US2922063A - Target assembly for cathode ray tubes - Google Patents

Description

Jan. 19, 1960 s 2,922,063

I TARGET ASSEMBLY FOR CATHODE RAY TUBES Filed Nov. 7, 1956 2 Sheets-Sheet 1 INVENTOR PQ UL HAAS WM ATTORNEY Jan. 19, 1960 P. HAAS 2,922,063v

TARGET ASSEMBLY FOR CATHODE RAY TUBES Filed Nov. 7, 195a 2 Sheets-Sheet 2 AXIAL ROTATIONAL RADIAL INVENTOR PBeU L HAAS ATTORNEY nited States Patent TARGET ASSEMBLY FOR CATHODE RAY TUBES Paul Haas, Seneca Falls, N.Y., assignor, by mesne assignments, to Sylvania Electric Products Inc, Wilmington, Del., a corporation of Delaware Application November 7, 1956, Serial No. 620,839

3 Claims. (Cl. 31385) This invention relates to cathode ray tubes and more particularly to a target assembly for such tubes.

A cathode ray tube of the type employed in color television apparatus generally has a screen comprising a large number of blue, green and red phosphor bars, stripes or dots arranged in a prescribed manner on the glass face plate of the tube. A grid or mask is usually mounted adjacent the screen so that the modulated scanning electron beam or beams utilized in the tube will be deflected or masked by the grid so as to strike the appropriate phosphor configuration.

When the above described screen is formed by the commonly used photographic printing technique, as well as by other techniques, it is important that the grid to screen distance in the target assembly be the same in the finished tube as it was in the screen forming operation, since any deviation in this distance will alter the screen area energized by a given electron beam and will thereby cause an impure color image to be reproduced. One of the major problems involved in maintaining the grid to screen distance arises from the expansion and contraction characteristics of the grid when it is heated during tube processing. Therefore, it is desirable to have a grid support structure which will allow the grid to be flexibly held in position. This support must also be rugged so that the grid cannot be dislodged from its position during handling and-installation in the television receiver.

One proposed support structure for a cathode ray tube grid comprises curved springs held in appropriate grooves formed in the tube envelop. The grid is mounted on a frame, which is welded to the springs. A support of this type requires a heavy grid frame to withstand the force exerted by the springs, since the grid mesh itself is very flimsy. This heavy frame in turn necessitates use of heavy springs so that the grid will be properly supported and will not be dislodged during handling. It is apparent that the dependency of the size and strength of the springs and frame leads to the adoption of unwieldy and expensive structures. In addition, it is diificult and expensive to fabricate a tube envelop with appropriate grooves or support means for mounting the springs.

Accordingly, an object of the invention is the provision of a target assembly for a cathode ray tube wherein impure color reproduction characteristics, attributable to shifting or warping of the target elements are reduced.

A further object is the provision of an aperture mask or rid structure which is adapted to expand and contract with temperature variations without warping.

A still further object is the provision of means for supporting the aperture mask or grid relative to the screen of the tube to allow radial movement of the grid while substantially preventing axial and rotational movement.

The foregoing objects are achieved in one aspect of the invention by the provision of a target assembly employing a face panel which has mounted thereon support 2,922.,Q53 Patented Jan. 19, 1960 members fabricated as resilient metal strips. These members are affixed to the frame of the grid to effect flexible suspension of the grid from the screen surface of thetube. The support members provide substantially rigid positioning for the grid in the axial and rotative directions, while allowing radial movement.

For a better understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a cross sectional view of a typical cathode ray tube of the type used in color television apparatus;

Fig. 2 is a plan view of a target assembly adapted for use in a cathode ray tube;

Fig. 3 is a view of Fig. 2 taken along line 3-3;

Fig. 4 is a partial perspective View showing a support member for the grid employed in the target assembly;

Fig. 5 shows another support member in perspective;

Fig. 6 illustrates the forces exerted on the grid under various circumstances;

Fig. 7 is a sectional view of the support member shown in Fig. 5;

Fig. 8 illustrates a spring of the type shown in Fig. 5; and

Fig. 9 shows a pin adapted spring illustrated in Fig. 8.

Referring to Fig. 1, a cathode ray tube 11 of the type adapted to be used in color television apparatus is shown comprising a target assembly 13 and an envelop 15 terminating in an electrical connector base 17. Contact pins 19 are arranged on base 17 to electrically interconnect the electrodes of an electron gun assembly 21 with its appropriate receiver circuitry.

Target assembly 13 comprises a glass face panel 23 which is formed with a peripheral wall portion 25. A11 aperture mask or grid 27 is held in position relative to the face panel by means of support member 29 which are in turn mounted upon tabs 31. These tabs are welded to flange 39 located on wall portion 25 to complete the grid suspension structure.

During operation of the tube, the electron beam or beams 33 emitted from gun assembly 21 pass through the apertures in grid 27 and impinge upon the phosphor screen material 35 to provide reproduction of the image. It is apparent that it is necessary to accurately maintain the distance between grid 27 and screen 35 at all times after the screen has been formed, since the beams, when deflected by coils 37, must pass through the openings in the grid at the correct distance from the deflection position in order to strike the correct phosphor configuration.

Tube 11 is usually processed to remove gases after target assembly 13 is sealed to envelop 15 by means of a glass solder or weld connection between oppositely disposed flanges 39. During this exhausting operation, the tube is heated above 400 C., which temperature is high enough to cause grid 27 to expand radially. Support members 29 are constructed to allow this expansion while still maintaining the grid substantially rigid in other directions.

