WO1995031084A1 - Heating element for a sheet electrical insulator - Google Patents

Heating element for a sheet electrical insulator Download PDF

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Publication number
WO1995031084A1
WO1995031084A1 PCT/EP1995/001695 EP9501695W WO9531084A1 WO 1995031084 A1 WO1995031084 A1 WO 1995031084A1 EP 9501695 W EP9501695 W EP 9501695W WO 9531084 A1 WO9531084 A1 WO 9531084A1
Authority
WO
WIPO (PCT)
Prior art keywords
heating element
insulator
graphite
element according
mirror
Prior art date
Application number
PCT/EP1995/001695
Other languages
German (de)
French (fr)
Inventor
Dusko Maravic
Original Assignee
Negawatt Gmbh
Maravic, Monika
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Negawatt Gmbh, Maravic, Monika filed Critical Negawatt Gmbh
Priority to AU26124/95A priority Critical patent/AU2612495A/en
Publication of WO1995031084A1 publication Critical patent/WO1995031084A1/en

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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
    • H05B3/10—Heater elements characterised by the composition or nature of the materials or by the arrangement of the conductor
    • H05B3/12—Heater elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
    • H05B3/14—Heater elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic
    • H05B3/145—Carbon only, e.g. carbon black, graphite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R1/00—Optical viewing arrangements; Real-time viewing arrangements for drivers or passengers using optical image capturing systems, e.g. cameras or video systems specially adapted for use in or on vehicles
    • B60R1/02—Rear-view mirror arrangements
    • B60R1/06—Rear-view mirror arrangements mounted on vehicle exterior
    • B60R1/0602—Rear-view mirror arrangements mounted on vehicle exterior comprising means for cleaning or deicing
    • 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
    • H05B3/84—Heating arrangements specially adapted for transparent or reflecting areas, e.g. for demisting or de-icing windows, mirrors or vehicle windshields
    • H05B3/845—Heating arrangements specially adapted for transparent or reflecting areas, e.g. for demisting or de-icing windows, mirrors or vehicle windshields specially adapted for reflecting surfaces, e.g. bathroom - or rearview mirrors

