JPS6035777B2 - Manufacturing method of impregnated cathode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing an impregnated cathode, and more particularly to a method for manufacturing an impregnated cathode that has high insulation resistance between cathode heaters and is useful for use in cathode ray tubes and the like.

Conventional technology: An impregnated cathode pellet is fixed to the upper end of the cathode support cylinder.
A conventional indirectly heated impregnated cathode in which a heater is disposed within a cathode support cylinder has a structure as shown in FIGS. 1 to 3.

That is, in FIG. 1, reference numeral 1 is an impregnated cathode pellet, in which a porous tungsten substrate is immersed with an electron-emissive material in a high salt solution in hydrogen gas. 2 is a cathode support cylinder, 3 is a brazing material, and 4 is a heater. An insulator 5 made of alumina or the like is sprayed or smeared on the surface of the heater wire.

The brazing material 3 of this impregnated cathode is
As described in the conventional example in Japanese Utility Model Application Publication No. 50-141557, in addition to fixing the cathode, pellet 1, and cathode support cylinder 2, the heater 4 is It also serves the purpose of preventing the evaporation of electron radioactive materials to the side. However, since this brazing material 3 uses a brazing material with relatively poor flow to prevent it from penetrating into the fine pores of the cathode pellet 3, pinholes are formed in the brazing material and the soldering material 3 leaks into the back surface of the cathode pellet 1. It is not possible to sufficiently prevent the evaporation and diffusion of electron radioactive materials. So, as expected, it was beautiful in 1974.
As disclosed in No. 52873 (Japanese Utility Model Publication No. 50-141557), the configuration shown in FIG. 2 has been considered.

That is, in Fig. 2, 6 is a second layer of soldering material such as platinum soldering material, and after the conventional first layer of soldering material 3 is deposited, it is deposited again using a high frequency electric furnace or the like to form the first layer of soldering material. The purpose is to fill Piwahole 3. However, even with this configuration, since the brazing material is used on the back side of the cathode pellet, even if the wax flow is poor, the brazing material flows into the fine pores of the cathode pellet, reducing the amount of electron radioactive material impregnated. In addition, pinholes in the soldering material cannot be completely prevented even if the soldering material for the second layer is made of a material with good flow. During the impregnation process, the back surface of the cathode pellet 1, that is, the exposed surface of the brazing material that has adhered to the nucleus, is contaminated and it is difficult to remove it;
There are drawbacks such as the electron radioactive substance entering the heater side during brazing with the cathode support cylinder 2 and having an adverse effect on operation. Furthermore, as shown in FIG. 3, a structure in which the cathode pellet and the cathode support cylinder 2 are fixed to each other via a metal plate 7 has been considered.

This is done to completely prevent pinholes in the brazing material, but since these are fixed using the two layers of brazing material mentioned above, as shown in the figure, the amount of impregnation of the electron radioactive substance as mentioned above is limited. However, the disadvantages that the amount of electron radiation decreases and the electron radioactive material gets around to the heater side during brazing still remain. Also, Miiso No. 48-99507 (Jitsu Kaiho 50-46
As disclosed in Japanese Utility Model Publication No. 057) and Japanese Utility Model Publication No. 45-31543, it is conceivable to fix the metal plate interposed between the cathode pellet and the cathode support cylinder by welding or caulking, but the cathode support The walls of these neap cathode parts, such as the cylinder, are thin and cracks occur during welding, and there are naturally gaps when caulking, so electron radioactive materials can easily seep through the gaps when the cathode is operating at high temperatures. It extends around the heater side. Problems to be Solved by the Invention As mentioned above, various attempts have been made to prevent electron radioactive substances from entering the heater side in impregnated cathodes used in cases such as cathode ray tubes that require a high-supply green resistance between the cathode heaters. However, it is difficult to obtain one that maintains the electron emission characteristics for a long time and also maintains the insulation resistance well over 100 feet, which has the disadvantage that the life of the cathode portion is short.

