HK1081045B - Heat retentive inductive-heatable laminated matrix - Google Patents

Description

Heat retentive induction heated laminated substrate

This application is a divisional application of the invention patent application entitled "Heat retentive Induction heated laminated substrate" having application number "02812841.9".

Technical Field

The invention relates to a magnetic induction heating device, system and method. More particularly, the present invention relates to an induction heating body capable of retaining heat, which can be embedded or inserted in a seat of a stadium, a food supply bag or tray, or other articles to heat or warm the articles. The present invention also relates to an RFID-based induction heating/vending system that can be used to quickly and easily heat and vend hot seats, food service items, or other items for open stadiums, and then efficiently retrieve the used items from the hands of the customer.

Background

In serving food, it is desirable to keep warm hot food such as pizza. One such practice is to insert or contain a heat retainer within a food-holding container, such as a pizza serving bag, to maintain the temperature of the food during serving. Examples of such systems and methods are disclosed in U.S. Pat. Nos.6,232,585 (the '585 patent) and 6,320,169 (the' 169 patent), which are owned by the assignee of the present application and the contents of which are incorporated herein by reference. Specifically, these patents disclose self-regulating food supply systems and methods of magnetic induction heating that utilize a magnetic induction heater and a corresponding induction heatable body to maintain the temperature of the food or other item during the supply process.

While the systems and methods disclosed in the '585 and' 169 patents are far superior to prior art systems and methods in warming food and other items, they suffer from several limitations that limit their application. For example, the induction-heatable bodies disclosed in these patents cannot be heated quickly, especially at high temperatures. Induction heatable bodies made of high cost, excellent ferromagnetic materials can heat more quickly than those made of lower grade ferromagnetic materials, but such devices are relatively expensive and heavy, and thus, are impractical for use in systems such as portable, low cost food supply systems. Many prior art induction-heatable bodies also often develop "hot spots" when heated with a heating source having a non-uniform magnetic field distribution, such as that provided by a typical flat spiral induction heating coil.

The prior art food service systems containing heat sensing bodies also suffer from several distinct disadvantages. For example, such systems are particularly configured for holding and warming pizzas, but not for other types of food. While pizza may constitute the largest percentage of food offerings in the united states, it is believed that customers will accept and prefer other types of offered food if the food items are able to keep warm during the offering process. In particular, it is believed that customers are willing to accept sandwich and french fries sold by mcdonia if the mcdonia has a food serving system that maintains the temperature of these foods during their serving.

In addition to food products, it is often desirable to heat other items. For example, in outdoor sporting events, concerts and other similar activities, it is common for spectators to sit on a conventional stadium or bleacher while using a portable heated seat cushion (hot seat) to keep them warm for comfort. Several such hot seats are disclosed in U.S. patent nos.5,545,198; 5,700,284, respectively; 5,300,105 and 5,357,693, which are generally described as seat cushions including a removable outer cover containing a liquid that can be heated in a microwave oven. The main drawback of this type of thermal pads is that they do not retain heat for a long time and therefore are not suitable in many long-lasting activities such as concerts and sports events.

Furthermore, because the fluid jacket must be heated in a microwave oven, it is difficult to heat and commercially rent a large number of these types of thermal pads to viewers during sporting events or concert activities. Commercial rental of hot pads has also become impractical because it is difficult to retrieve the seat cushion from the hands of the customer after it has been used. At the same time, the heat cushions must be manually heated, sold and collected, which requires too much labor and becomes cost-inefficient.

Disclosure of Invention

The present invention addresses the problems discussed above and provides significant advantages in the art of heat sensors capable of retaining heat, food delivery systems, and systems for renting and recycling thermal pads.

One embodiment of the present invention is an induction-heatable body that can be heated quickly to a desired temperature, retains heat for a long period of time sufficient for almost any application, and does not form "hot spots" even when heated by a heat source having an uneven magnetic field distribution. Moreover, the induction-heatable body of the present invention achieves the above-mentioned advantages while maintaining the advantages of light weight, low cost and ease of manufacture.

A preferred embodiment of the induction-heatable body generally comprises a plurality of induction-heatable layers, each sandwiched between alternating layers of heat-retentive material. The induction heating layer preferably comprises a sheet of graphite material which can be inductively heated at a magnetic field frequency of between 20 and 50 kHz. The thermal protection layer preferably comprises a solid-solid phase change material, such as irradiated cross-linked polyethylene.

Each induction heating layer should be of sufficient depth to allow induction heating of all layers completely or substantially simultaneously when the induction-heatable body is placed on or near an induction heating coil. This allows a large surface area to be heated simultaneously so that the induction-heatable body is quickly heated to a desired temperature by a typical induction heating coil and retains heat for an extended period of time. The alternating layers of induction heating material and heat retention material transfer heat quickly and uniformly so that any "hot spots" that occur during heating of the inductor are quickly eliminated.

Another embodiment of the present invention is a food service assembly uniquely adapted and configured to maintain the temperature of food products such as sandwiches, french fries and other related food products sold by McDonor. The food serving assembly generally includes a magnetic induction heater, a food container, and an induction pack for carrying and isolating the food container. The magnetic induction heater operates under the same principles disclosed in '585 and' 169, but is specifically sized to heat the food product container of the present invention. The preferred magnetic induction heater includes an L-shaped base or body with an induction heating coil positioned in or on each leg of the body. The magnetic induction coils are controlled by a common control source and are connected to the RFID reader/writer.

The food container preferably includes an open-top outer box, an open-top inner box fitted within the outer box, a plurality of partition walls fitted within the inner box to partition the inner box to receive a plurality of different foods, and a lid fitted on the open top of the inner box to substantially seal the food container and retain heat therein. The food container may be sized to hold any type of food product such as sandwiches and french fries sold by mcdonia. Two induction-heatable bodies are positioned on the two outer walls of the inner case, the dimensions and orientation of which are such that: when the food container is placed on the heater, the induction heating body is positioned in the vicinity of the induction heating coil of the magnetic induction heater. The induction-heatable body is preferably substantially identical to the induction-heatable body described above. An RFID tag and thermal switch are also attached to the induction-heatable body and operate in substantially the same manner as described in the '585 and' 169 patents.

The supply package is preferably made of a lightweight, flexible, thermally insulating material that includes a compartment for receiving and insulating food containers. The supply package may also include a separate compartment to receive and insulate cold food products, such as soft drinks.

Another embodiment of the present invention is an RFID-based induction heating/vending system for quickly and efficiently heating, vending and recycling stadium seat cushions or other items used in sporting events, concerts and similar activities. The system generally includes any number of thermal pads, each including an induction-heatable body such as those described above; a charging/vending station for heating and vending seat cushions; a self-service heating station for use by customers to reheat their seats; and a recycling station for customers to return their hot pads after the event terminal.

