EP0105175B2 - Vacuum-formed electrical heating unit and method of making it - Google Patents

Vacuum-formed electrical heating unit and method of making it Download PDF

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Publication number
EP0105175B2
EP0105175B2 EP83108349A EP83108349A EP0105175B2 EP 0105175 B2 EP0105175 B2 EP 0105175B2 EP 83108349 A EP83108349 A EP 83108349A EP 83108349 A EP83108349 A EP 83108349A EP 0105175 B2 EP0105175 B2 EP 0105175B2
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EP
European Patent Office
Prior art keywords
heating coil
heating
ceramic
sieve
vacuum
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EP83108349A
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German (de)
French (fr)
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EP0105175A1 (en
EP0105175B1 (en
Inventor
Josef Bös
Leo Saris
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Kanthal GmbH
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Kanthal GmbH
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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
    • H05B3/283—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor embedded in insulating material the insulating material being an inorganic material, e.g. ceramic
    • 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
    • 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
    • H05B3/62—Heating elements specially adapted for furnaces
    • 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
    • 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
    • Y10T29/49087—Resistor making with envelope or housing

Definitions

  • the invention relates to an electrical, free-radiating resistance heating device which is vacuum-formed from ceramic fibers and according to the preamble of patent claim 1.
  • the invention also relates to a vacuum molding method for producing such a resistance heating device according to the preamble of claim 3.
  • heating modules The basic technique for vacuum forming electrical heating devices, also referred to here as “heating modules”, is described, for example, in US-A-35 00 444 and in a more modern form in US-A-42 78 877 (see DE-Al 28 55 382).
  • heating modules produced by these vacuum molding processes the heating coils or heating spirals are embedded in the ceramic fiber mass in such a way that the interior of the heating coils is normally filled with fiber material.
  • a heating coil 5 is placed on a sieve-like base 1, for example a perforated plate. Under the floor 1 there is a suction box, not shown, through which liquid is drawn off from a top-filled sludge 3, which consists of a slurry of ceramic fibers, binders and water, by means of the vacuum generally indicated with reference 2. The liquid portion is sucked off through the sieve-like base 1 and a layer of ceramic fibers builds up.
  • the interior 8 of the heating coil 5 is generally also filled with ceramic fibers, specifically the density in this interior 8 will correspond approximately to the density of the remaining mass of the ceramic fiber block 4, which is approximately 200 kg / m 3 .
  • the free-radiating surface area 6 of the heating coil 5 is brought to an operating temperature of 1,150 ° C., for example. so on the opposite side (the back 7) of the heating coil 5, which is largely completely embedded in the ceramic fiber mass, a considerably higher temperature will occur. As a result, it is not possible to heat the heating coil on its freely radiating surface side 6 to a maximum desired operating temperature, since the rear side 7 would then be overheated.
  • Another problem associated with the desired maximum possible application or operating temperature of such heating modules is based on the fact that the aluminum silicate fibers which are used predominantly for the fiber mass are only suitable for a maximum permissible operating temperature of 1,150 ° C. Excessive crystallization of the fiber takes place above this temperature, causing it to lose its structure and desired properties entirely. If you now heat the heating coil 5 on the free-radiating surface side 6 to a temperature of approximately 1,150 ° C., 5 temperatures of approximately 1,250 ° C. occur on the rear of the heating coil. This temperature value is then about 100 ° C above the maximum permissible operating temperature of the fiber and will lead to an excessively rapid crystallization of the fiber material.
  • the heating coil loses its hold in the overheated part of the fiber mass and will detach itself from the fiber mass more or less quickly, especially with ceiling elements in an oven space.
  • the heating coil 5 will then initially protrude more and more on the radiating side 9 of the fiber block 4 and will eventually fall out.
  • the invention is therefore based on the object to provide heating modules of the type mentioned and a vacuum molding process for their production, by which it is achieved that the heating coil does not loosen or loosen in its anchoring in the ceramic fiber mass, in particular an aluminum silicate fiber mass when the heating coil is heated to an optimal operating temperature, such that, for example, a temperature of 1,150 ° C. occurs on the radiating side of the module.
  • a vacuum molding process for producing a heating module is the subject of claim 3.
  • the invention achieves, on the one hand, in a simple manner and without the use of plastic hoses that the interior of the heater Spiral remains more or less free of fiber material, so that the temperature difference on the heating coil between the radiating surface of the heating module and the back is significantly reduced and the heating coil can be operated at a significantly higher operating temperature overall without the risk of a gradual loosening there is anchoring within the fiber block.
