EP0217473A2 - Farbbildröhre mit innerer magnetischer Abschirmung - Google Patents

Farbbildröhre mit innerer magnetischer Abschirmung Download PDF

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Publication number
EP0217473A2
EP0217473A2 EP86201680A EP86201680A EP0217473A2 EP 0217473 A2 EP0217473 A2 EP 0217473A2 EP 86201680 A EP86201680 A EP 86201680A EP 86201680 A EP86201680 A EP 86201680A EP 0217473 A2 EP0217473 A2 EP 0217473A2
Authority
EP
European Patent Office
Prior art keywords
cathode ray
aperture
ray tube
shield
axis
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP86201680A
Other languages
English (en)
French (fr)
Other versions
EP0217473A3 (en
EP0217473B1 (de
Inventor
Richard Irwin Brown
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.)
Philips North America LLC
Original Assignee
North American Philips Consumer Electronics Corp
US Philips Corp
North American Philips 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 North American Philips Consumer Electronics Corp, US Philips Corp, North American Philips Corp filed Critical North American Philips Consumer Electronics Corp
Publication of EP0217473A2 publication Critical patent/EP0217473A2/de
Publication of EP0217473A3 publication Critical patent/EP0217473A3/en
Application granted granted Critical
Publication of EP0217473B1 publication Critical patent/EP0217473B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/06—Screens for shielding; Masks interposed in the electron stream