The hot seat is configured to be placed on a seat of a conventional stadium or bleacher to increase the comfort and heat of the seat. Together with an induction-heatable body, each heat block comprises one or more layers of solid-solid phase change material for storing a large amount of thermal energy. The thermal seats may be inductively heated on an RFID induction heater and each contain an RFID tag to allow for temperature regulation as per the '169 and' 585 patents. These tabs may be connected to a thermal switch, as also described in the' 169 patent. The RFID tag also stores the customer's information, e.g., credit card number, and the time and date that the customer was rented. This information is stored on the RFID tag of a seat cushion while the hot seat is being heated by the induction heater of the charging/vending station, as described below.

The charging/vending station includes one or more induction heaters as described in the' 585 patent, an RFID reader/writer coupled to each heater, and a credit card reader, which may be coupled to more than one induction heater and has a microprocessor for controlling the flow of information. When a hot seat needs to be rented for a customer, the hot seat is placed on top of an induction heater and the customer's credit card is scanned. When scanning a credit card, the information on the card is sent to an RFID reader/writer connected to an induction heater and then written onto the RFID chip of the rented hot pad. At the same time, the RFID reader/writer reads and identifies the level of the item code on the RFID tag embedded in the thermal base and executes a specific heating algorithm designed to effectively bring the thermal base to a preselected temperature and maintain it at that temperature without input from the vendor. The heat/rental station preferably also includes a simple control system, such as a red light to indicate heat up and a green light to indicate heat up completion, so that a hot seat can be removed from the heater and then rented to a customer.

Self-service heating stations are similar to the charging/vending stations but lack a bank acceptor and credit card reader. The heating station includes one or more induction heaters and an RFID reader/writer connected to each heater. If the hot seat appears unheated throughout the campaign, the heating station allows the customer to heat its hot seat again. Moreover, if a long team is ranked at the fill/sell station, a customer who has rented a hot seat may use the self-service station to again heat his or her hot seat.

A vendor or customer may also use a filling/vending station or a self-service heating station to initially heat or reheat the food supply container, or other means during the event. Many self-service heating stations may be strategically located around a stadium or other centralized location to allow customers and vendors to easily and safely heat their hot seats, food serving containers, or other items without assistance.

The recovery station includes a generally closed housing having one or more openings or "chutes" into which the hot seats may be placed so as to irretrievably drop into the housing. An RFID antenna is positioned adjacent each chute and communicates with an RFID reader/writer and a control unit of the microcontroller. The RFID antenna reads an RFID tag that is dropped onto a hot seat within the housing. The control unit of the RFID reader/writer and microcontroller communicates with the receipt printer to output a receipt shortly after the hot seat has fallen into the chute. The control unit of the microcontroller also stores information on the transaction process, including the time and date of return of each hot seat, so that it can be retrieved immediately or subsequently via a direct cable connection, a modulator, or a wireless modulator. The transaction information may then be aggregated with transaction information from other recycle bins to effectively monitor the status of all rental hot seats.

The control unit of the recycle bin preferably has a user interface similar to that found in other automatic rental systems, such as self-service gasoline stations. The user interface instructs the customer to place the hot seat into the chute and then obtain his or her receipt. The simple operation of the recycle bin allows a large number of hot seats to be returned quickly without the need for employee intervention.

The heating/vending system of the present invention provides numerous advantages not available in the prior art. For example, the hot block may be quickly, easily, and automatically heated to a predetermined temperature on the induction heater of the RFID device. During the rental sale, the RFID tag embedded in each hot seat can receive and store customer information to identify the customer when the hot seat is returned.

The heat-up/rental station allows for initial heating of the hot seat by the vendor and loading of the customer's identification information at the same time as the rental sale. The recycle bin may then be used to return the hot seat, identify the returned hot seat, identify the customer that rented it, identify the time of return of the hot seat, give the customer a receipt showing his payment immediately, and store information for the transaction for immediate or future download to the central database.

The self-service heating station allows customers and vendors to easily reheat the hot seat during the event. Advantageously, the heating station can return the hot seat to its predetermined temperature without any data input by the customer.

The filling/vending stations and self-service heating stations may also be used to heat other items such as food serving bags and trays. During sporting events, concerts and other activities, customers may use the bags and trays to maintain the temperature of the food items, and then return the bags or trays to a recycling bin as described above.

Drawings

Several preferred embodiments of the present invention will be described in detail below with reference to the attached drawings, wherein:

fig. 1 is a perspective view of a charging/vending station constructed in accordance with a preferred embodiment of the induction heating/vending system of the present invention;

fig. 2 is a perspective view of a self-service heating station of the induction heating/vending system;

FIG. 3 is a front elevational view of a recycle bin of the induction heating/vending system;

FIG. 4 is a vertical sectional view of the recycle bin taken along line 4-4 of FIG. 3;

fig. 5 is a vertical cross-sectional view of a hot block of the induction heating/vending system with a preferred stack of induction heaters and RFID tags positioned within the hot block;

fig. 6 is a vertical sectional view of the laminated induction-heatable body of fig. 5, further including a thermal switch and shown adjacent the magnetic induction heating element;

fig. 7 is a vertical cross-sectional view of a pin-type induction heating body that can be positioned in the hot well of fig. 5 in place of the stacked induction heating bodies;

fig. 8 is an exploded perspective view of the pin-type induction heating body of fig. 7;

fig. 9 is a vertical sectional view of a matrix-type induction heating body which can be positioned in the hot well of fig. 5 in place of the stacked induction heating bodies;

FIG. 10 is a perspective view of a magnetic induction heater and a heat retention food container constructed in accordance with a preferred embodiment of a food induction assembly of the present invention;

FIG. 11 is a perspective view of the food container of FIG. 10 with the lid removed;

FIG. 12 is a perspective view of an induction package in which a food container may be positioned;

FIG. 13 is an exploded perspective view of the components of the food container of FIG. 11;

FIG. 14 is a vertical cross-sectional view of a food container placed on an induction heater;

FIG. 15 is a plan view of the food container of FIG. 10 with the lid fully removed; and

fig. 16 is a vertical cross-sectional view of the food container taken along line 16-16 of fig. 15.

The drawings are not intended to limit the invention to the particular embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention.

Detailed Description

The embodiments of fig. 1-9

Turning now to the drawings, and particularly to fig. 1-3, there is shown an induction heating/vending system that can be used to heat, vend, and then retrieve stadium seats, food serving bags, trays, or any other inductively heated object. The heating/vending system generally comprises a plurality of objects to be heated, such as a hot seat 10, a food serving bag or tray; at least one charging/vending station 12 for heating and vending items; at least one self-service heating station operable to initially heat or reheat the articles; and at least one recycle bin 16 for customers to return the recycled items. Each of these components will be described in more detail below. Referring to fig. 4-9, several embodiments of an induction-heatable body are shown that may be used in a heating/vending system, or other system or device, such as a food service bag. The induction-heatable body will be described below in connection with the hot block of the heating/vending system.

Hot seat

As described above, the heating/vending system may be used to heat and vend any item, such as a hot plate 10, food serving bag, food serving tray, or the like. However, for the purposes of describing the preferred embodiment of the present invention, only the thermal base 10 will be described and illustrated in detail herein.

