JPS59184431A - Cathode structure for cathode-ray tube - Google Patents

Abstract

PURPOSE:To obtain at a low cost a cathode structure having no possibility of causing sags by attaching an electron-discharging emitter to the flat intermediate top surface of a heater, which is formed by curving a ribbon-like metallic piece in its longitudinal direction in an almost W-shape, and fixing the ends of the heater to a pair of conductive terminals. CONSTITUTION:A heater 1 consists of a ribbon-like metallic piece 2, in which Ni for example is used as a base metallic layer and which is made of an alloy containing at least one metal chosen from among W, Mo, Fe and Cr. The ribbon- like metallic piece 2 is curved in an almost W-shape in its longitudinal direction. An electron-discharging emitter 3 is attached to the flat intermediate top surface of the heater 1. The ends 1a and 1b of the heater 1 are fused and fixed to a pair of conductive terminals 4 and 5. The emitter 3 consists of a disk-like cathode base metal coated with an electron-discharging oxide layer. The conductive terminals 4 and 5 are the flat heads of two lead wires 7 and 8 penetrating a disk-like insulator 6 made of glass or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a cathode assembly used in a cathode ray tube such as a picture tube, observation tube or image pickup tube.

Conventional configuration and its problems In a directly heated cathode structure in which an electron emitter is attached to the top surface of the middle part of a heater made of a ribbon-shaped metal piece, the heater, which is heated during operation, expands and sag. Therefore, it is necessary to devise a way to absorb the expansion of the heater. Therefore, a cathode assembly was devised in which a spring is connected to one end of a heater made of a ribbon-shaped metal piece, and the heater is constantly kept under tension by this spring. in this case,
Although the above-mentioned sagging can be almost completely prevented, since a considerable tension is applied to the heater, the heater
A temperature rise to 00°C causes a creep phenomenon, which significantly shortens the life of the heater. In addition, with a cathode structure in which the expansion of the heater is absorbed by rotation of the emitter attachment area, sagging of the heater can be sufficiently prevented.
In addition, a specially shaped heater is required, and torsional distortion occurs in the emitter attachment area immediately after the heater, resulting in undesirable results such as the emitter falling off, the heater being deformed, or the wire breaking.

OBJECTS OF THE INVENTION Accordingly, it is an object of the present invention to provide a cathode assembly at a low cost that does not cause tension or torsional strain on the heater and is free from the risk of sagging.

Structure of the Invention In the cathode structure of the present invention, a ribbon-shaped metal piece is bent into a substantially W-shape in the length direction to serve as a heater, and an electron radiation emitter is attached to the top surface of the flat intermediate portion directly or through an insulating layer. Attached. Then, both ends of the heater are fixed to a pair of current-carrying terminals, and this will be explained in detail below together with embodiments shown in the drawings.

DESCRIPTION OF THE EMBODIMENTS In FIGS. 1 and 2, the ribbon-shaped metal piece 2 forming the approximately W-shaped heater 1 has a base metal of Nikkeno νNi), tungsten (W), molybdenum 4M01° iron (
It is made of an alloy containing at least one selected from Fe) and chromium (Or), and is bent into a substantially W-shape in its length direction. An electron radiation emitter 3 is attached to the top surface of the flat intermediate portion of the heater 1. Also, both ends of the heater 1; 1a, 1
b is welded and fixed to a pair of current-carrying terminals 4 and 5. However, the emitter 3 is made of a disk-shaped cathode base metal with an electron-emitting oxide layer adhered to its surface. The current-carrying terminals 4 and 5 are the flat heads of two lead wires 7 and 8 that pass through a disc-shaped insulator 6 made of glass or the like, and the insulator 6 is a metal ring that surrounds this. 9 and lead wires 7, 8
Together, they constitute a header, which is inserted into a bottomed cylindrical control electrode (not shown) and welded to the cylindrical portion of the control electrode at the metal ring 9 portion.

The heater, whose temperature rises to approximately 800° C. by energization, undergoes considerable thermal expansion and elongation. The amount of elongation in a heater using a ribbon-shaped metal piece 2 with a length of 5 jnH reaches as much as 0.05 mW-Q, I In. However, the metal piece 2 constituting the heater is bent into a substantially W-shape, and both ends 1a and 1b are connected to a pair of current-carrying terminals 4.5.
3, the directions of the elongation are alternately opposite as shown by the arrows in FIG. As the heater stretches, its bending angle changes and it deforms into the shape shown by the broken line, but this is a deformation that can be restored, and the position occupied by the emitter attachment area hardly changes due to the cancellation of the stretching direction, so the emitter 3 The amount of deviation is small. Furthermore, since no tension or torsional strain is generated in the heater, shortening of the heater's lifespan can be avoided.

The amount of deviation of the emitter 3 will be approximately zero if the four sides of the substantially W-shaped heater 1 have the same length, but there is no need to make them the same length. The area where the emitter of heater 1 is attached has little heat conduction loss, and the temperature may be higher than that of the pond area.
The emitter 3 shifts slightly as the temperature increases. but,
This amount of deviation is at most about 0.01 mπ, which poses no practical problem.

