US3403805A - Cathode-ray and other vacuumized tubes resistant to violent devacuation - Google Patents

Description

E. POWELL ETAL CATHODE-RAY AND OTHER VACUU 3,403,805 MIZED TUBES Oct. 1, 1 968 RESISTANT TO VIOLENT DEVACUATION 2 Sheets-Sheet 1 Filed May 31, 1966 INVENTOR.

PEAR 69%! D. E. POWELL ETAL 3,403,805 CATHODE-RAY AND OTHER VACUUMIZED TUBES Oct. 1, 1.968

RESISTANT TO VIOLENT DEVACUATION 2 Sheets-Sheet 2 Filed May 31, 1966 fl m o INVENTOR. DE Po WELL BM) PEAK United States Patent 3,403,805 CATHODE-RAY AND OTHER VACUUM IZED TUBES RESISTANT T0 VIOLENT DEVACUATION Daryl E. Powell, Maumee, and Burton W. Spear, Toledo, Ohio, assignors to Owens-Illinois, Inc., a corporation of Ohio Filed May 31, 1966, Ser. No. 553,757 13 Claims. (Cl. 2202.1)

ABSTRACT OF THE DISCLOSURE A direct-viewing impolsion resistant cathode-ray television picture tube comprising a glass envelope having a funnel portion and a flanged face plate member. An annular perforated reinforcing band is closely fitted to the external surface of the face plate flange. The perforations in the band are filled with a single layer of adhesive material which also extends under the band to form an intermediate layer between the band and the surface therebeneath.

The present invention relates to cathode-ray tubes and more particularly to the control and prevention of fracture and implosive-explosive effects in vacuumized cathode-ray picture tubes for television reception. More specifically, this invention relates to improved types of directviewing cathode-ray image tubes having glass envelopes and methods of fabricating such envelopes to eliminate breakage and to control devacuation thereof either in processing, shipping, installation or while in service.

Cathode-ray tubes are vacuumized to very low pressure and breakage of the envelope for any reason usually results in an implosion. Such implosion is accompanied by an explosion which, particularly in the case of large size envelopes, can be damaging where fragments of the envelope are projected in random directions with considerable force. The most common solution to this problem for many years has involved the use of a tempered-glass implosion panel mounted in front of the tube face plate. Such glass panel mounted in the front of television receiver cabinet and the cabinet itself have been relied upon to contain implosion-explosion effects. In more recent years, the television industry has adopted an integrallysafe direct-viewing tube envelope and it is this type of tube structure that the present invention is concerned.

US. Patent Nos. 3,220,592 and 3,220,593 which issued in our names on Nov. 30, 1965, relate to a basic type of direct-viewing implosion-resistant cathode-ray television picture tubes having glass envelopes and methods of fabricating such tube envelopes. These invention eliminate sources of fracture originating in highly-stressed areas and particularly those of substantially maximum cross-sectional dimensions of the envelope and prevent the deleterious effects which result from sudden violent devacuation.

-As disclosed in the referenced patents, noteworthy results have been achieved in protecting non-viewing areas of the tube envelope in such manner that damage to the tube envelope from whatever source and wherever caused cannot result in damaging implosion-explosion. The need for a separate implosion plate either mounted separately from or integrally with the image tube face plate has been eliminated in such manner that the tube face plate may be direct-viewing in all conventional sizes of television picture tubes.

The present invention constitutes an improvement over the tube constructions and methods of fabricating disclosed in the referenced patents, particularly with regard to further reducing the likelihood of an implosion and preventing its occurrence as well as providing improved reinforcement at minimal cost.

Accordingly, it is an object of the present invention to provide a direct-viewing cathode-ray tube construction which is capable of expeditious fabrication to provide both resistance to fracture and control of sudden devacuation without serious fragmentation of the envelope under widely-varying adverse conditions.

Another object of this invention is to provide an improved type of essentially all-glass cathode-ray tube envelope by the use of annular reinforcing elements mounted on non-viewing exterior surfaces of the envelope at peripheral sidewall areas which are subject to damage due to their dimensions with such elements controlling sudden devacuation upon fracture however caused.

