JPH03274635A - Manufacture of directly heated cathode - Google Patents

Abstract

PURPOSE:To prevent short circuit between a wire portion and a control electrode by tensilely fixing preset one of a group of heaters to cut off the wire portion, which is projected outside of leads, by means of electric spark. CONSTITUTION:For a coil heater 3a, preset one of a group of heaters is tensilely fixed and a wire portion 3b which is projected outside of leads 1a, 1b beyond fixed positions is cut off. At this time, the leads 1a, 1b to which the heater 3a is tensilely stuck are positioned depending on lower electrodes 6a, 6b. An upper electrode 5 is put in contact with the bottom of the heater wire portion 3b which is left outside of the leads 1a, 1b to turn a switch 8 on. Then, small electric spark is generated between the tip of the electrode 5 and the wire portion 3b to cut off the wire portion 3b from the bottom. As a result, there is no projection of the wire portion 3b and therefore no short circuit between the wire portion 3b and the electrodes 6a, 6b, and so a good directly heated cathode can be obtained.

Description

[Detailed description of the invention] The fox is standing on the top of the river The present invention relates to a method for manufacturing a cathode assembly for a cathode ray tube.

In particular, the present invention relates to a method of manufacturing a directly heated cathode suitable for assembling a filament heater of a viewfinder cathode ray tube.

A conventional method for manufacturing a directly heated cathode will be described with reference to the drawings.

FIG. 2 shows a sectional view of a directly heated cathode in the manufacturing process according to the prior art, and FIG. 3 shows a sectional view of a completed product of the directly heated cathode according to the prior art. In the figure, la.

1b is a lead for fixing the heater under tension, 2 is an insulator that supports the lead, 3a is a coil type heater, 3b is a heater wire left after the heater 3a is assembled and installed, and 4 is an electron emitting substance.

In the conventional manufacturing method, after attaching the heater 3a, the heater wire 3b was removed using tweezers or the like. After this,
The electron emitting material 4 is fixed by a spraying method or the like.

By the way, as mentioned above, after the heater 3 is attached to the leads 1a and 1b by welding or the like, it requires skill in the work to completely remove the heater wire 3b using a bin set or the like. must spend time. In addition, there was a problem in that the material that was not sufficiently removed caused a short circuit with the control electrode.

Therefore, the present invention has been proposed to eliminate these drawbacks, and its object is to provide a new and improved method for manufacturing a directly heated cathode.

In order to solve the above-mentioned problem, this invention No. 1 is characterized in that after a coil type heater is stretched and fixed to a lead-out lead, unnecessary wire portions of the heater are cut and removed using an electric spark.

According to the existing and above manufacturing method, the excess heater wire extending outside the lead is reliably removed. Therefore, it is possible to prevent the wire portion from being left behind due to insufficient removal.

Furthermore, the delicate and skilled work of removal using a bottle set or the like, which was done in the past, is simplified so that anyone can do it.

supporter The present invention will be explained below with reference to the drawings.

FIG. 1 is an embodiment showing the removal of the heater wire portion of a directly heated cathode according to the present invention, and is a cross-sectional view of the process of cutting and removing the heater wire portion remaining outside the lead immediately after the heater is stretched using an electric spark. It is. In the directly heated cathode structure, the same parts as in FIGS. 2 and 3 are designated by the same reference numerals, and the explanation thereof will be omitted. In the figure, 5 is an upper electrode for cutting used in the method of the present invention, 6 is a lower electrode, 7 is a power source, and 8 is a switch for turning the power on and off.

Next, the operation of cutting and removing the heater wire portion using electric spark will be described. As shown in the figure, the heater 3a is stretched and fixed, and the lower electrode 6
a, f3b, lower electrode Efa, 6b
is connected in series with an upper electrode 5 whose tip diameter is sharpened to 0.1 mm or less via a power supply 7 and a switch 8 which is normally set to the OFF state. When the upper electrode 5 is brought into contact with the base of the heater wire portion 3b remaining outside the lead and the switch 8 is turned on at this time, the tip of the upper electrode 5 and the ear portion 3
A minute electrical spark is generated between the At the same time, the heater wire portion 3b is cut from the root. At this time, the power source 7 may be a DC power source or an AC power source that provides a potential difference of 3 to 5 V between the upper electrode 5 and the lower electrodes 8a, 6b. Specifically, it is sufficient to set the current during cutting to 1 to 2 A. The upper electrode 5 is preferably a tungsten rod or a molybdenum rod.

According to this embodiment, the heater wire portion can be instantly cut and removed without precision work.

As explained above, the present invention provides a step of cutting off the heater wire portion remaining outside the lead by using an electric spark, so that the heater wire portion is completely removed and is not left behind. Furthermore, short circuit between the wire portion and the control electrode can be reliably prevented.

In particular, the time required to cut and remove the heater wire portion is greatly reduced, and there are practical effects such as the need for skill in the work.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the cathode manufacturing method of the present invention, which is a cross-sectional view of the process of cutting and removing the heater wire portion, FIG.
The figure is a cross-sectional view of a completed directly heated cathode. 1 atlb...Lead, 2...Insulator, 3a...Coil type heater, 3b...Heater wire part, 4...Electron emitting material , 5... Upper electrode, 6a, 6b... Lower electrode, 7... Power supply, 8... Switch.

Claims (1)

[Claims] In a method for manufacturing a directly heated cathode in which a coil-type heater is stretched between a pair of leads, a predetermined coil-type heater is stretched and fixed from a series of heater groups, and then the coil-type heater is stretched to the outside of the lead from the fixed position. A method for producing a directly heated cathode, characterized in that the wire portion is removed by a cutting process using an electric spark.