Load-bearing mounting elements for attachment to glass surfaces

May 28, 1968 r. l. vogelpohl 3,385 989

LOAD-BEARING MOUNTING ELEMENTS FOR ATTACHMENT TO GLASS SURFACES

Filed Sept. 29, 1966 2 Sheets-Shee· 1

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Roland L. Vogelpohl.

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May 28, 1968 r. l. vogelpohl 3,385,989

LOAD-BEARING MOUNTING ELEMENTS FOR ATTACHMENT TO GLASS SURFACES

Filed Sept. 29, 1966 2 Sheets-Sheet 2

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INVENTOR.

Roland L. Vogelpohl.

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3,385,989

Patented May 28, 1968

United States Patent Office

3,385,989 LOAD-BEARING MOUNTING ELEMENTS FOR ATTACHMENT TO GLASS SURFACES Roland L. Vogelpohl, Gahanna, Ohio, assignor to Owens-Illinois, Inc., a corporation of Ohio Filed Sept. 29, 1966, Ser. No. 582,888 10 Claims. (CI. 313—85)

ABSTRACT OF THE DISCLOSURE

This invention relates to load-supporting cup-shaped metallic stud elements having substantially uniform wall thickness adapted to permanent attachment to glass surfaces such as the interior of a cathode-ray tube face plate member for fabricating a color TV picture tube envelope.

The present invention relates to stud-like elements adapted to attachment to glass surfaces and in particular to a specific structure for such elements to facilitate their precise mounting in spaced array interiorly of a preformed glass article such as a face plate member of a color television picture tube envelope.

In the production of polychromatic-type picture tube envelopes, for color television reception, it has been found necessary in most conventional types of such tubes to mount a large color-controlling element internally of the tube in close proximity to its viewing area to control electron bombardment of prescribed areas of a multi-color producing luminescent screen. The color-controlling element normally consists of a multiple-apertured electrode member such as a shadow mask or line grid which is designed to control electron bombardment of certain colorproducing phosphors which comprise the tube screen. Normally, the phosphors which comprise the screen are capable of developing three primary colors. The aperture mask structure usually consists of a heavy rectangular or circular frame, complemental in shape to the tube viewing screen, to provide sufficient rigidity so that the individual apertures of the electrode can be precisely positioned with respect to the phosphor screen so that each tube can maintain proper color registry. It is common for the aperture mask to be inserted into the face plate member and removed several times during various tube processing steps in applying the various color-producing components of the screen, each re-installation of the electrode assuring its precise position in exactly duplicatable relation.

Previously, especially-shaped small metal studs or lugs have been employed in series precisely positioned within the internal surface of the face plate flange portion mounted closely adjacent the internal surface of the face plate viewing area. Such metal studs are normally hollow, cup-shaped members which heretofore have been carefully machined to precise specifications. An example of such stud element is disclosed and claimed in U.S. Patent No. 3,004,182 to Pfaender, issued Oct. 10, 1961, assigned to the same assignee as the present application. Each of such stud elements, whether they be of the frangible or non-frangible type, has required that it be formed by a machining operation in order to obtain the precise dimensional tolerances required for duplicatable mounting and alignment of the color-controlling electrode, i.e., the shadow mask, and to meet the physical requirements of various processes used to seal the studs. Precise machining of the cutting edge and skirt tapers are not needed for precise mask-positioning, but to obtain good seal quality under gas-flame sealing conditions. Machined studs have been utilized previously in order to provide the degree of precision required in color television picture tubes. Such machined stud structures having a heavy body portion are capable of carrying the required load without introducing undue stresses in the glass, however, such studs are exceedingly costly to manufacture, inspect and install in such glass article with the required degree 5 of preciseness. The inherent disadvantages of such supporting structure construction are eliminated by this invention.

Accordingly, it is an object of this invention to provide an improved supporting structure for a demountable elec70 trode element of considerable size and weight positioned in positive alignment within the interior of a hollow glass article such as a polychromatic-type picture tube envelope.