Definitions

  • the present invention relates to an electrical heating element for a flat, solid electrical insulator, the heating element being arranged on at least part of the insulator.
  • Electric heating elements are used in combination with a wide variety of flat bodies.
  • the exterior rear-view mirrors of vehicles are provided with heaters so that the mirrors always ensure a clear view.
  • the mirror heaters used so far have the following structure.
  • a first layer of plastic is applied to the back of the mirror, which has an electrically insulating effect.
  • a second layer, the heating layer is applied thereon. This layer is not a closed surface, but is formed by meandering electrical heating wires.
  • a third layer, again made of electrically insulating plastic, is finally applied as a cover.
  • the first layer is necessary so that the mirror does not fall apart if it breaks. On the other hand, it serves to protect the electrical conductor in the event of mirror breakage.
  • An electrical voltage is applied to the heating element, and the heat generated by the resistor is transferred to the mirror by means of heat conduction. Since a relatively thick electrical insulation layer, typically a few millimeters, is arranged between the mirror and the heater, the heat conduction is inhibited. In addition, this multilayer structure is complicated and the production of such heated mirrors is time-consuming.
  • the heating layers used can also only be used for low power ranges, since they melt under higher loads. If a body has to be heated to a higher temperature, resistance heating windings are therefore used. These are no longer arranged directly on the body but at a distance from it. In higher temperature ranges, heating is no longer carried out via heat conduction but via heat radiation with the physical disadvantages known from it, such as lower efficiency.
  • heating element according to the preamble of claim 1, which is characterized in that the heating element consists of flexible graphite.
  • the starting material for the production of graphite in flexible form is natural graphite. This is processed into a graphite intercalation compound. In further steps, this intermediate product is rolled into foils, drawn in cords or processed into tapes and fabrics.
  • This flexible materials have a relatively high specific resistance for electrical conductors.
  • a typical value for graphite foils is 1 " 10 " ⁇ m. Thanks to its physical properties, flexible or pliable graphite is also suitable as a heating resistor.
  • graphite is used as a heating element, it can be applied directly to the mirror surface in the case of mirror heating by pressing it onto the mirror surface by means of an outer insulation layer adhering to the edges of the mirror surface. No further insulation layer is required between the mirror and the heater.
  • the graphite heating element is considerably less susceptible to injury than the known heating layers. Therefore, it does not need to be specially protected in the event of a broken mirror. If a part of the film is nevertheless destroyed, the probability that the power line is completely interrupted is minimal, since it is wider than the wires of the known heating elements. There is therefore no noticeable loss in efficiency.
  • the heating element consists of a fabric or tape, its mechanical strength is significantly higher than that of the known heating elements. Therefore, damage to the heating element must be excluded, except in the case of extreme loads.
  • the graphite heating element covers the mirror more extensively than the known, thin heating wires. In the event of a broken mirror, the fragments are held together by the graphite heating element.
  • the heated mirror also has a simpler structure and is therefore quicker and cheaper to manufacture.
  • Figure 1 is a mirror heater for a vehicle exterior mirror in view
  • Figure 2 shows a tube heat exchanger in view.
  • the first embodiment is shown in Figure 1. It is a heated outside mirror of a vehicle.
  • the outside mirror consists of a solid glass plate 2, which has a mirror.
  • the lower surface in the drawing is the mirror surface 21 visible in the assembled state.
  • the upper surface in the drawing thus forms the rear side 20 of the exterior mirror in the assembled state.
  • a heating element 1 made of flexible graphite is arranged on this rear side 20.
  • this is an elongated film that runs in a meandering manner over at least one area of the surface.
  • other types of laying of the foils are possible, for example in the form of one or more spaced strips.
  • the graphite foil is attached to the electrical insulator, the glass plate, by means of an adhesive which is not visible here.
  • This adhesive has a suitable coefficient of thermal expansion, so that when the temperature changes, no stresses can arise that could produce cracks in the film.
  • Such adhesives somd Adhesln ® J1620 or Sichello ® J8510.
  • the thickness of the adhesive is only a few micrometers.
  • Electrical connections 10 are attached to the ends of the graphite foil by means of press contacts or by soldering. These connections pass into power supply lines 11, which can be connected to a power source, not shown here.
  • a graphite foil with a thickness of 0.2 mm is preferably used for heating an exterior mirror of a passenger vehicle.
  • Their specific resistance is 5-15 ⁇ m.
  • the current-carrying cross section and the unwound length of the film strip is also variable and depends on the effect that is to be achieved. In this example, a power of 15 watts is generally sufficient to heat the exterior mirror efficiently.
  • the applied voltage is 12 volts. This means that the film strip should have a width of approximately 3 mm and a developed length of 1 m.
  • the film thickness, the width or the length of the film strip is adjusted.
  • graphite foils with a thickness of 1/10 mm to 1 mm can be used.
  • the heating resistor made of graphite foil is completely covered with an additional electrically insulating foil. This protects the graphite foil on the one hand from environmental influences, and on the other hand it is completely electrically insulated from the environment. On the other side of the heating element, the glass plate forms the electrical insulator.
  • the heating resistor is applied directly on the mirror by the insulating film described above is fixed thereto. The film is larger than the heating resistor, so that it overlaps at the edges. These edges are now glued to the mirror, the film being pulled tight, so that the heating resistor is pressed through the film onto the mirror surface.
  • the structures described above can also be realized with other mirrors or glass plates, not shown here. Another application is heating bathroom mirrors to prevent them from fogging up. If a voltage of 220 volts is used, only the valid electrotechnical standards and regulations have to be observed. If the massive insulator forming the support is to be heated in sections, each section can be heated separately and with different outputs by laying several heating elements with separate power supplies.
  • heating element between two insulators to be heated.
  • the second insulator then corresponds to the insulating film described above.
  • Other heating elements and insulators can be sandwiched on top of each other.
  • FIG. 2 shows a second exemplary embodiment of the subject of the invention: a tubular heat exchanger. That kind can be used, for example, in household appliances such as dishwashers and washing machines.
  • the massive, In this example, the flat electrical insulator is a hollow cylinder 3.
  • the hollow cylinder 3 is at least partially wrapped by a heating element 1 '.
  • This heating element 1 ' consists of graphite in flexible form, in particular of a graphite foil, a graphite fabric or a graphite tape. As with the mirror heater, there are electrical connections and a power line.
  • the heating element 1 ' is in direct contact with the hollow cylinder 3. It must therefore be made of a suitable material. On the one hand, it must be an electrical insulator, on the other hand, its coefficient of thermal expansion must be matched to that of the heating element in order to avoid thermoindicated stresses.
  • the hollow cylinder 3 is therefore preferably made of a ceramic based on aluminum oxide Al 2 0 3 , silicon dioxide Si0 2 or magnesium oxide MgO. Well-known ceramics are cordierite and steatite.
  • the tube is now heated by means of heat conduction and not by means of heat radiation, so that the efficiency is markedly greater.

