US3501663A

US3501663A - Parallax barrier protecting means for cathode ray tubes having patterned screens

Info

Publication number: US3501663A
Application number: US751970A
Authority: US
Inventors: Glen A Burdick
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1968-08-12
Filing date: 1968-08-12
Publication date: 1970-03-17
Anticipated expiration: 1987-03-17
Also published as: GB1223779A

Description

March 17, 1970 G. A. BURDICK 3,501,663

PARALLAX BARRIER PROTECTING MEANS FOR CATHODE RAY TUBES HAVING PATTERNED SCREENS Filed Aug. 12, 1968 INVENTOR. GLEN A. BURDIGM ATTORNEY United States Patent US. Cl. 313-85 4 Claims AESTRACT OF THE DISCLOSURE Support-springs for color cathode ray tube parallax barriers have an outwardly projecting portion formed thereon to extend from the apertured free end of the spring to prevent damaging contact of the barrier with an inwardly extending supporting stud formed on the interior wall of the cathode ray tube face plate during the insertion of the barrier within the face plate.

Background of the invention This invention relates to cathode ray tubes having a patterned cathodoluminescent screen with a parallax barrier positioned between the screen and a source of electrons and more particularly to a color cathode ray tube of the shadow mask variety wherein the mask is releasably mounted within the face plate of the tube by means of leaf springs having one end connected in supportive relation to the mask and an apertured free end formed to engage an inwardly extending stud formed on a wall of the face plate. Still more particularly the invention relates to means associated with the support springs for protecting the mask from damaging contact with the studs during insertion thereof into the face plate. Color cathode ray tubes of the type in use today have patterned cathodoluminescent screens comprised of discrete areas of phosphors that emit different colored light upon excitation by a cathode ray. The particular phosphor or phosphors selected for excitation is controlled by a particular electron beam or beams and the parallax barrier as is well known in the art.

The patterned screens for this type color tube are prepared by a photographic deposition technique wherein, by one of several known methods, a layer of phosphor and a photosensitized material is applied to the screen area which is then exposed, by a point source of light passing through a patterned negative, to cause the exposed areas to become fixed in relation to the unexposed areas. The negative is then removed and the screen developed to form part of the final pattern. The process is repeated for each of the different color light emittin phosphors desired in the finished tube.

In tubes of the shadow mask variety, the parallax barrier (or shadow mask) is composed of a fragile foraminous metal sheet having a thickness of the order of .006 inch. This shadow mask is formed to be substantially parallel to the screen surface (generally spherical in modern tubes) and is fixed at its periphery to a frame having substantially rigidity relative to the mask. The frame may be composed of a metallic material having a thickness of the order of .050 inch. This shadow maskframe assembly is supported within the face plate of tube and in spaced relation to the screen by means of leaf springs attached at one end to the frame and having apertured free ends extending therefrom. The apertured free ends are formed to cooperate in supporting relationship with inwardly projecting studs formed on interior walls of the tube face plate. It is necessary that the mask be releasably mounted in the face plate because it is utilized as the negative in the screen formation process. Thus, during the formation of the screen the mask must be inserted and removed a minimum of three times. It 15 during insertion that damage to the mask is most likely to occur. If an operator inserting the mask is careless or if the mask is not properly centered in the face plate, damaging contact of the mask with one or more of the mwardly projecting studs may occur. Because of the fragile nature of the mask such contact need only be slight to cause a dent in the mask. Such a dent formed m the maskwhich, it is to be remembered, is used as the negative in the screen formation process-will cause an imperfect screen to be formed and result in the rejection of the finished tube.

Objects and summary of the invention It is an object of this invention to enhance the fabrication of color cathode ray tubes.

It is another object of this invention to reduce the scrap or shrinkage in color cathode ray tube production and thus reduce the cost.

It is yet another object of the invention to improve the screen quality of color cathode ray tubes.

Yet another object of the invention is to increase the facility with which an unskilled operator may insert parallax barriers in the face plates of color cathode ray tubes without causing damage thereto.

These and other objects are accomplished in one aspect of the invention by the provision on at least two of the support springs of means for protecting the parallax barrier from damaging contact with the inwardly projecting studs during its insertion into the face plate.

