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EP0348716A2 - Thermal switch - Google Patents

Thermal switch Download PDF

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Publication number
EP0348716A2
EP0348716A2 EP89110509A EP89110509A EP0348716A2 EP 0348716 A2 EP0348716 A2 EP 0348716A2 EP 89110509 A EP89110509 A EP 89110509A EP 89110509 A EP89110509 A EP 89110509A EP 0348716 A2 EP0348716 A2 EP 0348716A2
Authority
EP
European Patent Office
Prior art keywords
radiation
tube
temperature switch
temperature
switch according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP89110509A
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German (de)
French (fr)
Other versions
EP0348716A3 (en
EP0348716B1 (en
Inventor
Gerhard Gössler
Eugen Wilde
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EGO Elektro Geratebau GmbH
Original Assignee
EGO Elektro Gerate Blanc und Fischer GmbH
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.)
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Publication date
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Priority claimed from DE19883821496 external-priority patent/DE3821496A1/en
Priority claimed from DE19883821495 external-priority patent/DE3821495A1/en
Application filed by EGO Elektro Gerate Blanc und Fischer GmbH filed Critical EGO Elektro Gerate Blanc und Fischer GmbH
Publication of EP0348716A2 publication Critical patent/EP0348716A2/en
Publication of EP0348716A3 publication Critical patent/EP0348716A3/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
    • H05B1/00—Details of electric heating devices
    • H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
    • H05B1/0202—Switches
    • H05B1/0216—Switches actuated by the expansion of a solid element, e.g. wire or rod
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/68—Heating arrangements specially adapted for cooking plates or analogous hot-plates
    • H05B3/74—Non-metallic plates, e.g. vitroceramic, ceramic or glassceramic hobs, also including power or control circuits
    • H05B3/742—Plates having both lamps and resistive heating elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/02—Details
    • H01H37/32—Thermally-sensitive members
    • H01H37/46—Thermally-sensitive members actuated due to expansion or contraction of a solid
    • H01H37/48—Thermally-sensitive members actuated due to expansion or contraction of a solid with extensible rigid rods or tubes