Abstract

The proposed electrical heating element (1) is mounted on a solid sheet electrical insulator (2) to be heated. The electrical heating element (1) consists of graphite in flexible form, in particular a graphite film, fabric or web. This heating element is relatively insensitive to mechanical stress and is highly efficient. In one embodiment, the insulator is a metal-coated glass plate, which can be used to make an external heatable vehicle mirror.

Description

Heizelement für flächige elektrische Isolatoren Heating element for flat electrical insulators
Die vorliegende Erfindung betrifft ein elektrisches Heizelement für einen flächigen, massiven elektrischen Isolator, wobei das Heizelement mindestens auf einem Teil des Isolators angeordnet ist.The present invention relates to an electrical heating element for a flat, solid electrical insulator, the heating element being arranged on at least part of the insulator.
Elektrische Heizelemente werden in Kombination mit den verschiedensten flächigen Körpern eingesetzt. So werden beispielsweise die Aussenrückspiegel von Fahrzeugen mit Heizungen versehen, damit die Spiegel stets eine klare Sicht gewährleisten.Electric heating elements are used in combination with a wide variety of flat bodies. For example, the exterior rear-view mirrors of vehicles are provided with heaters so that the mirrors always ensure a clear view.
Die bisher verwendeten Spiegelheizungen haben den folgenden Aufbau. Auf der Rückseite des Spiegels wird eine erste Schicht aus Kunststoff aufgetragen, die elektrisch isolierend wirkt. Darauf wird eine zweite Schicht, die Heizschicht, aufgebracht. Diese Schicht ist nicht eine geschlossene Fläche, sondern wird durch mäanderförmig verlaufende elektrische Heizdrähte gebildet. Eine dritte Schicht, wiederum aus elektrisch isolierendem Kunststoff, wird zum Schluss als Abdeckung aufgetragen. Die erste Schicht ist notwendig, damit einerseits der Spiegel bei Bruch nicht auseinanderfällt. Andererseits dient sie als Schutz des elektrischen Leiters bei Spiegelbruch. An das Heizelement wird eine elektrische Spannung angelegt, und die über den Widerstand erzeugte Wärme wird mittels Wärmeleitung an den Spiegel abgegeben. Da zwischen Spiegel und Heizung eine relativ dicke elektrische Isolationschicht, typischerweise einige Millimeter, angeordnet ist, wird die Wärmeleitung gehemmt . Zudem ist dieser mehrschichtige Aufbau kompliziert und die Herstellung derartiger beheizter Spiegel zeitaufwendig.The mirror heaters used so far have the following structure. A first layer of plastic is applied to the back of the mirror, which has an electrically insulating effect. A second layer, the heating layer, is applied thereon. This layer is not a closed surface, but is formed by meandering electrical heating wires. A third layer, again made of electrically insulating plastic, is finally applied as a cover. The first layer is necessary so that the mirror does not fall apart if it breaks. On the other hand, it serves to protect the electrical conductor in the event of mirror breakage. An electrical voltage is applied to the heating element, and the heat generated by the resistor is transferred to the mirror by means of heat conduction. Since a relatively thick electrical insulation layer, typically a few millimeters, is arranged between the mirror and the heater, the heat conduction is inhibited. In addition, this multilayer structure is complicated and the production of such heated mirrors is time-consuming.
Die verwendeten Heizschichten lassen sich ausserdem nur für tiefe Leistungsbereiche einsetzen, da sie bei höheren Belastungen durchschmelzen. Muss ein Körper auf eine höhere Temperatur erwärmt werden, so werden deshalb Wider¬ standsheizwicklungen verwendet. Diese sind nicht mehr direkt auf dem Körper sondern beabstandet zu ihm angeordnet. In höheren Temperaturbereichen erfolgt die Erwärmung somit nicht mehr über Wärmeleitung sondern über Wärmestrahlung mit den damit bekannten physikalischen Nachteilen wie kleinerer Wirkungsgrad.The heating layers used can also only be used for low power ranges, since they melt under higher loads. If a body has to be heated to a higher temperature, resistance heating windings are therefore used. These are no longer arranged directly on the body but at a distance from it. In higher temperature ranges, heating is no longer carried out via heat conduction but via heat radiation with the physical disadvantages known from it, such as lower efficiency.
Es ist deshalb Aufgabe der Erfindung, ein Heizelement zu schaffen, das obengenannte Nachteile behebt.It is therefore an object of the invention to provide a heating element which overcomes the disadvantages mentioned above.
Diese Aufgabe löst ein Heizelement gemäss Oberbegriff des Patentanspruches 1, das dadurch gekennzeichnet ist, dass das Heizelement aus flexiblem Graphit besteht.This object is achieved by a heating element according to the preamble of claim 1, which is characterized in that the heating element consists of flexible graphite.
