EP0187576B1 - Process and apparatus for detecting the vaporization of getter material during the manufacture of a cathode ray tube, especially for television - Google Patents

Process and apparatus for detecting the vaporization of getter material during the manufacture of a cathode ray tube, especially for television Download PDF

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Publication number
EP0187576B1
EP0187576B1 EP85402415A EP85402415A EP0187576B1 EP 0187576 B1 EP0187576 B1 EP 0187576B1 EP 85402415 A EP85402415 A EP 85402415A EP 85402415 A EP85402415 A EP 85402415A EP 0187576 B1 EP0187576 B1 EP 0187576B1
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Prior art keywords
cathode
tube
current
intensity
evaporation
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EP85402415A
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German (de)
French (fr)
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EP0187576A1 (en
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Giuliano Giudici
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Videocolor SA
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Videocolor SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/42—Measurement or testing during manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J7/00—Details not provided for in the preceding groups and common to two or more basic types of discharge tubes or lamps
    • H01J7/14—Means for obtaining or maintaining the desired pressure within the vessel
    • H01J7/18—Means for absorbing or adsorbing gas, e.g. by gettering

Definitions

  • the invention relates to a method and an apparatus for detecting whether the getter material has been correctly evaporated during the manufacture of a cathode-ray tube, in particular color television set.
  • a cathode-ray tube is constituted by a vacuum glass vial with a front part forming a screen connected via a flared part to the cylindrical rear part, called the neck, at the end of which is housed the barrel (or the guns) with electrons.
  • the electron gun of which a cup containing the getter material to be evaporated is attached, is installed in the bulb which is then emptied by pumping; then the getter material is evaporated by heating using an induction coil, after which the cathode (s) are heated to a temperature higher than the usual operating temperature in order to form and stabilize the material forming this cathode, and apply to the grids of the barrel voltages intended to clean the tube, that is to say to remove unwanted gaseous particles which are absorbed by the getter material.
  • the tube thus produced will not be able to function correctly due, on the one hand, to the poor quality of the vacuum, and on the other hand, above all, to the presence of positive ions who will be attracted to and deteriorate the cathode.
  • the invention overcomes these drawbacks.
  • the intensity of the electric current flowing between the electrode brought to a negative potential and the mass represents the charge in positive ions in the tube and therefore the pressure. It is important to note that, for the measurement, the cathode is not used; indeed, if, on the latter, a negative potential was applied it would attract positive ions, which would damage it.
  • the intensity of the current flowing in the grid G 3 exceeds 150 nanoamps, which corresponds to a pressure of 2 x 10- 4 Torr, if the material of the getter has not evaporated to spread on the walls of the tube and is of the order of 25 nanoamps - i.e. 4 at 5 x 10- 5 Torr - otherwise.
  • the tube being treated is thus brought back to the station for evaporation of the getter material if the intensity between the electrode G 3 ⁇ and the mass exceeds 150 nanoamps.
  • the generator applying a positive potential on one of the electrodes is a constant current generator so that the intensity of the measurement current is not affected, or is little affected by the differences in characteristics between individual tubes, these differences or dispersions being inherent in mass production.
  • the example which will be described relates to the manufacture of a color television tube of the shadow mask type.
  • the getter material is evaporated so that it is distributed over all the glass walls .
  • This getter material is constituted by a barium tablet placed in a cup 12 located in the conical or flared part 13 of the bulb 11 attached by a rod 14 to the envelope of the block 15 of electron guns.
  • the heating of the barium with a view to its evaporation is carried out using an induction coil 16 arranged outside the bulb 1.1 but in the vicinity of the cup 12.
  • the frequency and the power of the supply of the coil 16 are such that they make it possible to reach a temperature of this cup of between 800 and 1100 ° C.
  • This cathode 20 usually comprises a nickel tube and the electron-emitting material consists of a mixture of barium, strontium and calcium oxides.
  • the heating filament 21 for heating the latter is brought to a temperature higher than that of normal operation.
  • the formation, or activation, of the cathode is carried out for a period of duration approximately 4 minutes; this activation period is itself divided into two stages of roughly equal durations: during the first the cathode material is brought to a temperature of approximately 1000 ° C. and during the second stage this material is brought to a higher temperature, of the order of 1070 ° C.
