JP2753295B2 - Manufacturing method of cathode for electron tube - Google Patents

Description

The present invention relates to a method for manufacturing a cathode for an electron tube, and more particularly to a method for welding a heater and a heater support.

[Conventional technology]

As the cathode structure for an electron tube, an indirectly heated cathode structure as shown in FIG. 3 is widely used.

The cathode assembly has a base 2 provided with a thermoelectron emitting substance 1 on a top, a cylindrical sleeve 3 fitted to the base 2, and a disk 4 fitted and held on the sleeve 3, and the bottom of the sleeve 3 is slightly And the cathode heater 5 is inserted with the gap A.

In such a cathode assembly, the gap A between the bottom of the sleeve 3 and the heater 5 greatly affects the heater characteristics.
If the gap A is large, the heat transfer to the thermionic emission material 1 becomes worse. In particular, in the case of a color picture tube having three electron guns,
If the gaps A are not kept constant, the heater characteristics become non-uniform, the transient rise in cathode temperature after switching becomes non-uniform, the white balance becomes poor, and the image quality is significantly degraded. .

Therefore, it is necessary to always maintain the gap A with high accuracy and constant. Usually, the heater 5 is welded to the heater support 6 to obtain a heater assembly 7, and then the heater assembly 7 is inserted into the sleeve 3, and the sleeve 3 and the heater assembly 7
Since the method of setting the gap A from the related position is performed, the accuracy of the length l of the heater structure 7 becomes important, and therefore, it is particularly required to improve the welding accuracy of the heater 5 and the heater support 6. Will be done.

FIG. 4 shows a side view of a main part of a conventional apparatus for welding the heater 5 and the heater support 6 by a resistance welding method, wherein 8 is an upper electrode, 9 is a lower electrode provided opposite to the upper electrode, and 10 is a lower electrode. The heater support 6 is placed on the lower electrode 9 that is inclined with respect to the direction of gravity on the support stand for positioning, and is locked to the stopper 11. Next, the lead 5a is overlapped on the heater support 6, and the heater 5 is positioned by bringing the head 5b of the heater into contact with the support base 10. Thereafter, the upper electrode 8 is pressed against the lead part 5a, and the two parts 5a and 6 are welded to form a predetermined length l.
(Japanese Patent Application Laid-Open No. 51-5056)
No. 5).

[Problems to be solved by the invention]

According to the above-described conventional method, the positioning of the heater 5 and the heater support 6 can be easily performed.
And the heater support 6 are easily welded, and the heater structure 7 having a predetermined length can be efficiently manufactured.

However, the lead portion 5a of the heater is usually formed into a core coil shape mainly composed of tungsten (W).
Is poor, and the top 5b of the heater 5 may not be in good contact with the support base 10 due to its own weight, so that the positioning accuracy of the heater 5 may be reduced.

When the upper electrode 8 is pressed against the lead portion 5a,
The lead portion 5a may be deformed or laterally displaced, so that accurate welding may not be obtained or welding may be insufficient.

An object of the present invention is to provide a welding method capable of welding a heater and a heater support with high accuracy and efficiency in view of the above-mentioned conventional problems.

[Means for solving the problem]

An object of the present invention is to provide a method for manufacturing a cathode for an electron tube in which a cathode heater and a heater support are sandwiched between electrodes arranged opposite to each other and joined by resistance welding. A heater support is attached to the electrode surface of one of the electrodes, and the lead and top of the heater are placed on the other electrode and the positioning support, respectively. This is achieved by blowing the active gas to bring the top of the heater into contact with the reference surface of the support base, and then pressing the two electrodes and resistance welding the heater and the heater support.

[Action]

By blowing the gas, the top of the heater can be reliably moved and brought into contact with the reference surface of the support table, so that the heater can be positioned with high accuracy. Therefore, the heater and the heater support can be accurately welded.

〔Example〕

An embodiment according to the present invention will be described below with reference to FIG.

FIG. 1 is a side view of a main part of an apparatus for practicing the present invention, and 12 is a lower electrode provided so as to be movable left and right on an electrode guide 13.
Numeral 14 denotes an upper electrode provided so as to be movable up and down via an arm 15 by a driving device (not shown). The electrodes 12 and 14 are provided to face each other with the electrode surfaces inclined at 5 to 20 degrees with respect to the horizontal direction. Have been.

