US3305123A

US3305123A - Cathode-ray tube

Info

Publication number: US3305123A
Application number: US336732A
Authority: US
Inventors: Roger M Nordby
Original assignee: Zenith Radio Corp
Current assignee: Zenith Electronics LLC
Priority date: 1964-01-09
Filing date: 1964-01-09
Publication date: 1967-02-21
Anticipated expiration: 1984-02-21

Description

Feb. 21, 1967 R. M. NORDBY INVENTOR. @0962 7??. WQWCZQ United States Patent O 3,305,123 CATHODE-RAY TUBE Roger M. N ordby, Wilmette, Ill., assigner to Zenith Radio Corporation, Chicago, Ill., a corporation of Delaware Filed Jan. 9, 1964, Ser. No. 336,732 9 Claims. (Cl. 220-2.1)

This invention relates in general to cathode-ray tubes and in particular to an improved cathode-ray tube and safety plate assembly for a television receiver.

The use of a highly evacuated cathode-ray tube in home entertainment apparatus, such as a television receiver, necessitates precautionary measures in order to protect the viewer in the event of a tube implosion. Ofne such measure takes the form of a transparent safety plate which is positioned directly in front of the display screen of the picture tube. While a variety of arrangements for mounting this plate have been utilized, a common practice is to employ a support which rigidly fixes the safety plate with respect to the tube as by peripherally anchoring the plate adjacent an opening in the front wall of the cabinet. As -will Ibe shown, this practice can contribute to safety plate failure should the tube implode.

A tube implosion is generally initiated by a crack or a fault on the surface of the tube envelope. Instantly, since substantial portions of the envelope surface are under tension due to the force exerted by atmospheric pressure, a multitude of additional fissures are developed. As a result, there is more or less a complete mechanical breakdown of the tube which is manifested, in part, by a violent dispersion of glass particles. It is, of course, the purpose of the safety plate to intercept the flying glass and confine the eects of the implosion to the television cabinet proper.

An additional factor to be considered is the effect of the implosion upon the safety plate itself particularly when the safety plate is hermetically sealed to the face plate of the tube as is required to effect a dust seal therebetween. While being scored and scratched by iiying glass, the plate is simultaneously subjected to a substantial pressure differential, that is, a very low pressure on the inside and atmospheric pressure on the outside. As a result, the plate is driven toward the tube under the impetus f atmospheric pressure. When the edge of the safety plate is rigidly constrained about its periphery, as practiced in a common prior art arrangement, the plate tends to bow subjecting the inner surface of the plate to tension forces. At this particular instant the plate is readily susceptible to failure because of the inability of the scratched inner surface to withstand the tension forces. This problem has vbeen resolved in the past by resorting to the use of a tempered or heavy glass plate, both rather expensive expedients.

An improvement in the method of mounting the safety plate is described in Patent 3,084,217 which issued to Joseph P. Fiore et al. and is assigned to the same assignee as the present invention. This patent describes a mounting arrangement in which the safety plate is yieldably suspended between the face plate of the tube and the cabinet or the escutcheon by a pneumatic mount. This mount comprises a gasket having a channel that embraces the plate about its perimeter and a bulbous portion that confronts the display panel to define with the channel portion a yieldable cushion which accommodates displacement of the safety window upon occurrence of a tube implosion.

An alternative implosion precaution is to bond a safety window directly to the face of the picture tube. In such an arrangement a safety window, having a bowl portion conforming substantially to the display panel of the tube and containing a quantity of transparent epoxy resin which dl Patented Feb. 21, 1967 fice covers the entire face of the tube, is laminated directly to the face of the tube envelope. As would be expected, the additional processing and material required in making a fully laminated tube is reflected in its cost which is substantialy more than that of the picture tube arrangement herein considered.

It is therefore a general object of the invention to provide an improved cathode-ray tube and safety plate arrangement.

It is a particular object of the invention to provide a unitary cathode-ray tube and safety plate assembly.

It is also an object of the invention to provide an improved method for bonding a safety plate to the face plate of a cathode-ray tube.

