JPH0128621Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a cathode assembly used in a cathode ray tube electron gun, and in particular improves the insulation between the cathodes and the first control electrode, or when a plurality of cathodes are arranged on the same plane. The present invention relates to improvements in cathode structures for the purpose of

Figure 1 shows a cathode structure 1 commonly used in the past.
FIG. 3 is a partial cross-sectional view including the first control electrode showing 0;
The cathode cylinder 13, which is a cap-shaped cylinder with a thermionic emissive material layer deposited on the top, is caulked to an insulating stone 11 made of ceramic such as alumina or steatite.
The lower end portion is welded and fixed to the outer cathode support cylinder 12 which is fixed by caulking or the like at 12B. The insulating stone 11 that supported the cathode tube 13 is placed inside the first control electrode 14 which is a bottomed cylindrical shape with a through hole in the closed surface, and the upper surface position of the insulating stone 11 is regulated by a spacer 15, and the lower surface thereof is regulated by a spacer 15. The stator 16 is pressed into contact with the first control electrode 14, and the stator 16 is welded to the side surface of the first control electrode 14 to be supported and fixed. At this time, the height of the spacer 15 is selected so that the difference in distance between the top of the cathode tube 13 and the upper surface of the insulating stone 11 with respect to the closed surface of the first control electrode 14 becomes a predetermined value.

Normally, a groove 11A surrounding the outer cathode support tube 12 is bored in the upper surface of the insulating stone 11 on the electron emitting surface side of the cathode tube 13. This is the cathode tube 1 during cathode ray tube operation.
The metal Ba that is reduced and produced from the electron emitting surface at the top of the cathode is evaporated by the heat of the heating wire inserted into the cathode cylinder 13 and the first control electrode even if this evaporated substance adheres to the upper surface 11B of the insulating stone 11. In order to prevent the insulation between the cathode 14 from deteriorating, a blind spot is created within the angle from which the groove 11A is viewed from the top of the cathode.

However, in the method of forming a blind spot for evaporated matter from the top of the cathode using the groove 11A described above, the deeper the groove 11A is, the more the groove 11A is required to improve the insulation between the cathode tube 13 and the first control electrode 14. The narrower the width, the better, but the thickness of the insulating stone 11 is usually about 1 to 2 mm, and if the width is made too deep, the mechanical strength of the insulating stone will be impaired. This makes it difficult to form the groove when forming the groove, making it impossible to obtain a necessary and sufficient blind spot. In particular, in cathode assemblies used in narrow electron guns for cathode ray tubes, the overall dimensions are reduced, and the annular groove 11A is formed in the insulating stone 11.
There is no dimensional margin to drill the grooves 11A, and it becomes extremely difficult to process the extrusion mold of the insulating stone 11 that forms the grooves 11A. Furthermore, when pressing the insulating stone, it is difficult to form a mold, the precision is poor, and due to dimensional constraints, it is impossible to obtain an effective blind spot.

The present invention eliminates the above-mentioned drawbacks, and the lower ends of one or more cap-shaped cathode tubes each having a thermionic emissive material layer deposited on the top are fixed to an insulating stone by welding.
In a cathode assembly equipped with two or more outer cathode support tubes, the caulked portion of the outer cathode support tubes on the upper surface of the insulating stone facing the top of the cathode tubes is formed to surround each outer cathode support tube. To provide a cathode ray tube cathode structure in which an annular metal plate is inserted to cover one or more annular grooves except for a part of the outside thereof, and the upper part of an outer cathode support cylinder is fixed.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows a side cross-sectional view including the first control electrode of a cathode assembly 20 based on an embodiment of the present invention, and for the sake of simplicity, the same parts as in the prior art are given the same reference numerals as in FIG. 1. Put on.

