[54]
`
`[75]
`
`[73]
`
`United States Patent
`Matsumoto
`
`[19]
`
`[11] Patent Number:
`
`5,580,594
`
`[45] Date of Patent:
`
`Dec. 3, 1996
`
`Illlllllllllllllllllll|Il|||l||||ll|lllllllllllllllllllllllllllllllllllllll
`USOO5580594A .
`
`METHOD FOR COOKING FOOD WITH
`EDDY-CURRENT GENERATED HEAT
`
`[56]
`
`References Cited
`U.s. PATENT DOCUMENTS
`
`Inventor: Kesafumi Matsumoto, Atsugi, Japan
`
`Assignee: Kouken Company, Limited,
`Kanagawa-ken, Japan
`
`[21]
`
`Appl. N0.: 498,962
`
`[22]
`
`I
`Jul. 6, 1995
`Filed:
`Foreign Application liriority Data
`[30]
`Oct. 25, 1994
`[JP]
`Japan .................................. .. 6-260046
`
`Int. Cl.6 ..................................................... .. H05B 6/00
`[51]
`[52] U.S. Ci............................ .. 426/243; 99/451; 219/622;
`426/523
`[58] Field of Search ..................................... 426/241, 243,
`426/248, 523; 99/451, DIG. 14; 219/622,
`649
`
`3,902,044
`5,094,865
`5,486,683
`
`............................ .. 99/440
`s/1975 Doyle etal.
`3/1992 Levinson ........... .;.................. .. 426/243
`1/1996 Shimizu etal.
`................... 99/DIG. 14
`
`Primary Examiner—George Yeung
`Attorney, Agent, or Firm—Jordan and Hamburg
`
`[57]
`
`ABSTRACT
`
`A utensil body 1 and a lid 2 are made of a metallic magnetic
`material which generates heat when eddy currents are
`induced therein in order to cook food with heat which is
`applicable to any of boiling, steaming, sauteing, frying,
`casseroling, and ba.king or roasting, which utilizes the uten-
`sil body 1 applicable to both gas combustion heating and
`eddy-current heating, and which allows cooking to be per-
`formed using water, oil or air as a cooking medium.
`
`1 Claim, 1 Drawing Sheet
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`Euro-Pro Exhibit 1009
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`Euro-Pro Exhibit 1009
`Euro-Pro v. Acorne
`Page 1 of 5
`IPR2014-00186
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`

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`U.S. Patent
`
`Dec. 3, 1996
`
`5,530,594
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`5,580,594
`
`1
`METHOD FOR COOKING FOOD WITH
`EDDY-CURRENT GENERATED HEAT
`
`BACKGROUND OF THE INVENTION
`
`‘
`
`The present invention relates to a method of applying heat
`to food for preparing food without using fire at indoors,
`particularly at resorts and the like, and a utensil directly used
`for carrying out the method.
`Cooking methods are roughly classified as boiling, steam-
`ing, sauteing, frying, casseroling, and baking or roasting.
`Heating methods are divided into a traditional heating
`method using combustion gas and a modern fireless heating
`method by high-frequency heating or eddy-current heating.
`Water, oil and air are used as a thermal medium in a
`heating utensil.
`Cooking utensils of glass or earthenware for boiling,
`steaming, sauteing, frying, easseroling, baking or roasting
`can be heated by burning gas, but carulot be heated by
`eddy-currents. These materials also have the drawback that
`they break easily when exposed to excessive heat or when
`subject to a physical external force, such as dropping or
`shock.
`
`Metallic materials available are aluminum, copper, stain-
`less steel, and iron. The first
`three materials have the
`drawback that they cannot be applied to utensils for cooking
`by eddy-current heating. Enameling has the drawback of the
`surface material separating when heated without water.
`Heating by gas has the advantage of quick heating and
`low cost, but has disadvantages, such as scorching caused by
`failure to turn off fire and danger of gas poisoning or
`explosion caused by extinction during cooking with a slow
`fire or by gas which leaks from the equipment in use.
