JPS6266531A - Manufacture of impregnated cathode structure - Google Patents

Abstract

PURPOSE:To increase the reliability of an impregnated cathode structure by preventing an insulating agent from adhering to the inner surface of a support sleeve or the legs of a heater by coating the inner surface of the opening of the support sleeve and the outer surfaces of the legs of the heater with plastic layers and removing these layers after formation of an insulating material. CONSTITUTION:A heater 14 is placed at a given position so that the coil-like end 14b of the heater 14 is in contact with the surface of an insulating agent 16a. Then, an additional amount of the insulating agent 16a is poured into a support sleeve 12 until the agent 16a is packed up to a given level in the sleeve 12, thereby making a continuous insulating material 16. Next, after the upper surface of the material 16 is flattened, the material 16 is dried and then plastic layers 17 and 18 are removed. By the means mentioned above, the insulating agent 16a is reliably prevented from adhering to the inner surface of the sleeve 12 or the legs of the heater 14, thereby achieving increased reliability of an impregnated cathode structure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing an impregnated cathode structure which particularly requires high reliability.

(Technical background of the invention and its problems) Impregnated cathode assemblies are widely used not only in cathode ray tubes but also in electron tubes such as traveling wave tubes mounted on satellite towers and talistrons, which particularly require high reliability.

This impregnated cathode structure has a structure as shown in FIG. Reference numeral 11 in the figure is a cathode substrate made of a porous substrate impregnated with an electron emitting substance, 11a is its electron emitting surface, 12 is a support sleeve fixed by brazing to the back side of the cathode substrate, 13 is a brazing material layer, 14 is a heater, 15 is a leg of the heater,
15a is the heater wire, 15b is an auxiliary wire added for reinforcement, 15c is an auxiliary winding that prevents the heater wire from melting due to instantaneous current and also serves as reinforcement; 16
is raining insulating filler.

In manufacturing such a cathode structure, the support sleeve 1
The heater 14 is placed in a predetermined position with the opening 12a of the heater 2 facing upward, and a muddy insulating filler is poured into the interior, which is heated and dried to embed the heater. The (flame) porous pole substrate 11 is impregnated with an electron emitting material.

It has been confirmed that such a manufacturing method involves the following inconveniences. That is, the negative part of the insulating filler tends to adhere to the inner peripheral surface 12b of the support sleeve on the opening side and the outer periphery of the beater leg 15. If the insulating filler adheres to the inner circumferential surface of the support sleeve and the heater legs, it may cause problems when resistance welding a cathode support (not shown) to the outer periphery of the opening of the support sleeve, or when resistance welding platinum connection leads to the heater legs. To,
There is a risk that highly reliable welding may not be possible due to the attached insulator. In particular, if it adheres to the heater legs, it is extremely difficult to remove because of the windings, and when removed, there is a risk that the heater legs may be deformed or the insulating filling may peel off. Therefore, there is a problem that it is difficult to obtain sufficiently high reliability.

(Objective of the Invention) The present invention solves the above-mentioned inconveniences, reliably prevents the insulating filler from adhering to the inner peripheral surface of the support sleeve and the heater legs in the process of embedding the insulating filler into the support sleeve, and improves reliability. The present invention provides a method for manufacturing an impregnated cathode structure with high properties.

[Summary of the invention]

This invention is a process of embedding a heater in a support sleeve bonded to a porous cathode substrate using an insulating filler, and a plastic layer is coated on the inner periphery of the opening side of the support sleeve and the outer periphery of the legs of the heater. This method of manufacturing an impregnated cathode structure is characterized in that the plastic layer is embedded in the plastic layer, and then the plastic layer is removed. This reliably prevents the insulating agent from adhering to the inner circumferential surface of the support sleeve and the heater legs, making it possible to obtain a highly reliable impregnated cathode structure.

[Embodiments of the invention]

Examples thereof will be described below with reference to the drawings. Identical parts are designated by the same reference numerals.

