JPS6053437B2 - How to seal a sheathed heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and a device for sealing an end treatment section of a sheathed heater.

Generally, the end portion of a sheathed heater is sealed to prevent deterioration of electrical insulation due to moisture absorption of the insulating powder inside, but conventionally, as shown in FIG. 2, and is further equipped with a heating wire 4 connected to a terminal bar 3, and a glass material 5 is loaded into the terminal portion, and the terminal portion is heated to melt the glass material and the terminal portion is sealed. was.

However, according to this sealing method, when the glass material 5 is heated and melted, the temperature of the entire sheathed heater rises, and the gas contained in the gaps between the insulating powders 2 expands and blows out of the sheathed heater. After that, the inside of the sheathed heater becomes depressurized.

This reduced pressure reduces the dielectric strength between the metal tube 1, the heating wire 4, and the terminal bar 3. For example, if the outside pressure is 2731 (1 atm), and the average temperature rise of the sheathed heater during sealing is 5.
Considering 46X, the pressure of the gas inside after being sealed is 0.
．． The pressure becomes 5 atmospheres. Also, this blowing out of gas takes time due to the resistance of the insulating powder 2, so it continues for a while.
For this reason, gas bubbles 6 are generated within the glass material 5, as shown in FIG. Therefore, not only does it take time to finish the seal as shown in Figure 1, but bubbles are difficult to form in glass with high viscosity and remain inside the glass, reducing the strength of the glass and causing incomplete sealing. There were some flaws that made me get used to it. The present invention eliminates the above-mentioned conventional drawbacks,
An embodiment of the present invention will be described below with reference to FIG.

In the figure, 11 is a metal tube constituting the exterior of the sheathed heater, 12 is an insulating powder densely packed inside the metal tube 11, 13 is a terminal rod connected to a heating wire 14 located inside the metal tube 11, and 15 is a metal tube. A heating sealing material made of glass or the like is used to seal the unopened end of the tube 11. Reference numeral 16 denotes a cooling device in which a water-cooled tube 17 is positioned approximately 2C77Z lower than the upper surface of the insulating powder 12. It cools only the vicinity of the terminal part. Reference numeral 18 denotes a heating device consisting of an induction heating coil or the like that heats the end portion of the metal tube 11.

The parts of the metal tube 11 other than the cooling part and the heating part are kept at room temperature. In the above configuration, when sealing is performed, the heating sealing material 15 is first loaded into the open end of the metal tube 11 housing the insulating powder 12 and the heating wire 14 connected to the terminal bar 13.

Next, the outside of the metal tube 11 is cooled by the cooling device 16, and the end portion of the metal tube 11 is heated by the heating device 18, and the heating sealing material 15 is melted to seal the end portion. According to this sealing method, the area where the temperature of the gas inside the insulating powder 12 increases is limited and most of the area is kept at room temperature.
The amount of gas blown out is small. Therefore, the decompression is so small that it can be ignored. In the same sheathed heater, the dielectric strength voltages of the metal tube 11, the terminal bar 13, and the heating wire 14 were measured in the case of sealing without cooling and in the case of sealing after cooling. As a result, the former had a breakdown voltage of 1000V, while the latter had a withstand voltage of 2000V or more. As is clear from the above explanation, according to the present invention, the area where the temperature of the gas inside the insulating powder rises is limited and most of it is kept at room temperature, so the amount of gas blown out is small and the depressurization is so small that it can be ignored. Therefore, the dielectric strength can be improved.

In addition, the time for blowing out the gas is short, so by the time the end portion is closed with the heated sealing material, the blowing out of the gas has finished and no bubbles are generated. A very good seal without bubbles can be obtained in a short period of time.
This method can also be applied to sealing by metal brazing or bonding using metallized ceramics, hermetic seals, etc. Furthermore, the sealing device is extremely simple and can be provided at low cost, which provides excellent effects.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the end of a sheathed heater showing a conventional sealing method, Fig. 2 is a cross-sectional view showing how bubbles are generated when sealing is performed using the same method, and Fig. 3 shows an embodiment of the present invention. FIG. 11... Metal tube, 12... Insulating powder, 15... Heat sealing material, 16... Cooling device,
18... Heating device.

Claims (1)

[Claims] 1. A heating sealing material is loaded into the end portion of a metal tube filled with insulating powder, and a cooling means is used to cool only the vicinity of the end portion, and the end portion is heated. A method for sealing a sheathed heater, characterized by melting a sealing material and sealing. 2. A heating device that heats the end portion of a metal tube loaded with a heat sealing material, and a cooling device that is located below the heating device and cools only the vicinity of the end portion of the metal tube. A sealing device for sheathed heaters.