Backup power supply charged by induction driven power supply for circuits accompanying portable heated container

Information

  • Patent Grant
  • 6534753
  • Patent Number
    6,534,753
  • Date Filed
    Friday, October 20, 2000
    24 years ago
  • Date Issued
    Tuesday, March 18, 2003
    21 years ago
Abstract
An induction heating system having an induction source, a heating element heated from the induction source, a power supply energized by the induction source and a circuit powered by the power supply. The circuit can be a controller which includes a temperature sensor for measuring a temperature of the heating element, and a feedback loop formed between the temperature sensor and the induction source. The heating element can be mounted within a housing to form an induction heated container for holding items to be heated. Such a container can be used in commercial food warming and holding.
Description




BACKGROUND OF THE INVENTION




Induction heating technology is well known and in wide spread use in industrial and commercial applications. One of the advantages of induction heating is the “non-contact” aspect of the technology. In particular, an induction heater uses magnetic fields to energize a heating element formed of a suitable radiation-sensitive material. The magnetic field generator need not be in contact with the heating element or even the item which is itself to be elevated in temperature. This arrangement makes induction heating a wise choice in applications where the heated item must easily be moved. These include industrial applications such as assembly lines or branding irons, as well as commercial food and plate warming.




There is a problem however with some of these applications. A plate warmer for example, needs to maintain the temperature of the plate below some defined allowable value. This is especially important if the plate is to be handled by a person, or if the plate is constructed of a plastic/metal composite.




One way to control the final temperature of the plate can be to apply the induction heating to the plate for a specific time duration. This method can provide poor results, unless the temperature of the plates was controlled before the start of the heating process. For example, if the same plate was exposed to an induction heater twice in a row, one time right after another, the plate can rise to a much higher temperature.




Another method of controlling the final temperature of the plate uses an external temperature sensor to measure the temperature of the plate before, and/or during the induction heating process. The sensor can be a “contact” or “non-contact” type. The “contact” type of temperature measurement spoils the inherent “non-contact” nature of the induction heating process. Additionally, it can be difficult to get the sensor to contact the correct surface of the heating element while providing a reliable, robust design. The “non-contact” type of temperature measurement is better, but more costly.




A completely different solution might involve a specially formulated metal heating element that only “couples” (i.e., allow currents to be induced) with the induction field if the temperature of the metal is below some pre-determined value. These metals have a Curie point that prevent the metal from overheating, even though the induction field is still present.




Other applications involve containers for take out food, such as pizza delivery bags, for example. These containers have typically been made with an external temperature indicator and a heating element heated by an AC source. These containers include an AC cord which can potentially entangle a user, creating safety issues when the container is transported.




The problem with the above methods is that none provide the capability of temperature indication, status monitoring, or other electronic functions after the heated item is removed from the induction heating device.




SUMMARY OF THE INVENTION




A solution to this problem is to place an induction-driven power supply within the electromagnetic field used to heat the heating element. The power supply can, for example, include an induction coil across which is induced a current. In an alternate embodiment, this can be provided by an opening or slot formed on the heating element, the opening having a first lead and a second lead, wherein the opening creates a voltage differential transferred to the first lead and the second lead.




The power supply is used to provide power to various electrical circuits which accompany the heating element. For example, these circuits may include a control system having a temperature sensor, a temperature indicator, and a communication link, such as an RF, light or sound link, which electronically controls the operation of induction source. The controller can communicate to the inductor, via the communication link, if more heating power is necessary and to indicate the desired temperature has been reached. The temperature indicator indicates when the element has reached an acceptable temperature and the unit is ready to be used.




Additionally, the circuits may include energy storage devices such as rechargeable batteries, or high capacity capacitors which are charged while the device is subjected to the electromagnetic field during the induction heating process. These energy storage devices permit the circuit to continue operating even when the container is removed from the electromagnetic field source.




In the case of the controller, the stored energy permits the monitoring of the temperature of the heating element with status LEDs even after the device has been removed from the inductor.











BRIEF DESCRIPTION OF THE DRAWINGS




The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.





FIG. 1

illustrates an induction heating system comprising a power supply.





FIG. 2

illustrates an alternate embodiment of the heating system.





