JPH0648886B2 - Surface shaping method for plastic cables - Google Patents

Description

TECHNICAL FIELD The present invention relates to a power cable, particularly a plastic sheath cable.

[Prior Art] Conventionally, in the surface finishing method of the end portion of the plastic sheath cable, the outer semiconductive layer portion is peeled off by using a knife, a tool or the like due to the structure of the cable, and then smoothed with sandpaper. However, at this time, fine scratches are formed on the surface and unevenness is formed.

Hereinafter, description will be given with reference to the drawings. FIG. 4 is a cross-sectional view showing a state in which a rubber mold stress cone 4 forming a prefabricated type connection portion is fitted around the outer periphery of a plastic sheathed cable composed of the cable conductor 3, the cable insulator 2 and the outer semiconductive layer 1. is there. That is, since the outer semiconductive layer 1 of the plastic sheathed cable has a larger outer diameter than the cable insulator 2, the portion B in FIG. 4 is shown enlarged at the interface with the outer peripheral surface of the insertion hole of the rubber mold stress cone 4. Also, as shown in FIG. 5, the gap 9 is inevitably generated. This causes a decrease in withstand voltage when the prefabricated type connection portion is formed.

[Problems to be Solved by the Invention] In such a conventional surface processing method for a plastic sheathed cable, the outer semiconductive layer is roughly cut with a tool, a knife or the like,
Furthermore, this is a method of finishing the insulation with a sandpaper to a smooth surface.At this time, fine scratches are created by the sandpaper, and the sand of the sandpaper cannot be completely cut off and adheres to the surface of the insulation, resulting in a withstand voltage. It is also a cause of lowering.

For this reason, in the outer semiconductive layer of the cable and the insulation resistant boundary part,
The outer semiconductive layer is tapered so as not to cause a step with the insulator. And, such a tapered portion is generally about 10 to 30 mm, but in a connecting portion structure using a rubber mold stress cone, these are preferably longer, and currently, a semiconductive polyethylene sheet is used. Molding is performed to form a tapered portion. For this reason, there is a drawback that a heating step, its time, and a lot of materials are required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a surface shaping method for a plastic sheath cable, which eliminates such drawbacks, shortens the assembly time of cable accessories, and improves performance.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view for explaining the surface shaping method of the plastic cable of the present invention, in which the plastic cable is heated by inserting a metal tube for surface shaping, and the plastic cable inside is in a cross-sectional view showing the expanded state. It is a figure.

First, the outer semiconductive layer 1 at the end of the plastic cable including the cable conductor 3, the cable insulator 2 and the outer semiconductive layer 1 is peeled off. Next, the surface shaping metal tube 5 is fitted to the outer circumference. The inner diameter of the metal tube 5 is 1t to 1.2 larger than the outer diameter of the outer semiconductive layer 1 of the plastic cable.
It is formed to be large by t (t is the thickness of the insulator 2 of the plastic cable), the left opening is large, and the inner diameter is formed in a tapered shape. Then, the metal tube 5 is heated to a temperature of 80 ° C. to 120 ° C. with a conductor temperature of 70 ° C. to 100 ° C. as a guide by heating means such as a heater 6 attached to the outer surface thereof. When the metal tube 5 is heated, the plastic cable inside is heated to soften and expand, so that the outer semiconductive layer 1 first comes into contact with the inner wall of the metal tube 5, and also the insulator 2 part comes into contact therewith. Become.
Since the entire plastic cable part expands as the temperature rises, the surface of the plastic cable is covered by the metal pipe 5.
It is crimped to the inner wall of the. At this time, the surface of the plastic cable is the same as the finished state of the inner surface of the metal tube 5. And the temperature of the metal tube 5 and the cable conductor 3
In order to constantly monitor the temperature of the above, thermocouples 7 and 8 for inspecting the heater temperature are installed on the outer periphery of the metal tube 5 and the cable conductor 3 to inspect so as not to overheat.

Next, the heater is turned off, the plastic cable is cooled, and the metal tube 5 is removed. The state of the plastic cable at this time is shown in FIG. The portion A of FIG. 2 is enlarged and shown in FIG. At the boundary between the cable insulator 2 and the outer semiconductor layer 1, the portion near the right end of the outer semiconductive layer 1 moves into the cable insulator 2 as shown in FIG. The outer diameter of the layer 1 is formed on a surface having the same outer diameter.

Therefore, when the rubber mold stress cone forming the prefabricated type connection portion is inserted into the plastic cable end portion thus shaped, the inner surface of the stress cone is uniformly adhered to the plastic cable surface and no gap is generated.

[Effect of the Invention] As described above, when the plastic cable surface shaping method of the present invention is applied, the vicinity of the outer semiconductive layer end portion has the same outer diameter as the cable insulator, so that the interface with the rubber mold stress cone is applied. There is no gap and the electrical insulation performance is significantly improved.

The surface of the insulator is as smooth and straight as the inner surface of the metal tube. This is very effective in prefabricated connections.

[Brief description of drawings]

FIG. 1 is an explanatory view of a surface forming method of the present invention, FIG. 2 is a cross-sectional view of a cable end portion after the surface forming method is performed, and FIG. 3 is an enlarged view of a portion A of FIG. FIG. 4 is a vertical sectional view when a rubber mold stress cone showing a conventional example is inserted, and FIG. 5 is an enlarged view of a portion B in FIG. 1 ... External semiconductive layer 2 ... Cable insulator 3 ... Cable conductor 4 ... Rubber mold stress cone 5 ... Surface shaping metal tube 6 ... Heating heater 7,8 ... Heating heater Temperature monitoring thermocouple

Claims (1)

[Claims] 1. The plastic cable is obtained by removing the outer semiconductive layer at the end of the plastic cable, inserting a metal tube having a smooth inner surface, and energizing a heating heater provided on the outer periphery of the metal tube to heat the plastic cable. A surface shaping method for a plastic cable, which is characterized by expanding and softening and bringing the metal tube into close contact with the inner surface of the metal tube to make the outer surface of the plastic cable a smooth surface having the same diameter.