Another object of this invention is to provide a directviewing non-imploding cathode-ray image tube construction which may be directly viewed without a protective implosion panel mounted forwardly of its viewing area, such construction being applicable to resisting common forms of glass surface damage in both large and small size tubes and preventing their violent devacuation, the internal working components of the completed tube being fully capable of functioning in their normal manner.

A further object of this invention is'to provide a cathode-ray tube structure having an essentially all-glass tube envelope with an annular perforated metal reinforcing band surrounding its forwardmost non-viewing sidewalls surrounding its viewing screen, said band being adaptable to mounting on either round or rectangular envelopes either before or after their final fabrication into completed tubes.

A still further object of this invention is to provide a method of imparting fracture resistance to a rectangular glass cathode-ray tube envelope to eliminate implosiveexplosive effects on breakage of the envelope from any cause. Fracture propagation through an annular area of maximum cross-sectional dimensions is prevented or retarded in such manner that violent collapse of major sidewalls of the envelope cannot occur. 7

The specific nature of this invention, as well as other objects and advantages 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 the invention.

On the accompanying drawings:

FIG. 1 is a perspective view of a cathode ray television picture tube fabricated in "accordance with the present invention.

FIG. 2 is an enlarged vertical sectional view of one portion of the tube envelope taken along the line of 2-2 of FIG. 1.

FIG. 3 is a view similar to FIG. 2 showing another embodiment of the invention.

FIG. 4 is a perspective view similar to FIG. 1 showing still another embodiment of the invention.

FIG. 5 is an exploded view illustrating the individual components utilized to form the embodiment shown in FIG. 4.

FIG. 6 is an enlarged vertical sectional view of one portion of the tube envelope taken along the line 66 of FIG. 4.

FIG. 7 is an enlarged fragmentary view showing a modification of the invention illustrated in FIGS. 1 and 2.

The present invention is described hereinafter as specifically applied to the manufacture of cathode-ray television picture tubes. However, it will be apparent to those skilled in the art that the invention is equally applicable to the manufacture of many different types of vacuum tubes utilizing glass envelopes, particularly those having substantial dimensions which are subject to implosion and virtually simultaneous explosion on sudden devacuation.

The term devacuation as used herein is intended to mean the converse of vacuation as in the case where a vacuumized vessel or tube experiences an internal pressure change toward atmospheric upon loss of vacuum. The rate of change may occur rapidly, in which case the deleterious effects can be exceedingly violent, or more slowly over a longer period of time whereby such effects are greatly moderated. Obviously, moderating the rate of devacuation results in gradual dissipation of the forces causative of destructive implosion.

The present invention provides an implosion-resistant system which is capable of being incorporated into all existing types and shapes of conventional cathode-ray picture tubes without serious alteration or modification of present fabricating procedures. The invention may be incorporated into any selected type of tube using materials and methods which are capable of supplementing normal bulb and tube production. The term bulb is applied to hollow glass envelopes having none of the image-producing electrical components installed While the term tube is used to designate the completed electron-discharge device having all of its electrical components installed in fully-evacuated condition, capable of displaying a raster on its image-creating screen.

In a preferred embodiment of the present invention, a glass cathode-ray tube envelope is normally comprised of a funnel member 11, face plate member 12 and neck tubulation 13 which are joined to form a unitary hollow glass article capable of withstanding the force of atmospheric pressure when vacuumized. The terminating end of neck tubulation 13 is normally sealed by an end cap 14 retaining one or more electron beam-emitting guns which project forwardly interiorly through neck tubulation 13. Funnel member 11 is usually frusto-conical or frustopyramidal in shape with its smaller end sealed to neck 13 and its larger end sealed to face plate 12 at a planar seal line 15. Electromagnetic beam-deflecting coils (not shown) are normally exteriorly mounted at the yoke area where neck 13 and funnel small end are joined to provide proper scanning of the tube screen 16 by the electron beam.

