US3898508A - Temperature compensated shadow mask for a color cathode-ray tube - Google Patents

Temperature compensated shadow mask for a color cathode-ray tube Download PDF

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Publication number
US3898508A
US3898508A US785171A US78517168A US3898508A US 3898508 A US3898508 A US 3898508A US 785171 A US785171 A US 785171A US 78517168 A US78517168 A US 78517168A US 3898508 A US3898508 A US 3898508A
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Prior art keywords
frame
tube
springs
mask
image area
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Expired - Lifetime
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US785171A
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English (en)
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Nicholas P Pappadis
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Zenith Electronics LLC
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Zenith Radio Corp
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Priority to US785171A priority Critical patent/US3898508A/en
Priority to GB1232728D priority patent/GB1232728A/en
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Assigned to FIRST NATIONAL BANK OF CHICAGO, THE reassignment FIRST NATIONAL BANK OF CHICAGO, THE SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ZENITH ELECTRONICS CORPORATION A CORP. OF DELAWARE
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Assigned to ZENITH ELECTRONICS CORPORATION reassignment ZENITH ELECTRONICS CORPORATION RELEASED BY SECURED PARTY (SEE DOCUMENT FOR DETAILS). Assignors: FIRST NATIONAL BANK OF CHICAGO, THE (AS COLLATERAL AGENT).
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    • 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
    • H01J29/07—Shadow masks for colour television tubes
    • H01J29/073—Mounting arrangements associated with shadow masks

