JPH04264324A - Cathode structure for impregnated cathode - Google Patents

Abstract

PURPOSE:To improve the efficiency of heat absorption by blackening the inside and outside faces of a cathode sleeve, restrain heat radiation by the reflection of an eyelet encircling it, secure the operating temperature of a cathode at a low power, restrict a space change between the plane of the impregnated cathode and the first electrode after switch-on to a small level and restrain a change in brightness on a screen by using metal materials different in thermal expansion coefficient for the cathode sleeve, the eyelet and a holder. CONSTITUTION:An eyelet 5 is welded to a cathode sleeve 2 with the inside and outside faces blackened by a sintered film 4, so as to encircle the side face thereof. The eyelet 5 is welded to a holder 6, and in addition the holder 6 is inserted in and fixed to a cathode support 7. The cathode sleeve 2, the eyelet 5, the holder 6 and the cathode support 7 are formed with materials different in thermal expansion coefficient.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode assembly for an impregnated cathode, and more particularly to a cathode assembly for an impregnated cathode used as a high current density cathode assembly in an electron tube or the like.

0002

2. Description of the Related Art In general, a cathode assembly for an impregnated cathode for a cathode ray tube (hereinafter referred to as cathode assembly) has a structure as shown in FIG. That is, the heater 3 and the impregnated cathode sleeve 2 containing the heater 3 are fixed to the cathode support 17 by welding or the like. Conventional cathode sleeves 2 generally have metallic luster on both the inner and outer surfaces. Considering only the heat absorption from the heater 3, the inner surface of the cathode sleeve 2 is
As disclosed in Japanese Patent Application Laid-Open No. 61-288339, blackening is desirable. On the other hand, if the outer surface is also blackened, the amount of heat radiated is large and a larger heater power is required to obtain a predetermined operating temperature.

Furthermore, when an electron gun assembly equipped with a cathode assembly is actually incorporated into, for example, a picture tube and operated, as the temperature of the cathode rises after switching on, the cathode sleeve 2,
Each component, such as the cathode support 7, expands thermally, and the distance between the surface of the impregnated cathode 1 and the first electrode 8 changes, changing the brightness of the screen. In particular, about 100
This is noticeable in the case of cathodes that operate at high temperatures exceeding 0°C.

0004

In the conventional cathode assembly described above, it is conceivable that only the inner surface of the cathode sleeve is blackened in order to increase the efficiency of heat absorption from the heater. One possible method for this is to mask the outer surface of the cathode and blacken it, but this method has the problems that the cathode sleeve is very small and that it is difficult to mass produce, resulting in high costs.

[0005]Also, in order to suppress the change in brightness after switching on, there is a method of changing the cathode sleeve, cathode support, first electrode material, and shape, but since it is around the cathode, it has a negative impact on emissions. There are restrictions on the materials that can be used, such as those that cannot be used, and there is a problem in that the materials that can be used are limited.

[0006] An object of the present invention is to provide a cathode structure that is inexpensive and free from restrictions on the use of materials surrounding the cathode.

[0007]

[Means for Solving the Problems] The present invention provides a cathode assembly for an impregnated cathode that includes an impregnated cathode, a cathode sleeve to which the immersed cathode is fixed, and a cathode support that supports the cathode sleeve. A cathode sleeve having a heat-absorbing film formed on its inner and outer surfaces, an eyelet formed to surround the side surface of the cathode sleeve, a holder fixed to one end of the eyelet, and a cathode support fixed by inserting the holder. It has

[0008] the cathode sleeve; the eyelet;
The holder and the cathode support are made of materials having different coefficients of thermal expansion.

[0009]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an enlarged sectional view of one embodiment of the present invention.

As shown in FIG. 1, the cathode sleeve 2 to which the impregnated cathode 1 is fixed is heated by a heater 3 inserted into the cathode sleeve 2 to reach an operating temperature (approximately 1100° C.
).

The cathode sleeve 2 is obtained by molding a Ta or Mo tube, and its inner and outer surfaces are blackened with a sintered film 4 containing a high melting point metal powder, such as tungsten powder.

[0013] The eyelet 5 is, for example, a cathode sleeve 2.
It is made of a metal material with a larger coefficient of thermal expansion than the cathode sleeve 2, and has a shape that surrounds the side surface of the cathode sleeve 2.

The holder 6 for fixing the eyelet 2 is further made of a metal material with a large coefficient of thermal expansion.

Finally, the impregnated cathode 1, the cathode sleeve 2,
A structure consisting of an eyelet 5 and a holder 6 is inserted and fixed to the cathode support 7 to form a cathode structure.

As described above, the cathode sleeve 2 whose inner and outer surfaces are blackened improves the heat absorption efficiency from the heater 3. on the other hand,
Thermal radiation due to the blackening of the outer surface is greatly alleviated because the non-blackened eyelets 5 surrounding the side surfaces function as reflectors, and therefore the operating temperature can be maintained with low power. With such a structure, it is not necessary to selectively blacken only the inside of the cathode sleeve, so it is obvious that the manufacturing process is simplified.

Further, heat conduction after the switch is turned on is conducted in the order of the cathode sleeve 2, the eyelet 5, and the holder 6, and the steady equilibrium temperature also decreases in this order.

Therefore, by using materials with larger coefficients of thermal expansion in the order of the cathode sleeve 2, eyelet 5, and holder 6, the surface of the impregnated cathode 1 and the first Since changes in the distance between the electrode 8 and the electrode 8 can be suppressed, changes in the brightness of the screen can be suppressed. Alternatively, if the first electrode 8 is deformed by the radiant heat of the impregnated cathode 1, the eyelet 5
By optimizing the materials of , holder 6 and cathode support 7,
It can solve the problem of screen brightness change.

[0019]

[Effects of the Invention] As explained above, according to the cathode structure according to the present invention, the heat absorption efficiency can be increased by the blackening of the inner surface of the cathode sleeve, and the thermal radiation caused by the blackening of the outer surface is reflected by the eyelet surrounding it. This results in less heat escaping, requires less power, and is easier to manufacture.

Furthermore, by using materials with different coefficients of thermal expansion for the cathode sleeve, eyelet, and holder, it is possible to suppress changes in brightness on the screen after the switch is turned on.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of an example of a conventional cathode assembly.

[Explanation of symbols]

1 Impregnated cathode 2 Cathode sleeve 3 Heater 4 Sintered film 5 Eyelet 6 Holder 7,17 Cathode support 8 First electrode

Claims (2)

[Claims] Claim 1: A cathode assembly for an impregnated cathode comprising an impregnated cathode, a cathode sleeve to which the immersion cathode is fixed, and a cathode support supporting the cathode sleeve, wherein a heat-absorbing film is provided on the inner and outer surfaces. A cathode sleeve is formed, an eyelet is formed to surround a side surface of the cathode sleeve, a holder is fixed to one end of the eyelet, and a cathode support is fixed by inserting the holder. Cathode structure for impregnated cathode. 2. The impregnated cathode according to claim 1, wherein the cathode sleeve, the eyelet, the holder, and the cathode support are each made of materials having different coefficients of thermal expansion. cathode structure.