Another object of this invention is to provide a novel 15 supporting element adapted to precise press forming from sheet material, such mounting element being particularly applicable to use in series to support a large electronbeam-controlling element in precise demountable and remountable arrangement within a cathode-ray tube en20 velope.

Another object of this invention is to provide a pressformed stud element adapted to expeditious fabrication for attachment to a glass surface by controlled heating to facilitate its being thermally sealed at least partially with25 in and beneath the glass surface without developing adverse stresses therein for permanent and durable support of a color-controlling aperture mask element.

Another object of this invention is to provide a hollow glass face plate member for a cathode-ray tube envelope 30 adapted to color television reception, such face plate having a spaced-apart series of similar cup-shaped metallic stud elements having uniform wall thickness especially adapted to induction heating using high frequency electrical energy to position the stud element in precise load35 bearing relation.

A further object of this invention is to provide a glass face plate for a color television picture tube envelope, said face plate having a precisely located series of hollow cup-shaped stud elements mounted in the internal surface 40 of its flange portion in a plane normal to the tube axis for retention of a color-controlling electrode in readilydetachable precise position, the stud elements having substantially uniform mall thickness throughout their extent for controlled heating by induction-type high-frequency 45 electrical energy during their fusion-type sealing within the glass surface.

A still further object of this invention is to provide a metallic stud element adapted to sealing into a glass surface in load-bearing precise alignment, said element hav50 ing an internal cavity size and shape to obtain a relationship between total stud cavity volume and the trapped air volume in the final seal which is particularly advantageous to the glass-to-metal sealing process.

The specific nature of this invention, as well as other 55 objects and advantages thereof will become apparent to those skilled in the art from the following detailed description, taken in conjunction with the annexed sheets of drawings on which, by way of preferred example only, are illustrated of the preferred embodiments of this in60 vention.

On the accompanying drawings:

FIG. 1 is a plane view of a face plate member of a cathode-ray tube envelope containing a series of stud elements embodying the present invention.

FIG. 2 is a fragmentary vertical sectional view of the ^fnce plate member taken along line 2—2 of FIG. 1.

FIG. 3 is an enlarged fragmentary vertical sectional view of an individual stud element of the conventional tvpe previously utilized in the prior art.

FIG. 4 is a view similar to FIG. 3 illustrating a stud element of the type embodying the present invention sealed in the glass sidewall.

3,385,989 mounted internally of the face plate flange portion in load-bearing relation. The studs are normally positioned in off-center relation in order to ensure reinsertion of electrode 20 in the same duplicatable relationship.

FIG. 5 is a perspective view of the stud element alone shown in FIG. 4 prior to its sealing in the glass.

While the present invention will be described as specifically applicable to the manufacture of a color television picture tube envelope and particularly its face plate member, it will be apparent to those skilled in the art that the principles of this invention are equally applicable to the manufacture of many other types and structures of preformed rigid glass articles upon or within which it is desirable or necessary to mount an independent component part of substantial size and weight directly supported by a series of stud or bracket elements attached to the glass in precise relation.

In a preferred embodiment of this invention, the glass face plate 10 of a cathode-ray picture tube has a uniformly curved concavo-convex viewing panel 11 and an annular skirt or flange portion 12 which terminates in an annular plane sealing surface 13 as shown in FIGS. 1 and 2. Face plate 10 is preferably rectangular in shape or alternately it may be circular in shape, both of which are conventionally known in the art.

A target or screen area 14 is formed on the interior surface of viewing panel 11, the screen being comprised of a layer of phosphor particles deposited in repeated tricolor patterns which constitute the image-producing area of a color-producing cathode-ray image tube. It is common in conventional color picture tubes to mount a small-apertured electrode structure 20 of large size such as a shadow mask shown in broken lines in FIG. 1 within the tube envelope. The electrode must be located in extremely precise alignment between screen area 14 and one or more electron-emitting beam guns disposed in the neck portion of the tube envelope (not shown).

