Wireless food temperature-sensing assembly

• US 4,475,024 A
• Filed: 01/10/1983
• Issued: 10/02/1984
• Est. Priority Date: 04/10/1978
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Tateda, Koichi
• Primary Examiner(s): Envall, Jr., Roy N.
• Assistant Examiner(s): Leung, Philip H.
• Application Number:
  US06/456,669
• Time in Patent Office: 631 Days
• Field of Search: 219/10.55 B, 219/10.55 R, 219/10.55 E, 219/10.55 F, 219/10.55 M, 340/870.26, 340/584, 340/588, 340/589, 340/596, 340/207 R, 340/210, 340/224, 340/417, 340/227 R, 340/228 R, 99/326, 99/329 R, 99/342, 325/37, 325/494, 325/185, 310/318, 343/6.5 SS, 343/6.5 R, 73/343.5, 374/117, 374/149, 374/155, 324/61 QL, 324/60 P
• US Class Current: 219/713
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 2207/06 for preparation purposes
• CPC Class Codes: G01K 5/62 the solid body being formed of compounded strips or plates, e.g. bimetallic strip
• CPC Class Codes: G01K 5/72 with electric transmission means for final indication
• CPC Class Codes: H05B 6/6452 the sensors being in contact with the heated product
• CPC Class Codes: H05B 6/6467 using detectors with R.F. transmitters
• CPC Class Codes: H05B 6/6482 combined with radiant heating, e.g. infrared heating

Abstract

The present invention is directed to a cooking utensil such as a microwave oven wherein a food temperature-sensing probe is inserted into a foodstuff for detecting the internal temperature of the food. The food temperature-sensing probe includes a resonance circuit the resonance frequency of which varies depending on the internal temperature. A first signal generator is provided for delivering a series of signals which contain a variety of frequencies inclusive of the signals of the resonance frequency. A second signal generator is employed to provide sweeping signals for the series of signals developed from the first signal generator. A selecting circuit is connected to the second signal generator for selecting a particular value in the sweeping signals relevant to the desired temperature of the foodstuff. A wireless controlled circuit is provided which determines the occurence of the dip phenomena in a relationship with the particular value in the sweeping signals under the radiation of the series of signals generated from the first signal generator.

Claims

1. A microwave oven for varying the temperature of a foodstuff, comprising:

microwave generation means for heating said foodstuff by application of microwaves thereto;

resonance circuit means having a resonance frequency which varies in response to the temperature of said foodstuff;

first transmitter means for providing a series of driving signals inclusive of signals of the various resonance frequencies of said resonance circuit means;

second means for selecting a particular frequency of said series of driving signals corresponding to a desired set temperature of said foodstuff;

said transmitter means having a parameter which varies in response to a condition of resonance in said resonance circuit means;

third means, responsive to said second means and the variation in said parameter of said transmitter means for detecting the coincidence of said variation and a said particular driving signal frequency representative of said desired set temperature and providing an output signal in response thereto; and

means responsive to said output signal for controlling said microwave generation means to heat said foodstuff to said desired set temperature.

2. The cooking utensil according to claim 1 wherein said resonance circuit is electrically connected to a probe inserted into the foodstuff to detect the internal temperature of the same, the probe comprising a thermally-responsive element.

3. The cooking utensil according to claim 2, wherein said resonance circuit means comprises an inductance element and a capacitance element and said thermally-responsive element contained within said probe includes means for varying the resonance frequency of said resonance circuit.

4. The cooking utensil according to claim 3, wherein said thermally-responsive element comprises bimetallic drive means and timing means driven thereby for varying said resonance frequency as a function of foodstuff temperature.

5. The cooking utensil according to claim 4, wherein said thermally-responsive element comprises capacitor means, the capacitance of which varies depending on the temperature, and said resonance circuit means comprises said capacitor means and an inductance element.

6. The cooking utensil according to claim 1, wherein said transmitter means comprises a wireless communication means for propagating said driving signals to said resonance circuit means.

7. The cooking utensil according to claim 6, wherein said parameter of said transmitter means is an amplitude of said driving signals which reduces in response to a resonance condition in said resonance circuit means.

8. The cooking utensil according to claim 1, wherein said second means comprises:

sweeping signal generator means for providing sweep signals of a saw tooth waveform which are applied to said transmitter means to control the frequencies of said driving signals; and

setting means for selecting a particular value of said sweep signals corresponding to said desired set temperature.

9. The cooking utensil according to claim 8, wherein the cycles of said sweep signals developed from said sweeping signal generator means are much smaller than the time period when the foodstuff is cooked and said third means is operated in each cycle of said sweep signals.

10. The cooking utensil according to claim 1, wherein said parameter of said transmitter means is an amplitude of said driving signals which reduces in response to a resonance condition in said resonance circuit means.