JPH0216537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron gun for a cathode ray tube, which can be assembled with high precision and has a large diameter electron lens.

As a method of increasing the lens diameter of an electron gun as much as possible within a given valve neck tube, it has long been practiced to use a conductive film coated on the inner wall of the valve neck tube as one of the electrodes constituting the main lens. However, since the bulb neck tube is usually a glass tube, it is difficult to achieve high dimensional accuracy, and it is also difficult to achieve accurate positional relationship with the counter electrode, making it difficult to obtain a main lens with few aberrations.

A structure for improving this point is shown in Japanese Patent Application Laid-Open No. 55-41678. In other words, the fourth diameter is as large as possible.
The cathode side end of the grid (second anode) has a small diameter and is supported by an insulating rod via a protruding support provided on the outside of this part, while the third grid (first anode) has a small diameter of the fourth grid. It is made in two parts, a cathode side part and a fluorescent surface side part, which are connected at the time of assembly by a neck part that passes through the parts without contacting them. However, this structure is accompanied by reduced precision due to the connection of the two divided parts and difficulty in assembly.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electron gun for a cathode ray tube that does not have the above-mentioned problems, has good dimensional accuracy, is easy to assemble, and has a large diameter electron lens.

In order to achieve the above object, in the present invention,
A two-diameter electrode having at least two outer diameters, one end having a small outer diameter and the other end having a large outer diameter (e.g., a third grid, although the outer diameter value may vary in multiple steps between the two ends).
The end of the large inner diameter electrode (e.g. the fourth grid), which surrounds the large outer diameter end of the grid and the space connected thereto, and whose inner diameter is larger than the large outer diameter part of the two outer diameter electrode, is located at the small outer diameter part of the two outer diameter electrode. An invaginated local part was created at the end of the extended large inner diameter electrode so as to be close to the electron gun axis without touching the small outer diameter part of the two outer diameter electrodes, and provided in this local part. The large inner diameter electrode is supported by the insulating rod via the protruding support portion.

FIG. 1 shows a bipotential electron gun embodying the present invention, and FIG. 2 is a sectional view taken along line A-A' in FIG. In these figures, 1 is the cathode, 2
3 is the heater, 3 is the first grid, 31 is the protruding support part of the first grid, 4 is the second grid, and 41 is the second grid.
The protruding support part of the grid, 5 is the third grid (two outer diameter electrodes), 51 is the small outer diameter part of the third grid, 52
53 is the large outer diameter part of the third grid, 6 is the protruding support part of the third grid, 6 is the fourth grid (large inner diameter electrode),
Reference numeral 61 denotes an invaginated local part 62 which is provided at the end of the fourth grid extending so as to surround a part of the third grid small outer diameter part 51 and close to the electron gun axis to the extent that it does not contact the third grid small outer diameter part. 7 is a protruding support portion of the fourth grid provided in the invaginated local area, and 7 is an insulating rod for supporting the electrode. FIG. 3 is a view from the cathode side when the protruding support portion 53 of the third grid is passed through the end of the fourth grid 6 during assembly of the electron gun. The outer diameter d of the protruding support part 53 of the third grid is
By setting the inner diameter D smaller than the inner diameter D of the fourth grid 6, the diameter portion of the third grid where the protruding support portion 53 is provided is the same as the diameter portion where the protrusion support portion 62 of the fourth grid (i.e., the invaginated local portion 61) is provided. On the other hand, by rotating it by a suitable angle Θ, the protruding support part 53 of the third grid can easily pass through the end of the fourth grid 6, as shown in FIG. After passing, the rotation angle Θ
is returned to 0 and each electrode is coaxially supported by the insulating rod 7 (usually the insulating rod 7 is made of high-voltage glass, and after heating and softening the insulating rod, the protrusions of each electrode are arranged in a line with an assembly jig). press-fit the end of the support).

FIG. 4 shows another example of the shape of the invaginated local part 61 of the fourth grid 6 according to the embodiment of the present invention, and in this way the protruding support part 62 can be made integrally with the grid.

FIG. 5 shows still another example of the fourth grid according to the embodiment of the present invention, in which the fourth grid 6' is
It can be divided into two parts that are symmetrical about the plane containing the electron gun axis. By using the fourth grid 6' having such a structure, a unipotential electron gun as shown in FIG. 6 can be manufactured. In the figure, 5a is the fifth grid,
51a is the small outer diameter part of the fifth grid, 52a is the fifth grid
The large outer diameter portion of the grid 53a is a protruding support portion of the fifth grid.

In the electron gun of the present invention, there is no work to connect two parts divided in the axial direction to form one electrode during assembly, and no axial bending occurs in one electrode. Assembly time is also reduced. If the assembly jig is properly made, there will be no eccentricity between the electrodes. The two outer diameter electrodes and the large inner diameter electrode according to the present invention are easy to manufacture. The local invagination of the large inner diameter electrode is in the shadow of the bottom surface of the large outer diameter part of the two outer diameter electrodes, so it does not affect the lens electric field. When using a bombarder in which the magnetic flux passes in the direction of the electrode axis for electrode degassing, the temperature of the protruding support part is generally somewhat lower than in the past, and the temperature of the protruding support part is lower at the point where the protruding support part is inserted into the glass insulating rod. Accidents such as damage to glass insulation rods due to thermal expansion are also reduced.

As described above, according to the present invention, an electron gun having a large diameter electron lens can be easily assembled with high precision.

[Brief explanation of drawings]

FIG. 1 is a diagram of a bipotential electron gun embodying the present invention, FIG. 2 is a sectional view taken along the line A-A' shown in FIG. 4 and 5 are diagrams showing examples of different fourth grids according to embodiments of the present invention, and FIG. 6 is a diagram of a unipotential electron gun embodying the present invention. 5...Third grid, 51...Third grid small outer diameter part, 52...Third grid large outer diameter part, 53...
...Third grid protruding support part, 6... Fourth grid, 61... Fourth grid invaginated local part, 62... Fourth grid protruding support part, 7... Insulating rod.

Claims (1)

[Claims] 1 At least two outer diameters, one end with a small outer diameter and the other end with a large outer diameter, are attached to an electrode system coaxially insulated and supported by an insulating rod through supporting parts protruding from each of the electrodes arranged along the electron gun axis. two outer diameter electrodes having;
In this electron gun for a cathode ray tube, which includes a large outer diameter end of the two outer diameter electrodes and a large inner diameter electrode that surrounds a space connected thereto and has an inner diameter larger than the large outer diameter parts of the two outer diameter electrodes, the large inner diameter electrode ends have two large inner diameter electrodes. A hole is extended to surround a part of the small outer diameter part of the outer diameter electrode, and the extended large inner diameter electrode end is placed close to the electron gun axis to the extent that it does not contact the small outer diameter part of the two outer diameter electrodes. An electron gun for a cathode ray tube, characterized in that an entrance part is provided, and this part has a protruding support part for a large inner diameter electrode.