Abstract:
A product warming apparatus with at least one product holding container having a bottom surface. An enclosure includes at least one opening configured to receive the product holding container. A heat radiating plate is provided in thermal communication with and configured to receive heat from a heating element. The heat radiating plate includes a top surface disposed adjacent the bottom surface of the product holding container with the top surface of the heat radiating plate being spaced apart from the bottom surface of the product holding container to define a gap therebetween. A thermostatic controller is in thermal communication with the heat radiating plate for controlling a flow of heat to the heat radiating plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 USC 119 to U.S. Provisional Patent Application No. 60/948,574 filed on Jul. 9, 2007 the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to a product or food warming apparatus and, more specifically, to a product or food warming apparatus of the type which may be used, for example, in restaurant or food buffets. 
     2. Description of Background Art 
     Hot product or food storage and warming devices are known in the art. Such devices are used, for example, in restaurant buffets, by catering services, in cafeterias, and other applications. 
     Various types or classes of product or food warming devices have been devised. In one such class, heat is transferred to one or more product or food storage containers by means of steam (so-called steam tables). Steam tables require a substantial pan which contains a quantity of water which is kept warm by means of a gas burner, electric heater, or other energy source. The water is heated to boiling or near boiling, and heat is transferred to containers which are suspended above the water. The heat is transferred by a combination of radiation, convection and conduction. The level of water must be maintained in order for the device to function properly. The volume of water used typically makes such devices heavy and cumbersome. They are also relatively expensive to construct and operate. 
     Another class of product or warming devices rely upon “dry” heat provided, for instance, by electrical coils or strip heaters. Such coils or heaters typically operate at a relatively high temperature, often at or above the temperature at which the coil or strip glows red (e.g., 800 degrees F., 427 degrees C.). 
     Cooking and/or heating a product or food is often done with gas or electric heating elements operating at relatively high temperatures (i.e., much higher than the temperatures at which a product or food cooks or is maintained). High temperatures are used primarily to speed the cooking process, as such temperatures are not necessary for actual cooking of the product or food. Many products or foods begin to cook at temperatures of approximately 140 degrees F., 60 degrees C., and will char or burn at the relatively high operating temperatures of electric coils and heating strips. Absent the use of pressurized containers or other special devices, product or foods containing a substantial amount of water cannot be heated above 212 degrees F., 100 degrees C. The use of extreme heat to cook and/or warm a product or food typically requires stirring, agitation or other mechanism to prevent the product or food closest to the extreme heat source from drying out, burning, charring, overcooking, sticking or other detrimental effect. 
     Product or food storage, holding, or warming devices should hold product or food within the range of 160 degrees F., 71 degrees C. (the temperature at which most products or food is pasteurized) and 140 degrees F., 60 degrees C. (the temperature at which many product or foods cook). While an ideal product or food warming apparatus might operate with a heat source which is heated to and maintained within this range, such apparatus are relatively expensive and may not be suitable for all applications. Thus, there exists a need for a relatively simple, non-cumbersome, inexpensive apparatus for maintaining a product or food in the desired temperature range for sustained periods, using a heat source that is “dry” and which does not operate at extreme temperatures. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     In one embodiment, a product or food warming apparatus according to the present invention comprises at least one product or food holding container having a bottom surface, an enclosure having at least one opening configured to receive the product or food holding container, an electric heating element, and a heat radiating plate. The heat radiating plate is in thermal communication with, and receives heat from, the electric heating element. The plate has a top surface disposed adjacent the bottom surface of the product or food holding container. The top surface of the plate is spaced apart from the bottom surface of the container to define a gap therebetween. The apparatus further comprises a thermostatic controller which is in thermal communication with the heat radiating plate, and which controls a flow of electric current to the electric heating element. 
