JPH06267641A - Sheath heater with temperature fuse subjected to bending process and its manufacture - Google Patents

Abstract

PURPOSE:To prevent abnormal high temperature of a sheath heater by connecting a temperature fuse to the outer end of one side terminal pin, and connecting a terminal to the outer end, and then, fixing an outer pin and the terminal with outer plugs. CONSTITUTION:A heating wire 21 is inserted into an inner pipe 11 made of a metal, and an insulating powder 31 is filled. The heating wire 21 is connected to terminal pins 41 and 42, the space between the pins 41 and 42, and the pipe 11 is sealed by inner plugs 51 and 52, and a temperature fuse 61 is connected to the outer end of the pin 41. A metallic outer pipe 81 is fitted to the outer periphery of the pipe 11, and, a terminal 71, the pin 42, and the pipe 81 are fixed with outer plugs 91 and 92, and furthermore, the pipes 11 and 81 are processed to bend at the intermediate positions. In such a way, the fuse 61 is positioned to the outer side of the pipe 11, and installed between the pin 41 and the terminal 71 at the inside surrounded by the inner plug 51, the pipe 81, and the outer plug 91. Consequently, the generation of an abnormal high temperature of a sheath heater, resulting from a burnout of the temperature fuse beforehand, can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheathed heater with a temperature fuse and a method for manufacturing the sheathed heater.
BACKGROUND ART Seeds heaters are widely used as a heating source for household electric appliances such as oven toasters, rice cookers, and irons, as well as industrial electric furnaces. The present invention relates to such a sheathed heater, and more particularly to a sheathed heater with a temperature fuse subjected to a bending process and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, as a sheath heater, a metal pipe, a heating wire inserted in the pipe, an insulating powder filled and compacted in the pipe, and attached to both ends of the heating wire. It has been proposed to provide a terminal pin and a plug member for sealing between the terminal pin and the pipe (Japanese Patent Laid-Open Nos. 49-35930 and 60-60).
117590, JP-B-60-24552).

Many of these sheathed heaters are bent into various shapes in relation to their applications, and the bent sheathed heaters are generally heating wires in which terminal pins are attached to both ends of a metal pipe. And then filling the pipe with the insulating powder, and then reducing the diameter of the pipe to consolidate the insulating powder, and then annealing the pipe, and then plug the gap between the pipe and the terminal pin. It is manufactured through the steps of sealing and bending the pipe.

However, the conventional sheathed heater as described above has a drawback in that the sheathed heater becomes abnormally high in temperature for some reason and may cause a burst or a fire.

[0005]

The problem to be solved by the present invention is that the conventional sheathed heater cannot prevent it from reaching an abnormally high temperature.

[0006]

DISCLOSURE OF THE INVENTION The present invention, therefore, is directed to an inner pipe made of metal, a heating wire inserted into the inner pipe, an insulating powder filled and compacted in the inner pipe, Terminal pins attached to both ends of the heating wire, an inner plug for sealing between the terminal pin and the inner pipe, a thermal fuse connected to at least one outer end of the terminal pin, and an external fuse. The inner pipe and the outer pipe are provided with a terminal connected to an end, a metal outer pipe fitted to the outer periphery of the inner pipe, and an outer plug for fixing the terminal and the outer pipe. The present invention relates to a sheathed heater with a temperature fuse, which has been subjected to bending, characterized in that the sheathed heater is provided with bending.

The present invention also relates to a method of manufacturing a sheathed heater with a temperature fuse, which has been subjected to bending, characterized by undergoing the following first to fourth steps. First step: A heating wire having terminal pins attached to both ends is inserted into an inner pipe made of metal, the inner pipe is filled with insulating powder, and the inner pipe is reduced in diameter to consolidate the insulating powder. Step 2): After annealing the inner pipe, sealing the inner pipe and the terminal pin with an inner plug Third step: connecting a thermal fuse to the outer end of at least one terminal pin, A step of connecting a terminal to the outer end of the thermal fuse, fitting an outer pipe made of annealed metal to the outer periphery of the inner pipe, and fixing the terminal and the outer pipe with an outer plug. Fourth step : Process of bending inner pipe and outer pipe into desired shapes

In the sheathed heater of the present invention, the mutual relationship among the metal inner pipe, the heating wire, the insulating powder, the terminal pin and the inner plug is the same as in the case of the conventional sheathed heater. In the sheathed heater of the present invention, the thermal fuse connected to the outer end of at least one terminal pin, the terminal connected to the outer end of the thermal fuse, the metallic outer pipe fitted to the outer periphery of the inner pipe, and An outer plug for fixing the terminal and the outer pipe is provided, and the inner pipe and the outer pipe are bent.