Definitions

  • the shadow mask of the tube type under consideration is the mechanism for attaining color selection. It has essentially the same size and shape as the image area of the tube and is positioned in close parallel relation therewith. Its function is to confine each electron beam issuing from the gun mount and reaching the screen through the shadow mask to impinge only on those elements of the screen which emit light of the particular color to which that beam and the gun creating it have been assigned.
  • the screen is a mosaic of triads of deposits of green, blue and red emitting phosphors and there are three guns in the gun mount one of which excites the green phosphor dots while the remaining two excite only the blue and red dots, respectively, this being accomplished by the aperture pattern of the mask or colorselection electrode.
  • this electrode intercepts a significant portion of each beam and experiences a substantial increase in temperature as the tube achieves operating temperature. It is not uncommon for the mask to rise to a temperature of 80 C.
  • the structural components of the color-selection electrode will obviously expand in the face of such an increase in temperature ambient. Such expansion, for the case of a thermally uncompensated structure, causes the apertures of the mask to be displaced transversely of the intended beam paths and results in misregistration of the beams with the dots of the phosphor triads. Since the temperature rise can hardly be avoided, it is necessary to take steps to minimize misregistration and a number of proposals have been made to confine movement of the electrode structure along the intended paths of the beams.
  • One prior structure features connecting the conventional leaf springs of the color-selection electrode to the mask frame through a bimetallic coupling structure having one base portion of a low coefficient of expansion, another base portion of a relatively high coefficient of expansion and an expansion loop for interconnecting these base portions. While these structures are more or less successful in reducing misregistration, they are objectionable because they increase the complexity of the tube structure and add significantly to its fabricating costs.
  • the invention is in a color cathode-ray tube having a faceplate section including a rectangular image area bearing deposits of three different phosphor materials defining a multiplicity of phosphor triads, a flange normal to the periphery of the image area, and support pins extending inwardly of the flange on both sides and/or the top and bottom of the tube envelope.
  • the tube further has a color-selection electrode of essentially the same size and shape as the image area and which includes a mask component having a field of apertures individually aligned with an assigned one of the phosphor triads. This electrode further includes a frame normal to the mask component and to which the peripheral portion of that component is attached.
  • an improved arrangement for mounting the color-selection electrode in spaced parallel relation to the image area of the tube comprises a pair of similar elongated leaf springs secured at one end to corresponding points on opposing side portions of the frame and having an aperture at the opposite end dimensioned to accept the support pins of the envelope and form a pivoted connection therewith.
  • the springs face the same direction with respect to the top of the frame and bridge the space between the frame and the pins of the tube.
  • the springs are individually formed of two metallic pieces having different temperature coefficients of expansion, arranged in side-by-side abutting relation with the piece of higher temperature coefficient closer to the image area and mechanically fastened to one another along their abutting surfaces.
  • the length of each spring is proportioned, in relation to the aforesaid difference in the co efficients of expansion, to effect pivotal movement of the springs about their associated pins and axial displacement of the frame toward the image area as the tube attains its operating temperature.
  • FIG. I is a schematic representation of a color cathode-ray tube having thermal compensation in accordance with the subject invention.
  • FIG. 2 is an enlarged fragmentary portion of the tube of FIG. 1 showing with greater particularity details of the mask structure
  • FIG. 3 is a sectional view taken on line 3-3 of FIG.
  • FIGS. 4 and 5 are enlarged detailed views of the terminal portion of mounting springs which includes its mounting aperture.
  • the cath ode-ray tube there represented is of the well-known shadow mask type and has an envelope l0 terminating at one end in a faceplate section 11. It will be assumed that the tube is of the 23-inch, degree variety having a rectangular image area bearing deposits 12 of different phosphor materials. While the phosphor deposits may be in the form of stripes, it is customary that they be clusters of dots forming the now familiar dot triads and it will be assumed that screen 12 is of this type. In such a case the elements of each triad are deposits of green, blue, and red emitting phosphors and the screen is backed by a conductive and light reflecting layer 13 of aluminum which is sufficiently thin to be electron permeable.
  • Faceplate section 11 additionally includes a flange 11a that projects from and is substantially normal to the periphery of screen 12 and its internal dimensions exceed the dimensions of the screen.
  • Support pins by means of which the shadow mask is removably installed within faceplate section 11 extend inwardly from flange 11a on both sides and also on the top and/or the bottom of the tube, depending on whether one wishes to employ a three or four-point suspension of the shadow mask. For convenience, a three-point arrangement will be assumed in which case the tube has support pins on both sides of flange 11a and in the central portion of the top.
  • One such pin 14 is shown in the enlarged view of FIG. 3.
  • the color-selection electrode or parallax barrier 15 of the tube is essentially the same size and shape as screen 12 and has maximum dimensions that are only slightly less than the internal dimensions of tube flange 11a.
  • the color-selection electrode includes a component 16 with electron transparent and electron opaque portions for admitting electrons to selected portions of screen 12. Where the screen is a mosaic of phosphor dots, as has been assumed, this component is the now familiar mask having a field of apertures with each aperture essentially in alignment with one triad of the screen. Obviously, the apertures are electron transparent and the interconnecting mask structure is opaque.
  • the color-selection electrode also has a frame component 17 with a portion 17a extending parallel to the tube axis or perpendicular to mask 16 and to which the peripheral portion of the mask is attached as by welding.
  • the frame further has a portion 17b disposed in normal relation to both the tube axis and to frame portion 170.
  • This assembly of mask 16 and frame 17 is removably installed within faceplate structure 11 by leaf springs to be considered more particularly hereafter. For present purposes they may be considered simply as flexible coupling elements affixed to frame 17 with apertures in their free ends to receive mounting pins 14 extending inwardly of the tube envelope.
  • the customary gun mount 18 for directing at least one beam along a desired path to screen 12.
