viewer. This would result in a sharp inside corner, but leave a large 45° chamfer on the outside corner. Another possible way to achieve this effect would be to use two hinge points, each bending 45°. Of course, several variations are possible in addition to these examples. 
     Moreover, although hinge  130  is illustrated in the drawings and described herein, it should be realized that numerous methods and variations on the attachment of main panel assembly  110  and auxiliary panel assembly  120  are possible, including those without the use of a hinge. For example, main panel assembly  110  and auxiliary panel assembly  120  could be separate pieces, and each piece could be bolted or screwed on individually. In another embodiment, an adhesive could be used to attach individual panels, without a hinge at the corner. In still another embodiment the panel assemblies could be clamped or bracketed to the cabinet. It might also be possible to manufacture an entire panel assembly as a single piece, and then to slide or arrange the cabinet within the panel assembly. Numerous other embodiments and options are possible. 
     Modular insulation panel  100  may be formed from a number of materials, and preferably is molded as a single piece including constituent elements main panel assembly  110 , auxiliary panel assembly  120  and hinge  130 . Additionally, it is preferred that these elements are formed from the same materials using the same process. More specifically, in a preferred embodiment, modular insulation panel  100  is comprised of a plastic such as a high-density polyethylene. Other possible materials include polypropylene or acrylonitrile butadiene styrene (ABS), as well as some engineering-grade resins. While the respective inner and outer walls of the double wall structures  117  and  127  of main panel assembly  110  and auxiliary panel assembly  120  may be comprised of the same material, it may also be possible to construct the inner and outer walls from different materials. For example, an inner wall of each double wall structure could be comprised of a material more resistant to heat than the material of the outer wall of the double wall structure, or vice versa. 
     In addition, various manufacturing techniques may be used to form modular insulation panel  100 , including blow molding, rotational molding, and injection molding (gas-assisted or regular). However, in a preferred embodiment, the method of manufacture is blow molding. 
     In more detail, blow molding is a process in which melted plastic is extruded into a hollow tube typically referred to as a parison. A divided metal mold then closes around the parison and the plastic, and air is blown into the parison, inflating the plastic into the shape of the metal mold. Once the plastic has cooled sufficiently, the metal mold opens, and the finished component is released. Thus, in regards to the present invention, a panel-shaped metal mold may be used. This process may require modifications on the parison or configuration of the molding apparatus, but the general principle is the same. 
     As noted above, using a living hinge which can also lie flat allows for the respective parts of modular insulation panel  100  to be processed via blow-molding with reduced scrap material and simpler and less expensive tooling, and allows for more consistent wall sections. In more detail, it may be easier and simpler to mold a single flat piece, rather than one with angles or bends. In particular, molding the modular insulation panel at the angle to fit to the cabinet could be much more difficult, since the tooling and molding would have to account for the angle between the panels and the increased area taken up by the panels at this angle, among other possible difficulties. 
     In the case where the inner and outer walls of modular insulation panel  100  are made of different materials, different manufacturing methods may be preferred. For example, one possible method is twin-sheet thermoforming. Thermoforming is basically the process of heating a sheet of plastic until it is pliable then forcing it into a mold (either positive or negative by pressure or vacuum) to create the desired shape and cool the sheet. The materials can have different characteristics and are fused where the meet at the perimeter of the part. 
     Of course, other manufacturing techniques are possible. For example, rotational molding is a process in which a measured quantity of polymer is loaded into a mold, usually in powder form. The mold is then heated in an oven while it rotates, until all of the polymer has melted and adhered to the mold wall. The mold is then cooled, and the plastic part is removed from the mold. Thus, rotational molding is useful in the manufacture of mostly hollow parts, and accordingly could be used to manufacture modular insulation panel  100  in one embodiment of the present invention. 
     Injection molding is a common manufacturing technique in which molten plastic is injected at high pressure into a mold which is shaped in the inverse of the product&#39;s desired shape. The mold then opens and the product is ejected. Again, modifications on the process might be necessary or desired for production of modular insulation panel  100 , but the general principles would remain the same. 
     As a further consideration, the preferred material for manufacture may depend on which manufacturing process is chosen. 
     In a preferred embodiment, the thickness of the each respective inner and outer wall of main panel assembly  110  and auxiliary panel assembly  120  is about 0.100 inches, although variation due to manufacture is possible. Moreover, other desired thicknesses are possible based on characteristics of the heating cabinet such as size or heat output. Additionally, the desired thickness of the inner and outer walls may vary based on the particular plastic or material used to mold the wall, as well as the method of manufacture. 
