EP0025946B1 - Heating element for indirectly heated cathode - Google Patents

Heating element for indirectly heated cathode Download PDF

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Publication number
EP0025946B1
EP0025946B1 EP80105443A EP80105443A EP0025946B1 EP 0025946 B1 EP0025946 B1 EP 0025946B1 EP 80105443 A EP80105443 A EP 80105443A EP 80105443 A EP80105443 A EP 80105443A EP 0025946 B1 EP0025946 B1 EP 0025946B1
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EP
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Prior art keywords
heating element
cap
heating
adjacent
distant
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EP80105443A
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German (de)
French (fr)
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EP0025946A1 (en
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Eberhard Weiss
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Nokia Deutschland GmbH
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International Standard Electric Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/13—Solid thermionic cathodes
    • H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
    • H01J1/22—Heaters

Definitions

  • the invention relates to a heating element for an indirectly heated cathode, which is inserted into a cathode tube, which is closed with a cap carrying the emitting layer, and which consists of a heating wire coil covered with an insulating layer, part of the heating element being adjacent to the cap and the other being further away from it is.
  • heating elements are known (DE-A 1564 462).
  • the part of the heating wire helix adjacent to the cap can either be M-shaped or a double helix.
  • Cathodes with a shorter heating time are also known (DE-A 2313911).
  • a cathode consisting of a cathode tube sealed with a cap carrying the emitting layer, into which a heating coil (heating element) covered with an insulating layer is inserted
  • various measures have been taken to reduce the heating-up time. These measures aim in particular to achieve a temperature distribution which has its maximum value on the cathode cap, which decreases with increasing distance from the cathode cap.
  • the user requests that a picture be obtained shortly after the device is switched on. This means that the cathode of the picture tube has to be heated up very quickly.
  • the object on which the invention is based is therefore to create a rapid heating cathode in which the heating element enclosed by the cathode tube and the cathode cap is designed in such a way that it generates as much heat as possible as quickly as possible during a short period of time in the heating phase.
  • the part of the heating element adjacent to the cap has a smaller heat capacity per unit length than the part farther away, the part adjacent to the cap consisting of at least two partial areas, between which at least one removed part with a larger heat capacity per unit length is arranged.
  • heating wire coil of the heating element runs more densely in the part adjacent to the cap than in the part further away, the part adjacent to the cap consisting of at least two partial regions, between which at least one part farther away with less density Heating wire coil is arranged.
  • the part adjacent to the cathode cap heats up very quickly for a short time (e.g. for 1-2 seconds) and has an excessive temperature during this time.
  • a short time e.g. for 1-2 seconds
  • the reason for this is that the part adjacent to the cap experiences a brief overheating because the tungsten wire of the heating element has a 1.2 to 1.5 times higher resistance during the sudden heating than in the operating state about 10 seconds later.
  • the heating output during this period is about 1.5 times higher than a few seconds later.
  • heating elements according to the invention practically do not differ in their electrical connection values and in their external mechanical dimensions from known heating elements, they can be exchanged for known heating elements without any change in the cathode and heating element fastening means. To produce heating elements according to the invention, however, no new devices are required, but only minor changes in the process sequence.
  • FIG. 1 a shows a front view and FIG. 1 b a side view of an embodiment of the heating element 1 according to the invention, which is inserted into a cathode tube 3 closed with a cap 2.
  • the part of the heating element 1 which is adjacent to the cap 2 is designated by 4, the part located at a distance by 5 B and 5 z .
  • the type of heating element shown is a so-called M-heating element. It consists of the tongue and the legs of the M. Therefore, the more distant part of the filament was designated 5 z and 5 B.
  • the invention is applicable regardless of the type of heating element used. It is only essential that the heating element has a length such that part of the heating element is adjacent to the cathode cap and another part of the heating element is further removed.
  • the invention can therefore also be implemented on a heating element designed as a double spiral.
  • the heating elements consist of filaments that are covered with an insulating layer.
  • the heating wire coil 6 can only be seen at the points where it is not covered. At these points, the filament is uncoiled so that it can be better attached to heating element fasteners.
  • the insulating layer in the part 4 adjacent to the cap is thinner than in the distant part 5 B , 5 z .
  • the oxide covering has a mass of approximately 0.25 mg / mm heating wire helix length. 1 has a mass of about 0.18 mg / mm in the adjacent part and a mass of about 0.36 mg / mm filament length in the distant part.