  • the cathode material is stabilized for approximately 14 minutes. During this stabilization the cathode material is brought to a temperature of about 1000 ° C.
  • gases such as carbon monoxide CO, carbon anhydride C0 2 , methane CH 4 , are released in the latter, in particular during activation. etc ...
  • gases contain in equal proportions, from the electrical point of view, positive ions and negative ions.
  • Positive ions (+) are particularly harmful to the cathode because, the latter being brought to a negative potential, it attracts positive charges, which risks damaging it.
  • the getter material distributed over the walls of the bulb 11 absorbs the gases released both during the formation of the cathode material and during subsequent degassing treatments.
  • the gas pressure in the tube is measured after the cathode material has been formed, during the period of stabilization of this material. This pressure is measured before the subsequent degassing or controlled aging operation. For this measurement, the charge of positive ions is determined. For this purpose, approximately 10 minutes after the start of activation of the cathode material, that is to say during the stabilization period, a positive potential is applied to the second grid 22, called G 2 , in connecting the latter to the positive potential terminal 25 of a constant current generator 24 and a negative potential is applied to the third grid 23, called G 3 , by connecting the negative terminal of a voltage generator 26 to this grid G 3 .
  • the source 26 delivers a voltage of 22.5 volts in the example.
  • a resistor 27 of value 100 K ⁇ for example is connected between the positive potential terminal of the source 26 and the ground.
  • a voltmeter 28 is connected in parallel to this resistor 27.
  • the voltage measured by this voltmeter represents the intensity of the current passing through the resistor 27, that is to say leaving the gate G 3 .
  • the first grid, called G 1 is connected to ground, as is the cathode 20.
  • the positive ions are attracted by the gate 23 brought to a negative potential, while the negative ions are attracted to the gate G 2 , 22, brought to a positive potential.
  • the current - measured by the voltmeter 28 - flowing in the resistor 27 represents the charge in positive ions in the bulb 11 and therefore the total pressure.
  • connection, to the respective grids, of the source 26 and of the generator 24 is effected by means of a socket 30 (FIG. 4), that which is usually used to make the connections for the formation of the cathode material and degassing treatments.
  • the intensity i of the current in the resistor 27 varies as a function of time t as represented by the curve 31 (FIG. 3) in solid lines.
  • the current has an intensity of the order of 300 nanoamps.
  • this intensity has dropped to the value of 25 nanoamps.
  • the tube is brought back to the induction heating station to evaporate the barium pellet.
  • the intensity is less than 150 nanoamps, the tube remains on the production line to undergo the degassing treatment.
  • the socket 30 is separated from the tube 10 but the latter remains on the production line with the other tubes until the end of the degassing treatment.
  • the tube which does not include a socket 30 does not undergo either the end of the stabilization of the cathode material or the degassing or aging. In this example, the tube is returned to the induction heating station after the degassing period which it has not, however, undergone.
  • the comparison with the value of 150 nanoamps can be carried out by an operator. It is also possible to provide a comparator for delivering a signal when the intensity exceeds said predetermined value. This signal can activate visual or audible alarm means. This signal can also be used to control a socket extraction mechanism 30.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)

Abstract

A method for checking the evaporation of a pellet of getter material such as barium on the walls of the envelope of a cathode-ray tube during manufacture. The pressure within the cathode-ray tube is measured during the operation involving stabilization of the cathode material by measuring the positive-ion charge within the tube.

Description

L'invention est relative à un procédé et à un appareil pour détecter si le matériau getter a été correctement évaporé au cours de la fabrication d'un tube cathodique, notamment de-télévision en couleurs.The invention relates to a method and an apparatus for detecting whether the getter material has been correctly evaporated during the manufacture of a cathode-ray tube, in particular color television set.

Un tube cathodique est constitué par une ampoule de verre sous vide avec une partie frontale formant écran raccordée par l'intermédiaire d'une partie évasée à la partie arrière cylindrique, appelée col, à l'extrémité de laquelle est logé le canon (ou les canons) à électrons.A cathode-ray tube is constituted by a vacuum glass vial with a front part forming a screen connected via a flared part to the cylindrical rear part, called the neck, at the end of which is housed the barrel (or the guns) with electrons.

