JPH0521296B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a directly heated cathode assembly used in an electron gun of a small cathode ray tube.

BACKGROUND TECHNOLOGY AND PROBLEMS The demand for small cathode ray tubes for use as viewfinders in imaging devices such as television cameras is increasing, and there is a demand for smaller cathode ray tubes with higher performance. It is small and has quick response, suitable for use in such small cathode ray tubes.
In addition, an electron gun equipped with a directly heated cathode that consumes low power has been proposed. An example of a directly heated cathode structure employed in such an electron gun is shown in FIGS. 1 to 3. FIG. 1 shows a directly heated cathode 1, which is a coiled heater formed by winding a heater wire made of tungsten wire or the like with an extremely small heat capacity of, for example, a diameter of about 5 to 10 μm. 2, and a thermionic emitting substance 3, for example, a metal oxide such as (Ba, Ca, Sr)O, etc., is applied by electrodeposition or spraying so as to cover the coiled molded part 2a of the coiled heater 2. It is formed by directly attaching it using a method such as. In this case, the coiled heater 2 is made of a material that also serves as a reducing agent for the thermionic emission material 3 and has high high-temperature strength, high specific resistance, and small coefficient of thermal expansion. is desirable, and from this point of view, tungsten wire or the like is used.

As shown in FIGS. 2 and 3, this directly heated cathode 1 is placed between a pair of cathode support pins 6 and 6' which are planted on an insulating support 5 made of ceramic material or the like having a center hole 4. Then, both ends of the coiled heater 2 are fixed to the upper surfaces of the cathode support pins 6 and 6' by welding or the like.
A so-called directly heated cathode structure 7 is constructed. In this case, the coiled heater 2 is first attached to the cathode support pins 6 and 6', and then the thermionic emitting material 3 is attached to the coiled heater 2 to form the directly heated cathode 1 and the directly heated type cathode 1. The entire cathode structure 7 may be configured. Such a directly heated cathode assembly 7 is extremely small, and to give an example of actual dimensions, for the directly heated cathode 1, the diameter d1 of the tungsten wire forming the coiled heater 2 is
5μm, coil-shaped molded part 2a of coil-shaped heater 2
The coil pitch d2 is 10 μm, the diameter d3 is 50 μm,
The length S1 is 0.75 mm, and this coiled molded part 2
The diameter d4 of the attachment part of the thermionic emitting substance 3 covering a is 60
~70 μm, and the length S2 is 1.0 mm. Further, the diameter d5 of each of the cathode support pins 6 and 6' is 0.3 mm,
The spacing S3 between both cathode support pins 6 and 6' is 1.5 mm.

The directly heated cathode assembly 7 as described above has a very small overall heat capacity and extremely low power consumption.
It has various extremely excellent properties, such as quick response, resistance to deformation of the heater section due to heat, and the fact that the working area of the cathode is minute. However, in the case of such a directly heated cathode assembly 7 manufactured by a conventional method, as shown in FIGS. Cathode support pins 6 at both ends 2b and 2b' of the coiled heater 2 extend in a cubic curve from
The lengths L1 and L1' of the parts 2c and 2c' fixed to the upper surface of the upper surface of the upper surface of the upper surface of the upper surface of the upper surface of
It is said to be relatively large, about 100 μm. For this reason, a directly heated cathode assembly 7 having a coiled heater 2 with a coiled molded part 2a supported through the ends 2b and 2b' extending in the shape of a cubic curve is used in a cathode ray tube. When vibration or shock is applied to the cathode ray tube, the coiled heater 2
A vibration occurs due to the elasticity of b and 2b', which causes noise to appear on the screen of the cathode ray tube. Further, there is a problem that the distance between the coil heater 2 and the first grid provided near the coil heater 2 changes, causing the cut-off voltage to fluctuate. Furthermore, there was a risk that the resistance value of the coiled heater 2 would fluctuate and the cathode temperature would become unstable.