  • a known heating element lights up with dark red heat after 2 seconds, which corresponds to a temperature of approx. 600 ° C. After 4 seconds the heating element has reached its final temperature of approx. 850 ° C.
  • the heating element according to the invention already shines with bright red glow in the neighboring part 4 after 2 seconds, since only a small amount of oxide is to be heated here. In the distant part with a stronger oxide covering, that is to say a higher heat capacity, the heating element according to the invention only reaches dark red heat after about 3 seconds.
  • the different heating times of the two parts are determined not only by the different heat capacities but also very significantly by the temperature-dependent electrical resistance of the heating wire coil, usually a tungsten heating wire coil.
  • the specific resistance of the tungsten is 5.5 10-8 Qm at 20 ° C. If the specific resistance is set to one at 20 ° C, it is three at 430 ° C, four at 630 ° C and five at 820 ° C. In a known heating element that reaches about 600 ° C after 2 seconds, the specific resistance is about four times as large as at 20 ° C. In the heating element according to the invention, the resistivity in the colder, distant part is about three times as great as at 20 ° C. in the hotter, neighboring part. The resistance over the entire length of the heating element, and thus the flowing current, is approximately the same in both cases. The heating power is calculated from the product of the resistance and the square of the current. Since the current remains almost unchanged, but the resistance in the adjacent part of the heating element according to the invention is higher than in the known heating element, the heating power in the heating element according to the invention is also greater in the adjacent part.
  • the different heat capacities can also be achieved by applying a porous oxide layer in the adjacent part and a compact oxide layer in the distant part.
  • FIG. 2 shows another embodiment of the heating element 7.
  • the oxide layer covering the heating wire coil 6 is only indicated by dashed lines here.
  • the heating wire coil is only slightly coiled in the distant part 8 B , 8 z of the heating element, but tightly coiled in the adjacent part 9.
  • the indices B and Z have the same meaning as explained in the description of FIG. 1.
  • the heat effects are very similar to those explained in the description of FIG. 1. Because of the tight winding in the neighboring part, it heats up faster than the distant part that is further away. Due to the faster warming, the resistance rises sharply, which further supports the warming.
  • the total wire length is again chosen so that the same current results for the same heating voltage for a known heating element and the heating element according to the invention. After the temperature differences have been equalized, there is hardly any difference in the temperature distribution between a heating element according to the invention and a known heating element. The rapid heating of the adjacent part, however, considerably reduces the heating time of the cathode. While 90% of the cathode current that is reached in thermal equilibrium flows after about 4.5 seconds in known heating elements, this is reached after about 3.5 seconds in the heating element according to the invention.
  • Inventive heating elements may be prepared as follows: A in M-shape or egg - ner other selected curved shape heating coil is immersed in an electrophoresis bath, are deposited to about 0.18 mg / mm of oxide.
  • the filament is then pulled out of the electrophoresis bath and immersed in a washing bath to such an extent that the oxide covering is washed off in the adjacent part.
  • the heating wire coil is immersed again in the electrophoresis bath and 0.18 mg / mm oxide are deposited again. Further treatment is carried out as usual. This method gives the adjacent part a thin and the distant part of the heating element a thick oxide layer
  • the method can be modified insofar as the voltage is increased so much on the second immersion in the electrophoresis bath that electrolysis occurs at the same time.
  • the second oxide layer becomes porous and thus has an even lower heat capacity than the compactly applied layer.
  • a heating element according to FIG. 2 with a heating wire coil with different densities can be produced, as will be described with the aid of FIG. 3.
  • a tungsten wire is wound from molybdenum of 0.175 mm diameter, with 42 turns / cm over 7.2 mm length in part 8 z and 4.1 mm length in part 8 3 , as well as with 90 turns / cm each with 4, 2 mm length in part 9.
  • the core wire with the coiled heating wire is etched out in an acid bath as usual. Covering with an oxide layer can be done in a conventional manner or as described in the previous paragraphs.
  • the length of the heating element in the adjacent part is approximately one third of the total length.

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  • Resistance Heating (AREA)
  • Solid Thermionic Cathode (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)

Description

Die Erfindung betrifft ein Heizelement für eine indirekt geheizte Kathode, welches in ein mit einer die emittierende Schicht tragenden Kappe abgeschlossenes Kathodenrohr eingeschoben ist und aus einer mit einer Isolierschicht bedeckten Heizdrahtwendel besteht, wobei ein Teil des Heizelements der Kappe benachbart und der andere von dieser weiter entfernt ist.The invention relates to a heating element for an indirectly heated cathode, which is inserted into a cathode tube, which is closed with a cap carrying the emitting layer, and which consists of a heating wire coil covered with an insulating layer, part of the heating element being adjacent to the cap and the other being further away from it is.

