EP0002926B1 - Cathode ray tube with implosion protection and method for manufacturing it - Google Patents

Cathode ray tube with implosion protection and method for manufacturing it Download PDF

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Publication number
EP0002926B1
EP0002926B1 EP78300859A EP78300859A EP0002926B1 EP 0002926 B1 EP0002926 B1 EP 0002926B1 EP 78300859 A EP78300859 A EP 78300859A EP 78300859 A EP78300859 A EP 78300859A EP 0002926 B1 EP0002926 B1 EP 0002926B1
Authority
EP
European Patent Office
Prior art keywords
coating
ray tube
cathode
tube
window
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
EP78300859A
Other languages
German (de)
English (en)
French (fr)
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EP0002926A1 (en
Inventor
Samuel Broughton Deal
Donald Walter Bartch
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.)
RCA Corp
Original Assignee
RCA Corp
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 RCA Corp filed Critical RCA Corp
Publication of EP0002926A1 publication Critical patent/EP0002926A1/en
Application granted granted Critical
Publication of EP0002926B1 publication Critical patent/EP0002926B1/en
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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
    • H01J9/20—Manufacture of screens on or from which an image or pattern is formed, picked up, converted or stored; Applying coatings to the vessel
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/86—Vessels; Containers; Vacuum locks
    • H01J29/87—Arrangements for preventing or limiting effects of implosion of vessels or containers