The hot seat 10 is used for heating and then placed on a conventional stadium or stadium-type seat to warm the seat and increase the comfort of the seat. As best shown in FIG. 5, each seat 10 is generally in the shape of a conventional stadium seat and includes a seat portion 18 and a seat back 20 for lumbar partial support. The seat portion 18 generally includes an induction-heatable body 22, a phase-change foam layer 24 positioned over the induction-heatable body 22, a thermal insulation layer 26 positioned beneath the induction-heatable body 22, and a seat cover 28 enclosing the induction-heatable body 22, the phase-change foam layer 24, and the insulation layer 26.

The induction-heatable body 22 may be heated within the charging/vending station 12 or the self-service heating station 14 (described in detail below). The present invention includes several different embodiments of induction-heatable body 22, which will be described separately below.

Phase change foam layer 24 is preferably formed from a foamed polymer material that is a mixture of a solid-solid phase change polymer and foam. Such a material is available from Frieby Technologies, Inc. of North Carolina as ComfortTemp^TMIs sold under the trademark (1). Comfortemp^TMThe foam comprises a thermoplastic foam^TMThe free-flowing microencapsulated phase change material of (a), which can have a phase transition temperature of 43 ° f to 142 ° f. The preferred phase transition temperature for the hot seat is 95 ° f. THERMASORB^TMThe powder may also be mixed into other high temperature resistant foams such as silicone foams.

The purpose of the phase change foam layer 24 is twofold. First and foremost, the foam absorbs energy from the upper surface of induction-heatable body 22 and alters thermsorb^TMPhase transition of (2). THERMASORB^TMThe large latent heat of the particles acts to buffer the temperature of the surface of seat cover 28 to maintain a preferred temperature of 95 ° f for an extended period of time. When the thermal energy stored within heating body 22 and phase change layer 24 is released (both released with latent and enthalpy at about 230 ° f during cooling after induction heating is complete), phase change foam layer 24 continues to absorb the thermal energy, while the top surface of seat cover 28 transfers the energy to the buttocks of the customer and the surrounding environment.

The secondary purpose of the phase change foam layer 24 is to provide a soft, pliable seat cushion for comfort purposes. Because the seat cover 28 is made of a pliable material, it can evenly distribute the weight of the customer with the aid of the phase change foam layer 24.

The insulation layer 26 under the induction heating body 22 is provided to reduce the loss of heat released from the induction heating body 22 and to direct the heat released from the induction heating body 22 upward toward the phase change foam layer 24. The insulation 26 may be formed of any conventional insulation material having a high R-value.

The seat cover 28 is preferably made of a pliable, hard, durable plastic such as polyurethane or polypropylene having sufficient thickness to resist scratching, impact, and harsh physical environments such as rain and snow. The lid 28 preferably has a removable base 30 that can be removed for insertion into and/or access to the induction-heatable body 22. The base plate 30 is secured to the remainder of the seat cover 28 with conventional fasteners or adhesives.

Laminated induction heating body

As described above, induction-heatable body 22 may be constructed in accordance with several embodiments of the present invention. The preferred embodiment is shown in fig. 5 and 6 and comprises a stack of substrates composed of at least two types of materials: 1) graphite material in the form of flakes that can inductively heat at magnetic field frequencies of 20 and 50kHz, and 2) thermally insulating, heat retaining polymer material that can bond to the graphite material, preferably without a separate binder. Specifically, the preferred induction heatable body comprises an alternating stack of induction heat generating graphite materials 32a, b, c and heat retentive polymer materials 34a, b, c, contained within a high density polyethylene shell or casing.

Graphite layers 32a, b, c are preferably formed of flexible graphite sheet material, e.g.,flexible graphite, or EGRAF^TMSheets, which are manufactured and registered trademarks by Graftech corporation, are a division of UCAR Carbon Company, Lakewood, ohio. Graphite layers 32a, b, c may also be formed from BMC940^TMIs formed of a hard graphite filled polymeric material available from Bulk Molding Compounds, inc.

Flexible graphite and EGRAF^TMThe flakes are produced by processing a high quality particulate graphite flake using a strong mineral acid in a mutually calculated process. The graphite flake is then heated to volatilize the mineral acid and expand the graphite flake multiple times to its original dimensions. No binder is introduced into the manufacturing process. The result is a sheet material with a carbon content typically in excess of 98% by weight. The sheet material exhibits properties of flexibility, light weight, compressibility, elasticity, chemical inertness, fire resistance, and stability under load and temperature. However, it is the anisotropic nature of the material due to its crystalline structure that provides certain benefits for the laminated induction-heatable body 22 of the present invention.

Flexible graphite and EGRAF^TMThe sheet is more electrically and thermally conductive in the plane than in the direction through the plane. It has been found experimentally that this anisotropy has two benefits. First, the higher electrical resistance in the direction of the through plane axis causes the material to have an impedance at 20-50 kHz which causes the magnetic induction heater (e.g., induction coil 38 in fig. 6) to operate at this frequency to effectively heat the material, while the super conductivity in the plane of the sheet causes eddy currents to heat, thereby quickly and rapidly achieving temperature equilibrium across the width of the sheet.

Second, and most importantly, the material can be inductively heated at the same time through successive layers, where each layer is electrically isolated from the next. That is to say intermixed with layers of insulating material 34a, b, cWill be described in relation to figures 5 and 6, in the following description of a stacked structure of several layers 32a, b, cEddy currents are induced in the layers of material. Experiments have shown that for the laminated matrix structure shown in fig. 5 and 6, the magnetic induction heating occurs at 20-50 kHz, and the graphite layers inductively generate heat at comparable heating rates. Higher magnetic field frequencies reduce the overall thickness of the laminated graphite (the sum of its layer thicknesses measured), which will heat the layers at comparable heating rates.

Equal heating rates of the continuous graphite layers 32a, b, c separated by insulating layers 34a, b, c have not been reported in conventional ferromagnetic induction heating elements. If the induction heating body of fig. 5 and 6 uses a steel sheet instead of the steel sheetSheet construction, then only the steel sheet closest to the induction heating coil will experience significant joule heating.EGRAF^TM，BMC940^TMAnd other graphite sheet materials, provides a number of unexpected advantages relating to thermal energy storage. For example, a larger amount of power can be applied to the laminated induction-heatable body 22 of fig. 5 and 6 without overheating any portion thereof, than can be applied to the same mass of heat-retentive material having a single layer of ferromagnetic material embedded therein. This is because each thin layer 34a, b, c of heat retentive polymer within the laminated induction heating body 22 has an adjacent surface layer 32a, b, c of graphite material that provides a source of conductive heat to drive thermal energy quickly through its plane without overheating either the graphite layer or the graphite/polymer interface. The mostly thin layer 34a, b, c of heat retentive polymer has two adjacent layers 32a, b, c of graphite material for uniform and rapid heating. It has been found that the induction-heatable body 22 of the construction shown in FIGS. 5 and 6 is employedThe graphite layer of (a) can receive three times the input power of the same heating mass with a single layer of induction heating material through the induction heating process. Even when there is no heat retaining materialThis is also the case when the portion of the charge is heated above 50 DEG F above its solid-to-solid temperature.

