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
  • H01J29/07—Shadow masks for colour television tubes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2229/00—Details of cathode ray tubes or electron beam tubes
  • H01J2229/07—Shadow masks
  • H01J2229/0722—Frame

Definitions

• This invention relates to color cathode ray picture tubes, and is addressed to tubes having tension masks in conjunction with a curved faceplate.
• the invention is applicable to the manufacture of color tubes of various types, including those used in home entertainment type television receivers of both standard resolution and high definition, and in medium-resolution and high-resolution tubes used in color monitors.
• the shadow mask is a part of the cathode ray tube front assembly, and is located in close adjacency to the phosphor screen deposited on the inner surface of the faceplate.
• the term "shadow mask” means an apertured metal component that acts as a color-selection electrode, or "parallax barrier,” which ensures that each of the three beams generated by the electron gun located in the neck of the tube lands only on assigned phosphor targets.
• the mask is supported in predetermined distances from the inner surface of the face panel by structures known as “rails.” The predetermined distance is termed the "Q-height" or "Q-distance. "
• Prior art color cathode ray tubes having tensed foil shadow masks have faceplates which are flat to match the flatness of an associated foil mask.
• An exemplary tube of this type is fully described in our U.S. Patent No. 4,891,546.
• shadow mask types are categorized as (a) "slot" masks which are characterized by having the strips comprising the mask coupled by closely spaced ties which form the slots, (b) "slit” masks, in which the strips comprising the mask are not interconnected by ties, and which run untied the whole length of the mask; and (c), "tied slit” masks in which the strips are loosely coupled by widely spaced ties.
• An example of a widely used slot mask is one in which the slots are bridged by tie bars at frequent intervals. Typically, the spacing between the two tie bars in a given slot is of the same order as the center-to-center spacing between the two metal strips which form the slot. Due to the high density of tie bars, such a mask has very substantial mechanical strength in the transverse direction; i.e. at right angles to the major axis of the slots.
• the aperture structure of a mask of this type is depicted in figure 7.
• the wide tie spacing is such as to produce a strip coupling which promotes handleability of the mask during mask and tube fabrication.
• the wide strip coupling facilitates damping of strip vibration when mounted in the tube, but is insufficient to induce unacceptable Poisson contraction of the mask when it is uniaxially tensed along the direction of the strips in the plane of the mask or to permit unacceptable thermal expansion perpendicular to the strips.
• the mask is the subject of our U.S. Patent No.
• slit mask is one in which the mask is composed of a plurality of grille wires strung in close and parallel proximity between two supports.
• a mask of this type is the subject of U.S. Patent No. 2,842,696.
• a slit mask is one in which the mask is essentially a parallel array of narrow strips held together only at the ends and stretched over a strong, specially shaped frame so that the tensioned strips form a sector of a cylindrical surface. The tension ensures that all strips remain straight.
• This design has the disadvantage that each strip is capable of "vibrating independently, with very little damping. Conventionally, this deficiency is remedied by stretching one or several small diameter wires or fibers around the cylindrical surface, lightly touching all strips. (See U . S . Patent No . 3 , 638 , 063 . )
• the slit mask is one used in a post-mask-deflection color cathode ray tube wherein the mask is in the form of two intercalated combs providing mutually insulated first and second arrays of strips. Each of the arrays is adapted to receive a different electrical potential effective to cause the electron beams passing therethrough to be deflected by the electrical fields created between the strips.
• masks may be formed from metal foil having thicknesses in the range of
• foils are non-self-supporting so they must be installed in a highly tensed state.
• tension of a foil mask for a 29 cm (14-inch) (diagonal
• tube is about 2100 kg/cm (30 kpsi) .
• the amount of tension that must be applied will vary with the thickness of the foil and the size of the tube in which the mask is installed.
• Masks also may be formed from metal having a thickness in the range of 0.0076 to .02 cm
• the present invention therefore provides a tension mask color cathode ray tube having a faceplate with curved outer and inner surfaces, and with a tensed shadow mask located adjacent to said inner surface and secured to discrete mask support rails affixed to said inner surface, said rails having a curvature related to the curvature of said inner surface.
