JPS6322438B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheathed heater, and an object thereof is to provide a sheathed heater that is extremely safe during use.

Generally, sheathed heaters are as shown in Figure 1.
A coiled heating wire 2 with terminal rods 1 at both ends is inserted into a metal pipe 3, and the metal pipe 3 is filled with electrical insulating powder 4 such as fused magnesia, fused silica, fused alumina, etc. Both ends of the metal pipe 3 are sealed with glass 5 or heat-resistant resin 6 as required.

This sheathed heater has been rapidly used as a heating component due to its excellent performance, quality, and simplicity, and is used in home appliances, various industrial applications, space exploration, electronic power, and other special applications. Since then, its market scope has been expanding. Among these, the use of high-temperature sheathed heaters is expected to continue to grow in the future.

When a conventional sheathed heater is used for a long period of time, the heating wire gradually thins out and generates local heat, which eventually leads to wire breakage. At this time, current flows between the heating wire and the metal pipe, which sometimes causes the pipe to melt, which can be extremely dangerous.

However, a method for detecting breakage in sheathed heaters in advance and preventing pipe melting has not yet been fully established, and the reality is that they are still used in extremely dangerous conditions.

The present invention solves the above-mentioned drawbacks and provides a safe sheathed heater.

A feature of the present invention is that a detection element capable of detecting oxygen or nitrogen concentration is embedded inside a conventional sheathed heater.

Generally, in a sheathed heater in which both ends of a metal pipe are sealed with low-melting glass or heat-resistant resin, the heating wire reacts with the oxygen or nitrogen in the air that exists inside the sheathed heater during use, creating a vacuum inside the sheathed heater. state.

In this way, when the inside of the sheathed heater becomes a vacuum state, significant evaporation of the component elements of the heating wire occurs,
Breaking of the heating wire is promoted.

The present invention detects a disconnection of a sheathed heater in advance by detecting the degree of vacuum inside the sheathed heater by detecting the concentration of oxygen or nitrogen.

In this way, by detecting the end of the sheathed heater's lifespan before it is about to break, and replacing it with a new sheathed heater, it is possible to completely prevent the pipe melting that occurs with conventional sheathed heaters, and the effect is It is extremely large.

The present invention will be described below based on specific examples with reference to FIG.

In FIG. 2, 11 is a metal pipe, 12 is a heating wire with terminal rods 13 connected to both ends, 14 is an electrically insulating powder filled in the metal pipe 11, and 15 is an oxygen or A sensing element for detecting the concentration of nitrogen, 16 is a lead wire of the sensing element 15, 17 is a low melting point glass that seals the end opening of the metal pipe 11, and 18 is a heat resistant resin.

In the above configuration, the lead wire 16 was connected to a measuring instrument (not shown) for measuring the concentration of oxygen or nitrogen, and the heating wire 12 was energized. Then, the sheathed heater was replaced when the oxygen concentration showed 0 or when the nitrogen concentration began to decrease. When this operation was repeated 10 times, no breakage of the sheathed heater or pipe melting was observed.

On the other hand, a sheathed heater in which the oxygen or nitrogen concentration detection element 7 was not embedded was also made at the same time, and when 10 pipes were energized under the same conditions, two pipes were fused when the wire broke.

In the present invention, the average lifespan of 10 sheathed heaters until replacement was approximately 90% of the lifespan of conventional sheathed heaters before disconnection, indicating extremely high efficiency.

As is clear from the above explanation, the present invention embeds a detection element that detects the concentration of oxygen or nitrogen inside the sheathed heater, so it is possible to predict wire breakage or melting in advance, and it is possible to create an extremely safe sheathed heater. Obtainable.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a typical sheathed heater, Figure 2
The figure is a sectional view of a main part of a sheathed heater showing an embodiment of the present invention. 2...Heating wire, 3...Metal pipe, 4...Electric insulating powder, 7...Detecting element.

Claims (1)

[Claims] 1. A heating wire made of a metal resistance heating element is placed in the center of a metal pipe, an electrical insulating powder is filled between the metal pipe and the heating wire, both ends of the metal pipe are sealed, and the electrical insulating powder has an oxygen concentration. Or a sheathed heater with an embedded detection element that detects nitrogen concentration.