JPH03212110A - Manufacture of power cable-connecting insulator tube - Google Patents

Abstract

PURPOSE:To mold the stress cone part of an external semiconductor on an insulting layer by casting an insulating rubber into an insulating layer-molding metal mold to mold a rubber insulating layer and thereafter by casting a semiconductive rubber on both sides of the tube part of the external semiconductor. CONSTITUTION:After a prepared internal semiconductor 1 and external semiconductor tube part 33 are arranged in a metal mold 5, an insulating rubber is injected into the metal mold 5 so that an insulating layer 2 is injection molded and heated and vulcanized further. In this case, when the metal mold 5 or core 7 is suitable provided with an air vent, no turbulence of surface based on residual air occurs in the rise part of the tapered part of the injection-molded insulating layer 2. Then, an insulation tube semimolded body 8 composed of the internal semiconductor 1, insulating layer 2 and external semiconductor tube part 33 is covered with the metal mold 9, semiconductive rubber is cast into the metal mold 9, and the stress cone part of the external semiconductor is injection-molded and heated and vulcanized further. Thus, the whole cable- connecting insulator tube can be molded by injection molding.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing an insulating tube for power cable connection used as a plug-in connection for rubber or plastic power cables.

(Problem to be solved by the prior art and the invention) The insulating cylinder for power cable connection used in the plug-in connection part of rubber or plastic power cables has an internal semiconductor as shown in the vertical cross-sectional view in Fig. 3. 11°3°, an insulating layer 2, and an outer semiconductor 3. Usually, the inner semiconductor 1 and the outer semiconductor 3 are made of semiconductive EP rubber, and the insulating layer 2 is made of insulating EP rubber. There is. The insulating layer 2 has tapered portions 21 on both sides, and the external semiconductor has stress cone portions 31 at both ends and a cylindrical portion 33 in the middle.
The stress cone part 31 has a cylindrical part 32 at the end thereof which comes into contact with the insulation layer and the external covering layer of the cable when the cable is plugged.

In order to improve manufacturing efficiency, rubber injection molding is used to manufacture this insulating tube for cable connection, but even if you try to mold the inner semiconductor layer, the insulating layer, and the outer semiconductor layer in this order by injection molding, The viscosity of the semiconducting rubber is high, and the thickness of the cylindrical part of the external semiconductor cannot be made very thick (usually about 3 to 4 cm) due to the reduction in the outer diameter of the insulating cylinder. In injection molding, the flow resistance of the semiconductive rubber Δ is large, which not only makes molding difficult, but also increases the injection pressure, which tends to cause damage such as deformation and cracks to the inner insulating layer. For this reason, even though the internal semiconductor and insulating layer are molded by injection molding, the external semiconductor layer is not injection molded, but is wrapped in raw rubber tape, covered with a mold, heated under pressure, molded, and vulcanized. Usually, this is done using the inefficient method of

In order to improve this, an inner semiconductor and an outer semiconductor are manufactured in advance, placed in a mold for forming an insulating layer, and an insulating rubber with low flow resistance is injected into the mold. A method of molding and molding an insulating layer has been attempted.

However, since the outer semiconductor body has a cylindrical part 32 with a small inner diameter of the stress cone part 31 on both sides of a cylindrical part 33 with a large inner diameter, it is difficult to remove the core of the mold after injection molding. It is difficult to manufacture conductors in one piece by injection molding. Furthermore, when casting an insulating layer inside the external semiconductor, it is difficult to remove air between the tapered rising part of the stress cone part 31 adjacent to the cylindrical part 32 and the mold core. It tends to leave air bubbles in the parts,
There is a problem in that a gap is formed at the interface between the external semiconductor and the insulating layer at the tapered rising portion of the stress cone portion of the formed insulating cylinder, and the interface is disturbed. It is conceivable to provide an air vent hole in the tapered rising part of the stress cone part in order to vent air from the above part, but providing a hole in this part of the external semiconductor will cause disturbance of the electric field, so it is not enough. If a hole is provided with a size that has an air venting effect, the effect will be large, and it is difficult to employ it in the manufacture of insulating tubes for connecting high voltage cables. Furthermore,
Depending on the selection of the inner diameter of the cylindrical part 32 of the stress cone portion of the external semiconductor prepared in advance and the outer diameter of the mold core in which it is set, the inner diameter of the injection molded insulating layer and the stress of the outer semiconductor A difference in diameter may occur between the inner diameter of the cone part and the inner diameter of the cylindrical part, and manufacturing errors in the outer semiconductor body and adjustment errors in the outer diameter of the core are likely to cause the above-mentioned difference in diameter.

Due to the above-mentioned difficulties, the method of placing the pre-fabricated rice internal semiconducting material and external semiconducting material into a mold, and then casting insulating rubber into the mold to form an insulating layer is not possible. It is difficult to put it into practical use, and as mentioned above, it is usually
The inefficient method used was to wrap a semiconductive raw rubber tape around an injection-molded insulating layer, pressurize it with a mold, heat it, mold it, and vulcanize it.

The present invention proposes a new manufacturing method for an insulating tube for cable connection, which eliminates the above-mentioned difficulties and makes it possible to mold all of the inner semiconductor, insulating layer, and outer semiconductor by injection molding. .

