US3377493A - Clip for mounting peripheral electron shield on shadow mask of color television tube, provided with contact spring to tube inner coating - Google Patents

Description

April 1968 N D. LEVIN ET AL 3,377,493

CLIP FOR MOUNTING PERIPHERAL ELECTRON SHIELD ON SHADOW MASK OF COLOR TELEVISION TUB PROVIDED WITH CONTACT SPRING TO TUBE INNER COATING 2 Sheets-Sheet 1 Filed Feb. 15, 1967 "a W n N n E L A Va m H or H U h 0H NA Aprxl 9, 1968 N. D. LEVIN ET AL 3,377,493

CLIP FOR MOUNTING PERIPHERAL ELECTRON SHIELD-ON SHADOW MASK OF COLOR TELEVISION TUBE, PROVIDED WITH CONTACT SPRING TO TUBE INNER COATING Filed Feb. 15, 1967 2 Sheets-Sheet 2 A I V o INVENITORJII fig- ,5

Patented Apr. 9, 1968 ABSTRACT OF THE DISCLOSURE Fastening apparatus for securing an electron shield to the mask frame of a color television picture tube, without the necessity of weldments. The configuration of the fastening apparatus precludes its accidental removal after installation on the mask frame, and may also include an electrical contact member for providing a current path between the frame and the interior conductive coating of the picture tube.

Disclosure This invention relates in general to color television picture tubes, and in particular to means for securing electron shielding members to the mask frame thereof, without welding. More particularly, this invention relates to self-restoring resilient clip fasteners for securing electron shields to a portion of the mask frame of a color television picture tube, wherein at least one of said clip fasteners may also include an integral electrical contact member providing a current path between the frame and an interior conductive coating.

conventionally, color television picture tubes comprise a funnel shaped glass envelope having a face plate assembly sealing its flared end, and an electron gun providing a source of electrons mounted in the funnel neck. An electron excitable phosphor screen is deposited on the interior surface of the face plate, oriented for exposure to the source of electrons emitted by the electron gun. A fragile aperture mask is interposed between the electron gun and the phosphor screen, closely adjacent the latter, and is supported in the face plate assembly by a heavy rigid frame, conventionally called a mask frame.

The mask frame is substantially smaller than the face plate assembly in which it is mounted, consequently, an open space or gap exists between the outer edge of the frame and the side wall of the face plate assembly. Under certain electron beam deflection conditions, some electrons are deflected beyond the frame outer edge and enter the gap between it and the side wall of the face plate. Many of these misdirected electrons strike the face plate side wall at an angle which causes them to ricochet onto the screen. As these electrons strike the screen, they cause random exciting of the phosphor around the edges, an obviously undesirable occurrence.

To eliminate this undesirable occurrence, it is wellknown in the art to provide an electron shield to block the space between the mask frame and the face plate assembly. The electron shield is maintained at the same potential as the mask and mask frame, thus providing a conductive path for those electrons directed beyond the outer edges of the frame.

Typically, electron shields are fabricated of heavy gauge metal and are secured to the frame by spot welding. Since the electron shield extends around the entire periphery of the mask frame, a substantial amount of spot welding is required. Further, the electron shield is normally spot welded to the frame subsequent to securing the aperture mask thereto, and while the frame and mask are mated with the screened face plate assembly. Consequently, there was the continual problem of unavoidable splatter from the spot Welding damaging the fragile aperture mask usually by plugging or filling some of its small holes, or injuring the phosphor screen.

It is obvious that plugged mask holes impede the passage of electrons therethrough, thus creating a blank area on the screen. The same result would be caused by injury to the phosphor screen. While various arrangements exist to protect the aperture mask and screen from splatter, all are time-consuming and damage still occasionally occurs, causing unnecessary expense.

In addition to spot welding the electron shield to the mask frame, at least one, and preferably two electrical contact members are also usually welded to the frame. These contact members provide a current path between the mask frame and the interior conductive coating of the picture tube, thus completing a high voltage path between the anode connection and the aperture mask. Obviously, the additional weldments afford further opportunity for damaging the aperture mask and the phosphor screen.

The difliculties incident to performing welding operations adjacent the aperture mask and screen dictate the desirability of eliminating such operations where practical. To this end, at least one prior art clip has been designed for securing an electron shield to a mask frame. This clip is fabricated of resilient material for installation on a mask frame, and is maintained thereon by compressing an edge of the frame between its opposing legs. The shield was held in place by one of the clip legs urging it against the frame.

