JPS6013164Y2 - Directly heated cathode structure - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a directly heated cathode assembly suitable for use in a cathode ray tube.

Generally, a cathode ray tube has a built-in electron gun and a cathode that emits an electron beam.

If a directly heated type is used as the cathode, it consumes less power than an indirectly heated type, and it is possible to turn on the ignition, that is, turn on the power switch.
) It has a characteristic that it has a quick start-up time from when it starts operating until it starts operating, making it very convenient for use in image pickup tubes and monitor tubes for portable television cameras.

By the way, the directly heated cathode structure that has been commonly used is constructed as shown in FIGS. This is an insulating substrate to be combined.

This insulating substrate 1 is made of ceramic and is a plate of a predetermined thickness with a notch 2 formed at one end.

A pair of conductive filament supports 3 and 4 are implanted through the insulating substrate 1 so as to face each other at a predetermined distance.

A filament 5 is stretched between the filament supports 3 and 4. In this case, one end of the filament 5 is fixed to the rod-shaped filament support 3, and the other end is connected to a cylinder through a spring 6 located in the notch 2. filament support 4
The other end is in contact with the tip of a strip-shaped movable adjustment rod 7 located within the filament support 4.

Further, a base metal plate 8 is fixed to the surface of the filament 5 at the narrow center, and an electron emitting substance 9 is coated on the base metal plate 8.

The movable adjustment rod 7 described above is a means for regulating the distance between the first grid electrode 10 and the electron emitting material 9 to a predetermined dimension during assembly.

Note that 11 and 12 in FIG. 2 are adhesives made of glass powder.

By the way, in the cathode structure as described above, the filament 5 needs to have a small heat capacity and a large electrical resistance.

In the case of a directly heated cathode structure using a ribbon-shaped filament 5, it is necessary to fix the disk-shaped base metal plate 8 on top of the filament 5 as described above in order to obtain the required total current. Therefore, the width of the filament 5 is the same as that of the base metal plate 8.
The dimensions must be such that it can be welded sufficiently firmly and that it will not undergo deformation such as twisting.

Therefore, the width of the filament 5 is inevitably determined.

There are various methods for lowering the heat capacity and increasing the electrical resistance of the ribbon-like filament 5 having a constant width, but the most fundamental method is to reduce the thickness.

However, it cannot be made too thin in order to maintain reliability in cathode characteristics, especially in the case of filament breakage.

On the other hand, the material of the filament 5 is 30%W-70%Ni alloy, in this case, the above dimensions are width 0.20m thickness 0.
．． 025 mm is considered to be the limit.

In order to increase the electrical resistance from the above, it is necessary to increase the length of the filament 5.

However, when the conventional cathode structure is heated by electricity, the current circuit consists of the filament support 3 - filament 5 - movable adjustment rod 7, and it is not possible to obtain a sufficient length of the filament, so that the appropriate filament current cannot be obtained. can't get it.

The object of this invention is to provide a directly heated cathode structure which eliminates the above-mentioned conventional drawbacks.

Hereinafter, one embodiment of this invention will be described in detail with reference to the drawings.

Taking as an example a directly heated cathode assembly used in a single electron gun for a black and white television picture tube, the directly heated cathode assembly of this invention is constructed as shown in FIGS. 3 and 4, and is different from the conventional one described above. The filament has been improved to eliminate its shortcomings.

That is, the same parts as in the above-mentioned conventional art (FIGS. 1 and 2) are given the same reference numerals. In this invention, a high-resistance oxide layer 13 is provided on the back surface of the filament 5, that is, on the surface where the base metal plate 8 is not attached. is formed.

Cr oxide is used as the oxide layer 13, and in this case, a Cr-containing metal is provided on the main metal by cratting or plating, and then heat-treated in a moisture-adding hydrogen furnace to form a raw Cr oxide.

A high-resistance oxide film formed on the back surface of the filament 5 is used for the movable adjustment rod 7, which is provided near the spring 6 and slidably contacts and holds the back surface near the end of the filament 5. The layer 13 prevents a direct electrical short circuit between the filament 5 and the movable adjustment rod 7.The directly heated cathode assembly of this invention is constructed as described above and shown in the drawings, and has a layer 13 on the back surface of the filament 5. High resistance oxide layer 13
, electrical insulation is provided between the contact surfaces of the filament 5 and the movable adjustment rod 7.

Therefore, the current circuit is filament support 3 - filament 5 - spring 6 - filament support 4, and the filament 5 can maintain a sufficient length required for the cathode assembly, resulting in an appropriate directly heated cathode assembly. .

In the above embodiment, a direct heating type cathode assembly for a single electron gun used in a black and white television picture tube was described, but this invention is applicable to a direct heating type cathode assembly for an in-line three-electron gun used in a color television picture tube as shown in FIG. Needless to say, it can be applied to a thermal composite cathode structure.

Portions corresponding to those in the above embodiment are given the same reference numerals.

As explained above, according to this invention, a directly heated cathode structure with great practical value can be provided.

[Brief explanation of the drawing]

1 and 2 are perspective views showing a conventional directly heated cathode structure, FIGS. 3 and 4 are perspective views showing a directly heated cathode structure according to an embodiment of this invention, and FIG. 5 is a perspective view showing a directly heated cathode structure according to an embodiment of the invention. It is a perspective view which shows the modification of this invention. 1... Insulating substrate, 3, 4... Filament support, 5... Filament, 6...
...Spring, 7...Movable adjustment rod, 8...
...Base metal plate, 9...Electron emitting material, 10
...First grid electrode, 13... Oxide layer.

Claims (1)

[Claims for Utility Model Registration] An insulating substrate 1 and a pair of filament supports 3 embedded in this insulating substrate
, 4; a spring 6 fixed to the filament support; a ribbon-shaped filament 5 electrically connected to the pair of filament supports via the spring and stretched along the substrate surface; A base metal plate 8 whose surface is coated with an electron emitting substance 9 and which is fixed to the surface of the central portion of the filament; and a base metal plate 8 which is provided near the joining position of the filament to the spring and is slidable on the back surface of the filament. In the directly heated cathode assembly, a high-resistance oxide layer 13 is deposited and formed on the back surface of the filament that is in slidable contact with the movable adjustment rod 7. A directly heated cathode assembly characterized in that a direct short circuit between the filament and the movable adjustment rod is prevented by the interposition of the layer 13.