Les dernières étapes de fabrication du tube sont les suivantes : le canon à électrons duquel est solidaire une coupelle contenant le matériau de getter à évaporer, est installé dans l'ampoule qu'on vide ensuite par pompage ; puis on évapore le matériau getter par chauffage à l'aide d'une bobine d'induction, à la suite de quoi on chauffe la (ou les) cathode(s) à une température supérieure à la température habituelle de fonctionnement afin de former et stabiliser le matériau formant cette cathode, et on applique aux grilles du canon des tensions destinées à nettoyer le tube, c'est-à-dire à éliminer les particules gazeuses indésirables qui sont absorbées par le matériau getter. Si le matériau getter ne s'est pas évaporé, le tube ainsi réalisé ne pourra pas fonctionner correctement en raison, d'une part, de la mauvaise qualité du vide, et d'autre part, surtout, de la présence d'ions positifs qui seront attirés par la cathode et la détérioreront.The last stages of tube manufacturing are as follows: the electron gun, of which a cup containing the getter material to be evaporated is attached, is installed in the bulb which is then emptied by pumping; then the getter material is evaporated by heating using an induction coil, after which the cathode (s) are heated to a temperature higher than the usual operating temperature in order to form and stabilize the material forming this cathode, and apply to the grids of the barrel voltages intended to clean the tube, that is to say to remove unwanted gaseous particles which are absorbed by the getter material. If the getter material has not evaporated, the tube thus produced will not be able to function correctly due, on the one hand, to the poor quality of the vacuum, and on the other hand, above all, to the presence of positive ions who will be attracted to and deteriorate the cathode.

On a constaté que sur les chaînes de fabrication en série pour environ 1 % des tubes l'évaporation du matériau de getter ne s'effectue pas correctement. Les tubes qui présentent ce défaut doivent alors être traités de nouveau, c'est-à-dire qu'ils doivent être dégagés de la chaîne de fabrication et ramenés au poste d'évaporation du getter. Cet incident peut avoir des causes diverses : erreur de l'opérateur, mauvais positionnement de la bobine utilisée pour le chauffage par induction en vue de l'évaporation, défaut de cette bobine ou de sa source d'alimentation, etc...It has been found that on series production lines for about 1% of the tubes the evaporation of the getter material is not carried out correctly. The tubes which have this defect must then be treated again, that is to say they must be released from the production line and brought back to the getter evaporation station. This incident can have various causes: operator error, incorrect positioning of the coil used for induction heating for evaporation, defect of this coil or its power source, etc.

Jusqu'à présent le contrôle de l'évaporation du matériau de getter s'effectue par observation visuelle des parois du tube. Un tel type de contrôle n'est pas entièrement fiable car un défaut d'évaporation peut ne pas être détecté par inattention de l'opérateur. En outre l'observation visuelle est pénible.Until now, the evaporation of the getter material has been checked by visual observation of the walls of the tube. Such a type of control is not entirely reliable because a fault in evaporation may not be detected by the operator's inattention. In addition, visual observation is painful.

Dans le brevet US 4 485 872 on a proposé un procédé et un appareil dérivés de l'observation visuelle qui se sont révélés également d'une fiabilité insatisfaisante et complexes à mettre en œuvre.In US Pat. No. 4,485,872, a method and an apparatus derived from visual observation have been proposed which have also proved to be of unsatisfactory reliability and complex to implement.

L'invention remédie à ces inconvénients.The invention overcomes these drawbacks.

Elle est caractérisée en ce que :

  • - on applique des potentiels de signes contraires à deux grilles, distinctes de la cathode, du canon à électrons ;
  • - on mesure la charge en ions positifs dans le tube, cette charge étant mesurée, après un temps t suivant le début de l'opération de formation du matériau de cathode, par l'intensité du courant circulant entre la grille de potentiel négatif et la masse ; et
  • - on compare l'intensité du courant mesuré à une valeur prédéterminée et on ramène le tube au poste d'évaporation du matériau de getter si l'intensité du courant est supérieure à la valeur prédéterminée, par exemple 150 nanoampères.
It is characterized in that:
  • - Potentials of opposite signs are applied to two grids, distinct from the cathode, from the electron gun;
  • - the charge of positive ions in the tube is measured, this charge being measured, after a time t following the start of the operation for forming the cathode material, by the intensity of the current flowing between the grid of negative potential and the mass ; and
  • - The intensity of the measured current is compared to a predetermined value and the tube is brought back to the getter material evaporation station if the current intensity is greater than the predetermined value, for example 150 nanoamps.