It is a further object of the invention to provide a cathode-ray tube arrangement which affords substantial economies over prior art safety plate mounting arrangements.

A cathode-ray tube constructed in accordance with the invention comprises an envelope having a curved screen-bearing face plate with a predetermined viewing area and a safety plate with a transparent section having overall dimensions greater than those of the viewing area and a curvature conforming substantially to the curvature of the face plate. The safety plate is secured in an overlying spaced relation to the face plate and hermetically sealed thereto by bonding means consisting of a continuous layer of adhesive paste in intimate contact with and confined to confronting portions of the envelope and the safety plate which are outside of the face plate viewing area. The adhesive paste is cured so as to constitute a resilient gasket capable of yieldably accommodating 4displacement of the safety plate relative to the face plate of the tube.

The features of this invention which are `believed to 'be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood, however, by reference to the following description taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify like elements, and in which:

FIGURE 1 is a perspective view of a cathode-rayl tube embodying the invention;

FIGURE 2 is a sectional view taken along lines 2 2 of FIGURE 1;

FIGURE 3 is a perspective view of apparatus employed in practicing the invention;

FIGURE 3a is a fragmentary detail of FIGURE 3 illustrating the `deposition of a gasket forming sealant on the faceplate of a cathode-ray tube;

FIGURE 4 is a perspective view of apparatus employed in practicing an alternate embodiment of the invention;

FIGUR-E 4a is a fragmentary detail of FIGURE 4 illustrating the deposition of a gasket forming sealant in accordance with an alternate embodiment of the invention; and

FIGURE 5 is a sectional view of a cathode-ray tube employing a safety window construction in accordance with an alternate embodiment of the invention.

FIGURES 1 and 2 show a cathode-ray tube 10 comprising an envelope having a neck 11, a funnel portion 12 and a curved faceplate 13 with `a -crown 14 which is butt-sealed to the rim of funnel 12. A phosphor screen 15, which is deposited on the inside surface of faceplate 13, covers substantially all the inner surface thereof. The usable viewing area, however, is restricted to that portion which is bounded by the `dotted-line enclosure identified by reference numeral 16.

A safety plate or window 17 is disposed in an overlying relation to faceplate 13 and has a transparent section essaies with overall dimensions greater than those of viewing area 16 and a curvature conforming substantially to the curva- ,ture of faceplate 13. Safety plate 17 is bonded to faceplate 13 and hermetically sealed thereto by a resilient gasket 18 which is in intimate adhesive contact with the confronting peripheral portions of faceplate 13 and safety plate 17 outside viewing area 16.

Gasket 18 not only bonds safety window 17 to faceplate 13, but, because of its resiliency, also accommodates displacement of safety plate 17 relative to faceplate 13 as would be required in the event of tube implosion. Moreover, .as a hermetic seal, gasket 1S also serves to prevent dust, moisture and other contaminants from collecting on the viewing surface of the faceplate. Preferably, gasket 18 is compounded of a viscous synthetic rubber base to which a solidifying or curing agent has rbeen added. In an embodiment of the invention which was 'actually constructed, a 'eyw'inch safety plate was bonded to a 19 inch cathode-ray ltube by a gasket formulated from a polysulfide polymer which was cured by the addition of a lead peroxide. Chemically, the polysulfide polymers are methanes containing disulfide linkages. The polymer segments `are terminated with reactive mercaptan (SH). The average structure -of a polysullide polymer may be represented as follows although some of the polymers are segmented branched:

It is appreciated that the viscosity of the polysulfide polymer defined by the above formula can be altered by resort to a quantity other than 23 for the constituent enclosed in the parentheses.

Specifically, in the constructed embodiment of the invention, BFC poiysuliide sealant No. 44-169, a product f Better Finishes and Coatings Company lof Clifton, New Jersey, was used to form gasket 13. This synthetic rubber sealant is characterized by a tenacious adhesion to glass, metals, etc., and remains resilient throughout a temperature range from 60 F. to 23() F. The tube and safety plate bonded with this sealant was subjected to and successfully withstood an induced implosion test of the type prescribed by the Underwriters Laboratories for television cathode-ray tubes.