Purpose of the Invention In view of the above, the present invention provides a coil heater that
Both ends of the coil heater are fixed to a pair of cathode support pins, and the coil heater is connected to the coil heater from each of both ends of the coiled molded part. An object of the present invention is to provide a method for manufacturing a directly heated cathode assembly that can effectively shorten the length of each portion fixed to the cathode support pin of the cathode assembly.

SUMMARY OF THE INVENTION A method for manufacturing a directly heated cathode assembly according to the present invention includes fixing both ends of a coiled heater to the center portion of each end face of a pair of cathode support pins by welding or the like, and the heater being firmly attached to the pair of cathode support pins;
After that step, the portion between the portion fixed to the center of the end face of the cathode support pin and the coiled molded portion at each end of the coiled heater that is attached to the pair of cathode support pins. is fixed to the outer periphery of the end surface of the cathode support pin by welding or the like, thereby regulating the displacement of each of both ends of the coiled heater. By doing this, the coiled heater in the direct heating type cathode structure is firmly attached to the pair of cathode support pins, and the coiled heater extends from both ends of the coiled molded part to the pair of cathode support pins. The lengths of the portions each fixed to the pins are made small, and as a result, the shaking of the coiled heater installed between the pair of cathode support pins, which is caused by application of vibration or the like, is reduced.

EXAMPLE Hereinafter, an example of a method for manufacturing a directly heated cathode assembly according to the present invention will be described with reference to FIG. 5 of the drawings.

This example begins with a process of winding and forming a wire forming a heater around a core wire. In this step, as shown in FIG.
The tungsten wire 11 drawn out from 0 is wound tightly in the portion forming the coiled heater 12 so as not to touch each other, and further, the portion forming the coiled heater 12 is spaced apart from each other. Coarsely wind it. here,
For example, molybdenum wire is used as the core wire because molybdenum wire does not form an alloy with tungsten wire and is stable even at high temperatures. FIG. 5B shows an enlarged view of the state in which the tungsten wire 11 is wound around the molybdenum wire 9. For example, the tungsten wire 11 having a diameter of about 5 μm has a diameter d6 of 40 μm.
A coiled heater 12 similar to the coiled heater 2 shown in FIG. 1 is continuously formed by winding the molybdenum wire 9 as a core wire having a length of about 100 m. Next, the molybdenum wire 9 and the coiled heater 12 wound thereon are immersed in an aqueous solution of a mixed acid of nitric acid and sulfuric acid to dissolve and remove the molybdenum wire 9, and then the series of coiled heaters 12 are individually separated. . Each coiled heater 12 obtained in this way is formed of a coiled part 12a formed by tightly winding the tungsten wire 11, and a part formed by loosely winding the tungsten wire 11. The coiled molded portion 12a has end portions 12b and 12b' extending in a cubic curve from both ends.

Next, as shown in FIGS. 6A and 6B, both ends 12b and 12b' of the coiled heater 12 and the third
As shown in the figure, for example, a pair of cylindrical cathode support pins 6 and 6' are aligned with an insulating support 5 made of ceramic material,
For example, one end 12b of the coiled heater 12 is placed on the upper surface of the cathode support pin 6,
In this state, the welding electrode 13 constituting the welding device is lowered to the upper surface of the cathode support pin 6, and the end 12b of the coiled heater 12 is attached to the cathode support pin 6.
Weld and secure it to the center of the top surface. Further, the other end 12b' of the coiled heater 12 is pulled in the direction of the cathode support pin 6' to extend the coiled heater 12, and the end 12b' of the coiled heater 12 is pulled toward the cathode support pin 6'. The welding electrode 13 is lowered to the center of the upper surface of the cathode support pin 6', and the end 12b' of the coiled heater 12 is welded and fixed to the center of the upper surface of the cathode support pin 6'. .
In this case, when the tip of the welding electrode 13 welds both ends 12b and 12b' of the coiled heater 12 to the upper surfaces of each of the cathode support pins 6 and 6', Recesses 6a and 6a' are formed in the center of the upper surface, and these recesses 6
a and 6a', both ends 1 of the coiled heater 12
Fixed parts 12c and 12 in 2b and 12b'
c′ is obtained. In this way, one welding is performed, and the coiled heater 12 is firmly attached to the pair of cathode support pins 6 and 6' which are set up on the insulating support by being installed between them. can do.