Definitions

  • the invention relates to a temperature switch according to the preamble of claim 1.
  • EP-B-116 861 describes a temperature switch of this type in which a web made of the insulating material of the radiant heater in which it is installed causes radiation shielding and thus a temporary delay in response. This makes it possible to bring the radiant heater to a higher temperature level in the heating or boiling phase, which is then lowered to a steady state during further operation, which certainly does not damage the glass ceramic plate in continuous operation.
  • EP-B-150 087 discloses a temperature switch for heating a glass ceramic plate, in which a quartz glass tube is used which selectively only absorbs radiation with a wavelength which is reflected back from the glass ceramic plate in order to respond to the temperature switch to the temperature of the glass ceramic plate allow. The radiation coming from the radiation source should be let through. This means that a temporary response delay cannot be achieved.
  • the object of the invention is to provide a temperature switch which avoids the disadvantages of the prior art and is particularly simple and effective.
  • the tube preferably at least partially comprises or consists of a radiation-absorbing material
  • the radiation-absorbing material primarily absorbs and absorbs the radiation from the radiant heater. So initially it does not come to the expansion rod. However, the tube heats up and in turn emits heat, albeit with a delay, to the expansion rod due to its own radiation and convection. Since the material of the tube has a lower, but not completely negligible expansion coefficient than the expansion rod, the increased initial heating of the tube compared to the expansion rod also has a certain countercompensating effect sation, which increases the delay effect. In further operation, the switching amplitude, which is very low as a result of the very sensitive switch basic characteristic, is increased as desired and thus the switching frequency is reduced.
  • This retarding effect can be dimensioned as desired in that the tube either completely or partially has the radiation-absorbing material. This could be designed as a coating, for example. However, the tube itself is preferably made of radiation-absorbing material.
  • the retarding effect is further improved if the tube has an increased thermal inertia. This means that it has an increased mass and / or specific heat, so that the radiant heat is stored before it is passed on to the expansion rod. After the heating element has been switched off, this heat still acts on the expansion rod and delays its cooling. A low thermal conductivity of the pipe material also contributes to this.
  • the tube preferably consists of a sintered ceramic material, for example of cordierite, which has excellent radiation absorption properties with low reflection values.
  • the tube from a glass ceramic, in particular with low transmission properties.
  • Low transmission properties can be created by adding a metal oxide.
  • Manufacture from radiation-absorbing, non-transmissive quartz has also proven successful.
  • the expansion rod consists at least partially of a chromium-iron-aluminum alloy which is heat-treated at a temperature above 800 ° C (approx. 1100 K), preferably above 1100 ° C (approx. 1400 K)
  • the switching amplitude has increased significantly, for example from ⁇ 2 K to ⁇ 5.5 K.
  • the chromium-iron-aluminum alloy which preferably contains approximately 22% chromium and approximately 5% aluminum, is available under the name "Kanthal A, Al, AF" from the company AB Kanthal, Sweden, and was previously used as electrical Resistor material used. In conjunction with the heat treatment, it causes the specified values of the thermal delay or increase in the switching amplitude.
  • the temperature switch can be used particularly advantageously in the case of a radiant heating element having at least one high-temperature radiant heater, for example a heating resistor enclosed by a lamp bulb. Because of its fast response, the switching amplitude could otherwise become very small and thus result in an increased switching frequency, which would be impermissible, above all because of the high starting currents of such high-temperature radiant heaters.
  • the temporary response delay effect can be dimensioned such that it allows a brief initial overheating of the glass ceramic plate, which due to its short duration does not cause any damage, but it can also be dimensioned so that it delays the heating of the glass ceramic plate, which is present anyway due to the higher mass of the glass ceramic plate compensated.
  • the drawing shows a schematic representation of a radiant heater 11, which is arranged below a glass ceramic plate 12 and heats it.
  • a carrier shell 33 there is insulation 42.
  • Heating resistors 13 or 14 are provided in the form of a heating coil 13 partially embedded in the insulation 42 and in the form of a high-temperature radiant heater 14, which is, for example, a halogen lamp, the heating coil 15 of which is made of tungsten or similar materials is contained in a quartz lamp body 16 and, due to temperatures above 1500 K, has a radiation spectrum largely in the visible range.
  • a temperature sensor 20 of a temperature switch 21 projects through edges 17 of the insulation 12 reaching as far as the glass ceramic plate 12 and projects between the glass ceramic plate 12 and the radiators 13, 14 across the radiant heater.
  • the temperature switch 21 is a fixed, but adjustable temperature limiter, the switching mechanism indicated as a snap switch 22 switches off the radiators 13 and / or 14 or in another way reduces their output when the limiting temperature is reached.
  • the temperature switch 21 can also open a second one have a different temperature-adjusted switching mechanism that can be used, for example, to display the hot state of the glass ceramic plate.
  • the switching mechanism 22 and possibly the further switching mechanism are actuated by an expansion rod 24. It is arranged in a tube 25, which consists of a material that has a substantially lower coefficient of thermal expansion than the expansion rod 24.
  • the expansion rod 24 is loaded by a spring 26 engaging a thickened head 30 of the expansion rod 24 in the switch head 27 of the temperature switch 21 lying outside the heated area of the radiant heater in the direction of the snap switch, so that it has one at its free end on a thread 28 arranged adjusting nut 29 against the end of the tube 25 and thus the tube also pulls against the switch head.
  • This so-called tension rod arrangement in which the tension rod is the thermally active part, enables a relatively simple assembly because the temperature sensor is held in a force-fitting manner by the spring itself and, despite some flexibility in the attachment, the adjustment accuracy does not suffer.
  • the expansion rod 24 consists of a chromium-iron-aluminum alloy, which preferably contains approximately 22% chromium and 5% aluminum and which is manufactured by AB Kanthal, Sweden, under the name Kanthal A or Al or AF as a heating conductor. Alloy is produced.
  • the rod made of this material after being provided with a head 30 for the engagement of the spring 26 and the thread 28, is subjected to a pre-aging in a temperature above 800 ° C, preferably at about 1200 ° C in a normal atmosphere. This also reduces the stress caused by the mechanical deformation. This surprisingly increases the switching amplitude by approximately ⁇ 3 K.
  • This material is a glass ceramic with low transmission and high radiation absorption, which is achieved by adding a metal oxide.
  • a tube 25 made of opaque quartz was successfully examined, for example from the material 'Rotosil' from Heraeus.
  • the impermeability to radiation and absorption capacity were achieved by adding metal oxides.
  • the switching amplitude should be of the order of magnitude between 4 and 10 K (preferably 5 to 7 K) in order to achieve a switching frequency that is less than 5 switching operations per minute. Otherwise, the maximum number of operations per minute specified by local regulations (due to network or radio interference) could be exceeded.
  • the radiation-absorbing design of the tube 25 is particularly advantageous when the thermal mass is increased. This can be done by substantially exceeding the usual wall thickness of 1 mm for pipes of this type and preferably up to 3 mm. It would also be possible to provide other heat-storing means on the pipe. It is also conceivable to provide the radiation-absorbing properties in a surface coating, while the tube has heat-storing properties. By using a pipe material with low thermal conductivity, the heat transfer from the pipe to the expansion rod can be hindered, which would also be achievable through intermediate insulation measures.
  • the radiation-absorbing material used on the tube is preferably radiation-absorbing in the entire wavelength range which is essential for the radiation heating, in particular in the area which comes directly from the respective radiation source, so that the response behavior is mainly from the heating and not from secondary radiators, e.g. the glass ceramic plate. This characteristic is guaranteed for the materials described, but can also be achieved with other materials.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Resistance Heating (AREA)
  • Thermally Actuated Switches (AREA)
  • Oscillators With Electromechanical Resonators (AREA)
  • Devices That Are Associated With Refrigeration Equipment (AREA)
  • Switches With Compound Operations (AREA)
  • Glass Compositions (AREA)
  • Electric Stoves And Ranges (AREA)

Abstract

A thermal switch, serving especially as a temperature limiter for a radiant heating body (11) for heating a glass-ceramic plate (12), has radiant heaters (13, 14). Its bar-shaped temperature sensor (20) has an expansion bar (24) which is located in a tube (25) serving as a reference and which can consist of a chromium/iron/aluminium alloy and is heat-treated above 1100 DEG C. The tube (25) can consist of a radiation-absorbing material or is coated with such, for example cordierite, non-transmissive glass ceramic or vitreous silica. Both measures ensure that the thermal switch has an increased switching amplitude and therefore a reduced switching frequency. <IMAGE>

Description

Die Erfindung betrifft einen Temperaturschalter nach dem Oberbegriff des Anspruchs 1.The invention relates to a temperature switch according to the preamble of claim 1.

Aus der EP-B-116 861 ist ein Temperaturschalter dieser Art beschrieben, bei dem ein Steg aus dem Isoliermaterial des Strahlheizkörpers, in den er eingebaut ist, eine Strahlungs­abschirmung und damit eine temporäre Ansprechverzögerung bewirkt. Dadurch ist es möglich, in der Anheiz- bzw. Ankoch­phase den Strahlheizkörper auf ein höheres Temperaturniveau zu bringen, das dann beim weiteren Betrieb auf einen Behar­rungszustand abgesenkt wird, der mit Sicherheit keine Schä­digung der Glaskeramikplatte im Dauerbetrieb bewirkt.EP-B-116 861 describes a temperature switch of this type in which a web made of the insulating material of the radiant heater in which it is installed causes radiation shielding and thus a temporary delay in response. This makes it possible to bring the radiant heater to a higher temperature level in the heating or boiling phase, which is then lowered to a steady state during further operation, which certainly does not damage the glass ceramic plate in continuous operation.