And EGRAF^TMAnother benefit of the anisotropic nature of the material is the extremely high thermal conductivity in the plane of the sheet of material. In a smaller surface area than the induction heating coil 38Or EGRAF^TMThis extremely high thermal conductivity actually prevents edge effects from occurring during induction heating of the segments. The edge effect of a sheet of ferromagnetic material during induction heating is well known in the art: if the edge is located within the surface boundaries of the induction heating coil, the edge of the ferromagnetic material sheet may become significantly hotter than the rest of the sheet. Even in the case where an uneven magnetic field is generated by the induction heating coil,and EGRAF^TMThe extremely high thermal conductivity of the material in the plane of the sheet causes the temperature to equilibrate almost instantaneously across the sheet.

Because of the fact thatAnd EGRAF^TMThe materials do not contain a binder and therefore they have a very low density. The standard density was 1.12 g/ml. It has been found that three 0.030 "thick plates in the structure shown in FIGS. 5 and 6Class C materials from a COOKTEK operating at 30kHz^TMCoupling cold rolled steel sheet as 0.035' thick on C-1800 induction cooktop with the same energy, wherein the spacing between the cold rolled steel sheet and the induction heating coil is equal toThe spacing between the closest sheet and the induction heating coil is equal. Moreover, the coupling is the sameAmount of energyIs 60% by weight less than that of the cold-rolled steel sheet.

BMC940^TMAre commonly used as conductive plates in fuel cells and are capable of inducing heat generation at frequencies between 30 and 50 kHz. The material is much lighter than metal materials and can be compression molded into various shapes. The depth of penetration of the material at the above-mentioned frequencies is very large so that it can be uniformly through-heated over a thickness of about 1 inch. BMC940^TMSheet display and the aboveAnd EGRAF^TMThe same properties. However, since at BMC940^TMThe binder is required, so that the inductive coupling efficiency is not goodIs high and the thermal conductivity in the plane of the sheet is not high. Thus, although it is used in the present invention, BMC940^TMIs inferior to the induction heating layer 32a, b, c in useOr EGRAF^TMIdeally.

The insulating, heat retentive polymer layers 34a, b, c are preferably formed of a solid-to-solid phase change material such as radiation crosslinked polyethylene. The procedure for irradiation crosslinking of polyethylene is described in detail in the' 585 patent. The preferred form of polyethylene for use as the thermal barrier is an off-the-shelf polyethylene sheet of any density having a melting temperature (which after cross-linking becomes a quasi-solid phase transition temperature) suitable for the application for which the substrate is being prepared. Of course, other phase change polymers that can be made into sheet shapes or other non-phase change polymers such as nylon, polycarbonate, and others can also be used as the thermal barrier.

The preferred induction-heatable body 22 also includes a separate RFID tag 40 (fig. 5) or an RFID tag 40 connected to a thermal switch 42 (fig. 6). The method of temperature regulation permitted by the RFID tag 40, or the combination of the RFID tag 40 and the thermal switch 42, when used in conjunction with an induction heater containing an RFID reader/writer is fully described in the' 169 patent. This method of induction heating and temperature regulation allows the induction-heatable body 22 to be used in a variety of products without entering any portion of the induction-heatable body to control its final temperature during the heating process. Induction-heatable body 22 may also simply be induction-heated by applying a known power for a known time.

Although not shown, the induction-heatable body 22 may also include a ferromagnetic layer. The ferromagnetic layer may be formed of cold rolled steel or any other alloy and may provide temperature feedback to the induction cooktop to regulate the temperature of the induction heatable body. In order to be able to heat all of the graphite layers 32a, b, c and the ferromagnetic layers, the graphite layers 32a, b, c must be placed closest to the induction working coil 38. Thus, the magnetic field will induce eddy currents in the graphite layer and the ferromagnetic layer simultaneously.

The layered induction-heatable body 22 can be manufactured in several different ways. One approach is to laminate large sheets of graphite and phase change material in a heated lamination press. In this case, the final sheet size laminated substrate is die cut or otherwise cut after lamination is complete. An induction-heatable body of the final desired shape can be obtained. This manufacturing method does not require much labor, and therefore, is less expensive than the second method described below. The method and structure are suitable for use with induction-heatable bodies that are to be incorporated into application products such as the thermal base 10 illustrated and described herein.

The laminated induction-heatable body 22 can also be manufactured by laminating sheets of graphite and phase change material cut in advance, suitably stacked in a laminator. In this case, it is preferable to make a jig or stacking tool that mates with the laminator so that the perimeter edges of the heat retentive polymer seal together during lamination. Then, the graphite layer is sealed in the induction heating body, which can prevent separation of the lamination during repeated heating and also prevent penetration of foreign substances such as liquid between the layers of the laminated induction heating body. This manufacturing method is preferably applied to an induction-heatable body which is not sealed in a cavity or lid, but which is intended to be used solely as a heating source. The method is also preferably applicable when the laminated induction-heatable body contains a ferromagnetic material layer such as a cold-rolled steel sheet which is difficult to die-cut

Regardless of the method of manufacture described above, layered induction heatable body 22 is manufactured in a press at controlled temperatures and pressures, preferably 300 ° f and 50 psi. The cooling rate of the press is controlled to prevent stresses in the induction heating body that would cause warping after removal from the press. The cross-linked polyethylene acts as a binder to bind the polymer layer to the graphite layer. For other polymeric materials, a binder may be used.

The RFID tag 40 and switch 42 may be inserted into the induction-heatable body 22, either in a stacked manner such that the tag/switch combination is completely encapsulated within the walls of the stacked assembly, or after the stacking has been completed. In the first case, the tab/switch combination is potted with a material such as epoxy. The potting assembly is placed within a hollow portion formed by a central cutting hole in the inner layer of graphite and heat retentive polymer. The lamination press then presses the layers together to bond the tabs/switches to the laminated induction heatable body 22 using the bonding characteristics of the cross-linked polyethylene.

In the latter case, as shown in fig. 6, an opening 44 is cut in the center of the layers 32a, b, c and 34a, b, c of the induction-heatable body 22. After the induction heating body 22 is removed from the laminating press, the tabs/switches are placed into the openings and then potted in place with an adhesive such as epoxy.

Pin type induction heating body

The hot block 10 may also include a pin-type induction heating body 22a as shown in fig. 7 and 8, instead of the stacked induction heating bodies 22 as described above. The pin-type induction heating body 22a generally includes an induction heating layer 46, a heat-insulating layer 48, a heat-insulating layer 50, and a bottom plate 52 that fixes the heat-insulating layer 48 and the heat-insulating layer 50 to the induction heating layer 46.