• the present invention further provides a tension mask color cathode ray tube having a cylindrical, skirted faceplate curved on a single axis oriented in the vertical direction, said faceplate having on its inner surface a centrally located screen with only two discrete support rails affixed to said inner surface and located on opposed sides said screen, said rails aligned in a horizontal direction and having a curvature related to the curvature of said inner surface, said rails providing for receiving and securing a shadow mask tensed in the vertical direction adjacent to said screen.
• One of the features of the invention is to provide a tensed shadow mask color cathode ray tube with a faceplate that has a greater resistance to atmospheric pressure than a flat faceplate.
• Figure 1 is a side view in perspective of a tension mask color cathode ray tube having a curved faceplate according to the invention; cutaway sections indicate the location and relationship of the major components of the tube.
• Figure 2 is a plan view of the front assembly of the color cathode ray tube of figure 1 taken from the aspect of the electron gun, and with parts cut away to show the relationship of the shadow mask with the faceplate and screen; an inset depicts the apertures (greatly enlarged) of a slot-type shadow mask.
• Figure 3 is a perspective view of the front assembly shown by figures 1 and 2, depicting discrete mask support rails affixed to the inner surface of the faceplate and having a curvature related to the curvature of the screen.
• Figure 4 is a view in elevation of the cross-section of the mask support rails depicted in figures 1-3.
• Figure 5 is a perspective view of a front assembly of a color cathode ray tube according to the invention in which the faceplate has a skirt.
• Figure 6 is a view in elevation showing the curvature of shadow mask support structure that provides for a predetermined variation in Q-height.
• Figure 7 is a perspective view of a prior art slot-type shadow mask for use in a color cathode ray tube according to the invention.
• Figure 8 is a view in perspective that depicts a section, greatly enlarged, of the prior art slot mask shown by figure 7.
• Figure 9 is a detail view of a mask comprising a plurality of grille wires.
• Figure 10 is a view in perspective showing a representative section of a mask that provides post-mask beam deflection.
• Figure 11 is a view in perspective of a representative section of a mask comprising a plurality of parallel strips.
• a curved-faceplate tension mask color cathode ray tube and its components is shown in figures 1-3, and is described in the following paragraphs in this sequence: reference number, a reference name, and a brief description of structure, interconnections, relationship, functions, operation, and/or result, as appropriate.
• centrally disposed phosphor screen consisting of a pattern of spaced vertical lines comprising a sequence of red-light-emitting, green-light-emitting and blue-light-emitting phosphors, the lines relating to the pattern of the slits or slots of the shadow mask 40 (described below); the lines are interspersed by a grille, or "black surround"
• the mask is mounted in tension of the mask support rails 38a and 38b by securing the mask aprons 40a and 40b to the support rails 38a and 38b; the apertures of the mask are depicted in the inset 42 as being distinctive of a slot mask
• gun 54 in-line electron gun enclosed in neck 52; gun 54 provides three discrete in-line beams 56, 58 and 60 for exciting the lines of red-light-emitting, green-light-emitting, and blue-light-emitting phosphors on screen 30
• shadow mask 40 is located adjacent to inner surface 26 of faceplate 24, indicated as being skirtless, and centrally located line screen 30.
• Mask 40 is secured to the discrete mask support rails 38a and 38b which are affixed to inner surface 26, and have a curvature related to the curvature of inner surface 26.
• the curvature of faceplate 24 will be noted as a curvature with respect to a single axis oriented in the vertical direction.
• Mask 40 is noted as being tensed in a vertical direction.
• the discrete mask support rails 38a and 38b comprise two rails located on opposed sides of centrally located screen 30. Rails 38a and 38b are aligned in a horizontal direction.
• Figure 4 is a detail view of the cross-section of rail 38a as mounted on faceplate 24 (rail 38b has the same structure) .
• the discrete rail 38a is affixed to the inner surface 26 of faceplate 24 by devitrified solder glass, the overflow of which is indicted by beads 70 and 72.
• a mask 40 is shown diagrammatically as being tensed by a mask-tensing fixture 74, with the direction of tensing indicated by arrow 76.
• the body of rail 38a is indicated symbolically as being composed of a ceramic.
• the function, structure and composition of the mask support rail 38a and its counterpart 38b is the subject of the aforesaid U.S. Patent No. 4,891,546.
• the mask support could as well comprise an all metal rail such as the mask support structure that is the subject of our U.S. Patent No. 4,891,544.
• a factory fixture frame that provides for mounting and tensing a shadow mask is described and claimed in our U.S. Patent No. 4,790,786.
• the frame described in the patent is designed to stretch a mask in both the horizontal and vertical directions; a simple modification of the apparatus will provide for stretching a mask, such as mask 40, in a single direction, such as the vertical direction.