On mesure la charge en ions positifs car seuls ces derniers sont dangereux pour la cathode.The charge of positive ions is measured because only the latter are dangerous for the cathode.

Il pourrait aussi être envisagé de mesurer la charge en ions négatifs ; mais cette mesure serait difficile à effectuer car, au cours de la stabilisation du matériau de la cathode, cette dernière produit des électrons et la charge provenant de ces électrons s'ajoute à celles des ions négatifs et ne peut pas en être séparée ; de ce fait la charge négative mesurée ne représenterait pas corecte- ment la pression dans le tube.It could also be considered to measure the charge in negative ions; but this measurement would be difficult to carry out because, during the stabilization of the material of the cathode, the latter produces electrons and the charge coming from these electrons is added to those of negative ions and cannot be separated therefrom; therefore the measured negative charge would not correctly represent the pressure in the tube.

L'intensité du courant électrique circulant entre l'électrode portée à un potentiel négatif et la masse représente la charge en ions positifs dans le tube et donc la pression. Il est important de noter que, pour la mesure, on ne fait pas appel à la cathode ; en effet, si, sur cette dernière, on appliquait un potentiel négatif elle attirerait des ions positifs, ce qui l'endommagerait. Si le potentiel négatif appliqué sur l'électrode G3 est de -22,5 V, on a constaté qu'après un temps de 10 à 15 minutes suivant la formation du matériau de cathode, l'intensité du courant circulant dans la grille G3 dépasse 150 nanoampères, ce qui correspond à une pression de 2 x 10-4 Torr, si le matériau du getter ne s'est pas évaporé pour se répandre sur les parois du tube et est de l'ordre de 25 nanoampères - soit 4 à 5 x 10-5 Torr - dans le cas contraire. Le tube en cours de traitement est ainsi ramené au poste d'évaporation du matériau de getter si l'intensité entre l'électrode G3 ·et la masse dépasse 150 nanoampères.The intensity of the electric current flowing between the electrode brought to a negative potential and the mass represents the charge in positive ions in the tube and therefore the pressure. It is important to note that, for the measurement, the cathode is not used; indeed, if, on the latter, a negative potential was applied it would attract positive ions, which would damage it. If the negative potential applied to the electrode G 3 is -22.5 V, it has been found that after a time of 10 to 15 minutes following the formation of the cathode material, the intensity of the current flowing in the grid G 3 exceeds 150 nanoamps, which corresponds to a pressure of 2 x 10- 4 Torr, if the material of the getter has not evaporated to spread on the walls of the tube and is of the order of 25 nanoamps - i.e. 4 at 5 x 10- 5 Torr - otherwise. The tube being treated is thus brought back to the station for evaporation of the getter material if the intensity between the electrode G 3 · and the mass exceeds 150 nanoamps.

Il est préférable que le générateur appliquant un potentiel positif sur l'une des électrodes soit un générateur à courant constant afin que l'intensité du courant de mesure ne soit pas affectée, ou soit peu affectée par les différences de caractéristiques entre tubes individuels, ces différences ou dispersions étant inhérentes à la fabrication en grande série.It is preferable that the generator applying a positive potential on one of the electrodes is a constant current generator so that the intensity of the measurement current is not affected, or is little affected by the differences in characteristics between individual tubes, these differences or dispersions being inherent in mass production.

D'autres caractéristiques et avantages de l'invention apparaîtront avec la description de certains de ses modes de réalisation, celle-ci étant effectuée en se référant aux dessins ci- annexés sur lesquels :

  • - la figure 1 est un schéma d'une partie d'un tube cathodique lors de sa fabrication.
  • - la figure 2 montre un canon à électrons d'un tube cathodique et des sources de courant et de tension utilisées pour mettre en oeuvre le procédé de l'invention,
  • - la figure 3 est un diagramme expliquant le procédé de l'invention et,
  • - la figure 4 est un schéma de la partie arrière d'un tube cathodique au cours d'une étape de sa fabrication.
Other characteristics and advantages of the invention will appear with the description of some of its embodiments, this being carried out with reference to the attached drawings in which:
  • - Figure 1 is a diagram of part of a cathode ray tube during its manufacture.
  • FIG. 2 shows an electron gun of a cathode ray tube and of the current and voltage sources used to implement the method of the invention,
  • - Figure 3 is a diagram explaining the process of the invention and,
  • - Figure 4 is a diagram of the rear part of a cathode ray tube during a stage of its manufacture.

