JPH0241858B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron tube cathode structure having a small lead wire diameter, high vibration resistance, and low cost, suitable for use in magnetrons and the like.

Currently, helical filament cathodes using thorium tungsten are widely used in magnetrons. This thorium tungsten wire is used with its surface layer subjected to carbonization treatment in order to increase the efficiency of thermionic emission. The carbonized portion becomes brittle, and the center lead and side leads, which support the helical filament and are connected to the lower end shield, may resonate due to external vibrations, causing the filament to break. To prevent this, it is possible to increase the rigidity by increasing the diameter of the center lead and side leads, but since these lead wires are made of expensive high-melting point metals such as W and Mo, the cost is low. It causes the increase in Therefore, while using lead wires having a relatively small diameter, the cathode structure as a whole including a center lead, side leads, etc. is constructed to be relatively strong as shown in FIG. 1. That is, upper and lower end shields 2 and 3 are fixedly supported at the ends of the center lead 4 and side leads 5, respectively, so as to sandwich the filament 1, and a heat-resistant insulator such as alumina porcelain is inserted into the through hole of the lower end shield 3. Spacer 10
is fitted with the center lead 4 inserted into its center hole. A groove 4a is previously provided in the center lead 4, and a stopper 11 is fitted therein to prevent the spacer 10 from moving in the axial direction. With such a structure, center lead 4
and the side leads 5 appear to be integrated with each other via the spacer 10, and have a great vibration-proofing effect. That is, with such a structure, there is no problem even if relatively thin lead wires are used. In this structure, a groove 4a is provided in the center lead 4, and a stopper 11 is fitted into the groove 4a, which is quite complicated.
If a Ru/Mo alloy is used as the brazing material for connection with the lower end shields 2 and 3, the temperature must be raised to approximately 1950 to 2000°C to fuse the material, whereas the firing temperature of the alumina porcelain material for the spacer 10 is from 1700
Since the temperature is 1800℃, when brazing the filament with the upper and lower end shields, lower the spacer to the position shown by the dotted line in Figure 1, and insert the spacer into the through hole of the lower end shield after brazing is complete. This is because consideration was given to ensuring that the spacer would not be exposed to the high temperatures during the brazing process. In FIG. 1, 6 is a terminal, 7 is a stem ceramic, and 8 is a seal component.

An object of the present invention is to provide an electron tube cathode structure which has sufficiently high vibration resistance without requiring the above-mentioned complicated structure and process, and using relatively thin lead wires as in the conventional art.

In order to achieve the above object, in the present invention,
A center lead bending part is provided directly below the spacer insertion part of the center lead to prevent the spacer from moving in the axial direction, and the filament is brazed to the upper and lower end shields using a brazing material whose melting point is below the spacer firing temperature. It was decided to.

FIG. 2 is a diagram showing one embodiment of the present invention. A bent portion 4b is provided on the center lead 4 directly below the normal (in use) position of the spacer 10 to prevent the spacer 10 from moving in the axial direction. In addition, for the brazing material between the filament 1 and the upper and lower end shields 2 and 3, use a brazing material such as Pt that has a melting point of 1800°C or less, that is, below the alumina porcelain firing temperature of the spacer. to ensure that they are not adversely affected. In this way, work such as providing a groove in the center lead, using a stopper, lowering the spacer and fitting it into the lower end shield through hole after the brazing work, and other parts are unnecessary.

As described above, according to the present invention, an electron tube cathode assembly can be obtained that uses relatively thin lead wires, has a simple structure, has sufficient vibration resistance, and is inexpensive.

[Brief explanation of drawings]

Figure 1 shows an example of a conventional cathode structure; Figure 2 shows an example of a conventional cathode structure;
The figure shows one embodiment of the present invention. 1... Filament, 2... Upper end shield, 3... Lower end shield, 4... Center lead, 4b... Bent part, 5... Side lead, 10
……Spacer.

Claims (1)

[Claims] 1 A helical filament that emits thermoelectrons,
This filament is held between upper and lower end shields located at both ends, and the upper end shield is connected to the center lead end inserted into the center hole of a spacer made of a cylindrical heat-resistant insulator that fits into the lower end shield through hole. In the method for manufacturing an electron tube cathode assembly in which the lower end shield is fixedly supported at the end of the side lead at the outer periphery of the through hole, the spacer is inserted into the center lead, and the center lead is bent in advance. manufacturing an electron tube cathode assembly, characterized in that the spacer is positioned in the axial direction by a part, and then the filament is brazed to the upper and lower end shields using a brazing material whose melting point is lower than the firing temperature of the spacer. Method.