US2915953A - Cathode ray tube apparatus - Google Patents

Description

1959 H. E. SMITHGALL 2,915,953

CATHODE RAY TUBE APPARATUS Filed Nov. 16, 1955 INVENTOR HARRY E. SMITHGALL BY 7704mm .6

ATTORNEY United States Patent Office 2,915,953 Patented Dec. 8, 1959 CATHODE RAY TUBE APPARATUS Harry E. Smithgall, Seneca Falls, N.Y., assignor, by mesne assignments, to Sylvania Electric Products Inc., Wilmington, Del., a corporation of Delaware Application November 16, 1955, Serial No. 547,246

3 Claims. (Cl. 95-1) This invention relates to a support structure and more particularly to a structure for supporting and positioning a source of radiant energy with respect to a printing mask of the type employed in the manufacture of tri-color television picture tubes.

In the processing of tri-color picture tubes, a pattern of blue, green, and red fluorescent phosphor dots or strips are conventionally formed on the inside surface of the picture tube face plate by means of photo-printing techniques. In accordance with one preferred technique, a first phosphor, which may be blue fluorescent phosphor material, is combined with a photosensitive substance to form a layer of material which is deposited on the face plate of the tube. This layer is subjected to light rays for a pre-determined period of time through a negative which may be the shadow mask employed in one type of a tri-color picture tube. Those areas of the phosphor and photosensitive composition layer which have been subjected to light become hardened and adhere to the face plate of the tube. A subsequent developing operation utilizing a washing step wherein the layer is rinsed with a suitable developing fluid completes formation of the blue phosphor pattern. This process is then repeated for the green and red fluorescent phosphors to complete the tri-color screen. The light source is indexed to a predetermined position for each of the dot forming operations in accordance with the electron excitation areas on the screen as determined by the three cathode emitters employed in the tube.

Light source supporting and positioning devices employed in this photo-printing technique usually comprise a stationary box having a point source of light positioned within an aperture provided in one surface of the box and a plurality of pedestals attached to the same surface and arranged along the periphery of a circle Whose center is the light source. During the phosphor pattern forming operation, the negative or aperture mask and face plate assembly is placed upon the pedestals so that the mask is intermediate the point source of light and the picture tube face plate. The height and position of the pedestals, along with cooperating elements mounted upon the mask, afford the correct spacing and alignment necessary for proper location of the phosphor dots. This mask and face plate assembly must be placed upon and removed from the light source housing pedestals at least once for each of the three phosphor dot forming operations.

The above described light source housing is not readily adaptable for automatic production of color television picture tubes because of its size and stationary mounting. The repetitious positioning and removal of the screen and aperture mask assemblies is time consuming and requires substantial attention and manipulation.

It is therefore an object of the invention to reduce the aforementioned disadvantages and to provide a picture tube processing frame which may be effectively used with automatic production methods and apparatus.

A further object is the provision of a viewing panel processing device frame which is portable and adaptable for efficient and accurate positioning of the device with respect to the viewing panel.

The foregoing objects are achieved in one aspect of the invention by the provision of a portable housing frame having a screen processing device mounted upon one portion thereof and a plurality of pins oppositely disposed therefrom for positioning the device relative to the viewing panel of the tube. This device can be readily placed upon a moving conveyor carried picture tube face plate structure so that the light exposure operation may be performed on a production line basis.

For a better understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawing which shows in perspective one embodiment of the invention partially cut away to illustrate the cooperating elements of the structure and the manner in which it is adapted to be positioned with respect to the color picture tube face plate and the negative mask structure.

Referring to the drawing, a housing frame 11, supporting a light box 19, is shown in position above a photoprinting negative structure or aperture mask 13. A picture tube face plate structure 15 surrounds mask 13 and has a screen panel 17 which is disposed beneath the mask and opposite light box 19. These structures are arranged in accordance with their assembled positions during the exposure period of the photo-printing process. In this process, a layer of a first phosphor such as the blue phosphor, zinc sulfide, is deposited on screen panel 17 along with a photosensitive material such as polyvinyl alcohol sensitized with ammonium dichromate. Mask 13 is then positioned above screen panel 17 and the frame 11 is mounted in its appropriate position upon mask 13 and opposite screen panel 17. The layer of phosphor and photosensitive material deposited on the screen panel is then subjected to ultra violet light traveling from light box 19 through aperture mask 13. Those areas of the screen panel which have been exposed become hardened and adhere to the glass panel. The panel, mask and housing may be continuously moving along a conveyor during this operation. Housing frame 11 and aperture mask 13 are then removed from face plate structure 15, and panel 17 is washed with a suitable rinsing fluid such as deionized water to effectively develop the blue fluorescent phosphor pattern. The complete tri-color pattern is made by repeating the previous steps sequentially for the green fluorescent phosphor, zinc ortho silicate, and the red fluorescent phosphor, zinc phosphate. The tri-color pattern of phosphor dots is attained by indexing light box 19 so as to provide a pattern made in conformance with the excitation areas of the appropriate ones of the three cathode emitters employed in the tube. This result is attained by positioning the light source approximately .277 inch off center.