Face plate 12 consists of a concavo-convex viewing portion 12a bounded 'by a depending annular side panel or flange 12b. Flange 12b and funnel large end terminate in annular sealing surfaces of complemental contour. The sealing surfaces are joined at seal line either by direct fusion of the glass or by an interposed annular layer of low-melting glass-sealing composition such as a devitrifying-type solder glass which is selected as being compatible with the thermal and physical characteristics of the parent glass parts. The basic shape of the envelope viewing area 12a may be either circular or rectangular in plan as conventionally known in the art with the sealing surfaces being substantially planar for forming a durable hermetic joint. The foregoing description is applicable to many known types of television picture tubes used for both monochromatic and polychromatic image creation.

The invention, as presently contemplated, consists of applying selected elements to external non-viewing surfaces of the tube envelope, either after the tube is fully fabricated or prior to subjecting the envelope or bulb to a tube fabricating process. In the former case the tubeis fully completed and assembled with all its required external and internal working components properly installed in operative alignment and after being subjected to bake-out temperatures and devacuation. In the latter case, the tube envelope consists of the so-called glass bulb having only a part of the electronic working components installed such as the metal anode button in the funnel side wall and/ or a plurality of mask mounting studs sealed internally of face plate flange 12b in the case of a color TV envelope. The envelope or bulb is subjected to the application of the required elements with ambient conditions existing both exteriorly and interiorly thereof. The bulb, after being fabricated into a form Where its devacuation can be controlled, is then subjected to a tube fabricating process. In this case, the components of the present implosion resistant system must be capable of withstanding required bake- 4- out cycling temperatures and pressures of the tube making process.

In describing a preferred embodiment of the present invention shown in FIGS. 1 and 2, a completed picture tube 10 capable of recreating transmitted images is subjected to reinforcement of the tube envelope in the following manner:

An annular perforated reinforcing band 20 of thinwalled high-tensile strength material such as metal is press formed having a transverse cross-sectional contour which conforms snugly to the forwardmost non-viewing exterior surfaces of face plate flange portion 12b. Band 20 preferably consists of preformed shaped metal member having a plurality of spaced-apart perforations or apertures 21 extending throughout its lateral and circumferential dimensions. Band 20 is preferably formed of pressed sheet steel having a thickness of about .020 to .040 inch which is capable of surrounding and encompassing the non-viewing corner region of the face plate closely adjacent its viewing area. Band 20 may consist of either an untensioned rim band or a tension band depending upon the size and shape of the tube envelope.

In the illustrated embodiment of the invention shown in FIGS. 1 and 2, the concavo-convex character of rectangular viewing area 12a of the face plate is shown which is utilized in many conventional types of cathode-ray picture tubes. Rim band 20 has a substantially greater width at the center of its arcuately-shaped long axis sides and lesser Width on its similarly-shaped short axis sides. The forward edge of reinforcing rim band 20 has a contour which is similar in shape to the periphery of the envelope screen line and the rearward edge resides in a plane normal to the tube axis and parallel to the mold match line of the face plate flange. Mold match line 120 is a region of maximal cross-sectional dimensions of the envelope.

Perforated rim band 20 is preferably formed with a circumferential dimension which is closely fitted to the external surfaces of the face plate flange. Band 20 may be formed from two U-shaped symmetrically-similar half sections which are welded together to form an endless band or it may be press-formed from a single sheet of perforate material. After the band is properly formed in foreshortened condition, it is expanded such as by heating and placed over and around the exterior surfaces of the face plate flange which may or may not be preheated as required. Normally preheating of the face plate or the entire bulb is not required; however, some slight preheating may be desirable in some cases to prevent thermal shock. Band 20 is permitted to cool in place to contact around the surrounded exterior surfaces so the band develops tensile stresses which in turn develop counteracting compressive stresses in the glass sidewalls therebeneath. Such sweating on of band 20 is most effective when the band is preheated to an elevated temperature short of damaging effects to enlarge the same due to thermal expansion and the bulb remains unheated.

