JPS6310857B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of processing a final electrode of an in-line electron gun forming a main lens used in a color cathode ray tube.

The electrode section of a conventional in-line electron gun has a structure as shown in FIG. That is, a flat cathode holder 1 holds three cathodes 2 arranged in parallel, and the cathodes 2 are heated by a heater 3 inserted in the cathodes 2 and emit an electron beam. . Further, at the tip of the cathode 2, a first grid 4 for controlling the electron beam, a second grid 5 for accelerating the electron beam, and third and fourth grids 6 and 7 constituting the main lens electrode are connected in series. The electron beams are provided and fixed to the bead glass 8, and each of these grids allows the electron beam to strike a predetermined phosphor stripe.

The fourth grid 7, which serves as the final electrode, has three circular hole-shaped lens parts 7a, 7b, and 7c arranged in close proximity to each other, and a cylindrical auxiliary electrode 9 is coaxially connected to these lens parts. It is permanently installed. This auxiliary electrode 9 is provided so that the electric field formed within the fourth grid 7 is not affected by the side wall of the fourth grid 7, and originally the lens portions 7a to 7
This is not necessary if the cylindrical portion c is formed long.

Therefore, conventional attempts have been made to manufacture the final electrode by integrally molding a lens portion having a long cylindrical portion. This method is illustrated in FIG. That is,
As shown in Figure A, a flat material plate 10 is subjected to an overhang process, and then, as shown in Figure B, a burring pilot hole 11 is formed by punching at the top of the overhang part, and then as shown in Figure C. A lens portion 1 having a cylindrical portion 12 subjected to burring processing as shown in FIG.
3 is formed. However, when the pitch of the lens portion 13 is p and the inner diameter is d, the final electrode satisfies p≦
The relationship is 1.5d. However, when integrally molding lens parts that are very close together using the conventional method, the height h of the cylindrical part must be approximately h≦1/3d relative to the inner diameter d, considering the elongation of the material. This is the limit. Therefore, in order to further increase the height h of the cylindrical portion, it is necessary to simultaneously perform so-called ironing, which is a processing method in which the gap between the punch and the die is made smaller than the material plate thickness during the overhang processing. However, in this case, the material of the U-shaped portion 14 formed at the base of the two adjacent cylindrical portions 12 is drawn in with the action of the punch, and the plate thickness is locally reduced, so the flatness of the opening periphery 15 is reduced. It will lower it. When such a phenomenon occurs, the circularity of the electron beam is lost, resulting in a fatal defect in the lens electrode, making it impossible to put it to practical use. Therefore, conventionally, an auxiliary electrode 9 is used as shown in FIG. Similar considerations apply to the third grid.

In addition, _as shown in FIG.
Equal distance between each hole through which 5 and 6 electron beams pass
It is somewhat larger than _S2 , and the hole diameter of the electron beam passage hole is also larger than the hole diameter of the third grid 6. In order to focus the three electron beams on a point on the fluorescent surface, two of the third and fourth grids 6 and 7 are used.
However, the degree of focusing largely depends on the flatness of the opposing surfaces of the electrodes, and if the flatness described above cannot be achieved accurately, the focus characteristics of a color cathode ray tube may be affected. This is a fatal flaw that causes deterioration.

The present invention has been made in view of the drawbacks of the prior art described above, and is designed to provide three electrodes in close proximity to each other so as to sufficiently satisfy the electrode function.
An object of the present invention is to provide a method for processing an electrode for an electron gun, which allows a lens part having a sufficient height of cylindrical parts to be integrally molded with high precision.

Hereinafter, the present invention will be explained with reference to illustrated embodiments.

FIG. 3 is a process explanatory diagram showing an embodiment of the method for processing an electrode for an electron gun according to the present invention. First, as shown in FIG. 2A, a stretching process 21 involving ironing is performed on the material plate 20 at locations corresponding to the two outer electron beam passage holes, thereby forming two outer projecting cylindrical portions 22. This stretching process 21 that involves ironing is performed in multiple steps while keeping the inner diameter of the die constant and gradually increasing the outer diameter of the punch, that is, gradually reducing the gap between the die and the punch.
As a result, the overhang thickness gradually becomes thinner and the height increases. Next, as shown in FIG. 1B, an overhanging process 23 involving ironing is performed at a location corresponding to the central electron beam passage hole in the same manner as in FIG. Next, as shown in FIG.
form 6. Subsequently, as shown in FIG.
Lens portions 29a, 29b, and 29c having 8c are formed. Finally, as shown in E, when the irregularly shaped cup drawn part 30 is formed, the irregularly shaped cup drawn part 31
is obtained.