     The dimensions of modular insulation panel  100  are sized to the target cabinet. Thus, main panel assembly  110 , auxiliary panel assembly  120  and hinge  130  may be manufactured to different dimensions depending on the dimensions of the cabinet. For example, main panel assembly  110  or auxiliary panel assembly  120  could be constructed to different dimensions to accommodate taller or wider (or shorter or thinner) holding cabinets or containers of varying sizes, or could be constructed with additional distance between the inner and outer walls to provide more space for insulation. 
     In general, it is preferred that the panel be molded in such a way that the panel is easy to clean and aesthetically pleasing, as well as easy to assemble. In this regard, the manufactured panel walls and insulating space between may allow for reduced weight and costs of the panels, while still reducing the energy required to maintain temperature in a holding cabinet by up to 30% or more. 
       FIG. 3  depicts a perspective view of a modular insulation panel in a flat position.  FIG. 4  illustrates a side elevational view of the modular insulation panel in the flat position, and  FIG. 4A  illustrates the hinge between the main panel assembly and auxiliary panel assembly in this position. 
     As seen in  FIGS. 3 and 4 , hinge  130  is not substantially bent, such that main panel assembly  110  and auxiliary panel assembly  120  lie flat. This configuration may be useful for storage or movement of the modular insulation panel  100  prior to attachment to a holding cabinet. For example, several modular insulation panels could be stacked flat in a box or other container, thus reducing the necessary amount of storage area. Thus, hinge  130  allows for main panel assembly  110  and auxiliary panel assembly  120  to lie flat, as well as bending to a right angle to wrap around a holding cabinet. As discussed above, the flat configuration may allow for processing via blow molding with reduced scrap material and simpler and less expensive tooling, and for more consistent wall sections. 
       FIG. 4A  depicts a partly cutaway perspective view of hinge  130  in more detail. As can be seen from the figure, hinge  130  runs along the entire height between main panel assembly  110  and auxiliary panel assembly  120 , and essentially acts as the interface between these panels. Additionally,  FIG. 4A  depicts the preferred embodiment in which hinge  130  is a living hinge, as can be seen from the small amount of material in the center of the hinge which bends to allow movement. Additionally, when hinge  130  bends inward, the inner sides of main panel assembly  110  and auxiliary panel  120  meet along the width of the hinge, such that the respective panel assemblies contact each other at this line. 
       FIG. 5  depicts a front elevational view showing the outer side of a modular insulation panel which would be seen by an observer, and  FIG. 6  illustrates a back elevational view showing an inner side of the modular insulation panel which would contact the cabinet.  FIG. 6  additionally serves as a guide for locating the views ( 7 ), ( 8 ), ( 9 ) and ( 10 ), as indicated by the view lines in the drawings. 
       FIGS. 7 to 10  illustrate various cross-sections of modular insulation panel  100 , taken respectively at the view lines ( 7 ), ( 8 ), ( 9 ) and ( 10 ) shown in  FIG. 6 . It can be seen that the space between the inner and outer wall of main panel assembly  110  and auxiliary panel assembly  120  is filled substantially with air. Additionally, the interior between the inner and outer walls of main panel assembly  110  and auxiliary panel assembly  120  near hinge  130  is also filled substantially with air, which may provide greater flexibility as the hinge  130  changes angle. However, it is also possible that another insulating material could be used to fill these spaces. 
     Additionally, the outer wall of main panel assembly dives steeply towards the inner wall near the edge of main panel assembly  110 , and also near hinge  130 . In other words, the outer wall indents into the inner wall, forming the recessed frame  119  which can be seen most clearly in  FIGS. 1 and 3 . This provides the frame  119  of the framed double wall structure  117  of main panel assembly  110 . Auxiliary panel assembly  120  also has a similar indentation for the frame  129  of its double walled structure  127  near the location of hinge  130 . While this frame design may be desired mainly for purposes of aesthetics, the thinner space between the inner and outer walls of main panel assembly  110  and auxiliary panel assembly  120  at the respective frames may provide for increased flexibility of hinge  130 . 
     The inner and outer walls of the respective panel assemblies meet at tack-offs  112  and  122 , such that there is not any space between the inner and outer walls at the location of the tack-off. As described above, it is preferred that the inner and outer walls of the panel are fused together at this location, such that there is no space between the inner and outer wall at the tack-off. Of course, other variations on the dimensions and size of the tack-offs are possible. 
