US3558955A - Self supporting shadow mask with reinforcing ribs and gusset plates for colored television picture tubes - Google Patents

Abstract

A shadow mask for colored TV picture tubes has a front section, containing the conventional foraminous or translucent area formed by a multitude of miniature apertures through which electron beams pass from the electron guns at the rear of the tube to the viewing face at the front of the tube; an imperforate margin area around the translucent area; a rearward extending wall from the edge of the margin area; and an inward directed flange formed along the rear edge of the wall. The flange contains a plurality of strengthening fragmentary gusset plate members.

D R A W I N G

Description

United States Patent [72] Inventor Myron C. Kirchner Itasca, Ill.

[21] Appl. No. 821,056 [22] Filed 313/85X 3l3/85X 313/85X May 1, 1969 Patented Jan. 26, 1971 11/1969 Mears....

[73] Assignee Northern Metal Products, Inc.

Franklin Park, III.

a corporation of Delaware Assistant Examiner-V. Lafranchi Attorney-Stryker and Jacobson ABSTRACT: A shadow mask for colored TV picture tubes foraminous or translucent area formed by a multitude of miniature through which electron beams [54] SELF SUPPORTING SHADOW MASK WITH has a front section, containing the conventional REINFORCING RIBS AND GUSSET PLATES FOR COLORED TELEVISION PICTURE TUBES Figs apertures pass from the electron guns at the rear of the tube to the viewing face at the front of the tube;

. 313/85, an imperforate margin area around the translucent area; a

3 13/286, 313/348 rearward extending wall from the edge of the margin area; and H0lj 29/46 an inward directed flange formed along the rear edge of the wall ty of strengthening fragmen- 4 Claims, 3 Drawing [52] [51] Int. Cl.......

. The flange contains a plurali [50] Field of Search.

928 tary gusset plate members.

PATENTEB JAN 25 191i 'Hllh.

"Hill" INVENTOR MYRO/V BY W M ATTOIQNEYS SELF SUPPORTING SHADOW MASK WITH REINFORCING RIBS AND GUSSET PLATES FOR COLORED TELEVISION PICTURE TUBES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is used in the construction of colored TV picture tubes containing aperture or shadow masks and is principally directed toward providing a mask which is essentially self-supporting.

2. Description of the Prior Art Heretofore, for the most part, the practice has been to take aconventional shadow mask, which has its translucent area shaped to conform to the front face of the picture tube, attach it to a heavy mounting ring to form a complete assembly, and then mount the entire assembly in some convenient fashion to the inside of the glass bulb of the picture tube. The mounting ring helps to physically stabilize the mask but it and its associated hardware constitutes a sizeable portion of the mask assembly. This results in a mask assembly that is costly, heavy, and somewhat unstable because of temperature differentials during a long warmup period while the assembly approaches a uniform steady temperature level. This has produced some warping or twisting of the face of the mask which, in turn, adversely affects the registration of the mask apertures with respect to the phosphor dots on the face of a picture tube. Attempts have been made to eliminate or modify this traditional mounting ring assembly. Typical of this is the shadow mask described in US. Pat. No. 3,376,451 and that described in copending application Ser. No. 822,792 filed Apr. 2, I969 by the present applicant.

SUMMARY I The present invention is somewhat of a variation or modification of the aperture mask described in the aforementioned copending application. The mask contains the conventional translucent area surrounded by an imperforate marginal area, has a rearward extending imperforate wall and an inward extending flange at the rear edge of the wall. Numerous strengthening ribs are in the various imperforate sections to assist in providing enough strength to make the mask self supporting. Fragmentary gusset plate members are welded at strategic locations on the flange to provide additional strengthening while keeping the weight and mass of the mask at a minimum. A mask of this nature not only warms up to uniform operating temperature quickly but also is rigid enough to withstand normal handling without any significant shift in the location of the tiny apertures. Masks of this nature can be attached to the glass bulb by springlike mounting tabs located on the wall section and containing openings for mating with mounting studs in the glass bulb.

BRIEF DESCRIPTION OF THE DRAWINGS F IG. 1 is a rear view of a shadow mask for a colored TV picture tube constructed according to the teachings of this invention;

FIG. 2 is a side view of the shadow mask; and

FIG. 3 is a sectional view taken along viewing line 3-3 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The aperture or shadow mask contains the conventional foraminous or translucent area formed by a myriad of apertures which are usually chemically milled through a thin sheet of metal, such as stainless steel. In normal use, when made part of the final picture tube assembly, the translucent section 10 of the shadow mask is located near and facing the front viewing face to of the picture tube and is between the viewing face and electron guns at the rear of the tube. When the tube is in operation, the electron beams are directed through the translucent area 10 to impinge upon colored phosphor dots on the inside of the face of the picture tube. The shadow mask is also used during the process of laying down the colored phosphor dots in conventional triad patterns. Without delving into this process to any great degree, it should be pointed out that during the process of forming the phosphor dots the mask ordinarily is removed and repositioned with respect to the face of the picture tube a number of times so it is important that the mask be stable enough so that the tiny apertures return virtually to their same previous location each time the mask it is temporarily removed and reinserted. It should also be apparent that the mask should be temperature stable so that the miniature apertures in the translucent area do not shift with respect to the phosphor dots on the industry face plate to interfere with the passage of the electron beams directed toward the face plate.

Conventionally, the translucent area 10 is partially domed or curved, usually aspherically, to conform to the shape of the inner face of the picture tube. Various methods, procedures and equipments have been developed and are used today throughout the industry for etching out the translucent areas and for doming or curving the mask face as desired. These methods, procedures and equipments are not considered part of the present invention.