Derartige Heizelemente sind bekannt (DE-A 1564 462). Bei den bekannten Heizelementen kann der der Kappe benachbarte Teil der Heizdrahtwendel entweder M-förmig oder als Doppelwendel ausgebildet sein.Such heating elements are known (DE-A 1564 462). In the known heating elements, the part of the heating wire helix adjacent to the cap can either be M-shaped or a double helix.

Es sind auch Kathoden mit verkürzter Aufheizzeit bekannt (DE-A 2313911). Bei einer solchen Kathode, bestehend aus einem mit einer die emittierende Schicht tragenden Kappe abgeschlossenen Kathodenrohr, in das eine mit einer Isolierschicht bedeckte Heizwendel (Heizelement) eingeschoben ist, sind verschiedene Massnahmen ergriffen, um die Aufheizzeit abzusenken. Diese Massnahmen zielen insbesondere dahin, eine Temperaturverteilung zu erzielen, die ihren Maximalwert an der Kathodenkappe hat, der mit zunehmendem Abstand von der Kathodenkappe abnimmt.Cathodes with a shorter heating time are also known (DE-A 2313911). With such a cathode, consisting of a cathode tube sealed with a cap carrying the emitting layer, into which a heating coil (heating element) covered with an insulating layer is inserted, various measures have been taken to reduce the heating-up time. These measures aim in particular to achieve a temperature distribution which has its maximum value on the cathode cap, which decreases with increasing distance from the cathode cap.

Vor allem bei Fernsehgeräten verlangt der Benutzer, schon kurz nach dem Einschalten des Gerätes ein Bild zu erhalten. Dies bedeutet, dass die Kathode der Bildröhre sehr schnell aufgeheizt werden muss.In the case of television sets in particular, the user requests that a picture be obtained shortly after the device is switched on. This means that the cathode of the picture tube has to be heated up very quickly.

Die der Erfindung zugrundeliegende Aufgabe besteht deshalb darin, eine Schnellheizkathode zu schaffen, bei der das vom Kathodenrohr und der Kathodenkappe umschlossene Heizelement derart ausgebildet ist, dass es während einer kurzen Zeitspanne in der Anheizphase möglichst schnell möglichst viel Wärme erzeugt.The object on which the invention is based is therefore to create a rapid heating cathode in which the heating element enclosed by the cathode tube and the cathode cap is designed in such a way that it generates as much heat as possible as quickly as possible during a short period of time in the heating phase.

Diese Aufgabe ist erfindungsgemäss dadurch gelöst, dass der der Kappe benachbarte Teil des Heizelementes eine kleinere Wärmekapazität je Längeneinheit aufweist als der weiter entfernte Teil, wobei der der Kappe benachbarte Teil aus wenigstens zwei Teilbereichen besteht, zwischen denen wenigstens ein entfernter Teil mit grösserer Wärmekapazität je Längeneinheit angeordnet ist.This object is achieved according to the invention in that the part of the heating element adjacent to the cap has a smaller heat capacity per unit length than the part farther away, the part adjacent to the cap consisting of at least two partial areas, between which at least one removed part with a larger heat capacity per unit length is arranged.

Eine andere Lösung dieser Aufgabe besteht darin, dass die Heizdrahtwendel des Heizelementes in dem der Kappe benachbarten Teil dichter als in dem weiter entfernten Teil verläuft, wobei der der Kappe benachbarte Teil aus wenigstens zwei Teilbereichen besteht, zwischen denen wenigstens ein weiter entfernter Teil mit wenig dichter Heizdrahtwendel angeordnet ist.Another solution to this problem is that the heating wire coil of the heating element runs more densely in the part adjacent to the cap than in the part further away, the part adjacent to the cap consisting of at least two partial regions, between which at least one part farther away with less density Heating wire coil is arranged.