     Fastener main panel bosses  114  extend almost completely through the space between the inner and outer walls of the double wall structure of main panel assembly  110 , to provide a more secure attachment for attaching fasteners through the main panel assembly. In particular, since the mounting is deeper, more screw threads can be engaged. Of course, other dimensions or types of fastener receptor mountings could also be implemented, and as such are not described here further. 
     At the edges of main panel assembly  110 , the material penetrates at a steeper angle, forming tack-offs at these locations. 
     A plurality of auxiliary panel bosses  124  are placed along the edge of the auxiliary panel assembly  120 . The auxiliary panel bosses  124  are indentations or openings in the structure of the panel, and are used for receiving fasteners (such as screws or nails) inserted through the cabinet to fix the cabinet to the auxiliary panel assembly  120 . The auxiliary panel bosses  124  may be placed at various locations on auxiliary panel assembly  120 , and are not limited to the positions shown in the figures. Of course, the number of auxiliary panel bosses, the dimensions (i.e., size, depth, etc.) of the bosses and other attributes can be varied widely according to application or preference. 
       FIGS. 11 through 15  illustrate various views of a top panel, which is integral with one or more sets of modular insulating panels to provide insulation to the top of the cabinet, in addition to the insulation provided to the back and lateral side walls by the modular insulation panels. 
       FIG. 11  is an front elevational view of a top panel, showing the outer side of a top panel as would be seen from an observer of the holding cabinet.  FIG. 13  illustrates an back elevational view of a top panel showing the inner side of the top panel which would contact the cabinet.  FIG. 15  illustrates an side elevational view of a top panel.  FIGS. 12 and 14  illustrate cross-sections of the top panel, at the view lines ( 12 ) and ( 14 ) shown in  FIG. 11 . 
     Top panel  200  is comprised of a double wall structure  217  with a space  118  therebetween, and plural tack-offs  212  are provided between the double walls of double wall structure  217  for providing rigidity to top panel  200 . A frame  219  runs around the outer wall of near the edge of top panel  200 . The space  218  in between the inner and outer walls of the double wall structure  217  may be filled substantially with air, or may be filled at least in part by an insulating material. 
     The tack-offs  212  are locations where the inner and outer walls of the double wall structure  217  meet. In a preferred embodiment, the inner and outer walls of the panel are fused at the location of a tack off, in order to provide increased rigidity and strength to the panel, as well as providing spacing to prevent unwanted “drum-heading” or contact between the inner and outer walls. In another embodiment, however, the walls may simply contact, if rigidity and other structural factors are not as much of an issue. 
     Top panel bosses  214  extend almost completely through the space between the inner and outer walls of the double wall structure of top panel  200 , to provide a more secure attachment when attaching fasteners through the cabinet to top panel  200 . Specifically, as noted above, the deeper insert allows for more fastener threads to be engaged. 
     Of course, many variations on the location and number of tack-offs  212  and top panel bosses  214  are possible. Additionally, receptor mountings other than bosses may be used. 
     Panel overhangs  211  can be seen on two sides of top panel  200 . These panel overhangs are used to interconnect top panel  200  to modular insulation panels  100 . In particular, each panel overhang  211  of top panel  200  interlocks with a respective top recess  111  to connect the modular insulation panel  100  and top panel  200 , such that both the lateral side walls and the top wall of a cabinet may be insulated. The panel overhang  211  also may provide a desired aesthetic to the insulation system, since much of the interconnection between modular insulation panel  100  and top panel  200  is hidden by panel overhang  211 . In this regard, in a preferred embodiment each of the (two) panel overhangs  211  would respectively integrate with a modular insulation panel  100 , such that each overhang connects to a respective modular insulation panel. This is because in a preferred embodiment, two modular insulation panels  100  are used to cover both of the lateral side walls and the back wall of a holding cabinet. This assembly will become more clear in view of additional figures and will be described in more detail below. 
     In a preferred embodiment, only the sides of top panel  200  which interlock with the main panel assembly  100  of modular insulation panel  100  have panel overhangs  211 . In other words, in a preferred embodiment, only the sides of top panel  200  which meet with the lateral side walls of a holding cabinet have panel overhangs  211 . However, a top panel could be constructed in which three or more sides of the top panel have panel overhangs. 