The induction heating layer 46 is preferably formed of BMC940^TMAnd (4) forming. BMC940^TMIs a graphite filled polymeric material, as described above, available from Bulk Molding Compounds of west chicago, illinois. The induction heating layer 46 is preferably formed by compression molding to include a substantially flat planar top plate 54, four depending peripheral side walls 56, and a plurality of "pins" 58 depending from the top plate 54 in the same direction as the side walls 56.

The thermal protection layer 48 includes a generally flat plate 60 having grid holes 62 formed therein that are aligned with the pins 58 of the induction heating layer 46. As shown in fig. 7, the thermal protection layer 48 fits within the depending side wall 56 such that the pins 58 are received within the grid holes 62 to form a close thermal contact therebetween. The preferred heat retention layer 48 is formed of a solid-solid phase change material, such as a cross-linked polyethylene material or UHMW as described in the' 585 patent. The phase transition temperature of the material is preferably between about 220F and 265F.

The insulation layer 50 is preferably formed from MANNIGLASS^TMV1200 or V1900, which is sold by Lydall corporation of Troy, N.Y., insulation 50 is placed under the thermal protection layer 48 to maintain thermal contact with the ends of the pins 58 and the bottom surface of the thermal protection layer 48. The RFID tag 40a as described above is placed within the cut-out 64 of the insulation layer 50. The RFID tag 40a may be electrically connected to a thermal switch 42a that is in thermal contact with the thermal retention layer 48 to temperature condition the induction-heatable body 22a according to the method described in the' 585 patent. The bottom plate 52 is then secured or bonded to the depending sidewall 56 of the induction heating layer 46, the bottom plate 52 preferably being formed of a high temperature hard plastic such as BMC 310.

As with the laminated induction-heatable body 22 described above, the pin-type induction-heatable body 22a can be heated by the induction heater to a temperature just above the phase transition temperature of the heat retaining layer 48 thereof, and held at that temperature. After the thermal socket 10 is removed from the induction heater, the heat retentive phase change layer 48, which has been heated to a temperature above the phase change temperature of approximately between 220 ° f and 265 ° f, has a significant latent heat and enthalpy release. Due to the high R value of the thermal insulation layer 26, the released heat is preferably driven upward toward the phase change foam 24. The phase change foam 24 cushions the surface temperature of the hot seat cover 28 so that the consumer can experience a comfortable temperature for an extended period of time.

Hot base with base body type induction heating body

The heat block 10 may also include a matrix-type heat-retentive induction heating body 22b instead of the induction heating body 22 described above. As shown in fig. 9, the matrix-type induction heating body includes an induction heating layer 66, a heat-retaining phase change material layer 68, and a base plate 70 for fixing the phase change material to the induction heating layer 66.

The induction heating layer 66 preferably comprises a Bulk Molding Compound (BMC) 940^TMA mixture of resinous material, graphite flakes, and a matrix-crosslinked polyethylene as described in the' 585 patent. Prior to compression molding, the ingredients were mixed in the following approximate proportions: 50% BMC940^TM(by weight), 10% graphite flakes (by weight), and 40% matrix cross-linked polyethylene (by weight).

The resultant material is inductively heat-generating, compression-moldable and capable of storing latent heat at the phase transition temperatures of the crosslinked polyethylene employed. The heat-retentive phase change layer 68 and the base plate 70 are the same as those described in the pin type induction heating body 22a under the same name.

Spherical particle type induction heating body

The hot block 10 may also include an induction heating body such as the pellet type described in the' 169 patent. However, for the present invention, the surface ribs shown in the' 169 patent are preferably removed. The pellet-type induction heatable body may also preferably include a heat-retentive phase change layer, a base plate, RFID tags, and a thermal switch as described above.

Other food supply containers and devices

The four embodiments of induction-heatable body 22 described above may also be embedded in food serving containers and other devices that are heated and tempered by the heating/vending system described above. One such food serving container, described in the' 585 patent, is in the form of a pizza serving bag. Such food serving containers may be automatically tempered to the appropriate temperature by the induction heater of the filling/vending station 12. Thus, the vendor may heat these food-serving containers using the same heaters used to heat hot block 10.

Charging/renting and selling station

The charging/vending station 12 is shown in fig. 1 and is similar to the charging station disclosed in the' 585 patent. The preferred charging/vending station 12 includes a table 72 equipped with two or more laterally spaced magnetic induction charging stations 74a, b. The top surface of the table has two spaced openings to accommodate the corresponding heat charging stations 74a, b. Each of the thermal charging stations is identical and includes an upwardly and forwardly open polycarbonate retainer/holder 76a, each having a base plate 78, upstanding side walls 80, and back walls 82. Each station 74a, b includes a magnetic induction cooktop 84a, b located directly below each locator/holder 76a, b and connected to the floor 78 of the locator/holder 76a, b, and a user control box 86a, b. The control boxes 86a, b may include a temperature adjustment reader, an input device that allows the user to select a desired adjustment temperature within a given range, a power switch, a reset switch, a red light to indicate "heat up", a green light to indicate "ready", and a light to indicate "operation required".

Each cooktop 84a, b is preferably a COOKTEK^TMCD-1800 magnetic induction cooktop of the type having a standard ceramic top surface that can be removed and attached to the locator/holder 76a, b. The microprocessor of the cooktop has been programmed to control the cooktop according to the preferred temperature control method disclosed in the' 585 patent. Each cooktop 84a, b is used to generate an alternating magnetic field in the preferred range of 20-100 kHz. It should be understood that COOKTEK^TMThe CD-1800 version is only one example of a magnetic induction heater that may be used in the present invention, and various other commercially available cooktops of this type may also be used. Further, with regard to magnetic inductionA more detailed description of the circuitry of the cooktop can be found in U.S. patent nos.4,555,608 and 3,978,307, which are incorporated herein by reference.

A pair of spaced apart light sensors (not shown) may be positioned within each locator/holder 76a, b. The light sensor is connected to the microprocessor line controller of the cooktops 84a, b and serves as a sensor that determines when the hot seat 10 is located on one of the cooktops 84a, b. The light sensor sends a start signal to the microprocessor when the hot seat 10 is placed on the cooktop, allowing it to start a heating operation. It should be understood that in this case, a variety of different sensors may be used, provided that the sensors are capable of identifying the appropriate hot seat, food container or other heating element, and other objects that may be improperly or inadvertently placed on the cooktop. The simplest sensor could be a mechanical switch or several switches placed in series on the base plate, so that only the appropriate hot seat or food serving container would activate the switch or switches in series. Other switches such as proximity switches or light sensor switches (photosensors) may be used instead of the push-type switches.

While the light sensors described above are effective for some applications, the charging/vending station 12 preferably utilizes more advanced location sensors using Radio Frequency Identification (RFID) technology. RFID is similar to bar code technology, but utilizes radio frequencies instead of optical signals. An RFID system consists of two main components, a reader and a special tag or card. In the case of the present invention, a reader (87 in fig. 6) is positioned near each base plate instead of or in addition to the light sensor, while the corresponding tab (40 in fig. 6) is connected to the hot block 10. The reader 87 performs several functions, one of which is to generate a low level radio frequency magnetic field, typically at 125kHz or 13.56MHz, by a coil-type transmitting antenna 88. The corresponding RFID tag 40 also includes a coil antenna and an integrated circuit. When the tag 40 receives the magnetic energy of the reader 87 and antenna 88, it transmits the stored information in the programmed IC to the reader 87, which then verifies the signal, decodes the data to the control unit of the cooktop 84a, b, or to a separate control unit.