L'exemple que l'on va décrire se rapporte à la fabrication d'un tube de télévision en couleurs du type à masque d'ombre.The example which will be described relates to the manufacture of a color television tube of the shadow mask type.

Lors des dernières étapes de la fabrication d'un tube cathodique 10, juste après la mise sous vide de l'ampoule de verre 11, on procède à l'évaporation du matériau de getter afin qu'il soit réparti sur toutes les parois de verre. Ce matériau de getter est constitué par une pastille de baryum disposée dans une coupelle 12 se trouvant dans la partie cônique pu évasée 13 de l'ampoule 11 rattachée par une tige 14 à l'enveloppe du bloc 15 de canons à électrons.During the last stages of the manufacture of a cathode ray tube 10, just after the evacuation of the glass ampoule 11, the getter material is evaporated so that it is distributed over all the glass walls . This getter material is constituted by a barium tablet placed in a cup 12 located in the conical or flared part 13 of the bulb 11 attached by a rod 14 to the envelope of the block 15 of electron guns.

Le chauffage du baryum en vue de son évaporation est effectué à l'aide d'une bobine d'induction 16 disposée à l'extérieur de l'ampoule 1.1 mais au voisinage de la coupelle 12. La fréquence et la puissance de l'alimentation de la bobine 16 sont telles qu'elles permettent d'atteindre une tempé- raturé de cette coupelle comprise entre 800 et 1100°C.The heating of the barium with a view to its evaporation is carried out using an induction coil 16 arranged outside the bulb 1.1 but in the vicinity of the cup 12. The frequency and the power of the supply of the coil 16 are such that they make it possible to reach a temperature of this cup of between 800 and 1100 ° C.

Après cette évaporation du baryum on procède à la formation et la stabilisation du matériau formant la cathode 20 (figure 2). Cette cathode 20 comporte habituellement un tube de nickel et le matériau d'émission des électrons est constitué par un mélange d'oxydes de baryum, de strontium et de calcium.After this evaporation of the barium, the material forming the cathode 20 is formed and stabilized (FIG. 2). This cathode 20 usually comprises a nickel tube and the electron-emitting material consists of a mixture of barium, strontium and calcium oxides.

Pour la formation et la stabilisation du matériau de cathode on porte le filament 21 de chauffage de cette dernière à une température supérieure à celle du fonctionnement habituel.For the formation and stabilization of the cathode material, the heating filament 21 for heating the latter is brought to a temperature higher than that of normal operation.

La formation, ou activation, de la cathode est effectuée pendant une période de durée 4 minutes environ ; cette période d'activation est elle-même divisée en deux étapes de durées à peu près égales : au cours de la première le matériau de cathode est porté à une température de 1 000 °C environ et au cours de la seconde étape ce matériau est porté à une température supérieure, de l'ordre de 1 070 °C.The formation, or activation, of the cathode is carried out for a period of duration approximately 4 minutes; this activation period is itself divided into two stages of roughly equal durations: during the first the cathode material is brought to a temperature of approximately 1000 ° C. and during the second stage this material is brought to a higher temperature, of the order of 1070 ° C.