Bei dem neuen Heizelement heizt der der Kathodenkappe benachbarte Teil für eine kurze Zeit (z.B. für 1-2 sec.) stossartig sehr schnell an und weist während dieserZeit eine überhöhte Temperatur auf. Das rührt daher, dass das der Kappe benachbarte Teil eine kurzzeitige Überhitzung erfährt, weil der Wolframdraht des Heizelementes während der stossartigen Erhitzung einen 1,2- bis 1,5fachen höheren Widerstand als im Betriebszustand ca. 10 sec. später besitzt. Somit ist die Heizleistung während dieser Zeitspanne etwa 1,5mal höher als wenige Sekunden später.In the new heating element, the part adjacent to the cathode cap heats up very quickly for a short time (e.g. for 1-2 seconds) and has an excessive temperature during this time. The reason for this is that the part adjacent to the cap experiences a brief overheating because the tungsten wire of the heating element has a 1.2 to 1.5 times higher resistance during the sudden heating than in the operating state about 10 seconds later. The heating output during this period is about 1.5 times higher than a few seconds later.

Der weiter entfernte Teil des Heizers hinkt in seiner Erwärmung, beispielsweise weil auf ihm viel zu erwärmende Masse angeordnet ist, hinter dem der Kappe benachbarten Teil her. Dies gilt in noch erhöhtem Masse für die Enden des Heizelementes, von welchem auch noch Wärme über die Heizerhalter abgeführt wird.The more distant part of the heater limps in its heating, for example because much mass to be heated is arranged on it, behind the part adjacent to the cap. This applies to an even greater extent to the ends of the heating element, from which heat is also dissipated via the heater holder.

Da sich die erfindungsgemässen Heizelemente in ihren elektrischen Anschlusswerten und in ihren äusseren mechanischen Abmessungen praktisch nicht von bekannten Heizelementen unterscheiden, können sie ohne jegliche Änderung von Kathode und Heizelementbefestigungsmitteln gegen bekannte Heizelemente ausgetauscht werden. Zur Herstellung erfindungsgemässer Heizelemente bedarf es aber auch keiner neuen Vorrichtungen sondern nur geringer Änderungen im Verfahrensablauf.Since the heating elements according to the invention practically do not differ in their electrical connection values and in their external mechanical dimensions from known heating elements, they can be exchanged for known heating elements without any change in the cathode and heating element fastening means. To produce heating elements according to the invention, however, no new devices are required, but only minor changes in the process sequence.

Die Erfindung ist nachstehend anhand einiger in den Figuren dargestellter Ausführungsbeispiele erläutert. Es zeigen:

  • Fig. 1a, b: eine Ausführungsform des erfindungsgemässen Heizelements in Front- und Seitenansicht,
  • Fig. 2: eine andere Ausführungsform des erfindungsgemässen Heizelementes und
  • Fig. 3: die Heizdrahtwendel für ein Heizelement gemäss Fig. 2.
The invention is explained below with reference to some exemplary embodiments shown in the figures. Show it:
  • 1a, b: an embodiment of the heating element according to the invention in front and side view,
  • 2: another embodiment of the heating element according to the invention and
  • 3: the heating wire coil for a heating element according to FIG. 2.

Fig. 1a zeigt in Frontansicht und 1b in Seitenansicht eine Ausführungsform des erfindungsgemässen Heizelements 1, welches in ein mit einer Kappe 2 abgeschlossenes Kathodenrohr 3 eingeschoben ist. Der der Kappe 2 benachbarte Teil des Heizelements 1 ist mit 4, der entfernt liegende Teil mit 5B und 5z bezeichnet. Der dargestellte Heizelementtyp ist ein sogenanntes M-Heizelement. Es besteht aus der Zunge und den Beinen des M. Daher wurde der weiter entfernte Teil der Heizdrahtwendel als 5z und 5B bezeichnet.FIG. 1 a shows a front view and FIG. 1 b a side view of an embodiment of the heating element 1 according to the invention, which is inserted into a cathode tube 3 closed with a cap 2. The part of the heating element 1 which is adjacent to the cap 2 is designated by 4, the part located at a distance by 5 B and 5 z . The type of heating element shown is a so-called M-heating element. It consists of the tongue and the legs of the M. Therefore, the more distant part of the filament was designated 5 z and 5 B.

Die Erfindung ist jedoch unabhängig vom verwendeten Heizelementtyp anwendbar. Wesentlich ist nur, dass das Heizelement eine solche Länge aufweist, dass ein Teil des Heizelementes der Kathodenkappe benachbart liegt und ein anderer Teil des Heizelementes wieter entfernt ist. Die Erfindung kann daher auch an einem als Doppelwendel ausgebildeten Heizelement verwirklicht sein.However, the invention is applicable regardless of the type of heating element used. It is only essential that the heating element has a length such that part of the heating element is adjacent to the cathode cap and another part of the heating element is further removed. The invention can therefore also be implemented on a heating element designed as a double spiral.