Frame 11 comprises a rotatable plate 21, a skirt portion 23, and integral lugs 39. Plate 21, shown supported upon the upper portion of skirt 23 is provided with three apertures disposed apart. These apertures cooperate with removable dowel pins 27, so that the pins may be disengaged after each phosphor dot forming operation to facilitate rotation of light box 19 to its subsequent operational position. Although three pins 27 are shown, a single pin may be used or any other means may be employed for sequentially rotating plate 21 over 120 and locking it in position after each rotation such as a spring loaded ball and cooperating socket combination.

Positioned on top of rotatable plate 21 is the light box 19 having mounted therein a light rod 29 and a light emitter 31. The light from this emitter travels down light rod 29 and emanates from the end thereof. A centering device 33 is mounted on the base of box 19 and surrounds light rod 29 so that the rod will be correctly positioned relative to plate 21. Cables 35 serve as the electrical connectors for emitter 31, and conduit 37 serves as a means for air-cooling the area within the box.

Skirt 23 is shown formed as a truncated cone type hoop having large elliptical perforations and stiffening ribs. Attached along the periphery of skirt 23 are a plurality of lugs 39 which are integral with skirt 23 and oppositely disposed from plate 21. The lugs extend from skirt 23 along a plane normal to the axis of the skirt. Arranged in the lugs are pins 41 which serve as positioning and locating means for housing 11 with respect to mask 13 and face plate structure 15. The three positioning pins 41 are disposed around skirt 23 so that two of them are spaced less than 120 apart, with the third pin being located in the lug which is equi-distant from the other two. This type of positioning provides an efficient and accurate means for attaining repetitious placement, since frame 11 will cooperate with mask 13 and face plate structure 15 in only one manner. Also disposed in lugs 39 are rods 43 which may have weights 45 mounted thereon. These rods, when used, serve to provide a multi-point pressure upon the mask assembly 13 during the phosphor pattern forming operation, thereby reducing the possibility of the thin perforated mask 13 becoming bent or warped. Weights 45 are mounted upon lugs 39 by means of nut 47. If desired, springs or other pressure devices may be used in place of the weights.

The ends of pins 41 have substantially V-shaped grooves formed therein for cooperation with clips 49 mounted upon mask 13. The clips, in turn, are positioned with respect to face plate 17 by means of integral glass nubbins 51. In some instances, the ends of pins 41 may have a semi-spherical shape so that they are formed to cooperate with an aperture mask and face plate assembly having a rim provided with indentations. The mask thereby has a three position support upon three nubbins arranged around the internal edge of face plate structure '15. Frame 11 also has a three point support by means of the cooperation between pins 41 and mask clips 49. In

addition, mask 13 rests upon a number of lands 53 which aid in maintaining the desired configuration of the mask. Weighted rods 43, when used, rest on the mask and therefore apply pressure at those points of the mask frame cooperating with face plate lands 53. If desired, mask 13 may have attached thereto more than three clips of the type designated at 49, and housing 11 may have as many positioning pins- 41 as is needed to effectively position and support the housing. In addition, mask material thickness, size of the mask assembly, and the number of perforations will determine the number of rods 43 and the size of weights or springs which may be used.

Although the support and positioning assembly illustrated has been described in conjunction with a photoprinting technique and applicable particularly to shadow or aperture mask type color picture tube, it is apparent that the structure constituting the embodiment shown is not limited to such a process nor such a type color pic- 'ture tube. For instance, it is applicable to any type of viewing panel processing technique wherein the processing device must be aligned and spaced from the viewing panel during processing.

Although housing frame 11 has been shown with a rotatable plate 21, It may be advantageous to utilize three such frames, each with a light box 19 permanently affixed in one of the three operational positions. In production, this frame would then be used continuouly for only the appropriate one of the three phosphor exposure operations.

A light mounting and positioning frame made in accordance with this invention provides a structure which is light weight and portable. It is adaptable for automatic production and is capable of being eificiently employed and accurately positioned during the process of forming color television picture tubes.

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

What is claimed is:

1. A portable device for processing screens employed in cathode ray tube screen assemblies comprising a radiant energy source, and a frame formed to position said radiant energy source above the screen, said frame having a base, means attached to said frame for supporting said radiant energy source, and a plurality of spaced locating devices depending from said base and oppositely disposed from said supporting means, said locating devices having a given configuration formed to removably engage complementary structures on the screen assembly and align said radiant energy source relative to the screen, the peripheral distance between two of said locating devices being less than the peripheral distance between others of said devices.

2. A portable device for processing screens employed in cathode ray tube screen assemblies comprising a radiant energy source, and a frame formed to position said radiant energy source above the screen, said frame having a base, a plate rotatably mounted upon said frame formed to support said radiant energy source, and a plurality of spaced locating pins depending from said base and oppositely disposed from said plate, said locating pins having a given configuration formed to removably engage complementary structures on the screen assembly and align said radiant energy source relative to the screen, the peripheral distance betwen two of said locating pins being less than the peripheral distance between others of said pins.

3. A portable device for processing screens employed in cathode ray tube screen assemblies employing a mask comprising a radiant energy source, and a frame formed to position said radiant energy source above the screen,

'said frame having a skirt portion, a plate rotatably mounted upon said skirt portion formed to support said radiant energy source, a plurality of integral lugs arranged peripherally around said skirt portion and oppositely disposed from said plate, three positioning pins disposed in three of said lugs formed with substantially V- shaped grooves to contact complementary structures on said screen assembly, two of said pins being mounted less than apart, and weighted rods mounted in others of said lugs formed to contact the mask.

References Cited in the file of this patent UNITED STATES PATENTS

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