La stabilisation du matériau de cathode est effectuée pendant 14 minutes environ. Lors de cette stabilisation le matériau de cathode est porté à une température d'environ 1 000 °C. Au cours de ces étapes de la fabrication du tube il se dégage, dans ce dernier, en particulier lors de l'activation, des gaz tels que l'oxyde de carbone CO, l'anhydride de carbone C02, le méthane CH4, etc... Ces gaz contiennent en proportions égales, du point de vue électrique, des ions positifs et des ions négatifs. Les ions positifs (+) sont particulièrement nocifs pour la cathode car, celle-ci étant portée à un potentiel négatif, elle attire les charges positives, ce qui risque de la détériorer. Le matériau de getter réparti sur les parois de l'ampoule 11 absorbe les gaz dégagés tant lors de la formation du matériau de cathode que lors des traitements ultérieurs de dégazage.The cathode material is stabilized for approximately 14 minutes. During this stabilization the cathode material is brought to a temperature of about 1000 ° C. During these stages of the manufacture of the tube, gases such as carbon monoxide CO, carbon anhydride C0 2 , methane CH 4 , are released in the latter, in particular during activation. etc ... These gases contain in equal proportions, from the electrical point of view, positive ions and negative ions. Positive ions (+) are particularly harmful to the cathode because, the latter being brought to a negative potential, it attracts positive charges, which risks damaging it. The getter material distributed over the walls of the bulb 11 absorbs the gases released both during the formation of the cathode material and during subsequent degassing treatments.

Pour contrôler que le baryum contenu dans la coupelle 12 a été correctement évaporé, selon l'invention, on mesure la pression de gaz dans le tube après la formation du matériau de cathode, au cours de la période de stabilisation de ce matériau. Cette pression est mesurée avant l'opération ultérieure de dégazage ou vieillissement contrôlé. Pour cette mesure on détermine la charge en ions positifs. A cet effet, environ 10 minutes après le début de l'activation du matériau de cathode, c'est-à-dire au cours de la période de stabilisation, on applique un potentiel positif sur la seconde grille 22, dite G2, en reliant cette dernière à la borne 25 de potentiel positif d'un générateur 24 de courant constant et on applique un potentiel négatif sur la troisième grille 23, dite G3, en reliant la borne négative d'un générateur de tension 26 à cette grille G3. La source 26 délivre une tension de 22,5 Volts dans l'exemple.To check that the barium contained in the cup 12 has been correctly evaporated, according to the invention, the gas pressure in the tube is measured after the cathode material has been formed, during the period of stabilization of this material. This pressure is measured before the subsequent degassing or controlled aging operation. For this measurement, the charge of positive ions is determined. For this purpose, approximately 10 minutes after the start of activation of the cathode material, that is to say during the stabilization period, a positive potential is applied to the second grid 22, called G 2 , in connecting the latter to the positive potential terminal 25 of a constant current generator 24 and a negative potential is applied to the third grid 23, called G 3 , by connecting the negative terminal of a voltage generator 26 to this grid G 3 . The source 26 delivers a voltage of 22.5 volts in the example.

Entre la borne de potentiel positif de la source 26 et la masse est disposée une résistance 27 de valeur 100 KΩ par exemple. En parallèle sur cette résistance 27 est connecté un voltmètre 28. la tension mesurée par ce voltmètre représente l'intensité du courant traversant la résistance 27, c'est-à-dire sortant dé la grille G3. Au cours de cette étape de contrôle de pression par mesure de la charge en ions positifs dans le tube, la première grille, dite G1, est reliée à la masse, de même que la cathode 20.Between the positive potential terminal of the source 26 and the ground is placed a resistor 27 of value 100 KΩ for example. In parallel to this resistor 27 is connected a voltmeter 28. the voltage measured by this voltmeter represents the intensity of the current passing through the resistor 27, that is to say leaving the gate G 3 . During this pressure control step by measuring the charge of positive ions in the tube, the first grid, called G 1 , is connected to ground, as is the cathode 20.

Les ions positifs sont attirés par la grille 23 portée à un potentiel négatif, tandis que les ions négatifs sont attirés vers la grille G2, 22, portée à un potentiel positif. Ainsi le courant - mesuré par le voltmètre 28 - circulant dans la résistance 27 représente la charge en ions positifs dans l'ampoule 11 et donc la pression totale.The positive ions are attracted by the gate 23 brought to a negative potential, while the negative ions are attracted to the gate G 2 , 22, brought to a positive potential. Thus the current - measured by the voltmeter 28 - flowing in the resistor 27 represents the charge in positive ions in the bulb 11 and therefore the total pressure.

La connexion, aux grilles respectives, de la source 26 et du générateur 24 s'effectue par l'intermédiaire d'une douille 30 (figure 4), celle qui est habituellement utilisée pour effectuer les connexions en vue de la formation du matériau de cathode et des traitements de dégazage.The connection, to the respective grids, of the source 26 and of the generator 24 is effected by means of a socket 30 (FIG. 4), that which is usually used to make the connections for the formation of the cathode material and degassing treatments.