  • the heating coils in vacuum forming are preferably underlaid by supporting elements, the supporting elements being narrower than the width dimensions of the heating coils in a plane parallel to the radiating surface or narrower than the diameter of the heating coils, means that the heating coils are largely in their interior remain free of fiber material, as can be seen, the openings of the sieve-like bottom in the longitudinal extension of the heating coils are partially closed during the vacuum molding process.
  • the heating coils are underlaid during the vacuum molding process by strip-like elements, hereinafter referred to as “spacer strips”, so that, for reasons explained below, the heating coils are later exposed on the radiating surface of the heating module, but overall are set back into the fiber block by the thickness of the spacer strips, so that optimum anchoring is achieved, but at the same time the interior of the heating coils remains free of fiber material.
  • FIG 3 illustrates a first embodiment: on the sieve-like base 1 (the perforated plate), for example, adhesive strips 10 are applied, which cover the perforation in the longitudinal extent of the heating spirals 5, that is to say in the direction perpendicular to the plane of the drawing. These adhesive strips 10 are attached directly under the heating spirals 5 which are subsequently placed on the perforated plate and are slightly fixed. The partial closure of the perforation does not result in a suction effect caused by the vacuum 2 at these points, so that the interior 8 of the heating spirals 5 remains largely free of ceramic fiber material.
  • FIG. 4 shows the result of the manufacturing method explained with reference to FIG. 3. Similar to the exemplary embodiment in FIG. 2, the heating coil 5 is also flush with the radiating side 9 of the fiber block 4. The interior 8 of the heating coil 5 is now hollow, that is to say free of fiber material, so that the rear side 7 of the heating coil 5 radiates much more freely can. It is thereby achieved that the temperature difference on the heating coil between the free-radiating side 6 on the radiating surface 9 and the rear side 7 is greatly reduced, so that undesired overheating in the area of the rear side 7 of the heating spirals 5 is avoided.
  • this first principle embodiment of the invention still has the disadvantage that the heating coil 5 is now less overall connected to the ceramic fiber block 4, although the above-explained effect of recrystallization of the fibers due to partial overheating is no longer observed.
  • the heating coils 5 are only surrounded by fiber material along their outer circumference and, moreover, they are not held on the free-radiating side 6, as is also the case in the prior art according to FIG. 2.
  • the principle advantage that the crystallization of the fiber material no longer occurs a difficulty can also arise with this construction, however, in that the heating spirals fall out of the fiber block because of inadequate anchoring, especially when such heating modules are used for ceiling constructions in furnace rooms.
  • the significantly improved embodiment of the invention according to FIGS. 5 and 6 is based on the idea of embedding the heating coil 5 on the one hand in the mass of the fiber block 4 in such a way that its interior 8 remains free of ceramic fibers without, on the other hand, the risk of the heating coils 5 can fall out of the fiber block 4 due to poor adhesion.
  • spacer strips 11 are attached to the sieve-like base 1 below the intended positions of the heating spirals.
  • These spacer strips 11 can, for. B. consist of metal, wood or plastic.
  • the width of these spacer strips 11 should in any case be somewhat less than the diameter or the width dimension of the heating coil 5 in a plane parallel to the radiating surface side 9 of the fiber block 4; the thickness of the spacer bars 11 should be in the range of at least 0.1 to approximately 30 mm, preferably in the range of 2 to 10 mm.
  • the silt 3 is now introduced into the frame (not shown in more detail) equipped with the sieve-like bottom 1 and the flux portion is drawn off through the sieve-like bottom 1, the fibers build up in such a way that the spacer strips 11 are enclosed, while the interior 4 of the heating coils 5 largely hollow, ie remains free of fiber deposits.
  • the free-radiating side 6 of the heating coil 5 is no longer flush with the radiating side 9 of the fiber block 4, but is set back into the fiber block 4 by the thickness of the spacer strips 11.
  • the resulting on the spacers 11 retaining webs 12 partially enclose the exposed side 6 of the heating spirals 5, but without the interior 8 is filled with fibers.
  • the desired goal was achieved, namely to keep the interior fiber-free, so that the temperature difference between the radiating side 6 and the back 7 of the heating coils 5 is significantly less than in the conventional technique in which the heating coils are completely, i.e. H. are embedded in the fiber block 4 with a fiber-filled interior 8.
  • the heating spirals 5 are held securely by the holding webs 12, so that there is no longer any danger of falling out, even if such a heating module is used as a ceiling element in an oven.

Abstract

A resistance heating coil is placed on a sieve like tray above a suction box, and a slip of ceramic fibers is placed in the suction box, so that a ceramic fiber layer builds up when suction is applied. Portions of the sieve like tray are closed in regions beneath the resistance heating coil by strips in such a manner that the impervious regions of the sieve like tray are narrower than the width dimensions of the heating coil so that the space inside the heating coil remains free of fiber material during the vacuum moulding operation. This allows the heater to be operated at a higher temperature without the risk of crystallization of the fibers.

Description

Die Erfindung betrifft eine aus keramischen Fasern vakuumgeformte, elektrische, freistrahlende Widerstands-Heizvorrichtung nach dem Oberbegriff des Patentanspruchs 1.The invention relates to an electrical, free-radiating resistance heating device which is vacuum-formed from ceramic fibers and according to the preamble of patent claim 1.

