US3218429A - Dielectric heating apparatus - Google Patents

Dielectric heating apparatus Download PDF

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Publication number
US3218429A
US3218429A US264398A US26439863A US3218429A US 3218429 A US3218429 A US 3218429A US 264398 A US264398 A US 264398A US 26439863 A US26439863 A US 26439863A US 3218429 A US3218429 A US 3218429A
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US
United States
Prior art keywords
cavity
oscillator
microwave energy
load
magnetron
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US264398A
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English (en)
Inventor
Lenart Tibor
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Electrolux AB
Original Assignee
Electrolux AB
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Filing date
Publication date
Application filed by Electrolux AB filed Critical Electrolux AB
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Publication of US3218429A publication Critical patent/US3218429A/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/66—Circuits
    • H05B6/666—Safety circuits
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/6402—Aspects relating to the microwave cavity
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/647—Aspects related to microwave heating combined with other heating techniques
    • H05B6/6491—Aspects related to microwave heating combined with other heating techniques combined with the use of susceptors
    • H05B6/6494—Aspects related to microwave heating combined with other heating techniques combined with the use of susceptors for cooking
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/70—Feed lines
    • H05B6/705—Feed lines using microwave tuning
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/72—Radiators or antennas
    • H05B6/725—Rotatable antennas
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B40/00—Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers

Definitions

  • dielectric heating apparatus in which heating of material is effected in a cavity of a heater by microwave electrical energy developed by an oscillator, such as a magnetron, for example.
  • a magnetron often is employed for developing ultra high frequency electrical energy as high as 2400 to 2500 mc./s.
  • the electrical energy which is in the form of high frequency electromagnetic waves, referred to as microwaves, is transmitted from the antenna of the magnetron through a wave guide to the cavity of a heater or oven adapted to hold the load or material to be heated. A part of the microwave electrical energy received in the cavity is refiected and transmitted back to the magnetron.
  • the magnetron can be adversely affected when the reflected microwave electrical energy becomes sufliciently great.
  • the reflected electrical energy transmitted back to the magnetron effects objectionable heating of the anode.
  • the magnetron can be electronically damaged by the reflected electrical energy for the reason that the magnetron and load in the cavity form .a system equivalent to two resonant circuits which are coupled together. In the event the resonant frequency of the load is very close to the resonant frequency of the magnetron and the resistive component is small, the magnetron can be forced to oscillate on the new frequency, which will overload the cathode and quickly damage the magnetron.
  • the object of my invention is to construct dielectric heating apparatus of this type which will produce the desired energy transfer from the magnetron to the cavity under all operating conditions ranging from no useful load to normal useful load, whereby the microwave energy reflected in the cavity and transmitted back to the magnetron will always be within safe limits under all conditions encountered in use.
  • a dummy load which consists of a number of damping or energy absorbing bodies disposed in that part of a cavity in which the intensity of the microwave energy received from the magnetron is highest.
  • a wall of the top cavity section 1a has a first apertured zone defining an access opening provided with a door or closure member 3 movable between closed and open positions and through which material to be heated is inserted and removed from the topsection 1a.
  • a receptacle 4 on the partition 2 may be employed to hold the material which constitutes the useful load to be heated.
  • the useful load in the cavity is heated by microwave electrical energy-produced by a magnetron 5 having an antenna 6 coupled thereto, the upper end or apex of as'a connectionbetween the magnetron 5 and the cavity above.
  • connection being in communication with the cavity at a second apertured zone 8 for introducing into the cavity microwave energy supplied by the oscillator or magnetron 5.
  • a movable member 9 at one end of the wave guide 7 is provided with an operating element 10 which is accessible in any suitable manner (not shown) to adjust the wave guide 7 to any length desired.
  • the cavity 1 under normal operating conditions is adapted to receive a normal useful load to be heated, as explained
  • a rotatable member 11 is positioned in the bottom cavity section 1b at a region beneath the partition 2.
  • the member 11 is fixed to the upper end of a vertical shaft 12 which projects downward exteriorly of the bottom cavity section 1b and is arranged to be driven by an electric motor 14.
  • the microwave electrical energy received in the cavity in the form of traveling electromagnetic waves produces an electromagnetic field which is made as homogeneous as possible by'the rotatable member 11 which functions as a stirrer.
  • an artificial or dummy load 15 is provided in the bottom cavity section 1b which is formed of material possessing ability to attract the electromagnetic field and also absorb microwave energy received in the cavity.
  • the dummy load 15 comprises a plurality of elongated bodies 15a and 15b which are supported in upright positions in the bottom cavity section 1b and extend upward from the bottom thereof.
  • the bodies a and 15b are in the form of cones and cylindrical rods, respectively, the lengths of the bodies being about onehalf of the length of the electromagnetic waves sent out or emitted by the magnetron 5.
  • the bodies 15a and 15b desirably are formed of a loss material, such as graphite, for example, and an insulating material, such as a ceramic material, cement or a plastic, for example.
  • the graphite can be mixed with a material selected from a ceramic material, cement or a plastic, which serve as a binding agent in the mixture.
  • the bodies 15a and 15b also may be formed from cone-shaped and cylindrical-shaped metallic members coated with an enamel containing iron powder.
  • the bodies 15:: and 15b in the bottom cavity section 1b are subjected to the alternating current electromagnetic field produced by the microwave energy transmitted from the magnetron 5, heating by dielectric losses results from the periodic stressing and displacement of the atoms of the material in the bodies acting as the dielectric of a capacitor.
  • the loss is due to a property of dielectric material referred to as absorption, and the magnitude of the absorption in the bodies 15a and 15b can be regulated by controlling the proportion of loss and insulating materials in the bodies.
  • the bodies 15a and 15! are imperfect dielectrics, the presence of both loss material and insulating material is necessary.
  • the expression loss factor is often used to indicate the relative heating rates of various dielectrics.
  • the bulk of a body 15a or 1512 is formed of an insulating material in which only a relatively small quantity of graphite is present, the resulting mixture functions as a relatively small condenser having a relatively great loss factor.
  • the capacitance and loss factor of the body can be changed at will.
  • the capacitance of the bodies 15a and 15b determines their ability to attract the electromagnetic field in the cavity, and the loss of the bodies determines what part of the concentrated electromagnetic energy in the bodies is utilized for the production of heat by dielectric losses.
  • the useful load in the receptacle 4 is disposed between the artificial or dummy load and the traveling electromagnetic waves transmitted into the top cavity section 1a through the opening 8 in the wave guide 7. With this arrangement, the useful load in the receptacle 4 will be subjected to direct radiation and effective heating thereof will be promoted.
  • the bodies 15a and 15b forming the dummy or artificial load function as energy absorbing bodies which are disposed in that part of the bottom cavity section 1!) in which the intensity and magnitude of the microwave energy received from the magnetron 5 is highest and the damping effect will be most effective to protect the magnetron.
  • the impedance of the loaded cavity is matched to that of the magnetron to produce the desired energy transfer from the magnetron 5 to the cavity 1 under all operating conditions ranging from normal useful load to no useful load, so that the microwave energy reflected in the cavity 1 and transmitted back to the magnetron 5 will always be within safe limits.
  • Dielectric heating apparatus comprising an oscillator for supplying microwave energy, an oven having Walls providing a cavity, a connection between said oscillator and said cavity, said walls having first and second apertured zones and otherwise being imperforate, the first apertured zone defining an access opening and a closure member therefor movable between closed and open posi tions, said connection being in communication with said cavity at the second apertured zone for introducing into said cavity microwave energy supplied by said oscillator, said cavity when said closure member is moved to its closed position defining a place of heating closed from the surroundings to prevent passage of microwave energy therefrom, said cavity under normal operating conditions being adapted to receive a normal useful load to be heated, means disposed within the walls of said cavity to provide an artificial load for matching said cavity to said oscillator in the absence of a useful load in said cavity, said artificial load means comprising damping body structure disposed within that part of said cavity in which the damping effect will be effective to protect said oscillator, and said damping body structure comprising a plurality of damping bodies, the length of
  • Dielectric heating apparatus comprising an oscillator for supplying microwave energy, an oven having walls providing a cavity, a connection between said oscillator and said cavity, said Walls having first and second apertured zones and otherwise being imperforate, the first apertured zone defining an access opening and a closure member therefor movable between closed and open positions, said connection being in communication with said cavity at the second apertured zone for introducing into said cavity microwave energy supplied by said oscillator, said cavity when said closure member is moved to its closed position defining a place of heating closed from the surroundings to prevent passage of microwave energy therefrom, said cavity under normal operating conditions being adapted to receive a normal useful load to be heated, means disposed within the walls of said cavity to provide an artificial load for matching said cavity to said oscillator in the absence of a useful load in said cavity, said artificial load means comprising damping body structure disposed within that part of said cavity in which the damping effect will be effective to protect said oscillator, and said damping body structure comprising a plurality of damping bodies which are formed from graphite
  • Dielectric heating apparatus comprising an oscillator for supplying microwave energy, an oven having walls providing a cavity, a connection between said oscillator and said cavity, said walls having first and second apertured zones and otherwise being imperforate, the first apertured zone defining an access opening and a closure member therefor movable between closed and open positions, said connection being in communication with said cavity at the second apertured Zone for introducing into said cavity microwave energy supplied by said oscillator, said cavity when said closure member is moved to its closed position defining a place of heating closed from the surroundings to prevent passage of microwave energy therefrom, said cavity under normal operating conditions being adapted to receive a normal useful load to be heated, means disposed within the walls of said cavity to provide an artificial load for matching said cavity to said oscillator in the absence of a useful load in said cavity, said artificial load means comprising damping body structure disposed Within that part of said cavity in which the damping effect will be effective to protect said oscillator, 1
  • said damping body structure comprising a plurality 6 of damping bodies which are formed of metal coated with an enamel containing iron powder.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Constitution Of High-Frequency Heating (AREA)
US264398A 1962-03-14 1963-03-11 Dielectric heating apparatus Expired - Lifetime US3218429A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE280462 1962-03-14

