JPS5852311B2 - Sea heater - Google Patents

Description

[Detailed description of the invention] The present invention relates to terminal processing of a sheathed heater.

Generally, the terminal part of a sheathed heater is sealed to prevent electrical insulation from deteriorating due to moisture absorption of the insulating powder inside.
However, conventionally, as shown in Fig. 1, an exterior metal tube 1 is filled with insulating powder 2 such as magneshima powder, and is further equipped with a heating wire 4 connected to a terminal bar 3. As shown in FIG. 2, a cylindrical glass tablet 5 was inserted into the tube 5, the terminal portion was heated to melt the glass tablet 5, the terminal portion was sealed, and the temperature was raised to °C.

However, in a sheathed heater sealed using this glass tablet 5, the gas in the voids contained in the insulating powder 2 in the exterior metal tube 1 expands and slowly flows out from the surface of the insulating powder 20, but the electric current Terminal bar 3 connected to hot wire 4
When the molten glass 5' exerts gravity between the metal tube 10 and the molten glass 5', the expanded gas pushes up the glass 5' and creates bubbles 6 in the glass 5'.

If the viscosity of the glass tube is high, the bubbles 6 may not come out of the glass tube, or some of them may remain in the glass tube 5'.

When large bubbles 6 remain in the glass, not only the mechanical strength of the glass decreases, but also the airtightness tends to be incomplete (and the heat resistance temperature also decreases).

The present invention eliminates the above-mentioned drawbacks of the conventional art, and one embodiment of the present invention will be described below with reference to FIGS. 4 to 6.

First, as shown in Fig. 4, a part of the cylinder is removed from the terminal part of the exterior metal tube 1 that houses the insulating powder 2 and the heating wire 4 connected to the terminal bar 3, as shown in Fig. 5. A glass tablet 7 with a space 8 formed therein is inserted.

The end of this sheathed heater is heated to melt the glass tablet 7 and seal the end.

When this sealed item is closed, the portion having the glass 7' between the terminal bar 3 to which the heating wire 4 is connected and the exterior metal tube 10 is melted and sealed first, as shown in FIG. 4, and then removed. The space 81 in the part where it was removed is not immediately filled up and a space 8' is created (
・Ru.

The expanded gas in the voids contained in the insulating powder 2 in the exterior metal tube 1 easily passes through without passing through the glass 7' (passes through the space 8' and exits to the outside).

At the time when this gas emission stops, the space 8' is
The molten glass 7' is blocked from the bottom by gravity and L.
(.

The size of the space 8' of the removed portion of the cylindrical glass tablet 7 inserted into the end of the sheathed heater in Fig. 5 should be such that the glass tablet 7 has the amount of glass necessary for sealing. L゛.

As mentioned above, when using a glass tablet as shown in Figure 5,
As shown in Figure 6, there are almost no bubbles left in the glass 7', and when the glass used is melted, there are no bubbles regardless of the viscosity of the L and glass T. is obtained.

As is clear from the above description, according to the present invention, no bubbles are formed in the glass, so the mechanical strength of the sealing portion is strong, and the sealing can be airtight with high reliability.

In addition, since the glass has a high viscosity and can be sealed against sunlight, it is possible to easily use glass with a high melting point and high viscosity, and glass that has been difficult to seal until now, such as crystallized glass.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional sheathed heater before sealing, Fig. 2 is a perspective view of the same glass tablet, Fig. 3 is a sectional view of the same after sealing, and Fig. 4 is a sectional view of the glass tablet of the present invention. FIG. 5 is a cross-sectional view of the sheathed heater when it is shipped to Japan, FIG. 5 is a perspective view of the same glass tablet, and FIG. 6 is a cross-sectional view showing the state after the sealed opening. 1...Metal tube, 2...Insulating powder
7...Glass tablet, 8...Space section.

Claims (1)

[Claims] 1. A broken cylindrical glass tablet with a space removed by removing a part of the periphery is inserted into the end of a metal tube filled with insulating powder, and the end is heated to melt and seal the glass tablet. A sheathed heater.