Definitions

  • This invention relates to providing cathode-ray tubes with implosion protection.
  • Cathode-ray tubes comprising evacuated glass bulbs are mass-produced articles of commerce. They usually include a glass faceplate panel hermetically sealed to the wide end of a glass funnel. A luminescent screen is carried on the inner surface of the panel, and one or more electron guns are housed in a neck attached to the narrow end of the funnel. Some adverse effects of implosion of the bulb can be reduced or eliminated by providing an implosion-protection system around the panel.
  • a rigid coating of a plastic-impregnated fiber or fabric encircles and adheres to the panel.
  • An encircling steel band on or adjacent to the plastic impregnated coating may or may not also be provided.
  • the plastic adhesive is usually a self-curing epoxy or polyester material.
  • an implosion-resisting band such as of metal or glass fiber is placed round the cathode-ray tube and adhered to it by an adhesive for which various materials, including polyurethane, have been suggested.
  • FR-A-1349345 It has also been suggested, for instance in GB-A-1040381 already mentioned and in FR-A-1349345, to apply a sheath or lining of foamed polyurethane (or other material) to provide implosion protection with the possibility, according to FR-A-1349346 that the foamed sheath may be self-adherent to the cathode-ray tube or may be stuck to it, for instance by polyurethane adhesive.
  • the invention also includes a method of providing implosion protection by preheating the cathode-ray tube to between about 20°C to 90°C, applying a water based emulsion of polyurethane to the relevant surfaces of the cathode-ray tube envelope by brushing, flowing or spraying, and thereafter heating the coated tube to between about 20°C and 120°C for about 30-5 minutes to leave the required elastomeric polyurethane film.
  • a method of providing implosion protection by preheating the cathode-ray tube to between about 20°C to 90°C, applying a water based emulsion of polyurethane to the relevant surfaces of the cathode-ray tube envelope by brushing, flowing or spraying, and thereafter heating the coated tube to between about 20°C and 120°C for about 30-5 minutes to leave the required elastomeric polyurethane film.
  • the cathode-ray tube illustrated in Figure 1 includes an evacuated envelope designated generally by the numeral 21.
  • the envelope 21 includes a glass neck 23 integral with a glass funnel 25, and a glass faceplate panel comprising a viewing window 27 having a peripheral sidewall 29.
  • the rim of the sidewall 29 is sealed to the wide end of the funnel 25 by a seal 31, such as devitrified glass.
  • the neck 23 is closed and sealed by a stem 35 having stem leads 37 extending therethrough.
  • An anode button (terminal) 43 is sealed through the funnel wall.
  • a luminescent screen (not shown) resides on the inside surface of the viewing window 27.
  • the luminescent screen when suitably scanned by an electron beam from a gun 33 housed in the neck 23, is capable of producing a luminescent image which may be viewed through the viewing window 27.
  • the interior of the envelope is evacuated to a high level of vacuum (low pressure) of the order of 10- 5 mm Hg.
  • low pressure atmospheric pressure pressing against the external surface of the viewing window exerts forces totaling about 1800 kilograms.
  • Circumferential tensile stresses as high as 70 kg/cm 2 are present in the sidewall 29 and the adjacent portions of the funnel. Should the viewing window fracture, atmospheric pressure would ordinarily drive window fragments inward against the funnel portion 25, from which they would then bounce outward.
  • An implosion-protection system does not prevent such implosion but, instead, reduces the chance of injury to viewers near the tube face. Particularly, an implosion-protection system reduces the amount of glass fragments thrown and reduces the distances that they are thrown.
  • a continuous peripheral film coating 39 of polyurethane about 0.125 mm (5 mils) thick is adhered to external surface portions of the sidewall 29 and the funnel 25 on each side of the seal 31.
  • the film coating 39 is about 12.5 cm wide, extending from the seal about 5 cm toward the window 27 and 7.5 cm toward the neck 23. Should the window 27 fracture, the film coating 39 adherent to external envelope surfaces maintains the adjacent glass in place while permitting gas to rush into the tube, reducing the pressure differential on opposite sides of the window 27, thereby reducing the forces which drive glass fragments into flight.
  • the film coating 39 in the embodiment of Figure 1 is fabricated on the tube after the envelope 21 has been completely evacuated of gases and sealed, and the electrodes of the gun 33 have been electrically processed.
  • a quantity of an emulsion of polyurethane in a water base is diluted with water to the desired viscosity.
  • One suitable polyurethane emulsion is RS 5302 marketed by PPG Industries, Coatings and Resin Products Division, Springdale, Pa., U.S.A.
  • the mixture is then brushed, flowed or preferably sprayed on the desired areas using a stencil to define such areas.
  • the emulsion-coating thickness When spraying on the emulsion, it has been found to be convenient to monitor the emulsion-coating thickness by including a water-soluble dye, such as Hldrocal Alpha Blue, marketed by Hercules, Inc., Glen Falls, N.Y., U.S.A., in the emulsion.
  • a water-soluble dye such as Hldrocal Alpha Blue
  • Hercules, Inc. Glen Falls, N.Y., U.S.A.
  • the emulsion is applied to a depth of color corresponding to the desired thickness.
  • fluorescent light is used and reflectance measurements are taken with a blue and with a red filter. The thicker the coating, the higher the blue-to-red ratio of these reflectances.
  • the emulsion coating is dried and the solids therein coalesced to a substantially uniform film.
  • This 'curing' of the film may be done by heating the tube in an oven in an ambient of air at about 20° to 120°C for about 30 to 5 minutes, preferably about 90°C for about 10 minutes, and then cooling the tube.
  • the tube may be pre-heated in an oven to about 20° to 90°C, preferably about 50°C, prior to applying the emulsion coating.
  • the film is at least 0.075 mm (3 mils) thick and preferably about 0.125 mm (5 mils) thick. Greater thicknesses are not detrimental to implosion protection, although too thick a film results in excessive material costs. It is surprising that, without reinforcement by fabric or other fibrous material in the films, sufficient protection can be realized with such thin films and with the use of so little polymeric material.
  • FIGs 2 and 3 are identical in structure to that of Figure 1 except for the extent of the film coating 39. Hence, similar reference numerals are used for similar structures.
  • a film coating 39a extends back on the funnel 25 almost to the neck 23.
  • An open area 41 is left around the anode button 43 to permit the connection of a high-voltage lead thereto.
  • a film coating 39c is shortened so that it lies only on the panel sidewall and does not extend over the seal 31 or the window 27. Even though the coating 39c is narrow, it nevertheless provides implosion protection that is adequate for many tubes, particularly when used in combination with one or more tensioned steel bands.
  • FIGs 4 and 5 are identical in structure to that of Figure 1 except that one or more continuous steel bands are tensioned to about 450 to 675 kilograms around the sidewalls 29 of the panel; plastic coated bands are preferred. Hence, similar reference numerals are used for similar structures.
  • a band 45 and a metal clip 47 are on top of a film coating 39d.
  • a band 49 and a metal clip 51 are under the film coating 39c.
  • Two tensioned bands, one on top of the other, may also be used over or under the film coating.
  • Adhesive strengths of polyurethane films to glass were determined by applying emulsions by draw-down blade or by spray to nonmold- released glass plates. After being outlined with a cutting tool, one end of a 2 inch (about 50 mm) strip was reinforced and attached to a spring scale and pulled off the plate at a 90° angle according to the ASTM method. This pull test was repeated on external funnel and sidewall surfaces of cathode-ray tubes. Pull test results averaged about 4.5 kilograms on funnel surfaces and about 6.4 kilograms on sidewall surfaces. These results are much higher than the minimum of about 1.4 kilograms considered necessary for adequate implosion protection.
  • polyurethane latexes that is, aqueous emulsions or sols in which each colloidal particle contains a number of macromolecules of polyurethane.
  • the colloidal particles are about 0.05 to 1.0 micron, preferably less than 0.3 micron, in average size.
  • the latexes are ones from which the water base can be removed and the macromolecules coalesced into an adherent film coating on a glass surface.
  • Other aqueous emulsions of polymeric materials have been tried, but only polyurethane has been found to develop sufficient tensile strength and adherence in coalesced film coatings.
  • the colloidal particles of the latexes should have a relatively low minimum film- forming temperature, or MFT preferably more than 20°C below the temperatures at which curing is carried out.
  • the latexes may include other constituents, such as a coloring dye, a defoaming agent and/or a stabilizing agent.
  • 19V and 25V tubes are tubes having viewing areas with nominal diagonal dimensions of 19 inches (about 48 cm) and 25 inches (about 63.5 cm) respectively.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
  • Laminated Bodies (AREA)
EP78300859A 1977-12-27 1978-12-19 Cathode ray tube with implosion protection and method for manufacturing it Expired EP0002926B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US86476277A 1977-12-27 1977-12-27
US864762 1977-12-27

