JPS5812280A - Sheathed heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheathed heater, and particularly to sealing an opening at the end of a pipe.

Conventionally, the pipe end opening of a sheathed heater was completely sealed with glass to block moisture absorption of the electrical insulating powder inside the pipe and maintain a high insulation resistance value. However, in such a sheathed heater sealed with glass, the glass breaks when subjected to impact, and the effect of blocking moisture absorption cannot be expected, so care must be taken when handling it. Also,
When this sheathed heater is used at high temperatures, the oxygen in the pipe reacts with the heating wire and is consumed, causing the pressure inside the pipe to drop significantly, which causes the metal components of the heating wire to be liberated, shortening its life. However, there were drawbacks such as deterioration of withstand voltage.

The present invention solves the above-mentioned drawbacks of the conventional sheathed heater, and embodiments of the present invention will be described below with reference to the accompanying drawings.

In Figures 1 and 2, 1 is a metal pipe, 2 is a coiled heating wire inserted into the pipe 1, 3 is a terminal bar connected to both ends of the heating wire 2, and 4 is a coil filled in the pipe 1. It is an electrically insulating powder such as magnesia. 5 is an insulating sealing material made of silicone rubber; 6 is high vacuum grease for sealing between the sealing material 5 and the pipe 1 and between the sealing material 6 and the terminal bar 3; 7 is sealing the end opening of the pipe 1; It is a polytrifluoroethylene resin film. In the embodiment shown in FIG. 1, the end opening of the pipe 1 is sealed with a sealing material 6, then filled with high vacuum grease 6, and further sealed with a polytrifluoroethylene resin film 7. In the embodiment shown in FIG. 2, the opening at the end of the pipe 1 is sealed with a polytrifluoroethylene resin film 7, followed by filling with high vacuum grease 6 and sealing with a sealing material 5. .

In the configuration described above, the polytrifluoroethylene resin film 7 blocks moisture but has the property of transmitting only oxygen, nitrogen, etc., so that the electrical insulating powder 4 does not absorb external moisture and is insulated. Deterioration of the resistance can be prevented. Furthermore, even if the heating wire 2 and the gas in the pipe 1 react and the gas in the pipe 1 is consumed, the gas is supplied from the outside through the polytrifluoroethylene resin film 7, so that the inside of the pipe 1 remains under reduced pressure. Therefore, the metal components of the heating wire 2 can be prevented from being released. Therefore, even when used at high temperatures, it has a long life and maintains high insulation resistance.

As is clear from the above description, in the sheathed heater of the present invention, the end opening of the pipe is sealed using a polytrifluoroethylene resin film, which prevents the electrical insulating powder from absorbing moisture and reduces the pressure inside the pipe. It has a long life, high insulation resistance, and has great industrial value.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a main part of a sheathed heater showing one embodiment of the present invention, and FIG. 2 is a sectional view of a main part of a sheathed heater showing another embodiment of the invention. 1...Pipe, 7...Polytrifluoroethylene resin film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 1 Figure 2

Claims (1)

[Claims] A sheathed heater made by sealing the end opening of a pipe with a polytrifluoroethylene resin film.