Structure 20 is positioned in a precise distance from .... ...

electron bombardment of individual color-producing phosphors. Structure 20 usually consists of a thin perforate metal sheet 20α extending throughout the tube viewing area. The apertured sheet is attached to a relatively commonly supported in demountable arrangement within the face plate by a series of tangentially-extending leaf springs attached to its peripheral frame 206, each spring having a circular opening adapted to snap over an individual mounting post or stud 25.

Stud elements 25 each have a body portion 25α which is circular in shape with an integral upstanding frustoconical-shaped seating portion 256 extending in one direction adapted to face radially inwardly within flange face 25b is engaged by the opening in the leaf spring on the periphery of electrode structure 20 to retain the latter in precise alignment with respect to the tube viewing area. ____________________________________

FIGS. 1 and 2 show a series of four spaced studs 25 55 of the stud for a brief interval will usually fillet the glass ^f---------------- ' therearound by lowering the glass viscosity.

In the high-frequency stud sealing process, the heat applied to the stud remains relatively constant during the entire sealing cycle. The temperature of that portion of steel alloy. Stud 25 has a circular or disc-shaped body portion 25α with an integral inwardly-projecting frustoconical-shaped seating surface 25b which terminates in a planar surface parallel to disc portion 25α. Mounting portion 25c is right-cylindrical in shape having a uniform external diameter similar to that of body portion 25α. Such stud has a considerably greater internal volume than comparable structures known in the prior art; the greater internal volume minimizing the development of internal pressure on heat-sealing of the stud in the glass side wall. Cup-shaped stud 25 is preferably imperforate throughout its extent. An axial opening in its frustoconical nose or seating portion need not be provided to prevent the development of excessive internal pressure during fusion-type sealing of the stud in the glass.

Stud 25 is preferably comprised of stainless steel alloy such as Sylvania No. 4 alloy or titanium-stabilized Number 430 stainless steel, such material having a coefficient of thermal expansion of about 90xl0~⁷ cm./cm./° C. over the range of 0 to 300° C. Both metals readily seal to Kimble TM-5 or KG-12 glasses, such alloys having thermal expansion coefficients of 82 and 104χ 10~⁷cm./cm./° C. respectively over the stated range. All portions of the stud have a similar wall thickness, preferably ranging from about 0.020 to 0.070 inch in thickness. Tests conducted of such stud elements having varied wall dimensions have shown that a wall weight of about 0.030 inch is preferred for studs adapted to support the shadow mask of a 23 rectangular color picture tube. Cylindrical mounting portion 25c should preferably have about twice the axial dimension of frusto-conical seating portion 25ά. The precise degree of taper of seating surface 25b may be varied as required; however, it has been found that ... . . .- . - . . . . - a degree of taper of about 12° on a side is preferred, and adjacent to viewing screen area 14 for controlling 35 The precise degree of taper must be controlled within ^ζ“»Ττ·ΖΊτ^ nrxm Fnrrltv, A.,,, -J,, — 1 — — — J.. · ._ . , ,, · λ ^χ prescribed limits for reseating the opening in the resilient spring element of the shadow mask frame.

The stud is preferably mounted by retaining its frustoconical seating portion 25b within a complementally30 rigid peripheral member or frame 20έ. Structure 20 is 40 _shaped cavity of a holder (not shown) being held therein by vacuum. The glass sidewall into which the stud is to be inserted is preferably preheated to a temperature of about 200-210° C. or above. Stud member 25 is then preferably heated by induction heating utilizing a high45 frequency induction heating coil surrounding the same to rapidly heat the stud to a temperature of about 1150° C. When the stud reaches a suitable elevated temperature, it is forcefully moved into contact with the glass with its mounting portion 25c driven beneath the glass surportion 12 of the face plate. Frusto-conical seating sur- 50 face, its high temperature effecting a lowering of the r— «ί j .... .... ....... glass _{viscosity in contact} therewith. The stud is driven into final or near-final position and, where necessary, mechanically withdrawn slightly to effect proper filleting of the glass around its contacted surfaces. Continued heating an extremely heavy body portion 30α and inwardly-projecting frusto-conical seating portion 30/j, such stud having a tapered mounting portion 30c embedded in the glass. The tapered mounting or skirt portion has a rather critical degree of taper for proper seating. Such stud, due 65 to its. varying wall weight, can only be fabricated by a machining or casting operation and normally cannot be press formed from stainless steel alloy such as those commonly utilized in the manufacture of cathode-ray picture tubes.