Ausgangsmaterial für die Herstellung von Graphit in flexibler Form ist Naturgraphit. Dieses wird zu einer Graphit- einlaσcrungsverbindung verarbeitet. In weiteren Verfa rens- schritten wird dieses Zwischenprodukt zu Folien gewalzt, in Schnüre gezogen oder zu Bändern und Geweben verarbeitet. Diese flexiblen Materialien weisen einen für elektrische Leiter relativ hohen spezifischen Widerstand auf. So beträgt ein typischer Wert für Graphit-Folien 1"10" Ωm. Dank seiner physikalischen Eigenschaften ist flexibles oder biegsames Graphit auch als Heizwiderstand geeignet.The starting material for the production of graphite in flexible form is natural graphite. This is processed into a graphite intercalation compound. In further steps, this intermediate product is rolled into foils, drawn in cords or processed into tapes and fabrics. This flexible materials have a relatively high specific resistance for electrical conductors. A typical value for graphite foils is 1 " 10 " Ωm. Thanks to its physical properties, flexible or pliable graphite is also suitable as a heating resistor.
Wird Graphit als Heizelement verwendet, so kann dieses im Falle der Spiegelheizung direkt auf die Spiegeloberfläche aufgebracht werden, indem es mittels eine an den Rändern an der Spiegeloberfläche haftende, äussere Isolationsschicht an die Spiegeloberfläche angepresst wird. Zwischen Spiegel und Heizung ist keine weitere Isolationsschicht mehr notwendig. Das Heizelement aus Graphit ist beträchtlich weniger verletzungsanfällig als die bekannten Heizschichten. Deshalb muss es im Falle von Spiegelbruch nicht speziell geschützt werden. Wird trotzdem ein Teil der Folie zerstört, so ist die Wahrscheinlichkeit minim, dass die Stromleitung vollständig unterbrochen ist, da sie breiter ist als die Drähte der bekannten Heizelemente. Es tritt somit kein merklicher Verlust des Wirkungsgrades auf . Falls das Heizelement aus einem Gewebe oder Band besteht, so ist ihre mechanische Beanspruchbarkeit wesentlich höher als die der bekannten Heizelemente. Deshalb ist ausser bei extremen Beanspruchungen eine Beschädigung des Heizelementes auszuschliessen.If graphite is used as a heating element, it can be applied directly to the mirror surface in the case of mirror heating by pressing it onto the mirror surface by means of an outer insulation layer adhering to the edges of the mirror surface. No further insulation layer is required between the mirror and the heater. The graphite heating element is considerably less susceptible to injury than the known heating layers. Therefore, it does not need to be specially protected in the event of a broken mirror. If a part of the film is nevertheless destroyed, the probability that the power line is completely interrupted is minimal, since it is wider than the wires of the known heating elements. There is therefore no noticeable loss in efficiency. If the heating element consists of a fabric or tape, its mechanical strength is significantly higher than that of the known heating elements. Therefore, damage to the heating element must be excluded, except in the case of extreme loads.
Zudem deckt das Heizelement aus Graphit den Spiegel flächiger ab als die bekannten, dünnen Heizdrähte. Dadurch werden im Falle von Spiegelbruch die Scherben durch das Heizelement aus Graphit zusammengehalten. Der beheizbare Spiegel weist auch einen einfacheren Aufbau auf und ist deshalb schneller und kostengünstiger herstellbar. In den beiliegenden Zeichnungen sind zwei Ausführungsbeispiele des Erfindungsgegenstandes dargestellt und in der nachfolgenden Beschreibung erläutert. Es zeigenIn addition, the graphite heating element covers the mirror more extensively than the known, thin heating wires. In the event of a broken mirror, the fragments are held together by the graphite heating element. The heated mirror also has a simpler structure and is therefore quicker and cheaper to manufacture. Two exemplary embodiments of the subject matter of the invention are illustrated in the accompanying drawings and are explained in the description below. Show it
Figur 1 eine Spiegelheizung für einen Fahrzeugaussenspiegel in Ansicht undFigure 1 is a mirror heater for a vehicle exterior mirror in view and
Figur 2 einen Rohrwärmetauscher in Ansicht.Figure 2 shows a tube heat exchanger in view.
Das erste Ausführungsbeispiel ist in Figur 1 dargestellt. Es ist ein beheizbarer Aussenspiegel eines Fahrzeuges. Der Aussen- spiegel besteht aus einer massiven Glasplatte 2, die eine Ver- spiegelung aufweist. Die auf der Zeichnung untere Oberfläche ist die im montierten Zustand sichtbare Spiegelfläche 21. Die in der Zeichnung obere Fläche bildet somit im montierten Zustand die Rückseite 20 des Aussenspiegels.The first embodiment is shown in Figure 1. It is a heated outside mirror of a vehicle. The outside mirror consists of a solid glass plate 2, which has a mirror. The lower surface in the drawing is the mirror surface 21 visible in the assembled state. The upper surface in the drawing thus forms the rear side 20 of the exterior mirror in the assembled state.