Si le baryum a été correctement évaporé l'intensité i du courant dans la résistance 27 varie en fonction du temps t comme représenté par la courbe 31 (figure 3) en traits pleins. Tout de suite après la formation de la cathode, au temps t = 0, le courant a une intensité de l'ordre de 300 nanoampères. Au bout d'un temps de l'ordre de 10 minutes cette intensité est descendue à la valeur de 25 nanoampères. Par contre si le baryum n'a pas été évaporé l'intensité i varie selon la courbe 32 en traits interrompus ; au bout du temps t = 10 minutes environ, cette intensité a une valeur de l'ordre de 200 nanoampères.If the barium has been correctly evaporated, the intensity i of the current in the resistor 27 varies as a function of time t as represented by the curve 31 (FIG. 3) in solid lines. Immediately after the cathode is formed, at time t = 0, the current has an intensity of the order of 300 nanoamps. After a time of the order of 10 minutes, this intensity has dropped to the value of 25 nanoamps. On the other hand, if the barium has not been evaporated, the intensity i varies according to curve 32 in broken lines; at the end of time t = 10 minutes approximately, this intensity has a value of the order of 200 nanoamps.

De cette manière si l'intensité i du courant dans la résistance 27 dépasse 150 nanoampères le tube est ramené au poste de chauffage par induction pour évaporer la pastille de baryum. Par contre si l'intensité est inférieure à 150 nanoampères, le tube reste sur la chaîne de fabrication pour subir le traitement de dégazage. Dans un exemple si l'intensité i du courant dépasse 150 nanoampères la douille 30 est séparée du tube 10 mais ce dernier reste sur la chaîne de fabrication avec les autres tubes jusqu'à la fin du traitement de dégazage. Mais le tube qui ne comporte pas de douille 30 ne subit ni la fin de la stabilisation du matériau de cathode ni le dégazage ou vieillissement. Dans cet exemple le tube est ramené au poste de chauffage par induction après la période de dégazage qu'il n'a cependant pas subie.In this way, if the intensity i of the current in the resistor 27 exceeds 150 nanoamps, the tube is brought back to the induction heating station to evaporate the barium pellet. On the other hand, if the intensity is less than 150 nanoamps, the tube remains on the production line to undergo the degassing treatment. In an example if the intensity i of the current exceeds 150 nanoamps the socket 30 is separated from the tube 10 but the latter remains on the production line with the other tubes until the end of the degassing treatment. However, the tube which does not include a socket 30 does not undergo either the end of the stabilization of the cathode material or the degassing or aging. In this example, the tube is returned to the induction heating station after the degassing period which it has not, however, undergone.

la comparaison avec la valeur de 150 nanoampères peut être effectuée par un opérateur. On peut également prévoir un comparateur pour délivrer un signal lorsque l'intensité dépasse ladite valeur prédéterminée. ce signal peut actionner des moyens d'alarme visuels ou sonores. Ce signal peut également être utilisé pour commander un mécanisme d'extraction de douille 30.the comparison with the value of 150 nanoamps can be carried out by an operator. It is also possible to provide a comparator for delivering a signal when the intensity exceeds said predetermined value. this signal can activate visual or audible alarm means. This signal can also be used to control a socket extraction mechanism 30.

Claims (7)