Next, as shown in FIGS. 6C and 6D, the fixed portion 12c at the end 12b of the coiled heater 12 on one of the cathode support pins 6 and 6', for example, the upper surface of the cathode support pin 6, and the coiled heater The welding electrode 13 is lowered again to a position between the end 12a of the coiled part 12a of the coiled heater 12, and the part of the end 12b of the coiled heater 12 that is closer to the coiled part 12a than the fixed part 12c is supported as a cathode. It is welded and fixed to the outer periphery of the upper surface of the pin 6 to form a new fixed part 12d. Further, on the upper surface of the cathode support pin 6',
The welding electrode 13 is lowered again to a position between the fixed part 12c' at the end 12b' of the coiled heater 12 and the other end of the coiled formed part 12a, and the fixed part 12b' of the coiled heater 12 is fixed. The part closer to the coiled molded part 12a than the part 12c' is welded and fixed to the outer periphery of the upper surface of the cathode support pin 6' to form a new fixed part 12d'. In this way, by performing the second welding, the displacement of both ends 12b and 12b' of the coiled heater 12 attached to the pair of cathode support pins 6 and 6' is restricted. be exposed. Both ends 12b and 12b' of the coiled heater 12 are
They are fixed to the upper surfaces of the cathode support pins 6 and 6', respectively, with two fixing parts 12c and 12d and 12c' and 12d'.

After that, the coiled molded part 12a of the coiled heater 12 installed between the cathode support pins 6 and 6'
Then, a thermionic emitting material is deposited by vapor deposition or spraying to complete a directly heated cathode structure similar to the directly heated cathode structure 7 shown in FIGS. 2 and 3.

As described above, in the directly heated cathode assembly manufactured based on the method according to the present invention, the coiled heater 12 is heated from each end of the coiled molded part 12a of the coiled heater 12. Cathode support pins 6 and 6' at both ends 12b and 12b', respectively
The lengths L2 and L2' of the fixing portions 12d and 12' to the respective upper surfaces of the cathode structure are shortened compared to the corresponding lengths in a directly heated cathode assembly manufactured by a conventional method.

Next, another example of the method for manufacturing a directly heated cathode assembly according to the present invention will be described with reference to FIG. In this example as well, the coiled heaters 12 are continuously wound around the molybdenum wire that is the core wire, and then the molybdenum wire is melted and removed and the series of coiled heaters 12 are individually separated. Both end portions 12b and 12b' are welded and fixed to the center portions of the upper surfaces of the pair of cathode support pins 6 and 6' that are planted on the insulating support, and this first welding connects the coiled heater 12 to the pair of cathode support pins 6 and 6'. The steps of establishing the cathode support pins 6 and 6' in a rigidly attached state by being bridged between them are performed as described above with reference to FIGS. 5A and B and FIGS. 6A and B. It is carried out in the same way as the process. After the coiled heater 12 is firmly attached to the pair of cathode support pins 6 and 6' through each of the steps described above, the coiled heater 12 is firmly attached to the pair of cathode support pins 6 and 6', as shown in FIGS. 7A and 7B. As shown, the lid body 14, which has a side plate 14a and a notch 14b through which the coiled heater 12 is passed, is placed above the end 12b of the fixed coiled heater 12. Then, it is placed on the upper surface of the cathode support pin 6 so as to cover the entire cathode support pin 6, and the welding electrode 13 is lowered onto this lid 14, and the lid 14 is welded and fixed to the upper surface of the cathode support pin 6. . In FIGS. 7A and 7B, this welding is performed twice, and circular recesses 14c and 14d are formed on the top surface of the lid 14 as traces of the tip of the welding electrode 13, respectively. . By welding the lid 14 to the upper surface of the cathode support pin 6, a portion of the end 12b of the coiled heater 12 closer to the coiled molded part 12a than the fixed part 12c is, for example, below the recess 14c of the cathode support pin 6. It will be fixed to the outer periphery of the upper surface of 6.
Note that in this case, the coil heater 12 is not necessarily
There is no need for the welding electrode 13 to be lowered onto the end 12b.