Following application of band 20 perforations 21 in the rim band which are complete apertures are preferably filled with a single layer of adhesive material such as low-melting solder glass to essentially fill the perforations and extend under the band to forman intermeditte layer between band and exterior surfaces therebeneath. The intermediate layer of adhesive material may or may not extend fully annularly. It is adequate for the intended purposes if it cements band 20 in place only in localized areas throughout the face flange periphery. A preferred solder glass is a lead-zinc-borate devitrifying-type sealing glass composition similar to Owens-Illinois Product No. CV- may be used to provide an intermediate layer 30 of adhesive or sealing material. Where solder glass is employed as the adhesive, its thermal expansion coeflicient is preferably matched to band 20 such as stainless steel No. 430 to permit its being applied either prior to or after band application.

As an alternative, intermediate layer 30 of adhesive material may becomprised of a synthetic organic resinous material such as epoxy or polyester resin. The epoxy resin for example consists of a thermosetting synthetic resin having the ability to chemically bond to both the metal and glass surfaces with the material having good chemical resistance and sufficient flexibility to permit some flexure of the bond without destruction. The epoxy system is composed of liquid epoxide resin which is cross linked by a liquid hardener into a thermoset which is a tough, resistant solid having excellent dimensional stability and strength. Such reacted resin system when cured forms a stable firmly-adhesive bond to both the, glass and metal. A preferred material consists of a Dow Epoxy Resin No. 741 manufactured by Dow Chemical Company which has been previously heated to a temperature ranging from 170 to 190, the resin having been previously mixed with eight parts of Dow Epoxy Resin Hardener No. 61 per one hundred parts of resin. An example of polyester resin is Plaskon Polyester Resin No. 9407 which is a rigid type, promoter-containing resin to which a catalyst such as methyl ethyl ketone peroxide is added to initiate tack-free cure.

Thus, it can be seen from the construction shown in FIGS. 1 and 2, rim band 20 may be applied either to an unexacuated bulb or completed tube; however, selection of the adhesive material must take into consideration its ability to withstand elevated temperatuers of the order of 430 C. which are utilized in tube bake-out cycling if a tube making operation is to follow. The form of the invention shown in FIGS. 1 and 2 is of special advantage in reinforcing smaller size picture tubes of the order of 11, 12, and 16 diagonal inch sizes.

In another embodiment of the present invention shown in FIG. 3, the rim band 20a consists of a semi-annealed steel strap having a uniform cross-section with a series of perforations or apertures 21a formed throughout its circumferential and lateral extent. Such band preferably consists of semi-annealed steel strapping of substantially uniform rectangular cross-section which is capable of being placed in tension and is particularly useful .for surrounding the skirt portion of small picture tube sizes such as 11 and 12 diagonal inch. In such sizes, flange 12b has lesser dimensions and adequate implosion protection can be provided by such band properly applied. Band 20 a is positioned so that its centerline preferably coincides with mold match line 120 of the face flange portion. p

In another modified form of the invention shown in FIG. 7, perforate rim band 20b is essentially enveloped by an annular layer 30b of low-melting solder glass or synthetic resin 30b. In this case, the layer of solder glass 30b contacts both interior and exterior surfaces of the perforated rim band. and is applied to a greater extent both internally and externally of the rim band to obtain improved adherence of the rim band to the glass exterior surfaces. The perforate nature of the band and its enveloping layer of adhesive material permit their ready application to a wide range of types of picture tubes with good results, especially smaller sizes.

.In a still further embodiment of the present invention, FIGS. 4, 5 and 6 illustrate a contoured perforate or mesh-type rim band 200 which is applied in the same manner as described hereinabove. Band 200 is preferably placed in tension by shrink fitting the same onto the tube; however, it may be untensioned. After the rim band is mounted in place, a second reinforcing band is applied over and around the rearward edge of rim band 20 forwardly of envelope seal line 15. Band 40 consists of high-tensile strength material such as semi-annealed steel strapping which is essentially imperforate and is termed a tension band. A connecting clip 41 is fitted onto one end of tension band 40 for joining its ends and maintaining continuous tension. Rim band 200 r is preferably overlapped to approximately one-half the width of tension band 40. The selected adhesive material 30 is then applied to the exterior surface of band 200 to penetrate its apertures and to flow at least in localized areas into the space between rim band 200 and the glass exterior surfaces.