The caulked portion 12A of the outer cathode support tube 12 on the upper surface of the insulating stone 11 facing the top side of the cathode tube 13 is provided with an annular metal plate having an opening that fits into the outer diameter of the outer cathode support tube 12. 21, and the outer cathode support cylinder 12 is attached to the caulked edges 12A, 12B as in the conventional case.
It is caulked and fixed to the insulating stone 11. The outer diameter of the annular metal plate 21 is equal to the annular groove 1 formed on the upper surface 11B of the insulating stone 11 so as to surround the outer cathode support cylinder 12.
The size is chosen to cover the outside of 1A with approximately 0.1 to 0.2 mm left. A cap-shaped cathode tube 13 whose top part is covered with a thermionic emission material layer is welded and fixed at the lower end of the outer cathode support tube 12, and an insulating stone 11 supporting and fixing the cathode tube 13 is placed inside the first control electrode 14. Spacer 15
The position of the upper surface 11B is regulated, and the lower surface is supported and fixed to the first control electrode 14 by the stator 16.

According to the embodiment of the present invention, the annular groove 11A is for preventing insulation deterioration between the outer cathode support tube 12 and the first control electrode 14 due to deposition of evaporated matter from the top of the cathode tube 13.
Most of the groove is covered with the annular metal plate 21, so even if the annular groove 11A alone does not have enough width and depth to provide a sufficient blind spot against evaporative accretion,
A complete blind spot is obtained by the annular metal plate 21, and the groove can be deepened at the expense of the strength and workability of the insulating stone 11.
There is no need to narrow it down. Alternatively, there is little dimensional margin to form the necessary and sufficient annular groove 11A in the insulating stone 11, especially when the cathode structure 20 is downsized.
If the present invention is applied, the annular groove 11A does not need to have an insufficient size, so that mold processing and manufacturing thereof become extremely easy.

In addition, the metal Ba generated by reduction from the top of the cathode tube 13 during operation of the cathode ray tube not only accretes linearly at a certain angle onto the upper surface of the insulating stone 11, but also collides with residual gas molecules in the tube and scatters, causing the insulation to deteriorate. Although some objects accrete perpendicularly to the upper surface of the stone 11, this embodiment can form a sufficient blind spot even for these objects. Alternatively, in an in-line cathode structure 30 in which three cathode cylinders 13 are arranged in-line in the same plane and fixed to an insulating stone 31 as shown in FIG. Evaporated matter is deposited from the cathode tube 13, and the conventional annular groove 31A alone cannot provide a sufficient blind spot. However, since the outer cathode support cylinder 12 is fixed by inserting the annular metal plates 21 according to the present invention into the upper caulking portions, the insulation between adjacent cathodes does not deteriorate.

Furthermore, since the annular metal plate 21 made of metal is inserted into the caulking portion of the outer cathode support cylinder 12 and caulked, the two fit into each other at the caulking edge 12A, and the annular metal plate 21 plays the role of an elastic material. Since the caulking is done by pressure contact, the caulking strength is dramatically improved, and the outer cathode support tube 12 is
Thermal changes over time, which would cause looseness in the caulked part due to thermal expansion, are prevented, and extremely stable cathode characteristics can be obtained.

In the above description, the method of fixing the outer cathode support cylinder 12 and the annular metal plate 21 to the insulating stone 11 was described as caulking, but the method is not limited to this, and for example, adhesive fixing using a glass material may be used. Needless to say.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view including a first control electrode showing a conventionally used cathode structure; FIG. 2 is a cross-sectional view including a first control electrode showing a cathode structure according to an embodiment of the present invention; The figure shows a cross-sectional view of an in-line cathode structure according to another embodiment of the present invention. 10, 20, 30... cathode structure, 11, 31...
...Insulating stone, 11A, 31A...Annular groove, 12...
Outer cathode support tube, 13... Cap-shaped cathode tube, 14...
First control electrode, 15... spacer, 16... stator, 21... annular metal plate.

Claims (1)

[Scope of utility model registration request] In a cathode assembly, the lower end of a cap-shaped cathode tube, the top of which is coated with a thermionic emissive material layer, is fixed by welding, and an outer cathode support tube is fixed to an insulating stone, on the top side of the cathode tube. An annular groove is formed in the facing upper surface of the insulating stone so as to surround the outer cathode support cylinder, and an annular metal plate covering the annular groove except for a part of the outer side is provided at the fixed part of the outer cathode support cylinder. A cathode assembly for a cathode ray tube, characterized in that: