Patent Publication Number: US-6989517-B2

Title: Apparatus and method for heated food delivery

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 10/301,348 filed Nov. 20, 2002; which is a continuation of U.S. patent application Ser. No. 10/101,249 filed Mar. 18, 2002, now U.S. Pat. No. 6,555,799; which is a continuation of U.S. patent application Ser. No. 09/747,181 filed Dec. 21, 2000, now U.S. Pat. No. 6,384,387; which is a continuation in part of U.S. patent application Ser. No. 09/611,761 filed Jul. 7, 2000, now U.S. Pat. No. 6,433,313; which is a continuation in part of U.S. patent application Ser. No. 09/504,550 filed Feb. 15, 2000, now U.S. Pat. No. 6,353,208. The entire disclosure of each of the above applications is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a delivery apparatus for keeping an article warm during transport, a delivery apparatus assembly for charging a delivery apparatus, a heater for heating an article, and a method for delivering an article. 
     BACKGROUND OF THE INVENTION 
     Food products, such as pizza, are frequently prepared and cooked at a store location. The prepared food product is then delivered to a customer at a home or place of business. 
     A freshly cooked food product may be stored at the store location awaiting a delivery person&#39;s transportation of the food product to the customer. It is common to prepare pizza and store it in a cardboard box. The cardboard box is placed under a heat lamp awaiting pickup by a delivery person. The delivery person then stores the cardboard box in a thermally insulated carrying case for delivery to the consumer. Despite these methods, the product may lose heat during storage and transportation and the temperature of the product may decrease. If the product becomes too cool, it may become unacceptable to a customer. As a result, attention has been directed at techniques for keeping a food product warm after it has been cooked. 
     The prior art describes delivery apparatus that can be used to keep food items warm during transportation. For example the following U.S. Patents describe such prior art delivery apparatus: U.S. Pat. No. 5,999,699 to Hyatt; U.S. Pat. No. 5,932,129 to Hyatt; U.S. Pat. No. 5,892,202 to Baldwin et al.; U.S. Pat. No. 5,880,435 to Bostic; U.S. Pat. No. 5,884,006 to Frohlich et al.; and U.S. Pat. No. 5,750,962 to Hyatt. 
     SUMMARY OF THE INVENTION 
     A delivery apparatus is provided according to the invention. The delivery apparatus includes a container for holding an article to be delivered and a heater. The container includes a housing forming an interior area and an opening. The opening is provided with a size sufficient to allow movement of the article from outside the container to within the interior area, and from within the interior area to outside the container. The heater is constructed and arranged for placement within the interior area and is provided for heating the article. The heater includes an electrically conductive coil and an electrical resistance heating element. The electrically conductive coil provides an electric current when exposed to a magnetic field. The electrical resistance heating element is provided in electrical connectivity with the electrically conductive coil. 
     The electrically conductive coil can include a primary coil and a secondary coil. The primary coil can be used for energizing or powering the electrical resistance heating element. The secondary coil can be provided for energizing or powering the enunciating device that can be included as part of the delivery apparatus. The enunciating device preferably includes a temperature sensor for sensing temperature within the interior area of the container, a temperature display for displaying temperature conditions within the interior area of the container, and a controller for controlling the enunciating device. 
     A delivery apparatus assembly is provided according to the invention. The delivery apparatus assembly includes the delivery apparatus and an induction range. The induction range includes a magnetic field generator for generating a magnetic field from electrical energy. The induction range can include a power cord for connecting the magnetic field generator to an electrical current power source. Preferably, the induction range is constructed to operate based on a 120 volt line voltage input or a 220 volt line voltage input. 
     The delivery apparatus can be characterized as a “cordless” delivery apparatus because of the absence of a cord extending from the delivery apparatus outside of the container for attachment to a power source. Instead, power is generated within the heater by the electrically conductive coil provided in the presence of a magnetic field generated by the induction range. By providing the delivery apparatus as “cordless,” the user can avoid having to plug the delivery apparatus into an outlet for charging the heater. 
     A heater for heating an article is provided according to the invention. The heater includes an electrically conductive coil, an electrical resistance heating element, a heat sink, and a binder. The electrically conductive coil provides an electric current when exposed to a magnetic field created by an induction range. The electrical resistance heating element is provided for generating heat and is an electrical connectivity with the electrically conductive coil. That is, the electrically conductive coil provides current for operating the electrical resistance heating element. The heat sink is provided for storing heat generated by the electrical resistance heating element and releasing heat to heat an article. The binder is provided for holding the electrically conductive coil, the electrical resistance heating element, and the heat sink together. The binder can be provided as a separate container for enclosing and containing the heater components. Alternatively, the binder can be provided as a clip for holding the heater components together. 
     A method for delivering food is provided by the invention. The method includes a step of placing a delivery apparatus in a magnetic field to generate heat within the delivery apparatus, and then placing food within the interior area of the delivery apparatus. The method preferably includes a step of transporting the delivery apparatus containing food to a consumer. The step of placing food within the interior area preferably takes place after the apparatus is removed from the magnetic field, but can take place before the delivery apparatus is placed in the magnetic field or while the delivery apparatus is provided in the magnetic field. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective illustration of the delivery apparatus according to the principles of the present invention along with a pizza box partially inserted into the delivery apparatus. 
         FIG. 2  is a perspective view of the heater according to the principles of the present invention. 
         FIG. 3  is a sectional view of the heater according to the principles of the present invention. 
         FIG. 4  is an exploded view of the assembly of the heater according to the principles of the present invention. 
         FIG. 5  is a wiring diagram of the heater according to the principles of the present invention. 
         FIG. 6  is a block diagram of a controller according to the principles of the present invention. 
         FIG. 7  is a block diagram of an alternative controller according to the principles of the present invention. 
         FIG. 8  is an exemplary temperature versus time chart showing one possible control scheme according to the principles of the present invention. 
         FIG. 9  is an exploded perspective view of a preferred embodiment of the heater of the invention. 
         FIG. 10  is a perspective view of a preferred embodiment of a thermostat and fuse assembly of the invention provided in  FIG. 9 . 
         FIG. 11  is a perspective view of a pizza delivery bag that includes a temperature enunciating device according to the principles of the invention. 
         FIG. 12  is a sectional view of the pizza delivery bag of  FIG. 11  taken along line  12 — 12 . 
         FIGS. 13(   a )–( c ) is a diagrammatic view of exemplary visual temperature displays according to the principles of the invention. 
         FIG. 14  is a diagrammatic view of an exemplary audio temperature display according to the principles of the invention. 
         FIG. 15  is a functional block diagram illustrating operation of the enunciating device according to the principles of the invention. 
         FIG. 16  is a functional block diagram illustrating operation of the enunciating device according to the principles of the invention. 
         FIG. 17  is an exemplary electronic schematic diagram according to the principles of the invention. 
         FIG. 18  is an exemplary electronic schematic diagram according to the principles of the invention. 
         FIG. 19  is an exemplary electronic schematic diagram according to the principles of the invention. 
         FIG. 20  is an exemplary electronic schematic diagram according to the principles of the invention. 
         FIG. 21  is an exemplary electronic schematic diagram according to the principles of the invention. 
         FIG. 22  is an exemplary electronic schematic diagram according to the principles of the invention. 
         FIG. 22A  is an enlarged section of the electronic schematic diagram illustrated in  FIG. 22 . 
         FIG. 22B  is an enlarged section of the electronic schematic diagram illustrated in  FIG. 22 . 
         FIG. 23  is an exemplary electronic schematic diagram according to the principles of the invention. 
         FIG. 23A  is an enlarged section of the electronic schematic diagram illustrated in  FIG. 23 . 
         FIG. 23B  is an enlarged section of the electronic schematic diagram illustrated in  FIG. 23 . 
         FIG. 23C  is an enlarged section of the electronic schematic diagram illustrated in  FIG. 23 . 
         FIG. 23D  is an enlarged section of the electronic schematic diagram illustrated in  FIG. 23 . 
         FIG. 23E  is an enlarged section of the electronic schematic diagram illustrated in  FIG. 23 . 
         FIG. 23F  is an enlarged section of the electronic schematic diagram illustrated in  FIG. 23 . 
         FIG. 24  is an exemplary electronic schematic diagram according to the principles of the invention. 
         FIG. 25  is an exemplary electronic schematic diagram according to the principles of the invention. 
         FIG. 26  is an exemplary electronic schematic diagram according to the principles of the invention. 
         FIG. 27  is a sectional view of an alternative embodiment of a pizza delivery bag that includes a heater powered by induction according to the principles of the invention. 
         FIG. 28  is a diagrammatic view of components of a heater powered by induction and an induction range according to the principles of the invention. 
         FIG. 29  is an exploded perspective view of a heater powered by induction according to the principles of the invention. 
         FIG. 30  is a bottom view of a heater powered induction according to the principles of the invention. 
         FIG. 31  is a top cutaway view of a heater powered by induction according to the principles of the present invention. 
         FIG. 32  is a top view of a dual stacked coil according to the principles of the invention. 
         FIG. 33  is a top view of a dual planar coil according to the principles of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference now to the various figures in which identical elements are identically numbered throughout, a description of the preferred embodiment of the present invention will now be provided. The present invention will be described with reference to a delivery apparatus for food products. In particular, the present invention will be described with reference to a pizza delivery bag for transporting pizzas. It is customary to place cooked pizza in individual cardboard boxes. While the invention is being described in the context of a preferred embodiment, it will be appreciated that the invention can be used in a wide variety of applications for storing and/or transporting articles where it is desired to maintain the articles at an elevated temperature relative to ambient temperature. 
     Now referring to  FIG. 1 , a container  10  having an interior area  12  is shown with a heater  14  partially inserted into the interior area  12 . The container  10  can be any device having a plurality of walls forming an interior area  12 . In a preferred embodiment of the container the walls of the container are insulated. The container  10  also includes an opening  25  constructed for movement of the article  13  in and out of the interior area  12 . The interior area  12  can be a single compartment or it can be multiple compartments. 
     A preferred embodiment of the container  10  is shown in  FIG. 1  as pizza bag  11 . Pizza bag  11  includes bottom wall  18 , top wall  16 , back wall  20  and first and second sidewalls  22  and  24 . The walls  16 ,  18 ,  20 ,  22  and  24  of pizza bag  11  are insulated walls. 
     The container  10  also includes a flap  26  for covering the opening  25 . The flap  26  can be any device for covering the opening  25 . The purpose of the flap  26  is to prevent heat from escaping from the interior area of the container  10 . The flap  26  could be an extension of any combination of walls  16 ,  18 ,  20 ,  22  and  24 . The extension of any of these walls would be constructed to substantially cover the opening  25 . Alternatively, the flap  26  could be a separate piece that is fastened to the container  10  to cover the opening  25 . While the flap  26  does not have to have a fastener, it is preferred. The flap  26  could be an extension of top wall  16  zippered to an extension of bottom wall  18 , for example. 
     In a preferred embodiment the flap  26  is an extension  27  of top wall  16 . The extension  27  is draped down over the opening  25  and is slightly longer in the vertical direction than the opening  25 . The free end of the extension  27  wraps around to the bottom wall  18  and is attached to the bottom wall  18  with hook and loop fastener  28 . A mating hook and loop fastener is provided on the bottom wall  18 . 
     An article  13  is shown partially received by the container  10 . The article  13  can be any item that needs to be heated or maintained at a temperature above ambient temperature. The article  13  could be a food item or it could be a non-food item. In the case of food, the article  13  could be the food itself without any packaging or it could be the food and its associated packaging. In a preferred embodiment, the article  13  is a pizza box  21  including a pizza inside the pizza box  21 . The article  13  could also be two or more pizza boxes  21 . 
       FIG. 2  shows the heater  14  in the absence of the bag  11 . Heater  14  is any device that releases heat energy. Heater  14  can come in many different configurations. A preferred embodiment of the heater  14  is a “wrap heater”. A heater can be called a wrap heater when is wraps an article to be kept warm. That is, it wraps or heats at least two sides of an article to be kept warm. An exemplary wrap heater is described in U.S. application Ser. No. 09/267,182 which is assigned to Vesture Corporation the assignee of the above-identified application and which is hereby incorporated herein by reference.  FIG. 2  shows a preferred embodiment of the heater  14 , which is wrap heater  29 . 
     Wrap heater  29  includes a cover  35 . The cover includes anything that covers the heating grid and, if present, the heat sink of the heater  14 . The cover can be a number of things including but not limited to a bag with a single compartment for receiving the heating grid and heat sink. The cover can be a hard-shell container. 
     In a preferred embodiment, the cover  35  of the wrap heater  29  has a first heating sleeve  30  and a second heating sleeve  32 . An extension  34  is provided connecting the first heating sleeve  30  to the second heating sleeve  32 . The wrap heater  29  is provided for heating a food product such that the first heating sleeve  30  is on one side of the food product and the second heating sleeve  32  is on the other side of the food product. The first and second heating sleeves  30  and  32  and the extension  34  are preferably made of a 210 to 400 denier nylon. 
     Each of the first heating sleeve  30  and second heating sleeve  32  include an inside surface  15  and an outside surface  17 . The inside surface  15  provides a surface which is generally the closest surface of the wrap heater  29  to the article being heated. The outer surface  17  provides a surface that is closest to the bag  11  in which the wrap heater  29  is provided. The inside surface  15  and the outer surface  17  are preferably attached together along their edges  19  to contain the internal components and to prevent foreign matter from entering into the internal components of the heater  14 . Preferably, the inside surface  15  and the outer surface  17  are sewn together along their edges  19 . A hook and loop fastener  21  is sewn to the outer surface  17  of the receiving sleeves  30  and  32 . A hook and loop fastener is also sewn to the pocket side of the top wall  16 . The first hook and loop fastener  21  can be easily fastened to the hook and loop fastener  23  on the container thereby holding the wrap heater  29  in the interior area  12  of the bag  11 . An identical system of hook and loop fasteners can be used to attach the outside surface  17  of the second receiving sleeve  32  to the pocket side of the bottom wall  16  of the bag  11 . 
     The power cord  38  is adapted to be plugged into a power source with plug  40 . The power source may be an alternating current source such as a wall outlet or it may be any other power source including a direct current power source. The power cord  38  is attached to the wrap heater  29  via a sleeve  42  that is stitched to the second heating sleeve  32 . The sleeve  42  is preferably of large enough diameter such that the plug  46  can be pulled through the sleeve for easy removal from the wrap heater  29 . The power cord  38  rounds a corner of the wrap heater  29  and travels along the extension  34 . A sleeve  44  holds the power cord  38  to the extension  34 . The sleeve  44  is preferably attached to the extension with a fastener such as a hook and loop fastener so that cord  38  and plug  46  can easily be removed from the wrap heater  29 . A female plug  46  and the male plug  48  connect the cord  38  to cord  50 . The purpose of the plugs  46  and  48  are to allow for replacement of the cord  38  along with plugs  46  and  40  without having to replace the entire wrap heater  29 . Additionally, the ability to remove cord  38  with associated plugs  40  and  46  allows for easy replacement with different cords and plugs that can be used in countries with different power sources. 
     Cord  50  is connected to the electronics residing in a box  64  (shown in  FIG. 3 ) that resides in sleeve  36 . The wrap heater  29  includes the controller sleeve  36  in which a controller or a portion of a controller (not shown in  FIG. 2 ) may be placed. Sleeve  36  is accessible from the food product receiving area of the bag  11  via an opening that is normally secured shut with a hook and loop fastener. 
     First and second light sources  52  and  54  are shown attached to the second heating sleeve  32 . The light sources  52  and  54  are attached to the second heating sleeve  32  via grommets (not shown). 
       FIG. 3  shows more detail of the wrap heater  29  of  FIG. 2 . In  FIG. 3  the wrap heater  29  is laid open such that first heating sleeve  30 , second heating sleeve  32  and extension  34  are in the same plane. The first heating sleeve  30  defines a pocket  56  and the second heating sleeve defines a pocket  58 . In the normal operation of the wrap heater  29 , assemblies  60  and  62  are located in the pockets  56  and  58  respectively. In normal operation the pockets  56  and  58  would be sewn shut with the assemblies  60  and  62  located inside the pockets  56  and  58  respectively so that the assemblies  60  and  62  cannot slide out. In  FIG. 3  the assemblies  60  and  62  are shown outside the pockets  56  and  58  for ease of illustration. 
     The first heating sleeve  30  is separated from the extension  34  by a first crease  31 . The second heating sleeve  32  is separated from the extension  34  by a second crease  33 . The creases  30  and  32  allow the wrap heater  10  to generally wrap an article for heating. In the case of a pizza provided in a pizza box, the first sleeve  30  can be provided covering the top of the pizza box, and the second heating sleeve  32  can be provided underneath the pizza box. The creases  31  and  33  also result in a pocket  57  located in the extension  34 . Pocket  57  preferably contains a layer of polyester insulation. A layer of polyester insulation is also placed in the pockets  56  and  58  between the respective assemblies  60  and  62  and respective outer surfaces  17 . This insulation further prevents heat loss to the outside environment. 
     Power cord  50  that provides electrical power to the wrap heater  29  is connected to the electronics in box  64 . The box  64  is preferably an aluminum box with ventilation holes. The box  64  protects and supports a circuit board contained within box  64 . The circuit board contained in box  64  includes electrical components and circuitry that make up a part of the controller. The term “controller” is not limited to the electronics located in the box  64  but could also include other components such as sensors and switches that will be described below. Furthermore, the term “controller” does not require all of the elements in the box  64  but could comprise a smaller subset of elements. 
     While a brief description of the electrical connections is provided here in conjunction with  FIG. 3 , a more detailed discussion is set forth below in the discussion of  FIG. 5 . Two wires  70  and  72  connect the first light source  52  to the electronics in box  64 . Likewise, two wires  74  and  76  connect the second light source  54  to the electronics in the box  64 . The wires  70 ,  72 ,  74 , and  76  can travel along the bottom of assembly  62  between the assembly  62  and the outer surface  17 . Preferably the wires  70 ,  72 ,  74  and  76  travel between the assembly  62  and the inside surface  15 . When the assemblies  60  and  62  are placed inside the pockets  56  and  58 , the light sources  52  and  54  can be seen through the window  51  at holes  53  and  55 . The window  51  is preferably a clear flexible plastic material that is sewn to the inside surface  15 . The light sources are preferably light emitting diodes (LED) with the first light source  52  being a red LED and the second light source  54  being a green LED. Each light source  52  and  54  has at least a first state in which a first level of light intensity is released and a second state in which a second level of light intensity is released. In a preferred embodiment, the first state of both light sources  52  and  54  is equivalent to the LED being turned on such that it releases light. In a preferred embodiment, the second state of both light sources  52  and  54  is equivalent to the LED being turned off such that no light is released. 
       FIG. 4  illustrates an exploded view of the elements of the assembly  62 . Note that in the preferred embodiment the assembly  60  is very similar to assembly  62 . Therefore, the discussion of assembly  62  below can be applied to assembly  60 . 
     Assembly  62  includes a heating grid  80  that is preferably a mica high watt density heating grid. For purposes of the present invention the term “high watt density heating grid” defines a heating grid with a watt density equal to or greater than 2.5 watts per square inch. In a preferred embodiment the heating grid  80  is a 300 watt mica heating grid with an area of 100 square inches (10 inch by 10 inch square) resulting in 3.0 watts per square inch. The heating grid can be constructed of other materials that can handle the high watt density required for this invention. 
     Assembly  62  also includes a heat sink  84  that is in thermally conductive contact with the heating grid  80  so that a portion of the heat generated by the heating grid  80  flows into the heat sink  84 . The heat energy in the heat sink  84  is then released for heating the article such as the pizza. The heat sink should have a phase change temperature of at least 300° F. It is desired that the heat sink have a specific heat on the order of the specific heat of polycarbonate or higher. It is also a design consideration to have a heat sink with a relatively low density. For example, a number of metals are too dense and thus would result in a very heavy delivery apparatus if used as the heat sink. Some exemplary materials that might be used as a heat sink are aluminum and resins or polymers. The heat sink  84  is preferably made of polycarbonate. 
     The heat sink  84  can be any shape including a square, rectangle, circle or any other shape. The polycarbonate heat sink  84  is preferably in the shape shown in  FIG. 4 . This preferred shape of the polycarbonate heat sink  84  is essentially a square central portion  85  with four wings  87 , one wing extending from each corner of the square central portion. The advantage of the wings  87  is that they extend over the corners of the cardboard box that holds the pizza. The corners of the cardboard box are the strongest part of the cardboard box. Therefore, the wings  87  in conjunction with the stronger corners of the cardboard box prevent the heat sink from pressing against the central part of the box. Pressure on the central part of the box would cause pressure into the pizza itself including the cheese resulting in a less desirable food product. 
     The ridges  89  are depressed as compared to the rest of the polycarbonate heat sink  84  and these ridges  89  become further depressed as they slope toward the center  91  of the polycarbonate heat sink  84 . That is, the center  91  of the polycarbonate heat sink  84  is closer to the heating grid than the rest of the polycarbonate heat sink  84 . This depression in the heat sink  84  accounts for stresses caused by thermal expansion and contraction of the heat sink  84 . The depression prevents materials from warping and therefore restricting the space in the cover  35 . 
     The layer  86  directs the heat energy from the heating grid  80  toward the polycarbonate heat sink  84 . The layer  86  is preferably two layers of fiberglass matting, such as maniglass material, each having dimensions the same as the heating grid  80  such as 10 inches by 10 inches. Each of the two maniglass layers is preferably about one eighth of an inch thick. An advantage of using maniglass for layer  86  is that maniglass is capable of withstanding high temperatures without emitting unpleasant odors. 
     The layer  88  is a structural element that holds all the elements of the assembly  62  together. Preferably the layer  88  is a sheet of aluminum. The dimensions of the layer  88  are generally the same as the square formed by the central portion of the heat sink  84  that is 12 inches long by 12 inches wide. The layer  88  further includes four flaps  90  that are also preferably made of aluminum. The flaps  90  extend beyond the square shape of the layer  88  and are made to wrap around the outer edge  92  of the heat sink  84  so that the heat sink  84  and the layer  88  cover and hold together all the elements of the assembly  62 . In  FIG. 4 , adhesive tape  94  is shown covering the outer edges  92  of the heat sink  84 . In the final assembly  62 , the flap  90  wraps around the outer edge  92  and then the tape  94  is adhesively attached to cover the flap  90  and a portion of the heat sink  84  as an additional means for keeping the flaps  90  from pulling apart from the heat sink  84 . The tape  94  is preferably a 7 inch strip of TYCO 225 FR tape. 
     A temperature sensor  100  is electrically connected to the box  64  by wires  102  and  104 . The temperature sensor  100  is any device that is capable of measuring the temperature of the heating grid such that the temperature information can be utilized by a controller. 
     The temperature sensor  100  is preferably a thermister. The thermister is preferably rated between 3 kilo ohms and 100 kilo ohms. A preferred embodiment utilizes a 10 kilo ohm thermister. In a preferred embodiment there is no sensor in the assembly  60 . A thermister  100  in the assembly  62  is sufficient to provide the requisite temperature feedback for proper control of the wrap heater  29 . However, there could be a sensor in the assembly  60 . The thermister  100  is attached to the heating grid  80  by tape  106  and  108 . Fuses  112  and  114  are in series and are also attached to the heating grid  80  by the tape  106  and  108 . The wires  102 ,  104  and others in the assembly  62  lead out of the assembly  62  through heat shrink tube  101  that is taped to the polycarbonate heat sink  84  with tape  103 . Tape  103  is preferably TYCO 225 FR tape. 
     It should be appreciated that while a preferred embodiment of the heater includes heating grids in both sleeves as shown in wrap heater  29 , the heater  14  of the invention can be provided so that only one sleeve provides heating. Furthermore, it should be appreciated that the amount of heating provided by both sleeves can vary. That is, the first sleeve can provide greater heating than the second sleeve, or vice versa. 
       FIG. 5  is a wiring diagram of a preferred embodiment of the invention. The heating grids  80  and  120  of assemblies  62  and  60  respectively are shown. The box  64  that contains electronics to be discussed further below is also shown. 
     In operation, thermister  100 , thermal fuse  112  and thermal fuse  114  are attached to the heating grid  80  with tape (not shown). The thermal fuse  112  is preferably a 192° C. thermal fuse. The thermal fuse  114  is preferably a 184° C. thermal fuse. Exemplary thermal fuses  112  and  114  are thermal fuses made by Thermodisk Corporation. However, other fuses may be used including thermal fuses having different temperature set points and made by different manufacturers. Two fuses of slightly different temperature set points are used as an extra precaution. If one of the thermal fuses malfunctions or is defective, the other fuse provides the necessary protection against overheating. By using fuses with different temperature set points, it can be guaranteed that the two fuses  112  and  114  were manufactured in different batches, thereby reducing the likelihood of a defect in both. 
     The connectors  122 ,  124  and  126  connect the fuses into the circuit. Connectors  122 ,  124  and  126  are preferably crimp style connectors such as Stacon crimp connectors. 
     In a preferred embodiment, there is no thermister on the heating grid  120 . However, thermal fuses  128  and  130  are connected to heating grid  120  in the same fashion as the thermal fuses  112  and  114  on heating grid  80 . Thermal fuse  128  is preferably a 192° C. fuse and thermal fuse  130  is preferably a 184° C. fuse. Each of the thermal fuses  112 ,  114 ,  128  and  130  is preferably wrapped in either a polyamide film such as Kapton tape by E. I. Du Pont De Nemours and Company or fiberglass sleeving material. The polyamide tape or fiberglass sleeving material is used for electrical insulation. 
     From  FIG. 5  it can be seen that the fuses  112  and  114  attached to the heating grid  80  are in series with the fuses  128  and  130  attached to the heating grid  120 . Therefore, if any fuse is blown, power to both heating grids  80  and  120  is shut down. 
     Terminals  132 ,  134 ,  136  and  138  are connected to the box  64 . Power comes in via wire  140  to terminal  136 . Power flows out of the box  64  at terminal  134 . Wires  142  and  144  carry power to the mica heating grids  80  and  120 . The blocks  146  and  148  each represent a butt splice. Neutral wires  150  and  152  exit the mica heating grids  80  and  120  respectively and return to terminal  132 . Terminal  138  is connected to neutral wire  154  that is the neutral return wire to plug  48 . Wire  156  is the ground wire and is attached to the aluminum box  64  with a fork terminal  158  and a screw  160 . 
       FIG. 6  is a block diagram of a preferred embodiment of a controller of the invention and its interaction with a heating grid and power source. It should be appreciated that the term “controller” as used in this application could mean the combination of a number of elements and that not all the elements included in the controller  198  of  FIG. 6  are required to be in a “controller”. The controller  198  in  FIG. 6  is but one embodiment of the term “controller”. Note also that  FIG. 7 , discussed below, is an alternate embodiment of a controller in accordance with the present invention. 
     The controller  198  includes a central processing unit 200 that receives power from the power source  202 . The central processing unit  200  could be any electronic control device capable of receiving information from a sensor and determining what signals to provide to one or more other electronic elements to perform some task. As an example only, the other electronic element could be a switch that the central processing unit  200  directs to turn off the electrical power from the power source  202  to the heating grid  208 . As a further example only, the other element could be an energy storage device that the central processing unit  200  directs to energize a light source. A preferred embodiment of the central processing unit  200  is a microprocessor located on the circuit board in the box  64 . 
     The central processing unit is electrically connected to a switch  204 . Switch  204  may be any device capable of receiving a signal from the central processing unit to allow or disallow energy to flow from the power source  208  to the heating grid  208 . The switch  204  must also be capable of then performing the operation of allowing or preventing energy to flow from the power source  208  to the heating grid  208 . A preferred embodiment of switch  204  comprises solid-state electronics such as one or more transistors. 
     The temperature sensor  206  is in thermal communication with the heating grid  208 . The temperature sensor  206  is also in electrical communication with the central processing unit  200 . The temperature sensor is any sensor capable of communicating the temperature of the heating grid  208  to another device. For example, the temperature sensor  206  communicates the temperature of the heating grid  208  to the central processing unit  200 . As stated above, in a preferred embodiment the temperature sensor  206  is a thermister. 
     Energy storage device  210  is electrically connected to the light source  212  for providing energy to the light source  212  even when the heater is not connected to the power source  202 . Energy storage device  210  is also in electrical communication with the central processing unit  200 . Any device capable of storing energy and releasing that energy in the form of electricity qualifies as an energy storage device  210 . In a preferred embodiment the energy storage device  210  provides energy to the light source  212  upon command by the central processing unit  200 . The energy storage device  210  is preferably a set of capacitors provided on the circuit board in the box  64 . An alternative embodiment of the energy storage device  210  would be a rechargeable battery. The presence of energy storage device  210  attached to the delivery apparatus for powering the light sources is very advantageous in that the indicating lights can provide information even after the delivery apparatus is disconnected from the power source. 
       FIG. 7  is a block diagram of an alternate embodiment of a controller of the present invention. The controller  241  is shown. A power source  242  is connected to a relay  244 . The relay  244  is any device capable of allowing energy to flow through for a specified period of time and then preventing energy to flow through after that specified time has passed. The relay  244  is preferably a timer control latching relay. The relay  244  allows a predetermined amount of energy to go to the heating grid  246 . In a preferred embodiment the timer control latching relay is set for 2.5 minutes before the energy to the heating grid is interrupted. 
     The fuse  248  is for security to prevent overheating of the heating grid  246 . In a preferred embodiment, the fuse  248  is a 184° C. thermal fuse. 
     The sensor  250  is also a security component that prevents the temperature of the heating grid from going over a particular temperature. Sensor  250  is any device that is capable of opening the circuit when a particular temperature is reached. In a preferred embodiment, the sensor  250  is a thermostat. In a more preferred embodiment, the sensor  250  is a normally closed thermostat that opens the circuit at 140° C. The thermostat  250  is in thermal communication with the heating grid  246 . If the temperature of the heating grid  246  goes over 140° C. the thermostat  250  prevents further energy from passing to the heating grid  246 . 
     Heating grid  246  is preferably a mica heating grid but could be other types of heating grids as discussed above with respect to other embodiments. In a preferred embodiment heating grid  246  is capable of high watt densities of greater than 2.5 watts per square inch. 
     Control of the light sources  254  and  256  is shown in the rest of  FIG. 7 . Transformer  252  reduces the voltage from source voltage to a voltage appropriate for the light sources. In a preferred embodiment, the power source is at 120 volts and the transformer reduces the voltage to 5 volts. 
     The transformed down power then passes through the energy storage device  258 . Relay  260  is any device which can receive a signal from a thermostat or other sensor and switch one or more lights on and off according to a particular protocol that results in providing information to the user regarding the status of the heater. In a preferred embodiment the relay  260  is a single pole double throw thermostat driven relay. 
     The relay  260  is driven by sensor  262 . Sensor  262  is in thermal communication with the heating grid  246 . Sensor  262  is any device capable of determining the temperature of the heating grid  246  and communicating that temperature information on to the relay  260 . In a preferred embodiment the sensor  262  is a normally open 66° C. thermostat. The normally open 66° C. thermostat is open when the temperature is below 66° C. When the temperature of the heating grid  246  goes above 66° C. the thermostat  262  closes the circuit. 
     The relay  260  drives light sources  254  and  256  according to the signals the relay  260  receives from the thermostat. The light sources  254  and  256  are preferably a red LED and a green LED. It should be appreciated that it is within the scope of this invention to have only one light source or to have more than two light sources. The choice of how many light sources depends on what information is desired to provide to the user. 
     The operation of the device in  FIG. 7  is now described. The relay  244  allows power to pass through the relay  244  for a set period of time, preferably about 2.5 minutes. During the 2.5 minutes the heating grid is charging and therefore the temperature of the heating grid  246  is rising. If the temperature goes above 140° C., the thermostat  250  opens the circuit to prevent the heating grid  246  from receiving further electrical energy. As a precaution the fuse  248  will also open the circuit if the temperature of the heating grid rises above 184° C. 
     The 120 volts from the power source  242  is transformed to 5 volts by transformer  252 . The energy storage device is charged during the approximately 2.5 minutes that the timer allows charging of the heating grid  246 . 
     When the relay  244  opens the circuit after 2.5 minutes, the heating grid  246  gradually cools down. The heating grid  246  will not heat up again until the user restarts the cycle by resetting the relay  244 . 
     Before charging of the heating grid begins, the red and green LED&#39;s are off. When the charging is proceeding and the temperature of the heating grid  246  is below the 66° C. set point of the thermostat  262 , the relay  260  causes the red light to be on. When the temperature of the heating grid exceeds 66° C., the relay  260  causes the red light to go off and the green light to go on. When the temperature of the heating grid  246  drops below 66° C., the relay  260  causes the green LED to go off and the red LED to go on. At this stage, there is no power reaching the transformer  252  and so there is only a limited amount of energy available as stored in the energy storage device  258 . After the energy in energy storage device  258  is expended, both light sources go off. 
     The control operation of the wrap heater  29  with respect to the embodiment shown in  FIGS. 1–6  is now explained in conjunction with  FIG. 8 .  FIG. 8  is a graph of temperature of the heating grids  80  and  120  versus time. This graph was generated from an experimental measurement of the preferred embodiment of the invention described above. The line in the graph using diamond shapes for data points is one possible temperature curve of the heating grid  80  and the line using square data points is one possible temperature curve of the heating grid  120 . The graph of  FIG. 8  is not intended to be limiting to the invention disclosed herein. Rather the graph of  FIG. 8  is merely an example of a possible control scheme. The notations along the time axis for “AC OFF” and “AC ON” represent the time at which the power to the heating grids was turned off and on respectively. 
     In a preferred embodiment, the temperature of the heating grids  80  and  120  cycle from an initial temperature that is room temperature to a higher temperature and then the temperature is allowed to drop to a lower temperature while the power to the heating grid is turned off. Preferably this cycle from a higher temperature to a lower temperature will occur three times and then the controller directed by the microprocessor will turn the heating grids  80  and  120  off and leave them off until a user directs the heater to begin charging again. The user so directs the heater to begin charging again by unplugging the plug  48  from the power outlet and then plugging plug  48  back into the outlet. The shut off of power to the heater after three cycles is to prevent excessive use of electricity in the case when a heater is unintentionally left on for an extended period of time. Only one cycle from higher temperature to lower temperature is shown in  FIG. 8 . 
     As can be seen, each cycle from AC OFF to AC ON is 30 minutes. In a preferred use of the invention the wrap heater  29  is removed from the power source at the same time the power is turned off (AC OFF). Then the heating grids continue to heat up to approximately 240° F. The polycarbonate heat sink  84  then releases heat energy for an extended period of time. Thirty minutes after the AC is turned off the temperature of the heating grids is approximately 170° F. Using heating grids  80  and  120  with a watt density of 3.0 watts per square inch, it takes 2.5 minutes from power on to power off to accomplish a higher or peak temperature of 240° F. The difference between the peak temperature and the lower temperature is referred to as the “hysteresis”. In the example provided, the hysteresis is 240°−170°=70°. 
     It is noted that the use of a high watt density heating grid in the prior art devices would present significant problems. Prior art delivery apparatus use thermostats that are not capable of providing a large hysteresis. Thermostats typically provide a hysteresis of 2°–10°. With a high watt density heating grid of 3.0 watts per square inch, the overshoot would be much less controllable and there would certainly be a high risk that the thermostat would fail to perform consistently to prevent heat sink degradation. For example, in U.S. Pat. No. 5,880,435 entitled “Food Delivery Container”, the replacement of the heating element with the high watt density heating grid of the present invention would result in a high risk of melt down of the polyethylene material. The thermostat of U.S. Pat. No. 5,880,435 would be in danger of failing because the large current flow that is required for a high watt density heating grid would likely cause arching at the bimetallic contact points. Additionally, high watt density heating grid would cause unacceptable overshoot by the thermostat when the heater is powered up. 
     A preferred method of using the delivery apparatus in accordance with the principles of this invention will now be described. The wrap heater  29  is placed in the pizza bag  11  and attached to the pizza bag  11  as discussed above. If it is desirable to clean the pizza bag  11  or wrap heater  29 , then the heater can be removed from the interior area  12  for cleaning. The heater is then charged with thermal energy by connecting the heater to the power source. In a preferred embodiment, the charging step is accomplished by plugging the plug  48  into a wall outlet. Alternatively, the heater can be electrically connected to a battery or other power source. A further embodiment could involve a manual or other type of switch that can be activated while the plug  48  is plugged into the wall outlet. Activation of such a switch would result in electrical energy flowing to the heater from the power source. 
     The electrical resistance heating of the heating grid then causes the heating grid to rise to a temperature of approximately 240° F. within approximately 2.5 minutes. A food product such as pizza or any other food item for which it is desirable to keep warm is placed in the food product receiving area  12 . The food product could be hot sandwiches, pizza, casseroles or other food items. The heater is disconnected from the power source. The article such as a food product is then delivered in the delivery apparatus. The delivery step is typically carried out by placing the delivery apparatus in a vehicle such as a car or truck and driving the vehicle to the customers&#39; home or business. An advantage of the present invention is that the delivery apparatus does not need to be plugged into a power source such as a cigarette lighter in the vehicle during transport to the customer. 
     It is also noted that in accordance with the embodiment shown in  FIG. 6 , the pizza or other food product can be placed in the delivery apparatus after more than 2.5 minutes from the beginning of the charging step. For example, a pizza bag  11  containing a wrap heater  29  may be left plugged into the power source for up to about 1.5 hours before the controller allows the pizza bag  11  to cool to room temperature. Therefore an exemplary use is to leave the bag  11  and wrap heater  29  plugged into the power source for up to about one hour and then place the pizza into the food receiving area, unplug the heater and transport the entire delivery apparatus to the customer. Alternatively, the food product may be placed in the delivery apparatus before the charging step. This alternative does not result in a cold food product because of the short amount of time (2.5 minutes) that it takes to charge the heater. 
     An alternative embodiment of a heater  298  of the present invention is shown in exploded perspective view in  FIG. 9 . This heater  298  is placed inside a pizza delivery bag (not shown). The embodiment shown in  FIG. 9  utilizes a polycarbonate heat sink in conjunction with a heating grid that is not of the high watt density category. This alternative embodiment utilizes a thermostat to control the temperature of the heating grid. 
     The heating grid of  FIG. 9  comprises a 4.5 ohm wound wire  300  that is taped to a polycarbonate heat sink  302 . The wound wire  300  has an output of 190 watts over a 12 inch by 12 inch heater. The resulting watt density is therefore approximately 1.3 watts per square inch. The wound wire  300  is attached to the polycarbonate heat sink  302  by a 9 inch by 14.75 inch piece of aluminum tape  303  that covers the central portion of the wound wire  300 . Two 12.75 inch by 2 inch strips of aluminum tape  304  cover the ends of the wound wire  300  and assist in attaching the wound wire  300  to the polycarbonate heat sink  302 . The male plug  306  is for connection to a typical wall outlet. The cord  308  connects plug  306  to female plug  308  that receives male plug  312 . Cord  308  and associated plugs  306  and  310  may be removed from plug  312  and replaced with a different cord and plugs if it is desired to utilize a power source of different voltage requirements or to replace a worn cord or plug. 
     The power cord  314  includes ground wire  316  that is mounted to a 3/16 inch ring tongue terminal  322  at the center of the polycarbonate heat sink. Wire  318  is the positive power wire and it leads to a thermostat  324  and thermal fuse  326  (shown in  FIG. 10 ). Wire  320  is the returning neutral wire from the wound wire  300 . Maniglass layers  330  and  332  are situated between the wound wire  300  and the injection molded hard-shell  334 . At the other end of heater  298  is a hard-shell  336  which is constructed to mate with the hard-shell  334  to enclose the other components of the heater  298 . 
       FIG. 10  shows the thermostat  324  and fuse  326  of the alternative embodiment shown in  FIG. 9 . Wire  318  is spliced to the thermal fuse  326  by a Panduit butt splice  328 . The fuse  326  is in series electrical connection with thermostat  324  that is in series connection with wire  340 . 
     When the heater  298  is assembled the hard-shell  334  is coupled to hard-shell  336  by welding. Different welding techniques may be utilized such as hot plate welding and ultrasonic welding. The hard-shells  334  is constructed of polypropylene filled with talc. The hard-shell  334  could also be polycarbonate or other materials with similar properties. Wire  314  passes between the two hard-shells  324  and  326  at the passage created by indentations  342  and  344 . 
     Now referring to  FIGS. 11–12 , a pizza delivery bag according to the invention is shown at reference numeral  400 . The pizza delivery bag includes an enunciating device  402 . The enunciating device is an arrangement that provides a user or customer with desired information about the temperature conditions within the bag. The pizza delivery bag is a type of delivery apparatus according to the invention that can be used to transport and deliver various items or articles to be kept warm. Preferred items or articles to be kept warm include food such as pizza. Furthermore, the enunciating device can be used to display temperature or thermal conditions within the delivery apparatus and, if desired, provide control of the temperature or thermal conditions within the delivery apparatus. The delivery apparatus that includes an enunciating device can be referred to as a “smart bag” because of the informational display properties, and, if desired, the control properties exhibited by the apparatus. 
     The enunciating device allows a customer to have confidence that the food arriving in the delivery container is arriving at a desired thermal condition. In addition, the enunciating device provides an additional quality control measure to insure that the food product is delivered at a specified temperature. Accordingly, the enunciating device can be used to provide desired information about the thermal condition or temperature of the article provided within the container. 
     The enunciating device can be a visual enunciating device or an audio enunciating device. The enunciating device  402  is shown as a visual enunciating device  404 . The visual enunciating device  404  is shown having a plurality of lights  406  and  408  that can function similar to light sources  254  and  256 . Illumination of light  406  can indicate that the bag  400  is charging, and illumination of light  408  can indicate that the temperature in the bag is at least about 140° F. In general, it should be understood that the temperature of a heating element or a heat sink in the bag is preferably measured rather than the actual ambient temperature in the bag. The ambient temperature in the bag can be calculated based upon the measured temperature of the heating element or the heat sink. As the bag  400  is used and an article is either moved into the bag or removed from the bag, it is expected that the ambient temperature in the bag will change but will return to a desired temperature that is above about 140° F. The Food and Drug Administration has specified that 140° F. is a hot hold food safe temperature for transporting food. 
     The lights  406  and  408  can be provided as red and green lights, for example. It is expected that a start-up protocol can include a solid red light changing to flashing red indicating that the bag  400  is charging. The red light switch is off and the green light switch is on when the readiness set point threshold has been achieved. The readiness set point threshold refers to the temperature of the heating element or the heat sink provided within the bag  400 . Preferably, the readiness set point threshold is at least about 200° F. It is believed that the readiness set point threshold can be used to fairly accurately calculate the temperature within the bag  400  in which the article to be heated  410  is exposed. Preferably, the article  410  includes a food item such as a pizza  412  provided within a cardboard box  414 . 
     The bag  400  includes a top wall  416 , a bottom wall  418 , a rear wall  420 , and side walls  422  and  424 . Preferably, the walls include an insulation material  426  for reducing heat transfer from the interior area  428  of the bag  400  to exterior of the bag. The amount of insulation  426  provided in the walls can vary. As shown in  FIG. 12 , the top wall  416  includes a greater thickness of insulation material  426  than the bottom wall  418 . 
     The bag  400  includes an interior area  428  that includes the article to be heated  410  and the heater  430 . In general, the interior area  428  refers to the area within the bag  400  provided between the interior surfaces  432  of each wall. The interior area  428  includes an article transport area  440  and a heater storage area  442 . The heater  430  can be contained within the heater storage area  442  by a holder  444 . Preferably, the holder  444  includes a fabric cover  446  for containing the heater  430  in place. Preferably, the article  410  can be provided resting on the heater  430  and in thermally conductive contact with the heater  430 . It should be appreciated that the phrase “thermally conductive contact” refers to the existence of heat transfer from the heater to the article. There is no requirement of direct contact between the heater and the article, although direct contact can be preferred. Preferably, the holder  444  includes a window  445  that allows viewing of the enunciating device  402 . 
     The bag  400  includes a flap  450  that covers the bag opening. The flap  450  is selectively movable between an open position and a closed position. As shown in  FIGS. 11 and 12 , the flap  450  is provided in a closed position. When the flap  450  is moved to an open position, the article  410  can be removed from the bag  400 . 
     The flap  450  can include a transparent material  452 . By manufacturing at least a portion of the flap as a transparent material  452 , it is possible to provide a window  453  for visually observing the enunciating device  402  provided within the interior area  428 . The flap can be provided as an opaque material such as a fabric. In the case of an audio enunciating device, it is believed that it is not necessary to provide a window for viewing the interior of the bag. Furthermore, the flap  450  can be provided as a non-transparent material (to visible light) when the enunciating device is provided so that it is visible when the flap  450  is provided in the closed position, or when it is decided to be sufficient to only view the enunciating device when the flap  450  is provided in an open position. For example, the enunciating device can be provided attached to the bag exterior  455  or can be provided so that it hangs outside of the bag exterior  455 . The flap can be held in a closed position by a fastener  454  such as a hook and loop fastener system  456 . 
     The bag  400  can include handles  460  and  462  for transporting the bag. The heater  430  can be heated by electrical energy. A power cord  464  can be provided for providing electrical connectivity between the heater  430  and a power source. The power source can be provided by alternating current or direct current. The power cord  464  includes a plug  466  for connecting to a desired power source. 
     The heater can include a heating element  433  such as a resistive heating element, an induction heating element, and/or a microwave heating element. The heater can include a heat sink  435 . The heat sink can be a sensible and/or latent polymeric based material, a sensible and/or latent ceramic-based material, a sensible and/or latent metal enclosure, and/or a latent heat storage micro encapsulated material. A preferred micro encapsulated material is in the form of a foam or gel and is available from Frisbee Technology. The heating element and heat sink material can be any of those materials previously referred to in this patent application. The power source for powering the enunciating device can include a conventional 120 and/or 220 volt line voltage input, a voltage reducing a current source transformer driven electronic isolating circuit, a conventional electronic non-isolated circuit, a bridge rectifier, a battery, a charged capacitor such as a standard battery and a rechargeable battery, and an induction driven, bag mounted, secondary coil (24 volts) with input/output enunciation device power supply only or with control and resistive grid power supply (24 volt). 
     The bag  400  includes a control unit  436  provided within a container  439 . The control unit  437  includes a power connection  441  for instructing the heater  430  to heat. Additionally included is a temperature sensor  443  for sensing the temperature of the heating element  433  and/or the heat sink  435 . The control unit  437  controls the supply of power received through the power cord  464 . In addition, the enunciating device  402  can be connected to the control unit  437  or it can include its own control unit and its own sensor and power supply. 
     Now referring to  FIGS. 13 and 14 , enunciating devices are shown.  FIG. 13(   a )–( c ) shows visual enunciating devices  500 .  FIG. 13(   a ) shows a rounded visual enunciation device  504 .  FIG. 13(   b ) shows a rectangular visual enunciation device  505 . The rectangular visual enunciation device  505  is preferably in the form of lighted pipes  506 .  FIG. 13(   c ) shows a numeric visual enunciation device  508 . The numeric visual enunciation device  508  includes three characters  510 . Preferably, the visual enunciation devices are provided as LED displays. 
     An alternative enunciating device according to the invention can be referred to as an audio enunciating device. As shown in  FIG. 14 , an audio enunciating device  512  is shown. The audio enunciating device  512  preferably includes a voice chip  514  that synthesizes a human voice for audibly indicating the temperature within the delivery bag once provided with stimulation. It is believed that the voice chip can be stimulated by pressing a button and/or by opening the delivery bag. 
     Now referring to  FIGS. 15 and 16 , functional block diagrams for operating the enunciation device according to the invention are provided.  FIG. 15  shows a functional block diagram that does not include a control for controlling the temperature within the delivery bag. The functional block diagram  520  includes a power source  522 , a trigger  524 , a temperature sensor  526 , and a display  528 . In general, the power source  522  can include any power source sufficient to drive the circuit  523 . Preferred power sources include batteries including commercially available batteries and rechargeable batteries. In addition, the power source can be induction driven. That is, when the heating source for the delivery bag is driven by induction heating, a secondary coil can be provided which charges upon exposure to the induction force, thereby providing a power source for operating the circuit  523 . In addition, the power source can be bridge rectified, voltage reduced current source, charged capacitor, and/or transformer driven isolated circuit. The trigger  524  can be any trigger that generates the display  528 . It is possible that the trigger  524  is always on thereby always causing the display  528  to enunciate the temperature conditions within the delivery bag. Of course, the enunciating device can be provided without a trigger so that it is always “on.” In order to prolong the longevity of the power source  522 , it is possible to provide a trigger  524  which, when activated, causes the display  528  to enunciate the temperature conditions within the delivery bag. The trigger can be a button, a switch, and any opto coupler switch such as a light sensor or photocell or an infrared emitter/receiver switch. The temperature sensor  526  can be any temperature sensor such as a thermometer or thermocouple that senses the temperature conditions within the delivery bag. The temperature sensor can include a thermister, a thermocouple, an RTD, and/or bimetal thermostat. The display  528  is preferably an enunciating device such as one of the enunciating devices previously described. Preferred displays include digital readouts, alternating light patterns demonstrating different conditions, and voice chips. 
       FIG. 16  shows a functional block diagram  540  including a power source  542 , a trigger  544 , a temperature sensor  546 , a control  548 , and a display  550 . It should be appreciated that the power source  542 , the trigger  544 , the temperature sensor  546 , and the display  550  can be similar to the power source  522 , the trigger  524 , the temperature sensor  526 , and the display  528 . The diagram  540  is different from the diagram  520  in that the diagram  540  includes a controller  548 . The controller  548  is preferably provided for controlling the temperature within the delivery bag. Accordingly, the controller  548  is preferably provided with an ability to generate a feedback to the heating element within the delivery bag. 
     The enunciating device is preferably constructed to work when connected to a secondary power source and continue working when disconnected from the secondary power source. That is, it can be powered by its primary power source. In addition, the enunciating device is preferably portable which means that it can be attached and detached from a delivery apparatus. Furthermore, the enunciating device is preferably constructed to be operated at a temperature greater than 140° F., and is sufficiently light weight. Preferably, the enunciating device weighs less than 0.5 lb. and preferably less than three ounces. In addition, the enunciating device preferably can be either permanently installed in a delivery apparatus or retrofitted to a variety of delivery apparatus and to the heat sink of the delivery apparatus. 
     Now referring to  FIG. 27 , a delivery apparatus for use with an induction range is shown at reference numeral  600 . The delivery apparatus  600  includes a housing  602  having an interior area  604 . The housing can be provided in the form of a delivery bag  605 . The interior area  604  includes sufficient space for storage of an article  606  to be delivered and a heater  608  that provides heating to the article  606 . When the delivery apparatus  600  is used to deliver pizza, the article  606  is preferably a pizza  610  provided in a box  612 . An enunciating device  614  can be included for providing information about the temperature conditions within the interior area  604 . Preferably, the enunciating device  614  includes a controller  616  for controlling the temperature conditions within the bag  605  and a display  617  for displaying the temperature conditions within the bag  605 . Although it is convenient to have the controller  616  as part of the enunciating device  614 , the controller can be provided as part of the heater  608  or separate from the enunciating device  614  and the heater  608 . In addition, the controller  616  can be any type of apparatus that provides temperature control within the bag. 
     The delivery apparatus  600  is provided for use with an induction powered heater  620 . When the induction powered heater  620  is exposed to a magnetic field created by an induction range, the magnetic field can be used to power the induction powered heater  620 . It is understood that the strength of a magnetic field generally decreases with increasing distance from the source of the magnetic field. Accordingly, it is desirable to provide the induction powered heater  620  as close as possible to the source of the magnetic field to maximize the effect of the magnetic field on the induction powered heater  620 . The delivery apparatus  600  preferably has a relatively thin bottom wall  622  to reduce the distance between the induction powered heater  620  and the induction range. The bottom wall  622  of the delivery apparatus  600  can be provided without the insulation layer conventionally found in the walls of a pizza delivery bag. 
     The interior area as shown in  FIG. 27  includes a heater receiving area  623  and an article receiving area  625 . The heater receiving area  623  is separated from the article receiving area  625  by a wall  627 . The wall  627  can be extended so that the induction power heater  620  is completely separated from the article  606 . It is advantageous to isolate the induction powered heater  620  from the article receiving area  625  to reduce the likelihood of contamination of the induction powered heater  620  by materials placed within the article receiving area  625 . The heater receiving area  623  can be referred to as being sufficiently sealed to prevent contamination of the induction powered heater  620  during use of the delivery apparatus  600  when the wall  627  completely separates the two areas. 
     Now referring to  FIG. 28 , the relationship between an induction powered heater  630  and an induction range  632  is shown. The induction powered heater  630  is provided within the interior area  633  of the housing  634 . The induction powered heater  630  includes a heat sink  636 , a heating element  638 , an insulation layer  640 , an induction receiving coil  642 , a bottom layer  644 , and a binder  646  for holding the induction powered heater  630  together. It should be appreciated that size of the binder  646  in  FIG. 28  is exaggerated to demonstrate that it includes a top lip  648  and a bottom lip  650  which clip or bind the components of the induction powered heater  630  together. Although the binder  646  is a preferred mechanism for holding the components of the induction powered heater  630  together, it should be understood that the components can be held together by a container or by other techniques known to those skilled in the art of heater production. 
     The induction receiving coil  642  of the induction powered heater  630  is provided wrapped around a core  652 . The core  652  is provided to help maintain the shape of the induction receiving coil  642 . It should be understood that the core  652  can be omitted if the induction receiving coil  642  will maintain its shape without it and if it is not needed to maintain the position of the induction receiving coil  642  within the induction powered heater  630 . Although the core  652  is shown attached to the bottom layer  644  by a fastener  654  which is a rivet  656 , it should be understood that the fastener  654  can include any other fastener capable of holding the core  652  to the bottom layer  644 , including, screws, adhesive, etc. In addition, it should be understood that the core  652  can be formed from the bottom layer  644 . That is, the core can be an indentation or molded extension of the bottom layer  644 . 
     The heating element  638  is preferably provided adjacent to the heat sink  636  to provide efficient transfer of heat from the heating element  638  to the heat sink  636 . The insulation layer  640  is preferably provided to protect the induction receiving coil  642  from the heating element  638 . In addition, the bottom layer  644  can be omitted if the induction receiving coil  642  can be held in position without it. In addition, the induction powered heater  630  can include a housing or sleeve or container that contains or encloses it. 
     The induction range  632  includes a magnetic field generator  660  provided within the induction range housing  662 . The induction range  632  includes a power cord  664  for providing electrical connectivity between the magnetic field generator  660  and an electrical current power source. The power cord  664  preferably includes a plug  665  for providing a connection to an electrical power source. Induction ranges are commercially available and can be obtained, for example, from Spring U.S.A. Corporation of Naperville, Ill. Preferably, the induction range is provided that runs off a 120 volt line input or a 220 volt line input. 
     The induction range  632  creates a magnetic field. Placing the induction receiving coil  642  within the magnetic field causes an electrical current to develop within the induction receiving coil  642 . The electrical current that is generated within the induction receiving coil  642  can be used to power the heating element  638 . In addition, the electrical current generated within the induction receiving coil  642  can be used to power the enunciating device and/or the controller for controlling the operation of the induction powered heater  630  if these components are present. Alternatively, the induction receiving coil  642  can be used to charge an energy storage device that will then be used to power the enunciating device and/or the controller. An exemplary energy storage device includes a battery. It is pointed out that rechargeable batteries have been identified as a power source  522  for operating the enunciation device  500 . The induction receiving coil  642  can function as the power source  522  or can be used to charge rechargeable batteries that serve as the power source  522 . 
     The heat sink  636  can be any material that absorbs heat from the heating element  638  and releases the heat to provide heating of the delivery apparatus  634  for a desired period of time after the heating element  638  has been turned off or no longer generates heat. The heat sink can include sensible and/or latent heat sink materials including polymers, ceramic-based materials, and microencapsulated materials. A preferred heat sink material includes polycarbonate because it is relatively lightweight and exhibits a fairly high melting temperature. The heat sink  636  can include those materials identified as the heat sink  84  in  FIG. 4 . 
     The heating element  638  is preferably an electrical resistance heating element  668 . The electrical resistance heating element  668  preferably provides a desired heat output when the induction receiving coil  642  is exposed to the magnetic field created by the induction range  632 . In the case of a pizza delivery bag, it is desirable for the heater to generate a sufficient amount of heat so that the heat sink  636  can keep the pizza or pizzas provided within the pizza delivery bag sufficiently warm during delivery to a customer. The electrical resistance heating element  668  is preferably a “high watt density heating grid” such as the heating grid  80  shown in  FIG. 4 . Preferably, the electrical resistance heating element  668  is a heating element that provides sufficient heating in a short enough period of time. Preferably, the electrical resistance heating element  668  provides a sufficient amount of heat to the heat sink  636  so that the heat sink  636  can continually discharge heat to the article  606  within the housing  602 . It is desirable for the electrical resistance heating element  668  to heat the heat sink  636  sufficiently quickly to reduce down time or the time of non-use of the delivery apparatus  600 . Preferably, the electrical resistance heating element  668  sufficiently heats the heat sink  636  within a time period of less than about five minutes beginning with the introduction of the induction receiving coil  642  within the magnetic field created by the induction range  632 . More preferably, the electrical resistance heating element  668  provides sufficient heating within a time period of less than about three minutes. It should be understood that sufficient heating refers to heating the heat sink sufficiently so that it will maintain the article at a desired temperature until the article is delivered to a consumer. If the electrical resistance heating element  668  heats too slowly, then the down time of the delivery apparatus  600  may be too long. If the electrical resistance heating element  668  heats too quickly, it is possible that components of the delivery apparatus  600  may burn out too quickly. Preferably, the electrical resistance heating element  668  has a characterization of between about 200 watts and about 500 watts. A preferred electrical resistance heating element  668  has a characterization of about 300 watts. 
     It should be appreciated that the reference to being placed within a magnetic field refers to a magnetic field sufficient to generate a current within the induction receiving coil  642  that can power the electrical resistance heating element  668 . In general, the type of magnetic field contemplated for generating a current within the induction receiving coil  642  is provided by an induction range. 
     The insulation layer  640  is provided for protecting the induction receiving coil  642  from the heating element  638 . Accordingly, the thermal properties of the insulation layer  640  are provided so that the induction receiving coil  642  is not damaged during the operation of the induction powered heater  630 . It should be understood that the insulation layer  640  can be excluded if the concern about damaging the induction receiving coil  642  because of the presence of the heating element  638  can be eliminated and if the heat from the heating element  638  can be directed toward the heat sink  636  and provided so as to maximize the use of the generated heat in heating articles within the delivery apparatus. The insulation layer  640  can include multiple insulation layers  670  and  671  in order to provide the desired level of thermal insulation. A preferred type of thermal insulation includes fiberglass insulation and insulation available under the name Maniglass. In addition, the insulation layer  640  is desirable to reduce heat transfer out of the delivery apparatus though, for example, the bottom wall. As discussed above, the bottom wall of a delivery apparatus may not contain much thermal insulation in order to reduce the distance between the induction receiving coil and the induction range. 
     The induction receiving coil  642  is preferably provided as an electrically conductive coil  680  for generating a current when placed within a magnetic field. The electrically conductive coil  680  is preferably constructed so that when it is provided within the magnetic field, it generates the desired current for operating the components of the delivery apparatus  600  that are to be operated or driven by the induction receiving coil  642 . That is, the electrically conductive coil  680  should generate a current sufficient to run the electrical resistance heating element  638 . Preferably, the electrically conductive coil  680  provides a current of at least about 0.8 amp. More preferably, the conductive coil  680  provides a current of about 0.8 amp to about 3 amp for running the heating element  638 . 
     The electrically conductive coil  680  can include multiple coils  682  such as a primary coil  684  and a secondary coil  686 . The primary coil  684  can be wound sufficiently to generate a current sufficient to power the heating element  638 . The secondary coil  686  can be coiled sufficiently to power the enunciating device and/or the device for controlling the operation of the induction powered heater  630 . The Applicants discovered that a difficulty with operating both the heating element  638  and the controller is that the resistance of the heating element causes the controller to receive insufficient power to power the controlling operations. One way to correct this is to provide a separate coil for powering the electrical resistance heater and a separate coil for powering the controller. 
     The bottom layer  644  and the core  652  can be provided from any material that keeps the electrically conductive coil  680  sufficiently in place. Preferably, the bottom layer  644  and the core  652  are provided as a polymer material  688 . The polymer  688  can be provided from the same material as the heat sink  636 . 
     It should be appreciated that the induction powered heater of the invention can be provided as a wrap heater as described as described above. For a wrap heater, it is expected that the coil could be used to power electrical resistance heaters provided in the sleeves of the wrap heater. 
     Now referring to  FIGS. 29–31 , an alternative embodiment of an induction powered heater is shown at reference numeral  700 . The induction powered heater  700  includes a heat sink  702 , a heating element  704 , an insulation layer  706 , an induction receiving coil  708 , a bottom layer  710 , and binder  712  for holding the induction powered heater  700  together. A second insulation layer  707  is shown in  FIG. 29 . The heat sink  702  is provided with wings or extensions  716 . The purpose for the wings or extension  716  is to help center the induction powered heater  700  within the delivery apparatus. That is, it is expected that the wings or extensions  716  will fit within the corners of the delivery apparatus to provide the induction receiving coil  708  within a relatively constant location in the delivery apparatus. By providing the induction receiving coil  708  at a relatively constant location within the delivery apparatus, it is expected that it will be possible to more consistently place the induction receiving coil  708  within the strongest part of a magnetic field created by an induction range. A core  711  can be provided about which the induction receiving coil  708  can be wrapped. The core  711  can be a part of the bottom layer  710 . 
     A controller  720  can be provided for controlling the operation of the heater  700  and/or for controlling the enunciating device such as the enunciating device as previously described. That is, the previously described enunciating device can be used in combination with the induction powered heater  700  and the enunciating device can be a visual or audio display device as described. Alternatively, a thermostat  722  can be provided for controlling the operation of the heater  700 . In addition, the control can be shared by the controller  720  and the thermostat  722 . For example, the thermostat  722  can control the heating of the heating element  706  up to a set point temperature. Once the set point temperature is reached, the control can be transferred to the controller  720 . In such a shared arrangement, the thermostat  722  can be electrically located in parallel with the controller. In another embodiment, the controller  720  can control the heater  700  without the thermostat  722 . The thermister  723  can be provided for sensing and conveying temperature information to the controller  720 . A preferred type of thermister includes a temperature sensor for electrically sensing and conveying temperature. Fuses  725  and  727  are provided to avoid runaway heating of the heating element  704 . The controller  720  can include a battery  721  therein for running the controller  720 . 
     The heater  700  can be controlled solely by the thermostat  722 . It should be appreciated that the thermostat  722  can be provided embedded in or adjacent to the insulation  706 . In addition, the thermister  723  can be provided embedded in or adjacent to the insulation  706 . Preferably, the thermostat  722  and or the thermister  723  are provided sufficiently close to the heating element  704  to detect the heated environment created by the heating element  704 . In a preferred embodiment, the thermostat  722  and/or the thermister  723  are provided adjacent the heating element  704 . In an alternative embodiment, the thermostat  722  and/or the thermister  723  can be provided in a different location that is not adjacent to the heating element  704 , but it is desirable for these components to be placed at a location that measures the heated environment within the delivery apparatus. 
     It is common for an induction range to perform a periodic detection test to determine whether a receiver, such as a conductive coil, is placed on the range. The reason for this is that it takes energy for the induction range to generate a magnetic field and, if there is no receiver, energy savings can be obtained by not generating a magnetic field. An induction range can be provided that is programmed to perform such a detection test at a predetermined interval, such as three seconds. If a device is placed on the induction range but is turned off so that it cannot draw an induced current, the detection test will not detect a presence of a conductive receiving coil. It may be desirable for the controller  720  to perform a self-test. Preferably, the self-test takes a short period of time, such as about five seconds, and should be performed prior to initiating the heating of the heating element  704 . In the case of a pizza delivery bag, the controller can be designed to automatically allow current to be drawn by the heating element  704  when the controller  720  is placed on the induction range. This design allows the controller to be provided with sufficient power so that it can perform the self-test. 
     Now referring to  FIGS. 32 and 33 , alternative embodiments of the induction receiving coil of the invention are shown at reference numerals  750  and  752 . The induction receiving coils  750  and  752  include dual conductive coils  754  and  756 . The dual conductive coil  754  is a representation of the induction receiving coil  708 . In general, the dual conductive coil  754  includes a primary coil  760  and a secondary coil  762 . The primary coil  760  includes sufficient windings to power the electrically resistive heating element, and the secondary coil  762  provides sufficient power to power the enunciating device and/or the controller. As shown, contacts  764  and  766  are in electrical connectivity with the primary coil  760 , and the contacts  768  and  770  are provided in electrical connectivity with the secondary coil  762 . The coils  760  and  762  can be provided as wires that wrap in a planar or non-planar fashion. That is, the wire can be arranged so that the entire coil is only one wire thick in a planer fashion. Alternatively, the coil can be arranged so that it is a wrapping of several thicknesses of wire in a non-planer fashion. In a preferred embodiment, the induction receiving coil  750  includes a primary coil  760  formed from 22 turns of 14 gauge wire, and the induction receiving coil  750  has an inner diameter  772  of 1.9 inches and an outer diameter  774  of 5.9 inches. In addition, the windings can be held together by coil fasteners  776  that preferably include tape  778 . 
     The induction receiving coil  752  is shown as a planar induction receiving coil. That is, the wiring is provided as a single layer. Of course, the wiring can be provided in multiple planes, if desired. The dual conductive coil  756  includes a primary coil  780  and a secondary coil  782 . Leads  784  and  786  are provided in electrical connectivity with the primary coil  780 , and leads  788  and  790  are provided in electrical connectivity with the secondary coil  782 . In a preferred embodiment of the dual conductive coil  756 , the primary coil  780  includes 33 turns of 18 gauge wire, and the secondary coil  782  includes 7 turns of 18 gauge wire. In a 22 KHz magnetic field, the output of the primary coil  780  is expected to be about 275 VAC and 1.5 A, and the output of the secondary coil is expected to be about 15 VAC and 150 mA. In addition, this is for a center opening  790  of ¾ inch and a maximum coil diameter of 10 inches. Furthermore, the coils are preferably prepared from metallic wire. A preferred type of metallic wire includes copper wire. The wire can be provided embedded in a substrate, such as, a circuit board. 
     The above specification, examples and data provide a complete description of the manufacture and use device of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.