Reference numeral 16 denotes a positioning support for positioning the heater 5 by placing the top 5a of the heater 5 on the reference surface 17 and positioning the heater 5; reference numeral 18 denotes a gas flow path provided on the upper electrode 14 side; It is provided so as to be inclined toward 17 so that the inert gas 19 is strongly blown to the lead portion 5a from an oblique direction.

Using such a device, first, the heater support 6 is attached to a predetermined position on the electrode surface of the upper electrode 14, and the lead portion 5a is placed on the lower electrode 12 as shown in FIG. When the lead portion 5a is strongly blown, the heater 5 is moved in the direction of the reference surface 17, and the top portion 5b is securely brought into contact with the reference surface 17, and is positioned with high accuracy on the lower electrode 12.

Next, in this state, the upper electrode 14 is lowered, the lead portion 5a and the heater support 6 are overlapped and pressed, and resistance welding is performed.

As the inert gas 19 blown to the lead portion 5a, a gas such as argon or nitrogen that does not cause a chemical change in the welded portion and the electrodes 12, 14 is used.

Further, if the lower electrode 12 is slid over the electrode guide 13 and the two lead portions 5a are alternately welded one by one, compared to the case where two lead portions are welded simultaneously, Since electric power at the time of welding can be halved, fluctuations in the power supply are reduced, and stable welding can be performed.

Next, as shown in FIG. 2, a groove 20 is provided on the electrode surface of the lower electrode 12, and the lead 5a is disposed in the groove 20, so that the lead 5a is not deformed or laterally displaced. Accurate welding can be stably performed.

The depth of the groove 20 is such that the lead 5a sufficiently appears on the electrode surface. For example, it is sufficient that the depth is about two-thirds of the outer diameter of the lead.

〔The invention's effect〕

According to the present invention described above, since the heater can be positioned with high accuracy, the heater can be welded to the heater support with high accuracy. For example, when the resistance value of the heater manufactured according to the present invention is measured at room temperature and the welding accuracy is confirmed from the difference between the measured value and the reference value, the difference between the resistance value and the reference value is within about 3%. As a result, it is possible to achieve a large improvement compared to the conventional 10%, and high-precision welding has become possible.

As a result, a heater assembly of a fixed length can be obtained with high accuracy, and a cathode having uniform heater characteristics can be manufactured. If the cathode is applied to an electron gun of a color picture tube, the effect of improving image quality can be reduced. is there.

[Brief description of the drawings]

FIG. 1 is a side view of a main part according to an embodiment of an apparatus for practicing the present invention, FIG.
FIG. 3 is a sectional view of an essential part of the indirectly heated cathode structure, and FIG. 4 is a side view of the essential part for explaining a conventional method of welding a cathode heater and a heater support by a resistance welding method. 5 ... heater, 5a ... lead part, 5b ... top part, 6 ... heater support, 7 ... heater structure, 8 ... upper electrode, 9 ... lower electrode, 10 ... support base, 12 ... Lower electrode, 13: Electrode guide, 14: Upper electrode, 16: Positioning support, 17: Reference surface, 18: Gas flow path, 19: Inert gas, 20: Groove.

Claims (2)

(57) [Claims] 1. A method for manufacturing a cathode for an electron tube in which a cathode heater and a heater support are sandwiched between electrodes arranged opposite to each other and joined by resistance welding, the electrodes arranged opposite to each other are inclined with respect to a horizontal direction. A heater support is attached to one electrode, and a lead portion and a top portion of the heater are placed on the other electrode and the positioning support, respectively. Then, an inert gas is supplied to the lead portion from the one electrode side. A method for manufacturing a cathode for an electron tube, comprising spraying the heater so that the top of the heater is in contact with a reference surface of the support base, and then pressing both the electrodes to perform resistance welding between the heater and the heater support. 2. A method for manufacturing a cathode for an electron tube according to claim 1, wherein a groove is provided in said other electrode, and said lead is disposed in said groove.