JPS5916711B2 - Sea heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheathed heater, in particular a sheathed heater with a pipe surface temperature of 8.
Withstands temperatures around 00℃ and has improved insulation performance.

Heat-resistant inorganic insulating powder is added to the magnesia filling powder to prevent moisture and improve the characteristics of the sheathed heater. Conventionally, the sheathed heater is as shown in Figure 1a,
An insulating material 4 was filled between a metal pipe 1 and a heating wire 3.9 having terminals 2 at both ends, and the ends were sealed with glass 5 and silicone rubber 6.

In this case, moisture proofing is achieved by the glass 5, but this glass 5 has the disadvantage of being weak against thermal and mechanical impact forces, making it difficult to obtain stable quality. Also, 650℃
For products that are used at high temperatures above, ・ If the terminal opening is completely sealed, the metal vapor in the heating wire 3 and pipe 1 will dissipate and the withstand voltage will gradually deteriorate during use. However, the requirement for a perfect glass seal also brought with it some weaknesses. On the other hand, as shown in FIG. 1b, silicone resin or the like is added to the magnesia powder to form the insulating filling powder 4' without relying on the glass seal.
There were also some that were made of living flesh and were moisture-proof. However, the heat resistance of this added silicone resin is up to 400° C., and there is a drawback that the effect is completely lost at temperatures higher than that. The present invention solves the above-mentioned drawbacks, and an embodiment thereof will be described below with reference to FIG. 2.

In FIG. 2, 11 is a spiral heating wire, 12 is a terminal whose one end is welded or screwed onto the end of the heating wire 11, 13 is a metal pipe that covers the heating wire 11, and 14
1 is an insulating material that maintains insulation between the heating wire 11 and the metal pipe 13, and 16 is silicone rubber for the purpose of simple sealing. The insulating material 14 is first made of magnesia filling powder 14a.
5, a heat-resistant inorganic filler powder 14b of a calcia-silica compound is added as an additive in an amount of 3 to 10% by weight relative to the magnesia filler powder 14a.

After going through the usual sheathed heater manufacturing processes of filling, rolling diameter reduction, annealing, and molding, it is finally sealed with silicone cone rubber 16 or the like. In the thus-made sheathed heater, the heat-resistant inorganic insulating powder 14b made of calcia-silica compound is a kind of desiccant than the magnesia filling powder 14a, so it is hydrated first, and the magnesia filling powder 14a does not absorb moisture and is sufficiently insulated. expensive. Furthermore, it has been experimentally shown that if the calcia-silica compound heat-resistant inorganic filler powder 14b is added in an amount of 10% or more, the heat conduction decreases in the high temperature range of 700'C or higher.
The insulation during heating (when energized) decreases, and when the addition is less than 3%, the period during which the hydration power of the heat-resistant inorganic filler powder of calcia-silica compound 14b is saturated is at high temperatures (4'C) and high humidity (95%). In an indoor test, it reached saturation after about 2 months.

Therefore, from both of the above, 3 to 10% is most effective in actual use. In addition, from a process standpoint, the moisture resistance is almost determined by the amount of moisture permeation of the silicone rubber 16 that performs simple sealing, but epoxy resin or the like can be used as a simple sealing material if it is heated and cured.

Furthermore, since glass is not used as a sealant and silicone rubber is used, the seal can be sealed after annealing using a malleable material, so it can be moisture-proofed at that stage, eliminating the need for a stoppage in the process or a subsequent dehumidification process. As described above, the sheathed heater of the present invention has
Moisture-proofing is achieved by adding a calcia-silica compound, which not only withstands high-temperature use and improves insulation performance, but also eliminates the use of glass as a sealant, making it possible to provide products with higher reliability. There is no need to worry about damage to the glass, and from the perspective of the manufacturing process, sealing can be performed after annealing, eliminating the need for the usual dehumidification process, making overall cost reductions and mass production extremely easy.

[Brief explanation of the drawing]

Figure 1a is a sectional view of the main parts of a conventional sheathed heater, Figure 1b
2 is a sectional view of a main part of another conventional sheathed heater, and FIG. 2 is a sectional view of a main part of a sheathed heater showing an embodiment of the present invention. 11...Heating wire, 13...Metal pipe, 14...Insulating material, 14a...Magnesia filling powder, 14b...Heat-resistant inorganic filling powder,
16...Silicone rubber.

Claims (1)

[Claims] 1. A calcia-silica compound added to magnesia filling powder in an amount of 3 to 10% by weight is filled as an insulating material between a metal pipe and a heating wire inserted into the metal pipe. A sealed sheathed heater. 2. The sheathed heater according to claim 1, wherein the simple sealing is made of silicone rubber or epoxy resin.