RFID technology has many advantages in the present invention. The RFID tag 40 may be several inches from the reader 87 and still be in communication with the reader 87. Also, many RFID tags are read-write tags, and many readers are reader-writers. The contents of the read/write tag can be arbitrarily changed by a signal sent from a reader/writer. Thus, a reader (e.g., OMR-705, manufactured by motorola) may have its output connected to the cooktop microprocessor and its antenna positioned below the soleplate. Each respective hot block includes an RFID tag 40 (e.g., IT-254E from motorola) such that when the hot block 10 with an attached tag 40 is placed on the locator/holder 76a, b, communication between the block's tag 40 and the reader 87 generates an activation signal to initiate the heating cycle. Other types of objects placed on the cooktop that do not include an RFID tag will not initiate any heating.

The charging/vending station 12 also preferably includes a cash register 90 with a credit card reader 92 in communication with the cooktops 84a, b so that information from a customer's credit card can be written to the RFID tag 40 of the hot holder 10 rented to the customer. A credit card reader is preferably connected to all of the induction cooktops 84a, b with microprocessors controlling the flow of information.

To use the charging/vending station 12, a vendor simply places the thermal base 10 on the locators/holders 76a, b. The readers 87 of the heat-up stations 74a, b immediately recognize the level of the code of the object attached to or embedded in the RFID tag 40 in the hot block 10 and execute a special heating algorithm designed to effectively heat the hot block 10 to a predetermined temperature and maintain that temperature without the need for data input by the customer. This process is described entirely in the' 585 patent. While the hot block 10 is heating, the vendor takes the customer's credit card and scans it through the credit card reader 92. All of the contents of the customer's credit card or portions of the credit card number are transferred to the RFID tag 40 embedded within the hot block 10 being heated in the appropriate charging station 12. Also, the time and date when the heating operation occurred is written into the RFID tag 40. After the information transfer and the hot block 10 has been fully heated, the "ready" light is illuminated and the vendor gives the hot block 10 to the customer. And advises the customer that a rental fee will be driven into the credit card once he returns hot seat 10 to the recycling bin. The customer will also be informed that a full return fee can be driven into the credit card if the hot block 10 is not returned.

Because of the flexibility of the RFID-based induction heating method, the same filling/vending station 12 can be used to automatically heat and temperature condition other objects such as food serving containers.

Self-service heating station

The self-service heating station 14 is shown in fig. 2 and is similar to the charging/vending station 12, but lacks a cash register and credit card reader. The purpose of the self-service heating station is to allow the customer to reheat the rented hot seat 10 if the hot seat is not warm throughout the campaign. Moreover, a customer who purchases hot seats may use the heating station 14 to heat his or her hot seats 10 without having to line up at the filling/vending station 12. Finally, a vendor may utilize the heating station 14 to initially heat or reheat a food supply container or other such device. Many self-service heating stations can be placed in strategic locations around the stadium to provide easy access to the customers. Simple instructions in the heating station coupled with simple operation of the induction heater enable customers to easily and safely heat their hot plate 10 and other induction heated objects.

Recycle bin

The recycling station 16 is shown in fig. 3 and 4 and includes a substantially closed enclosure 94, the enclosure 94 having one or more openings or "chutes" 96 into which the hot plate 10 and other inductively heated objects may be placed so as to irretrievably drop into the enclosure. Referring to fig. 4, an RFID antenna 98 is positioned adjacent each chute 96 and is in communication with an RFID reader/writer 100 and a control unit 102 of the microcontroller. RFID antenna 98 reads an RFID tag 40 of a hot seat 10 that is dropped into housing 94. The RFID reader/writer 100 and the control unit 102 of the microcontroller communicate with the receipt printer 104 to output a receipt shortly after the hot block 10 falls into the chute 96. The control unit 102 of the microcontroller also stores information on the transaction process, including the time and date of return of each hot seat, so that it can be retrieved immediately or thereafter via a direct cable connection, a modulator, or a wireless modulator. The transaction information may then be aggregated with other recycle bin transaction information to effectively monitor the status of all rental hot seats 10.

The control unit 102 preferably has a user interface 106 similar to that found in other automatic rental and sale systems, such as self-service gasoline stations. User interface 106 instructs the customer to place hot block 10 into chute 96 and then take his or her receipt from the receipt printer. The simple operation of the recycle bin 16 allows a large number of hot seats 10 to be returned quickly without requiring employee intervention.

The preferred RFID reader/writer 100 is a coupler of the mediiols 200 package manufactured and sold by Gemplus corporation, france. This coupling is ideal for this application because it can simultaneously control 4 different RFID antennas and handle communications with these antennas. The preferred RFID antenna 98 is an Aero LC antenna. The antenna is large enough to easily read the RFID tag 40 on the hot block 10 when slid down one of the chutes 96.

An RFID reader/writer 100 with a user interface 106 and a control unit 102 of the microcontroller communicate with a receipt printer 104 to output a receipt to the customer after a few seconds after the customer has placed the hot seat into one of the chutes. The receipt preferably lists the time of sale, time of return, credit card payment, and other useful information. The recycle bin 16 also calculates how much time has elapsed between the hot-seat sale and return and, if appropriate, may require a mispayment due on the customer's credit card.

The control unit 102 also stores transaction information including the time and date of each hot seat return so that it can be retrieved by the vendor via a direct cable connection, a modulator, or a wireless modulator. The retrieval of this information may be done either simultaneously with the transaction or after a delay. In either case, the transaction information may be compiled with transaction information from other recycle bins to effectively monitor the status of all sales hot seats.

The recycle bin 16 also preferably has a locked rear access door that can be opened by authorized personnel to remove the returned hot seats 10 and return them to the charging/vending station 12.

Examples of the invention

The following examples illustrate the presently preferred methods for producing several embodiments of the layered induction heatable body 22, thermal base 10, and heating/vending system of the present invention. It should be understood, however, that these examples are provided by way of illustration and are not intended to limit the overall scope of the invention.

Example 1

In this example, the laminated induction-heatable body 22 is constructed by a vacuum lamination process. First, the components or layers are assembled by hand in the following order, with layer 1 being the topmost layer from the perspective of FIG. 6:

^*low density polyethylene

The third layer of LDPE (layer 5) was die cut with a 1.25 "diameter hole. Third layer(layer 6) and a second layer(layer 2) a 2.5 "diameter hole was also die cut. In the second layerMust be largestTo a lesser extent interfering with the front face of the surface of the RFID tag 40. The die cutting process is performed before the laminated induction-heatable body 22 specified in the above table is manually assembled.