1. A method for controlling the evaporation of a blob of a getter material such as barium, on the walls of the envelope (11) of a cathode ray tube during the course of the manufacture thereof, characterized in that :
- potentials of opposite sign are applied to two grids (22 and 23), distinct from the cathode, of the electron gun (15),
- the charge of positive ions in the tube is measured, the said charge being measured, after the time t following the start of the operation of forming the cathode material, by the intensity of current circulating between the grid at a negative potential and ground ; and
- the intensity of the current measured is compared with a predetermined value and the tube is returned to the position for the evaporation of getter material if the intensity of the current is superior to the predetermined value.
2. The method as claimed in claim 1, characterized in that there is applied to the grid G2 (22) a positive potential and in that to the grid G3 (23) there is applied a negative potential, the measured intensity being that of the current with circulates between the grid G. (23) and ground.
3. The method as claimed in claim 1 or claim 2, characterized in that the application of the said potentials to the grids of the electron gun is effected by the intermediary of a sleeve (30) which is also used for establishing the electrical connections at the time of the formation of the cathode material and of the degassing treatments.
4. The method as claimed in any one of the claims 1 through 3, characterized in that the positive potential applied to one of the grids of the electron gun is furnished by a constant current generator (24).
5. The method as claimed in any one of preceding claims, characterized in that the measurement of the current is undertaken approximately 10 minutes after the start of the operation of the formation of the material of the cathode.
6. The method as claimed in claim 3, characterized in that if the intensity of the current is superior to the predetermined value the sleeve is separated from the tube and the latter is later returned to the position for the evaporation of the getter is later returned to the position for the evaporation of the getter material.
7. The method as claimed in any one of the preceding claims characterized in that the predetermined value is of the order of 150 nanoam- peres.
EP85402415A 1984-12-07 1985-12-04 Process and apparatus for detecting the vaporization of getter material during the manufacture of a cathode ray tube, especially for television Expired EP0187576B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85402415T ATE43203T1 (en) 1984-12-07 1985-12-04 METHOD AND DEVICE FOR DETECTING GATE MATERIAL EVAPORATION DURING THE MANUFACTURE OF A CATHODE RAY TUBE, ESPECIALLY FOR TELEVISION.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8418777 1984-12-07
FR8418777A FR2574590B1 (en) 1984-12-07 1984-12-07 METHOD AND APPARATUS FOR DETECTING EVAPORATION OF GETTING MATERIAL DURING THE MANUFACTURE OF A CATHODE RAY TUBE, PARTICULARLY FOR TELEVISION

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EP0187576A1 EP0187576A1 (en) 1986-07-16
EP0187576B1 true EP0187576B1 (en) 1989-05-17

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EP85402415A Expired EP0187576B1 (en) 1984-12-07 1985-12-04 Process and apparatus for detecting the vaporization of getter material during the manufacture of a cathode ray tube, especially for television

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US (1) US4668203A (en)
EP (1) EP0187576B1 (en)
JP (1) JPS61138434A (en)
AT (1) ATE43203T1 (en)
DE (1) DE3570323D1 (en)
FR (1) FR2574590B1 (en)
HK (1) HK102690A (en)
IN (1) IN166685B (en)
SG (1) SG78190G (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8703042A (en) * 1987-12-16 1989-07-17 Philips Nv GETTERING DEVICE WITH A GETTER DETECTOR AND A POST HEATING CLOCK.
IT1241102B (en) * 1990-04-11 1993-12-29 Getters Spa METHOD AND EQUIPMENT FOR THE AUTOMATIC DETECTION OF THE EVAPORATION TIME OF THE BARIER GETTERS DEVICES
JP2962270B2 (en) * 1997-04-03 1999-10-12 日本電気株式会社 Manufacturing method of cathode ray tube

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2141644A (en) * 1937-11-27 1938-12-27 Rca Corp Manufacture of evacuated metal envelopes
US2861861A (en) * 1951-11-13 1958-11-25 Rca Corp Gas pressure testing and control apparatus
US3227506A (en) * 1961-09-18 1966-01-04 Rca Corp Method of making electron tubes
JPS4874777A (en) * 1971-12-30 1973-10-08
US4038616A (en) * 1976-04-29 1977-07-26 Rca Corporation Vacuum tube gas test apparatus
JPS5574038A (en) * 1978-11-29 1980-06-04 Hitachi Ltd Vacuum measuring device for picture tube
US4445872A (en) * 1982-01-18 1984-05-01 Rca Corporation Method of detecting the vaporization of getter material during manufacture of a CRT

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ATE43203T1 (en) 1989-06-15
US4668203A (en) 1987-05-26
DE3570323D1 (en) 1989-06-22
FR2574590B1 (en) 1988-05-13
JPS61138434A (en) 1986-06-25
HK102690A (en) 1990-12-14
EP0187576A1 (en) 1986-07-16
IN166685B (en) 1990-06-30
SG78190G (en) 1991-01-18
FR2574590A1 (en) 1986-06-13

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