Die Heizelemente bestehen aus Heizdrahtwendeln, die mit einer Isolierschicht bedeckt sind. In Fig. 1 ist die Heizdrahtwendel 6 nur an den Stellen zu erkennen, an denen sie nicht bedeckt ist. An diesen Stellen ist die Heizdrahtwendel ungewendelt, um sie besser an Heizelementbefestigungsmitteln befestigen zu können.The heating elements consist of filaments that are covered with an insulating layer. In Fig. 1, the heating wire coil 6 can only be seen at the points where it is not covered. At these points, the filament is uncoiled so that it can be better attached to heating element fasteners.

Wie aus Fig. 1 ersichtlich ist, ist die Isolierschicht in dem der Kappe benachbarten Teil 4 dünner als in dem entfernt liegenden Teil 5B, 5z. Damit ist aber die Wärmekapazität im benachbarten Teil kleiner als im entfernt liegenden Teil. Die Wirkung dieser Massnahme wird durch ein Beispiel erklärt.As can be seen from Fig. 1, the insulating layer in the part 4 adjacent to the cap is thinner than in the distant part 5 B , 5 z . However, this means that the heat capacity in the neighboring part is smaller than in the distant part. The The effect of this measure is explained by an example.

Die Oxidbedeckung hat bei bekannten Heizelementen eine Masse von etwa 0,25 mg/mm Heizdrahtwendellänge. Das erfindungsgemässe Heizelement nach Fig. 1 hat dagegen im benachbarten Teil eine Masse von etwa 0,18 mg/mm und im entfernt liegenden Teil eine Masse von etwa 0,36 mg/mm Heizdrahtwendellänge.With known heating elements, the oxide covering has a mass of approximately 0.25 mg / mm heating wire helix length. 1 has a mass of about 0.18 mg / mm in the adjacent part and a mass of about 0.36 mg / mm filament length in the distant part.

Beim Anlegen einer Heizspannung von 7 V leuchtet ein bekanntes Heizelement nach 2 sec mit dunkler Rotglut, die einer Temperatur von ca. 600 °C entspricht. Nach 4 sec hat das Heizelement seine Endtemperatur von ca. 850 °C erreicht. Das erfindungsgemässe Heizelement dagegen leuchtet nach 2 sec in dem benachbarten Teil 4 bereits mit heller Rotglut, da hier nur wenig Oxidbedekkung aufzuheizen ist. Im entfernt liegenden Teil mit stärkerer Oxidbedeckung, also höherer Wärmekapazität, erreicht das erfindungsgemässe Heizelement erst nach ca. 3 sec dunkle Rotglut.When a heating voltage of 7 V is applied, a known heating element lights up with dark red heat after 2 seconds, which corresponds to a temperature of approx. 600 ° C. After 4 seconds the heating element has reached its final temperature of approx. 850 ° C. The heating element according to the invention, on the other hand, already shines with bright red glow in the neighboring part 4 after 2 seconds, since only a small amount of oxide is to be heated here. In the distant part with a stronger oxide covering, that is to say a higher heat capacity, the heating element according to the invention only reaches dark red heat after about 3 seconds.

Die unterschiedlichen Erwärmungszeiten der beiden Teile werden ausser durch die unterschiedlichen Wärmekapazitäten auch ganz wesentlich durch den temperaturabhängigen elektrischen Widerstand der Heizdrahtwendel, in der Regel einer Wolfram-Heizdrahtwendel, bestimmt.The different heating times of the two parts are determined not only by the different heat capacities but also very significantly by the temperature-dependent electrical resistance of the heating wire coil, usually a tungsten heating wire coil.