Auf dieser Rückseite 20 ist ein Heizelement 1 aus flexiblem Graphit angeordnet. In diesem Beispiel handelt es sich dabei um eine längliche Folie, die mäanderförmig über mindestens einen Bereich der Oberfläche verläuft. Andere Verlegungsarten der Folien sind jedoch möglich, beispielsweise in Form von einem oder mehreren beabstandeten Streifen. Die Graphitfolie ist mittels einem hier nicht sichtbaren Klebstoff auf dem elek¬ trischen Isolator, der Glasplatte, angebracht. Dieser Klebstoff weist einen geeigneten Wärmeausdehnungskoeffizienten auf, so dass bei der Tempreraturveränderung keine Spannungen entstehen können, die Sprϋnge in der Folie erzeugen könnten. Derartige Klebstoffe somd Adhesln® J1620 oder Sichello® J8510. Die Dicke des Klebstoffes beträgt lediglich einige Mikrometer. An den Enden der Graphitfolie sind elektrischen Anschlüsse 10 mittels Presskontakten oder durch Löten angebracht. Diese Anschlüsse gehen in Stromzuführungen 11 über, die mit einer hier nicht dargestellten Stromquelle verbindbar sind.A heating element 1 made of flexible graphite is arranged on this rear side 20. In this example, this is an elongated film that runs in a meandering manner over at least one area of the surface. However, other types of laying of the foils are possible, for example in the form of one or more spaced strips. The graphite foil is attached to the electrical insulator, the glass plate, by means of an adhesive which is not visible here. This adhesive has a suitable coefficient of thermal expansion, so that when the temperature changes, no stresses can arise that could produce cracks in the film. Such adhesives somd Adhesln ® J1620 or Sichello ® J8510. The thickness of the adhesive is only a few micrometers. Electrical connections 10 are attached to the ends of the graphite foil by means of press contacts or by soldering. These connections pass into power supply lines 11, which can be connected to a power source, not shown here.
Für die Beheizung eines Aussenspiegels eines Personenkraftfahr¬ zeuges wird bevorzugterweise eine Graphitfolie der Dicke 0.2 mm verwendet. Ihr spezifischer Widerstand beträgt 5-15 μΩm. Der stromdurchflossene Querschnitt und die abgewickelte Länge des Folienstreifens ist ebenfalls variabel und hängt von der Wirkung ab, die erzielt werden soll. In diesem Beispiel reicht im allgemeinen eine Leistung 15 Watt aus, um den Aussenspiegel effizient zu beheizen. Die angelegte Spannung beträgt 12 Volt. Damit ergibt sich, dass der Folienstreifen ungefähr 3 mm breit und eine abgewickelte Länge von 1 m aufweisen soll.A graphite foil with a thickness of 0.2 mm is preferably used for heating an exterior mirror of a passenger vehicle. Their specific resistance is 5-15 μΩm. The current-carrying cross section and the unwound length of the film strip is also variable and depends on the effect that is to be achieved. In this example, a power of 15 watts is generally sufficient to heat the exterior mirror efficiently. The applied voltage is 12 volts. This means that the film strip should have a width of approximately 3 mm and a developed length of 1 m.
Soll nun eine grössere Leistung erzielt werden oder differiert die angelegte Spannung von dem oben angegebenen Wert, so wird die Foliendicke, die Breite oder die Länge des Folienstreifens angepasst. Grundsätzlich lassen sich Graphitfolien mit einer Dicke von 1/10 mm bis 1 mm verwenden.If greater power is now to be achieved or if the applied voltage differs from the value given above, the film thickness, the width or the length of the film strip is adjusted. Basically, graphite foils with a thickness of 1/10 mm to 1 mm can be used.
In einer bevorzugten Ausführungsform ist der Heizwiderstand aus Graphitfolie mit einer zusätzlichen elektrisch isolierenden Folie vollständig zugedeckt. Dadurch wird die Graphitfolie einerseits vor Umwelteinflüssen geschützt, andererseits ist sie somit vollständig gegenüber der Umgebung elektrisch isoliert. Auf der anderen Seite des Heizelementes bildet nämlich die Glasplatte den elektrischen Isolator. In einer anderen Ausführungsform 'ist der Heizwiderstand direkt auf dem Spiegel aufgebracht, indem die oben beschriebene isolierende Folie diesen fixiert. Die Folie ist hierfür grösser als der Heizwiderstand, so dass sie ihn an den Rändern überlappt. Diese Ränder werden nun auf den Spiegel geklebt, wobei die Folie straffgezogen wird, so dass der Heizwiderstand durch die Folie an die Spiegeloberfläche angepresst wird.In a preferred embodiment, the heating resistor made of graphite foil is completely covered with an additional electrically insulating foil. This protects the graphite foil on the one hand from environmental influences, and on the other hand it is completely electrically insulated from the environment. On the other side of the heating element, the glass plate forms the electrical insulator. In another embodiment, 'the heating resistor is applied directly on the mirror by the insulating film described above is fixed thereto. The film is larger than the heating resistor, so that it overlaps at the edges. These edges are now glued to the mirror, the film being pulled tight, so that the heating resistor is pressed through the film onto the mirror surface.