First, as shown in FIG. 1a, the leg portion 15 of the heater 14 is
Apply a mixture of epoxy resin and curing agent to the outer periphery of the
This is cured to cover the plastic layer 17. On the other hand, as shown in the diagram, a porous tungsten cathode substrate 11
The support sleeve 12 is joined to the back side of the support sleeve by soldering, and a mixture of epoxy resin and a hardening agent is similarly applied to the inner periphery of the open end 12a of the support sleeve, and this is hardened to cover the plastic layer 18. do. Then, as shown in the figure, a part 16a of a mud-like insulating material made of alumina is poured into the support sleeve from above to a predetermined thickness D to flatten the surface. The thickness D of the part 16a of the insulating material is determined by drying the insulating material so that the distance between the coiled tip of the heater and the cathode base becomes a predetermined distance when the anode structure is completed.
The dimensions should also take into account shrinkage due to sintering.

The porous cathode substrate 11 is made by shrink-molding tungsten powder with a particle size of 3 to 10 μm into a rod shape and then sintering it in a reducing atmosphere. This porous tungsten sintered body was machined to form an electron emitting surface with an outer diameter of 11.3 mm and a radius of curvature of 10 mm, and a circumferential groove for joining the support sleeve was formed by cutting. It is constructed by removing impregnated copper with nitric acid and high temperature heating in a hydrogen furnace. An opening at one end of a support sleeve 12 made of dipropylene is fitted into a circumferential groove on the outer periphery of the back surface of the porous cathode substrate 11, and a brazing material made of molybdenum-ruthenium is placed therein. A similar brazing material layer 13 is also formed to prevent later impregnated electron emitting material from diffusing into the insulating filler during operation.

Next, the heater 14 shown in FIG. 1a is inserted so that its coiled tip 14b is in contact with the surface of the insulating material 16a, and placed in a predetermined position. Then, an additional amount of insulating material is poured from above again, filling the support sleeve to a predetermined position as shown in FIG. Note that the alumina powder naturally settles and lowers the top surface of the insulating material, so add a predetermined amount taking this into account. In this way, a connected insulating filler 16 is obtained. The upper surface of this insulating filler 16 is shaped to be flat.

This insulating filler is then dried to give a rough plasti layer 17.
Remove 18. Removal of this plastic layer involves heating the cathode assembly in the state shown in Figure 2 at approximately 1200°C in a hydrogen furnace.
The epoxy resin and binder can be removed by evaporation.

Next, the insulating filler is sintered in vacuum at a temperature of 1800° C. for 2 hours.

Then, on the porous cathode substrate 11, BaO1CaO1Al2
It is impregnated with an electron emitting substance such as O3.

In this way, an impregnated cathode structure having the structure shown in FIG. 3 is completed.

Note that the plastic material is not limited to those mentioned above, and other materials may be used. Further, the removal is not limited to heat treatment, but may be mechanically peeled off.

(Effects of the Invention) According to the invention described above, the inner periphery of the opening of the support sleeve and the outer periphery of the heater leg are filled with an insulating agent while the plastic layer is coated, and then this is removed and sintered. , no insulating material adheres to the inner circumferential surface of the end of the support sleeve and the heater legs, so that the welding of the cathode support to the support sleeve and the welding of the connection leads to the heater legs can be performed reliably and efficiently. A highly reliable impregnated cathode structure can be obtained.

[Brief explanation of drawings]

1A and 1B are longitudinal cross-sectional views showing an insulating agent filling process according to an embodiment of the present invention; FIG. 2 is a vertical cross-sectional view showing a combination thereof; and FIG. 3 is a vertical cross-sectional view showing an impregnated cathode structure. It is. DESCRIPTION OF SYMBOLS 11... Cathode base, 12... Support sleeve, 14... Heater, 15... Heater leg part, 16... Insulating filler, 17.18... Plastic layer.

Claims (1)

[Claims] In the method for manufacturing an impregnated cathode structure, the method includes joining a support sleeve to a porous cathode base, embedding a heater in the support sleeve with an insulating filler, and impregnating the cathode base with an electron emitting substance, wherein the heater is filled with an insulator. An impregnated cathode structure characterized in that, in the step of embedding with an agent, the inner periphery of the opening side of the support sleeve and the outer periphery of the leg of the heater are covered with a plastic layer and then the plastic layer is removed. manufacturing method.