JPH05258660A - Cathode for electronic tube - Google Patents

Abstract

PURPOSE:To minimize the welding position between a sleeve and a cap. CONSTITUTION:A flange 25 is formed on the opening of-a cap body 23 in which a porous sintered body is received, and the angle theta nipped by the flange 25 and the cap body 23 is set at 0 deg. or more and lower than 90 deg.. Therefore, since the electrons flying out from the porous sintered body 2 are shielded by the flanged when they try to escape from the gap between the cap 26 and a sleeve 4 into the sleeve 4 at the time of current-carrying, the generation of leak current can be relatively minimized. According to such a constitution, the welding position may be minimized to such a degree that the cap 26 can be fixed to and held by the sleeve 4 without shaking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode for an electron tube, which is suitable for application to a picture tube for a projection display device, for example.

[0002]

2. Description of the Related Art FIG. 6 shows a structure of a conventional cathode for an electron tube before assembly. FIG. 7 shows a structure of a cathode for an electron tube according to a conventional technique after assembly. As can be seen from FIGS. 6 and 7, the cathode 1 for an electron tube (hereinafter referred to as a cathode) 1 has a cylindrical porous sintered body 2 impregnated with an electron emitting substance, and the porous sintered body 2 is housed therein. And a sleeve 4 for accommodating and holding the cap 3.

FIG. 8 shows a structure in which the cathode 1 is assembled by resistance welding. In this case, first, the cap 3 is arranged on the tip surface of the convex portion 6 with the sleeve 4 fitted in the convex portion 6 of the insulating welding jig 5.
The porous sintered body 2 is assembled in the inside. Next, the welding electrodes 7 and 8 are moved in the directions of arrows P and Q, and are pressed against each other while abutting against the outside of the sleeve 4. In this pressurized state, the welding electrodes 7, 8
By applying a predetermined voltage in between, the sleeve 4 and the cap 3 are welded and fixed at the pressing point.
The porous sintered body 2 is deformed by the above pressing force and fixed to the cap 3.

[0004]

By the way, in the production of the cathode 1 by the conventional technique, the resistance welding process is performed over the entire circumference of the sleeve 4 and the cap 3 without any gap. If there is a gap between the sleeve 4 and the cap 3, the porous sintered body 2 is energized during energization for the test of the cathode 1 or energization after being incorporated in the electron tube. This is because there is a problem that the electrons that jump out from the above escape to the heater (not shown) side from the gap between the cap 3 and the sleeve 4, and so-called leak current occurs. The generation of such a leak current is a problem because it may cause a dielectric breakdown of the cathode 1. FIG. 9 shows a state in which a leak current is generated by the electrons 11 jumping out from the porous sintered body 2. The total leakage current is several μ because it does not cause the above dielectric breakdown.
It is necessary to limit the value to A or less.

Therefore, in order to limit the total leak current to a value of several μA or less, conventionally, every time the pressure welding by the welding electrodes 7 and 8 is performed, the cathode 1 is moved at a predetermined angle in the arrow R direction. After that, the resistance welding was performed over the entire circumference between the sleeve 4 and the cap 3.

However, when resistance welding is performed over the entire circumference of the sleeve 4 and the cap 3 in this way, for example, when the sleeve diameter is φ1.6, the above-mentioned leakage current value is satisfied. In addition, there is a problem in that resistance welding must be performed at approximately 26 points or more, and the manufacturing man-hours for that purpose are considerably increased. Specifically, it usually took about 1 minute to manufacture one cathode 1.
In addition, the fact that there are many welding points means that the welding electrodes 7, 8
Since the number of times of replacement (for example, once for every 30 cathodes) also increases, there is a problem that the number of steps required for the replacement also increases. Further, there is a problem that the cost of the cathode 1 as a finished product increases because the consumption of the welding electrodes 7 and 8 is accelerated.

The present invention has been made in view of the above problems, and an object thereof is to provide a cathode for an electron tube capable of relatively reducing the number of welded portions.

[0008]

The cathode for an electron tube of the present invention comprises:
For example, as shown in FIG. 1, a high-melting-point metal porous sintered body 2 impregnated with an electron emitting substance, a cap in which the porous sintered body 2 is housed, and a sleeve 4 in which the cap is housed. In the cathode for an electron tube having, a substantially umbrella-shaped flange 25 having a diameter D ₁ larger than the diameter D _{2 of the} sleeve 4 is formed in the opening of the cap 26.
5 and the side surface of the cap 26 have an angle θ of 0 ° or more and 90 ° or less.

[0009]

According to the cathode for an electron tube of the present invention, the porous sintered body 2
A substantially umbrella-shaped flange 2 is provided in the opening of the cap 26 in which the
5 is formed, and the angle θ sandwiched between the flange 25 and the side surface of the cap 26 is 0 ° or more and 90 ° or less. For this reason, even if the electrons jumping out from the porous sintered body 2 at the time of energization try to escape from the gap between the cap 26 and the sleeve 4, the electrons are shielded by the flange 25, so that the leakage current can be relatively reduced. it can.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the cathode for an electron tube of the present invention will be described below with reference to the drawings. In the drawings referred to below, parts corresponding to those shown in FIGS. 6 to 9 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 shows the structure of an electron tube cathode according to this embodiment after assembly. FIG. 2 shows the structure before assembly of the cathode for an electron tube according to this embodiment. As can be seen from FIGS. 1 and 2, a cathode 21 for an electron tube (hereinafter, referred to as a cathode) according to the present embodiment includes a cylindrical porous sintered body 2 impregnated with an electron emitting substance, and the porous sintered body. It has a cap 26 for accommodating 2 and a sleeve 4 for accommodating and holding the cap 26. The porous sintered body 2 is made of tungsten or the like, and the cap 26 and the sleeve 4 are made of tantalum or molybdenum.