The stud structure 25 which constitutes the subject matter of this invention is shown in detail in FIG. 4. Such stud has a substantially uniform wall thickness throughout its extent and is specially adapted to press forming by conduction to the glass, but even though embedded, the section of the stud remains in the high-frequency field and is subject to the same heating condition it experiences prior to insertion. The glass absorbs heat from the stud and prevents the stud skirt from reheating to the temperature of that section of the stud not in contact with the glass. In addition to the heat transferred to the glass by conduction, a considerable amount of heat is transferred 70 to the glass within the stud cavity by radiation from the stud.

The viscosity of the glass contained within the stud cavity decreases to some degree while the viscosity of the glass at the stud interface is reduced markedly. Such

JY.__ . , i_ , 7· , .., 7----— — ° ---_σ— «V _kUV u^u Hnviiavc is 1UUUICU HldiKeUiy. OUCH om a single sheet of strip material such as stainless 75 conditions of reduced glass viscosity continue for the

3,385 5 duration of the time high-frequency electrical energy is applied to the stud.

Immediately after insertion, when the glass viscosity is lowered sufficiently, pressure of entrapped air in the stud cavity causes the viscose glass to flow along the embedded surfaces of the stud skirt. The contained bubble expands by the displacement of the glass until a condition of equilibrium is reached wherein the reduced air pressure in the expanded bubble is balanced by the resistance of the glass to flow. Care is taken to ensure that the air bubble is positioned within the stud cavity so that the desired thermal and mechanical properties of the glass-tometal seal are obtained.

The larger the ratio of the total stud cavity volume to the volume of the glass inside the stud at full depth of penetration, the lower the resultant pressure of trapped air tending to induce hot glass flow or displacement during sealing. In addition, the actual stud skirt length, if it changes the length of the path of glass flow, also affects glass displacement. The two factors must be balanced by stud design to result in the seal configuration and quality.

Thus, the stud construction of the present invention causes lesser detrimental glass flow from or within the stud cavity and fewer sealing problems than the prior art stud constructions. Such lesser glass flow increases the range of control of the sealing-in process insofar as bubble size and seal contour results are concerned.

Further, the exterior angle of taper of the stud skirt of the prior art stud which has been found to be critical in various sealing processes such as gas-sealing is eliminated.

Additionally, the subject stud construction is adapted to being press formed from sheet material such as Sylvania No. 4 alloy or Type No. 430 stainless steel alloy having a thickness from about 0.020 to 0.070 inch thickness, such press forming being considerably less expensive than machine forming. The total cavity volume to entrapped air volume at full depth of penetration is an important feature of the present stud construction. It is preferred that the total cavity volume should not be more than three times the contained air volume to obtain an optimum strength seal.

The greater contained volume of the subject stud construction is particularly beneficial in minimizing the development of excessive internal pressure which is generated during thermal sealing of the stud in the glass. The internal pressure generated during sealing is insufficient to cause deep and/or uneven pocketing of the glass which can result in non-uniform seals and residual stresses which can cause breakage of the glass-to-metal seal resulting in the loss of an extremely valuable tube assembly either during its processing, installation in a receiver, or while in service. The internal volume of the subject stud is more than double that of the prior art structures to minimize adverse effects due to excessive internal pressure.

Various modifications may be resorted to in the spirit and scope of the appended claims.