US2936924A - Cathode-ray tube manufacture - Google Patents

Description

- 1960 w. s BLANDING ETAL 2,936,924

ICATHODERAY TUBE MANUFACTURE f Filed oci. 2, 1953 INVENTORJ l/s-woaz. J fizn/vamm WI 1.14 WJHAK R United Sjtates Patent r 2,936,924 CATHODE-RAY TUBE MANUFACTURE Wendell S. Blanding, Painted Post, and William W. Shaver, Corning, N.Y., assignors' to Corning Glass Works, Corning, N.Y., a corporation of New York Application October 2, 1953, Serial No. 383,804

12 Claims. (Cl. 220-23) The present invention relates to television picture tubes and is particularly directed to the construction of such a tube of the all-glass type suitable for the reproduction of pictures in color.

Television picture reception in color can be obtained through the use of a tube that contains a suitable viewing-screen assembly which may comprise a tri-color phosphor plate and an aperture mask orother grid-like controlling element and which is suitably mounted or other: wise positioned in the panel end of the tube. Since such a viewing-screen assembly is the same or substantially the same as the panel in area, it must be installed before the panel and the funnel are joined together. Because such viewing-screen assembly is relatively sensitive to heat, however, it is necessary that the panel and the funnel be sealed to one another in such a way as to avoid heat damage thereto. This requirement thus renders the conventional manner of sealing the glass panel to the glass funnel of an all-glass black-and-white picture tube unsuitable for the production of such a color picture tube since the heat required to effect the seal is sufiicient to damage seriously or otherwise to impair the viewingscreen assembly. a

We have now discovered that an all-glass type of picture tube can be readily adapted for satisfactory use with such a viewing-screen assembly by sealing the glass panel and the glass funnel to one another through the medium of endless metal strip or ring elements whose "ice 2 such strip is flexed, acondition which cannot be altogether avoided in the welding'of complementary strips to each other.

. In accordance with our invention, these disadvantages are avoided and a satisfactory all-glass type of color television picture tube is produced by employing metal strip or ring elements, each of which comprises a rela-,

tively thick portion and an associated relatively thin portion extending outwardly therefrom with the relativelythick portion substantially conforming in configuration to and following the outline of the sealing surface of the glass panel or the glass funnel and usually having a width substantially only sufficient to afford a satisfactory surface for butt-sealing to the panel or the funnel. The relatively thick portion of one of such elements is butt-sealed to the sealing surface of the glass panel, and the rela-v tively thick portion of the other element is butt-sealed to the sealing surface of the glass funnel. The relatively thin portions of the two elements are in turn joined to each other in sealing relation as by welding preferably adjacent their outer peripheries.

The use of such a thin-thick metal sealing strip or element thus has the advantage that the mass of metal embodied in the seal can be reduced suitably to restrictthe hoop stress and/or any bending stress in the glass portion of the glass-to-metal seal. The thick portion of the strip further provides the rigidity in the glass-to-metal seal area necessary to prevent deformation and pulling away of the metal from the glass that might otherwise result from flexing of the thin portion, as may be neces- 1 sary to bring complementary strips into engagement with outer dimensions or diameter is greater than that of the panel and the funnel. Such endless metal strip or ring elements are respectively butt-sealed to the glass panel and the glass funnel and are in turn sealed to each other as by welding, advantageously adjacent their outer mar: gins or peripheries.

It would appear at first glance that a metal strip or ring of uniform cross-sectional thickness would be quite suitable for this purpose. matches the glass in thermal expansion as is desirably the case, the resulting expansion mismatch causes a hoop stress to be set up in the glass portion of such a glassto-metal seal, however, such stress tending to increase unduly as the thickness or mass of the metal strip or ring is increased. Again, as the thickness of such metal strip or ring increases, more heat is required to eifect the welding of complementary strips to each other with a greater prospect that the glass-to-metal seals maybe damaged.

In addition, a metal strip or ring of sufiicient thickness to Even though the'metal closely one another for welding. Furthermore because of the thin character of the outwardly extending portions of the strips, the amount of heat required to weld them to one another is not sufiicient to damage theglass-to-metal seals while making the weld. Such relatively thin por tions moreover possess sufiicient pliability or resilience so that they can be flexed to the extent necessary in preparation for their welding together.