An adhesive gasket of the type herein considered can also be compounded of other synthetic rubbers. For example, a .polyurethane -polymer cured with a polyol such as polyester or polyether provides an excellent bonding sealant as does a silicon rubber base suitably cured by an oxidizing agent.

As will be shown the material constituting gasket 18 is applied as a lbead of paste by one of several methods to be described. Accordingly, a series of small temporary spacers 19, see FEGURE 2, are first interposed between the faceplate and the safety Window and along their confronting peripheral portions to maintain a minimum spacing between faceplate 13 and safety plate 17 until the gasket material cures to a rubber-like consistency. Preferably, the spacers are constructed of a compliant material such as felt, soft rubber, etc., and are aixed, .as by an adhesive, to either faceplace 13 or safety window 17 before the gasket material is applied. Four spacers have been found sufficient for rectangular as well as round cathode-ray tubes. Moreover, so long as t-hey are of a yieldable material, the spacers need not be removed after the gasket material sets up since they have no adverse effect on the bonding ability of the gasket. On the other hand, and as will be demonstrated, the requisite spacing can be secured without recourse to spacers by apparatus to lbe described. In any case, it is Ionly necessary that the requisite spacing be maintained a time suflicient for the bead of adhesive to cure since once the adhesive has cured, the resultant gasket constitutes the sole Imeans for securing safety window 17 to the cathode-ray tube.

Referring now to FIGURE 3, there is illustrated an apparatus for practicing one method of constructing a cathode-ray tube of the type herein considered. As shown, tube 111 is supported face up in a rotatable cradle 22 at a sealant dispensing station. lt should be recognized that this sealant dispensing station can be one of a series of stati-ons encountered by tube 10 during its manufacture and that the tube and cradle are transportable to other stations for such additional processing as may be required as by a conveyor. Cradle 22 includes a collar 23 which is engaffeable with a drive pinion 24. A pressure operated dispensing gun 25, connected to a supply of adhesive sealant, is pivotally supported adjacent tube 1S for displacement from the depicted operative position to a storage position. The nozzle of gun 25 is most advantageously fitted with a guillotine type shut-off valve in orderthat the iiow of the sealant can be instantaneously started or stopped. Thevalve itself is desirably controlled by a remotely actuated solenoid which is synchronized with drive pinion Z4.

Also located at the sealant dispensing station is a safety window transport 27 comprising a vertically displaceable hollow post 28 which communicates, at one end, with a vacuum pump, not shown, and, at the other end, with a suction cup 29 which engages the outside surface of safety window 17. In this manner safety window 17 is releasably supported over faceplate 13 and with its periphery in alignment with the periphery of faceplate 13.

The processing steps entailed in bonding safety window 17 to tube 10 with the apparatus of FIGURE 3 are instituted by inserting a tube in cradle 22 at a prior station and Iattaching a safety plate having previously affixed spacers 19 to suction cup 29. Alternatively, the spacers may be affixed to the periphery of faceplate 13. In any event, upon arriving at the sealant dispensing station, `drive pinion 24 is mechanically coupled to cradle collar 23 and gun 2.5 is pivoted from its storage position te the illustrated operative position in which the iiozzleis poised over the periphery of faceplate 13. Then, simultaneously, drive pinion 24 is actuated to rotate tube 10 at a constant speed and the guillotine valve of gun 25 is opened.- -ii this fashion 4a continuous uniform bead of adhesive' sealant is deposited on the peripheral portion of faceplate 13, see FIGURE 3a. After one revolution of tubel 10, drive pinion 24 is disengaged from collar 23,- the shut off valve for gun 25 is closed and the gun is swung out to the storage position. The viscid nature of the sealant prevents it from running down the side of the envelope, in fact its Visco-sity is such that it would not run or drip even if t-he envelope was inverted. When the gun is clear of the faceplate, post 28 is lowered permitting safety plate 17 to contact the bead 18 of sealant and spread the material upon the confronting peripheral portions `of the safety plate and faceplate. If spacers 19 have previously been applied to the safety window or to the faceplate, the vacuum holding force in cup 29 is released permitting' safety window 17 to settle upon spacers 19 and bead 1S. The tube and cradle are then transferred to a subsequent processing station Where curing of the sealant to a rubberlike consistency is accelerated as by applying heat.