FIG. 3

illustrates a cross sectional view of a heating element housing where the heating element has a coil.





FIG. 4

shows a block diagram of a circuit for a controller.





FIG. 5

illustrates a temperature controller circuit.





FIG. 6

illustrates a temperature indicator circuit.





FIG. 7

shows a blinker circuit.





FIG. 8

illustrates a voltage controlled oscillation circuit.











DETAILED DESCRIPTION OF THE INVENTION





FIG. 1

illustrates an induction powered heating system, given generally as


10


. The induction powered heating system


10


includes an induction source


20


and a heating element


22


. The heating system


10


also includes a power supply


42


which is energized by the induction source


20


. The heating element


22


can be formed of a material such that, when exposed to an induction source, a current is created within the heating element, thereby producing heat. The heating element


22


can be formed of a Curie point metal, for example. The heating element is typically mounted within a container or other housing


24


for the items to be heated (not shown).




The heating element


22


is mounted within a housing


24


. The heating element


22


and housing


24


form an induction heated container for holding items to be heated. The housing


24


includes a cavity defined by a top surface


11


, a bottom surface


15


and a side wall


19


. The side wall


19


attaches to an outer edge


13


of the top surface


11


with an outer edge


17


of the bottom surface


15


. A portion of the side wall


19


is moveably attached to the top surface


11


and the bottom surface


15


to allow user access to the cavity. The housing can be made of a thermally insulated material which can contain heat generated by the heating element


22


. The illustrated housing is a bag for storage of food, such as a pizza bag, for example.




The induction source


20


includes a field generator


26


and a power supply


28


. The field generator


26


has a core


56


and a ring


58


, where the core


56


and the ring


58


are made from ferrite, for example. The field generator


26


creates a magnetic flux which is used to induce a current in the heating element


22


, thereby creating heat. The power supply


28


can be a standard 120 VAC or a 240 VAC connection, for example.




The induction source


20


can produce an alternating magnetic flux. For example, at one instant, the core


56


can have a first polarity and the ring


58


can have a second polarity, thereby producing a radial magnetic field directed along the center axis of the core


56


and the ring


58


. At another instant the polarities of the core


56


and the ring


58


can switch such that the core


56


has a second polarity while the ring


58


has a first polarity. The resulting alternating magnetic flux induces a current in the heating element


22


to produce heat, provided that the heating element


22


is placed in close enough proximity to the induction source


20


.




The local power supply


42


is carried within the housing


24


. It can be as simple as an opening


46


on the heating element


22


, shown in

FIG. 1

, such as a slot


46


formed in the heating element


22


, for example. Other geometries can also be used. Each side of the opening


46


can be coupled to leads


44


, such as a first lead and a second lead, which, in turn, can be coupled to an electronic circuit. When the heating element


22


is exposed to the induction source


20


, a current is created along the surfaces of the heating element


22


. The opening


46


creates a voltage drop; the leads


44


are placed on either side of the opening


46


draw the AC voltage created by this voltage drop. The voltage thus created is then used to power an electronic circuit.





FIGS. 2 and 3

illustrate an alternate embodiment of power supply


42


as a wire coil


50


. The coil


50


can be mounted in physical relationship within the container to be subjected to the magnetic field created by the induction source


20


. The coil


50


can be formed integrally with the heating element


22


. For example, the coil


50


can be etched or plated on to the heating element


22


. Alternately, the coil can be physically separate from the heating element


22


. Exposure of the coil


50


to a magnetic flux


52


created by the induction source


20


induces a current within the coil


50


. The coil


50


includes coil leads


54


which connect to an electronic circuit and provide power from the current created in the coil


50


to the circuit. In the preferred embodiment, the coil


50


is placed in a plane of the heating element


22


nearest the induction source


20


; otherwise the material of the element


22


might interfere with the coil


50


receiving sufficient energy.




As mentioned previously, the supply


42


provides power to a circuit located within the housing


24


. The electronic circuit can be a heat control


30


. The controller


30


can include a temperature sensor


32


, which is arranged to measure the temperature of the heating element


22


. The controller


30


can also include a temperature indicator


34


which can be a light emitting diode, for example. The temperature indicator


34


can be used to indicate that the interior of the housing


24


is at a temperature appropriate for maintaining the warmth of its contents.




