US3798759A - Method of making electric heating unit - Google Patents

Method of making electric heating unit Download PDF

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Publication number
US3798759A
US3798759A US00332622A US33262273A US3798759A US 3798759 A US3798759 A US 3798759A US 00332622 A US00332622 A US 00332622A US 33262273 A US33262273 A US 33262273A US 3798759 A US3798759 A US 3798759A
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US
United States
Prior art keywords
heating
conductor
embedding compound
wire
heating unit
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
US00332622A
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English (en)
Inventor
H Gerds
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.)
SEG Hausgeraete GmbH
Original Assignee
Siemens Elektrogaerate GmbH
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Filing date
Publication date
Application filed by Siemens Elektrogaerate GmbH filed Critical Siemens Elektrogaerate GmbH
Application granted granted Critical
Publication of US3798759A publication Critical patent/US3798759A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H05B3/00—Ohmic-resistance heating
    • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
    • H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
    • H05B3/28—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor embedded in insulating material
    • H05B3/30—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor embedded in insulating material on or between metallic plates
    • 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
    • H05B3/00—Ohmic-resistance heating
    • H05B3/68—Heating arrangements specially adapted for cooking plates or analogous hot-plates
    • H05B3/688—Fabrication of the plates
    • 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/49082—Resistor making
    • Y10T29/49083—Heater type