Außerdem wird dadurch die Schaltamplitude bzw. -hysterese vergrößert, so daß die Schalthäufigkeit unter allen Bedin­gungen auf einen zulässigen wert gesenkt werden kann.This also increases the switching amplitude or hysteresis, so that the switching frequency can be reduced to a permissible value under all conditions.

Aus der EP-B-150 087 geht ein Temperaturschalter für die Beheizung einer Glaskeramikplatte hervor, bei dem ein Quarz­glasrohr verwendet wird, das selektiv nur Strahlung mit einer Wellenlänge absorbiert, die von der Glaskeramikplatte zurückgestrahlt wird, um den Temperaturschalter auf die Tem­peratur der Glaskeramikplatte ansprechen zu lassen. Die von der Strahlungsquelle kommende Strahlung soll durchgelassen werden. Damit kann eine temporäre Ansprechverzögerung nicht erreicht werden.EP-B-150 087 discloses a temperature switch for heating a glass ceramic plate, in which a quartz glass tube is used which selectively only absorbs radiation with a wavelength which is reflected back from the glass ceramic plate in order to respond to the temperature switch to the temperature of the glass ceramic plate allow. The radiation coming from the radiation source should be let through. This means that a temporary response delay cannot be achieved.

Zum gleichen Zweck und aufbauend auf dem gleichen Prinzip wird bei der WO85/01412 der Ausdehnungsstab oder das ihn umgebende Rohr mit einer Strahlung reflektierenden Beschich­tung versehen. Diese reflektierende Beschichtung erfordert zusätzliche Maßnahmen bei der Herstellung und ist im Betrieb auch in ihrer Wirkung gefährdet, da die Reflektionsfähigkeit nachlassen kann.For the same purpose and based on the same principle, in WO85 / 01412 the expansion rod or the tube surrounding it is provided with a radiation-reflecting coating. This reflective coating requires additional measures during manufacture and its effectiveness is also jeopardized in operation, since the reflectivity can deteriorate.

Aufgabe der Erfindung ist es, einen Temperaturschalter zu schaffen, der die Nachteile des Standes der Technik vermei­det und besonders einfach und wirksam aufgebaut ist.The object of the invention is to provide a temperature switch which avoids the disadvantages of the prior art and is particularly simple and effective.

Diese Aufgabe wird durch den Anspruch 1 gelöst.This object is solved by claim 1.

Wenn vorzugsweise das Rohr zumindest teilweise ein strah­lungsabsorbierendes Material aufweist, oder aus diesem be­steht, dann nimmt das strahlungsabsorbierende Material pri­mär die Strahlung des Strahlheizkörpers auf und absorbiert sie. Sie kommt also anfänglich nicht an den Ausdehnungsstab. Das Rohr heizt sich dabei jedoch auf und gibt seinerseits Wärme, wenn auch mit Verzögerung, durch Eigenstrahlung und Konvektion an den Ausdehnungsstab ab. Da das Material des Rohres zwar einen geringeren, jedoch nicht gänzlich vernach­lässigbaren Ausdehnungskoeffizienten hat als der Ausdehn­ungsstab, bewirkt die erhöhte Anfangsaufheizung des Rohres gegenüber dem Ausdehnungsstab auch eine gewisse Gegenkompen­ sation, was die Verzögerungswirkung noch verstärkt. Im wei­teren Betrieb wird die infolge der sehr ansprechungsempfind­lichen Schalter-Grundcharakteristik sehr geringe Schalt­amplitude wunschgemäß vergrößert und damit die Schalthäufig­keit herabgesetzt.If the tube preferably at least partially comprises or consists of a radiation-absorbing material, then the radiation-absorbing material primarily absorbs and absorbs the radiation from the radiant heater. So initially it does not come to the expansion rod. However, the tube heats up and in turn emits heat, albeit with a delay, to the expansion rod due to its own radiation and convection. Since the material of the tube has a lower, but not completely negligible expansion coefficient than the expansion rod, the increased initial heating of the tube compared to the expansion rod also has a certain countercompensating effect sation, which increases the delay effect. In further operation, the switching amplitude, which is very low as a result of the very sensitive switch basic characteristic, is increased as desired and thus the switching frequency is reduced.

Diese Verzögerungswirkung kann dadurch wunschgemäß bemessen werden, daß das Rohr entweder ganz oder teilweise das strah­lungsabsorbierende Material aufweist. Dies könnte zum Bei­spiel als Beschichtung ausgebildet sein. Vorzugsweise ist aber das Rohr selbst aus strahlungsabsorbierendem Material hergestellt.This retarding effect can be dimensioned as desired in that the tube either completely or partially has the radiation-absorbing material. This could be designed as a coating, for example. However, the tube itself is preferably made of radiation-absorbing material.

Die Verzögerungswirkung wird ferner verbessert, wenn das Rohr eine erhöhte thermische Trägheit aufweist. Das bedeu­tet, daß es eine erhöhte Masse und/oder spezifische Wärme aufweist, so daß die Strahlungswärme gespeichert wird, bevor sie an den Ausdehnungsstab weitergegeben wird. Diese Wärme wirkt nach dem Abschalten des Heizelementes noch auf den Ausdehnungsstab ein und verzögert seine Abkühlung. Auch eine geringe thermische Leitfähigkeit des Rohrmaterials trägt dazu bei.The retarding effect is further improved if the tube has an increased thermal inertia. This means that it has an increased mass and / or specific heat, so that the radiant heat is stored before it is passed on to the expansion rod. After the heating element has been switched off, this heat still acts on the expansion rod and delays its cooling. A low thermal conductivity of the pipe material also contributes to this.

Bevorzugt besteht das Rohr aus einem durchgesinterten kera­mischen Material, beispielsweise aus Cordierit, das ausge­zeichnete Strahlungsabsorptions-Eigenschaften bei geringen Reflektionswerten aufweist.The tube preferably consists of a sintered ceramic material, for example of cordierite, which has excellent radiation absorption properties with low reflection values.