The induction powered heating system


10


can also include a communication link


40


. Preferably, the communication link


40


is an infrared link. The communication link


40


, however, can be an ultrasound communication link or a radio communication link. The communication link


40


can include a transmitter


36


and a receiver


38


. The transmitter


36


can be in electrical communication with the controller


30


and the receiver


38


can be in electrical communication with the induction source


20


. The communication link


40


can help form a feedback loop between the temperature sensor


32


and the induction source


20


. In this manner, when the heating element


22


is exposed to a magnetic flux created by the induction source


20


, the temperature of the heating element


22


rises. The temperature sensor


32


then measures the temperature of the element


22


and relays this data to the controller


30


. If the temperature of the heating element


22


is low, the controller


30


sends a signal to the induction source


20


by way of the communication link


40


. This signal causes the inductor


20


to continue to provide a magnetic field, thereby increasing the temperature in the element


22


. If the temperature of the plate


22


rises above pre-determined level or temperature, the controller


30


can send by way of the communication link


40


a signal to the induction source


20


. This signal causes a reduction in power of the magnetic flux produced by the induction source


20


. This same signal can also be used to eliminate the presence of a magnetic flux by placing the induction source in an off mode of operation. By reducing the strength of the magnetic flux or eliminating the magnetic flux, the temperature of the heating element


22


can be reduced. Therefore, the feedback loop can control the temperature of the plate


22


, thereby controlling the temperature within the housing


24


.




In an alternate embodiment, the heating element


22


can be formed of a Curie point metal. By using a Curie point metal for the heating element


22


, a communication link


40


and feedback loop between the temperature sensor


32


and the induction source


20


are not needed. Curie point metals have the property that they will heat only up to a certain temperature and not beyond.




The electronic circuit or controller


30


can have a backup or chargeable power supply which is charged by the power supply


42


. The backup power supply can be a battery or can be a capacitor, for example. When the heating element


22


is placed near the induction source


20


, the magnetic flux energizes the power supply


42


, which can thereby provide energy to charge it.





FIG. 4

shows a block diagram of a circuit


92


for a controller


30


. The controller circuit


92


can be connected to the power source


42


. The controller circuit


92


includes a rectifier


90


, a backup power supply


88


connected to the rectifier


90


, a temperature sensor circuit


60


, a temperature indicator circuit


80


and a blinker circuit


100


. Temperature indicators


34


and a transmitting portion


36


of a communication link


40


are also connected to the circuit


92


.





FIG. 5

illustrates the rectifier circuit


90


in more detail. It converts an AC input signal to a DC output signal and also charges the chargeable power source


88


. The circuit includes input diode bridge


84


which acts to rectify the incoming signal. The chargeable power source


88


includes super capacitors in the illustrated embodiment. The circuit


90


can also include zener diodes


94


which regulate the output voltage, as well as a voltage regulator in circuit U


7


.





FIG. 6

illustrates the temperature controller circuit


60


and the temperature indicator circuit


80


. The temperature controller circuit


60


can include thermostats


62


and the transmitter


36


, which is an infrared diode in the illustrated embodiment. The thermostats


62


include a first thermostat


74


and a second thermostat


76


. The first thermostat


74


can be set so as to engage an off mode of operation when the temperature of the heating element


22


rises above a predetermined high temperature. When the temperature of the heating element


22


is below a pre-determined temperature, the first thermostat


74


is in a normally closed position. In this closed position, current flows through the IR diode, which in turn supplies light to the receiver


38


on the induction source


20


. This signal indicates the need for a maintained or an increased magnetic flux strength. When the temperature of the heating element


22


rises above a preset temperature, the first thermostat


74


engages an open position, at which point the IR diode shuts off. This lack of signal causes the induction source to shut down, and prevents the heating element


22


from overheating.