`Eddy—eurrent heating has the following disadvantages:
`slow heating, high cost of an eddy-current generating unit,
`and high cost of energy due to the use of electricity. This
`heating method, however, has the following advantages:
`ability to heat with weak electric power, heating at a fixed
`temperature, and no danger of gas poisoning or explosion as
`a result of fire not being used.
`
`SUMMARY OF THE INVENTION
`
`Major objects of the present
`described below.
`
`invention will now be
`
`An object of the present invention is to provide a method
`and utensil for cooking food with heat which can be appli-
`cable to any of boiling, steaming, sauteing, frying, casse-
`roling, and baking or roasting.
`Another object of the present invention is to provide a
`utensil for cooking food with heat applicable to heating both
`by burning gas and by eddy currents.
`A further object of the present invention is to provide a
`method and utensil for cooking food with heat in which the
`food can be cooked using water, oil, or air as a cooking
`medium.
`
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`A first feature of a method for cooking food with heat
`according to the present
`invention is as follows. Eddy
`currents induced by eddy-current generating means in a
`main magnetic path in the bottom of a utensil body, in which
`food to be cooked is placed, flow through a continuous
`magnetic path formed endlessly over a side magnetic path in
`a sidewall and a top magnetic path in a lid at a rate inversely
`proportional
`to respective reluctances. Heat generating
`energy produced by eddy currents induced in the main
`magnetic path in the bottom of the utensil body is radiated
`to the inside of the utensil body as far-infrared radiation.
`Outward diffusion of the far-infrared radiation is suppressed
`by far-infrared radiation which is derived from heat gener-
`ating energy of the side and top magnetic paths and which
`is directed toward the inside of the utensil body, thereby
`preventing a loss of cooking energy caused by the far-
`infrared radiation from the main magnetic path diffusing
`toward the outside of the sidewall and the lid in order to
`
`improve a heat insulation effect.
`A first feature of a utensil for cooking food with heat
`according to the present invention resides in the combination
`of a utensil body and a lid both of which are made of a
`material which generates heat when eddy currents flow
`therethrough.
`A second feature of the utensil according to the present
`invention is that the bottom of the utensil in the first feature
`has a wide flat surface which will be contacted with an
`eddy-current generator of an eddy-current generating unit.
`A third feature of the utensil according to the present
`invention is that the material in the first or second feature is
`
`a metallic magnetic material allowing a magnetic path to be
`freely formed therein.
`A fourth feature of the utensil according to the present
`invention is that the lid in the first, second or third feature is
`made of a material that does not get hot even when eddy
`currents flow therethrough.
`The present invention employs the above-described new
`method and structural means. The utensil according to the
`present invention comprises a combination of a pan type
`utensil body having an opening facing up and a lid for
`covering the opening. Both the utensil body and the lid are
`made of a material which generates heat by eddy currents.
`The bottom of the utensil body is finished flat for easy
`contact with the surface of an eddy-current generating unit.
`The lid of a material similar to that of the utensil body is put
`on the utensil body to improve heating and heat insulating
`elfects.
`
`Metallic magnetic materials exhibit heat generating char-
`acteristics when eddy currents are induced therein, and do
`not break as glass and earthenware do. Preferably, the lid
`should be of a material that does not get hot even when eddy
`currents are induced.
`
`Still another object of the present invention is to provide
`a utensil for cooking food with heat having a hard—to-break
`property.
`Other objects of the present invention will become appar-
`ent from the specification and a drawing, and particularly
`from the scope of the appended claims.
`The above-mentioned problems are solved by employing
`new techniques and means of constmction provided by the
`present invention. They are described below item by item.
`
`60
`
`65
`
`DESCRIPTION OF THE DRAWINGS
`
`Various other objects, features and many of the attendant
`advantages of the present invention will be readily appre-
`ciated as the same becomes better understood by reference
`to the following detailed description of the preferred
`embodiments when considered in connection with the
`accompanying drawings, in which:
`.