Es ist jedoch auch vorteilhaft möglich, das Rohr aus einer Glaskeramik, insbesondere mit geringen Transmissions-Eigen­schaften, herzustellen. Geringe Transmissions-Eigenschaften können durch eine Metalloxid-Beimischung erzeugt werden. Auch eine Herstellung aus strahlungsabsorbierendem, nicht­transmissivem Quarzgut hat sich bewährt.However, it is also advantageously possible to produce the tube from a glass ceramic, in particular with low transmission properties. Low transmission properties can be created by adding a metal oxide. Manufacture from radiation-absorbing, non-transmissive quartz has also proven successful.

Wenn der Ausdehnungsstab bei einer bevorzugten Ausführung zumindest teilweise aus einer Chrom-Eisen-Aluminium-Legie­rung besteht, die bei einer Temperatur oberhalb 800 °C (ca. 1100 K), vorzugsweise oberhalb 1100 °C (ca. 1400 K) wärmebe­handelt ist, wird erstaunlicherweise gegenüber dem üblichen Chrom-Nickel-Material, das für den Ausdehnungsstab bisher verwendet wurde, eine wesentliche Erhöhung der Schaltampli­tude von beispielsweise ± 2 K auf ± 5,5 K erreicht. Die Chrom-Eisen-Aluminium-Legierung, die vorzugsweise ca. 22 % Chrom und ca. 5 % Aluminium enthält, ist unter der Bezeich­nung "Kanthal A, Al, AF" von der Firma AB Kanthal, Schweden, erhältlich und wurde bisher als elektrisches Widerstandsma­terial verwendet. In Verbindung mit der Wärmebehandlung be­wirkt es die angegebenen Werte der thermischen Verzögerung bzw. Erhöhung der Schaltamplitude.If, in a preferred embodiment, the expansion rod consists at least partially of a chromium-iron-aluminum alloy which is heat-treated at a temperature above 800 ° C (approx. 1100 K), preferably above 1100 ° C (approx. 1400 K) Surprisingly, compared to the usual chromium-nickel material that was previously used for the expansion rod, the switching amplitude has increased significantly, for example from ± 2 K to ± 5.5 K. The chromium-iron-aluminum alloy, which preferably contains approximately 22% chromium and approximately 5% aluminum, is available under the name "Kanthal A, Al, AF" from the company AB Kanthal, Sweden, and was previously used as electrical Resistor material used. In conjunction with the heat treatment, it causes the specified values of the thermal delay or increase in the switching amplitude.

Besonders vorteilhaft ist der Temperaturschalter bei einem Strahlungsheizelement mit wenigstens einem Hochtemperatur-­Strahlheizkörper, beispielsweise einem von einem Lampenkol­ben umschlossenen Heizwiderstand, einsetzbar. Durch sein schnelles Ansprechen könnte die Schaltamplitude anderenfalls sehr klein werden und damit eine erhöhte Schalthäufigkeit zur Folge haben, die, vor allem auch wegen der hohen Anlauf­ströme derartiger Hochtemperatur-Strahlungsheizkörper unzu­lässig wäre. Die temporäre Ansprechverzögerungswirkung kann so bemessen sein, daß sie eine kurzzeitige Anfangsüberhit­zung der Glaskeramikplatte zuläßt, die wegen ihrer Kurzzei­tigkeit keine Schädigung auslöst, sie kann aber auch gerin­ger bemessen sein, so daß sie die aufgrund der höheren Masse der Glaskeramikplatte ohnehin vorhandene Verzögerung der Aufheizung der Glaskeramikplatte kompensiert.The temperature switch can be used particularly advantageously in the case of a radiant heating element having at least one high-temperature radiant heater, for example a heating resistor enclosed by a lamp bulb. Because of its fast response, the switching amplitude could otherwise become very small and thus result in an increased switching frequency, which would be impermissible, above all because of the high starting currents of such high-temperature radiant heaters. The temporary response delay effect can be dimensioned such that it allows a brief initial overheating of the glass ceramic plate, which due to its short duration does not cause any damage, but it can also be dimensioned so that it delays the heating of the glass ceramic plate, which is present anyway due to the higher mass of the glass ceramic plate compensated.

Weitere Vorteile und Merkmale der Erfindung gehen auch aus den Unteransprüchen und der nachfolgenden Beschreibung im Zusammenhang mit den Zeichnungen hervor. Diese Merkmale kön­ nen sowohl einzeln als auch in Unterkombinationen miteinan­der vorteilhafte Ausführungen der Erfindung bilden und auch auf anderen Gebieten als den angegebenen einsetzbar sein.

  • Anhand der einzigen Zeichnungsfigur, die einen schema­tischen Längsschnitt durch ein Ausführungsbeispiel der Erfindung, d.h. einen Temperaturschalter zeigt, wird die Erfindung nachstehend erläutert.
Further advantages and features of the invention also emerge from the subclaims and the following description in connection with the drawings. These characteristics can NEN individually as well as in subcombinations form advantageous embodiments of the invention and can also be used in fields other than those specified.
  • The invention is explained below on the basis of the single drawing figure, which shows a schematic longitudinal section through an exemplary embodiment of the invention, ie a temperature switch.

Die Zeichnung zeigt in schematischer Darstellung einen Strahlheizkörper 11, der unterhalb einer Glaskeramikplatte 12 angeordnet ist und diese beheizt. In einer Trägerschale 33 liegt eine Isolation 42. Heizwiderstände 13 oder 14 sind in Form einer in die Isolation 42 teilweise eingebetteten Heizwendel 13 und in Form eines Hochtemperatur-Strahlheiz­körpers 14 vorgesehen, bei dem es sich beispielsweise um eine Halogenlampe handelt, deren Heizwendel 15 aus Wolfram oder ähnlichen Materialien in einem Quarz-Lampenkörper 16 enthalten ist und die aufgrund von Temperaturen oberhalb 1500 K ein Abstrahlungsspektrum weitgehend im sichtbaren Bereich hat.The drawing shows a schematic representation of a radiant heater 11, which is arranged below a glass ceramic plate 12 and heats it. In a carrier shell 33 there is insulation 42. Heating resistors 13 or 14 are provided in the form of a heating coil 13 partially embedded in the insulation 42 and in the form of a high-temperature radiant heater 14, which is, for example, a halogen lamp, the heating coil 15 of which is made of tungsten or similar materials is contained in a quartz lamp body 16 and, due to temperatures above 1500 K, has a radiation spectrum largely in the visible range.