The controller


30


can also include a temperature indicator circuit


80


. The temperature indicator circuit


80


can include logic gates


96


and a visual temperature indicator


34


. When the heating element


22


is in the process of being heated and is not at its desired, preset temperature level, the first thermostat


74


is in an open state. When the first thermostat


74


is in an open state, a current is provided which causes the indicator


34


to produce a “not ready” warning. For example, if the indicator


34


is a light emitting diode (LED), the current can excite the diode to produce a red color to indicate that the temperature of the heating element


22


is not at a desired level. When the heating element


22


has achieved its desired, preset temperature level, the thermostat


62


is caused to engage a closed state. When the first thermostat


74


is in a closed state, a current is provided to the indicator


34


which causes the indicator to produce a “ready” indication. For example, if the indicator is an LED, the current can excite the diode to produce a green color to indicate that the temperature of the heating element


22


is at a desired level.




The second thermostat


76


can be set so as to engage an off mode of operation when the temperature of the heating element


22


falls below a predetermined low temperature. During operation, the second thermostat


76


is normally in a closed position. When the temperature of the heating element


22


drops below the preset low temperature, the second thermostat


76


opens thereby providing a current to the indicator


34


to provide a “not ready” warning.




Another possible circuit is shown in FIG.


7


. This is a circuit


100


which provides a blinking visual indication as long as the power supply


42


is connected. Such flashing or blinking can continue until the voltage source providing power to the circuit is terminated. For example, when the heating element


22


is removed from the induction source


20


, the chargeable power supply


88


is used to power the blinker circuit


100


. The LED


34


can flash until the power from the chargeable power source is drained. The chargeable power source can, for example, provide power to the circuit for approximately 30 minutes, thereby allowing flashing of the LED


34


for that amount of time. This time frame is the typically expected “hot” time for a pizza delivery.





FIG. 8

illustrates a voltage controlled oscillation circuit, given generally as


110


. The circuit


110


creates a feedback loop between the power supply


42


and the induction source


20


based upon the voltage generated by the power supply


42


. The voltage feedback loop can be used, for example, to increase the field strength from the induction source


20


if the power supply is improperly positioned over the source


20


. The circuit


110


controls the transmitter


36


, such as an infrared LED, such that the transmitter


36


flashes at a particular rate based upon the voltage produced by the power supply


42


. For example, the closer the power supply


42


is to the induction source


20


, the greater the voltage generated within the power supply.




With a relatively high voltage generated by the power supply


42


, the circuit


110


sends a signal to the transmitter


36


which causes the transmitter


36


to flash at a relatively high rate. Conversely, with a relatively low voltage generated by the power supply


42


, the circuit


110


sends a signal to the transmitter


36


which causes the transmitter


36


to flash at a relatively low rate. The signal sent by the transmitter


36


is received by the receiver


38


on the induction source


20


.




The circuits shown here are by way of example only. Many other uses of the supply voltage generated by the supply


42


are possible. For example, the feedback loop formed between the power supply


42


and the induction source


20


could also include a microprocessor to control the loop. Such a microprocessor can be mounted to the housing


24


which holds the heating element


22


and power supply


42


.




While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.