In the accompanying drawing Fig. l is a side elevation of an all-glass type of round television picture tube envelope embodying the glass-to-rnetal seal of the present invention.

Fig. 2 is an enlarged sectional view of a fragment 0 a picture tube such as shown in Fig. 1 illustrating one specific form of the glass-to-metal seal.

Fig. 3 is' a view similar to Fig. 2 illustrating a specifically difierent embodiment of the glass-to-metal seal.

Fig. 4 is an enlarged perspective view of a fragment of a metal sealing strip similar'to those employed in the structure of Fig. 2.

Fig. 5 is a view similar to Fig. 2 illustrating the relationship of the parts resulting from use of strips such as illustrated in Fig. 4.

The picture tube envelope shown in Fig. l embodies a funnel portion 11 and a panel portion 12 and includes a metal sealing assembly 17 which may comprise any of the forms specifically shown in Figs. 2, 3 and 5. C011 ventionally shown in dotted lines is a viewing-screen assembly 10.

In the embodiment illustrated in Fig. 2 the panel portion 21 of a tube envelope is butt-sealed to one broad surface of the thick cross-sectional portion 22 of a metal strip or ring having an integrally adjoining thin cross: sectional portion 23 preferably but not necessarily, with a corrugation or rib 24 formed therein paralleling the seal. A similar but oppositely disposed strip or ring comprising corresponding parts 22, 23, and 24 is, in a similar fashion, but-sealed to the funnel portion 25 of the tube envelope. As shown, the thick strip portions 22 and 22 need be only sufiiciently wide to provide the necessary surface to effect a satisfactory butt seal. Strip portions 23 and 23' are hermetically joined to one another at or adjacent to their outer boundaries preferably by welding, as at 29. To reduce point loading between strip portions 22 and 22 that may occur as a result of such welding, an annular gasket 28 of a soft metal or othersuitable material may be provided therebetween.

As described and claimed in a commonly owned application of John F. Frazier, Serial No. 383,803, filed of even date herewith, strip portion 22 is advantageously provided along its inner margin with an inwardly extending peripheral projection 26, to which are appropriately welded a plurality of spaced threaded studs 27 for supporting a viewing-screen assembly 20. Projection 26 may be of any thickness suitable to provide the desired resilience and structural strength and may be welded or otherwise joined to portion 22' as indicated or formed integrally therewith.

If desired, a similar thick-thin metal strip can be made by first forming a thin strip of an inner peripheral dimension smaller than that'of thick portion 22 and then folding the inner marginal portion of such thin strip back upon itself to form the thick portion. Advantageously, the adjointing strip surfaces are welded to one another.

In the embodiment illustrated in Fig. 3, the metal sealing element includes a relatively thick strip 32 which is only of suflicient width to provide the surface necessary for the butt seal to the panel portion 31. A companion strip 33 of relatively thin metal is arranged adjacent to the opposite surface of strip 32 and is joined thereto as by welding along or adjacent to their inner margins, as at 34. Oppositely disposed corresponding strips 32 and 33' are similarly associated with respect to the funnel portion 35. As shown, strips 32' and 33' are welded to one another preferably along a line outward from their inner margins as at 36. The latter manner of joining the thick and the thin strips may, of course, also be utilized in the panel-sealing element.

As in the case of strip portion 22 shown in Fig. 2, strip 33 desirably has an inwardly projecting peripheral projection 37 which at suitably spaced intervals is provided with studs, such as 38, for supporting a viewingscreen assembly 30. As in the structure of Fig. 2 the adjoining similar strips 33 and 33' are welded to one another at or adjacent to their outer margins as at 39.

During the butt-sealing of strip portions such as 22 or strips such as 32 to the glass parts, such strip portions or strips under other than ideal heating conditions tend to expand and tip at a slight angle (generally on the order of 3), as shown greatly exaggerated in Figs. 2 and 3. After strip portions 23 and 23 or strips 33 and 33 are subsequently sealed to each other and the tube has been evacuated the compressive load instead of being between the broad surfaces of strip portions 22 and 22' or strips 32 and 32 is thereby diverted toward the outer margins of such surfaces. With the compressive load between the outer margins of such surfaces there is more likelihood of point loading therebetween, and since such compressive load tends to return the strips to their initial fiat condition there is a tendency for the inner margins of the butt seals to be placed under tension.

