JPH0442719A - Forming method of mold stress cone - Google Patents

Abstract

PURPOSE:To form a mold stress cone having excellent electrical characteristics by fitting a cone type semiconductor to the tapered face on the cable sheath end side of a body applied with an insulation tape and then thermally molding the taped body and the semiconductor integrally through a single heating process. CONSTITUTION:An insulating polyethylene tape 13 is wound, in spindle shape, around a cable insulator 12. A cone type semiconductor 17 having a tapered face 15a approximately corresponding to the tapered face 13a of the spindle type polyethylene tape and rounded at the tip thereof is formed. The semiconductor 17 is then fitted to the end of the spindle type cable sheath and fitted tightly to the tapered face 13 through thermal contraction. An insulating polyethylene tape 20 is then applied on the semiconductor 17 and the cylindrical part of the polyehtylene taped layer 13 and subjected to thermal molding. Consequently, taped layers are fused integrally to make round the tip of the semiconductor layer thus improving the electrical characteristics.

Description

[Detailed Description of the Invention] CObject of the Invention] (Industrial Application Field) The present invention is intended for the purpose of electrolytic relaxation on the outer periphery of a cable insulator, for example, at an intermediate connection portion or a terminal connection portion of a cross-linked polyethylene insulated cable, etc. The present invention relates to a method for forming a mold stress cone.

(Conventional technology) Conventionally, cross-linked polyethylene insulated cables (hereinafter referred to as C
It is called a cable. ), a molded stress cone is formed using cross-linked polyethylene or the like on the outer periphery of the insulator at the cable end to alleviate electrolytic properties.

FIG. 5 is a cross-sectional view showing an example of the structure of such a molded stress cone, in which a spindle-shaped molded insulation reinforcing body 2 is provided around the outer periphery of the cable insulator 1 which is exposed by peeling off the end of the cable. A semiconductive layer 3 is provided from the tapered surface 2a on the end 3 side to the cylindrical portion 2b, and an insulating layer 4 is further formed from the semiconductive layer 3 to the insulating reinforcing body 2.

In such a mold stress cone, as shown in the figure, the shape of the insulating reinforcing body 2 is changed to the tip of the Taber surface 2a in order to prevent local concentration of electrolyte on the tip of the semiconducting layer 3. The semiconducting layer 3 is formed on the Taber surface 2a so as to fill this rounded portion.

For this reason, conventionally, in its formation, an insulating tape is wound around the outer periphery of the cable insulator 1 in a spindle shape, as shown in FIG. After it is attached and heated for the first time, thereby forming a rounded spindle-shaped insulating reinforcement body 2, a semiconductive tape is wrapped on the tapered surface 2a, and an insulating tape is further wrapped on these. A method has been adopted in which a second heating is performed to fuse the tape-wound layers together.

However, in such a conventional method, the heating molding process has to be performed twice, once when forming the insulating reinforcement body 2 and when final molding, and the semiconductive layer 3 is formed by wrapping the tape around it. However, due to the lack of roundness or smoothness at the tip, initial electrical characteristics could not be obtained.

(Issue 8 to be solved by the invention) In this way, in the conventional mold stress cone forming method, the heating molding process is performed twice in order to round the tip of the semiconductive layer to prevent concentration of electrolyte. In addition to the poor workability, it is difficult to form a rounded surface with good smoothness, making it impossible to obtain the initial electrical characteristics.

The present invention has been made to solve these conventional problems, and provides a molded stress cone with excellent electrical properties in which a smooth, well-shaped, rounded tip of the semiconducting layer is formed in a single heating process. The purpose is to provide a method that can be configured.

[Structure of the Invention (Means for Solving the Problems)] The present invention involves winding an insulating tape around the outer periphery of an insulator at a cable end in a substantially spindle shape, and then winding an insulating tape on the tapered surface of the end side of the cable sheath of the insulating tape wrapping body. Then, a semi-conductor which has been formed in advance into a cone shape with a tapered surface on the inside that can match the tapered surface and whose tip side edge has a predetermined roundness is fitted, and further, from above this semi-conductor, After winding the insulating tape over the insulating tape wrapping, the insulating tape wrapping and the semiconductor are integrally heat-molded in a one-degree heating step. do.

(Function) In the method of the present invention, the heating step may be repeated once in the final step, improving workability. Further, since the rounded tip of the semiconducting layer can be formed into a shape with a smooth surface and a small curvature, a mold stress cone with improved electrolytic relaxation characteristics can be formed.