Der spezifische Widerstand des Wolframs beträgt bei 20°C 5.5 10-8 Qm. Wird der spezifische Widerstand bei 20 °C gleich eins gesetzt, so ist er bei 430°C gleich drei, bei 630°C gleich vier und bei 820 °C gleich fünf. Bei einem bekannten Heizelement, das nach 2 sec etwa 600°C erreicht, ist der spezifische Widerstand etwa viermal so gross wie bei 20°C. Bei dem erfindungsgemässen Heizelement ist im kälteren, entfernt liegenden Teil der spezifische Widerstand etwa dreimal, im heisseren, benachbarten Teil etwa fünfmal so gross wie bei 20°C. Der Widerstand über die gesamte Heizelementlänge, und damit der fliessende Strom, ist in beiden Fällen etwa gleich. Die Heizleistung berechnet sich aber aus dem Produkt des Widerstandes und dem Quadrat des Stromes. Da der Strom nahezu unverändert bleibt, der Widerstand im benachbarten Teil des erfindungsgemässen Heizelementes jedoch höher als bei dem bekannten Heizelement ist, ist auch die Heizleistung beim erfindungsgemässen Heizelement im benachbarten Teil grösser.The specific resistance of the tungsten is 5.5 10-8 Qm at 20 ° C. If the specific resistance is set to one at 20 ° C, it is three at 430 ° C, four at 630 ° C and five at 820 ° C. In a known heating element that reaches about 600 ° C after 2 seconds, the specific resistance is about four times as large as at 20 ° C. In the heating element according to the invention, the resistivity in the colder, distant part is about three times as great as at 20 ° C. in the hotter, neighboring part. The resistance over the entire length of the heating element, and thus the flowing current, is approximately the same in both cases. The heating power is calculated from the product of the resistance and the square of the current. Since the current remains almost unchanged, but the resistance in the adjacent part of the heating element according to the invention is higher than in the known heating element, the heating power in the heating element according to the invention is also greater in the adjacent part.

Geringe Wärmekapazität und hoher elektrischer Widerstand im benachbarten Teil bewirken beim erfindungsgemässen Heizelement, dass in der Aufheizphase der benachbarte TeiI wesentlich schneller heiss wird als beim bekannten Heizelement, ja sogar, dass die Temperatur des benachbarten Teils in der ersten Aufheizphase die sich nach einiger Zeit einstellende Betriebstemperatur zunächst übersteigt. Dies bedingt ein sehr schnelles Aufheizen der Kappe und damit der elektronenemittierenden Schicht der Kathode. Später, wenn das thermische Gleichgewicht erreicht ist, besteht kein Unterschied mehr in der Temperaturverteilung zwischen einem bekannten und einem erfindungsgemässen Heizelement.Low heat capacity and high electrical resistance in the adjacent part in the heating element according to the invention cause the neighboring part to heat up much faster in the heating phase than in the known heating element, and in fact even that the temperature of the adjacent part in the first heating phase becomes the operating temperature that arises after some time initially exceeds. This causes the cap and thus the electron-emitting layer of the cathode to heat up very quickly. Later, when the thermal equilibrium is reached, there is no longer any difference in the temperature distribution between a known and an inventive heating element.

Statt unterschiedlichen Dicken in der Oxidbedeckung können die unterschiedlichen Wärmekapazitäten auch dadurch erzielt werden, dass im benachbarten Teil eine poröse Oxidschicht und im entfernt liegenden Teil eine kompakte Oxidschicht aufgebracht ist.Instead of different thicknesses in the oxide covering, the different heat capacities can also be achieved by applying a porous oxide layer in the adjacent part and a compact oxide layer in the distant part.

Fig. 2 zeigt eine andere Ausführungsform des Heizelements 7. Die die Heizdrahtwendel 6 bedekkende Oxidschicht ist hier nur gestrichelt angedeutet. Wie ersichtlich, ist die Heizdrahtwendel im entfernt liegenden Teil 8B, 8z des Heizelements nur leicht, im benachbarten Teil 9 dagegen dicht gewendelt. Die Indizes B und Z haben die gleiche Bedeutung, wie in der Beschreibung der Fig. 1 erläutert.FIG. 2 shows another embodiment of the heating element 7. The oxide layer covering the heating wire coil 6 is only indicated by dashed lines here. As can be seen, the heating wire coil is only slightly coiled in the distant part 8 B , 8 z of the heating element, but tightly coiled in the adjacent part 9. The indices B and Z have the same meaning as explained in the description of FIG. 1.