• the apron 40a of the mask 40 is shown in contact with a first surface 80 of the metal cap 82 of rail 38a.
• a high-energy welding beam 84 indicated by the dotted line as being a pulsed beam, provides for welding the apron 40a of mask 40 to first surface 80 of rail 38a while mask 40 is under the tension provided by mask-tensing fixture 74.
• the welding line 86 which runs the entire length of rail 38a (and 38b), is indicated by the pattern of dots shown on apron 40a in figure 2.
• the high-energy beam is moved outwardly and becomes a continuous-wave mask-trimming beam 88 of higher power, indicated by the solid line.
• Mask-trimming beam 88 is focused on a trimming line 90 for severing the mask and releasing the front assembly 22 from the mask-stretching fixture 74.
• the trimming line 90 follows the approximate path of the dashed line shown.
• rail 38a has a second surface 92 which slopes outwardly and downwardly toward the inner surface 26 of faceplate 24 to define a non-zero angle in range of 40 to
• the shadow mask 40 shown is the tension mask described and claimed in the aforesaid U.S. Patent No.
• mask 40 comprises a series of parallel strips 100 separated by slits 102. Strips 100 are loosely coupled by widely spaced ties 104. As noted, and as indicated by figures 2 and 3, the mask is tensed uniaxially; in this case, tensed in the vertical direction.
• a foil mask as defined in this application is tensed uniaxially; in this case, tensed in the vertical direction.
• tension i.e., about 700 kg/cm (10 kpsi)
• the magnitude of tension is also a function of the size of the cathode ray tube in which it is used.
• Figure 5 depicts a front assembly for a tension mask color cathode ray tube having a cylindrical faceplate
• Mask 118 is tensed in the vertical direction and is secured to discrete mask support rails
• Faceplate 112 has a skirt 122 according to the invention.
• Figure 6 is a diagrammatic depiction of the profile of an alternate embodiment of a rail 123 as mounted on a faceplate 125.
• the rail 123 is shown as having a predetermined variance in Q-height according to the invention.
• the Q-height of rail 123 at its center is shown as having a predetermined variance in Q-height according to the invention.
• Figure 7 depicts the configuration of a prior art slot mask 130 described heretofore.
• Figure 8 depicts a detail of the structure of slot mask 130 in which the slots 132 are bridged by tie bars 134 at frequent intervals.
• the mask has a substantial mechanical strength in the transverse direction; that is, at right angles to the major axis of the slots.
• the slot mask 130 can be installed adjacent to the inner surface of a cylindrical faceplate curved on a single axis and secured to discrete mask support rails affixed to the inner surface of the faceplate. With reference to figure 3, the slot mask 130 can be ' installed in place of the mask 40.
• Slot mask 130 can be tensed in the vertical direction with
• mask 130 is largely self supporting, and there would be no need to provide support for the borders 136 and 138 of mask 130, as by additional mask support rails.
• a mask 142 comprising a plurality of grille wires 144 tensed in a vertical direction (the y-direction) between two mask support structures 146a and 146b.
• FIG 10 is a depiction of a representative section 150 of a mask support structure and two arrays of metal strips that provide for post-mask deflection of the electron beams.
• a ceramic mask support structure 152 has on its top surface 154 a pattern of metallized areas 156 made of a weldable material such as nickel, and having sufficient thickness to permit welding foil mask strips
• the metal strip 160 is severed from the apron
• this shadow mask is in the form of two intercalated combs providing physical separation and mutually insulated first and second arrays of metal strips each adapted to receive a different electrical potential. The difference in potential of the two arrays is effective to cause electron beams passing therethrough to be deflected by the electrical fields created between the strips; as a result, it is termed a "bipotential" shadow mask that provides for post-mask deflection.
• a similar structure is depicted in figure 11, except that there is no gap between metal strips 170, 172 and 174.
• the mask is unpotential "strip mask” that provides acceleration of the electron beams passing therethrough, but provides no post-mask beam deflection.
• the structure is simplified in that the discrete metallized areas 156 shown by figure 10 can comprise the continuous strip of metal 176 indicated. This strip-mask structure is also installable in the color cathode ray tube having a curved faceplate according to the present invention.

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• Electrodes For Cathode-Ray Tubes (AREA)
• Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)

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• 1991
  • 1991-12-18 WO PCT/US1991/009583 patent/WO1992012525A2/en not_active Ceased
  • 1991-12-18 EP EP19920907447 patent/EP0565643A1/de not_active Withdrawn

Non-Patent Citations (1)

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