This prior art clip had limited holding capabilities since its holding strength depended entirely upon the resilience r of the material from which it was fabricated. Consequently, the prior art clip was subject to disassociation from the mask frame upon vibration or shock imposed upon the picture tube, with a consequent movement of the electron shield. When using the clip discussed above, the electrical contact members were still affixed by spot welding.

This invention obviates many of the difficulties heretofore experienced in securing an electron shield to the mask frame of a color television picture tube, by providing a clip fastener of unique design. The clip fastener comprises two resiliently connected legs which straddle the lip and adjacent section of the mask frame and are in physical contact therewith in such a manner as to establish a torsional moment thereabout for counteracting external forces attempting to remove it. The clip fastener is easily installed on the mask frame during assembly of the picture tube, thereby eliminating a welding operation and incidental splattering which heretofore existed in connection with securing the electron shield to the frame.

In addition, the invention eliminates the difficulties heretofore created by Welding an electrical contact member to the mask frame for establishing a current path between the mask frame and the interior conductive coating. This is accomplished by forming the contact member as an extension of one of the clip legs. Thus, another possibility of splattering is eliminated and with its elimination, the reduction of possible damage to the aperture mask.

Accordingly, the primary object of this invention is to provide improved means for securing an electron shield to a mask frame.

It is also an object of this invention to provide resilient clip means for securing the electron shield to the mask frame of a color television picture tube, wherein said clip means is designed to counteract external forces tending to remove it from said frame.

A further object of this invention is to provide, in a color picture tube, combination resilient means for securing an electron shield to a mask frame and for establishing a conductive path between said mask frame and a conductive coating on the interior of said picture tube.

An additional object of this invention is to eliminate the weldments usually required for securing electrical contact members to the mask frame, thereby reducing the possibility of damage to the aperture mask and the phosphor screen.

FIG. 1 is a partially broken, sectional view of a color television picture tube embodying the invention.

FIG. 2 is an enlarged three dimensional view of a resilient clip fastener for securing an electron shield to a mask frame. Also shown, is an enlarged perspective view of an electrical contact member which is normally integral with at least one clip fastener in each picture tube.

FIG. 3 is a slightly perspective view taken along line 33 of FIG. 1 showing one possible arrangement of the clip fasteners around the mask frame, and also showing possible locations of several combination clip fasteners and electrical contact members on the frame.

FIG. 4 is an enlarged cross sectional view taken along line 4-4 of FIG. 3 and including a portion of the funnel, showing a clip fastener seated on the mask frame with an electrical contact member contacting the conductive coating covering a major portion of the picture tube interior.

Turning to consideration of the drawings and in particular to FIG. 1, there is shown a color television picture tube which includes a glass envelope 10, comprising a funnel 12, and a face plate assembly 14 secured to the funnel by special sealing means 15. The interior surface of the face plate assembly provides a substrate for a screen comprising a deposited triad phosphor dot structure 16, well-known by those familiar with the art. The glass envelope houses an aperture mask 18 which is accurately maintained closely adjacent the phosphor dot structure by a rigid mask frame 20. The mask frame includes a lip 21 and a central portion 23. In addition, it has a plurality of outwardly biased locating springs 24 welded thereto, and is supported in the picture tube by these springs which cooperate with an equal number of integrally molded studs 22.

An electron gun 26 is permanently sealed in the neck of funnel 12, facing the phosphor screen. As is wellknown by those familiar with the art, beams of electrons are emitted from the electron gun and pass through the holes in the aperture mask. After passing through the aperture mask, the electrons impinge the phosphor dot structure, exciting the phosphor and illuminating portions thereof to form an image.

As can be seen in FIG. 1 and even more clearly in FIG. 4, a space a exists between an outer edge 30 of the mask frame and an inner surface 31 of the face plate assembly. Misdirected electrons, such as those which are deflected beyond edge 30, could pass through this space, strike surface 31 and rebound onto the screen, randomly exciting the phosphor at the perimeter. An example of the path of one such misdirected electron is shown by a dashed line in FIG. 1.

