JPH0139199B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a rod-shaped sheath heater, which comprises inserting a hard core wrapped with heating wire into a sheath and filling the gap with an insulating material.

There are various conventional methods for manufacturing this type of sheath heater, but these methods have the following major drawbacks. That is, this type of heating element has a length of 2
The length is ~6 m, and the gap between the outer metal tube and the hard core inserted inside it is minute, 1 to 2 mm, and the hard core is held correctly in the center of the outer metal tube over this length (6 m). Since it is extremely difficult or almost impossible to do so, the gap between the two may be uneven depending on the location, and there is even a risk that the heating wire may come into contact with the exterior metal tube and cause an electric leak. In addition, when filling the gap between the outer metal tube and the hard core with inorganic insulating powder, after combining the two, the powder is poured from above into the gap between the two while standing upright and vibrating. If you do this, the grains will have different sizes, and for this reason, the larger grains will accumulate at the bottom,
There is vertical unevenness depending on the particle size, with small particles accumulating at the top. Further, the packing density becomes higher in the lower part due to the pressure of the powder from above, and the density becomes lower in the upper part, resulting in uneven density between the upper and lower parts. As mentioned above, unevenness in the gap, unevenness in powder particle size, and unevenness in density have a synergistic effect, and heat is radiated irregularly in various parts of the sheathed heater, so it cannot be said to be a perfect product as a rod-shaped sheathed heater. There is also the risk that the heat will build up and cause the wire to break at that location. It is an object of the present invention to provide a method for manufacturing a rod-shaped sheath heater that eliminates the irregular heat radiation unevenness as described above and further allows the amount of heat radiation to be controlled as required. In order to achieve this object, the present invention improves the powder insertion in conventional products, and is characterized by inserting a cylinder made of an inorganic insulating material and molding it to a required size, and pulverizing it to form an insulating layer. It is.

EMBODIMENT OF THE INVENTION Hereinafter, an example of the embodiment of this invention will be illustrated and explained. A tape-shaped heating wire 2 is wound spirally around the outer periphery of a hard core 1 made of ceramic or the like, and is connected to the conductor 3 at the center of the hard core 1 at the tip to form a heater body 4. On the outer periphery, inorganic insulating powder e.g.
An insulating molded body 5 made of MgO into a cylindrical shape is tightly inserted, and this is further tightly inserted into a sheath 6 prepared separately. Thus, external pressure is applied from the outer periphery of the sheath 6 by an appropriate method to reduce the outer diameter without damaging the rigid core 1. For example, the insulating molded body 5
When the wall thickness of t1.6mm is reduced to 1mm, the molded body 5 is crushed and compressed to an appropriate density, forming an insulating layer 5A, densely filling the space between the hard core 1 and the sheath 6, and generating heat. The wire 2 is protected and the tip of the sheath is thus closed with a lid 7 to produce a product.

With the above configuration, the current flows through the heating wire 2 and the conducting wire 3, generates heat, and is transmitted through the insulating layer 5A to radiate the heat to the outside of the sheath.Since the heating wire 2 is very close to the sheath 6, high heat is generated. This enables heat dissipation.

The characteristic effects of this invention will be described below. An insulating molded body 5 uniformly molded with a wall thickness t is attached to a hard core 1
Since the outer diameter of the sheath 6 is narrowed and reduced so that the rigid core body 1 is tightly inserted between the sheath 6 and the rigid core body 1 and is not damaged, the rigid core body 1 is held correctly in the center of the sheath 6, and the heat generating wire 2 Since the distance from the sheath 6 to the sheath 6 can be made constant anywhere, the unevenness of the gap described above with respect to conventional products is eliminated. In addition, since the insulating molded body 5 is inserted in advance and crushed at that point to form the insulating layer 5A, there is no unevenness in particle size caused by the size of particles or density unevenness depending on the top and bottom, which occurs when pouring powder, as in conventional products. Does not occur. Next, when manufacturing the insulating molded body 5, an insulator with different thermal conductivity such as MgO, BN (boron nitrite), BeO
(beryria), Al ₂ O ₃ (alumina), etc. 5 ₁ 5 ₂
5 ₃ ... is molded, and a molded body 5 made of BN is placed in the part of the total length of the sheath heater that generates a large amount of heat.
₂ and use MgO molded body 5 ₁ in areas with low heat generation to actively control the amount of heat dissipated and control the temperature inside the sheath heater to prevent accidents such as disconnection. It is possible. Also, although BeO (beryria) is expensive, it has particularly excellent heat resistance and insulation properties, so it is suitable for use in particularly necessary parts of the total length of the sheath heater.
A high-quality rod-shaped sheath heater can be obtained by using the insulating molded body ₅₃ made of BeO. As described above, there is no irregular heat radiation unevenness, and the heat radiation can be controlled freely, so it is possible to extract the desired heat and provide a method for manufacturing a rod-shaped sheath heater with good heat resistance and efficiency.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional side view of an embodiment of the present invention in the process of inserting an insulating molded body, Fig. 2 is a cross-sectional side view of a completed product of the embodiment of this invention, and Fig. 3 is a perspective view of the insulating molded body. be. 1...Hard core, 2...Heating wire, 3...Conducting wire,
4...Heater body, 5...Insulating molded body, 6...Sheath, 7...Closing lid, 5A...Insulating layer.

Claims (1)

[Claims] 1 The heating wire 2 is spirally wound around a hard core 1 to form a heater body 4, and the heater body 4 is wrapped around a plurality of cylindrical insulating molded bodies 5 made of an inorganic insulator and having a desired thermal conductivity.
After tightly inserting these into the sheath 6, the outer periphery of the sheath 6 is pressurized to reduce its diameter to crush the insulating molded body 5 without damaging the rigid core 1, thereby insulating. A method for manufacturing a rod-shaped sheath heater, characterized in that a thin layer of layer 5A is formed.