Die Erfindung bezieht sich außerdem auf ein Vakuumformverfahren zur Herstellung einer solchen Widerstands-Heizvorrichtung gemäß dem Oberbegriff des Patentanspruchs 3.The invention also relates to a vacuum molding method for producing such a resistance heating device according to the preamble of claim 3.

Die prinzipielle Technik zum Vakuumformen von hier auch als « Heizmoduln » bezeichneten elektrischen Heizvorrichtungen ist beispielsweise in der US-A-35 00 444 sowie in moderner Form in der US-A-42 78 877 (s DE-Al 28 55 382) beschrieben. Bei nach diesen Vakuum-Formverfahren hergestellten Heizmoduln sind die Heizwendeln oder Heizspiralen in die keramische Fasermasse so eingebettet, daß der Innenraum der Heizwendeln im Normalfall mit Fasermaterial gefüllt ist.The basic technique for vacuum forming electrical heating devices, also referred to here as “heating modules”, is described, for example, in US-A-35 00 444 and in a more modern form in US-A-42 78 877 (see DE-Al 28 55 382). In heating modules produced by these vacuum molding processes, the heating coils or heating spirals are embedded in the ceramic fiber mass in such a way that the interior of the heating coils is normally filled with fiber material.

Dieses übliche Vakuum-Formverfahren wird zunächst anhand der Fig. 1 erläutert :This conventional vacuum molding process is first explained with reference to FIG. 1:

Auf einen siebartigen Boden 1, beispielsweise eine perforierte Platte, wird eine Heizwendel 5 aufgelegt. Unter dem Boden 1 befindet sich ein nicht dargestellter Saugkasten, durch den mittels des allgemein mit dem Bezugshinweis 2 angegebenen Vakuums Flüssigkeit aus einem oberseitig aufgefüllten Schlick 3 abgezogen wird, der aus einer Aufschlämmung von keramischen Fasern, Bindemittel und Wasser besteht. Der Flüssiganteil wird durch den siebartigen Boden 1 abgesaugt und es baut sich eine Schicht aus keramischen Fasern auf. Bei diesem herkömmlichen Verfahren wird in der Regel auch der Innenraum 8 der Heizwendel 5 mit keramischen Fasern gefüllt, und zwar wird die Dichte in diesem Innenraum 8 in etwa der Dichte der übrigen Masse des keramischen Faserblock 4 entsprechen, die etwa 200 kg/m3 beträgt.A heating coil 5 is placed on a sieve-like base 1, for example a perforated plate. Under the floor 1 there is a suction box, not shown, through which liquid is drawn off from a top-filled sludge 3, which consists of a slurry of ceramic fibers, binders and water, by means of the vacuum generally indicated with reference 2. The liquid portion is sucked off through the sieve-like base 1 and a layer of ceramic fibers builds up. In this conventional method, the interior 8 of the heating coil 5 is generally also filled with ceramic fibers, specifically the density in this interior 8 will correspond approximately to the density of the remaining mass of the ceramic fiber block 4, which is approximately 200 kg / m 3 .

Die technischen Schwierigkeiten, die sich beim Gebrauch solcher Heizmodulen ergeben, werden nachfolgend unter Bezug auf die Fig. 2 beschrieben:The technical difficulties that arise when using such heating modules are described below with reference to FIG. 2:

Wird derfreistrahlende Oberflächenbereich 6 der Heizwendel 5 beispielsweise auf eine Betriebstemperatur von 1 150 °C gebracht. so wird auf der gegenüberliegenden Seite (der Rückseite 7) der weitgehend vollständig in die keramische Fasermasse eingebetteten Heizwendel 5 eine beträchtlich höhere Temperatur auftreten. Dadurch ist es nicht möglich, die Heizwendel auf ihrer freistrahlenden Oberflächenseite 6 bis zu einer maximal erwünschten Betriebstemperatur zu erwärmen, da dann die Rückseite 7 überhitzt werden würde.If the free-radiating surface area 6 of the heating coil 5 is brought to an operating temperature of 1,150 ° C., for example. so on the opposite side (the back 7) of the heating coil 5, which is largely completely embedded in the ceramic fiber mass, a considerably higher temperature will occur. As a result, it is not possible to heat the heating coil on its freely radiating surface side 6 to a maximum desired operating temperature, since the rear side 7 would then be overheated.