This tipping can be compensated for by shaping the integral strip shown in Fig. 2 to provide an angle of approximately 3 between the thick portion and the outwardly extending thin portion as illustrated by the strip 40 in Fig. 4. Such a strip during the butt-sealing operation expands and becomes substantially fiat, as illustrated by the sealing stripus 40 and 40 shown sealed respectively to glass parts 41 and 45 in Fig. 5. In such arrangement, moreover, less point loading between the strips prevails, thus reducing or eliminating the need for use of a gasket therebetween. A similar construction can also be provided in the thin strip of the combination metal sealing element shown in Fig. 3.

Strip portions 22 and 22' and strip portions, 23 and 23" may respectively vary considerably in thickness, as may strips 32 and 32' and. strips 33 and 33'. In any particular case, however, the optimum or desirable thickness in each strip portion or strip depends in large part on the size of the tube as well as its shape and to some extent on the particular glass and metal utilized. In any event the relatively thin portions or the thin strips should not be so thick as to objectionably increase the hoop stress in the glass portion of the glass-to-metal butt seal or to introduce other objectionable stresses into the glass parts when complementary thin strip portions or thin strips are clamped for welding. Moreover, if such thin strip portions or thin strips are too thick, the amount of heat necessary to effect the welding therebetween may be suflicient to require forced cooling of the glass-to-metal seals in order to prevent damage thereto while making the Weld.

By way of example an entirely satisfactory all-glass type of 15-inch round color television picture tube can be produced in accordance with thepresent invention by the use of relatively thick strip portions or relatively thick strips ranging from 0.60" to 0.100" in thickness and by the use of relatively thin strip portions or relatively thin strips ranging from 0.020" to 0.030 in thickness. Generally speaking, the relatively thin strip portions or the relatively thin strips should not be much thinner than 0.020 since otherwise excessive warping may occur and the welding of complementary strips together may become objectionably difficult.

It will also be appreciated that, while in the strip assemblies shown, the glass surfaces have been sealed to the thick strips thereof, it is within the concept of the invention to attach the thick strip to the opposite side of the thin strip thus employing the thick strip merely as a stiffening member and to then butt-seal the glass to the thin strip side of the assembly. Furthermore it will be apparent that, as so-called thin strips of greater thickness are employed, a corresponding reduction in thickness of the so-called thick strips can be tolerated. In other words, as the thickness of the so-called thin strip is increased, the so-called thick strip can be correspondingly reduced in thickness, since when both such strips are sealed to one another the effectiveness of a thick strip is acquired.

As will be understood, this invention is equally applicable to either circular or non-circular including the so-called rectangular-type picture tubes, the glass-sealing portions of the metal sealing elements being merely conformed to the outline of the glass surfaces to which they are to be butt-sealed.

It should be further. understood that, although the shape of the panels illustrated closely follows that embodied in commercial all-glass black-and-white picture tubes, the invention is not limited in this respect, since sealing strips embodying the invention can with equal facility be sealed to shallow-walled, concave-convex, or substantially flat panels such as are ordinarily employed in metal-funnel picture tubes. Nor is the invention necessarily limited to picture tubes embodying glass funnels since a panel equipped with a sealing strip embodying the invention may with equal facility be edge-welded to a suitably shaped flange of a metal funnel.

While the endless metalstrip or ring elements have been shown as substantiallyv flat or planar, they can also be formed with the relatively thick portion arcuately shaped, as described and claimed in a commonly owned application of Francis W. Martin, Serial No. 383,871, filed of even date herewith.

We claim:

1. An article comprising two glass members, at least one of which is hollow, such members having endless sealing surfaces facing one another, and an assembly interposed between such sealing surfaces and comprising a pair of endless strip elements of metal having a melting point above that of the glass members, each such element comprising a relatively thick portion and an associated relatively thin portion extending outwardly therefrom, only the relatively thick portion of one of said elements contacting and being butt-sealed directly to the sealing surface of one of said glass members and only the relatively thick portion of the other of said ele ments contacting and being butt-sealed directly to the sealing surface of the other glass member, the relatively thin portions of the two elements being joined to one another in sealing relation.