In each of the embodiments of the invention described above, a plastic or rubber-like material may be used in place of metal for perforated rim band 20'; however, the latter affords the optimum degree of reinforcement. Also the development and maintenance of permanent tensile stresses can be better controlled with a metal band. By proper control of the stresses imparted into the glass sidewalls, the eifect of a source of fracture and resultant breakage is controllable to a high degree.

The following Table I sets forth devacuation data for a series of 5 foot-pound impact tests for evacuated 12 inch bul-bs protected in accordance with the present invention as shown in FIG. 3. In each of these tests, a thin coating of Saureisen cement was first sprayed on the face rim area.12b to protect the glass against thermal shock duringthe sweating-on application of the hot perforated band. Following application of the perforated band, the Saureisen cement was applied over the band and made spot contact with the glass through the perforations. If desired, the Saureisen cement may be modified with a filler material to lower its thermal expansion coefiicient. The following results employed Saureisen cement and 50% filler material such as fine particle perlite, althrough the former used alone provides good results.

In a series of twenty-two (22) tests, ten (10) of which are representative and shown in the table, no cave-ins of the envelope or funnel implosions whereby the funnel portion collapses were experienced. Also, no glass fragments were thrown beyond three (3) feet in any of the tests. Total glass fallout dropped immediately in front of the test cabinet averaged only 1% ounces for the twenty-two (22) tests, all in the form of small fragments.

This data is representative of only one embodiment of the invention as illustrated by FIG. 3 of a uniform cross-section tension-band with the addition of the adhesive over the top of the band as illustrated in FIG. 7.

Examples of results obtained by implosion testing a series of cathode-ray picture tubes utilizing the stated conditions are as follows:

TABLE I Distance (ft.) Band Short- Ball Weight Impact Impact Test No. Band Size ene d D(i me5n- Obs.) (ft.-lbs.) position Result 0-8 3-5 5 sion in.

' Glass Throw (ozs.)

.020 1% 5 Front Large Hole O 0 .020" 1% 5 d 0 0 .020" .150 1 5 1 0 0 .020" .150 1% 5 0 0 0 .020- 1% 5 1 0 0 .020"- 200 1% 5 2 0 0 023" 025 1% 5 0 0 0 023 .075 1% 5 5% 0 0 023 .125 1% 5 0 O 0 023" 175 1% 5 0 0 0 What is claimed:

1. A direct-viewing implosion-resistant television picture tube envelope comprising a substantially funnelshaped hollow body portion and a light-transmitting viewing portion enclosing its larger end, said viewing portion having an integral peripheral sidewall region of substantially maximum cross-sectional dimensions of said envelope sealed to the larger end of said body portion,

an endless reinforcing band of thin-walled high-tensile strength metal surrounding the non-viewing peripheral sidewall region of said viewing portion and complementally contoured to conform snugly thereto,

a plurality of small perforations formed in said reinforcing band extending both laterally and circumferentially essentially throughout its dimensions,

adhesive means penetrating into the perforations of said reinforcing band and contacting the envelope exterior surfaces therebeneath bonding said band thereto, and

constricting means surrounding at least one annular portion of said reinforcing band to maintain the same in closely conforming relation with respect to the peripheral sidewall region,

said reinforcing band, adhesive means and constricting means conjunctively having sufficient yield strength to maintain the envelope sidewall region therebeneath intact upon breakage of said envelope.

2. A direct-viewing implosion-resistant television picture tube envelope in accordance with claim 1, wherein said constricting means comprises a second reinforcing band of thin-walled high-tensile strength metal of uniform cross-section maintained in continuous tension disposed around the rearward portion of said first reinforcing band and substantially forward of said envelope body portion.