Um die übermäßige Überhitzung auf der der freistrahlenden Oberflächenseite 6 gegenüberliegend in die Fasermasse eingebetteten Rückseite 7 sowie die Überhitzung im Innern der Heizwendel 5 zu vermeiden, ist es aus der GB-A-14 41 577 bekannt, den Innenraum der Heizwendel 5 während des Vakuumformprozesses mit einem wärmeausschmelzbaren Material, beispielsweise mit einem Kunststoffrohr auszufüllen, das beim ersten Inbetriebnehmen des Heizmoduls ausgeschmolzen und verdampft wird, so daß der Innenraum der Heizwendel 5 dann frei ist von Fasermaterial.In order to avoid the excessive overheating on the back 7 embedded in the fiber mass opposite the free-radiating surface side 6 and the overheating inside the heating coil 5, it is known from GB-A-14 41 577 to include the interior of the heating coil 5 during the vacuum molding process a fusible material, for example, to be filled with a plastic tube which is melted and evaporated when the heating module is started up for the first time, so that the interior of the heating coil 5 is then free of fiber material.

Ein anderes mit der erwünschten maximal möglichen Anwendungs- oder Betriebstemperatur solcher Heizmodulen verbundenes Problem beruht darauf, daß die für die Fasermasse ganz überwiegend verwendeten Aluminium-Silikatfasern nur für eine maximal zulässige Betriebstemperatur von 1 150 °C geeignet sind. Oberhalb dieser Temperatur findet eine übermäßige Kristallisation der Faser statt, wodurch diese ihre Struktur und erwünschten Eigenschaften völlig verliert. Heizt man nun die Heizwendel 5 an der freistrahlenden Oberflächenseite 6 auf eine Temperatur von etwa 1 150 °C auf, so treten an der Rückseite der Heizwendel 5 Temperaturen von ca. 1 250 °C auf. Dieser Temperaturwert liegt dann um ca. 100 °C über der maximal zulässigen Betriebstemperatur der Faser und wird zu einer übermäßig schnellen Kristallisation des Fasermaterials führen. Damit verliert die Heizwendel im überhitzten Teil der Fasermasse ihren Halt und wird sich mehr oder weniger rasch, vor allem bei Deckenelementen in einem Ofenraum, aus der Fasermasse lösen. Die Heizwendel 5 wird dann zunächst an der strahlenden Seite 9 des Faserblocks 4 mehr und mehr hervorstehen und schließlich herausfallen. Um dies zu vermeiden, ist es aus der GB-PS 14 41 577 für eine darin beschriebene weitere Ausführungsform bekannt, die Heizwendel durch ein Zementbett seitlich zu fixieren. Diese Verankerung der Heizwendel erfordert jedoch einen erhöhten Herstellungsaufwand.Another problem associated with the desired maximum possible application or operating temperature of such heating modules is based on the fact that the aluminum silicate fibers which are used predominantly for the fiber mass are only suitable for a maximum permissible operating temperature of 1,150 ° C. Excessive crystallization of the fiber takes place above this temperature, causing it to lose its structure and desired properties entirely. If you now heat the heating coil 5 on the free-radiating surface side 6 to a temperature of approximately 1,150 ° C., 5 temperatures of approximately 1,250 ° C. occur on the rear of the heating coil. This temperature value is then about 100 ° C above the maximum permissible operating temperature of the fiber and will lead to an excessively rapid crystallization of the fiber material. As a result, the heating coil loses its hold in the overheated part of the fiber mass and will detach itself from the fiber mass more or less quickly, especially with ceiling elements in an oven space. The heating coil 5 will then initially protrude more and more on the radiating side 9 of the fiber block 4 and will eventually fall out. To avoid this, it is known from GB-PS 14 41 577 for a further embodiment described therein to fix the heating coil laterally by means of a cement bed. This anchoring of the heating coil, however, requires an increased manufacturing effort.

Der Erfindung liegt damit die Aufgabe zugrunde, Heizmodule der eingangs genannten Art sowie ein Vakuum-Formverfahren zu deren Herstellung zu schaffen, durch die erreicht wird, daß die Heizspirale sich in ihrer Verankerung in der Keramikfasermasse, insbesondere einer Aluminiumsilikatfasermasse, auch dann nicht lockert oder löst, wenn die Heizwendel auf eine optimale Betriebstemperatur aufgeheizt wird, derart, daß an der strahlenden Seite des Moduls beispielsweise eine Temperatur von 1 150 °C auftritt.The invention is therefore based on the object to provide heating modules of the type mentioned and a vacuum molding process for their production, by which it is achieved that the heating coil does not loosen or loosen in its anchoring in the ceramic fiber mass, in particular an aluminum silicate fiber mass when the heating coil is heated to an optimal operating temperature, such that, for example, a temperature of 1,150 ° C. occurs on the radiating side of the module.

Diese Aufgabe wird durch die im kennzeichnenden Teil des Patentanspruchs 1 angegebenen Merkmale gelöst. Ein Vakuum-Formverfahren zur Herstellung eines Heizmoduls ist Gegenstand des Patentanspruchs 3.This object is achieved by the features specified in the characterizing part of patent claim 1. A vacuum molding process for producing a heating module is the subject of claim 3.

