JPS6153837B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a sheathed heater having a flat portion, and particularly aims at simplifying the device and improving the shape accuracy of the finished product.

Conventionally, in a spiral sheathed heater as shown in Fig. 1, a heating wire 2 is arranged in the center of a metal pipe 1 as shown in Fig. 2, and an insulating material 3 such as magnesium oxide is filled, and then the filling density is adjusted. In order to increase the diameter, the diameter is reduced by rolling, swaging, etc., and then annealing is performed to remove machining strain and stress, and further, after smoothing, as shown in FIG. 3, the flat part 1a is formed as shown in FIG. 4. The entire body was manufactured by press working using a mold 4 as shown in FIG.

This press processing equipment requires large-scale equipment, which has the drawback of high equipment costs, and if a mistake is made in setting the sheathed heater in the mold, the mold may be damaged. There were also drawbacks.

The present invention eliminates the drawbacks of the conventional sheathed heater manufacturing method described above, and embodiments of the present invention will be described below.

In Fig. 5, 5 is a sheathed heater, in which a heating wire is placed in the center of a metal pipe, filled with an insulating material, and the diameter is reduced by rolling, swaging, etc. to increase the packing density, and further processing distortion is removed. It is annealed to remove stress and then formed into a spiral shape. A lower mold 6 has a spiral groove 7 on its upper surface, and a recess 8 is formed in the center. Reference numeral 9 denotes a fan-shaped upper mold, and a downwardly protruding protrusion 10 is formed at the center of the fan.
The end portion 11 of the portion of the upper mold 9 on which the sheathed heater 5 is pressed has a gently curved surface.

In the above configuration, the sheathed heater 5 is pressed. For example, in the case of a sheathed heater with an outer diameter of 6.6 mm, a pressing pressure of 2 tons or more is required per 1 cm of length. In addition, in order to improve the dimensional accuracy of flat parts, etc., a pressing force of 5 to 15 tons per 1 cm of length is required. Therefore, when pressing a sheathed heater with a length of 80 to 170 cm, the
A pressurizing force of tons is required, but in this example, for example, if the press work is performed by dividing into 4 parts, the press work will be 350 tons, and if the press work is performed by dividing into 6 parts, the press work will be 233 tons, and the equipment may be small. Moreover, it is economical. In addition, in the press, the convex part 10 of the upper die 9 is fitted into the concave part 8 of the lower die 6 to perform local press processing, and further, the convex part 10 of the upper die 9 is rotated around the convex part 10. Then, further pressing is performed to complete the entire pressing. Note that the end portion 1 of the portion of the upper mold 9 where the sheathed heater 5 is pressed
1 has a gently curved surface, so even if the press surfaces overlap, no stepped portion will occur in the sheathed heater 5. Further, although there may be cases where the sheathed heater 5 in the part that is not pressurized by the press work comes off the groove 7, the shape of the groove 7 is set so that the cross-sectional shape of the sheathed heater 5 contracts, and furthermore, the preliminary press It is a good idea to pressurize the whole thing once beforehand.

During the above-mentioned pressing, even if the sheathed heater 5 is set incorrectly in the groove 7 or the insulating material falls out, the total pressing pressure is small, so the mold 6,
9 will not destroy. Furthermore, when pressing a spiral sheathed heater as in this example, it is possible to set the extreme pressures at the center and the outer circumference to be the same, thereby obtaining a spiral sheathed heater with high dimensional accuracy. be able to.

As is clear from the above description, according to the present invention, press working is performed by dividing the press work locally, so that equipment can be downsized and a sheathed heater with high dimensional accuracy can be obtained.

[Brief explanation of the drawing]

Figure 1 is a plan view of a typical spiral sheathed heater, Figure 2 is a sectional view of the same sheathed heater before press working, Figure 3 is a sectional view of the same sheathed heater after press working, and Figure 4 is a conventional FIG. 5 is a sectional view of the press working process of a sheathed heater showing an embodiment of the present invention, FIG. 6 is a plan view of the upper mold for performing the press working, and FIG. A in Figure 6
- It is a sectional view taken along the A′ line. 5... Sheathed heater, 6... Lower mold, 7...
Groove, 9... Upper mold.

Claims (1)

[Scope of Claims] 1. After reducing the diameter and annealing a metal pipe containing an insulating material and a heating wire, press processing for processing it into a flat shape is performed using an upper mold rotatably supported with respect to a lower mold. A method for manufacturing a sheathed heater, characterized in that the process is divided into two or more times by rotating a mold. 2. The method for manufacturing a sheathed heater according to claim 1, wherein the press working is performed using an upper mold having a gently curved end.