3. A direct-viewing implosion-resistant television picture tube envelope in accordance with claim 1, wherein said reinforcing band comprises a pair of complemental U-shaped half-sections of thin-walled high-tensile strength metal disposed in telescoping relation around the forwardmost non-viewing peripheral sidewall region of said envelope, said band being concave-convex in transverse cross-section to conform to the envelope exterior surfaces at said envelope sidewall region.

4. A direct-viewing implosion-resistant television picture tube envelope in accordance with claim 1, wherein said plurality of small apertures comprises a series of uniform circular openings disposed in spaced array throughout all areas of said reinforcing band.

5. A cathode-ray tube envelope resistant to fracture and capable of controlled devacuation on breakage comprising a substantially funnel-shaped hollow body portion and a light-transmitting viewing portion enclosing its larger end, said viewing portion having an integral peripheral sidewall region of substantially maximum crosssectional dimensions of said envelope sealed to the larger end of said body portion,

an annular reinforcing band of thin-walled high tensile strength material surrounding the peripheral sidewall region and complementally contoured to conform snugly thereto,

a plurality of perforations comprising a series of apertures extending substantially throughout the lateral and circumferential extent of said reinforcing band,

adhesive means penetrating and essentially filling the said series of apertures in said band thereby bonding said band directly to the exterior surfaces of said peripheral sidewall region,

said reinforcing band and intermediate adhesive means having sufficient yield strength to substantially prevent fracture propagation through the envelope sidewall region therebeneath upon breakage of said envelope.

6. A cathode-ray tube envelope in accordance with claim 5, wherein said annular reinforcing band comprises a one-piece thin-walled high-tensile strength metal memher having a uniform transverse cross-section, except for the perforations.

7. A cathode-ray tube envelope in accordance with claim 5, wherein said annular reinforcing band comprises a one-piece thin-walled high-tensile strength metal member having a non-uniform concavo-convex transverse cross-section complemental to the forwardmost nonviewing exterior surfaces of said envelope.

8. A cathode-ray tube envelope in accordance with claim 5, wherein said adhesive means comprises an intermediate layer of epoxy resin containing material in solidified reacted condition.

9. A cathode-ray tube envelope in accordance with claim 5, wherein said adhesive means comprises an intermediate layer of low-melting solder glass having a thermal expansion coefiicient complemental to said envelope and reinforcing band.

10. The method of protecting an essentially all-glass cathode-ray tube envelope against fracture and implosiveexplosive elfects upon sudden devacuation comprising the steps of mounting an annular perforate reinforcing band of thin-walled high-tensile strength material around the peripheral sidewall region of substantially maximum cross-sectional dimensions of said envelope, said band having a plurality of apertures extending substantially throughout its lateral and circumferential extent,

introducing an annular layer of adhesive material intermediate said reinforcing band and the sidewall surfaces therebeneath to substantially fill the apertures of said band, said adhesive material having a thermal expansion coefficient complemental to said envelope and said reinforcing band, and

curing said adhesive material to bond said band to the envelope exterior surfaces therebeneath.

11. The method in accordance with claim 10, including the steps of expanding an endless perforate metal reinforcing band having circumferential dimensions and contour closely complemental to said envelope peripheral sidewall region,

applying the expanded metal band to the forwardmost non-viewing sidewall region of said envelope, and contacting said band to place the same in continuous tension.

12. The method in accordance with claim 10, including the step of introducing epoxy resin containing material in an annular pattern into the perforations of said reinforcing band to contact the envelope exterior surfaces therebeneath to band the same into an integral structure capable of preventing fracture propagation therethrough upon breakage of said envelope.

13. The method in accordance with claim 10, including the step of introducing a layer of low-melting solder glass in an annular pattern into the perforations of said reinforcing band to contact the envelope exterior surfaces therebeneath.

References Cited UNITED STATES PATENTS 2,969,163 1/1961 Roberts 220 2.3 3,162,933 12/1964 Trax et al. 2202.1 3,314,566 4/1967 Minneman et al. 220--2.1

MARTHA L. RICE, Primary Examiner.

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