Vorteilhafte Ausgestaltungen und Weiterbildungen des erfindungsgemäßen Verfahrens und der erfindungsgemäßen Widerstandsheizvorrichtung sind in den Unteransprüchen angegeben.Advantageous refinements and developments of the method according to the invention and the resistance heating device according to the invention are specified in the subclaims.

Durch die Erfindung wird einerseits auf einfache Weise und ohne die Verwendung von Kunststoffschläuchen erreicht, daß der Innenraum der Heizwendel mehr oder weniger frei bleibt von Fasermaterial, so daß die Temperaturdifferenz an der Heizwendel zwischen der strahlenden Oberfläche des Heizmoduls und der Rückseite wesentlich verringert ist und die Heizwendel insgesamt auf einer deutlich höheren Betriebstemperatur betrieben werden kann, ohne daß andererseits die Gefahr einer allmählichen Lockerung aus der Verankerung innerhalb des Faserblocks besteht.The invention achieves, on the one hand, in a simple manner and without the use of plastic hoses that the interior of the heater Spiral remains more or less free of fiber material, so that the temperature difference on the heating coil between the radiating surface of the heating module and the back is significantly reduced and the heating coil can be operated at a significantly higher operating temperature overall without the risk of a gradual loosening there is anchoring within the fiber block.

Dadurch, daß die Heizwendeln beim VakuumFormen vorzugsweise durch Unterlageelemente unterlegt sind, wobei die Unterlageelemente schmäler sind als die Breitenabmessungen der Heizwendeln in einer Ebene parallel zur strahlenden Oberfläche bzw. schmäler sind als der Durchmesser der Heizwendeln, wird erreicht, daß die Heizwendeln in ihrem Innenraum weitgehend frei bleiben von Fasermaterial, da ersichtlich die Öffnungen des siebartigen Bodens in Längserstreckung der Heizwendeln während des Vakuum-Formvorgangs partiell verschlossen sind.The fact that the heating coils in vacuum forming are preferably underlaid by supporting elements, the supporting elements being narrower than the width dimensions of the heating coils in a plane parallel to the radiating surface or narrower than the diameter of the heating coils, means that the heating coils are largely in their interior remain free of fiber material, as can be seen, the openings of the sieve-like bottom in the longitudinal extension of the heating coils are partially closed during the vacuum molding process.

Bei einer besonders vorteilhaften Ausführungsform der Erfindung werden die Heizwendeln während des Vakuum-Formvorgangs durch streifenartige Elemente, im folgenden « Distanzleisten » genannt, unterlegt, so daß aus weiter unten noch erläuterten Gründen die Heizwendeln später zwar an der strahlenden Oberfläche des Heizmoduls freiliegen, jedoch insgesamt um die Dicke der Distanzleisten in den Faserblock hinein zurückversetzt sind, so daß eine optimale Verankerung erreicht wird, gleichzeitig jedoch der Innenraum der Heizwendeln frei bleibt von Fasermaterial.In a particularly advantageous embodiment of the invention, the heating coils are underlaid during the vacuum molding process by strip-like elements, hereinafter referred to as “spacer strips”, so that, for reasons explained below, the heating coils are later exposed on the radiating surface of the heating module, but overall are set back into the fiber block by the thickness of the spacer strips, so that optimum anchoring is achieved, but at the same time the interior of the heating coils remains free of fiber material.

Ausführungsbeispiele der Erfindung werden nachfolgend anhand der Zeichnung näher erläutert. Es zeigen :

  • Fig. 1 und 2 den bereits erläuterten Stand der Technik ;
  • Fig. 3 ein erstes Ausführungsbeispiel zur Erläuterung des erfindungsgemäßen Vakuum-Formverfahrens:
  • Fig. 4 in schematischer Darstellung das Produkt als Ergebnis des Vakuum-Formverfahrens nach Fig. 3 ;
  • Fig. 5 ein zu bevorzugendes Ausführungsbeispiel für ein erfindungsgemäßes Vakuum-Formverfahren ; und
  • Fig. 6 wiederum in schematischer Darstellung das Produkt des Vakuum-Formverfahrens nach
  • Fig. 5 zur Erläuterung bestimmter vorteilhafter Eigenschaften.
Exemplary embodiments of the invention are explained in more detail below with reference to the drawing. Show it :
  • 1 and 2 the already explained prior art;
  • 3 shows a first exemplary embodiment to explain the vacuum molding process according to the invention:
  • 4 shows a schematic representation of the product as a result of the vacuum molding process according to FIG. 3;
  • 5 shows a preferred exemplary embodiment for a vacuum molding process according to the invention; and
  • Fig. 6 again in a schematic representation of the product of the vacuum molding process
  • Fig. 5 for explaining certain advantageous properties.