Further, a lid 14 is also provided on the upper surface of the cathode support pin 6'.
A lid body similar to the above is placed and fixed by welding. Thereafter, a thermoelectron emitting material is attached to the coiled molded portion 12a of the coiled heater 12 installed between the cathode support pins 6 and 6', thereby completing a directly heated cathode assembly.

Even in the directly heated cathode structure obtained in this way, both ends 12b and 1 of the coiled heater 12
Displacement is restricted by the outer periphery of the upper surface of the cathode support pin 6 or 6' for each of 2b',
From each of both ends of the coil-shaped molded part 12a of the coil-shaped heater 12, both ends 12 of the coil-shaped heater 12
The lengths (L3) of the cathode support pins 6 and 6' at b and 12b' to the respective upper surfaces of the fixing portions are shortened. In addition, each cathode support pin 6
and 6′, for example, the lid 14,
It has a side plate 14a and is placed so as to cover the upper part of the cathode support pin 6, so that the tip 12e extending outward of the coiled heater 12 is wrapped therein as shown in FIG. 7A. This can prevent the tip 12e of the coiled heater 12 from coming into contact with other parts.

Effects of the Invention As is clear from the above description, according to the method for manufacturing a directly heated cathode assembly according to the present invention, after both ends of the coiled heater are fixed to the center portions of the upper surfaces of the pair of cathode support pins, Furthermore, the portions between the fixed ends of the coiled heater and the coiled molded part are fixed again to the outer periphery of the upper surface of the cathode support pin, so that the coiled heater is attached to the pair of cathode support pins. It is installed between them and firmly attached, and the displacement of both ends of the coiled heater is restricted by cathode support pins.
The length of the support ends extending from both ends of the coil-formed part of the coil heater and connected to the pair of cathode support pins is effectively shortened. It is possible to obtain a small directly heated cathode structure in which the fluctuation of the coiled heater installed between the pair of cathode support pins is extremely small even when the above-mentioned cathode support pins are applied.
In a cathode ray tube employing a directly heated cathode assembly obtained by the manufacturing method according to the present invention, noise generated on the screen due to vibration is significantly reduced, and the distance between the cathode and the first grit is reduced. By being held constant, the cut-off voltage will be stabilized.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing an example of a directly heated cathode used in a small directly heated cathode structure, and Figures 2 and 3 are directly heated cathodes using the directly heated cathode shown in Figure 1. Plan view and side view showing an example of a cathode structure, No. 4
The figure is a partially enlarged view for explaining the coiled heater part of a directly heated cathode assembly obtained by a conventional manufacturing method, and FIGS. FIG. 7 is a process explanatory diagram for explaining one example. FIG. 7 is a process explanatory diagram for explaining another example of the method for manufacturing a directly heated cathode assembly according to the present invention. In the figure, 6 and 6' are cathode support pins, 12 is a coiled heater, 12a is a coiled molded portion of the coiled heater 12, 12b and 12d' are end portions of the coiled heater 12, and 14 is a lid.

Claims (1)

[Claims] 1. Both ends of a coiled heater are fixed to the center of each end face of a pair of cathode support pins,
a first fixing step in which the coiled heater is attached to the pair of cathode support pins by being installed between them; and after the first fixation step, the coil heater is attached to the pair of cathode support pins At each end of the coiled heater in the state, a portion between the portion fixed to the center portion of the end surface of the cathode support pin and the coiled molded portion is attached to the outer peripheral portion of the end surface of the cathode support pin. A method of manufacturing a directly heated cathode assembly, comprising: a second fixing step of fixing each end of the coiled heater to restrict displacement of each end portion of the coiled heater.