Durch bis zur Glaskeramikplatte 12 reichende Ränder 17 der Isolierung 12 ragt ein Temperaturfühler 20 eines Temperatur­schalters 21 hindurch, der zwischen der Glaskeramikplatte 12 und den Heizkörpern 13, 14 quer über den Strahlheizkörper ragt.A temperature sensor 20 of a temperature switch 21 projects through edges 17 of the insulation 12 reaching as far as the glass ceramic plate 12 and projects between the glass ceramic plate 12 and the radiators 13, 14 across the radiant heater.

Bei dem Temperaturschalter 21 handelt es sich um einen fest eingestellten, jedoch justierbaren Temperaturbegrenzer, des­sen als Schnappschalter 22 angedeutetes Schaltwerk die Heiz­körper 13 und/oder 14 abschaltet oder in anderer Weise ihre Leistung mindert, wenn die Begrenzungstemperatur erreicht ist. Der Temperaturschalter 21 kann noch ein zweites, auf eine andere Temperatur einjustiertes Schaltwerk besitzen, das beispielsweise zur Anzeige des Heißzustandes der Glas­keramikplatte verwendet werden kann.The temperature switch 21 is a fixed, but adjustable temperature limiter, the switching mechanism indicated as a snap switch 22 switches off the radiators 13 and / or 14 or in another way reduces their output when the limiting temperature is reached. The temperature switch 21 can also open a second one have a different temperature-adjusted switching mechanism that can be used, for example, to display the hot state of the glass ceramic plate.

Das Schaltwerk 22 und ggf. das weitere Schaltwerk wird durch einen Ausdehnungsstab 24 betätigt. Er ist in einem Rohr 25 angeordnet, das aus einem Material besteht, das gegenüber dem Ausdehnungsstab 24 einen wesentlich geringeren thermi­schen Ausdehnungskoeffizienten hat.The switching mechanism 22 and possibly the further switching mechanism are actuated by an expansion rod 24. It is arranged in a tube 25, which consists of a material that has a substantially lower coefficient of thermal expansion than the expansion rod 24.

Der Ausdehnungsstab 24 ist durch eine an einem verdickten Kopf 30 des Ausdehnungsstabes 24 angreifende Feder 26 im außerhalb des beheizten Bereiches des Strahlheizkörpers lie­genden Schalterkopf 27 des Temperaturschalters 21 in Rich­tung auf den Schnappschalter hin belastet, so daß er eine an seinem freien Ende auf einem Gewinde 28 angeordnete Justier­mutter 29 gegen das Ende des Rohres 25 und damit das Rohr auch gegen den Schalterkopf zieht. Diese sog. Zugstab-Anord­nung, bei der der Zugstab das thermisch aktive Teil ist, ermöglicht eine relativ einfache Montage, weil der Tempera­turfühler durch die Feder selbst in kraftschlüssiger Anlage gehalten wird und trotz einiger Flexibilität der Anbringung die Justiergenauigkeit nicht leidet.The expansion rod 24 is loaded by a spring 26 engaging a thickened head 30 of the expansion rod 24 in the switch head 27 of the temperature switch 21 lying outside the heated area of the radiant heater in the direction of the snap switch, so that it has one at its free end on a thread 28 arranged adjusting nut 29 against the end of the tube 25 and thus the tube also pulls against the switch head. This so-called tension rod arrangement, in which the tension rod is the thermally active part, enables a relatively simple assembly because the temperature sensor is held in a force-fitting manner by the spring itself and, despite some flexibility in the attachment, the adjustment accuracy does not suffer.

Der Ausdehnungsstab 24 besteht aus einer Chrom-Eisen-Alumi­nium-Legierung, die vorzugsweise ca. 22 % Chrom und 5 % Alu­minium enthält und die von der Firma AB Kanthal, Schweden, unter der Bezeichnung Kanthal A bzw. Al bzw. AF als Heizlei­ter-Legierung hergestellt wird. Der aus diesem Material her­gestellte Stab wird, nachdem er mit einem Kopf 30 für den Angriff der Feder 26 und dem Gewinde 28 versehen ist, einer Voralterung in einer Temperatur oberhalb 800 °C, vorzugswei­se bei ca. 1200 °C in normaler Atmosphäre unterzogen. Da­durch wird auch die durch die mechanische Umformung entste­hende Spannung abgebaut. Dadurch wird die Schaltamplitude überraschenderweise um etwa ± 3 K erhöht.The expansion rod 24 consists of a chromium-iron-aluminum alloy, which preferably contains approximately 22% chromium and 5% aluminum and which is manufactured by AB Kanthal, Sweden, under the name Kanthal A or Al or AF as a heating conductor. Alloy is produced. The rod made of this material, after being provided with a head 30 for the engagement of the spring 26 and the thread 28, is subjected to a pre-aging in a temperature above 800 ° C, preferably at about 1200 ° C in a normal atmosphere. This also reduces the stress caused by the mechanical deformation. This surprisingly increases the switching amplitude by approximately ± 3 K.

