US3524971A

US3524971A - Shadow mask mounting brackets moving mask toward screen with radial mask expansion

Info

Publication number: US3524971A
Application number: US608562A
Authority: US
Inventors: James W Schwartz; Laslo J Javorik
Original assignee: National Video Corp
Current assignee: National Video Corp
Priority date: 1967-01-11
Filing date: 1967-01-11
Publication date: 1970-08-18
Anticipated expiration: 1987-08-18

Description

1970 r J. w. SCHWARTZ ETAL 3,524,971 SHADOW MASK MOUNTING BRACKETS MOVING MASK TOWARD SCREEN WITH RADIAL MASK EXPANSION INVEJVTORS: JAMES W. SCHWARTZ LASLO J. JAVORIK Filed Jan. 11, 1967 d ATT'YS 3,524,971 fice Patented Aug. 18, 1970 U.S. Cl. 313-85 2 Claims ABSTRACT OF THE DISCLOSURE A color television tube mask mounting adapted to substantially compensate for the mechanical shift of the mask openings during operation. The mask mounting is constructed to move the mask axially so as to maintain register of the mask openings with the electron paths which extend from the guns to the phosphor dots.

SUMMARY OF INVENTION The inventive mask mounting includes a unique coupling for interconnecting a post or like rigid piece on the envelope of the television tube with the shadow mask. The coupling is responsive to the change in size of the shadow mask so as to move the same in a direction parallel to the axis of the tube.

The invention is explained in conjunction with the accompanying drawing in which- FIG. 1 is a fragmentary elevational View of the faceplate portion of a rectangular color television tube, with the above-mentioned mask mounted in place;

FIG. 2 is a fragmentary cross-sectional view such as would be seen along the sight line 2-2 applied to FIG. 1, the showing in FIG. 2 being on enlarged scale, relative to FIG. 1;

FIG. 3 is a schematic representation of the movement of a particular shadow mask opening according to the prior art and according to the inventive teaching;

FIG. 4 is a fragmentary sectional view on an enlarged scale of the encircled portion in FIG. 1;

FIG. 5 is a fragmentary view of a portion of FIG. 4 but with the parts thereof in a different operative condition; 7

FIG. 6 is a sectional view taken along the line 6-6 of FIG. 4;

FIG. 7 is a fragmentary sectional view of a modified form of the invention; and

FIG. 8 is a sectional view taken along the line 8-8 of FIG. 7.

In the illustration given, the numeral 10 designates generally the face plate of a rectangular color television tube. The view in FIG. 1 is looking forwardly from the interior so as to see the face plate lipthis constituting the portion ultimately fused to the funnel portion of the tube to provide the overall glass envelope of the tube. The inside of the face plate is equipped with the usual phosphor dot screen as at 10b (see FIG. 2) and mounted inwardly of the screen is a shadow mask generally designated 11, conventionally employed with a screen having triads of dots in green, red and blue. The shadow mask 11 includes a perimetric frame about a perforated, curved face. It is the means for supporting this mask with which the instant invention is concerned. For this purpose, I depart from the usual posts and spring clips and employ instead, connection means which are responsive t the change in mask size (i.e., dimension) to move the mask axially to compensate for the size change.

OPERATION GENERALLY Reference is made now to FIG. 2 wherein the shadow mask 11 is seen in relatively heavy line and in the position when the tube is not in operation or under any kind of stress tending to change the size of the shadow mask 11. In the condition of the mask designated 11 in FIG. 2, it will be seen that an electron beam 12 passes through a given opening 13 in the mask 11. As the mask changes in sizeusually due to thermal expansion, the mask normally tends to expand laterally so as to position the opening 13 laterally outwardly of its original position. This is seen in FIG. 2 at 13 but relative to a chain line showing of the mask as at 11. It will be appreciated that with the ordinary installation, the mask 11 is not permitted to move axially so that the movement of the opening 13 is substantially only laterally, the relatively lighter chain line showing of the mask designated 11' in FIG. 2 not corresponding to actual operation but being exaggerated in order to more graphically illustrate the operation of the invention.

According to the invention, however, the movement of the opening 13 under stress is not merely just laterally as designated by the position 13 but is additionally axial, i.e., to the position designated 13 relative to mask position 11" in FIG. 2. As seen in FIG. 3, the position of the opening designated 13" is along the line of the beam 12. This direction is designated 14 in contrast to the direction 15 of ordinary movement in an uncompensated mask. This means therefore, that a beam will necessarily fall on its intended dot as at 16 in FIG. 2. rather than on an unintended dot or different portion of the screen as at 16'.

It will be appreciated that the absolute movements involved are rather small-of the order of .00 to .00 "but these are significant when it is considered that the mask openings are correspondingly small-300,000 openings 13 being provided in a shadow mask for a 23- inch tube.

By moving the mask axially of the tube 10 toward the screen 1012, I compensate for misregister of the openings 13 in a unique manner. The compensation is essentially a dilferential compensation-hence a true compensation. In the case where the mask 11 and the face plate 10 expand identically, there will be no axial movement since none is required. However, the usual case finds the metal mask (i.e., cold-rolled steel) expanding more than the glass face plate. The source of heat for the expansion is the electron beam 12 which first impinges on the mask (11, normally causing it to increase in temperature 30 C. or so. The tube 10 itself may increase in temperature only 10 C. or so. Alternatively, it will be appreciated that any change in size of the mask will result in the displacement when the size change is relative to the envelope and this may occur, for example, because of a pressure differential as well as because of a temperature differential.