2. An article such as defined by claim 1 which includes a compressible gasket arranged between the relatively thick portions of the two elements.

3. An article comprising two glass members, at least one of which is hollow, such members having endless sealing surfaces facing one another, and an assembly interposed between such sealing surfaces and comprising a pair of endless metal strips, each such strip comprising a relatively thick portion and an integral relatively thin portion extending outwardly therefrom, the relatively thick portion of one of said strips being butt-sealed to the sealing surface of one of said glass members and the relatively thick portion of the other of said strips being butt-sealed to the sealing surface of the other glass memher, the relatively thin portions of the two strips being joined to one another in sealing relation.

4. An article such as defined by claim 3 wherein the relatively thin portions of the two strips are joined to one another adjacent their outer peripheries.

5. An article comprising two glass members, at least one of which is hollow, such members having endless sealing surfaces facing one another, and an assembly interposed between such sealing surfaces and comprising a pair of endless metal elements, each such element comprising a relatively thick strip and an associated relatively thin strip, the relatively thin strip being joined to the relatively thick strip in sealing relation and extending outwardly therefrom, the relatively thick strip of one of said elements being butt-sealed to the sealing surface of one of said glass members and the relatively thick strip of the other of said elements being butt-sealed to the sealing surface of the other glass member, the relatively thin strips of the two elements being joined to one another in sealing relation.

6. An article such as defined by claim 5 wherein the relatively thin strip of at least one element is joined to its associated relatively thick strip adjacent their inner peripheries.

7. An article such as defined by claim 5 wherein the relatively thin strip of at least one-element is joined to its associated relatively thick strip along a line outward from their inner peripheries.

8. An article such as defined by claim 5 wherein the relatively thin strips of the two elements are joined to one another adjacent their outer peripheries.

9. A television picture tube comprising an envelope, said envelope comprising a glass viewing panel, a glass funnel, said panel and said funnel having endless sealing surfaces facing one another, and an assembly interposed between such sealing surfaces, said assembly comprising a pair of endless strip elements of metal having a melting point above that of the glass funnel and panel, each such element comprising a relatively thick portion and an associated relatively thin portion extending outwardly V therefrom, only the relatively thick portion of one of said elements contacting and being butt-sealed directly .to the sealing surface of the panel and only the relativesaid envelope comprising a glass viewing panel, a glass funnel, said panel and said funnel having endless sealing surfaces facing one another, and an assembly interposed between such sealing surfaces, said assembly comprising a pair of endless metal strips, each such strip comprising a relatively thick portion and an integral relatively thin portion extending outwardly therefrom, the relatively thick portion of one of said strips being butt-sealed to the sealing surface of the panel and the relatively thick portion of the other of said strips being butt-sealed to the sealing surface of the funnel, the relatively thin portions of the two strips being joined to one another in sealing relation.

11. A television picture tube comprising an envelope, said envelope comprising a glass viewing panel, a glass funnel, said panel and said funnel having endless surfaces facing one another, and an assembly interposed between such sealing surfaces, said assembly comprising a pair of endless metal elements, each such element comprising a relatively thick strip and an associated relatively thin strip, the relatively thin strip being joined to the relatively thick strip in sealing relation and extending outwardly therefrom, the relatively thick strip of one of said elements being butt-sealed to the sealing surface of the panel and the relatively thick strip of the other of References Cited in the file of this patent UNITED STATES PATENTS 2,178,826 Bowie Nov. 7, 1939 2,202,469 'Schedel May 28, 1940 2,254,090 Power Aug. 26, 1941 2,423,066 Giboson June 24, 1947 2,527,587 Smyth Oct. 31, 1950 2,635,205v Olson Apr. 14, 1953 2,650,683 McPhee et al. Sept. 1, 1953 2,663,821 Law Dec. 22, 1953 FOREIGN PATENTS 583,242 Great Britain Dec. 12, 1946

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