  • this mount is a cluster of three guns each of which issues a beam which, in traversing shadow mask 16, impinges only on phosphor elements of an assigned color as these beams are caused to scan the image area of the tube. Since the tube, as thus far described, is totally conventional both as to its structure and mode of operation, it is not necessary to develop this matter further. Instead, the remainder of the description will be directed to the details of mounting springs 20 and the thermal stabiliza- .tion or compensation they afford.
  • frame 17 is secured to faceplate section 11 by means of a three-point suspension in which three leaf springs affixed to the mask engage three support pins provided in the envelope.
  • One such spring is positioned essentially in the central top portion of frame 17 with one end welded to the frame and the other end apertured to accept the support pin extending inwardly from the top central portion of the tube envelope.
  • the other two springs are welded to corresponding points on the sides of frame 17 and both face upward. that is to say, the end of each spring closer to the bottom of the frame is welded to the frame and the free end of each spring is closer to or faces the top of the frame.
  • the three springs are structurally alike and one of them is shown in the en' larged fragmentary views of FIGS. 2 to 5.
  • Each spring is formed of two metallic components 20a and 2012 having specifically different coefficients of expansion.
  • Component 20a which is closer to screen 12, has a relatively high coefficient of expansion while component 20b, which is closer to gun mount 18, has zero or a relatively low coefficient of expansion.
  • the mounting spring is formed at one end 20d to rest flush against a portion of frame component 17a that is to be positioned in spaced parallel relation to the inner wall of the tube envelope.
  • the other or free end of the spring structure has an aperture 200 that is dimensioned to accept support pin 14 and form a pivoted connection therewith. Thermal stability is best achieved if each of the side springs faces in the same direction, whether they both face the top, as shown, or face the bottom of frame 17.
  • the specific point of attachment to the frame is chosen to properly present the aperture 200 of each spring to its associated support pin 14.
  • the portion of spring 20 extending from its weld to frame portion 17a is outwardly biased and subtends an acute angle B therewith, being configured to bridge the space between the frame and support pin 14.
  • each spring 20 is oriented in relation to screen area 12 to translate the greater expansion of one of its metallic components, experiencd to response in an increase in temperature, to pivoted movement of the spring about its associated pin 14 and axial displacement of frame 17 toward screen 12. More particularly, as the tube is brought to a stable operating temperature, the mask-frame assembly increases in temperature causing its component parts to expand. Expansion of frame 17, for example, tends to compress springs 20, especially those attached to the sides of the frame. Additionally, these springs tend to expand but component 20]; having zero or a low coefficient of expansion resists elongation of the spring and movement of the apertures of mask 16 in a vertical plane.
  • each spring 20 is proportioned, in relation to the difference in coefficients of expansion of its components, to the end that electrons having access to screen 12 through mask 16 impact substantially the same selected portions of the screen at all times, even as the tube, having been energized, attains its operating temperature. That is to say, the proportioning maintains the beams in substantial register with their assigned phosphor dots even though the temperature of the mask structure increases significantly during the first one to two hours of the tube operation.
  • This desired condition is established by constructing springs 20 to cause a particular amount of axial displacement of mask structure per degree rise in temperature to displace the mask assembly essentially along the paths of the electron beams and this is rather easily measured or readily determined empirically.
  • a preferred structure of the bimetallic mounting spring is one in which equal lengths of components 200 and 2012 are butt welded to one another. Maximum deflection per degree temperature rise is achieved if only component a, having the higher coefficient of expansion, is welded to mask section 170 as indicated at the points 20e. It is also preferred that the mounting aperture 20c be formed in component 20a. Where the mounting pin 14 is circular in cross section, as represented in FIG. 2, it is preferred to have aperture 200 formed of a first radius r, with cutouts of a radius r as indicated in FIG. 4. And to enhance the pivotal action, it is desirable to countersink or coin the aperture at an angle 0, see FIG. 5.
  • Thickness of spring 0.05 inch.
  • this arrangement maintains the mechanical stability inherent in prior art mounting springs which were of the same structural design but lacking thermal compensation.
  • This arrangement maintains the mechanical stability inherent in prior art mounting springs which were of the same structural design but lacking thermal compensation.
  • the attachment to that portion of the frame causes the system to be undesirably susceptible to microphonics which is avoided in the described structure wherein the spring attaches to the portion of the frame that is parallel to the sides of the tube envelope.
  • support pins are affixed to the tube to be received in apertures in the mounting springs but, obviously the reverse arrangement may be employed with the invention, if desired.
  • a color cathode-ray tube having a faceplate section including (a) a rectangular image area bearing deposits of three different phosphor materials defining a multiplicity of phosphor triads, (b) a flange normal to the periphery of said area and (c) support pins extending inwardly from said flange on both sides and on the top and/or bottom of said tube, further having a colorselection electrode of essentially the same size and shape as said image area including (d) a mask component having a field of apertures individually aligned with an assigned one of said triads and (e) a rectangular frame of angular cross section having one part parallel to the axis of the tube to which the peripheral portion of said mask is attached and having another part disposed transverse to said axis, and also having an improved arrangement for mounting said electrode in spaced parallel relation to said image area comprising: a pair of similar elongated leaf springs individually formed of two metallic pieces having different temperature coefficients of expansion, arranged in side-by
  • said springs being secured at one end to said frame by means of weld connections made only to corresponding points on opposing side portions of said one part of said frame, said springs being contoured to bridge the space between said frame and said support pins on the side portions of said faceplate flange and having an aperture at the opposite end dimensioned to accept said support pins and form a pivoted connection therewith,
  • each of said springs being proportioned in relation to the aforesaid difference in coefficients of expansion to effect pivotal movement of said springs about their associated pins and axial displacement of said frame toward said image area as the tube attains its operating temperature.