Publications (1)

Publication Number Publication Date
US3218429A true US3218429A (en) 1965-11-16

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ID=20260739

Family Applications (1)

Application Number Title Priority Date Filing Date
US264398A Expired - Lifetime US3218429A (en) 1962-03-14 1963-03-11 Dielectric heating apparatus

Country Status (5)

Country Link
US (1) US3218429A (de)
CH (1) CH412144A (de)
DE (1) DE1285641B (de)
GB (1) GB1029995A (de)
NL (1) NL290163A (de)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3329898A (en) * 1964-10-30 1967-07-04 Itt Cabinet having wall containing strip line for microwave communication system
US3370145A (en) * 1964-04-07 1968-02-20 Philips Corp Arrangement in microwave stoves
US3521019A (en) * 1968-02-19 1970-07-21 Varian Associates Microwave heating cavity with a venetian blind mode stirrer
US3560695A (en) * 1969-02-17 1971-02-02 Varian Associates Microwave applicator employing a flat multimode cavity
US3740514A (en) * 1970-07-01 1973-06-19 Litter Syst Inc Mode-shifting system for microwave ovens
US4099042A (en) * 1975-07-04 1978-07-04 Olivier Jean A Applicator for applying microwaves
US4190757A (en) * 1976-10-08 1980-02-26 The Pillsbury Company Microwave heating package and method
US4223194A (en) * 1978-12-26 1980-09-16 General Electric Company Microwave oven with means for modifying energy distribution therein
US4816632A (en) * 1987-01-08 1989-03-28 U.S. Philips Corporation Multi-resonant microwave oven having an improved microwave distribution
FR2681410A1 (fr) * 1991-09-13 1993-03-19 Toshiba Kk Appareil de chauffage par les hautes frequences.
US5272302A (en) * 1991-12-17 1993-12-21 Raytheon Company Microwave oven with improved cooking uniformity
US5698128A (en) * 1995-03-13 1997-12-16 Sanyo Electric Co. Microwave oven with a projection for uniform heating within the cavity
WO2015127999A1 (en) * 2014-02-28 2015-09-03 Arcelik Anonim Sirketi Microwave oven having a physically adjustable waveguide dynamically displaced by a movement control means