     Top panel  200  may also include ridges  250  on the outer side. These ridges may serve several purposes. For example, ridges  250  may serve to raise objects placed on top of the cabinet above the main surface. Additionally, the recess around ridges  250  could possibly be used to mount or locate a metal inlay for supporting hot objects. Ridges  250  may also provide a grip for easier movement of the cabinet. Moreover, ridges  250  may improve the aesthetics of the panel assembly. 
     Top panel  200  is preferably formed using the same materials and the same manufacturing method as used to form modular insulation panel  100 . Thus, in a preferred embodiment, top panel  200  is a high-density polyethylene, although other possible materials include polypropylene or acrylonitrile butadiene styrene (ABS), and certain resins. Additionally, while the inner and outer walls of the double wall structure  217  of top panel  200  may be comprised of the same material, it may also be possible to construct the inner and outer walls of top panel from different materials. For example, an inner wall of the double wall structure  217  could be comprised of a material more resistant to heat than the material of the outer wall of the double wall structure, or vice versa. If desired, top panel  200  may be comprised of a material different than that of modular insulation panel  100 . 
     In addition, various manufacturing techniques may be used to form top panel  200 , including blow molding, rotary molding, and injection molding (gas-assisted or regular). Sample methods were described above in respect to modular insulation panel  100 , and therefore will not be described again. In this regard, top panel  200  can of course be manufactured by a method different from that of modular insulation panel  100 . 
     As with modular insulation panel  100 , dimensions of modular insulation panel  100  are sized to the target cabinet. Thus, top panel  200  may be manufactured to different dimensions depending on the dimensions of the cabinet. For example, top panel  200  could be constructed to different dimensions to accommodate taller or wider (or shorter or thinner) holding cabinets or containers of varying sizes, or could be constructed with additional distance between the inner and outer walls to provide more space for insulation. Of course, in a preferred embodiment the dimensions of top panel  200  are sized to the dimensions of the set of modular insulating panels  100 , and all such panels are sized to the dimensions of the particular cabinet. 
       FIGS. 16 to 19  illustrate a modular insulation system in accordance with one embodiment of the present invention. The modular insulation system combines four modular insulation panels and a top panel, along with optional elements such as bumpers and channel brackets.  FIG. 16  depicts an exploded view of the exterior of a holding cabinet and a modular insulation system in accordance with one embodiment of the present invention.  FIGS. 17 and 18  show two perspective views of a cabinet  500  equipped with a modular insulation system of the present invention. For purposes of simplicity in regards to  FIGS. 16 to 18 , holding cabinet  500  will be described as “the cabinet”, although only the exterior of the holding cabinet is illustrated in these figures. 
     Briefly, four modular insulation panels  100  attach to holding cabinet  500 . As can be seen from the figure, one pair of left and right modular insulation panels  100  covers the holding cabinet laterally. In particular, using the hinge  130 , each modular insulation panel  100  wraps around the holding cabinet, and the respective auxiliary panels  120  of each modular insulation panel  100  meet in the center of the back wall of the holding cabinet. 
     However, a second set of modular insulation panels are also included in the embodiment shown. This is to accommodate the taller cabinet  500  vertically. More specifically, the height of a holding cabinet may be such that it is preferred to stack pairs of modular insulation panels vertically in order to achieve the desired insulation coverage. The pairs of modular insulation panels  100  interlock vertically, such that any gap in vertical coverage is reduced. In another embodiment, the cabinet may be short enough that only one pair of modular insulation panels is required. Of course, several variations are possible between the height of the panels and the number of panels required, based on the size of the holding cabinet  500  and the desired coverage. To insulate the top of the cabinet, top panel  200  is provided, and top panel  200  interfaces with the upper set of modular insulation panels. 
     A modular insulation system may also include bumpers  300 . Bumpers  300  are an optional accessory to the modular insulation system, and provide extra insulation and protection to the base of the cabinet. The bumper  300  may be constructed such that each lower recess  113  of the lower set of modular insulation panels  100  interfaces with the top of bumper  300 , and the modular insulation panels rest on the bumpers. In this regard, lower recess  113  can also be used to interface with another modular insulation panel  100 , as in the case of the upper set of modular insulation panels. 
     In more detail, a bumper  300  may comprise a double wall structure with a space therebetween for providing insulation to the base of the bottom wall, and plural tack-offs are provided between the double walls for providing rigidity to the bumper. Thus, the structure of bumper  300  may be similar to that of main panel assembly  110  and auxiliary panel assembly  120 . However, bumper  300  may also be a solid piece, or mostly hollow, or any number of other variations. Bumper  300  may be constructed of a plastic or other material as described above, and the methods of construction may also vary as described above. Accordingly, these characteristics of bumper  300  will not be described in detail. 