Definitions

  • This invention relates to color cathode ray tubes having aperture masks, and more particularly relates to improved internal magnetic shields for such tubes.
  • Color cathode ray tubes for color television (color picture tubes) employing aperture masks are known to be sensitive to external magnetic fields, especially the earth's magnetic field, which can undesirably influence the trajectories of the electron beams, causing shifting and distortion of the screen raster, as well as degradation of colour purity and convergence. For example, shifting of a beam trajectory to the right or left will result in a beam landing error in a tube with vertically oriented phosphor stripes. That is, the beam will land to the right or left of the intended landing area on the stripe.
  • these shields are customarily fabricated from a soft magnetic material, such as low carbon steel, enabling ready remagnetization each time the television set is turned on.
  • the shape of the shield is in general dictated by the desire to have as much of the tube volume shielded as possible, without having the shield interfere with the tube's operation. For example, extending the shield too far back into the funnel risks interference with the magnetic deflection field for the electron beams, as well as physical interception or "clipping" of the deflected beams. In addition, cost considerations dictate as simple a shape as possible.
  • the shield is composed of two curved sheets of magnetic material, said to make processing, storing, transportation and assembly convenient and easy.
  • an external shield is employed to cover the gaps created by the opening between the two curved sheets "to provide complete shielding".
  • the effect of the earth's magnetic field on beam landing interms of two components is customary to describe the effect of the earth's magnetic field on beam landing interms of two components; the east-west effect, determined by a transverse horizontal field, and the north-south effect, determined by an axial horizontal field.
  • the magnitude of these effects is the difference between the beam landing errors in the east and west-facing directions, and the north and south-facing directions, respectively.
  • the tube's surface in terms of the face of an analog clock. Thus, the top is 12 o'clock, the bottom is 6 o'clock, the right side (as seen by the viewer) is 3 o'clock and the left side is 9 o'clock.
  • an improved internal magnetic shield for a color tube comprising a bowl-shaped structure having at least one slot-shaped opening in both the 6 and 12 o'clock sides of the shield, each slot aligned in the direction of the axis of rotation or Z axis of the tube, and a large aperture surrounding the Z axis for passing the tube's electron beams.
  • such an improved shield is fabricated by first cutting slots into a foil sheet of soft magnetic material, such as low carbon steel, and then forcing the sheet over a bowl-shaped form to simultaneously stretch and crimp the sheet into a bowl-shaped structure. Subsequently, an aperture is cut into the shield.
  • cathodoluminescent screen 21 Disposed on the interior surface of face panel 15 is cathodoluminescent screen 21, consisting of an array of discrete phosphor elements.
  • mount 22 Positioned in the neck 19 is mount 22 including an electron gun for generating and directing three electron beams to screen 21.
  • mount 22 Positioned adjacent screen 21 is a multi-apertured mask 25 for directing the electron beams to the desired phosphor elements on the screen.
  • Aperture mask 25 is supported by frame member 29, which is in turn supported by studs 27 embedded in the sidewall of panel 15.
  • IMS internal magnetic shield
  • the bowl-shaped structure 39 of shield 31 extends from the periphery of the mask 25 downward along the funnel 17 toward the mount 22, generally followingthe contour of the funnel wall, until it terminates in a mid-region between the mask and mount to define aperture 47. While a further extension of the shield would result in improved shielding, it would also present the risk of interference with the magnetic beam deflection field produced by external deflection means (not shown) positioned in the transition region between the funnel and the neck, as well as actual physical interception (clipping) of the electron beams.
  • the shield 31 is seen in plan view from the rear or mount end of the tube, as viewed along the Z axis.
  • the top, left side, bottom, and right side of the shield are labeled the 12, 3, 6 and 9 o'clock sides, respectively.
  • the slots 41a and 41b are located in the centres of the 6 and 12 o'clock sides.
  • the slots may also be located off-center, for example within a central region of the 6 and 12 o'clock sides, this region defined as extending up to 40 percent of the length La ofthe aperture. There may also be more than one slot in a sidewall, but preferably there will be the same number of slots in each sidewall. In addition, the facing slots need not be superjacent as shown, but may be displaced relative to one another, within the central region defined.
  • the slots have a height h which is from about 50 to 95 percent of the height Hs of the shield from the rim 48 to the straight edge 49 of the aperture 47, and a width w which is from about 1 to 10 percent of the length Lr of the shield at the rim 48.
  • the aperture 47 is oblong-shaped, having a length-to-width ratio of from about 1.7 to 2.1, and having a central region defined by straight edges 49 and two end regions defined by curved edges 50. As may be seen more clearly in Figs. 1 and 3, the central region of the aperture lies in a plane normal to the Z axis, while the end regions lie in upwardly curving surfaces, resulting in the curved edge profile seen in Fig. 3.
  • the aperture has a width Wa which is from about 49 to 51 percent of the width Wr of the shield at the rim 48, and a length La which is from about 65 to 69 percent of the length Lr.
  • the amount of upward is from about 49 to 51 percent of the width Wr of the shield at the rim 48, and a length La which is from about 65 to 69 percent of the length Lr.
  • curvature of the end regions of the aperture, resulting from the intersection of the bowl-shaped sidewalls with the oblong-shaped aperture, is indicated by the height He of the shield from the rim 48 to the outer point 52 of curved edge 50, and this height Hc may range from about 85 to 90 percent of the height Hs.
  • the aperture has a larger length-to-width ratio than the apertures of certain prior shield designs (about 2 versus 1.3). This change has the effect of improving north-south shielding, but at the expense of slightly reduced east-west shielding. East-west shielding is at least partially recovered, however, by introducing the slots into the 6 and 12 o'clock sidewalls.
  • 19V mini neck color tubes having a shield of the invention and a prior art shield were fabricated and compared for registration differences.
  • Registrations were measured on several sample tubes for each type mf shield and averaged. Measurements were taken at the four corners ofthe screen for each sample tube oriented successively in the west, south, east, north and west directions. Registration differences between north and south facing orientations averaged about 0.6 mils or is less for the inventive shield versus about 1.2 mils for the prior art hield. Registration differences between east and west facing orientations averaged about 0.6 mils for the inventive shield versus about 0.5 mils for the prior art shield. The significant improvement in north-south shiel-. ding at the expense of a slight decrease in east-west shielding resulted in a beneficial correction of the effects of external magnetic fields, and a consequent overall improvement in tube performance.
  • the shield is fabricated from a foil sheet of soft magnetic material, such as low carbon steel.
  • the sheet is shaped by forcing it over a mold, resulting in simultaneously stretching and crimping it into the desired shape.
  • the crimps are represented in the drawings by the randomly distributed loopedand wavy lines.
  • the slots are preferably formed before shaping (such as by cutting or punching) because after shaping the slots lie in a curved surface and forming in such a surface is more difficult than in a flat surface. Because the slots are located in an area of the foil which undergoes considerable stretching during shaping, it is important that the slots adhere to the dimensional and other limitations set forth herein, in order to avoid tearing of the foil or deformation of the slots or both, during shaping. For the same reasons, the aperture is preferably formed after shaping.

Landscapes

  • Electrodes For Cathode-Ray Tubes (AREA)
  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
EP86201680A 1985-10-03 1986-09-30 Farbbildröhre mit innerer magnetischer Abschirmung Expired - Lifetime EP0217473B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US78388585A 1985-10-03 1985-10-03
US783885 1985-10-03

Publications (3)

Publication Number Publication Date
EP0217473A2 true EP0217473A2 (de) 1987-04-08
EP0217473A3 EP0217473A3 (en) 1988-01-07
EP0217473B1 EP0217473B1 (de) 1991-01-30

Family

ID=25130704

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86201680A Expired - Lifetime EP0217473B1 (de) 1985-10-03 1986-09-30 Farbbildröhre mit innerer magnetischer Abschirmung

Country Status (5)