To preclude this random exciting of the peripheral phosphor coating, which is obviously undesirable, electron shields 32 and 33 are provided (FIG. 3). These electron shields, one of which may be provided for each side of a television picture tube having a rectangular configuration, fill the space between the outer edge 30 of the mask frame and inner surface 31 of the face plate assembly. The shields are maintained at a high potential by means explained below, thereby preventing electrons from reaching the phosphor screen.

The electron shields, which may be fabricated of aluminum or other conductive material, are maintained in position by resilient clip "fasteners. Two basically similar clip fasteners, 34 and 36 are provided. Fastener 34 is solely a resilient clip for securing the elec- 4 tron shield to the frame, while fastener 36 is a combination clip fastener and electrical contact member. One possible arrangement of fasteners 34 and 36-on frame 20, is shown in FIGS.

Referring now to FIGS. 2 and 4, a clip fastener with an electrical contact member will be described in detail, it being understood that those clip fasteners without electrical contact members, function in the identical manner.

The clip fastener is fabricated of a thin rectangular metal strip which is formed into a short leg 40, and a longer leg 42, the legs joining at an apex 44. The apex conforms to the shape of frame lip 21, rectangular in the preferred embodiment, and includes an end 46 in contact with the top of the lip. Sides 48 and-50 complete apex 44, and fit loosely against the sides of the frame lip. The ends of legs 40 and 42 are divergingly, arcuately shaped, which facilitates assembly upon the frame. The arcuate ends, which may be substantially circular, have offset centers of curvature which assists in maintaining the clip on the frame. The important aspect of the configuration of the clip legs is the point of contact between each leg and the frame. More specifically, the direction of force must not produce an identical reaction on the clip leg, but the force must 'vary by a distance b, FIG. 4. The opposing reaction forces exerted by the frame on the clip legs and the distance .therebetween, establishes a torsional moment in the direction shown by the arrow in FIG. 4. This torsional moment counteracts external forces attempting to remove the clip from the frame, and assists rescating it thereon upon movement incident to its partial removal from shock, vibration, etc.

As external forces attempt to remove the clip from the mask frame and impart movement thereto in the direction of its removal, side 50 separates from its adjacent lip wall, and side 48 is forced into contact with its adjacent wall. Simultaneously, legs 40 and 42 spread apart and the distance b between the contact of the legs with the frame increases. Thus, the torsional moment resisting its removal from the frame increases, reseating the clip thereon. During handling of a picture tube assembly, including severe handling with mechanical shock and vibration, the clip will not separate from the mask frame, although it may be manually removed by prying it with finger pressure so that the entire apex is free of the frame lip.

The electron shield is clamped between the mask frame and the longer leg 42. The clamping forces are the primary means for retaining the electron shield in place, although the configuration of the shield itself, including its curved end 51 adjacent surface 31 of the faceplate assembly and its opposite end 52 conforming to the curvature of the frame lip, also assists in holding the electron shield in place.

An electrical contact member 54, shown in perspective in FIG. 2 and in position within a picture tube in FIGS. 1 and 4, is provided to complete an electrically conductive path between the conductive aquadag coating and the aperture mask. Instead of welding the electrical contact member directly to the mask frame as was conventional in the prior art, it is secured to long clip leg 42 of at least one clip fastener, although in the preferred embodiment two clips and two electrical contact members are used. The electrical contact member may be spot welded to the long clip leg, but this should be performed at a location remote from the aperture mask to prevent the possibility of damaging splatter. The contact member extends obliquely away from the screen and toward the con ductive coating on the funnel, and is resilient to establish good electrical contact with the conductive coating.

What has been described is a resilient clip fastener for securing an electron shield to a mask frame without welding, thereby precluding the possibility of damage to the aperture mask or phosphor screen. In addition, electrical contact means are provided integral with at least one clip fastenerfor insuring an adequate current path between the mask frame and the conductive coating, without the neoessity of weldments.

It is obvious that upon study by those skilled in the art, the disclosed invention may be altered or modified both in physical appearance and construction without departing from its inventive concept. Therefore, the scope of protection to be given this invention should not be limited by the embodiment described above, but should be determined by the essential descriptions thereof which appear in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In combination: a color television picture tube having an electron activated phosphor screen; an aperture mask; a frame fixedly supporting said aperture mask closely juxtaposed said screen; a source of electrons directed at said screen through said aperture mask for selectively activating portions of said phosphor; electron shielding means for preventing fortuitously misdirected electrons from striking said phosphor screen; and clip means adapted for installation on said frame; said clip means having legs resiliently biased toward each other; said legs grasping said frame and securing said shielding means thereto by firmly clamping it between said frame and one clip leg.