Claims
  • 1. An induction heated container, comprising:a housing; a heating element mounted within the housing wherein the heating element is heated from an induction source; a power supply energized by the induction source; and a circuit powered by the power supply, the circuit further comprising: a backup power supply charged by the power supply.
  • 2. The container of claim 1 wherein the power supply is energized by a magnetic field produced by the induction source.
  • 3. The container of claim 1 wherein the circuit comprises a controller having a temperature sensor, a temperature indicator and a feedback loop formed between the temperature sensor and the induction source.
  • 4. The container of claim 3 wherein the controller further comprises a communication link.
  • 5. The container of claim 1 wherein the housing comprises a thermally insulated material.
  • 6. The container of claim 1 wherein the power supply comprises an induction coil charged by the induction source.
  • 7. The container of claim 1 wherein the circuit comprises a feedback loop formed between the power supply and the induction source.
  • 8. The container of claim 7 wherein the feedback loop comprises a communications link between the power supply and the induction source.
  • 9. The container of claim 1 wherein the backup power supply continues to power the circuit when the power supply is not energized by the induction source.
  • 10. An induction heated container for holding items to be heated comprising:a housing wherein the housing comprises a cavity, the cavity defined by a top surface, a bottom surface and a side wall, the side wall attaching an outer edge of the top surface with an outer edge of the bottom surface and wherein a portion of the side wall is moveably attached to the top surface and the bottom surface; a heating element mounted within the housing, the heating element being heated from an induction source; a power supply energized by the induction source; and a circuit energized by the power supply, the circuit further comprising: a backup power supply charged by the power supply.
  • 11. The container of claim 10 wherein the circuit comprises a controller having a temperature sensor for measuring a temperature of the heating element.
  • 12. The container of claim 11 wherein the controller comprises a feedback loop formed between the temperature sensor and the induction source.
  • 13. The container of claim 11 wherein the controller comprises a temperature indicator.
  • 14. The container of claim 10 wherein the housing comprises thermally insulating material.
  • 15. The container of claim 10 wherein the circuit comprises a feedback loop formed between the power supply and the induction source.
  • 16. The container of claim 15 wherein the feedback loop comprises a communications link between the power supply and the induction source.
  • 17. The container of claim 10 wherein the backup power supply continues to power the circuit when the power supply is not energized by the induction source.
  • 18. A container for heating of food items comprising:a housing; a heating element mounted within the housing wherein the heating element is heated from an induction source; a power supply energized by the induction source; and a circuit powered by the power supply, the circuit further comprising: a backup power supply charged by the power supply.
  • 19. The container of claim 18 wherein the power supply is energized by a magnetic field produced by the induction source.
  • 20. The container of claim 18 wherein the power supply comprises an induction coil charged by the induction source.
  • 21. The container of claim 18 wherein the power supply comprises an opening on the heating element, a first lead and a second lead wherein the opening creates a voltage differential transferred to the first lead and the second lead.
  • 22. The container of claim 18 wherein the circuit comprises a feedback loop formed between the power supply and the induction source.
  • 23. The container system of claim 22 wherein the feedback loop comprises a communication link between the power supply and the induction source.
  • 24. The container system of claim 18 wherein the circuit comprises a controller having a temperature sensor for measuring a temperature of the heating element and a feedback loop formed between the temperature sensor and the induction source.
  • 25. The container of claim 24 wherein the controller further comprises a temperature indicator.
  • 26. The container of claim 24 wherein the feedback loop comprises a communication link between the induction source and the controller.
  • 27. The container of claim 24 wherein the controller comprises the backup power supply, wherein the backup power supply is charged by a power supply.
  • 28. The container of claim 18 wherein the backup power supply comprises a battery.
  • 29. The container of claim 18 wherein the backup power supply comprises a capacitor.
  • 30. The container of claim 18 wherein the housing is thermally insulated.
  • 31. The container of claim 18 wherein the housing comprises a cavity, the cavity defined by a top surface, a bottom surface and a side wall, the side wall attaching an outer edge of the top surface with an outer edge of the bottom surface and wherein a portion of the side wall is moveably attached to the top surface and the bottom surface.
  • 32. The container of claim 18 wherein the heating element is formed of a Curie point metal.
  • 33. The container of claim 18 wherein the induction source comprises a ferrite material.
  • 34. A container for heating food items, comprising:a housing; a heating element mounted within the housing, the heating element being driven by an induction source; an induction-driven power supply energized by the induction source; and a circuit powered by the induction-driven power supply, the circuit further comprising: a backup power supply charged by the induction-driven power supply, the backup power supply continuing to power the circuit when the induction-driven power supply is not energized by the induction source.
  • 35. A container for heating food items, comprising:a housing wherein the housing comprises a cavity, the cavity defined by a top surface, a bottom surface and a side wall, the side wall attaching an outer edge of the top surface with an outer edge of the bottom surface and wherein a portion of the side wall is moveably attached to the top surface and the bottom surface; a heating element mounted within the housing, the heating element being driven by an induction source; an induction-driven power supply energized by the induction source; and a circuit energized by the induction-driven power supply, the circuit further comprising: a backup power supply charged by the induction-driven power supply, the backup power supply continuing to power the circuit when the induction-driven power supply is not energized by the induction source.
RELATED APPLICATION(S)

This application is a Continuation-in-Part of U.S. application Ser. No. 09/678,723, filed Oct. 4, 2000, which claims the benefit of U.S. Provisional Application No. 60/211,562, filed Jun. 15, 2000, and the entire teachings of which are each incorporated herein by reference.

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