Country Link
EP (1) EP0217473B1 (de)
JP (1) JP2588513B2 (de)
KR (1) KR870004484A (de)
CA (1) CA1270888A (de)
DE (1) DE3677310D1 (de)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0503709A2 (de) * 1991-03-08 1992-09-16 Koninklijke Philips Electronics N.V. Farbbildwiedergaberöhre mit innerer magnetischer Abschirmkappe
DE4219337A1 (de) * 1991-06-11 1992-12-17 Mitsubishi Electric Corp Farbkathodenstrahlroehre
EP0570065A1 (de) * 1992-05-15 1993-11-18 Koninklijke Philips Electronics N.V. Farbbildröhre mit innerer magnetischer Abschirmung
EP0650180A1 (de) * 1993-10-22 1995-04-26 Koninklijke Philips Electronics N.V. Farbbildröhre mit einer magnetischen Abschirmung
BE1007665A3 (nl) * 1993-10-22 1995-09-05 Philips Electronics Nv Kleurenbeeldbuis met magnetische afscherming.
GB2318906A (en) * 1996-10-31 1998-05-06 Lg Electronics Inc Shielding a CRT from the earth's magnetic field
GB2319887A (en) * 1996-11-30 1998-06-03 Lg Electronics Inc Cathode ray tubes
FR2824184A1 (fr) * 2001-04-27 2002-10-31 Thomson Licensing Sa Tube cathodique en couleurs avec blindage magnetique interne

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2000902A (en) * 1977-07-01 1979-01-17 Hitachi Ltd Colour picture tube
EP0090643A2 (de) * 1982-03-31 1983-10-05 Kabushiki Kaisha Toshiba Farbkathodenstrahlröhre

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5425157A (en) * 1977-07-27 1979-02-24 Matsushita Electronics Corp Color picture tube
JPS5525157A (en) * 1978-08-11 1980-02-22 Mitsubishi Electric Corp Signal transmitter
JPS5919619B2 (ja) * 1981-09-11 1984-05-08 松下電子工業株式会社 カラ−受像管用内部磁気シ−ルドの製造方法
JPS58178945A (ja) * 1982-04-15 1983-10-20 Toshiba Corp カラ−受像管
JPS5990161U (ja) * 1982-12-10 1984-06-19 株式会社東芝 カラ−受像管

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2000902A (en) * 1977-07-01 1979-01-17 Hitachi Ltd Colour picture tube
EP0090643A2 (de) * 1982-03-31 1983-10-05 Kabushiki Kaisha Toshiba Farbkathodenstrahlröhre

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0503709A3 (en) * 1991-03-08 1993-11-24 Philips Nv Colour display tube having an internal magnetic shield
EP0503709A2 (de) * 1991-03-08 1992-09-16 Koninklijke Philips Electronics N.V. Farbbildwiedergaberöhre mit innerer magnetischer Abschirmkappe
US5434470A (en) * 1991-03-08 1995-07-18 U.S. Philips Corporation Colour display tube having an internal magnetic shield
DE4219337C2 (de) * 1991-06-11 1998-02-26 Mitsubishi Electric Corp Farbkathodenstrahlröhre
US5336963A (en) * 1991-06-11 1994-08-09 Mitsubishi Denki Kabushiki Kaisha Color cathode-ray tube
DE4219337A1 (de) * 1991-06-11 1992-12-17 Mitsubishi Electric Corp Farbkathodenstrahlroehre
EP0570065A1 (de) * 1992-05-15 1993-11-18 Koninklijke Philips Electronics N.V. Farbbildröhre mit innerer magnetischer Abschirmung
EP0650180A1 (de) * 1993-10-22 1995-04-26 Koninklijke Philips Electronics N.V. Farbbildröhre mit einer magnetischen Abschirmung
BE1007665A3 (nl) * 1993-10-22 1995-09-05 Philips Electronics Nv Kleurenbeeldbuis met magnetische afscherming.
GB2318906A (en) * 1996-10-31 1998-05-06 Lg Electronics Inc Shielding a CRT from the earth's magnetic field
GB2318906B (en) * 1996-10-31 2001-09-05 Lg Electronics Inc Device for shielding earth magnetic field of a colour CRT
GB2319887A (en) * 1996-11-30 1998-06-03 Lg Electronics Inc Cathode ray tubes
GB2319887B (en) * 1996-11-30 2001-11-14 Lg Electronics Inc Rail structure of a cathode-ray tube
FR2824184A1 (fr) * 2001-04-27 2002-10-31 Thomson Licensing Sa Tube cathodique en couleurs avec blindage magnetique interne
WO2002089171A1 (en) * 2001-04-27 2002-11-07 Thomson Licensing S.A. Color cathode-ray tube having internal magnetic screening
US7064478B2 (en) 2001-04-27 2006-06-20 Thomson Licensing Color cathode-ray tube having internal magnetic screening

Also Published As

Publication number Publication date
CA1270888A (en) 1990-06-26
DE3677310D1 (de) 1991-03-07
JPS6288245A (ja) 1987-04-22
JP2588513B2 (ja) 1997-03-05
EP0217473A3 (en) 1988-01-07
KR870004484A (ko) 1987-05-09
EP0217473B1 (de) 1991-01-30

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