JPH0340331A - Impregnated cathode structure - Google Patents

Abstract

PURPOSE:To enhance the quality and producibility by embedding the outer edges of high melting point metal thin wires, which are stretched radially from an impregnated cathode, in a cathode supporting table of metal having a lower melting point than the metal thin wires and in a welding nugget with a metal fitting having a lower melting point than the metal thin wires. CONSTITUTION:The outer edges of a plurality of high melting point metal thin wires 11 stretched radially from an impregnated cathode 5 are secured to the top of a cylindrical metal cathode supporting table 8 of a cathode holder 7, and these outer edges are embedded in a welding nugget 13, which is obtained by welding this supporting table 8 to a cylindrical metal fitting 12 installed on its outside circumference and is produced through this welding. The thin wires 11 intersect cruciform and, at this intersection, are welded previously between a metal cup 2 and a metal sleeve 3. In the process of fitting the metal fitting 12 on the outside circumference of the cathode supporting table 8, the outer edges of the thin wires 11 are fitted between these two members followed by laser welding in the direction of arrow, and now the metal fitting 12 and cathode supporting table 8 are partially melted to produce a welding nugget 13, in which the outer edges of the thin wires 112 are embedded.

Description

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

Conventional technology In general, the operating temperature of an impregnated cathode is between 1,000 and 1.10
The temperature is as high as 0°C, and can exceed 1,200°C during the cathode activation process. For this reason, a high melting point metal thin wire made of tungsten, molybdenum, an alloy thereof, or the like is used to support and fix the impregnated cathode.

In the conventional impregnated cathode assembly shown in FIG. 4, a metal cup 2 containing a pellet-shaped impregnated emitter 1 is housed in a metal sleeve 3 welded to its bottom plate and inside the metal sleeve 3. An impregnated cathode 5 is formed together with the impregnated heater 4, and the outer edge of a high melting point metal fine wire 6 radially extending from the impregnated cathode 5 is welded to a metal cathode support 8 of a cathode holder 7. . The cathode holder 7 has a ceramic insulating ring 9 for insulatingly supporting a cylindrical cathode support 8, and also has a metal cylinder 10, which is fixed within a cup-shaped control grid electrode (not shown). Ru.

The cathode support 8 is made of Kovar (Fe-Ni-C0 alloy), which has a melting point lower than that of the thin metal wire 6, and the outer edge of the thin metal wire 6 is resistance welded (spot welded) to the cathode support 8. or laser welded.

Problems to be Solved by the Invention However, since the metal wire (made of a metal with a higher melting point) is welded, the welding is not easy and the reproducibility and stability are very poor.Especially in the case of resistance welding, the sparks generated during welding cause the metal to melt. It is easy to melt the thin wire or cause embrittlement near the welding point, reducing mechanical strength.Also, when laser welding is applied, the outer edge of the thin metal wire when irradiated with the laser beam is attached to the surface of the cathode support. Since it is difficult to make the thin metal wire adhere to the metal wire, the temperature of the thin metal wire, especially at the outer edge, becomes abnormally high, further increasing the risk of melting and embrittlement.

Means for Solving the Problems In the present invention, the outer edge of a high-melting point metal thin wire extending radially from an impregnated cathode is connected to a metal cathode support having a melting point lower than that of the metal thin wire, and a metal cathode support having a lower melting point than the metal thin wire. The material is embedded in a welding nugget with a fixing metal fitting having a low melting point.

Function: Because of this configuration, the thin metal wire is not fixed to the cathode support by direct welding of the two, and the outer edge of the thin metal wire is protected by being sandwiched between the cathode support and the fixing fittings. It is heated and fixed with good heat conduction. Furthermore, the humidity of the thin metal wire during welding does not exceed the respective melting points of the fixing fitting and the cathode support, and the outer edge of the thin metal wire is embedded in the weld nugget produced during this welding. Regardless of whether resistance welding or laser welding is applied, it is firmly fixed to the cathode support without fusion or embrittlement.

Embodiments Next, the present invention will be explained along with embodiments shown in the drawings.