2. The combination as set forth in claim 1 wherein said clip means has two legs; each of said legs coacting with said frame to establish a torsional moment resisting removal from said frame; said torsional moment maintaining said clip means on said frame thereby preventing dislocation of said electron shielding means incident to vibration or mechanical shock of said picture tube.

3. The combination as set forth in claim 2 wherein said frame includes a lip; the legs of said clip means forming an apex having a shape substantially conforming to the shape of said lip; said apex normally seated on said lip, and coacting therewith to alter contact between said legs and said frame upon attempted removal thereof, thereby establishing a restoring torsional moment to said clip means tending to reseat said apex on said frame.

4. The combination as set forth in claim 1 wherein said frame includes a lip about an edge thereof; said clip means including two opposed legs having a common apex associated with said lip; each of said legs having diverging ends arranged to assist installation of said clip means on said frame, and having an area presenting an engaging surface for contact with said frame; said legs engaging said frame in spaced apart contact and establishing a torsional moment for maintaining said clip means on said frame thereby preventing dislocation of said electron shielding means incident to vibration or mechanical shock of said picture tube.

5. The combination as set forth in claim 4 wherein said frame includes a clip means engagement portion contiguous with said lip; the engaging surfaces of said legs contacting said frame at said clip means engagement portion; and wherein the apex of said clip means has a shape substantially conforming to the cross section of said lip; the resilience of said legs and the spaced apart contact thereof with said frame establishing a restorational torsional moment for maintaining said apex in firm contact with said lip.

6. The combination as set forth in claim 5 wherein the clip engagement portion of said frame is substantially parallel to the plane of said screen, and wherein said lip is formed substantially perpendicular thereto; the apex of said clip means including an upstanding tabular member substantially parallel to said lip and butting there against to resist displacement of said clip means in a direction parallel to said screen.

'7. In combination: a color television picture tube having a non-conductive envelope; a face plate forming a front closure for said envelope and having an electron activated phosphor screen on the interior thereof; an aperture mask; a conductive frame in electrical contact with said aperture mask and supporting it within said envelope, closely adjacent said phosphor screen; an electron gun mounted in said envelope, emitting electrons through said aperture mask toward said phosphor screen for activating portions thereof; electron shielding means filling a gap between said frame and the interior of said envelope for preventing electrons which may be misdirected beyond the limits of said frame, from striking said screen; a conductive coating on the inner surface of said nonconductive envelope providing an electrical path from a source of high potential connected thereto, to a point adjacent said frame; and resilient clips adapted for installation on said frame; said resilient clips securing said electron shielding means to said frame and having conductive means completing an electrical path between said conductive coating and said frame.

8. The combination as set forth in claim 7 wherein said frame defines an open central area through which said electrons normally pass toward said screen, and wherein said clip engagement surface is outwardly of said open area; said resilient clips each comprising a reverse bend extending into a first leg and a second leg biased toward each other, and straddling said frame in contact with said clip engagement surface; each of said legs having diverging arcuate ends with offset centers of curvature establishing a torsional moment for maintaining said clip on said frame; said electron shield frictionally secured to said frame by positioning it between said first clip leg and said clip engagement surface; and wherein said conductive means comprise a resilient contact member extending from said first leg to said conductive coating.

9. The combination as set forth in claim 8 wherein said frame includes additionally; a lip adjacent said clip engagement surface; each of said clips including an apex at the junction of said legs, conforming to and mounted on said lip; said apex having at least one side in physical contact with said lip resisting transverse movement of said clip.

10. The combination as set forth in claim 9 wherein said resilient contact member is permanently fastened to the terminus of said first leg at its arcuate end, and when mounted on said frame extends outwardly therefrom in a direction away from said screen; said contact member being movable during assembly of said picture tube and exerting sufficient pressure on said conductive coating to provide an adequate electrical path between said frame and said coating.

References Cited UNITED STATES PATENTS JAMES W. LAWRENCE, Primary Examiner. V. LAFRANCHI, Assistant Examiner.

Images