A flange 25 formed integrally with the cap body 23 is provided at the opening of the cap body 23. As described above, in the cathode 21 of this embodiment, the cap 26 is composed of the cap body 23 and the flange 25. It should be noted that the shape of the flange 25 is not limited to the flat flange 25 as described above, and for example, as shown in FIG.
As shown in FIG. 5, it may be formed on the umbrella-shaped flange 27.
The porous sintered body 2 is omitted in FIG.

Generally speaking, the flanges 25 and 27 formed in the opening of the cap body 23 are substantially umbrella-shaped, and the flanges 25 and 27 and the side surface of the cap body 23 (the side surface of the cap 28). Angle θ (Fig. 1,
The angle (see FIG. 3) may be formed to be 0 degree or more and 90 degrees or less. The diameters D ₁ and D ₃ of the flanges 25 and 27 may be formed to be larger than the diameter D _{2 of the} sleeve 4.

FIG. 4 shows a structure in which the cap 26 having the flange 25 thus formed is assembled to the cathode 21 by resistance welding. In this case, first, the welding jig 5
The cap body 23 is fitted to the tip surface of the convex portion 6 with the sleeve 4 fitted in the convex portion 6, and the porous sintered body 2 is assembled in the cap main body 23. Next, the welding electrodes 7, 8 from the directions of arrows P, Q
Are moved and pressed against each other while abutting against the outside of the sleeve 4. In this pressurized state, a predetermined voltage is applied between the welding electrodes 7 and 8, so that the sleeve 4 and the cap 3 are welded and fixed at the pressed portion. The porous sintered body 2 is deformed by the above-mentioned pressing force and is fixed to the cap body 23. The welding margin d from the bottom of the cap 23 (see also FIG. 3) may be 0.5 mm or more.

FIG. 5 shows the welding points. In the case of resistance welding shown in FIG. 4, it is sufficient that there are four locations at 90-degree intervals as indicated by solid arrows 31 to 34. This corresponds to two pressure welding operations in the resistance welding machine.

As described above, according to this embodiment, it is possible to reduce the number of welding spots from 26 spots to only 4 spots as compared with the conventional technique. Therefore, the number of steps and cost for manufacturing the cathode 21 are reduced. In addition, the reason why the number of welded portions is not set to two at the minimum is to prevent rattling of the cap 28.

Further, since the number of welding points is reduced, laser welding is also possible. In the case of this laser welding, the welding points are 12 as shown by the dotted arrows 35 to 37 in FIG.
Three points may be provided at intervals of 0 degree. This corresponds to three laser welding operations. Laser welding does not require electrode replacement as in the resistance welding process, so
It is possible to further reduce the number of welding steps.

As described above, according to the above-described embodiment, the substantially umbrella-shaped flange 25 is formed in the opening of the cap body 23 in which the porous sintered body 2 is housed, and the flange 25 and the cap body 23 together. The angle θ that is sandwiched is 0 degrees or more and 90 degrees or less. For this reason, even if the electrons jumping out from the porous sintered body 2 at the time of energization try to escape from the gap between the cap body 23 and the sleeve 4, the electrons are structurally shielded by the flange 25, so that the leakage current is relatively generated. Can be reduced. Actually, the value of total leakage current could be set to a value of 3 μA or less.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0020]

As described above, according to the cathode for an electron tube of the present invention, a substantially umbrella-shaped flange is formed in the opening of the cap in which the porous sintered body is housed, and the flange and the side surface of the cap. The angle between the angles is 0 degrees or more and 90 degrees or less. For this reason, even if the electrons jumping out of the porous sintered body at the time of energization try to escape from the gap between the cap and the sleeve, the gap is structurally shielded by the flange, so that the leakage current is relatively generated. The effect is that it can be reduced to a very small amount.

Further, since the flange is formed, there is an effect that the number of welding points for welding the side surface of the cap and the sleeve can be relatively reduced. as a result,
The effect that the number of manufacturing steps of the cathode for an electron tube can be reduced can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of an embodiment of an electron tube cathode according to the present invention.

FIG. 2 is an exploded view showing the structure of the cathode for an electron tube of FIG.

FIG. 3 is a cross-sectional view showing the configuration of another embodiment of the cathode for an electron tube according to the present invention.

FIG. 4 is a partial cross-sectional view showing the structure of the cathode for an electron tube of FIG. 1 during assembly.

5 is a cross-sectional view showing a welded portion of the cathode for an electron tube of FIG.

FIG. 6 is an exploded view showing a structure of a conventional cathode for an electron tube.

7 is a cross-sectional view showing the structure of the cathode for an electron tube of FIG. 6 after assembly.

8 is a partial cross-sectional view showing the structure of the cathode for an electron tube of FIG. 7 during assembly.

9 is a partially omitted cross-sectional view provided for explaining a leak current in the cathode for an electron tube of the example of FIG. 7. FIG.

[Explanation of symbols]

 2 Porous Sintered Body 4 Sleeve 23 Cap Body 25 Flange 26 Cap

Claims (1)

[Claims] 1. A cathode for an electron tube, comprising: a porous sintered body of a refractory metal impregnated with an electron emitting substance; a cap in which the porous sintered body is housed; and a sleeve in which the cap is housed. A substantially umbrella-shaped flange having a diameter larger than the diameter of the sleeve is formed in the opening of the cap, and the angle between the flange and the side surface of the cap is 0 degrees or more and 90 degrees or less. A cathode for an electron tube characterized by.