Die oben beschriebenen Aufbauten lassen sich auch bei anderen, hier nicht dargestellten Spiegeln oder Glasplatten verwirklichen. Eine weitere Anwendungsmöglichkeit ist das Beheizen von Badezimmerspiegeln, um deren Beschlagen zu verhindern. Wird eine Spannung von 220 Volt verwendet, so sind lediglich die gültigen elektrotechnischen Normen und Vorschriften zu beachten. Ist der massive, den Träger bildender Isolator abschnittsweise zu beheizen, so kann jeder Abschnitt getrennt und mit unterschiedlicher Leistung geheizt werden, indem mehrere Heizelemente mit getrennten Stromzuführungen verlegt werden.The structures described above can also be realized with other mirrors or glass plates, not shown here. Another application is heating bathroom mirrors to prevent them from fogging up. If a voltage of 220 volts is used, only the valid electrotechnical standards and regulations have to be observed. If the massive insulator forming the support is to be heated in sections, each section can be heated separately and with different outputs by laying several heating elements with separate power supplies.
Zudem ist es möglich, das Heizelement zwischen zwei zu beheizenden Isolatoren anzuordnen. Der zweite Isolator entspricht dann der oben beschriebenen isolierenden Folie. Weitere Heizelemente und Isolatoren sind sandwichartig aufeinanderschichtbar.It is also possible to arrange the heating element between two insulators to be heated. The second insulator then corresponds to the insulating film described above. Other heating elements and insulators can be sandwiched on top of each other.
In Figur 2 ist ein zweites Ausführungsbeispiel des Erfindungs- gegenstandet- dargestellt: ein rohrförmiger Wärmetauscher. Deartige
Figure imgf000008_0001
sind beispielsweise in Haushaltgeräten wie Geschirrspüler und Waschmaschinen einsetzbar. Der massive, flächige elektrische Isolator ist in diesem Beispiel ein Hohlzylinder 3. Dieser wird von einem zu erwärmenden Medium, beispielsweise Wasser, durchflössen. Der Hohlzylinder 3 ist mindestens teilweise von einem Heizelement 1 ' umwickelt . Dieses Heizelement 1 ' besteht aus Graphit in flexibler Form, insbesondere aus einer Graphitfolie, einem Graphitgewebe oder einem Graphitband. Wie bei der Spiegelheizung sind auch hier elektrische Anschlüsse und eine Stromleitung vorhanden.FIG. 2 shows a second exemplary embodiment of the subject of the invention: a tubular heat exchanger. That kind
Figure imgf000008_0001
can be used, for example, in household appliances such as dishwashers and washing machines. The massive, In this example, the flat electrical insulator is a hollow cylinder 3. A medium to be heated, for example water, flows through it. The hollow cylinder 3 is at least partially wrapped by a heating element 1 '. This heating element 1 'consists of graphite in flexible form, in particular of a graphite foil, a graphite fabric or a graphite tape. As with the mirror heater, there are electrical connections and a power line.
Das Heizelement 1' steht in direkter Berührung mit dem Hohl¬ zylinder 3. Deshalb muss dieser aus einem geeigneten Material gefertigt sein. Er muss einerseits ein elektrischer Isolator sein, andererseits muss sein Wärmeausdehnungskoeffizient dem¬ jenigen des Heizelementes angepasst sein, um thermoindizierte Spannungen zu vermeiden. Der Hohlzylinder 3 besteht deshalb bevorzugterweise aus einer Keramik auf der Basis von Aluminiumoxid Al203, Siliziumdioxid Si02 oder Magnesiumoxid MgO. Bekannte Keramiken sind Cordierit und Steatit .The heating element 1 'is in direct contact with the hollow cylinder 3. It must therefore be made of a suitable material. On the one hand, it must be an electrical insulator, on the other hand, its coefficient of thermal expansion must be matched to that of the heating element in order to avoid thermoindicated stresses. The hollow cylinder 3 is therefore preferably made of a ceramic based on aluminum oxide Al 2 0 3 , silicon dioxide Si0 2 or magnesium oxide MgO. Well-known ceramics are cordierite and steatite.
Im Gegensatz zu den bekannten Wärmetauschern erfolgt nun die Beheizung des Rohres mittels Wärmeleitung und nicht mittels Wärmestrahlung, so dass der Wirkungsgrad merklich grδsser ist. In contrast to the known heat exchangers, the tube is now heated by means of heat conduction and not by means of heat radiation, so that the efficiency is markedly greater.