Means for Solving the Problems In view of this situation, the present invention is designed to prevent electron radioactive substances from getting around to the heater side at all, and to maintain good insulation resistance between the cathode heaters even during operations of about 1000 cycles. Specifically, first, a metal plate is airtightly fixed to the upper end of the cathode support cylinder using a wax material with good solder flow, and then the upper surface of the metal plate is It is manufactured by fixing cathode pellets together by welding.

Function: Since the impregnated cathode manufactured according to the present invention is manufactured by the method described above, there is no risk of the Kasumi anti-reflection material getting into the inside of the cathode cylinder where the heater is inserted, and the cathode pellet is made by welding. Because it is firmly fixed, there is no risk of the wax material seeping into the fine pores of the cathode pellet and reducing the electron radioactive material, and it maintains good electron emission characteristics and insulation resistance between the cathode heaters even over a long period of 10,000 hours. Maintain and operate.

Embodiment FIG. 4 shows a sectional view of a monkey-containing cathode manufactured according to an embodiment of the present invention, and 1 to 7 show the same parts as in FIG. 3.

In this impregnation type manufacturing procedure, first, the metal plate 7 is airtightly fixed to the upper end of the cathode support cylinder 2 using a soldering material 6 with good wax flow so as to avoid any gaps. This brazing material 6 may be placed separately, or may be placed on the inner surface of the upper end of the cathode support cylinder or on the metal plate 7.
It is also possible to preliminarily deposit a metal to serve as a brazing material on the lower surface of the plate by plating or vapor deposition. Next, a cathode pellet 1 is placed on the upper surface of the metal plate 7, and the periphery thereof is fixed by electric welding. After that, the impregnated cathode is formed by inserting and fixing the heater 4 inside the cathode support cylinder 2 or fixing the heater 4 and the cathode support cylinder 2 separately so that the heater 4 is located inside the cathode support cylinder 2. Form. In the above-mentioned embodiment, an example of a cup-shaped metal plate was used as the metal plate 7, but it goes without saying that the same applies to a flat metal plate as shown in FIG.

Effects of the Invention As explained above, in the impregnated cathode manufactured according to the present invention, since the soldering material is not poured into the cathode pellet, the waxing material does not seep into the cathode pellet, and electron radioactive substances are sufficiently immersed in the cathode pellet. In addition, since the metal plate 7 can completely prevent electron radioactive substances from contaminating the inside of the cathode support cylinder, it is possible to maintain good electron emission characteristics and insulation resistance between the cathode heaters even during long-term use. can.

FIG. 5 shows the insulation resistance between the cathode heaters of the impregnated cathode manufactured according to the present invention and the conventional product (in the case of FIG. 1), along with changes over time. In the cathode, region 0 is the characteristic range of a conventional impregnated cathode.

As is clear from FIG. 5, the product according to the present invention has excellent initial characteristics and changes over time.

As a result of the above, impregnated cathodes can now be used in fields that require high insulation resistance, such as cathode ray tubes, and the advantages of impregnated cathodes, such as high current density and long life, can now be fully utilized. .

[Brief explanation of drawings]

1 to 3 are cross-sectional views showing the structure of a conventional impregnated cathode, FIG. 4 is a cross-sectional view showing the structure of an impregnated cathode manufactured according to an embodiment of the present invention, and FIG. 5 is a cross-sectional view showing the structure of a conventional impregnated cathode. FIG. 3 is a diagram illustrating the aging characteristics of insulation resistance of the present invention (area 1) and the conventional example (area b). 1... Impregnated cathode pellet, 2... Cathode support cylinder,
4... Heater, 6... C material, 7... Metal plate. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. In a method for manufacturing an impregnated cathode in which an impregnated cathode pellet is fixed to the upper end of a cathode support cylinder via a metal plate, after the metal plate is airtightly fixed to the upper end of the cathode support cylinder with a brazing material. A method for manufacturing an impregnated cathode, comprising fixing the impregnated cathode pellets to the upper surface of the metal plate by welding.