Further, this amount of deviation can be estimated in advance. Therefore, the cathode may be arranged so that the emitter after the temperature rises will occupy the optimum position.

In the embodiment shown in FIG. 4, the approximately W-shaped heater 1
Since the heater has reinforcing ribs 10 having an arcuate cross section on its four sides, there is almost no deformation on the four sides of the heater. However, instead of forming such a reinforcing lip 10, the heater may be formed using a ribbon-shaped metal piece having a U-shaped cross section.

Since the operating temperature of a directly heated oxide cathode is usually relatively low, about 8 Q O'C, the heater material is not required to have a heat resistance strength of just over 9 degrees, but rather has a high electrical resistivity. A heater material with a high electrical specific resistance not only allows the heater voltage to be set high but also allows the overall length of the heater to be shortened, so it is advantageous in terms of heat resistance and strength, especially in the case of the present invention, which is approximately W-shaped.・The heater material suitable for this purpose is Ni as the base metal and MO as 6 to 6.
It is an alloy containing 35% by weight and 11 to 30% by weight of Fe. The content of Mo and Fe is determined by taking into consideration the desired heater operating temperature, heater power consumption, heat resistance strength, etc. Generally, the higher the heater voltage, the easier it is to use.
Contains 16% by weight or more of Mo, and has an electrical resistivity of approximately 100μ
Set to Ω・σ or more. In this case, the heat resistance strength is also on the order of magnitude, but if the MO content exceeds 35% by weight, the hardness of the alloy is on the order of magnitude, resulting in poor workability. The content of Fe is smaller than the content of Mo, and can be selected from the range of 1 to 30% by weight.

The electrical resistivity of the Ni-Mo-Fe alloy containing about 28% by weight of Mo and about 5% by weight of Fe as the Nii base metal is about 135 μΩ·min, and the workability is also good. =
! The heat resistance strength was approximately 4 s Ky, /- in terms of tensile strength at 800°C. Using this alloy, width 0
．． A 2ffiJ ribbon-shaped metal piece having a thickness of 0.02 mm and a length of 5#IIW was manufactured and bent into a substantially W-shape to manufacture a heater. Then, a cathode base metal serving as an emitter with a diameter Q of 8ffff and a thickness of 0.03 am was attached to the top surface of the flat intermediate portion, and an electron emissive oxide layer was provided. The heater voltage of this directly heated oxide cathode was o, e V, the heater power consumption was Q, 15 W, and the operating temperature was 750'C.

Do not attach the emitter directly to the emitter attachment area of the heater.
When attached via a heat-resistant insulating layer such as alumina, it can be used as an indirectly heated cathode. In this case, it becomes possible to contain 1 to 30% by weight of an element such as chromium (Cr), which affects the electron emission function of the emitter, in the heater material alloy. 8
So-called nichrome alloys such as Q%Ni and 20%IQr are inexpensive, have a large electrical resistivity, and are excellent in terms of heat resistance strength.

Also, 16%Mo, 15.5%Or, 5.6%F
e.

4% W1 balance Ni -Mo -Or -Fe -
W alloy-1, 9% MO, 22% Or, 1 B,
5% Fe, 0.6% W1 balance Ni -
The Mo-0r-Fe-W alloy (both weight%) is
The tensile strength at 800°C is about 4 oKy/-, and the electrical resistivity is about 12Q to 130 μΩ·(m).

An impregnated type emitter can be used, but
Since the operating temperature in this case is as high as about 950 to 1100°C, the heat resistance strength of the heater must be taken into consideration. A heater material suitable for this purpose is an Nt-W alloy.

In general, when the W content is high, both the heat resistance strength and the electrical resistivity are high.
An impregnated cathode whose heater is formed using a -W alloy can sufficiently withstand continuous use for about 1000 hours at an operating temperature of 1000°C. The content of W is 10-40
The weight percentage is appropriate; if it exceeds this range, workability will be extremely poor. The electrical resistivity of the N1-W alloy at 1000'C is approximately 7 .mu..OMEGA. for 10 wt. % W, and approximately 130 .mu..OMEGA..alpha. for 40 wt. % W.

Effects of the Invention Since the cathode structure of the present invention is configured as described above, even if the heater expands due to a rise in temperature, the heater does not sag, and the emitter can always be held at a substantially constant position. . Moreover, not only is it easy to manufacture, but the heater does not suffer from tension or torsional distortion, and the risk of characteristic fluctuations and early disconnection can be eliminated.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a cathode assembly in which the present invention is implemented, Fig. 2 is a cross-sectional view of the same side, Fig. 3 is a diagram showing the direction of expansion of the heater in the cathode assembly as the temperature rises, and Fig. 4 is a diagram of the main body. FIG. 7 is a perspective view of main parts of another embodiment of the invention. 1... Heater, 2... Ribbon-shaped metal piece, 3... Emitter, 4, 5... Current-carrying terminal. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] a heater formed by bending a ribbon-shaped metal piece into a substantially W-shape in its length direction; an electron radiation emitter attached directly or via an insulating layer to the flat top surface of the intermediate portion of the heater;
A cathode assembly for a cathode ray tube, comprising a pair of current-carrying terminals for fixing both ends of the heater.