Claims

Patentansprüche Claims
1. Elektrisches Heizelement (1,1') für einen flächigen, massiven elektrischen Isolator (2,3) , wobei das Heizelement1. Electrical heating element (1,1 ') for a flat, solid electrical insulator (2,3), the heating element
(1,1') mindestens auf einem Teil des Isolators (2,3) angeordnet ist, dadurch gekennzeichnet, dass das Heizelement (1,1') aus flexiblem Graphit besteht.(1,1 ') is arranged at least on part of the insulator (2,3), characterized in that the heating element (1,1') consists of flexible graphite.
2. Heizelement nach Anspruch 1, dadurch gekennzeichnet, dass das Heizelement (1,1') aus Graphitfolie besteht.2. Heating element according to claim 1, characterized in that the heating element (1,1 ') consists of graphite foil.
3. Heizelement nach Anspruch 2, dadurch gekennzeichnet, dass die Folie in Streifen mäanderförmig auf dem Isolator (2,3) angeordnet ist.3. Heating element according to claim 2, characterized in that the film is arranged in strips meandering on the insulator (2,3).
4. Heizelement nach Anspruch 1, dadurch gekennzeichnet, dass es mittels einem einen geeigneten Wärmeausdehnungskoeffizienten aufweisenden Klebstoff auf dem Isolator (2,3) angeordnet ist.4. Heating element according to claim 1, characterized in that it is arranged on the insulator (2, 3) by means of an adhesive having a suitable coefficient of thermal expansion.
5. Heizelement nach Anspruch 1, dadurch gekennzeichnet, dass der Isolator (2,3) ein Glas ist.5. Heating element according to claim 1, characterized in that the insulator (2,3) is a glass.
6. Heizelement nach Anspruch 1, dadurch gekennzeichnet, dass es auf der vom Isolator (2,3) abgewandten Seite durch eine elektrisch isolierende Schicht oder einem Isolator abgedeckt ist.6. Heating element according to claim 1, characterized in that it is covered on the side facing away from the insulator (2, 3) by an electrically insulating layer or an insulator.
7. Heizelement nach Anspruch 6, dadurch gekennzeichnet, dass es mittels der abdeckenden isolierenden Schicht oder dem Isolator am Isolator fixiert ist. 7. Heating element according to claim 6, characterized in that it is fixed to the insulator by means of the covering insulating layer or the insulator.
8. Heizelement nach einem der Ansprüche 1 oder 5, dadurch gekennzeichnet, dass es eine Spiegelheizung, insbesondere für Fahrzeugaussenεpiegel, ist.8. Heating element according to one of claims 1 or 5, characterized in that it is a mirror heater, in particular for Fahrzeugaussenεpiegel.
9. Heizelement nach Anspruch 1, dadurch gekennzeichnet, dass der Isolator ein Hohlzylinder (3) ist, der mindestens teilweise vom Heizelement (1') umwickelt ist und der von einem zu erwärmenden Medium durchflössen ist.9. Heating element according to claim 1, characterized in that the insulator is a hollow cylinder (3) which is at least partially wrapped by the heating element (1 ') and which is flowed through by a medium to be heated.
10. Heizelement nach Anspruch 9, dadurch gekennzeichnet, dass der Isolator (3) aus Keramik, insbesondere Cordierit ® oder Steatit ®, besteht.10. Heating element according to claim 9, characterized in that the insulator (3) consists of ceramic, in particular Cordierit ® or Steatit ®.
11. Heizelement nach Anspruch 9, dadurch gekennzeichnet, dass das Heizelement (1') aus Graphitfolie, aus Graphitgewebe oder aus Graphitbändern besteh . 11. Heating element according to claim 9, characterized in that the heating element (1 ') consists of graphite foil, graphite fabric or graphite strips.
PCT/EP1995/001695 1994-05-10 1995-05-04 Heating element for a sheet electrical insulator WO1995031084A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU26124/95A AU2612495A (en) 1994-05-10 1995-05-04 Heating element for a sheet electrical insulator