`FIG. 1 is a central vertical section of the apparatus
`according to the embodiment of the present invention.
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`5,580,594
`
`3
`DETAILED DESCRIPTION OF THE
`EXEMPLARY EMBODIMENT
`
`An apparatus according to an embodiment of the present
`invention will now be described, by way of example, with
`reference to a drawing.
`FIG. 1 is a central vertical section of the apparatus
`according to the embodiment of the present invention.
`In the figure, symbol A denotes a utensil for cooking food
`with heat according to the embodiment. 1 denotes a utensil
`body, 2 denotes a lid, 3 denotes an eddy-current generating
`unit, 4 denotes a bottom, 5 denotes a circumferential side-
`wall, 6 denotes a main magnetic path, 7 denotes a side
`magnetic path, 8 denotes a top magnetic path, 9 denotes an
`eddy-current generator, 10 denotes a temperature detector,
`11 denotes a power cord, 12 denotes a plug, and ot denotes
`an object to be heated.
`The utensil body 1 and the lid 2 are of a metallic magnetic
`material which generates heat when eddy currents are
`induced therein and which allows magnetic paths 6, 7, 8 to
`be formed therein. Preferably, the lid 2 is of such a material
`that does not get hot even when eddy currents are induced
`therein.
`
`The bottom 4 of the utensil body 1 is formed into a flat
`surface with a wide contact area which will be contacted
`with the surface of the eddy—current generator 9 of the
`eddy-current generating unit 3. The bottom 4 is magnetized
`to form the main magnetic path 6 therein.
`The present embodiment assumes the above specific
`mode for carrying out the present invention. Next, how the
`present embodiment works will be described.
`Of cooking methods of boiling, steaming, sauteing, fry-
`ing, casseroling, and baking or roasting, boiling, steaming,
`sauteing, and frying use water or oil as a thermal medium,
`and hence their heat transfer is mainly carried out by contact
`therebetween.
`
`Casseroling involves heat transfer both through far infra-
`red radiation and through air. Hence, the description of the
`present embodiment below will
`take up this cooking
`method.
`
`Sweet potato was selected as the object Ot to be heated.
`This is because sweet potato has various advantages includ-
`ing the following: its internal temperature can be indirectly
`measured with a needle-like sensor used as the temperature
`detector 10; its shape remains intact at room temperature and
`atmospheric pressure; and it allows the cooking temperature
`to be raised to 100° C. or higher.
`As shown in FIG. 1, the plug 12 is inserted into an outlet,
`and the apparatus according to the present embodiment is
`placed on the eddy—current generating unit 3. Eddy currents
`are generated by the eddy—current generator 9. The bottom 4
`of the utensil body 1 is heated by inducing eddy currents in
`the main magnetic path 6.
`.
`Heat thus generated heats the inside of the utensil body 1
`and also heats the object oz to be heated as time passes. A
`casserole of sweet potato will be prepared after maintaining
`an inner temperature T3 of the sweet potato at 100° to 105°
`C.
`
`Heat balance among relevant portions is as follows:
`T0=2O° C.
`T1=26O° C.
`T2=2OO° C.
`T3=10O° to 105° C.
`T4=180° C.
`T5=75° C.
`
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`4
`where TO: ambient temperature, T1: surface temperature of
`eddy—current generating unit 3, T2: surface temperature of
`bottom 4 of utensil body 1, T3: inner temperature of object
`0t to be heated, T4: inner temperature of utensil body 1, and
`T5: surface temperature of lid 2.
`A cooking method to be applied to the apparatus accord-
`ing to the present embodiment will now be described, by
`Way of example, with reference to FIG. 1.
`According to the principle of the cooking method, the
`eddy—current generator 9 of the eddy—current generating unit
`3 induces eddy currents in the bottom 4 of the utensil body
`1, and the inside of the bottom 4 of the utensil body 1 serves
`as the main magnetic path 6 to convert energy of thus
`induced eddy currents to heat.