Surrounding the translucent area 10 is a marginal imperforate area 11 which is merely an extension of the same sheet of metal from which the translucent area is formed. In marginal area 11, near the outer edge of the translucent area 10, there is formed a continuous, inwardprojecting shallow groove 12 which serves as a strengthening rib for the front portion of the aperture mask. Ordinarily, this rib is formed in a press using standard well-known techniques. At the outer edge of the marginal area 11 the metal sheet bends rearward to form an imperforated wall section 13 which extends completely around the front portion of the mask. The depth of the wall section 13, Le. its dimension from front to back, may vary from mask to mask depending upon a number of factors ineluding, but not limited to, the size an and the type of the picture tube for which the mask is being made. However, in general terms, the mask is referred to as being deep-drawn as differentiated from a shallow-drawn mask which has a very short wall section. Typically, with no limitation intended, the wall may be in the order of l inches deep for an aperture mask used in a 21 or 24 inch picture tube. A shallow, inwardly directed groove 14 which extends continuously around wall 13 provides a strengthening rib for the wall section. The location and size of strengthening rib 14 depends on a number of factors including the size of the mask, the dimension of the wall, the metal thickness, etc. This choice can be and ordinarily is made by the skilled artisan depending on the various factors and no precise formula for covering the various conditions appears to be reasonably predeterminable. In some instances, it has been found that additional strengthening ribs may be desirable. These may be the same as and run parallel to rib 14 or they may meander over the wall section 13.

At the rear edge of wall l3 the metal sheet bends inward to form flange 16 in a plane which is substantially at to the central axis of the aperture mask. The dimension of flange I6 also depends on a number of different factors but suffice is to point out that it should not extend inward so far as to interfere with the passage of the electron beams from the electron guns to the viewing face of the tube. The inner edge of flange 16 may be flared angularly as illustrated at 18, to provide some degree of shielding. As shown in FIG. 1, flange I6 is in a rectangular geometric form corresponding in general with the geometric form of the aperture mask for use with a rectangular picture tube. Attached securely to the four corners of flange 16 are reinforcing gusset plate members 19. Preferably, the gusset plate members are attached by welding them to the flange. Also, preferably, the gusset plates 19 are made out of the same type of metal as the rest of the mask and dimensionally may be the same thickness as the metal sheet from which the mask is formed. However, it has been found preferable that the gusset plate members 19 be in the order of twice the thickness of the flange material. Although it has been found that in most instances the corner-located gusset plate members 19 provide sufficient strengthening for the desired results, in some instances it may be necessary or desirable to enhance the strength of the mask by welding additional girsset plate members at suitable locations between corner gusset members. Typically, fragments of metal similar to gusset plate members 19 may be welded to flange 16 at the center of each of the sides of the flange. The sizes of these additional gusset plate members may be selected according to the degree of additional strength desired while keeping in mind the necessity of keeping the mass and the weight of the mask structure at a minimum.

Directing attention back to FIG. 2, wall 13 may be provided with additional strengthening and supporting ribs 23 which run across the continuous rib 14. The number. dimensions and the spacing of these cross ribs 23 again is a matter of choice depending on a number of factors and can be selected by the artisan familiar with construction of masks of this nature. Attached to the outside of wall 13 are springlike mounting tabs 20 which contains openings 21 on tongue portions 22 for mating with pins (not shown) extending out from the glass bulb of the picture tube. Because of the inherent strength of the mask brought about by the supporting ribs in conjunction with the suitably located gusset plate members, it can be used in the phosphor dot forming process and be mounted as part of the final assembly of a the picture tube and remain secure in this virtually self-supporting manner without the need of the usual heavy, rigid supporting rings and mounts which had been commonplace heretofore.

I claim:

1. A self-supporting shadow mask for a colored television picture tube comprising: a thin metal sheet having a front section containing a translucent area defined by a myriad of miniature apertures through the metal sheet and an imperforate margin area surrounding the translucent area with a continuous strengthening rib formed in said margin area, an imperforate wall section extending rearward from the edge of said from section, said wall section containing strengthening ribs formed therein, a flange section directed inwardly from the back edge of said wall section, said flange section being generally rectangular in shape; and fragmentary gusset plate members rigidly attached to said flange section at its four corners.

2. The invention as described in claim 1 further including further fragmentary gusset plate members rigidly attached to a said flange at locations between the corner gusset plate members.

3. The invention as in claim 1 wherein the front section, the wall section and the flange section are all formed from a single sheet of metal.

4. The invention as in claim 3 wherein the gusset plate members are made from metal having the same characteristics as the mask metal and range up to three times its thickness, said gusset plate members being welded to the flange section.

Claims (4)

1. A self-supporting shadow mask for a colored television picture tube comprising: a thin metal sheet having a front section containing a translucent area defined by a myriad of miniature apertures through the metal sheet and an imperforate margin area surrounding the translucent area with a continuous strengthening rib formed in said margin area, an imperforate wall section extending rearward from the edge of said front section, said wall section containing strengthening ribs formed therein, a flange section directed inwardly from the back edge of said wall section, said flange section being generally rectangular in shape; and fragmentary gusset plate members rigidly attached to said flange section at its four corners.

2. The invention as described in claim 1 further including further fragmentary gusset plate members rigidly attached to a said flange at locations between the corner gusset plate members.

3. The invention as in claim 1 wherein the front section, the wall section and the flange section are all formed from a single sheet of metal.

4. The invention as in claim 3 wherein the gusset plate members are made from metal having the sAme characteristics as the mask metal and range up to three times its thickness, said gusset plate members being welded to the flange section.

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