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4121078A (en) * 1975-04-30 1978-10-17 Matsushita Electric Industrial Co., Ltd. Microwave heating apparatus
JPS565904U (de) * 1980-06-10 1981-01-20
US4446349A (en) * 1983-01-03 1984-05-01 General Electric Company Microwave phase shifting device

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2207845A (en) * 1938-05-28 1940-07-16 Rca Corp Propagation of waves in a wave guide
US2584162A (en) * 1948-12-15 1952-02-05 Sperry Corp Impedance matching device for wave guide junctions
US2704802A (en) * 1952-05-22 1955-03-22 Raytheon Mfg Co Microwave ovens
US2804598A (en) * 1946-02-08 1957-08-27 Roberto M Fano Wave guide termination
US2820127A (en) * 1953-03-30 1958-01-14 Raytheon Mfg Co Microwave cookers
US2827537A (en) * 1953-11-12 1958-03-18 Raytheon Mfg Co Electronic heating apparatus
US2961520A (en) * 1957-04-02 1960-11-22 Gen Motors Corp Domestic appliance
US2977591A (en) * 1952-09-17 1961-03-28 Howard A Tanner Fibrous microwave absorber

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2207845A (en) * 1938-05-28 1940-07-16 Rca Corp Propagation of waves in a wave guide
US2804598A (en) * 1946-02-08 1957-08-27 Roberto M Fano Wave guide termination
US2584162A (en) * 1948-12-15 1952-02-05 Sperry Corp Impedance matching device for wave guide junctions
US2704802A (en) * 1952-05-22 1955-03-22 Raytheon Mfg Co Microwave ovens
US2977591A (en) * 1952-09-17 1961-03-28 Howard A Tanner Fibrous microwave absorber
US2820127A (en) * 1953-03-30 1958-01-14 Raytheon Mfg Co Microwave cookers
US2827537A (en) * 1953-11-12 1958-03-18 Raytheon Mfg Co Electronic heating apparatus
US2961520A (en) * 1957-04-02 1960-11-22 Gen Motors Corp Domestic appliance

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3370145A (en) * 1964-04-07 1968-02-20 Philips Corp Arrangement in microwave stoves
US3329898A (en) * 1964-10-30 1967-07-04 Itt Cabinet having wall containing strip line for microwave communication system
US3521019A (en) * 1968-02-19 1970-07-21 Varian Associates Microwave heating cavity with a venetian blind mode stirrer
US3560695A (en) * 1969-02-17 1971-02-02 Varian Associates Microwave applicator employing a flat multimode cavity
US3740514A (en) * 1970-07-01 1973-06-19 Litter Syst Inc Mode-shifting system for microwave ovens
US4099042A (en) * 1975-07-04 1978-07-04 Olivier Jean A Applicator for applying microwaves
US4190757A (en) * 1976-10-08 1980-02-26 The Pillsbury Company Microwave heating package and method
US4223194A (en) * 1978-12-26 1980-09-16 General Electric Company Microwave oven with means for modifying energy distribution therein
US4816632A (en) * 1987-01-08 1989-03-28 U.S. Philips Corporation Multi-resonant microwave oven having an improved microwave distribution
FR2681410A1 (fr) * 1991-09-13 1993-03-19 Toshiba Kk Appareil de chauffage par les hautes frequences.
US5272302A (en) * 1991-12-17 1993-12-21 Raytheon Company Microwave oven with improved cooking uniformity
US5698128A (en) * 1995-03-13 1997-12-16 Sanyo Electric Co. Microwave oven with a projection for uniform heating within the cavity
WO2015127999A1 (en) * 2014-02-28 2015-09-03 Arcelik Anonim Sirketi Microwave oven having a physically adjustable waveguide dynamically displaced by a movement control means
CN106031304A (zh) * 2014-02-28 2016-10-12 阿塞里克股份有限公司 具有由移动控制构件动态移位的物理可调节波导的微波炉

Also Published As

Publication number Publication date
NL290163A (de)
GB1029995A (en) 1966-05-18
DE1285641B (de) 1968-12-19
CH412144A (de) 1966-04-30

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