In the manufacturing method of the present invention, the procedure for bending the inner pipe through the first step and the second step has the same constitution as that of the conventional sheathed heater as far as these are concerned. In the manufacturing method of the invention, as a third step after the first step and the second step, a thermal fuse is connected to the outer end of at least one of the terminal pins, and a terminal is connected to the outer end of the thermal fuse. After that, through a step of fitting an outer pipe made of annealed metal to the outer periphery of the inner pipe and fixing the terminal and the outer pipe with an outer plug,
The inner pipe and the outer pipe are bent.

[0010]

According to the sheathed heater of the present invention, the thermal fuse is interposed between the terminal pin and the terminal outside the inner pipe and surrounded by the inner plug, the outer pipe and the outer plug. It is possible to prevent the sheathed heater from abnormally high temperature due to the thermal fuse being burned out in advance. It is possible to omit the outer pipe, the outer plug and the terminal and insert a temperature fuse inside the inner pipe between the heating wire and the terminal pin, but such a sheathed heater is very troublesome for industrial mass production. In particular, this is extremely inconvenient because the temperature fuse is burned out when the inner pipe having the temperature fuse inside is annealed before the bending process.

[0011]

FIG. 1 is a partially omitted sectional view showing an embodiment of the present invention. The heating wire 21 is inserted into the inner pipe 11 made of metal, the inner pipe 11 is filled with the insulating powder 31, and the insulating powder 31 is compacted. Heating wire 21
Terminal pins 41 and 42 are attached to both end portions of the above, and the inner pins 51 and 52 are sealed between the terminal pins 41 and 42 and the inner pipe 11.

A thermal fuse 61 is connected to the outer end of the terminal pin 41 taken out from the inner plug 51.
A terminal 71 is connected to the outer end of the thermal fuse 61. An outer pipe 81 made of metal is fitted on the outer periphery of the inner pipe 11, and an outer plug 91 is provided between the terminal 71 and the outer pipe 81 and between the terminal pin 42 taken out from the inner plug 52 and the outer pipe 81. , 92 fixed. The inner pipe 11 and the outer pipe 81 are bent at their intermediate portions (not shown).

The sheathed heater shown in FIG. 1 was manufactured by the following procedure. First, a heating wire having terminal pins attached to both ends is inserted into an inner pipe made of SUS304 and having an outer diameter of 7.5 mmφ, and the inner pipe is filled with magnesium oxide powder as insulating powder. The magnesium oxide powder was consolidated by rolling to a diameter of 0.5 mm. Next, the inner pipe was annealed at a maximum ambient temperature of 1050 ° C., and then sealed with lead glass as an inner plug between the inner pipe and the terminal pin.

Further, a thermal fuse is connected to the outer end of one terminal pin, a terminal is connected to the outer end of the thermal fuse, and then the outer circumference of the inner pipe is annealed in advance under the same conditions as described above. An outer pipe made of SUS304 was fitted and lightly rolled, and fixed with silicone rubber as an outer plug between the terminal and the outer pipe and between the other terminal pin and the outer pipe. Then, the middle portion of the inner pipe and the outer pipe was bent into a spiral shape.

[0015]

As is apparent from the above, the sheathed heater of the present invention described above can prevent an abnormally high temperature from occurring, and the manufacturing method of the present invention can efficiently use such a sheathed heater. It has the effect that it can be mass-produced stably and stably.

[Brief description of drawings]

FIG. 1 is a partially omitted sectional view showing an embodiment of the present invention.

[Explanation of symbols]

11 ... Inner pipe, 21 ... Heating wire, 31 ... Insulating powder, 41, 42 ... Terminal pins, 51, 52
... Inner plug, 61 ... Thermal fuse, 71 ... Terminal, 81 ... Outer pipe, 91, 92 ... Outer plug

Claims (2)

[Claims] 1. An inner pipe made of metal, a heating wire inserted in the inner pipe, an insulating powder filled and compacted in the inner pipe, and terminal pins attached to both ends of the heating wire. An inner plug for sealing between the terminal pin and the inner pipe, a thermal fuse connected to an outer end of at least one of the terminal pins, and a terminal connected to an outer end of the thermal fuse, A metal outer pipe fitted to the outer periphery of the inner pipe; and an outer plug for fixing the terminal and the outer pipe, wherein the inner pipe and the outer pipe are bent. A sheath heater with a temperature fuse that is characterized by bending. 2. A method for manufacturing a sheathed heater with a temperature fuse, which is subjected to a bending process, characterized by comprising the following first to fourth steps. First step: A heating wire having terminal pins attached to both ends is inserted into an inner pipe made of metal, the inner pipe is filled with insulating powder, and the inner pipe is reduced in diameter to consolidate the insulating powder. Step 2): After annealing the inner pipe, sealing the inner pipe and the terminal pin with an inner plug Third step: connecting a thermal fuse to the outer end of at least one terminal pin, A step of connecting a terminal to the outer end of the thermal fuse, fitting an outer pipe made of annealed metal to the outer periphery of the inner pipe, and fixing the terminal and the outer pipe with an outer plug. Fourth step : Process of bending inner pipe and outer pipe into desired shapes