Das gegenüber dem Ausdehnungsstab-Material 24 geringer ther­misch dehnende Rohr 25, das als Vergleichsnormal für den Ausdehnungsstab dient, besteht vorteilhaft aus einem haupt­sächlich strahlungsabsorbierenden Material. Das bedeutet, daß es Strahlung praktisch nicht durchläßt, andererseits aber auch in größtem Umfang absorbiert und nicht reflek­tiert. Vorteilhaft konnte ein Material aus Keramik, insbe­sondere Cordierit KER 410, eingesetzt werden. Cordierit ist ein Mischkristall aus den Oxiden der Stoffe Magnesium, Alu­minium und Silicium (2 MgO x 2 Al₂O₃ x 5 SiO₂). Die Keramik KER 410 wird aus tonsubstanz-magnesiumsilicat-haltigen Mas­sen bei Temperaturen um 1400 °C gebrannt und besitzt als Hauptbestandteil das Mineral Cordierit. Es kann auch über die Schmelzphase und spätere Kristallisations-Behandlung hergestellt werden (vgl. D.M. Müller, "Sintered Cordierite Glass-Ceramic Bodies", Corning N.Y., US-PS 3 926 648). Bei Cordierit handelt es sich um ein durchgesintertes Material, das hauptsächlich strahlungsabsorbierend ist.The pipe 25, which is less thermally expanding than the expansion rod material 24 and serves as a standard for the comparison of the expansion rod, advantageously consists of a mainly radiation-absorbing material. This means that it practically does not let radiation through, but on the other hand it also absorbs to a large extent and does not reflect. A ceramic material, in particular Cordierit KER 410, could be used to advantage. Cordierite is a mixed crystal made from the oxides of magnesium, aluminum and silicon (2 MgO x 2 Al₂O₃ x 5 SiO₂). The ceramic KER 410 is fired from masses containing clay substance-magnesium silicate at temperatures around 1400 ° C and has as its main component the mineral cordierite. It can also be made via the melt phase and subsequent crystallization treatment (see D.M. Müller, "Sintered Cordierite Glass-Ceramic Bodies", Corning N.Y., U.S. Patent 3,926,648). Cordierite is a sintered material that is mainly radiation absorbing.

Ferner wurde als geeignetes Material ein Rohr 25 aus Glas­keramik verwendet, beispielsweise vom Typ Ceran 85573. Die­ses Material ist eine Glaskeramik mit niedriger Transmission und hoher Strahlungsabsorption, die durch eine Metalloxid-­Beimischung erreicht wird.A tube 25 made of glass ceramic, for example of the Ceran 85573 type, was also used as a suitable material. This material is a glass ceramic with low transmission and high radiation absorption, which is achieved by adding a metal oxide.

Ferner wurde mit Erfolg ein Rohr 25 aus undurchsichtigem Quarzgut untersucht, beispielsweise aus dem Material 'Roto­sil' der Firma Heraeus. Auch hier ist die Strahlungsundurch­lässigkeit und Absorptionsfähigkeit durch eine Beimischung von Metalloxiden erreicht worden.Furthermore, a tube 25 made of opaque quartz was successfully examined, for example from the material 'Rotosil' from Heraeus. Here, too, the impermeability to radiation and absorption capacity were achieved by adding metal oxides.

In allen Fällen war es möglich, eine jeweils den Anforderun­gen entsprechende mehr oder weniger große thermische Verzö­gerung und Schaltamplitudenverzögerung zu erreichen. Insbe­sondere bei der Verwendung von Hochtemperatur-Strahlungs­heizkörpern 14 war diese Verzögerung, was auch den Anforde­ rungen der Praxis entspricht, größer, so daß beim ersten Ansprechen bei vorher kaltem Temperaturfühler die Abschal­tung später erfolgt als beim nachfolgenden Dauerbetrieb. Vor allem wurde auch die Schalthysterese bzw. -amplitude vergrö­ßert, ohne die Ansprechempfindlichkeit im übrigen zu beein­trächtigen. Die Schaltamplitude sollte etwa in der Größen­ordnung zwischen 4 und 10 K (bevorzugt 5 bis 7 K) liegen, um eine Schalthäufigkeit zu erreichen, die unter 5 Schaltungen pro Minute liegt. Anderenfalls könnte die durch jeweilige örtliche Bestimmungen festgelegte Maximalzahl von Schaltun­gen pro Minute (wegen Netz- bzw. Funkstörungen) überschrit­ten werden. In diesem Zusammenhang wirkt die strahlungsab­sorbierende Ausbildung des Rohres 25 besonders dann vorteil­haft, wenn die thermische Masse vergrößert wird. Dies kann dadurch geschehen, daß die bisher übliche Wandstärke für derartige Rohre von 1 mm wesentlich überschritten wird und vorzugsweise bis 3 mm gewählt wird. Auch ein Vorsehen ande­rer wärmespeichernder Mittel am Rohr wäre möglich. Es ist auch denkbar, die strahlungsabsorbierenden Eigenschaften in einer Oberflächenbeschichtung vorzusehen, während das Rohr wärmespeichernde Eigenschaften aufweist. Durch die Verwen­dung eines Rohrmaterials mit geringer thermischer Leitfähig­keit kann die Wärmeabgabe vom Rohr an den Ausdehnungsstab behindert werden, was auch durch zwischengeschaltete Isola­tionsmaßnahmen erreichbar wäre.In all cases, it was possible to achieve a more or less large thermal delay and switching amplitude delay that corresponded to the requirements. Especially when using high temperature radiant heaters 14 this delay was what the requirement stations corresponds to practice, larger, so that the first response with a previously cold temperature sensor, the shutdown takes place later than in subsequent continuous operation. Above all, the switching hysteresis or amplitude has been increased without affecting the responsiveness. The switching amplitude should be of the order of magnitude between 4 and 10 K (preferably 5 to 7 K) in order to achieve a switching frequency that is less than 5 switching operations per minute. Otherwise, the maximum number of operations per minute specified by local regulations (due to network or radio interference) could be exceeded. In this context, the radiation-absorbing design of the tube 25 is particularly advantageous when the thermal mass is increased. This can be done by substantially exceeding the usual wall thickness of 1 mm for pipes of this type and preferably up to 3 mm. It would also be possible to provide other heat-storing means on the pipe. It is also conceivable to provide the radiation-absorbing properties in a surface coating, while the tube has heat-storing properties. By using a pipe material with low thermal conductivity, the heat transfer from the pipe to the expansion rod can be hindered, which would also be achievable through intermediate insulation measures.