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH1451/94-7 1994-05-10
CH145194 1994-05-10

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WO1995031084A1 true WO1995031084A1 (en) 1995-11-16

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000038950A3 (en) * 1998-12-29 2001-09-27 Magna Reflex Holding Gmbh Vehicle rearview system with electrochrome mirror
WO2006037596A1 (en) * 2004-10-05 2006-04-13 Margarete Kerschbaum Heating device
WO2006110730A2 (en) * 2005-04-12 2006-10-19 Hyperion Innovations, Inc. Portable heated seating

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1765768A1 (en) * 1968-07-16 1971-08-26 Tuerk & Hillinger Kg Electric flat radiator
DE2710588A1 (en) * 1977-03-11 1978-09-14 Licentia Gmbh Heated exterior driving mirror - has resistive heating backing layer keeping surface clear
FR2446202A3 (en) * 1979-01-15 1980-08-08 Vorwerk & Sohn HEATABLE EXTERIOR MIRROR FOR MOTOR VEHICLES
DE2908623A1 (en) * 1979-03-06 1980-09-11 Licentia Gmbh Heated car rear mirror - with central and peripheral electrodes for resistance layer to provide uniform current density
JPS58173156A (en) * 1982-04-05 1983-10-12 Daicel Chem Ind Ltd Polyamide composition
EP0127226A2 (en) * 1983-05-31 1984-12-05 Société Anonyme Compagnie Générale Belge des Isolants (COGEBI) Method of manufacturing electrical resistances and heating apparatuses

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1765768A1 (en) * 1968-07-16 1971-08-26 Tuerk & Hillinger Kg Electric flat radiator
DE2710588A1 (en) * 1977-03-11 1978-09-14 Licentia Gmbh Heated exterior driving mirror - has resistive heating backing layer keeping surface clear
FR2446202A3 (en) * 1979-01-15 1980-08-08 Vorwerk & Sohn HEATABLE EXTERIOR MIRROR FOR MOTOR VEHICLES
DE2908623A1 (en) * 1979-03-06 1980-09-11 Licentia Gmbh Heated car rear mirror - with central and peripheral electrodes for resistance layer to provide uniform current density
JPS58173156A (en) * 1982-04-05 1983-10-12 Daicel Chem Ind Ltd Polyamide composition
EP0127226A2 (en) * 1983-05-31 1984-12-05 Société Anonyme Compagnie Générale Belge des Isolants (COGEBI) Method of manufacturing electrical resistances and heating apparatuses

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 008, no. 003 (C - 203) 7 January 1984 (1984-01-07) *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000038950A3 (en) * 1998-12-29 2001-09-27 Magna Reflex Holding Gmbh Vehicle rearview system with electrochrome mirror
WO2006037596A1 (en) * 2004-10-05 2006-04-13 Margarete Kerschbaum Heating device
WO2006110730A2 (en) * 2005-04-12 2006-10-19 Hyperion Innovations, Inc. Portable heated seating
WO2006110730A3 (en) * 2005-04-12 2009-05-07 Hyperion Innovations Inc Portable heated seating

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