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  • Electrodes For Cathode-Ray Tubes (AREA)
US785171A 1968-12-19 1968-12-19 Temperature compensated shadow mask for a color cathode-ray tube Expired - Lifetime US3898508A (en)

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US785171A US3898508A (en) 1968-12-19 1968-12-19 Temperature compensated shadow mask for a color cathode-ray tube
GB1232728D GB1232728A (enrdf_load_stackoverflow) 1968-12-19 1969-11-26

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US785171A US3898508A (en) 1968-12-19 1968-12-19 Temperature compensated shadow mask for a color cathode-ray tube

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4164682A (en) * 1976-01-05 1979-08-14 Zenith Radio Corporation Shadow mask suspension system having bracket means integrally formed from the shadow mask assembly
US4491763A (en) * 1982-08-31 1985-01-01 Tokyo Shibaura Denki Kabushiki Kaisha Color picture tube with shadow mask supporting members
US4524298A (en) * 1983-07-05 1985-06-18 North American Philips Consumer Electronics Corp. Color cathode ray tube incorporating improved thermal compensation type aperture mask supporting means
US4593225A (en) * 1984-08-31 1986-06-03 Zenith Electronics Corporation Tension mask colar cathode ray tube
US4614892A (en) * 1984-08-31 1986-09-30 Zenith Electronics Corporation Tension mask mounting structure
US4659958A (en) * 1985-09-24 1987-04-21 Rca Corporation Support means for use with a low expansion color-selection electrode
US4721488A (en) * 1986-02-21 1988-01-26 Zenith Electronics Corporation Apparatus for tensing a shadow mask foil
US4721879A (en) * 1983-09-30 1988-01-26 Zenith Electronics Corporation Tensed mask cathode ray tube
US5030154A (en) * 1983-09-30 1991-07-09 Zenith Electronics Corporation Method of mounting tensed CRT mask
US5066886A (en) * 1989-10-31 1991-11-19 Carpenter Technology Corporation Thermally responsive article, method of making same, and a device incorporataing said article
US5502350A (en) * 1993-07-05 1996-03-26 Hitachi Metals Ltd. Shadow mask support member having high strength and thermal deformation resistant low-expansion alloy plate and high expansion alloy plate and method of producing the same

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3308327A (en) * 1964-06-12 1967-03-07 Rca Corp Cathode ray tube
US3449611A (en) * 1966-06-22 1969-06-10 Nat Video Corp Suspension system for color television tube mask
US3454813A (en) * 1968-09-12 1969-07-08 Admiral Corp Mask-frame captivator
US3573527A (en) * 1968-02-08 1971-04-06 Gerardus Antonius Hafkenscheid Shadow mask supported by bimetallic spring comprising coplanar strips with different coefficients of expansion

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3308327A (en) * 1964-06-12 1967-03-07 Rca Corp Cathode ray tube
US3449611A (en) * 1966-06-22 1969-06-10 Nat Video Corp Suspension system for color television tube mask
US3573527A (en) * 1968-02-08 1971-04-06 Gerardus Antonius Hafkenscheid Shadow mask supported by bimetallic spring comprising coplanar strips with different coefficients of expansion
US3454813A (en) * 1968-09-12 1969-07-08 Admiral Corp Mask-frame captivator

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4164682A (en) * 1976-01-05 1979-08-14 Zenith Radio Corporation Shadow mask suspension system having bracket means integrally formed from the shadow mask assembly
US4491763A (en) * 1982-08-31 1985-01-01 Tokyo Shibaura Denki Kabushiki Kaisha Color picture tube with shadow mask supporting members
US4524298A (en) * 1983-07-05 1985-06-18 North American Philips Consumer Electronics Corp. Color cathode ray tube incorporating improved thermal compensation type aperture mask supporting means
US4721879A (en) * 1983-09-30 1988-01-26 Zenith Electronics Corporation Tensed mask cathode ray tube
US5030154A (en) * 1983-09-30 1991-07-09 Zenith Electronics Corporation Method of mounting tensed CRT mask
US4593225A (en) * 1984-08-31 1986-06-03 Zenith Electronics Corporation Tension mask colar cathode ray tube
US4614892A (en) * 1984-08-31 1986-09-30 Zenith Electronics Corporation Tension mask mounting structure
US4659958A (en) * 1985-09-24 1987-04-21 Rca Corporation Support means for use with a low expansion color-selection electrode
US4721488A (en) * 1986-02-21 1988-01-26 Zenith Electronics Corporation Apparatus for tensing a shadow mask foil
US5066886A (en) * 1989-10-31 1991-11-19 Carpenter Technology Corporation Thermally responsive article, method of making same, and a device incorporataing said article
US5502350A (en) * 1993-07-05 1996-03-26 Hitachi Metals Ltd. Shadow mask support member having high strength and thermal deformation resistant low-expansion alloy plate and high expansion alloy plate and method of producing the same

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Publication number Publication date
GB1232728A (enrdf_load_stackoverflow) 1971-05-19

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AS Assignment

Owner name: FIRST NATIONAL BANK OF CHICAGO, THE

Free format text: SECURITY INTEREST;ASSIGNOR:ZENITH ELECTRONICS CORPORATION A CORP. OF DELAWARE;REEL/FRAME:006187/0650

Effective date: 19920619

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Owner name: ZENITH ELECTRONICS CORPORATION

Free format text: RELEASED BY SECURED PARTY;ASSIGNOR:FIRST NATIONAL BANK OF CHICAGO, THE (AS COLLATERAL AGENT).;REEL/FRAME:006243/0013

Effective date: 19920827