     In a particular embodiment, an area of the top surface of the heat radiating plate is substantially equal to or greater than an area of the bottom surface of the product or food holding container. In other embodiments, the plate  18  may have a smaller surface area relative to the product or food container  12 . In this or other embodiments, the thermostatic controller controls the flow of electricity to the electric heating element so as to maintain the top surface of the plate at a temperature below 450 degrees Fahrenheit, 232 degrees Celsius. In a particular embodiment, the thermostatic controller controls the flow of electricity to the electric heating element so as to maintain the top surface of the plate in a temperature range of 100 degrees Fahrenheit, 38 degrees Celsius to 450 degrees Fahrenheit, 232 degrees Celsius. 
     In certain embodiments, the heat radiating plate is formed of a conductive material, such as steel or aluminum. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1  shows a partial cross-sectional side view of one embodiment of a product or food warming apparatus constructed in accordance with the present invention; and 
         FIG. 2  shows a top view of the apparatus illustrated in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a partial cross-sectional side view of one embodiment of a product or food warming apparatus constructed in accordance with the present invention. With reference to  FIG. 1 , this illustrative embodiment includes an enclosure  10  having one or more openings  11  which receive, respectively, one or more product or food containers  12 . The enclosure may be made of various materials, but will most likely be made of a “product or food friendly” material, such as stainless steel. Interior surfaces of the enclosure may also be provided with insulation over all or portions of its extent. This feature is schematically illustrated by insulation layer  13  which covers the under side of the top of enclosure  10 . 
     Product or food containers  12  may be made of metal, plastic, glass, or other materials suitable for maintaining and serving hot product or food. Product or food containers  12  have bottom surfaces  22  which may be curved or may be substantially flat, or horizontal in the embodiment illustrated or may be of any shape, and side surfaces  23  which are substantially vertical. Lids (not shown) may be provided for one or more of product or food containers  12 . 
     Inside enclosure  10  is a heat source  14 . In this embodiment, heat source  14  is electrically powered, and has a heating element  16 , such as a coil, adjacent the surface of a heat conducting/radiating plate  18 . Plate  18  receives heat from heating element  16 , and is sized and configured to evenly distribute that heat throughout its conductive body. Heat is radiated from a top surface  20  of plate  18  to the bottom surfaces  22  of containers  12 . An air gap  24  is intentionally maintained between top surface  20  of plate  18  and bottom surfaces  22  of containers  12 . The presence of air gap  24  and the enclosed space assures that the primary mode of heat transfer between heat source  14  and containers  12  is radiation, as opposed to conduction and/or convection. The horizontal and vertical orientations of bottom surfaces  22  and side surfaces  23 , relative to top surface  20  of plate  18 , also assures that most of the heat transferred by radiation from plate  18  will be transferred to bottom surfaces  22 , and not to side surfaces  23 , of containers  12 . 
     A thermostatic controller  26  is provided, as illustratively shown. Thermostatic controller  26  is positioned so as to control the temperature of plate  18 . Specifically, thermostatic controller  26  can be used to control the surface temperature of the top surface  20  of plate  18  by controlling the flow of electricity to the heating element  16 . 
       FIG. 2  shows a top view of the warming apparatus of  FIG. 1 . Visible in  FIG. 2  are enclosure  10  and product or food containers  12 . Shown in dashed lines are openings  11  in enclosure  10  which receive containers  12 . The peripheries of openings  11  support containers  12  around their respective peripheries, as illustrated. 
     Also shown by dashed lines in  FIG. 2  is heat conducting plate  18 . As illustrated, the overall size of heat conducting plate  18 , including its top surface  20 , is relatively large when compared to the bottom surfaces  22  of product or food containers  12 . In other embodiments, the plate  18  may have a smaller surface area relative to the product or food container  12 . This is significant in that, due to the relatively large surface area of plate  18 , the temperature of top surface  20  can be maintained relatively lower (as compared to prior art “dry” product or food warming apparatus) while still transferring a sufficient amount of heat to bottom surfaces  22  of containers  12 . The lower temperature, coupled with the even distribution of heat, improves the overall performance of the apparatus. Product or food is maintained at the desired temperature with a lower risk of scorching, burning, spot cooking/sticking, or other undesired occurrences. 