     Main panel bosses  114 , auxiliary panel bosses  124 , and top panel bosses  214  are used to attach the respective panels to holding cabinet  500 . In particular, screws, nails, or other fasteners are inserted through cabinet  500  into the bosses to attach the cabinet to the panels. In this regard, although an embodiment using hinged panels and fasteners is shown in  FIG. 16 , numerous methods of attaching the modular insulation panels are possible. For example, as described above, each piece could be bolted or screwed on individually, or an adhesive could be used to attach individual panels, or the panel assemblies could be clamped or bracketed to the cabinet. It might also be possible to manufacture an entire panel assembly as a single piece, and then to slide or arrange the cabinet within the panel assembly. 
     In the embodiment of  FIG. 16 , channel brackets  400  are placed at each interface between two modular insulation panels. More specifically, channel brackets  400  also cover the interface between the main panel assemblies  110  of the respective upper and lower modular insulation panels  100 , as well as the seam between the auxiliary panel assemblies  120  of the left and right modular insulation panels. The channel brackets  400  may then be placed at the seams to provide further protection or cleanability, as well as covering the interfaces between the panels. 
     Additionally, channel brackets  400  may be attached on top of top panel  200 . In such an embodiment, channel brackets  400  could also be used to support objects above the top surface of the cabinet, such as hot trays. Again, numerous variations in the method and hardware for attachment are possible. 
     In one aspect, a combination of the interlocking panels with the channel brackets  400  may help to reduce the gaps formed at joints and seams of panel interfaces, leading to reduced build-up of dirt and other particles. This may in turn may reduce the need for silicone or other sealants to close these gaps. In addition, certain molding techniques may have size variation inherent in the process, and this embodiment allows for these differences while still reducing the gaps between the panels. However, channel brackets  400  are not required to practice the invention. 
     As mentioned above, the modular insulation panels  100  are constructed to interface with each other, with top panel  200 , and optionally with bumpers  300 . In more detail, upper recess  111  can interface with either top panel  200  (as in the case of upper pair of modular insulation panels) or another modular insulation panel  100  (as in the case of the lower set of modular insulation panels). Conversely, lower recess  113  can be constructed to interface with bumper  300  (as in the case of the lower insulation panels) or another modular insulation panel  100  (as in the case of the upper insulation panels). Thus, the interfaces between the panels allow for modular insulation by adding or subtracting pairs of modular insulation panels  100 , and provide increased insulation to holding cabinet  500 . 
     If desired, the auxiliary panel may also be constructed to interface with a top panel or other modular insulation panel in a similar manner. 
     As can be seen, the modular insulation system provides insulation to the majority of the cabinet, except in the places where insulation may not be desired, such as the front of the cabinet where the door is placed, and the base of the back wall of the cabinet, where exhaust ports or other mechanical or electrical equipment may be located. 
       FIG. 19  illustrates an example embodiment of the present invention in which a full holding cabinet is illustrated. The structural and operational features of the holding cabinet shown can vary widely as appropriate to the given application. In particular, such cabinets may be constructed with varying height, width, or depth. For example, cabinets may be constructed to be one-half or three-quarters the size of the cabinet shown  FIG. 1 , as well as numerous other variations. 
     While the present invention has been described with a food service cabinet in mind, the present invention is not limited to such or to food service applications, but could be used for other types of containers, in commercial or non-commercial settings. The invention may also be modified to accommodate non-food service applications. 
     The foregoing provides an uninsulated cabinet with insulation. Moreover, the expense on the consumer may be reduced, and additional options in cabinet purchase may be made available to the consumer. It may also be possible to reduce the energy consumption of the cabinet, since the insulating walls may reduce the amount of heat (or cold) lost from the cabinet interior. Furthermore, it may be possible to replace or update panels in the field that are already in usage, as well as adding or subtracting panels if the consumer&#39;s needs change or damage occurs to an original set of panels. Additionally, it may also be possible to reduce wear and tear on the cabinet walls, since the panels cover portions of the cabinet which would otherwise be exposed. 
     One of ordinary skill in the art will realize that modifications and variations, including but not limited to those discussed above, are possible within the spirit and scope of the present invention. The invention is intended to be limited in scope only by the accompanying claims, which should be accorded the broadest interpretation so as to encompass all such modifications, equivalent structures and functions.