Die Wärmeeffekte sind den in der Beschreibung der Fig. 1 erläuterten sehr ähnlich. Wegen der dichten Wendelung im benachbarten Teil erwärmt sich dieser schneller als der entfernt liegende weiter gewendelte Teil. Durch die schnellere Erwärmung steigt der Widerstand stark an, was die Erwärmung noch weiter unterstützt. Die Gesamtdrahtlänge ist wieder so gewählt, dass sich für ein bekanntes und das erfindungsgemässe Heizelement der gleiche Strom bei gleicher Heizspannung ergibt. Nach dem Ausgleich der Temperaturunterschiede besteht im thermischen Gleichgewicht wieder kaum ein Unterschied in der Temperaturverteilung zwischen einem erfindungsgemässen und einem bekannten Heizelement. Durch das schnelle Aufheizen des benachbarten Teils wird jedoch die Aufheizzeit der Kathode erheblich verkürzt. Während bei bekannten Heizelementen nach ca. 4,5 sec 90% des Kathodenstromes fliesst, der im thermischen Gleichgewicht erreicht wird, wird dieser bei dem erfindungsgemässen Heizelement schon nach etwa 3,5 sec erreicht.The heat effects are very similar to those explained in the description of FIG. 1. Because of the tight winding in the neighboring part, it heats up faster than the distant part that is further away. Due to the faster warming, the resistance rises sharply, which further supports the warming. The total wire length is again chosen so that the same current results for the same heating voltage for a known heating element and the heating element according to the invention. After the temperature differences have been equalized, there is hardly any difference in the temperature distribution between a heating element according to the invention and a known heating element. The rapid heating of the adjacent part, however, considerably reduces the heating time of the cathode. While 90% of the cathode current that is reached in thermal equilibrium flows after about 4.5 seconds in known heating elements, this is reached after about 3.5 seconds in the heating element according to the invention.

Erfindungsgemässe Heizelemente können wie folgt hergestellt werden: Eine in M-Form oder ei- ner anderen gewählten Form gebogene Heizdrahtwendel wird in ein Elektrophoresebad getaucht, bis ca. 0,18 mg/mm an Oxid abgeschieden sind.Inventive heating elements may be prepared as follows: A in M-shape or egg - ner other selected curved shape heating coil is immersed in an electrophoresis bath, are deposited to about 0.18 mg / mm of oxide.

Danach wird die Heizdrahtwendel aus dem Elektrophoresebad gezogen und so weit in ein Abwaschbad getaucht, dass im benachbarten Teil die oxidbedeckung abgewaschen wird. Nach dem Spülen in Wasser wird die Heizdrahtwendel wieder in das Elektrophoresebad getaucht und es werden nochmals 0,18 mg/mm Oxid abgeschieden. Die weitere Behandlung erfolgt wie üblich. Durch dieses Verfahren erhält der benachbarte Teil eine dünne und der entfernte Teil des Heizelements eine dicke OxidschichtThe filament is then pulled out of the electrophoresis bath and immersed in a washing bath to such an extent that the oxide covering is washed off in the adjacent part. After rinsing in water, the heating wire coil is immersed again in the electrophoresis bath and 0.18 mg / mm oxide are deposited again. Further treatment is carried out as usual. This method gives the adjacent part a thin and the distant part of the heating element a thick oxide layer

Das Verfahren kann insoweit abgewandelt werden, als beim zweiten Eintauchen in das Elektrophoresebad die Spannung so weit erhöht wird, dass gleichzeitig eine Elektrolyse auftritt. Dadurch wird die zweite Oxidschicht porös und besitzt damit noch geringere Wärmekapazität als die kompakt aufgebrachte Schicht.The method can be modified insofar as the voltage is increased so much on the second immersion in the electrophoresis bath that electrolysis occurs at the same time. As a result, the second oxide layer becomes porous and thus has an even lower heat capacity than the compactly applied layer.

Ein Heizelement nach Fig. 2 mit einer Heizdrahtwendel mit unterschiedlich dichter Wendelung kann hergestellt werden, wie mit Hilfe von Fig. 3 beschrieben wird. Auf einen Kerndräht 10 aus Molybdän von 0,175 mm Durchmesser wird ein Wolframdraht aufgewickelt, und zwar mit 42 Windungen/cm auf 7,2 mm Länge im Teil 8z und jeweils 4,1 mm Länge im Teil 83, sowie mit 90 Windungen/cm auf jeweils 4,2 mm Länge im Teil 9. Danach wird der Kerndraht mit dem aufgewickelten Heizdraht wie üblich in einem Säurebad ausgeätzt. Das Bedecken mit einer Oxidschicht kann auf herkömmliche Art und Weise oder wie in den vorigen Absätzen beschrieben erfolgen.A heating element according to FIG. 2 with a heating wire coil with different densities can be produced, as will be described with the aid of FIG. 3. On a core wire 10 a tungsten wire is wound from molybdenum of 0.175 mm diameter, with 42 turns / cm over 7.2 mm length in part 8 z and 4.1 mm length in part 8 3 , as well as with 90 turns / cm each with 4, 2 mm length in part 9. Then the core wire with the coiled heating wire is etched out in an acid bath as usual. Covering with an oxide layer can be done in a conventional manner or as described in the previous paragraphs.