     Also shown in dashed lines in  FIG. 2  is thermostatic controller  26  used to maintain top surface  20  of plate  18  at the desired temperature. An electrical cord  28  is illustrated as a means by which electric current is provided to thermostatic controller  26  and heating element  16 . Other means for connecting element  16  and controller  26  to a source of power may be used. 
     In operation, electrical power is supplied through thermostatic controller to heating element  16 , causing the temperature of plate  18  to rise. Plate  18  is formed of a conductive material and has sufficient thickness and mass so as to cause top surface  20  thereof to be maintained at a relatively uniform temperature. Because top surface  20  of plate  18  is a “dry” radiating surface, the temperature thereof can exceed 212 degrees Fahrenheit, 100 degrees Celsius, which is the maximum temperature that the surface of water can reach in a typical “wet” steam table warming apparatus. Due to the relatively large surface area of top surface  20 , as compared to bottom surfaces  22  of containers  12 , it is not necessary to heat the plate  18  to extreme temperatures (e.g., 750 degrees F., 399 degrees Celsius at which steel begins to glow red in the dark). Indeed, it will generally not be necessary to heat top surface  20  of plate  18  above a temperature of 450 degrees Fahrenheit, 232 degrees Celsius. In particular embodiments, it is anticipated that the temperature of top surface of the plate  18  will range from 100 degrees Fahrenheit, 38 degrees Celsius to 450 degrees Fahrenheit, 232 degrees Celsius. 
     Although the illustrated embodiment of  FIGS. 1 and 2  shows the area of top surface  20  of plate  18  as being substantially larger than the bottom surfaces of containers  12 , such is not required to achieve improvements over prior art devices. The heat radiated from top surface  20  of plate  18  and transferred to containers  12  is a function of the respective areas of top surface  20  and bottom surfaces  22  of containers  12 . Accordingly, the larger surface area of top surface  20  has advantages in terms of reducing the surface temperature needed to maintain product or food in containers  12  in the desired range. However, the width of air gap  24  is also a factor, as are the respective materials from which plate  18  and containers  12  are formed. Varying these factors to achieve optimal results for specific products or foods under specific circumstances can be done. In one embodiment of the present invention, the area of top surface  20  of plate  18  is substantially equal to or greater than the combined bottom surfaces  22  of containers  12 . By “substantially equal to” it is meant that the respective surface areas do not need to correspond exactly. That is, top surface  20  of plate  18  could be slightly smaller than the bottom surfaces  22  of containers  12 , while still achieving the advantages of the invention. However, the present arrangement is distinguishable over those arrangements which use relatively small heating elements operating at relatively high temperatures. Avoidance of relatively high temperatures, which are considered to be temperatures in excess of 700 degrees Fahrenheit, 371 degrees Celsius, is advantageous. 
     As explained above, electrical power supplied through thermostatic controller to heating element  16  causes the temperature of the heat radiating plate  18  to rise. The heat radiating plate  18  is formed of a conductive material and has sufficient thickness and mass so as to cause the top surface  20  thereof to be maintained at a relatively uniform temperature. The bottom surfaces  22  of the containers  12  are spaced a predetermined distance from the top surface wherein a product or food is maintained at a constant temperature regardless of minor fluctuations in the temperature of the plate  18 . More specifically, it is anticipated that the temperature of top surface of the plate  18  may be in the range of a first predetermined temperature from 100 degrees Fahrenheit, 38 degrees Celsius to 450 degrees Fahrenheit, 232 degrees Celsius while the temperature of the product or food within the container  12  will be maintained at a constant second predetermined temperature within a range below the preselected first predetermined temperature of the heat radiating plate  18 . 
     It is to be noted that in some embodiments the plate  18  may have a smaller surface area relative to the product or food container  12 . 
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates an embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.