JPH0334825Y2 - - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a directly heated cathode used in cathode ray tube electron guns and the like.

B. Prior Art An example of a directly heated cathode is shown in FIGS. 1 and 2 and will be described. In the figure, 1 is an insulator made of a heat-resistant insulator such as ceramic, and the planar shape is approximately oval, and the flat plate part 1 has a through hole in the center.
A cylindrical projecting wall 1b is provided protruding from the center of the projecting wall 1.
Lead insertion holes 1c, 1c are formed in the flat plate portion 1a adjacent to the outside in the diameter direction of b, and projecting walls (spacers) 1d, 1d are provided protruding from both longitudinal edges of the flat plate portion 1a. . 2, 2 have one end protruding below the flat plate portion 1a, respectively, and lead insertion holes 1c, 1c.
The leads 3, 3 are inserted through the leads 3, 3 and fixed with an adhesive such as fritted glass, and each of the leads 2, 3 is a plate spring whose one end is welded and fixed to the leads 2, 2, and whose other end is bent outward on the side of the projecting wall 1b. Reference numeral 4 denotes a tape-shaped heater whose both ends are welded and fixed to the bent portions 3a of the leaf springs 3, 3, and is stretched across the projecting wall 1b of the insulator 1, and is made of a metal having sufficient tensile strength in the heated state. For example, Fe-Ni-Cr alloy is used. Reference numeral 5 indicates a disk-shaped base metal welded and fixed to the center of the heater 4, and 6 indicates an emitter material adhered to the surface of the base metal 5.

This directly heated cathode is held at a predetermined distance from the grid electrode (not shown) of the electron gun, and when the heater 4 is energized, the base metal 5 is heated and the emitter material 6 emits electrons. . Here, a change in the distance between the grid electrode and the cathode, that is, the emitter material 6 on the base metal 5 (hereinafter simply referred to as the G-K distance) causes a change in the cut-off voltage, so it is necessary to maintain a predetermined distance.

By the way, the heater 4 is connected to the bent portion 3 of the leaf springs 3, 3.
When the heater 4 is welded and fixed to the heaters 4a and 3a, the heater 4 bends due to its elasticity, as shown in FIG. Therefore, the base metal 5 tends to shift in the horizontal direction, making it extremely difficult to arrange it coaxially with the through hole of the grid electrode. In addition, when the cathode is operated in this state, the heater 4 is deformed, the base metal 5 position is shifted horizontally or vertically (horizontally or vertically in the drawing), and the G
- Vary the cut-off voltage by changing the K interval. This causes the amount of electron beam emitted from the electron gun to fluctuate, which has the disadvantage that the brightness fluctuates after the start of operation.Especially in electron guns where the through holes in the grid electrode are made small in order to obtain high resolution, G-K Since the interval is also set small, there is a drawback that the change in the G-K interval becomes relatively large.

Therefore, in order to avoid these drawbacks, the heater 4 is bent in advance so as to be bent at the outer peripheral edge of the upper surface of the projecting wall 1b, as shown in FIG. 4, and then attached to the insulator 1. If the heater 4 is installed in a shifted state as shown in the figure, not only will the heater 4 be tilted and the G-K interval will be shifted, but also the heater 4 will be deformed when the cathode is operated, so it is necessary to perform the assembly process precisely. The drawback was that the quality was unstable.

Therefore, as shown in FIG. 6, the heater 4 is bent slightly outward from the outer peripheral edge of the upper surface of the projecting wall 1b.
By bending and forming the heater 4 in advance and attaching it to the insulator 1, it becomes easier to position the heater 4 and weld it to the bent portions 3a of the leaf springs 3, 3 compared to the case shown in FIG. However, there still remains the drawback that the tension of the heater 4 decreases due to thermal expansion of the heater 4 after energization, which increases the influence of vibrations and the like, and that the G-K interval tends to fluctuate.

C. Purpose of the invention The present invention was proposed in view of the above-mentioned drawbacks, and aims to improve assembly workability and provide a directly heated cathode with stable operation.

D. Structure of the invention The invention consists of a tape-shaped heater 4, which has a base metal 5 coated with an emitter material 6 fixed to its center;
7 and 8 are opposed projecting walls 1b on the insulator 1.
In the case where the projecting wall 1b is stretched across the
Heater portions 7b, 7c, 8b located on the outside of the projecting wall 1b with respect to heater portions 7a, 8a located in between.
The reinforcing portion is formed by making the wall thicker.

E. Examples Examples of the directly heated cathode according to the present invention will be described below with reference to FIGS. 7 and 8. In the figure, the same reference numerals as in FIG. 1 indicate the same parts, and the explanation will be omitted.
The only difference between the cathode according to the present invention and the conventional cathode is the shape of the heater. Figures 7 and 8 show an embodiment of the present invention, and in the figures,
Reference numeral 8 denotes a tape-shaped heater whose both ends are welded and fixed to the bent portions 3a, 3a of the leaf springs 3, 3, and is stretched across the projecting wall 1b of the insulator 1, and is located outside the projecting wall 1b. A tape-shaped reinforcing material 9 is pasted and welded to both ends of the wall 1b, and a thick reinforcing part 8 is attached to the thin part 8a located at the circular diameter of the projecting wall 1b.
It forms b. Further, the reinforcing portion 8b is bent and formed in advance.

When this cathode is operated, since the reinforcing part 8b of the heater 8 is thicker than the middle thin part 8a, the temperature rise in the reinforcing part 8b is small and it is difficult to deform mechanically. As in the example, G-
The distance K is maintained constant, and the axis misalignment with the through hole of the grid electrode is also prevented.

F. Effects of the invention According to the invention, since the reinforcing portion is formed by making the part located outside the projecting wall thicker than the part located between the projecting walls of the insulator of the heater, This reduces the temperature rise in the part fixed to the leaf spring, and also suppresses deformation in this part, so the tension of the heater can be maintained at the same tension as when the cathode is not operating, which prevents the cathode from shifting relative to the grid electrode. Since there is no cut-off voltage, fluctuations in the cut-off voltage are prevented and stable operation is possible. Furthermore, since the heater can be easily positioned, the ease of assembling the cathode is greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a top view showing an example of a general directly heated cathode, Fig. 2 is a sectional view taken along line A-A in Fig. 1, and Fig.
6 to 6 are partial sectional views showing a heater in a conventional directly heated cathode, and FIGS. 7 and 8 are a partial plan view and a partial sectional view of a directly heated cathode according to the present invention. 1... Insulator, 1b... Projection wall, 4...
Heater, 5... Base metal, 6... Emitter frequency, 8... Heater, 8a... Heater part between the projecting walls, 8b... Heater part outside the projecting walls.

Claims (1)

[Scope of utility model registration request] A tape-shaped heater to which a base metal coated with an emitter material is fixed to the center is stretched across the projecting walls of the insulator with both ends fixed to the bent portions of the leaf spring, and is located between the projecting walls. A directly heated cathode characterized in that a heater portion located outside of the projecting wall is formed with a thicker reinforcement portion than the heater portion.