Vorzugsweise ist das am Rohr verwendete strahlungsabsorbie­rende Material im gesamten für die Strahlungs-Beheizung we­sentlichen Wellenlängenbereich strahlungsabsorbierend, ins­besondere in dem Bereich, der von der jeweiligen Strahlungs­quelle direkt herrührt, so daß das Ansprechverhalten haupt­sächlich von der Beheizung und nicht von Sekundärstrahlern, z.B. der Glaskeramikplatte, bestimmt wird. Diese Charakteri­stik ist bei den beschriebenen Materialien gewährleistet, ist aber auch mit anderen Materialien zu erreichen.The radiation-absorbing material used on the tube is preferably radiation-absorbing in the entire wavelength range which is essential for the radiation heating, in particular in the area which comes directly from the respective radiation source, so that the response behavior is mainly from the heating and not from secondary radiators, e.g. the glass ceramic plate. This characteristic is guaranteed for the materials described, but can also be achieved with other materials.

Claims (12)

1. Temperaturschalter für eine eine Strahlungsquelle ent­haltende Strahlungsheizung, mit wenigstens einem Schaltkontakt (22) und einem Temperaturfühler (20), der aus einem Ausdehnungsstab (24) aus einem Material mit höherem und einem diesen umgebenden Rohr (25) aus einem Material mit einem demgegenüber geringerem thermischen Ausdehnungskoeffizienten besteht und Mittel zur temporären, insbesondere bei Strahlung wirksamen An­sprechverzögerung des Temperaturschalters (21) auf­weist.1. Temperature switch for a radiation heater containing a radiation source, with at least one switch contact (22) and a temperature sensor (20), which consists of an expansion rod (24) made of a material with a higher and a surrounding tube (25) made of a material with a There is a lower coefficient of thermal expansion and has means for a temporary response delay of the temperature switch (21), which is particularly effective in the case of radiation. 2. Temperaturschalter nach Anspruch 1, dadurch gekenn­zeichnet, daß das Rohr (25) zumindest teilweise ein strahlungsabsorbierendes Material aufweist, das die von der Strahlungsquelle (13, 14) kommende Strahlung haupt­sächlich absorbiert, und/oder vorzugsweise ganz aus dem strahlungsabsorbierenden Material besteht.2. Temperature switch according to claim 1, characterized in that the tube (25) at least partially has a radiation-absorbing material which the the radiation source (13, 14) mainly absorbs radiation and / or preferably consists entirely of the radiation-absorbing material. 3. Temperaturschalter nach einem der vorhergehenden An­sprüche, dadurch gekennzeichnet, daß das Rohr (25) eine erhöhte thermische Trägheit und/oder eine geringe ther­mische Leitfähigkeit aufweist.3. Temperature switch according to one of the preceding claims, characterized in that the tube (25) has an increased thermal inertia and / or a low thermal conductivity. 4. Temperaturschalter nach einem der vorhergehenden An­sprüche, dadurch gekennzeichnet, daß das Rohr (25) aus einem durchgesinterten keramischen Material, vorzugs­weise aus Cordierit besteht.4. Temperature switch according to one of the preceding claims, characterized in that the tube (25) consists of a sintered ceramic material, preferably of cordierite. 5. Temperaturschalter nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß das Rohr (25) aus Glaskera­mik, insbesondere einer Glaskeramik mit geringen Trans­missions-Eigenschaften besteht.5. Temperature switch according to one of claims 1 to 3, characterized in that the tube (25) consists of glass ceramic, in particular a glass ceramic with low transmission properties. 6. Temperaturschalter nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß das Rohr (25) aus einem strahlungsabsorbierenden, nichttransmissivem Quarzgut besteht.6. Temperature switch according to one of claims 1 to 3, characterized in that the tube (25) consists of a radiation-absorbing, non-transmissive quartz material. 7. Temperaturschalter nach einem der vorhergehenden An­sprüche, dadurch gekennzeichnet, daß das Rohrmaterial eine Metalloxid-Beimischung enthält.7. Temperature switch according to one of the preceding claims, characterized in that the tube material contains a metal oxide admixture. 8. Temperaturschalter nach einem der vorhergehenden An­sprüche, dadurch gekennzeichnet, daß das strahlungsab­sorbierende Material einen zumindest den von der Strah­lungsquelle (13, 14) direkt herrührenden Wellenlängsbe­reich umfassenden Absorptionsbereich aufweist.8. Temperature switch according to one of the preceding claims, characterized in that the radiation-absorbing material has at least one of the radiation source (13, 14) directly originating wavelength region comprising the absorption region. 9. Temperaturschalter, insbesondere nach einem der vorher­gehenden Ansprüche, dadurch gekennzeichnet, daß der Ausdehnungsstab (24) zumindest teilweise aus einer Chrom-Eisen-Aluminium-Legierung besteht, die bei einer Temperatur oberhalb 800 °C (ca. 1100 K), vorzugsweise oberhalb 1100 °C (ca. 1400 K) wärmebehandelt ist.9. Temperature switch, in particular according to one of the preceding claims, characterized in that the expansion rod (24) consists at least partially of a chromium-iron-aluminum alloy, which at a temperature above 800 ° C (about 1100 K), preferably above 1100 ° C (approx. 1400 K) is heat treated. 10. Temperaturschalter nach Anspruch 9, dadurch gekenn­zeichnet, daß die Chrom-Eisen-Aluminium-Legierung ca. 22 % Chrom und ca. 5% Aluminium enthält.10. Temperature switch according to claim 9, characterized in that the chromium-iron-aluminum alloy contains approximately 22% chromium and approximately 5% aluminum. 11. Temperaturschalter nach einem der vorhergehenden An­sprüche, dadurch gekennzeichnet, daß der Ausdehnungs­stab (24) federnd auf Zug belastet ist und durch eine justierbare Verbindung (28, 29) an seinem vom Schalt­kontakt (22) entfernten Ende mit dem Rohr (25) verbun­den ist.11. Temperature switch according to one of the preceding claims, characterized in that the expansion rod (24) is resiliently loaded on train and is connected to the tube (25) by an adjustable connection (28, 29) at its end remote from the switching contact (22) . 12. Temperaturschalter nach einem der vorhergehenden An­sprüche, dadurch gekennzeichnet, daß er fest auf eine Begrenzungstemperatur eingestellt ist, wobei ein zwei­ter, eine Heißanzeige für eine Kochstelle betätigender Signalkontakt vorgesehen ist und/oder in einem Strah­lungs-Heizelement (11) mit wenigstens einem Hochtempe­ratur-Strahlheizkörper (14) wie einem von einem Lampen­kolben (16) umschlossenen Heizwider stand (15) vorgese­hen ist.12. Temperature switch according to one of the preceding claims, characterized in that it is permanently set to a limiting temperature, wherein a second, a hot display for a hotplate actuating signal contact is provided and / or in a radiation heating element (11) with at least one high-temperature Radiant heater (14) as a stand by a lamp bulb (16) enclosed heating resistor (15) is provided.
EP89110509A 1988-06-25 1989-06-10 Thermal switch Revoked EP0348716B1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DE3821495 1988-06-25
DE3821496 1988-06-25
DE19883821496 DE3821496A1 (en) 1988-06-25 1988-06-25 Temperature switch
DE19883821495 DE3821495A1 (en) 1988-06-25 1988-06-25 Temperature switch