Einander entsprechende Teile sind in allen Figuren mit den gleichen Bezugshinweisen gekennzeichnet.Corresponding parts are identified in all figures with the same reference notes.

Die Fig. 3 verdeutlicht eine erste Ausführungsform : Auf dem siebartigen Boden 1 (der perforierten Platte) werden beispielsweise Klebestreifen 10 aufgebracht, welche die Perforation in Längserstreckung der Heizspiralen 5, also in senkrechter Richtung zur Zeichenebene, abdecken. Diese Klebestreifen 10 werden direkt unter der anschließend auf die perforierte Platte aufgelegten und leicht fixierten Heizspiralen 5 angebracht. Durch das partielle Verschließen der Perforation entsteht an diesen Stellen keine durch das Vakuum 2 verursachte Saugwirkung, so daß der Innenraum 8 der Heizspiralen 5 weitestgehend frei bleibt von keramischem Fasermaterial.3 illustrates a first embodiment: on the sieve-like base 1 (the perforated plate), for example, adhesive strips 10 are applied, which cover the perforation in the longitudinal extent of the heating spirals 5, that is to say in the direction perpendicular to the plane of the drawing. These adhesive strips 10 are attached directly under the heating spirals 5 which are subsequently placed on the perforated plate and are slightly fixed. The partial closure of the perforation does not result in a suction effect caused by the vacuum 2 at these points, so that the interior 8 of the heating spirals 5 remains largely free of ceramic fiber material.

Die Fig. 4 zeigt das Ergebnis des anhand der Fig. 3 erläuterten Herstellungsverfahrens. Ähnlich wie beim Ausführungsbeispiel der Fig. 2 liegt auch hier die Heizspirale 5 bündig mit der strahlenden Seite 9 des Faserblocks 4. Der Innenraum 8 der Heizspiralen 5 ist jetzt hohl, also frei von Fasermaterial, so daß die Rückseite 7 der Heizspiralen 5 wesentlich freier abstrahlen kann. Damit ist erreicht, daß der Temperaturunterschied an der Heizspirale zwischen der freistrahlenden Seite 6 an der strahlenden Oberfläche 9 und der Rückseite 7 stark verringert ist, so daß eine unerwünschte Überhitzung im Bereich der Rückseite 7 der Heizspiralen 5 vermieden ist.FIG. 4 shows the result of the manufacturing method explained with reference to FIG. 3. Similar to the exemplary embodiment in FIG. 2, the heating coil 5 is also flush with the radiating side 9 of the fiber block 4. The interior 8 of the heating coil 5 is now hollow, that is to say free of fiber material, so that the rear side 7 of the heating coil 5 radiates much more freely can. It is thereby achieved that the temperature difference on the heating coil between the free-radiating side 6 on the radiating surface 9 and the rear side 7 is greatly reduced, so that undesired overheating in the area of the rear side 7 of the heating spirals 5 is avoided.

Diese erste prinzipielle Ausführungsform der Erfindung hat jedoch noch den Nachteil, daß die Heizspirale 5 jetzt insgesamt weniger gut mit dem keramischen Faserblock 4 verbunden ist, obgleich der oben erläuterte Effekt der Umkristallisation der Fasern aufgrund von partieller Überhitzung nicht mehr beobachtet wird. Die Heizspiralen 5 sind jedoch nur entlang ihres äußeren Umfangs von Fasermaterial umgeben und sie werden überdies an der freistrahlenden Seite 6 nicht gehalten, wie dies auch beim Stand der Technik nach Fig. 2 der Fall ist. Trotz des prinzipiellen Vorteils, daß die Kristallisation des Fasermaterials nicht mehr auftritt, kann jedoch auch bei dieser Konstruktion noch eine Schwierigkeit dadurch entstehen, daß die Heizspiralen wegen unzureichender Verankerung aus dem Faserblock herausfallen, insbesondere, wenn solche Heizmoduln für Deckenkonstruktionen in Ofenräumen eingesetzt werden.However, this first principle embodiment of the invention still has the disadvantage that the heating coil 5 is now less overall connected to the ceramic fiber block 4, although the above-explained effect of recrystallization of the fibers due to partial overheating is no longer observed. However, the heating coils 5 are only surrounded by fiber material along their outer circumference and, moreover, they are not held on the free-radiating side 6, as is also the case in the prior art according to FIG. 2. Despite the principle advantage that the crystallization of the fiber material no longer occurs, a difficulty can also arise with this construction, however, in that the heating spirals fall out of the fiber block because of inadequate anchoring, especially when such heating modules are used for ceiling constructions in furnace rooms.