On the other hand, if spacers are not used, post 28 retains support of Window 17 when it contacts the bead of sealant 18 and maintains the requisite spacing 0f the window from the faceplate while heat is applied to the bead to accelerate curing of the sealant. When the sealant cures to a resilient gasket of sufficient body to support the weight of window 17, the window is released from cup 29.

It is further appreciated that means other than spacers 19 and post 28 can be employed to maintain a desired spacing between windows 17 and faceplate 13 until the polysulfide sealant cures.

An alternative construction for a bonded cathode-ray tube contemplates a modification of the bonding gasket to include a mounting guard or cushion for the tube. To this end, and as exemplified in FIGURES 4 and 4a, such a gasket 35 comprises a principal bonding section 36 which is disposed, as in the principal embodiment, between the confronting peripheral portions of faceplate 13 and window 17 and a collar 37 which surrounds the frontal periphery of window 17. Collar 37 serves as a resilient mount for the tube in that it abuts the escutcheon or inner wall of the television cabinet when the tube is installed in a receiver. As an additional safe-guard, collar 37 preferably extends across the edge of safety plate 17 and down to crown 14 of the face plate. In this fashion collar 37 protects the edge of window 17 during subsequent handling of the tube.

As in the principal embodiment gasket 35 can be compounded of a synthetic rubber which is applied in paste form. Insofar as the processing ofthe alternate tube construction is concerned, at least two approaches are available. Window 17 can initially be bonded to .faceplate 13 by resort to the apparatus and technique detailed in the discussion of FIGURE 3. Thereafter collar 37 is added simply by raising gun 25 until it clears window 17 and then returning it to the operative position so that the nozzle of gun 25 is now poised over the rim of the safety window. A second bead of paste is then deposited on the rim of window 17 and crown 14 of the faceplate as tube rotates through one revolution. Upon curing the two beads of sealant unite to form gasket 35.

Alternatively, gasket 35 can be formed by the apparatus shown in FIGURE 4 which, except for one detail, is the same as that of FIGURE 3. The only significant difference in the FIGURE 4 mechanism resides in the use of a multiple nozzle gun This gun extrudes two contiguous beads of sealant thereby permitting gasket 3S to be formed by a single sealant dispensing operation.

In practicing the alternative method, prior to the sealant dispensing step, a series of spacers 19 having previously deposited layers of adhesive on each end are affixed about the periphery of faceplate 13. Window 17 is then aligned over face plate 13 and lowered onto the spacers. Upon making contact the adhesive on the exposed ends of the spacers secure the window in position for the next step. The tube is thus presented to the sealant dispensing station with window 17 already in place. The tube drive pinion 24 and gun 25 are then actuated. The lower nozzle of gun 25' discharges adhesive sealant at a pressure sufficient to force the sealant between the confronting peripheral portions of the safety window and faceplate a distance short of viewing area 16 of the faceplate. Simultaneously, sealant is discharged from the other nozzle of gun 25 onto the rim of window 17 and the crown 14 of the faceplate. As in the previously described gasket forming processes, the valve of gun 25 is closed at the completion of one revolution of tube 10 and the gun is returned to an inoperative or stand-by position. The tube and cradle are then transported to a different station where the sealant is heat-cured to form` resilient gasket 35.

