INDUCTION COOKING APPLIANCE INCLUDING TEMPERATURE SENSING OF INDUCTIVELY HEATED COOKING VESSEL

• US 3,786,220 A
• Filed: 12/29/1971
• Issued: 01/15/1974
• Est. Priority Date: 12/29/1971
• Status: Expired due to Term

• Current Assignee: Jr Harnden
• Original Assignee: Jr Harnden
• Inventors: Harnden, Jr
• Primary Examiner(s): Reynolds, Bruce A.
• Application Number:
  US05/213,350
• Time in Patent Office: 748 Days
• Field of Search: 219/10.49,10.77,10.79,450,449,516,456 338/22,23 73/362AR
• US Class Current: 219/622
• CPC Class Codes: F24C 15/105 Constructive details concerning the regulation of the temperature
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor
• CPC Class Codes: H05B 2213/07 Heating plates with temperature control means
• CPC Class Codes: H05B 6/062 for cooking plates or the like

Abstract

Disclosed herein is an induction range having a counter including a top surface on which a cooking vessel is rested. A temperature sensing unit is located in an opening in the counter. The temperature sensing unit includes a low-restoring-force spring diaphragm which supports a thermistor unit. The temperature sensing unit forms a closure for the opening in the counter such that the temperature sensing unit together with the top surface of the counter provides an uninterrupted work surface which may be easily cleaned. Because energization of an induction coil positioned near the counter induces high frequency heating currents in the vessel only, and because the temperature sensing unit and induction coil are located relative to each other so that the temperature sensing unit is in a region of relatively low magnetic field intensity, the counter and the temperature sensing unit are not directly heated by the action of the induction coil. Hence, materials not employable in prior art conventional electric and gas ranges may now be employed for the counter and temperature sensing unit. Since the spring diaphragm has a low restoring force it is easily compressed by the cooking vessel, enabling the thermistor unit, or temperature sensor, to make positive contact with the vessel in order to sense its temperature. Also, being of a thin elastic material, the spring diaphragm easily contours itself to the irregular surface of cooking vessels. Permanent magnet means may be combined with the diaphragm in order to achieve a more positive coupling with magnetically permeable cooking vessels.

Claims

1. An induction cooking appliance, for heating a vessel which has at least one portion in which electric current may be induced in order to heat said one portion of said vessel, comprising:

vessel supporting means for supporting said vessel, said vessel supporting means being of a material in which no substantial amount of current is induced when said vessel supporting means is subjected to a changing magnetic field, said vessel supporting means having a surface on which said vessel is supportable, said vessel supporting means including an opening therein which communicates with said surface;

an induction coil energizable for generating a changing magnetic field within which said one portion of said vessel is located whereby electric current is inducted in said one portion of said vessel thereby heating said one portion;

an electric power source;

a power conversion circuit coupled with said power source and said induction coil, said conversion circuit converting the power of said source to electric power of at least ultrasonic frequency and energizing said induction coil with the electric power of said at least ultrasonic frequency; and

, a temperature sensing unit comprising spring means and temperature sensing means supported by said spring means, said spring means and supported temperature sensing means being located in said opening in said vessel supporting means, at least said spring means forming a closure for said opening in said vessel supporting means, said closure together with said surface of said vessel supporting means providing a substantially uninterrupted working surface on said vessel supporting means, said spring means having a relatively low restoring force and being compressible by said vessel as said vessel contacts said spring means when said vessel is being supported on said surface of said vessel supporting means, said temperature sensing means supported by said spring means being proximate said at least one portion of said vessel as said vessel contacts said spring means when said vessel is being supported on the surface of said vessel supporting means whereby said temperature sensing means senses the temperature of said at least one portion of said vessel, said spring means and said temperature sensing means being of materials in which no substantial amount of current is induced when said spring means and said temperature sensing means are subjected to a changing Magnetic field, said spring means being a diaphragm of elastic permanent magnet material which forms said closure for said opening in said vessel supporting means and which exerts a relatively low restoring force when compressed by said vessel and which conforms to the contour of that part of the vessel which is in compressive contact with said diaphragm, said diaphragm exerting an attractive magnetic force on said part of said vessel which is in compressive contact with said diaphragm when said part is of magnetically permeable material.

2. An induction cooking appliance, for heating a vessel which has at least one portion in which electric current may be induced in order to heat said one portion of said vessel, comprising:

vessel supporting means for supporting said vessel, said vessel supporting means being of a material in which no substantial amount of current is induced when said vessel supporting means is subjected to a changing magnetic field, said vessel supporting means having a surface on which said vessel is supportable, said vessel supporting means including an opening therein which communicates with said surface;

an induction coil energizable for generating a changing magnetic field within which said one portion of said vessel is located whereby electric current is inducted in said one portion of said vessel thereby heating said one portion;

an electric power source;

a power conversion circuit coupled with said power source and said induction coil, said conversion circuit converting the power of said source to electric power of at least ultrasonic frequency and energizing said induction coil with the electric power of said at least ultrasonic frequency; and

a temperature sensing unit comprising spring means and temperature sensing means supported by said spring means, said spring means and supported temperature sensing means being located in said opening in said vessel supporting means, at least said spring means forming a closure for said opening in said vessel supporting means, said closure together with said surface of said vessel supporting means providing a substantially uninterrupted working surface on said vessel supporting means, said spring means having a relatively low restoring force and being compressible by said vessel as said vessel contacts said spring means when said vessel is being supported on said surface of said vessel supporting means, said temperature sensing means supported by said spring means being proximate said at least one portion of said vessel as said vessel contacts said spring means when said vessel is being supported on the surface of said vessel supporting means whereby said temperature sensing means senses the temperature of said at least one portion of said vessel, said spring means and said temperature sensing means being of materials in which no substantial amount of current is induced when said spring means and said temperature sensing means are subjected to a changing magnetic field, said spring means being comprised of an elastic diaphragm and separate permanent magnet means supported by said diaphragm, said diaphragm and permanent magnet means forming said closure for said opening in said vessel supporting means, said diaphragm exerting a relatively low restoring force when compressed by said vessel, said diaphragm conforming to the contour of that part of the vessel which is in compressive contact with said diaphragm, said permanent magnet means exerting an attractive magnetic force on said part of said vessel which is in compressive contact with said diaphragm when said part is of magnetically permeable material.