Classifications

• • 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 [2D] plane, e.g. plate-heater
  • H05B3/22—Heating elements having extended surface area substantially in a two-dimensional [2D] plane, e.g. plate-heater non-flexible
  • H05B3/26—Heating elements having extended surface area substantially in a two-dimensional [2D] plane, e.g. plate-heater non-flexible heating conductor mounted on insulating base
  • H05B3/262—Heating elements having extended surface area substantially in a two-dimensional [2D] plane, e.g. plate-heater non-flexible heating conductor mounted on insulating base the insulating base being an insulated metal plate

Definitions

• the present invention relates to high-temperature heating systems consisting of a composite system made of enamelled metal substrate, an electrically insulating base glass layer applied thereon, metallic heating conductors and chemically resistant cover glass layer and a mediator layer between enamelled metal substrate and insulating glass layer, a process for producing these heating systems and their use.
• Low-temperature heating systems based on enamelled sheet steel have been known for a long time.
• electrical resistances in the form of heating lacquers, metal-containing pastes or metallic conductor tracks are applied directly to the enamelling.
• This conventional enamelling which acts as an electrical insulator, has the disadvantage that its electrical volume resistance decreases as the temperature rises, so that the use of such heating systems is limited to a low temperature range ( ⁇ 150 ° C.).
• DE-A 3 536 268 describes a heating element for high operating temperatures (> 150 ° C.).
• This is a composite system consisting of sheet steel, on which there is an electrically insulating base glass layer, metallic conductor tracks and, as a conclusion, a chemically resistant one Cover glass layer are.
• This heating element can be loaded up to 400 ° C without changing the resistance of the insulating glass layer.
• This electrically insulating glass layer used here consists of an alkali-free calcium aluminum borosilicate (see also DE-A 3 446 554).
• the disadvantage of these heating elements is that the steel sheet must be decarburized, degreased, pickled and nickel-plated so that the insulating glass layer adheres well to the steel sheet.
• the heating elements further described in this document in which a steel sheet coated with a base enamel was used instead of a treated steel sheet, have the disadvantage that after a short time and repeated heating and cooling of the element, the volume resistance of the insulating glass layer also decreases here and thus the Functionality is severely impaired or even disturbed.
• the task was therefore to provide heating elements in which on the one hand the steel sheet does not have to be pretreated and on the other hand the insulating glass layer on which the conductor tracks are located maintains its volume resistance.
• the present invention relates to a high-temperature heating system consisting of an enamelled metal substrate, preferably sheet steel, on which there is a multilayer system which consists of an inner layer of insulating glass, metallic conductor tracks and an outer layer of a cover glass, which is characterized in that the layer system a mediator layer is connected to the enamelled metal substrate.
• the mediator layer consists of a mixture of a zirconium phosphate glass and a boron-titanium frit, this mixture preferably consisting of 35-55% by weight of zirconium phosphate glass and 65-45% by weight of boron-titanium frit.
• the insulating glass layer is an alkali-free calcium-alumo-borosilicate glass.
• the outer cover glass layer consists of a mixture of a boron-titanium frit and a zirconium phosphate glass.
• the above zirconium phosphate glasses can have the following composition: ZrO2 26-30 % By weight P2O5 21-25 % By weight SiO2 7-12 % By weight Na2O 6-10 % By weight K2O 8-12 % By weight TiO2 6-10 % By weight BaO 8-12 % By weight F 3-8 % By weight
• the above-mentioned boron-titanium frits are known and customary types of fries (see, for example, AI Andrews, Porcelain Enamels, p. 277).
• the above insulating glasses can have the following composition: B2O3 43-48 % By weight CaO 29-34 % By weight SiO2 8-15 % By weight Al2O3 7-10 % By weight MgO 1- 2 % By weight
• the high-temperature heating systems according to the invention are produced by multi-screen printing processes in that the various layers are applied successively to the enamelled metal substrate and then baked together at 780 to 850 ° C., preferably at 780 to 820 ° C., in one operation.
• the layers are applied in the form of pastes, the pastes being mixed by intimate mixing of the mediator frit as a fine powder (grain size range from 1 to 25 ⁇ m), the insulating glass or the cover glass with a thermoplastic medium, an oil medium or with a medium of a water-soluble organic suspension,
• the mixing ratio of powder to medium is preferably approximately 4: 1.
• the pastes are applied either at room temperature or at elevated temperature (especially when using thermoplastics) with the screen printing mesh.
• Pine oil (80-90% by weight) with 3-15% by weight of rosin or derivatives thereof, 1-4% by weight of cellulose derivatives and 2-5% by weight of acrylic acid ester is preferably used as the oil medium, while the organic suspension preferably contains a mixture of 5-10% by weight of cellulose derivatives, 20-30% by weight of ethyl alcohol and 60% by weight of glycol derivatives.
• Steryl alcohol 70-80% by weight with 5-15% by weight glycol ester, 5-15% by weight acrylic acid ester and 5-10% by weight rosin is preferably used as the thermoplastic medium.
• the heating conductor is also applied in the form of a paste consisting of the above.
• Media and very finely divided metal particles preferably silver, ruthenium, a blend of the two metals, nickel or copper.
• the layer thickness of the screen printing layers is regulated via the mesh size and the thread thickness of the screen printing network.
• Sieves with 62 to 84 meshes / cm are preferred for the application of the heating circuit boards and sieves with 34 to 42 meshes / cm for the application of the other pastes.
• the heating conductor layer has a thickness of approximately 15-20 ⁇ m, while the remaining layers have thicknesses of the order of 50 ⁇ m,
• the high-temperature heating systems are preferably used as inserts in ovens, in washing machines, in hot water tanks and in toasters.
• a metal substrate preferably a steel sheet, which is provided as a high-temperature heating element, is coated with a known enamel frit by conventional methods (wet method or electrostatic) and fired.
• This enamelled metal substrate is then coated with e.g. 4 different pastes made of thermoplastic medium coated in the form of 5 screen printing jobs to be finally fired at 780-850 ° C,
• thermoplastic media such as a thermoplastic based on sterol and a plasticizer
• the intermediate drying after each screen printing job is omitted (see e.g. oil medium).
• the mediator frit which consists of a mixture of 35-55% by weight of a zirconium phosphate glass and 65-45% by weight of a commercially available boron-titanium frit, is used as a fine powder (grain size range from 1 to 25 ⁇ m) with the thermoplastic and the plasticizer is intimately mixed in a closed container at approx. 75 ° C for about an hour using a stirrer and homogenized using a three-roll mill, the cylinders of which are also preheated to approx. 60 ° C.
• the mixing ratio of the powder to the medium is 4: 1.
• the homogenized product is printed on the enamelled metal substrate in liquid form via the (directly or indirectly) heated screen printing network,
• the sieve has 34 to 42 stitches / cm.
• the pastes with the insulating glass or cover glass are produced and applied in the same way.
• the heating conductor paste consists of finely divided metal particles in the thermoplastic medium. Sieves with 62 to 84 stitches / cm are used for the application.
• thermoplastic medium is evaporated at 780-850 ° C in a drying or heating tunnel at approx. 100-150 ° C before the actual fire.
• Finely divided silver in a thermoplastic medium 70-80% by weight steryl alcohol, 5-15% by weight glycol ester, 5- 15% by weight of acrylic acid ester and 5-10% by weight of rosin).
• each screen print is 50 ⁇ m, while the heating conductor layer moves at a thickness of 15-20 ⁇ m.
• Screen printing is carried out using commercial machines available on the market.
• the same application system can also be used for geometrically complex metal substrate shapes, namely by means of the so-called "pad printing" using special media.
• the fire takes place at 800-820 ° C in one operation.