Brief description of the drawings FIG. 1 is a sectional view of a color cathode ray tube employing the invention;

FIG. 2 is a perspective view of one type of support spring utilizing the invention; and

FIG. 3 is an alternate embodiment of the invention.

Description of the preferred embodiments For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above-described drawings.

Referring now to the drawings with greater particularity, in FIG. 1 there is shown a typical color cathode ray tube 10 of the shadow mask variety which comprises an envelope formed from a substantially funnel-shaped body 12, an elongated neck 14 closing the small end of the funnel, and a face plate 16 having an upstanding peripheral wall 17 therearound closing the large end of the funnel. A patterned cathodoluminescent screen 18 is formed on the inside surface of face plate 16 and a source of electrons in the form of one or more electron guns 20 is positioned in neck 14. Positioned intermediate guns 20 and screen 18, but closer to screen 18, is a parallax barrier 22. In this instance parallax barrier 22 is shown as a shadow mask; and will hereafter be referred to as such; however, it is to be understood that other types of bar riers may be utilized, such, for example, as switching grids, aperture grills, focus masks, etc. The shadow mask 22 is a thin, fragile, foraminous member having a thickness of the oder of .006 inch. A small upstanding wall 24 projects from the periphery of the mask and is attached to a relatively rigid supporting frame 26. The frame 26 is in turn mounted within the face plate 16 by means of a plurality of support springs 28 which are mounted in a supporting relation at one end thereof to a wall frame 26 and at their free end to inwardly projecting studs 30 formed in spaced relation around wall 17 of face plate 16. Studs 30 are substantially frustoconical in configuration and mate conjnnctively with appropriately formed apertures 32 in the free end 34 of springs 28.

Spring 28 is shown detail *in FIG. 2 as comprising a first portion 36 and a second portion 34, previously men tioned as the free end, which are substantially parallel.

The first and second portions are interconnected by an intermediate section 38. Means 40 for protecting mask 22 from damage during, insertion into face plate 16 comprises a projecting portion 42 extending from; the apertured end 34 of spring 28 toward mask 22. The distal end 44 may be formed to project inwardly toward the center of the tube. Thus it will be seen that during insertion of the mask-frame assembly into face plate 16, if the mask is off-center, it is the distal portionAZ of mask protecting means 40 which will contact the inwardly projecting stud 30. Obviously, mask protecting means 40 must not project toward mask 22 a;distance great enough to interiere with.;the screen forming process.

In FIG. 3 is shown an alternate embodiment of the spring 28 wherein the mask protecting means 40 has formed therein stud lead-in means 44 which may; be in the form of a groove extending from substantially the aperture 32 to the terminus of distal end 42. Additionally, when spring 28 is so provided, the groove may have a widened entrance area 46 to facilitate the entrance of stud 30 thereinto.

Thus, by this invention, the fabrication of color cathode ray tubes has been greatly enhanced. Means have been provided which reduce shrinkage in tube manufacture and subsequent cost thereof. Further, the facility with which an unskilled operator may insert parallax barriers within the face plates of tubes, without damage thereto, has been increased.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made 4 therein without departing from the scope of the invention as defined by the appended claims.

I claim:

1. In a cathode ray tube having a parallax barrier releasably mounted therein between a patterned 'cathodoluminescent screen and a source of electrons, means for mounting said barrier in said tube comprising at least two inwardly projecting studs formed around a wall of the tube and a like number of support springs formed to support said barrier and being further formed to provide at the free end thereof an aperture to receive said inwardly projecting studs, the improvement comprising:

means integral with said at least two of said support springs for protecting said parallax. barrier from damaging contact withzsaid inwardly projecting studs during its insertion into said tube.

2. The invention of claim 1 wherein said means for preventing damaging mask contact with said studs comprises a projecting portion extending from the apertured free end of said spring toward said barrier and having. its distal end formed to project inwardly toward the center of said tube. I

3. The invention of claim 2 wherein said distal end is spaced from said barrier.

4. The invention of claim 1 wherein said barrier is aflixed at substantially its periphery to a supporting frame having upstanding walls and said support springs are affixed to said walls and said free end is spaced there from.

References Cited UNITED STATES PATENTS 12/1955 Mark et al 313 8/1958 Shrader 3l385