Der wesentlich verbesserten Ausführungsform der Erfindung nach den Fig. 5 und 6 liegt die Idee zugrunde, die Heizspirale 5 einerseits so in die Masse des Faserblocks 4 einzubetten, daß deren Innenraum 8 frei bleibt von keramischen Fasern, ohne andererseits Gefahr zu laufen, daß die Heizspiralen 5 durch mangelhafte Haftung aus dem Faserblock 4 herausfallen können.The significantly improved embodiment of the invention according to FIGS. 5 and 6 is based on the idea of embedding the heating coil 5 on the one hand in the mass of the fiber block 4 in such a way that its interior 8 remains free of ceramic fibers without, on the other hand, the risk of the heating coils 5 can fall out of the fiber block 4 due to poor adhesion.

Das Prinzip der Herstellung wird zunächst anhand der schematischen Schnittdarstellung der Fig. 5 erläutert: Auf dem siebartigen Boden 1 werden unterhalb der vorgesehenen Positionen der Heizspiralen 5 Distanzleisten 11 angebracht. Diese Distanzleisten 11 können z. B. aus Metall, Holz oder Kunststoff bestehen. Die Breite dieser Distanzleisten 11 sollte auf jeden Fall etwas geringer sein als der Durchmesser bzw. die Breitenabmessung der Heizspirale 5 in einer Ebene parallel zur strahlenden Oberflächenseite 9 des Faserblocks 4 ; die Dicke der Distanzleisten 11 sollte im Bereich von wenigstens 0,1 bis ca. 30 mm, vorzugsweise im Bereich von 2 bis 10mm, liegen. Wird nun der Schlick 3 in den mit dem siebartigen Boden 1 ausgerüsteten nicht näher gezeigten Rahmen eingebracht und wird der Flussiganteil durch den siebartigen Boden 1 abgezogen, so bauen sich die Fasern derart auf, daß die Distanzleisten 11 umschlossen werden, während der Innenraum 4 der Heizspiralen 5 weitgehend hohl, d. h. frei von Faserablagerungen bleibt.The principle of manufacture is first explained with the aid of the schematic sectional illustration in FIG. 5: 5 spacer strips 11 are attached to the sieve-like base 1 below the intended positions of the heating spirals. These spacer strips 11 can, for. B. consist of metal, wood or plastic. The width of these spacer strips 11 should in any case be somewhat less than the diameter or the width dimension of the heating coil 5 in a plane parallel to the radiating surface side 9 of the fiber block 4; the thickness of the spacer bars 11 should be in the range of at least 0.1 to approximately 30 mm, preferably in the range of 2 to 10 mm. If the silt 3 is now introduced into the frame (not shown in more detail) equipped with the sieve-like bottom 1 and the flux portion is drawn off through the sieve-like bottom 1, the fibers build up in such a way that the spacer strips 11 are enclosed, while the interior 4 of the heating coils 5 largely hollow, ie remains free of fiber deposits.

Die Fig. 6 zeigt in einer prinzipiellen Schnittdarstellung das Produktergebnis: Die freistrahlende Seite 6 der Heizspirale 5 liegt jetzt nicht mehr bündig mit der strahlenden Seite 9 des Faserblocks 4, sondern liegt um die Dicke der Distanzleisten 11 in den Faserblock 4 zurückversetzt. Die aufgrund der Distanzleisten 11 entstehenden Haltestege 12 umschließen die freistrahlende Seite 6 der Heizspiralen 5 teilweise, ohne daß jedoch der Innenraum 8 mit Fasern gefüllt ist. Damit wurde das angestrebte Ziel erreicht, nämlich, den Innenraum faserfrei zu halten, so daß die Temperaturdifferenz zwischen der strahlenden Seite 6 und der Rückseite 7 der Heizspiralen 5 wesentlich geringer ist als bei der herkömmlichen Technik, bei der die Heizspiralen komplett, d. h. mit fasergefülltem Innenraum 8 in den Faserblock 4 eingebettet sind. Andererseits aber werden die Heizspiralen 5 durch die Haltestege 12 sicher gehalten, so daß keine Gefahr des Herausfallens mehr besteht, auch wenn ein solcher Heizmodul als Deckenelement in einem Ofen verwendet wird.6 shows a basic sectional illustration of the product result: the free-radiating side 6 of the heating coil 5 is no longer flush with the radiating side 9 of the fiber block 4, but is set back into the fiber block 4 by the thickness of the spacer strips 11. The resulting on the spacers 11 retaining webs 12 partially enclose the exposed side 6 of the heating spirals 5, but without the interior 8 is filled with fibers. Thus, the desired goal was achieved, namely to keep the interior fiber-free, so that the temperature difference between the radiating side 6 and the back 7 of the heating coils 5 is significantly less than in the conventional technique in which the heating coils are completely, i.e. H. are embedded in the fiber block 4 with a fiber-filled interior 8. On the other hand, the heating spirals 5 are held securely by the holding webs 12, so that there is no longer any danger of falling out, even if such a heating module is used as a ceiling element in an oven.