Definitions

  • ABSTRACT [30] Foreign Application Priority Data Feb. 17 1972 Germanv N 2207343 A heating unit for use in heating plates used for cooking, irons, and the like in which a conventional helical 52 us. c1 29/611, 219/462, 219/464 heater Wire is Pressed Provide a S 511 1111.01.
  • heating units The most conventional manner of forming heating units is to use a heater wire in the form of a wire helix, with the coils of the helix located in a plane essentially perpendicular to the plane of the heating surface of the heating unit.
  • This type of construction lends itself to ease of manufacture but results in an unsatisfactory heat transfer. Since not all of the heater wire is equidistant from the surface to be heated most efficient heating is not obtained.
  • This problem has been solved, at least to a small degree, in some prior art devices by installing heat conduction ribs and using a relatively thick embedding compound layer surrounding the heating coils. This solution is somewhat costly requiring excessive amounts of embedd-ing compound which make warmup take longer and limit the response of the unit to control changes.
  • the heating wire within the heating plate lies in a plane which is parallel to the heating surface of the unit.
  • the heating wire should meander or zig-zag through the embedding compound in which it is installed to obtain the maximum effective heating wire area. With the wire flat in the plane parallel to the heating plane, a maximum heat transfer will take place. Because the wire is flat the embedding compound may be thin and the above noted problems will not be present.
  • prior art methods of constructing this type of heating unit have not been particularly efficient. In general, the heating conductors have been stamped out in the desired form from sheet stock consisting of appropriate resistance material. The processes used have considerable waste and are expensive to employ, thus resulting in a costly final product.
  • the apparatus and method of the present invention provide a solution to this problem allowing a heating unit to be constructed at a low cost, which unit has its heating wires lying in a plane parallel to the heating surface.
  • the heating unit will comprise a support plate, e.g., the top of a heating plate or the bottom of an iron, in which a heating coil or conductor follows a zig-zag or S type path in an embedding compound, in which it is embedded.
  • the embedding compound is placed on the side of the support plate opposite the heating surface, the flat coil installed, and then covered with further embedding material.
  • the coil which follows a zigzag or S shaped path and lies in a plane parallel to the heating surface is formed by stretching a conventional circular helix coil to the desired length, placing it in a die which has the desired shape of the final heating element, and pressing it in that die, so that the helical curved portions are flattened out to form a flat zig-zag or S shaped coil path.
  • the flattened coil may be removed from the die by pressing it against an adhesive foil backing, and then transferred with the adhesive foil to a partially set embedding compound which has been placed on one side of the support plate and allowed to dry therein, after which the adhesive backing can be removed and a further layer of embedding compound placed over the coil to provide heat insulation.
  • the heating unit made according to the present invention will have a low heat capacity which will result in a very short heating up time and improved control properties. As compared to conventional cast plates with internally arranged ribs, the amount of reduction in material is substantial, thus allowing a significant reduction in cost.
  • FIG. 1 is a cross-sectional elevation view of a heating unit constructed according to the present invention.
  • FIG. 2 is a cross-sectional plan view of the same heating unit as shown on FIG. 1.
  • FIG. 3 is a cross-sectional view of a press apparatus which may be used to flatten the heating conductor used in the embodiment of FIGS. 1 and 2.
  • the heating unit constructed according to the present invention is illustrated by FIGS. 1 and 2.
  • the unit comprises a support plate 1 with sloping sides 1 1, a first layer of embedding compound 2 in which are embedded the conductors 4,and an additional layer of heat insulating embedding compound 3.
  • the support plate 1 may be stamped out of sheet steel or alternately may comprise another metal, ceramic glass material or the like.
  • the layers of embedding compound, the composition of which will be described below, will have thicknesses in the range of 1 to 3 millimeters.
  • the coils are placed into the embedding compound layer 2 so as to be just completely immersed therein in a manner to be described below. As shown on FIG.
  • the conductor 4 is arranged in a spiral path while at the same time zigzagging to cover more area. It should benoted that this is only used as an example and other arrangements are possible. This arrangement would be particularly suited when the unit forms a cook hot plate. It the unit were to be used in an iron, the path might be more oval shaped.
  • FIG. 3 is a cross-sectional view of a press apparatus which may be used for forming the conductor 4 into the flat spiral shape shown on FIGS. 1 and 2.
  • the press apparatus comprises a base 6, a die mold 5, which is resiliently supported on base 6 by springs l3,and a press 7 which may be moved down upon the die plate 5 to compress it against the force of the springs 13.
  • the die plate 5 will have grooves or channels 51 formed therein corresponding to the shape of the heating conductor to be formed, e.g., the spiral shape shown on FIG. 2.
  • the base plate 6 will contain corresponding projections 61 which fit into the grooves 51 and are capable of moving therein.
  • a conventional helical heating conductor 8 is stretched and placed within the grooves 51, whereupon the press 7 is lowered compressing and flattening the conductor against the projections 61.
  • the heating coil of resistance wire in helical form is chosen with a coil diameter and pitch for the turns such that the coils will not flip over when pressed flat by the plate 7. Good results may be obtained where the pitch and the coil diameter are each five times the wire diameter.
  • the coils of wire 8 are placed in the die 5, and the press 7 brought down flattening the coils into the shape shown on FIGS. 1 and 2.
  • an adhesive foil backing which for the shape shown on FIG. 2 would be circular and large enough to cover all of the coils 4 shown on FIG. 2, may be placed on top of the die 5 and the base plate 6 brought up to push the flattened conductor against the adhesive foil causing the conductor to stick thereto.
  • the plate 1 is prepared by sand blasting or another means of roughening and then neutralized against acid by a method such as oxidizing or phosphatizing.
  • the embedding compound will normally consist mainly of magnesium oxide and a phosphoric acid binder.
  • a particularly good mixture is 2 parts of MgO and one part of SiO- and a solution of 1 part of Al [H P 41 and three parts of water f'l li coriipouiid is appiiai'rd the inside of the plate 1 with a thickness of about 1.5 millimeters.
  • the heating conductor which is now stuck to the adhesive backing, may be placed on top of the compound and pressed into it so that it is flush with the edge of the layer 2 as shown on FIG. 1.
  • the unit may then be heated to between 40 and 80C to cause the compound to completely solidify, after which the adhesive backing will be stripped off.
  • the protective layer 3 of the embedding compound may then be applied and the finished unit fired at 600 C to accomplish final drying and setting.
  • the layer 3 provides electrical and heat insulation to the conductors 4.
  • the layer of embedding compound 3 can be composed of a mixture of 90 parts by weight of quartz sand and 10 parts by weight of talc mixed with a phosphoric-acid binder such as that described above. There can also be added to this mixture 10 to 30 parts by weight of magnesium oxide in order to make the setting of the compound occur more quickly at room temperature.
  • the layer 2 after the heating conductors are inserted therein, can have applied to it either by spraying, brushing or otherwise a protective sealing layer comprising a mixture of talc and alkali silicate or talc and colloidal silicon dioxide.
  • a protective sealing layer comprising a mixture of talc and alkali silicate or talc and colloidal silicon dioxide.
  • Such a layer need only be 0.05 millimeters thick. This will form a protective coating which will prevent moisture from entering into the heating unit even at operating temperatures of 800C.
  • the sealing layer has extremely good mechanical stability at the high operating temperatures of the unit and will not affect the conducting properties of the embedding compound. Good results are obtained with a mixture of 1 part by weight oftalc and 10 parts by weight of silicon dioxide. Even if the layer 3 is used, it is preferable to coat it with the above described protective layer to obtain the moisture proofing described above.
  • Test results have shown that this method will result in excellent adhesion of the embedding compounds to the plate 1 where the embedding compound layers are l to 4 millimeters thick. Tests have indicated good results using base plates made of ceramic glass materials, sheet steel, cast iron, stainless steel or enamelled materials. With each of the materials, good adhesion was maintained throughout all temperature cycling tests.
  • the layer of embedding material can be made thick enough to maintain a spacing which will avoid any breakdown problems.
  • Another solution is to apply the embedding compound to a very thin axillary plate, e.g., a few tenths of a millimeter thick, made of an electrical insulating, heat resistant material, for example, mica.
  • the embedding compound need only be applied to the axillary plate with a thickness which corresponds to the diameter of the wire, thus making it a very thin layer.
  • a method for manufacturing a heating conductor for use in a heating unit of the type wherein the conductor lies parallel to the heating surface immersed in an embedding compound applied to the other side of the plate which forms the heating surface comprising:

Landscapes

  • Surface Heating Bodies (AREA)
  • Resistance Heating (AREA)
US00332622A 1972-02-17 1973-02-15 Method of making electric heating unit Expired - Lifetime US3798759A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19722207343 DE2207343B1 (de) 1972-02-17 1972-02-17 Elektrische heizplatte

Publications (1)

Publication Number Publication Date
US3798759A true US3798759A (en) 1974-03-26

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US00332622A Expired - Lifetime US3798759A (en) 1972-02-17 1973-02-15 Method of making electric heating unit

Country Status (6)

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US (1) US3798759A (en))
JP (1) JPS4890034A (en))
DE (1) DE2207343B1 (en))
FR (1) FR2172247A1 (en))
IT (1) IT979048B (en))
NL (1) NL7302275A (en))

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3881824A (en) * 1972-03-17 1975-05-06 Canada Minister Defence Alignment and control system
US4308080A (en) * 1979-02-07 1981-12-29 Micropore International Limited Method of shaping coils
US4665637A (en) * 1985-07-26 1987-05-19 Braun Aktiengesellschaft Sole plate coating for a fabric pressing device
US4702933A (en) * 1985-07-26 1987-10-27 Braun Aktiengesellschaft Fabric pressing device
US5026970A (en) * 1988-07-29 1991-06-25 Emaco Ltd. Cooking appliances
FR2745147A1 (fr) * 1996-02-19 1997-08-22 Eco Tan Ltd Element chauffant a resistance electrique
WO2010151839A1 (en) * 2009-06-26 2010-12-29 Evo, Inc. Electric cooking apparatus
USD636630S1 (en) 2010-06-25 2011-04-26 Evo, Inc. Electric cooking apparatus

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2551137C2 (de) * 1975-11-14 1986-04-24 E.G.O. Elektro-Geräte Blanc u. Fischer, 7519 Oberderdingen Elektrischer Strahlungsheizkörper für Glaskeramikkochplatten
JPS5734991U (en)) * 1980-08-07 1982-02-24
JPH028399Y2 (en)) * 1980-08-12 1990-02-28
DE19711541A1 (de) * 1997-03-20 1998-09-24 Ako Werke Gmbh & Co Elektrokochplatte
WO2000013466A1 (fr) * 1998-08-31 2000-03-09 Daikin Industries, Ltd. Dispositif de chauffage

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2249476A (en) * 1938-09-26 1941-07-15 John A Knight Electric hot plate
US3680207A (en) * 1971-01-28 1972-08-01 Corning Glass Works Method of making electrical heating units

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2249476A (en) * 1938-09-26 1941-07-15 John A Knight Electric hot plate
US3680207A (en) * 1971-01-28 1972-08-01 Corning Glass Works Method of making electrical heating units

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3881824A (en) * 1972-03-17 1975-05-06 Canada Minister Defence Alignment and control system
US4308080A (en) * 1979-02-07 1981-12-29 Micropore International Limited Method of shaping coils
US4665637A (en) * 1985-07-26 1987-05-19 Braun Aktiengesellschaft Sole plate coating for a fabric pressing device
US4702933A (en) * 1985-07-26 1987-10-27 Braun Aktiengesellschaft Fabric pressing device
US5026970A (en) * 1988-07-29 1991-06-25 Emaco Ltd. Cooking appliances
FR2745147A1 (fr) * 1996-02-19 1997-08-22 Eco Tan Ltd Element chauffant a resistance electrique
WO2010151839A1 (en) * 2009-06-26 2010-12-29 Evo, Inc. Electric cooking apparatus
US20100326980A1 (en) * 2009-06-26 2010-12-30 Evo, Inc. Electric cooking apparatus
US8530795B2 (en) 2009-06-26 2013-09-10 Evo, Inc. Electric cooking apparatus
US9220368B2 (en) 2009-06-26 2015-12-29 Evo, Inc. Electric cooking apparatus
USD636630S1 (en) 2010-06-25 2011-04-26 Evo, Inc. Electric cooking apparatus

Also Published As

Publication number Publication date
IT979048B (it) 1974-09-30
DE2207343B1 (de) 1973-08-09
NL7302275A (en)) 1973-08-21
FR2172247A1 (en)) 1973-09-28
JPS4890034A (en)) 1973-11-24
DE2207343A1 (en)) 1973-08-09

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