In this way, during the overhanging process that involves straining, two separate outer overhanging cylindrical parts 22 are first formed, so that the plate thickness does not locally decrease due to this process. After forming the outer overhanging cylindrical portion 22 in this way, the central overhanging cylindrical portion 24 is formed next, so when the central overhanging cylindrical portion 24 is stretched out by ironing, the outer overhanging cylindrical portion 22 is Therefore, the material is not drawn in and the plate thickness is not locally reduced. Therefore, it is possible to suppress the decrease in the plate thickness of the bases of the adjacent cylindrical parts 28a, 28b, 28c, and to maintain a sufficient height of the cylindrical parts 28a, 28b, 2 without impairing the flatness around the opening.
Lens parts 29a, 29b, 29c having 8c are obtained.

Here, the height and inner diameter of the central cylindrical portion 28b are respectively Hc and Dc, and the outer cylindrical portion 28b is
The heights of a and 28c and their inner diameters are respectively Hs,
If Ds, Hc/Dc≧0.5, Hs/Ds≧0.5, Hc≦Hs, Dc at the same time by the method of the present invention described above.
An integrally molded electrode that satisfies <Ds can be obtained.

Here, the height of the outer cylindrical parts 28a, 28c
Hs may be the same as the height Hc of the central cylindrical portion 28b, but in the present invention, as described above, the outer extending cylindrical portion 22 is first subjected to the elongating process accompanied by ironing, so that the outer cylindrical portions 28a and 28c are The height Hs can be formed higher than the height Hc of the central cylindrical portion 28b. In this way, the outer cylindrical portion 28a,
If the height Hs of the third grid 28c is made high, there are disadvantages that arise because the outer cylindrical parts 28a and 28c are eccentric with respect to the center of the side circular hole of the opposing third grid.
That is, it is possible to prevent the aberration of the electrostatic lens from increasing. As a result, the focus characteristic of the electron beam passing through the side circular holes is improved to the same extent as that of the electron beam passing through the central circular hole.

In the above embodiments, a bipotential electron gun has been described, but the present invention can be similarly applied to the final electrode of a unipotential electron gun. Further, before the process shown in FIG. 3A, pilot holes for overhanging processing may be formed in advance at the centers of the two outer electron beam passage holes and the center electron beam passage hole. If the pilot hole for overhanging is formed in advance in this way, the overhanging process that involves ironing in the next step becomes easier.

As is clear from the above explanation, according to the method of processing an electrode for an electron gun according to the present invention, the lens part having three cylindrical parts of sufficient height in close proximity to each other so as to sufficiently satisfy the electrode function can be fabricated with high precision. It is possible to obtain a color cathode ray tube which can be integrally molded into a color cathode ray tube and which has good focus characteristics and resolution.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway side view of a conventional in-line electron gun, Fig. 2 a, b, and c are explanatory diagrams showing the process order of the final electrode processing method of a conventional in-line electron gun, and Fig. 3 is the main FIG. 3 is an explanatory diagram showing, in order of steps, an embodiment of a method for processing a final electrode of an in-line electron gun according to the invention. 20... Material board, 21... Overhanging process with ironing, 22... Overhanging cylindrical part, 23... Overhanging process with ironing, 24... Overhanging cylindrical part, 25... Hole punching process, 26 ...Burring prepared hole, 27...Burring processing, 28a, 28
b, 28c... Cylindrical part, 29a, 29b, 29c
...Lens section.

Claims (1)

[Claims] 1. In a method of processing an electrode for an in-line electron gun in which the main lens is formed by three adjacent cylindrical parts, an overhanging process involving ironing is performed on the material plate at locations corresponding to the two outer electron beam passage holes. to form an overhanging cylindrical portion, and then similarly perform overhang processing with ironing at the location corresponding to the central electron beam passage hole to form an overhanging cylindrical portion, and then Processing of an electrode for an electron gun, characterized in that a burring pilot hole is formed in the zenith portion, and then a burring process is performed on the three projecting cylindrical portions to form a lens portion having a cylindrical portion with a predetermined height. Method.