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EP0348716A2 true EP0348716A2 (en) 1990-01-03
EP0348716A3 EP0348716A3 (en) 1991-04-03
EP0348716B1 EP0348716B1 (en) 1995-02-01

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EP89110509A Revoked EP0348716B1 (en) 1988-06-25 1989-06-10 Thermal switch

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US (1) US5055819A (en)
EP (1) EP0348716B1 (en)
AT (1) ATE118144T1 (en)
DE (1) DE58908957D1 (en)
ES (1) ES2066805T3 (en)

Cited By (1)

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Publication number Priority date Publication date Assignee Title
EP0416335A1 (en) * 1989-09-08 1991-03-13 E.G.O. Elektro-Geräte Blanc und Fischer GmbH &amp; Co. KG Temperature switch

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US5256860A (en) * 1993-01-22 1993-10-26 Therm-O-Disc, Incorporated Control for glass cooktops utilizing rod-shaped thermistor
IT240975Y1 (en) * 1996-10-25 2001-04-20 Whirpool Europ S R L TEMPERATURE AND SAFETY CONTROL DEVICE ASSOCIATED WITH A HEATING ELEMENT OF A GLASS-CERAMIC HOB
DE19846513A1 (en) * 1998-10-09 2000-04-13 Ego Elektro Geraetebau Gmbh Switching device for an electrical heating device
ATE371256T1 (en) * 2001-01-10 2007-09-15 Electrovac TEMPERATURE LIMITER
AT409680B (en) * 2001-04-17 2002-10-25 Electrovac Temperature
DE102018213625A1 (en) * 2018-08-13 2020-02-13 Siemens Aktiengesellschaft Switchgear temperature measurement

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US3926648A (en) * 1974-06-07 1975-12-16 Corning Glass Works Sintered cordierite glass-ceramic bodies
DE2839161A1 (en) * 1978-09-08 1980-03-20 Ego Regeltech Temp. limiter for vitreous ceramic cooking utensil - has main power switch and second switch warning against touching heated surface
DE3440156A1 (en) * 1983-11-04 1985-05-15 Electrovac DEVICE FOR CONTROLLING OR LIMITATION OF AT LEAST ONE TEMPERATURE VALUE OR A TEMPERATURE RANGE OF RADIATION OR CONTACT HEATER FROM ELECTRICAL COOKING EQUIPMENT
GB2192279A (en) * 1983-09-10 1988-01-06 Micropore International Ltd Thermal cut-out devices for radiant heaters
DE3817113A1 (en) * 1988-05-19 1989-11-30 Ego Elektro Blanc & Fischer Radiating heater

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GB8324271D0 (en) * 1983-09-10 1983-10-12 Micropore International Ltd Thermal cut-out device
IE55689B1 (en) * 1983-12-01 1990-12-19 Thorn Emi Patents Ltd Thermal limiter
EP0176027B1 (en) * 1984-09-22 1989-02-01 E.G.O. Elektro-Geräte Blanc u. Fischer Radiative heating body for a cooking apparatus

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US3926648A (en) * 1974-06-07 1975-12-16 Corning Glass Works Sintered cordierite glass-ceramic bodies
DE2839161A1 (en) * 1978-09-08 1980-03-20 Ego Regeltech Temp. limiter for vitreous ceramic cooking utensil - has main power switch and second switch warning against touching heated surface
GB2192279A (en) * 1983-09-10 1988-01-06 Micropore International Ltd Thermal cut-out devices for radiant heaters
DE3440156A1 (en) * 1983-11-04 1985-05-15 Electrovac DEVICE FOR CONTROLLING OR LIMITATION OF AT LEAST ONE TEMPERATURE VALUE OR A TEMPERATURE RANGE OF RADIATION OR CONTACT HEATER FROM ELECTRICAL COOKING EQUIPMENT
DE3817113A1 (en) * 1988-05-19 1989-11-30 Ego Elektro Blanc & Fischer Radiating heater

Cited By (2)

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EP0416335A1 (en) * 1989-09-08 1991-03-13 E.G.O. Elektro-Geräte Blanc und Fischer GmbH &amp; Co. KG Temperature switch
US5113170A (en) * 1989-09-08 1992-05-12 E.G.O. Elektro-Gerate Blanc U. Fischer Temperature switch

Also Published As

Publication number Publication date
EP0348716A3 (en) 1991-04-03
DE58908957D1 (en) 1995-03-16
EP0348716B1 (en) 1995-02-01
US5055819A (en) 1991-10-08
ES2066805T3 (en) 1995-03-16
ATE118144T1 (en) 1995-02-15

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