(Example) Next, embodiments of the present invention will be described using the drawings.

1 to 4 are longitudinal sectional views showing the process of forming a polyethylene molded stress cone according to an embodiment of the present invention.

In the present invention, as shown in FIG.
An insulating polyethylene tape 13 is wound around the outer periphery of 2 in a spindle shape with a predetermined thickness.

On the other hand, as shown in FIG. 2, the spindle-shaped insulating polyethylene tape wound layer 13 has a tapered surface 15a that substantially corresponds to the tapered surface 13a on the cable sheath end 14 side, and a semiconducting conductor to be formed at the tip thereof. Curved surface 1 that matches the roundness R of the layer
A cone-shaped semiconductor 17 having a predetermined roundness R at the tip is molded using a mold 16 having a molding surface 15 with a shape 5b formed thereon.

That is, from above the tapered surface 1.5a of the molding surface 15 to above the curved surface 15b, a heat-shrinkable tube made of semiconductive polyethylene with approximately twice the length of these tubes] 8 is connected with one end to the proximal end of the tapered surface 1.5b. After wrapping the semiconductive polyethylene tape 19 in a predetermined shape from the curved surface to the tapered surface, the heat shrinkage remaining on the curved surface 15b side is shown in FIG. The tube 18 is folded back and heat-shrinked, and then molded into the mold 16.
The cone-shaped semiconductor 17 is obtained by removing the waste.

As shown in FIG. 4, the semiconductor 17 thus obtained is fitted onto the tapered surface 13 on the cable sheath end 14 side of the previously formed spindle-shaped insulating polyethylene tape winding layer 13. , heat-shrink it again to bring it into close contact with the tapered surface 13.

Next, the insulating polyethylene tape 20 is again wound to a predetermined thickness from the semiconductor 17 to the cylindrical portion of the insulating polyethylene tape winding layer 13, and then an appropriate restraining tape (not shown) is applied over these. Roll it up and heat-form it while applying pressure.

As a result, the tape winding layers are fused together to form a polyethylene molded stress cone with good electrical properties and a rounded radius formed at the tip of the semiconductive layer.

Note that the inner layer portion of the semiconductor body 17 may be formed using a heat shrink tube made of the same semiconductive polyethylene as the outer layer instead of the semiconductive polyethylene tape 19.

Furthermore, in the above embodiments, the method for forming a molded stress cone at the end of a CV cable has been described, but the present invention is not limited to such embodiments, and may be applied to intermediate connections of various other rubber/plastic cables. It can be widely applied as a method for forming a molded stress cone in a terminal connection portion, etc.

[Effects of the Invention] As explained above, according to the method of the present invention, since a pre-molded semiconductor is fitted, only one heat molding step is required, improving workability. Further, since the tip of the semiconductor can have a smooth surface and a rounded shape with a small curvature, it is possible to form a mold stress cone with improved electrical characteristics.

[Brief explanation of the drawing]

1 to 4 are longitudinal cross-sectional views showing the process of forming a molded stress cone at the end of a CV cable according to an embodiment of the present invention, and FIG. 5 shows the structure of a molded stress cone formed by a conventional method. FIG. 6 is a vertical cross-sectional view showing a cable termination in the process of forming a molded stress cone by a conventional method. 11...CV cable terminal part 12...
......Cable insulator 13.20...Insulating tape winding layer 13a...Tapered surface 14 of insulating tape winding layer... ...Cable sheath end 15...
... Mold molding surface 16 ... Mold 17 ... Semiconductor 18 ... Semi-conductive heat shrink tube 19・
・・・・・・Semi-conductive tape R・・・・・・・・・・・・
...Roundness of semiconductors (Figure 1, Figure 2) 2

Claims (1)

[Claims] (1) Wrap an insulating tape around the insulator of the cable terminal in an almost spindle shape, and on the tapered surface of the cable sheath end side of this insulating tape wrapping body, in advance, attach a tapered surface that can match the tapered surface to the inside. Shaped into a cone with
A semiconductor having a predetermined roundness on its tip side edge is fitted, and an insulating tape is wound over the semiconductor and onto the insulating tape wrapping body, and then a single heating process is performed. A method for forming a molded stress cone, which comprises integrally heat-molding each of these insulating tape wrappings and a semiconductor.