Electric heating – Inductive heating – With heat exchange
Reexamination Certificate
2002-05-20
2003-12-02
Leung, Philip H. (Department: 3742)
Electric heating
Inductive heating
With heat exchange
C219S634000, C219S635000, C219S647000, C219S221000, C126S375100, C126S400000, C297S180110, C297S180120
Reexamination Certificate
active
06657170
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to magnetic induction heating devices, systems, and methods. More particularly, the invention relates to a heat-retentive, induction-heatable body that maybe embedded or inserted in stadium seats, food delivery bags or trays, or other objects to heat or warm the objects. The invention also relates to an RFID-based induction heating/vending system that may be used to quickly and easily heat and vend stadium seats, food delivery items or other objects and to then efficiently collect the objects from customers after use.
2. Description of the Prior Art
It is desirable to keep hot foods, such as pizza, warm during delivery. One method of doing so is to insert or incorporate a heat-retentive body into a food-holding container such as a pizza delivery bag to maintain the temperature of the food item during delivery. Examples of such systems and methods are disclosed in U.S. Pat. No. 6,232,585 (the '585 patent) and U.S. Pat. No. 6,320,169 (the '169 patent), both owned by the assignee of the present application and incorporated into the present application by reference. Specifically, these patents disclose temperature self-regulating food delivery systems and magnetic induction heating methods that utilize a magnetic induction heater and a corresponding induction-heatable body to maintain the temperature of a food item or other object during delivery.
Although the systems and methods disclosed in the '585 and '169 patents are far superior to prior art systems and methods for keeping food and other items warm, they suffer from several limitations which limit their utility. For example, the induction-heatable bodies disclosed in these patents cannot be heated quickly, especially to a high temperature. Induction-heatable bodies made of high cost, fine ferromagnetic materials can be heated more quickly than those made of lower grade ferromagnetic materials, but such devices are relatively costly and heavy and thus impractical for many applications such as portable, cost-sensitive food delivery systems. Many prior art induction-heatable bodies also often develop “hot spots” when heated by a heating source having an uneven magnetic field distribution such as is provided by typical flat pancake spiral induction heating coils.
Prior art food delivery systems which incorporate induction-heatable bodies also suffer from several distinct disadvantages. For example, such systems are especially configured for holding and warming pizza, but not other types of food. Although pizza likely constitutes the largest percentage of delivered food items in the U.S., it is believed that consumers would accept and desire many other types of delivered food items if such food items could be kept warm during delivery. Specifically, it is believed that consumers would readily request the delivery of sandwiches and french fries such as those sold by the McDonald's Corporation if food delivery systems existed for maintaining the temperature of these food items during delivery.
It is also often desirable to heat objects other than food items. For example, portable, heatable seat cushions (thermal seats) are popular for use by consumers to stay warm and comfortable while seated in conventional stadium or bleacher seats during outdoor sporting events, concerts and other similar events. Several such thermal seats are disclosed in U.S. Pat. Nos. 5,545,198; 5,700,284; 5,300,105; and 5,357,693, which generally describe seat cushions including a removable envelope enclosing a fluid which can be heated in a microwave oven. A primary disadvantage of these types of thermal seats is that they do not retain heat long and therefore are unsuitable for use during many longer activities such as concerts and sporting events.
Moreover, because the fluid envelopes must be heated in microwaves, it is difficult to heat and commercially rent a large number of these types of thermal seats to customers at sporting events or concerts. The commercial rental of thermal seats has also been impractical because of the difficulties in collecting the seats back from customers after they have been used. Currently, thermal seats must be heated, vended and recollected manually, requiring too much labor to be cost-effective.
SUMMARY OF THE INVENTION
The present invention solves the above described problems and provides a distinct advance in the art of heat-retentive induction-heatable bodies, food delivery systems, and systems for vending and recollecting thermal seats.
One embodiment of the present invention is an induction heatable body that quickly heats to a desired temperature, retains heat long enough to be used in almost any application, and develops no “hot spots,” even when heated by a heating source having an uneven magnetic field distribution. Moreover, the induction-heatable body of the present invention achieves the foregoing while remaining relatively lightweight, inexpensive and easy to manufacture.
A preferred embodiment of the induction-heatable body broadly includes a plurality of induction-heatable layers each sandwiched between alternating layers of heat retentive material. The induction-heatable layers preferably consist of sheets of graphite material that can be inductively heated at magnetic field frequencies between 20 and 50 kHz. The heat-retentive layers preferably consist of solid-to-solid phase change material such as radiation cross-linked polyethylene.
The skin depth of each of the induction-heatable layers is large enough to permit complete and substantially simultaneous inductive heating of all of the layers when the induction-heatable body is placed on or in the vicinity of an induction heating coil. This allows a great amount of surface area to be simultaneously heated so that the induction-heatable body is quickly heated to a desired temperature by a typical induction heating coil and retains the heat for a long period of time. The alternating layers of induction-heatable material and heat-retentive material quickly and uniformly conduct heat so that any “hot spots” created during heating of the induction body are quickly eliminated.
Another embodiment of the present invention is a food delivery assembly uniquely adapted and configured for maintaining the temperature of sandwiches, french fries, and other related food items such as those sold by the McDonald's Corporation. The food delivery assembly broadly includes a magnetic induction heater, a food container, and a delivery bag for carrying and insulating the food container. The magnetic induction heater operates under the same principles as disclosed in the '585 and '169 patents but is specially sized and configured for heating the food 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 coupled with an RFID reader/writer.
The food container preferably includes an outer, open-topped box, an inner open-topped box that fits within the outer box, a plurality of divider walls that fit within the inner box to subdivide it for receiving several separate food items, and a lid that fits over the open top of the inner box to substantially seal the food container and retain heat therein. The food container may be sized and configured for holding any types of food items such as sandwiches and french fries sold by the McDonald's Corporation. Two induction-heatable cores are positioned on two exterior walls of the inner box and are sized and oriented so as to be positioned adjacent the induction heating coils of the magnetic induction heater when the food container is placed on the heater. The induction-heatable cores are preferably substantially identical to the induction-heatable body described above. An RFID tag and thermal switch are also coupled with the induction-heatable cores and operate substantially the same as described in the &apo
Hovey & Williams, LLP
Leung Philip H.
Thermal Solutions Inc.
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