Bei bevorzugten Ausführungsformen erfindungsgemässer Heizelemente beträgt die Länge des Heizelementes im benachbarten Teil etwa ein Drittel der Gesamtlänge.In preferred embodiments of heating elements according to the invention, the length of the heating element in the adjacent part is approximately one third of the total length.

Claims (8)

1. Heating element for an indirectly heated cathode which is inserted in a cathode tube closed with a cap having the emitting coating thereon and which consists of a heating coil covered with an insulating layer, one portion of the heating element being adjacent to the cap and the other being more distant from the cap, characterised in that the portion (4) of the heating element (1) which is adjacent to the cap has a lower heat-radiating capacity per unit length than the more distant portion (5B, 5z), the portion (4) adjacent to the cap consisting of at least two sections between which at least one distant portion (5z) with a greater heat-emitting capacity per unit length is placed.
2. A heating element for an indirectly heated cathode which is inserted in a cathode tube closed with a cap having the emitting coating thereon and which consists of a heating coil covered with an insulating layer, one portion of the heating element being adjacent to the cap and the other being more distant from the cap, characterised in that the heating coil (6) of the heating element (7) in the portion (9) adjacent to the cap is more closely wound than in the more distant portion (8B, 8z), the portion (8B) adjacent to the cap consisting of at least two sections between at least one more distant portion (8z) with a less closely wound heating coil is placed.
3. A heating element according to Claim 1 or 2, characterised in that the heating coil (6) in the portion (4) adjacent to the cap (2) is covered with a thinner insulating layer than in the more distant portion (5a, 5z).
4. A heating element according to Claim 1 or 2, characterised in that the heating coil (6) is covered with a porous insulating layer in the portion (4) adjacent to the cap (3) and with a dense insulating layer in the more distant portion (5z, 58).
5. A heating element according to Claim 1 or 2, characterised in that the heating coil (6) is covered with a dense layer in the more distant portion (5z, 5B) and that a porous layer is applied over the dense layer on the entire heating coil (1).
6. A heating element according to any one of Claims 1 to 5, characterised in that the heating coil (6) is bent in the shape of an M.
7. A heating element according to any one of Claims 1 to 5, characterised in that the heating coil (6) is in the shape of a coiled coil.
8. A heating element according to any one of Claims 1 to 7, characterised in that the length of the portion (4, 9) adjacent to the cap (3) is about one-third of the length of the entire heating coil (6).
EP80105443A 1979-09-21 1980-09-12 Heating element for indirectly heated cathode Expired EP0025946B1 (en)

Applications Claiming Priority (2)

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DE2938248 1979-09-21
DE19792938248 DE2938248A1 (en) 1979-09-21 1979-09-21 HEATING ELEMENT FOR AN INDIRECTLY HEATED CATHODE

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EP0025946B1 true EP0025946B1 (en) 1985-02-06

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DE3029853C2 (en) * 1980-08-07 1982-08-26 Standard Elektrik Lorenz Ag, 7000 Stuttgart Wehnelt cathode indirectly heated by electron impact
JPS58100329A (en) * 1981-12-11 1983-06-15 Toshiba Corp Cathode structure for electron tube
US4760306A (en) * 1983-06-10 1988-07-26 The United States Of America As Represented By The United States Department Of Energy Electron emitting filaments for electron discharge devices
US4939411A (en) * 1986-11-19 1990-07-03 North American Philips Corporation Composite vacuum evaporation coil
DE19828158C1 (en) * 1998-06-24 1999-11-25 Siemens Ag Indirectly heated cathode, especially for X-ray tube
US6690103B1 (en) 1999-07-21 2004-02-10 Alan K. Uke Incandescent light bulb with variable pitch coiled filament
US7009329B2 (en) 2003-08-20 2006-03-07 Hewlett-Packard Development Company, L.P. Thermally optimized cold cathode heater
JP2010225420A (en) * 2009-03-24 2010-10-07 Stanley Electric Co Ltd Hot-cathode fluorescent lamp, and electrode for fluorescent lamp

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DE2317446C3 (en) * 1973-04-06 1983-11-10 Standard Elektrik Lorenz Ag, 7000 Stuttgart Method of manufacturing a heating element for an indirectly heated cathode
US3883767A (en) * 1974-02-08 1975-05-13 Gte Sylvania Inc Heater for fast warmup cathode
JPS5427230B2 (en) * 1974-10-30 1979-09-08

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US4355259A (en) 1982-10-19
DE2938248A1 (en) 1981-03-26
JPS56103842A (en) 1981-08-19

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