A more detailed description of one means of supporting mask 27 relative to screen 35 may be obtained with reference to Figs. 2 through 4 inclusive. Four support members 40 are shown attached to tabs 41, which are in turn welded or otherwise affixed to flange 39. Support members 40 are arranged apart around the periphery of face panel 23 so that grid 27 is properly suspended and spaced from screen 35. This arrangement of the support members provides a substantially rigid mounting for the grid in its axial and rotative directions. Although four support members are shown, it is to be understood that more than four such memto cooperate with the bers may be employed. Also three equally spaced members may provide satisfactory support.

Fig. 4 shows more clearly the configuration of support' is exerted upon it. The long leg of the L-shaped bracket 40 provides a thin fiat-faced resilient member upo which grid 27 is suspended.

Figs. 5 and 7 show another embodiment of the support member adapted to be employed in a cathode ray tube. This support member or bracket 49 is a substantially triangular shaped flat-faced resilient metal strip with one leg of the triangle being welded to the frame 51 of mask or grid 27, which is shown in this instance as a perforated metallic sheet. An aperture is formed in the bracket to provide cooperation with the suspension device or pin 53 mounted in wall portion 25. Bracket 49 is held on the pin by means of spring 55. It can be seen in Fig; 8 that the spring is folded over to provide opposed faces between which bracket 49 may be positioned and held. One face of the spring has a slot 57 with an aperture 59 formed intermediate the slot ends. The opposed spring face is bent inwardly toward aperture 59, and is provided with an aperture 61. Referring to Fig. 9, pin 53 comprises a barrel portion 63, which is sealed into wall 25, connected to a frustoconical portion 65 by a recess portion 67. The taper of portion 65 is outwardly toward recess 67. During assembly ofgrid 27 upon face panel 23, bracket 49 is first placed upon pins 53.- The slot 57 of A grid for a cathode ray tube fabricated and suspended in the manner illustrated herein may be accurately and efiiciently mounted in a target assembly. The grid may expand or contract without becoming mis-formed, while still remaining substantially rigidly aflixed to the face panel to protect against displacement or dislodgement during handling;

Although several embodiments of the invention have been shown and described, it will be apparent 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: V

1. A target assembly for a cathode ray tube comprising a face panel having a face plate and a peripheral wall portion, suspension devices attached to said wall portion spaced from said face plate, a'fragile grid structure disposed intermediate said plate and the suspension devices, and a pluralityof support brackets including a thin flat resilientstrip connected at one end to said suspension devices'and at the opposed end to said grid, the brackets extending from said suspension devices toward said face plate along a plane spaced from the peripheral wall portion to eifect a free suspension of the grid on said brackets, said brackets being spaced from one another and positioned to allow flexing substantially perpendicular to said flat strip during :radial expansion of said grid and to substantially prevent movement of said grid rotatively and axially.

2. -A target assembly for a, cathode ray tube comprising a'face panel having a face plate and a peripheral wall portion, at least three suspension devices attached to said wall portion spaced from said face plate, a fragile grid structure disposed intermediate said plate and the suspenspring 55 is then slid down over recess 67 until the w walls of aperture 59 contact the recess. The opposed face of the spring is then allowed to move toward the pin so that pin portion 65 protrudes through aperture 61. The walls of this aperture contact the surface of the tapered pin portion and thereby lock bracket 49 in position; a

To better understand the action of the'support me'nithe periphery of face panel 23, and due to the rigid aflixation of mask frames 47 and 51 to thesev support members, no substantial rotational movement of the grid is possible.

'As previously explained, the grid of a cathoderay tube must be allowed to expand and contract radially so that the metal will not warp when subjected to heat; It is believed that a grid ,of this type does not substantially expand or contract at its center, but that, for all practical purposes, it moves only radially. Brackets and 49 are therefore constructed to flex in the directibnof radial movement of the grid. The action of brackets 40 and 49 may be likened to a hinge action. When the grid 27 expands, the hinges allow it to move out radially, and when they contract, the hinges allow a movement radially inward. It is to be noted however, that the grid is not allowed substantial movement in any other direction.

Also, dueto'the arrangement of the support members 40 and 49 around sion1devices,-and an L-shaped support bracket including a thin flat resilient strip connected at one end to each of said suspension devices and at the opposed end to said grid, the brackets extending from said suspension devices toward said face plate along a plane spaced from the peripheral wall portion to effect a free suspension of the grid on said brackets, said brackets being spaced from one another and positioned to allow flexing substantially perpendicular to said flat strip during radial expansion of said grid and tosubstantially prevent movement of said grid rotatively and axially. i

3. A target assembly for a cathode ray tube comprising a face panel having a face plate anda peripheral wall portion, at least three suspension pins attached to said wall portion spaced from. said face plate, a spring associated with each pin, a fragile grid structure disposed intermediate said plate and the suspension pins, and a plurality'of support brackets including a thin flat resilient strip connected by said springs atone end to said suspension pins and at the opposed end to said grid, the brackets extending from said suspension pins toward said face plate along a planespaced from the peripheral wall portionto effect a free suspension'of the grid on said brackets, said brackets being spaced from one another and posi- A tioned to allow flexing substantially perpendicular to said fiat stn'p during radial expansion of said grid and to v substantially prevent movement of said grid rotatively and axially; I

--Refer'enc'es Cited in the file of this patent p UNITED STATES PATENTS 2,727,172 Mark Dec. 13, 1955 2,733,366 Grimm Ian. 31, 1956 2,795,718 j Van Hekken June 11, 1957 2,795,719 Morrell June 11, 1957 2,823,328 Vincent Feb. 11, 1958 2,846,608 Shrader Aug. 5, 1958

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