Publications (2)

Publication Number Publication Date
EP0002926A1 EP0002926A1 (en) 1979-07-11
EP0002926B1 true EP0002926B1 (en) 1982-02-03

Family

ID=25344012

Family Applications (1)

Application Number Title Priority Date Filing Date
EP78300859A Expired EP0002926B1 (en) 1977-12-27 1978-12-19 Cathode ray tube with implosion protection and method for manufacturing it

Country Status (11)

Country Link
EP (1) EP0002926B1 (fi)
JP (1) JPS5497359A (fi)
AT (1) AT376063B (fi)
AU (1) AU4212678A (fi)
CA (1) CA1120990A (fi)
DD (1) DD141221A5 (fi)
DE (1) DE2861614D1 (fi)
FI (1) FI783920A (fi)
IT (1) IT1101089B (fi)
MX (1) MX4477E (fi)
PL (1) PL129652B1 (fi)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57191946A (en) * 1981-05-21 1982-11-25 Toshiba Corp Explosion-proof cathode-ray tube
DE3515167A1 (de) * 1985-04-26 1986-10-30 Siemens AG, 1000 Berlin und 8000 München Verfahren zur herstellung eines metallischen koerpers aus einer amorphen legierung

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3184327A (en) * 1962-07-17 1965-05-18 Gen Electric Implosion resistant cathode ray tubes
FR1349346A (fr) * 1962-12-04 1964-01-17 Perfectionnement aux tubes électroniques et procédé pour la fabrication de ces tubes
FR1355737A (fr) * 1963-02-07 1964-03-20 Loing Verreries Perfectionnement à la protection d'appareils tels que tubes de télévision, contre les implosions
NL6612938A (fi) * 1966-09-14 1968-03-15
DE1564507B1 (de) * 1966-09-15 1971-03-11 Philips Patentverwaltung Verfahren zur herstellung eoner implosionsgeschuetzten elektronenstrahlroehre insbesondere fernsehbildroehre
JPS50110080U (fi) * 1974-02-14 1975-09-08

Also Published As

Publication number Publication date
PL212044A1 (pl) 1979-08-27
MX4477E (es) 1982-05-18
CA1120990A (en) 1982-03-30
ATA912978A (de) 1984-02-15
AU4212678A (en) 1979-07-05
PL129652B1 (en) 1984-05-31
IT7831295A0 (it) 1978-12-22
IT1101089B (it) 1985-09-28
EP0002926A1 (en) 1979-07-11
JPS5497359A (en) 1979-08-01
JPS616971B2 (fi) 1986-03-03
DE2861614D1 (en) 1982-03-11
DD141221A5 (de) 1980-04-16
FI783920A (fi) 1979-06-28
AT376063B (de) 1984-10-10

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