The RFID tag 40 and thermal switch 42 are then connected and potted with epoxy. The resultant structure was approximately 1.25 "diameter and 0.30" thick. Placement of RFID tag/thermal switch structure to third layerIn the hole of (layer 6), the thermal switch is faced downwards. Next, epoxy is added to the holes. The whole structure was then laminated in vacuum according to the following technical conditions:

Time	1.7min
		temperature of	400℉
Vacuum-pumping atmospheric pressure	550mm Hg
		Pressure of the cylinder	50psi

The heat from the vacuum lamination process cures the epoxy resulting in an RFID tag/thermal switch structure having a height of about 0.275-0.30 "

The entire layered induction heatable body 22 can be heated to about 230 ° f in about 20 seconds. In contrast, a metal disc-shaped induction-heatable body was heated to approximately the same temperature, which took about 2 hours and 15 minutes. Also, the graphite-laminated induction heating body 22 is about half the weight of the metal disc-shaped induction heating body. The test shows that three are 0.30 ″The layers result in full efficiency of the laminated induction heating body 22 without overheating the LDPE layer.

Example 2

In this example, the laminated induction-heatable body 22 was constructed using the same vacuum lamination process as described above, but without the addition of an RFID tag/thermal switch. Laminated structure in addition toIn addition to the layers, high density and low density polyethylene are included. The laminated induction-heatable body 22 was assembled by hand in the following order, with layer 1 being the topmost layer:

¹high density polyethylene

Vacuum lamination was performed according to the following technical conditions:

Time	1.7min
		temperature of	400℉
Vacuum-pumping atmospheric pressure	550mm Hg
		Pressure of the cylinder	50psi

As shown in the table above, HDPE has a higher melting point than LDPE as a function of its increasing density. The use of HDPE allows for greater current to be applied to the structure because HDPE does not undergo a phase change at low temperatures. Moreover, the use of HDPE allows for the storage of greater latent heat. Finally, when HDPE is positioned as an outer layer of the structure, the HDPE acts to buffer the outside of the laminate structure from the softened LDPE.

A laminated induction heatable body 22 comprising a combination of HDPE/LDPE and flexible graphite layers, heated to 230 ° f in less time than the construction described in example 1. Clearly, by using HDPE, the advantage of using anisotropic materials other than LDPE will be increased, as HDPE is more resistant to phase change and can store more latent heat than LDPE alone.

Example 3

In this example, the pin-type induction heating body 22a is formed using a compression molding tool. A 0.25 "hole was drilled into a 0.25" thick HDPE sheet. The HDPE used has dimensions of 12 "x 12" only to fit the dimensions of the compression molding tool. Next, BMC940^TMResin and graphite resin with filler, available from Bulk Molding Compounds inc. were applied to pre-drilled HDPE sheets. The entire structure is then compression moulded according to the following technical conditions:

Time	35min
		temperature of	375℉
Pressure of the cylinder	50psi

Making BMC940^TMThe primary purpose of the resin pins in cooperation with the holes in the HDPE is to create a close relationship between the two materials, thereby enabling the formation of a self-heating material (BMC 940)^TM) Efficient energy transfer to a heat retention material (HDPE). Such an induction heating body is not as effective as the laminated type induction heating body discussed in examples 1 and 2, but may be used as an alternative.

Example 4

In this example, a matrix-type induction-heatable body 22b was prepared by kneading the following materials in a low-shear mixer for 10 minutes or until complete mixing:

composition (I)	Composition ratio
		BMC940	50％
Graphite flake	10％
		Matrix Linear LDPE	40％

Tests of the induction heating body 22b show that the energy of coupling of the matrix type induction heating body is less than that of the induction heating body without the LDPE structure. To increase the low resistance in the transverse plane and the high resistance in the through plane of the induction-heatable body, i.e. to increase the anisotropy, graphite sheets can be added. The resulting mixture is compression molded into increasingly thinner sheets to construct a structure of increased anisotropy. The thinnest plate formed was 0.40 "thick. The addition of graphite results in improved coupling properties, but not as well as the use of flexible graphite or the use of BMC940^TMIs effective with graphite flake alone because LDPE interferes with the conductivity of the across-plane induction heater of the material.

Example 5

In this example, a thermal base having dimensions of 16 x 16 inches was constructed to include a nylon supply bag, two gel pads developed by Pittsburgh Plastics, four laminated induction heaters, HDPE, and a vacuum insulation panel. The laminated induction-heatable body was constructed according to example 1 above, but without the molded RFID tag. Sold by Pittsburgh plasticsAndthe gel pad is used for forming a temperature gradient. The gel pad may be considered to comprise about 40% by weight of THERMASORB^TM(solid-solid phase change material) and fillers.The cushion is placed against the outside of the seat, i.e. the area in contact with the buttocks of the seat user.The gel pad is placed on the induction heating body andbetween the gel pads.The gel pad has a phase transition temperature of 122 DEG FThe gel pad has a phase transition temperature of 95 ° f.

The hot block 10 is constructed with four laminated induction-heatable bodies 22 placed into a nylon housing. Four stacked induction-heatable bodies 22 matched to four induction coils are required to heat the hot block at 20,000 watts of power, since the largest induction heaters work at 5,000 watts of power. The laminated induction heating body does not include the molded RFID tag 40. Instead, the RFID tag 40 is placed within the surface of the nylon housing. The magnetic flux generates eddy current through the laminated structure.The anisotropic property ofA transient thermal equilibrium is achieved in the cross-plane of the material without overheating. In this case, the anisotropic property is thatIn-plane, as opposed to high resistance in the through-plane direction, which results in a uniform rate of heating throughout the laminated structure.The gel pad receives heat emitted from the laminated induction heating body and then the excessive heat is applied toA gel pad. The phase change achieved within the gel pad results in maintaining a comfortable temperature of the buttocks at about 90-95 ° f for about 5 hours. Phase (C)The metamaterials also provide additional cushioning for the hot seat user.

Example 6

In this example, a hot-seat heating/vending system is constructed with the following parts: a recycle bin and a check-in bin. The recycle bin includes an analog silver receptor and an RFID reader/writer platform. The simulated cash acceptor also includes a notebook computer, a credit card reader, and a receipt printer. The RFID reader/writer platform is connected with the notebook computer. The customer's credit card is scanned through a credit card reader and the customer's information is programmed into the RFID tag for future reference. At this stage, the RFID tag contains customer information, hot seat return time, and temperature adjustment information. The hot seat is placed on the platform and heated by magnetic induction.

The registration station includes an RFID reader/writer platform having a top plate and a bottom plate defining a slot into which a thermal mount having an RFID tag can be inserted. The registration station also includes a receipt printer and a wireless network connecting the simulated LCD screen and the database. The customer can return the hot seat by putting the hot seat into the slot at the recycling station. The check-in station gives the customer a receipt. The recovery time and customer information are stored for use by the vendor.

