EP0187576B1 - Procédé et appareil pour la détection de l'évaporation du matériau de getter au cours de la fabrication d'un tube cathodique, notamment pour la télévision - Google Patents

Procédé et appareil pour la détection de l'évaporation du matériau de getter au cours de la fabrication d'un tube cathodique, notamment pour la télévision 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
Authority
EP
European Patent Office
Prior art keywords
cathode
tube
current
intensity
evaporation
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.)
Expired
Application number
EP85402415A
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German (de)
English (en)
French (fr)
Other versions
EP0187576A1 (fr
Inventor
Giuliano Giudici
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.)
Videocolor SA
Original Assignee
Videocolor SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Videocolor SA filed Critical Videocolor SA
Priority to AT85402415T priority Critical patent/ATE43203T1/de
Publication of EP0187576A1 publication Critical patent/EP0187576A1/fr
Application granted granted Critical
Publication of EP0187576B1 publication Critical patent/EP0187576B1/fr
Expired legal-status Critical Current

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Classifications

    • 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)
EP85402415A 1984-12-07 1985-12-04 Procédé et appareil pour la détection de l'évaporation du matériau de getter au cours de la fabrication d'un tube cathodique, notamment pour la télévision Expired EP0187576B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85402415T ATE43203T1 (de) 1984-12-07 1985-12-04 Verfahren und vorrichtung zur feststellung der gattermaterialverdampfung waehrend der herstellung einer kathodenstrahlroehre, insbesondere fuer das fernsehen.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8418777 1984-12-07
FR8418777A FR2574590B1 (fr) 1984-12-07 1984-12-07 Procede et appareil pour la detection de l'evaporation du materiau de getter au cours de la fabrication d'un tube cathodique, notamment pour la television

Publications (2)

Publication Number Publication Date
EP0187576A1 EP0187576A1 (fr) 1986-07-16
EP0187576B1 true EP0187576B1 (fr) 1989-05-17

Family

ID=9310385

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85402415A Expired EP0187576B1 (fr) 1984-12-07 1985-12-04 Procédé et appareil pour la détection de l'évaporation du matériau de getter au cours de la fabrication d'un tube cathodique, notamment pour la télévision

Country Status (9)

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

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8703042A (nl) * 1987-12-16 1989-07-17 Philips Nv Getterinrichting met een getterdetector en een naverwarmingstijdklok.
IT1241102B (it) * 1990-04-11 1993-12-29 Getters Spa Metodo ed apparecchiatura per la rilevazione automatica del tempo di evaporazione dei dispositivi getters al bario
JP2962270B2 (ja) * 1997-04-03 1999-10-12 日本電気株式会社 陰極線管の製造方法

Family Cites Families (7)

* 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 (enrdf_load_stackoverflow) * 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

Also Published As

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

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