In each of the gasket forming processes thus far described, the adhesive sealant has been deposited upon the peripheral portion of a cathode-ray tube face plate which is oriented face up. It is recognized, of course, that the positions of the tube and window can be inverted and that the sealant can be deposited upon the periphery of the safety window prior to lowering the tube upon the window. Moreover, because of the adhesion the described sealants demonstrate for glass, neither the faceplate of the tube nor the safety window need be oriented in a horizontal plane. By the same token the constituency of the sealants is such that a deposited bead of sealant will cling to the receiving surface without running or dripping. Accordingly, in practicing the inventive processes, the orientations of the tube and safety window are immaterial. It is also of no consequence whether the sealant is applied to the faceplate of the tube or to the periphery of the safety window. The end product is the same in any case;

a cathode-ray tube having a safety window bonded thereto solely by a resilient gasket formed of a curable synthetic.

rubber base sealant.

The invention need not be limited to a tube employing an essentially flat safety window of the type shown in FIGURES 1-4 but also contemplates the alternate embodiment shown in FIGURE 5. This embodiment cornprises a tube 10 substantially identical to that shown in FIGURES 1-4, in which like parts are identified by like but primed, reference numerals. The safety plate 50 however comprises, in addition to a viewing panel 51, a fiange 52 which extends back from panel 51. The FIG- URE 5 construction may also employ spacers 19 to maintain the required minimum spacing between window 50 and faceplate 13. A gasket 53, comprising a cured bead of sealant, is interposed between the confronting peripheral portions of safety plate 13 an-d viewing panel 51 to bond window 50 to faceplate 13 and effect a hermetic seal therebetween. By way of distinction, gasket 53 extends from the aforesaid peripheral portions back over crown 14 to the rim of flange 52.

Gasket 50 is formed, preferably, by following the technique previously described in using the apparatus shown in FIGURE 3. An advantage of the FIGURE 5 embodiment resides in the development of a wider bonding gasket. This obtains by virtue of a spreading of the sealant as the face plate and window are joined.

It is appreciated of course that a very significant percentage of the cathode-ray tubes employed in television receivers today are of the rectangular type. Accordingly, while the foregoing teaching has related to round-faced picture tubes, it should be recognized that the invention is equally applicable to rectangular picture tubes. Apparatus for applying a bead of seaalnt to the periphery of a rectangular picture tube is rather complicated in comparison to that required for a round-faced picture tube. For example, the sealant dispensing gun must be so controlled as to oscillate back and forth in order to follow the periphery of a rectangular tube as the tube rotates. Additionally, the tube must be driven at a variable speed in order that the peripheral speed of the tube, as it passes beneath the nozzle of the dispensing gun, remains constant. An oscillating path for the gun can be achieved by having it respond to a cam having a track which corresponds to the outline of the rectangular tube being processed. Likewise, the speed of the cathode-ray tube can also be controlled by a drive cam having a profile related to the outline of the rectangular tube. In this fashion the peripheral speed of the rim of the tube passing beneath the gun remains constant thus assuring the disposition of a continuous uniform bead of sealant upon the periphery of the faceplate. Therefore in order to avoid unduly complicating the drawings and specification discussion has been limited to the round-faced tube.

It is further recognized that the cathode-ray tube itself can be bonded to a support frame or bezel with one of the adhesive sealants described above. In essence, such a support comprises a fian-ge having a dished portion depending therefrom. The `dished portion is centrally ported or relieved to permit -displafy of the viewing screen and has [overall dimensions greater than those of the tube faceplate. At selected stations about its perimeter the fiange is aperture'd or :in some other fashion provided with means which permit attaching the frame to an associated chassis or cabinet.

The tube is united with the frame by nesting the frontal or display part of its envelope in the dished portion of the frame and then filling the space between the envelope Wall and the frame with one of the aforementioned adhesives. Upon curing, the adhesive effects a permanent bond between the tube an-d the frame. Such an assembly achieves significant economies in that straps and other hardware formerly required to secure the tube to the chassis or cabinet are eliminated, as are attendant assembl-y costs.

While particular embodiments of the present invention have been shown and described, it is app-arent that changes and modifications may :be made therein without dep-arting from the invent-ion in its `broader aspects. The aim of the appended claims, therefore, is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

I claim:

1. A cathode-ray tube comprising:

an envelope having a curved screen-bearing face plate with a predetermined viewing area;

a safety plate including a transparent section having overall dimensions greater than those of said viewing area and a .curvature conforming substantially to the curvature of said face plate;

and bonding means for securing said safety plate in an overlying spaced relation to said face plate, said bonding means consisting of a continuous layer of adhesive paste in intimate contact with and confined to confronting portions of said envelope and said safety plate outside of said face plate viewing area and cured to constitute a resilient gasket capable of yielda-bly accommodating displacement of said safety plate relative to said face plate.