Landscapes

• Resistance Heating (AREA)
• Glass Compositions (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)
• Surface Heating Bodies (AREA)
• General Induction Heating (AREA)
• Laminated Bodies (AREA)
• Pipe Accessories (AREA)
• Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
• Mounting, Exchange, And Manufacturing Of Dies (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (3)

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Family Applications (1)

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Cited By (2)

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• 1988
  • 1988-04-15 IT IT20218/88A patent/IT1218221B/it active
• 1989
  • 1989-03-31 NO NO89891370A patent/NO891370L/no unknown
  • 1989-04-03 AT AT89105794T patent/ATE67369T1/de not_active IP Right Cessation
  • 1989-04-03 DE DE8989105794T patent/DE58900273D1/de not_active Expired - Lifetime
  • 1989-04-03 ES ES89105794T patent/ES2025348B3/es not_active Expired - Lifetime
  • 1989-04-03 US US07/332,166 patent/US4970375A/en not_active Expired - Fee Related
  • 1989-04-03 DE DE8909020U patent/DE8909020U1/de not_active Expired - Lifetime
  • 1989-04-03 EP EP89105794A patent/EP0337230B1/fr not_active Expired - Lifetime
  • 1989-04-11 JP JP1089898A patent/JPH0212788A/ja active Pending
  • 1989-04-13 CA CA000596558A patent/CA1298603C/fr not_active Expired - Lifetime
  • 1989-04-14 DK DK181489A patent/DK181489A/da unknown

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