According to the invention, there is provided a mask mounting which is responsive to size or geometric factors and which is independent of temperature. Although other devices have been advanced for remedying the problem to which this invention is directed, these devices have been temperature-dependent, i.e., involving the use of bimetals or the like. This has stemmed from the fact that those in the art have focused upon one of the significant factors which develop undesirable misregister. However, in compensating for temperature rise, they have been dealing with what might be considered a secondary phenomenon, as contrasted to the primary phenomenon the misregister due to change in size itself. There are instances where the ambient temperature has risen so that both the temperature of the glass envelope and the frame increase together. In such a case, providing a mounting device to shift the mask upon just its increase 'in tempera ture leads to an improper compensation. To provide the movement of the mask, I employ a mask-envelope connection as seen in FIG. 4, as described below.

MOUNTING CONSTRUCTIQN Referring now to FIG. 4, it will be seen that the envelope 10 carries a mounting post 17, a plurality of the posts 17 being provided as can be appreciated from a consideration of FIG. 1. The mounting post 17 projects inwardly of the envelope 1!) and is engaged by a fitting generally designated 18 which in turn is rigidly secured (as by welding) to the mask 11. The fitting 18 includes a spring portion 19 which engages a projection 20 provided on the post 17. The projection 20, in the portion thereof engaged by the spring portion 19, is V-shaped as can be appreciated from a consideration of FIG. 6.

The projection 20 is also equipped with a notch or a recess as at 21 which is engaged by a bracket portion 22 provided on the fitting 18. The bracket portion 22 is relatively flexible, being weldably secured as at 23 to the spring portion 19 and equipped with stiffener ribs 24 so as to confine any deformation to the area designated 25 in FIG. 4. As the mask 11 increases in size, the bracket 22 assumes a different angular configuration in the portion designated 25" (see FIG. so as to reduce the dimension x, of FIG. 4 to the dimension x in FIG. 5 while in creasing the dimension y to that designated y in FIG. 5. This moves the mask axially-to the position 11" of FIG. 5. In doing this, the bracket 22 has the leg portion equipped with the ribs 24 pivot about the leg portion secured as at 23 (see FIG. 4) so as to decrease the angle included between these leg portions.

An alternative construction can be seen in FIGS. 7 and 8 wherein the post is designated 117, being embedded partially in the envelope 110 for the purpose of moveably supporting the mask 111. Each post has a projection 120 corresponding to the showing in FIG. 4 for engagement by means of a fitting generally designated 118. Again, the fitting 118 is equipped with the spring portion as at 119. The bracket portion 122, instead of engaging a notch as in FIG. 4 is seen to bear upon an inclined plane portion 121. For this purpose, the bracket portion 122 may be equipped with a beveled contacting edge as seen in FIG. 7.

In the practice of this embodiment of the invention, the mask 111 is snapped into place, making use of the spring clip portion 119 which engages one side of the post portion 120, the other side 121 of a given post 117 being engaged by the laterally-extending projection 122. Upon differential expansion of the mask 111 relative to the envelope 110, the entire mask moves by virtue of the 4 engagement of the

parts

122 and 121 so that when the mask expands, the mask slides along the inclined plane to move axially toward the screen of the face plate 10.

While in the foregoing specification I have described the invention in detail, it will be appreciated that many variations may be made in the details of the invention without departing from the spirit and scope of the invention.

We claim:

1. In a color television tube having :a faceplate panel with an array of phosphor dots to provide an image screen and an apertured shadow mask adjacent said screen for admitting the passage of electron beams for the selective excitation of said dots, an improved mounting system for mounting said mask to said tube for shifting the mask toward said screen axially of said tube when said mask is heated as a function of the differential expansion of said mask relative to said faceplate panel comprising a plurality of posts projecting inwardly of said tube for receiving said mask, each post defining a projection having a transverse V-shaped surface facing away from said screen and a limiting surface facing said screen, and a plurality of fittings on said shadow mask, one for each of said posts, and including a hook-shaped spring member extending outwardly and rearwardly of said mask and defining a. groove for engaging said V-shaped surface of an associated post thereby to bias said mask in a rearward position relative to said screen, and a deformable bracket member having a first portion secured to said mask and a second portion angularly inclined at a bend line relative to said first portion and having a distal edge received in the limiting groove of said associated post whereby when said mask expands due to heating said deformable bracket will bend about said line to shift said mask forward and into registration and said mask upon cooling will revert to its original position under action of said spring member.

2. The mounting system of claim 1 wherein each of said second portions of said deformable bracket members is ribbed to provide a stiffening thereof to prevent deformation of said second portion during heating.

References Cited UNITED STATES PATENTS 2,727,172 12/1955 Mark ct a1. 2,795,718 6/1957 Van Hekken et al. 2,795,719 6/ 1957 Morrell. 3,370,194 2/ 1968 Schwart et a1.

ROBERT SEGAL, Primary Examiner US. Cl. X.R. 3 13-286, 292