2. A cathode-ray tube comprising:

a safety plate including a transparent section having overall dimensions greater than those of said viewing area and a curvature conforming substantially to the curvature of said face plate;

and bonding means for securing said safety plate in an overlying spaced relation to said face plate and hermetioally sealing the space therebetween, said bonding means consisting of a continuous layer of adhesive paste in intimate contact with and confined to confronting portions of sai-d envelope and saidsafety plate outside of said face plate viewin-g area and cured to constitute a resilient lgasket .capable of yieldably accommodating displacement of said safety plate relative to said face plate.

3. A `cathode-ray tube comprising:

a safety plate including a transparent section having overall `dimensions greater than those o-f said viewing area and a curvature conforming substantially to the curvature of said face plate;

bonding means for securing said safety plate in an overlying spaced relation to said face plate and hermetically sealing the space therebetween, said bonding means consisting of a continuous layer of adhesive -paste in intimate contact with confronting portions of said envelope and said safety plate outside of said face plate viewing area and cured to constitute a resilient gasket capable of yieldably accommodating displacement of said safety plate relative to said face plate;

and an edge guard for said face plate consisting of a bead of adhesive paste disposed along the juncture of said envelope and said safety plate and extending onto the outer peripheral edge portion of said safety plate a distance short of said face plate viewing area and cured to form a resilient cushion.

4. A cathode-ray tube comprising:

a safety plate including a transparent section having overall 4dimensions greater than those of said viewing area and a curvature conforming substantially to the curvature of said face plate;

spacer means interposed between said face plate and said safety plate for establishing -a minimum spacing therebetween;

and 'bonding means for securing said safety plate in an overlying spaced relation to said face plate and hermetically sealing the space therebetween, said. bonding means consisting of a continuous layer of adhesive paste in intimate contact with and confined to confronting portions of said envelope and said safety plate outside -of said face plate viewing area and cured to constitute a resilient `gasket capable of yieldably accommodating displacement of said safety plate relative to said face plate.

5. A cathode-ray tube comprising:

a safety plate comprising a transparent section having overall dimensions greater than those of said viewing area and a curvature .conforming substantially to the curvature of said face plate and a dangle portion folded back from said transparent section;

and bonding means for securing said safety plate in overlying Aspaced relation to said face plate and hermetically sealing the space therebetween, said bonding means consisting of a continuous layer :of adhesive paste in intimate contact with and confined to confronting portions of said envelope and said safety plate flange outside of said face plate viewing area and curved to constitute a resilient gasket capable of yieldably accommodating displacement of said safety plate relative to said face plate.

6. The method of assembling a cathode-ray tube having a curved screen-bearing face plate with `a predetermined viewing area and a safety plate having a transparent section with overall dimensions greater than those of the face plate viewing area and a -curvature conforming substantially to the curvature thereof, which method comprises the following steps:

supporting said cathode-ray tube with its face plate disposed in a preselected plane;

applying a la-yer of adhesive paste to a selected peri-pheral portion of `at least one of said plates and only outside a yborder defined by said face plate viewing area;

positioning said safety plate in an overlying relation with said face plate and with the peripheral portions 'of said plates substantially aligned and in intimate contact with said adhesive;

and maintaining said safety plate and: face plate in a spaced relation and said peripheral portions -of said plates in contact with said adhesive for a period of time sufcient to cure said adhesive and bond said safety plate to said cathode-ray tube.