Bei den beschriebenen Ausführungsformen der Erfindung sind, wie die Figuren erkennen lassen, sogenannte ovale Heizspiralen oder Heizwendeln 5 vorgesehen, wie sie auch in der oben erwähnten US-PS 4 278 877 mit den dort erwähnten Vorteilen beschrieben sind. Für den Fachmann ist ohne weiteres ersichtlich, daß sich die Erfindung auch für Heizspiralen mit anderen Querschnitten, beispielsweise mit rundem Querschnitt oder zu einem Rechteck verformten Querschnitt, mit Vorteil einsetzen läßt.In the described embodiments of the invention, as can be seen from the figures, so-called oval heating spirals or heating coils 5 are provided, as are also described in the above-mentioned US Pat. No. 4,278,877 with the advantages mentioned therein. It is readily apparent to the person skilled in the art that the invention can also be used advantageously for heating spirals with other cross sections, for example with a round cross section or a cross section deformed into a rectangle.

Claims (6)

1. Free-radiating electrical resistance-heating device, vacuum-formed from ceramic fibres, with a resistance-heating coil (5) which is embedded directly in a ceramic-fibre layer and is anchored in this by retaining webs (12) partially surrounding the free-radiating side (6) and which is essentially free of ceramic-fibre material in its interior (8), and a surface region (6) of which is exposed on the radiating heating surface (9), characterized in that those surface regions (6) of the heating coil (5) which are exposed on the heating surface (9) are offset inwards in their entirety by a distance of 2 to 30 mm relative to the outer surface (9) of the ceramic fibre layer (4).
2. Heating device according to Claim 1, characterized in that the distance between the exposed surface regions (6) of the heating coil (5) and the outer surface (9) of the ceramic-fibre layer (4) is 2 to 10 mm.
3. Vacuum-forming process for producing an electrical resistance-heating device, in which a resistance-heating coil (5) is laid on a sieve-like base (1) of a frame above a suction box, and a silt consisting of a slurry of ceramic fibres, binder and water is introduced into the frame, so that there builds up under the suction effect a ceramic fibre layer which is hardened and which contains the resistance-heating coil as an embedded heating element (5), characterized in that the surface portions of the sieve-like base (1) which are located under the resistance-heating coil (5) are made impermeable to liquid by strips (11) placed in the positions of the heating coil(s) before the heating coil(s) is laid on the sieve-like base (1) in an area which is narrower than the maximum diameter or width dimension of the heating coil in a plane offset inwards and parallel to the radiating surface, so that the interior of the heating coil (5) remains essentially free of ceramic fibres during the sucking-off operation.
4. Vacuum-forming process according to Claim 3, characterized in that the surface portions impermeable to liquid are formed by strips (11) and are placed in the positions of the heating coil (5) before the latter is laid on the sieve-like base (1).
5. Vacuum-forming process according to Claim 3, characterized in that the surface portions impermeable to liquid are formed by strips (11) and are fastened to the heating coil (5) on the side facing the sieve-like base (1), so as to adhere to it in an easily releasable manner.
6. Vacuum-forming process according to Claim 4 or 5, characterized in that the strips (11) are designed as spacer strips with a thickness of 0.1 to 30 mm, preferably with a thickness of 2 to 10 mm.
EP83108349A 1982-09-07 1983-08-24 Vacuum-formed electrical heating unit and method of making it Expired - Lifetime EP0105175B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT83108349T ATE32157T1 (en) 1982-09-07 1983-08-24 VACUUM-FORMED ELECTRIC HEATING DEVICE AND METHOD OF MANUFACTURE THERE.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3233181 1982-09-07
DE3233181A DE3233181C2 (en) 1982-09-07 1982-09-07 Vacuum-formed, electric, radiant resistance heating device for industrial furnaces and processes for their production, made from ceramic fibers.

Publications (3)

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EP0105175A1 EP0105175A1 (en) 1984-04-11
EP0105175B1 EP0105175B1 (en) 1988-01-20
EP0105175B2 true EP0105175B2 (en) 1993-06-23

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EP83108349A Expired - Lifetime EP0105175B2 (en) 1982-09-07 1983-08-24 Vacuum-formed electrical heating unit and method of making it

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US (1) US4617450A (en)
EP (1) EP0105175B2 (en)
JP (1) JPS5966094A (en)
AT (1) ATE32157T1 (en)
CA (1) CA1213635A (en)
DE (1) DE3233181C2 (en)
MX (1) MX153420A (en)

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Also Published As

Publication number Publication date
US4617450A (en) 1986-10-14
EP0105175A1 (en) 1984-04-11
MX153420A (en) 1986-10-07
DE3233181C2 (en) 1985-08-01
CA1213635A (en) 1986-11-04
DE3233181A1 (en) 1984-03-08
EP0105175B1 (en) 1988-01-20
JPS5966094A (en) 1984-04-14
ATE32157T1 (en) 1988-02-15

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