The structure shown in FIGS. 1 and 2 is different from the conventional structure shown in FIG. 7 is fixed to the upper end of a cylindrical metal cathode support 8, and this fixation is obtained by welding the cathode support 8 and a cylindrical fixing fitting 12 provided on its outer peripheral surface, The only difference is that the outer edge of the thin metal wire 11 is embedded in the weld nugget 13 produced by this welding, and the other configurations are unchanged.

The thin metal wire 11 with a high melting point is made of a round wire of tungsten-rhenium alloy with a diameter of about 0.05M, and its melting point is about 3.
The temperature is 100°C. On the other hand, the cathode support 8 is made of Kovar and is formed into a cylindrical shape with an outer diameter of 3.5 mm and a wall thickness of 0.2 mm, and its melting point is approximately 1.450°C. In addition, the fixing fittings 12 are made of stainless steel and have an inner diameter of 3.6 cm.
It is formed into a cylindrical shape with a wall thickness of 0.15 m5, and its melting point is about 1.450° C., which is almost the same as the melting point of the cathode support 8.

In the illustrated example, two thin metal wires 11 are made by crossing each other in a cross, and at the cross intersection, the metal cup 2 and the metal sleeve 3 are connected to each other.
It is pre-welded between the As shown in FIG. 2, in the process of fitting the fixing fitting 12 onto the outer peripheral surface of the cathode support 8, the outer edge of the thin metal wire 11 is fitted between the two. Then, when laser welding is performed in the direction of the illustrated arrow, the fixing metal fitting 12 and the cathode support 8 are partially melted to form a welding nugget 13, and the outer edge of the thin metal wire 11 is formed in the welding nugget 13. is embedded.

A YAG laser is most suitable for laser welding, and when the fixing fitting 12 and the cathode support 8 are partially melted by irradiating beam light with a beam diameter of 0, 4 vm = 0, 6 mm, a fine metal wire is formed. A preferred weld nugget 13 with a diameter of about 0.3 mm could be obtained without damaging the weld nugget 11.

In this embodiment, the distance between the fixing fitting 12 and the cathode support 8 is 0.05-, which is equivalent to the wire diameter of the thin metal wire 11, but the upper limit of the distance is 2 times the wall thickness of the fixing fitting 12. one part
It is permissible up to 0.075 nwa or less. Further, resistance welding may be applied instead of laser welding, but in this case, the fixing fitting 12, the thin metal wire 11, and the cathode support 8 must be in close contact with each other. However, if the pressing pressure of the welding electrode is appropriately increased, a good welding effect can be obtained due to the elastic deformation of the fixing fitting 12 even without negative fitting.

The thin metal wire 11 is not limited to a round wire, but may be a ribbon-like wire. As the material for the fixing fittings 12 and the cathode support 8, it is preferable to use a Fe--Ni alloy having a melting point of about 1.500 DEG C. or lower, such as Kovar or stainless steel.

FIG. 3 shows another embodiment of the invention. In this case, the outer end edge of the thin metal wire 11 is fixed onto the top surface of the cathode support 8 using a flat annular fixing fitting 12a. In this case too,
A thin metal wire 11 is attached to the fixing fitting 12a and the cathode support 8.
The outer edge of the thin metal wire 111 is embedded in a weld nugget created between the two by laser welding or resistance welding.

Effects of the Invention Since the present invention is constructed as described above, the outer edge of the high melting point metal fine wire for supporting the impregnated cathode is fixed to the cathode support without damage, reliably and with good reproducibility, resulting in improved quality. and productivity can both be improved.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of an impregnated cathode assembly according to the present invention before welding, FIG. 2 is a partially cutaway perspective view of the same cathode assembly, and FIG. 3 is a side sectional view of another embodiment of the present invention. FIG. 4 is a side sectional view of a conventional impregnated cathode structure. 5... Impregnated cathode, 7... Cathode holder, 8... Cathode support stand, 11... Thin metal wire, 12.12a...・Fixing metal fittings, 13...
...Welding nuggets.

Claims (1)

[Claims] A welding nugget of a metal cathode support base in which the outer edge of a high-melting point thin metal wire extending radially from an impregnated cathode has a melting point lower than that of the thin metal wire, and a fixing fitting having a melting point lower than that of the thin metal wire. An impregnated cathode structure characterized by being embedded in the cathode structure.