7. The method of assembling a cathode-ray tube having a curved screen-bearing face plate with a predetermined viewing area and a safety plate having a transparent section with overall dimensions greater than those of the face plate viewing area and a curvature conforming substantially to the curvature thereof; which method oomprises the following steps:

supporting said cathode-ray tube with its face plate disposed in a substantially horizontal plane;

applying a layer of adhesive paste to a selected peripheral portion of said face plate and only outside the border defined by said face plate viewing area;

positioning said safety plate in an overlying relation to said face plate and with the peripheral portions of said plates substantially aligned and in intimate contact with said adhesive;

and maintaining said safety plate and said face plate in a spaced relation and said peripheral portions of said plates in Contact with said ladhesive for a period of time sutiicient to cure sai-d adhesive and bond. said safety plate to said cathode-ray tube envelope.

8. The method of assembling a 4cathode-ray tube having a curved screen-bearing face plate with a predetermined viewing area and a safety plate having a transparent section with 'overall dimensions :greater than those of the face plate viewing `area and a curvature conforming substantially to the curvature thereof, which method cornprises the following steps:

supporting said cathode-ray tube with its face plate Idisposed in a substantially horizontal plane and with said safety plate mounted upon and in a spaced aligned relation to said face plate; applying a layer of adhesive paste to selected confronting peripheral portions of said plates and only outside the border defined by said face plate viewing area; and maintaining said safety plate and said face plate in a said spaced relatio-n and said mripheral portions lof said plates in contact with said adhesive for `a period of time sufficient to cure said adhesive and bond said safety plate to said cathode-ray tube envelope. 9. The method of assembling a cathode-ray tube having a curve-d screen-bearing face plate with a predeter- :mined viewing area and a safety plate having a transparent section with overall `dimensions greater than those of the face plate viewing area and Ia curvature conforming substantially to the curvature theenof, vwhich method comprises the following steps:

supporting said cathode-ray tube with its face plate dsiposed in a preselected plane; applying |a rst layer of adhesive paste to a selected peripheral portion of said face plate outside .a lborder defined -by said face plate viewing area; positioning said safety plate in an overlying relation to said face plate and with the peripheral portions of said plates substantially aligned and in intimate conytact with said adhesive;

applying a second layer of adhesive paste along the periphery of said safety plate and extending onto .said safety plate a distance short of said face plate viewing area;

and maintaining said safety plate and said face plate in a spaced relation and said peripheral portions of said plates in contact with said first layer of adhesive for a period of time suflicient to cure said first lalyer to bond said safety plate to said cathode-ray tube envelope and to cure said second layer t-o pnovide a resilient peripheral cushion for said safety plate.

References Cited by the Examiner UNITED STATES PATENTS 2,293,529 8/ 1942 Bedford l78-7.82 X 3,113,347 12/196-3 Kufrovich 220-2.1 X 3,130,854 4/1964 Casciari 220-2.1

FOREIGN PATENTS 904,616 8/ 1962 Great Brit-ain.

THERON E, CONDON, Primary Examiner. MARTHA L. RICE, Examiner.

Claims

1. A CATHODE-RAY TUBE COMPRISING: AN ENVELOPE HAVING A CURVED SCREEN-BEARING FACE PLATE WITH A PREDETERMINED VIEWING AREA; A SAFETY PLATE INCLUDING A TRANSPARENT SECTION HAVING OVERALL DIMENSIONS GREATER THAN THOSE OF SAID VIEWING AREA AND A CURVATURE CONFORMING SUBSTANTIALLY TO THE CURVATURE OF SAID FACE PLATE; AND BONDING MEANS FOR SECURING SAID SAFETY PLATE IN AN OVERLYING SPACED RELATION TO SAID FACE PLATE, SAID BONDING MEANS CONSISTING OF A CONTINUOUS LAYER OF ADHESIVE PASTE IN INTIMATE CONTACT WITH AND CONFINED TO CONFRONTING PORTIONS OF SAID ENVELOPE AND SAID SAFETY PLATE OUTSIDE OF SAID FACE PLATE VIEWING AREA AND CURED TO CONSTITUTE A RESILIENT GASKET CAPABLE OF YIELDABLY ACCOMMODATING DISPLACEMENT OF SAID SAFETY PLATE RELATIVE TO SAID FACE PLATE.