The third part of the station is a self-service heating station where the customer can heat the hot seat again during the event. The self-service heating station includes a single or multiple heating plates having induction heaters with RFID reader/writer platforms. The self-service heating station has a lighting system that indicates a hot and ready condition. A red light for indicating heat charging and a green light for indicating hot seat standby. The customer only needs to place the hot seat on the heating plate to heat again, and does not need to wait in long lines at a recycling bin.

The embodiment of fig. 10-16

Fig. 10-16 illustrate a food product supply assembly 108 that is specifically configured to supply and maintain the temperature of food products other than pizza. The preferred food service assembly 108 is configured to retain heat during the service process, such as sandwich and french fries sold by mcdonia, but may be configured to hold other food items sold by conventional fast food restaurants. As shown in fig. 10 and 12, the food supply assembly 108 generally includes a magnetic induction heater 110, a food container 112 that can be placed on the heater 110 for heating, and an induction pack 114 for carrying and insulating the food container 112.

The magnetic induction heater 110 operates under the same principles as the heaters disclosed in the above-mentioned '585 and' 169 patents, but is specifically sized to heat the food container 112 of the present invention. To this end, the preferred magnetic induction heater 110 includes an L-shaped base or body 116 with induction heating coils 118a, b positioned in or on each leg of the body 116. The magnetic induction coils 118a, b are controlled by a common control source (not shown) and are connected to an RFID reader/writer 120 operating as described above.

The food container 112 is shown in fig. 12 and includes an open-top outer box 122, an open-top inner box 124 fitted within the outer box 122, a dividing wall assembly 126 fitted within the inner box to divide the inner box into a plurality of adjacent compartments for carrying a plurality of food products, and a lid 128 fitted over the open top of the inner box 124 to substantially seal the food container 112 and retain heat therein. As described above, the food container 112 may be sized to hold any type of food product. In one embodiment, the inner box 124 and divider wall assembly 126 are configured to subdivide the food supply container to hold a number of packaging cartons, such as sandwich and french fries sold by mcdonia.

Outer casing 122 is preferably generally cuboidal and is formed from any suitable material, such as a synthetic resin material. An insulating layer 130 is preferably positioned along the interior walls of the cassette (as shown in fig. 14).

The inner case 124 is sized to fit snugly within the outer case 122 and, therefore, is also preferably cuboidal. The top edge of the inner box 124 includes a horizontally projecting lip 132 that fits over the top edge of the outer box 122 when the inner box 124 is inserted into the outer box. The inner case 124 includes two induction-heatable bodies: one 134a is positioned on the bottom panel of the cassette and the other 134b is positioned on one of the side walls of the cassette. The dimensions and orientation of the induction-heatable bodies 134a, b are such that: when the food container 112 is placed on the heater 110 as shown in fig. 14, the induction heating body is positioned close to the induction heating coil of the induction heater. The induction heating bodies 134a, b are preferably substantially identical to the layered induction heating body 22 described above for use in a hot seat heating/vending system, but may also be constructed in accordance with other embodiments of induction heating bodies described herein.

An RFID tag 136 and a thermal switch 138 are attached to the induction heating bodies 134a, b and operate in the same manner as the components named above. The RFID tag 136 is oriented such that: when the food sensing container 112 is placed on the heater as shown in fig. 14, the RFID tag is in proximity to the RFID reader/writer 120 on the induction heater 110.

A support bracket 139 or gasket is positioned at the bottom of the outer case 122 to support and prevent damage to the induction heating body 134a positioned on the bottom plate of the inner case 124. Likewise, a similar support bracket 140 or gasket is positioned along one of the interior sidewalls of outer casing 122 to support and protect induction heating body 134b positioned on the sidewall of inner casing 124.

As shown in fig. 15 and 16, the divider wall assembly 126 includes a tall divider wall 142 received within divider guide walls 144 positioned on opposite interior walls of the inner box 124, and two short divider walls 146a, b received within divider guide walls 148 positioned on opposite interior walls of the inner box 124 and centered along the tall divider wall 142. The divider walls may be easily removed and/or interchanged to change the load bearing structure of the inner box 124.

The lid 128 is sized to fit snugly over the open top of the inner box 124 to seal the food-serving container and retain heat therein. The lid preferably includes an insulating inner layer 150 and a horizontally projecting lip 152 that sits on the lip 132 of the inner box 124.

The supply package 114 is preferably made of a lightweight, flexible, thermally insulating material that includes a bottom 154 having an interior compartment or partition 156 for receiving the food container 112. The serving package 114 also preferably includes a second partition 158 for receiving food items such as soft drinks that do not require insulation during serving. A closure flap or lid 160 is hinged to one side of the base 154 and may be closed over the base 154 and secured in place using velcro or any other fastener to insulate the food container 112 from the cold soft drink contained within the base 154. The supply package also preferably includes one or more carrier belts 162 or handles 164.

In use, the food container 112 may be placed on the heater 110 to initially heat the induction-heatable bodies 134a, b positioned on the inner case 124. The RFID reader/writer 120 of the heater and the RFID tag 136 and thermal switch 138 of the food container 112 operate in the manner described above to heat the food container 112 to a desired temperature and maintain that temperature for an extended period of time. Once the food container has been heated, it can be removed from the heater and placed in a compartment of the bag as shown in FIG. 12. The hot food product may then be inserted into the food container while the cold food product, such as a soft drink, is positioned in the compartment adjacent the side of the food container 112 so that all of the food product contained in the bag is maintained at the desired temperature during serving.

Although the present invention has been described with reference to the preferred embodiments shown in the drawings, it should be noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as set forth in the claims below.

Having thus described the preferred embodiments of the present invention, what is claimed as novel and claimed as the invention is as follows.

Claims (7)

1. An induction-heatable body comprising:

a plurality of magnetically inductive heating layers each presenting a pair of spaced apart opposing faces and a thickness therebetween, said magnetically inductive heating layers having a first thermal resistance in a direction transverse to said faces and a second thermal resistance in a direction through the thickness of said opposing faces, said second thermal resistance being greater than said first thermal resistance; and

a heat retentive material located between the magnetic induction heating layers so as to electrically insulate the magnetic induction heating layers from each other and operable to function as a heat absorbing member in response to the magnetic induction heating of the magnetic induction heating layers.

2. The induction-heatable body as set forth in claim 1, wherein the magnetic induction-heatable layer is formed of a graphite material.

3. The induction-heatable body as set forth in claim 1, wherein the magnetic induction-heatable layer is formed of pre-formed graphite sheet.

4. The induction-heatable body as set forth in claim 1, wherein the heat retentive material comprises a solid-solid phase change polymer material.

5. An induction-heatable body comprising:

a plurality of discrete induction heating elements, each comprising a graphite material; and

a heat retentive material positioned adjacent to the induction heating elements, the heat retentive material being operable to electrically insulate the induction heating elements from each other and to function as a heat sink in response to magnetic induction heating of the induction heating elements.

6. The induction-heatable body as set forth in claim 5, wherein the induction heating elements each comprise a plurality of layers of graphite sheet material.

7. The induction-heatable body as set forth in claim 5, wherein the heat retentive material comprises multiple layers of phase change polymer material.