`Eddy currents induced in the bottom 4 of the utensil body
`1 flow through the side magnetic path 7 and the top magnetic
`path 8, which are continuously formed in the circumferential
`sidewall 5 and the lid 2, at a rate inversely proportional to
`respective reluctances. Accordingly,
`the circumferential
`sidewall 5 and the lid 2 are also heated.
`Heat generating energy produced by eddy currents
`induced in the main magnetic path 6 in the bottom 4 of the
`utensil body is radiated as far-infrared radiation L1.
`The use of a metallic magnetic material for the circum-
`ferential sidewall 5 of the utensil body 1 and the lid 2 seems
`to cause a large loss due to high thermal conductivity.
`However, far—infrared radiation L2 from the magnetic paths
`7, 8 in the circumferential sidewall 5 of the utensil body 1
`and the lid 2 suppresses outward diffusion of the cooking
`far—infrared radiation L1.
`Thus, a loss of energy diffusing outward from the cir-
`cumferential sidewall 5 and the lid 2 is prevented, thereby
`improving the heat insulation eifect. Accordingly, a cost
`raising factor stemming from the use of electricity can be
`reduced to some extent.
`In the above description, heat generation, a major heat
`transfer path, and a thermally insulated method in waterless
`cooking are shown. When water or oil is used for cooking,
`heat transfers from the bottom 4 of the utensil body 1 by
`contact
`therewith. The present embodiment employs a
`metallic magnetic material for the lid 2. However, the lid 2
`may be of a material that does not get hot even when eddy
`currents are induced therein. Such material allows a user to
`directly hold the lid 2 with a hand.
`As has been described above, according to the present
`invention, no fire is used, and the temperature of the contact
`surface between a heating unit and a utensil is as low as
`T,=260° C. Accordingly, the present invention is free from
`risks of gas explosion and fire, which could be caused by
`extinction during cooking with a slow fire or gas which leaks
`from equipment in use, which are peculiar to combustion
`gas. Of course, the present invention is free from any danger
`of a gas explosion.
`In contrast with a conventional electric heater in which
`the temperature of a heat generating portion such as a
`Nichrome wire rises to 600°—888° C., there is no danger of
`a tire or burning even when a user touches an apparatus of
`the present invention.
`Furthermore,
`the present invention can provide a safe
`cooking utensil which does not break when exposed to
`excessive heating or an external impulse force, or when
`being dropped, thus exhibiting excellent practicability and
`usefulness.
`What is claimed is:
`1. A method for cooking food with heat, comprising:
`inducing eddy currents by eddy—current generating means
`in a main magnetic path in the bottom of a utensil body
`Page 4 of 5
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`5,580,594
`
`5
`means, in which the food to be heated is placed, to flow
`through a continuous magnetic path formed endlessly
`over a side magnetic path in a sidewall and a top
`magnetic path in a lid means at a rate inversely pro-
`portional to respective reluctances;
`producing heat generated energy by the eddy currents
`induced in the main magnetic path in the bottom of the
`utensil body means;
`radiating said heat generated energy to the inside of the
`utensil body means as far-infrared radiation;
`cooking food in the inside of said utensil body means
`utilizying said radiated heat generated energy which
`has been radiated to the inside of said utensil body
`means;. and
`
`6
`
`suppressing the outward diifusion of the far-infrared
`radiation from the main magnetic path by the far-
`infrared radiation which is derived from the heat gen-
`erated cncrgy of the side and top magnetic paths and
`which is directed toward the inside of the utensil body
`means,
`
`10
`
`thereby preventing loss of cooking energy caused by the
`far-infrared radiation from the main magnetic path
`diffusing toward the outside of the sidewall and the lid
`means in order to improve heat insulation effect.
`
`*
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`Page 5 of 5
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