(l! Means for Solving the Problem) The present invention arranges a pre-molded inner semiconductor and an outer semiconductor cylindrical part in a mold for molding an insulating layer, and insulating rubber is placed in the mold. The method is characterized in that after a rubber insulating layer is formed by casting, semiconducting rubber is cast on both sides of the cylindrical part of the outer semiconductor, and the stress cone part of the outer semiconductor is formed on the insulating layer. do.

(Examples and effects) The present invention and its embodiments will be described in detail below.

In the present invention, the outer semiconductor body and the inner semiconductor body are lined in advance with semiconductive EP rubber or the like. Further, an injection port for insulating rubber is provided in advance in the cylindrical portion of the external semiconductor. The production of these is not limited to injection molding, but from the viewpoint of production efficiency and cost, injection molding is preferable and most suitable for the purpose of the present invention. There is no particular difficulty in molding only the cylindrical portion of the external semiconductor by injection molding, unlike in the case of injection molding the entire external semiconductor as one piece.

After placing the prefabricated inner semiconductor body and outer semiconductor cylindrical part in a mold as shown in Figure 1, insulating rubber is injected into the mold and an insulating layer is injection molded. Heat and vulcanize. In this case, if an appropriate air vent is provided in the mold or core, there is no risk of surface disturbance due to residual air at the rising part of the tapered part of the injection-molded insulating layer. In FIG. 1, 1 is a pre-molded internal semiconductor,
Reference numeral 33 designates a cylindrical body portion of the external semiconductor body which is also previously molded. 34 is an insulating rubber injection port provided in the cylindrical body portion. 5
is a mold, and is constructed as a proportioned mold with splits in the longitudinal or radial direction. Reference numeral 6 denotes an insulating rubber injection port (injection gate) provided in the mold, which communicates with the insulating rubber injection port 34 of the external semiconductor cylindrical body portion 33 .

7 is the core. The insulating rubber injection port 34 of the cylindrical body portion 34 is cut after the insulating layer is molded and vulcanized, and a semiconductive paint is applied to the cut surface.

Next, as shown in FIG.
A mold 9 for molding the stress cone portion of the external semiconductor is placed on the insulating cylindrical semi-molded body 8 consisting of 3, and semiconducting rubber is cast into the mold to form the stress cone portion of the external semiconductor. is injection molded and then heated and vulcanized. 10 is a semiconductive rubber injection port of the mold, and 7 is a core. If the surface of the tapered part of the insulating layer is finished neatly without any disturbances, when the stress cone portion is injection molded, the interface between the insulating layer and the stress cone portion will also be finished neatly without any disturbances.

By the method described above, the entire insulating tube for cable connection can be molded by injection molding.

In injection molding, a mold is set on a heated hot plate, and preheated rubber is injected into the mold.

Therefore, the vulcanization time is reduced to about half compared to when a raw rubber tape is wrapped and a mold is placed over the tape and heated.

Although the above description has been made regarding the case of manufacturing an insulating tube for straight line connection of cables, the method of the present invention can of course be applied to the case of manufacturing an elbow insulating tube for cable connection as shown in FIG. The method of the present invention is more effective when manufacturing more complex elbow insulation tubes. In FIG. 4, 1 is an internal semiconductor, 2 is an insulating layer, and 3 is an external semiconductor. We are prepared. A conductor connection fitting may be embedded inside the internal semiconductor body 1 integrally therewith. In manufacturing such elbow insulating tubes, as in the case of manufacturing insulating tubes for linear connections, the cylindrical portion of the external semiconductor and the internal semiconductor are manufactured in advance, and these are placed in a mold. The insulating rubber is injection molded into the mold, the insulating layer is injection molded, and the insulating layer is vulcanized.Then, a mold for molding the stress cone of the external semiconductor is covered, and the semiconductor is injected into the mold. Rubber is cast and the stress cone part is injection molded and vulcanized.

(Effect of the invention) According to the manufacturing method of the present invention, the internal semiconductor All insulating layers and external semiconductors are manufactured with high manufacturing efficiency. It can now be manufactured using injection molding.

And easy. Compared to the conventional method of wrapping raw rubber tape around the external semiconductor and heat-molding it by covering it with a mold, the process of manually winding the raw rubber tape can be omitted, and as mentioned above, injection molding requires less processing time. Since the sulfur time is greatly shortened, manufacturing efficiency can be significantly improved.

Moreover, according to the method of the present invention, it is possible to injection mold the entire external semiconductor after molding the conventional insulating layer, or to manufacture the entire external semiconductor including the entire stress cone in advance. When injection molding an insulating layer by arranging it in a mold, there are some difficulties, such as deformation or cracking of the insulating layer during injection molding of the external semiconductor, and the possibility that the stress cone of the external semiconductor and the insulating layer may This eliminates problems such as disturbances at the interface between the stress cone and the diameter difference between the inner diameter of the cylindrical part of the stress cone and the inner diameter of the insulating layer. You can get a tube.

In addition, in the manufacturing method of the present invention, it is most advantageous to injection mold all of the inner semiconductor, the insulating layer, the cylindrical part of the outer semiconductor, and the stress cone part, and it is most suitable for the purpose of the present invention. However, the present invention does not limit the manufacture of the internal semiconductor body and the external semiconductor cylinder body portion to be manufactured in advance by injection molding. This is because even if these are manufactured in advance by a method other than injection molding, the effects of the present invention described above can be enjoyed.

[Brief explanation of drawings]

1 and 2 are longitudinal cross-sectional views illustrating the forming of the stress cone portion of the insulating layer and the external semiconductor by the manufacturing method of the present invention, and FIGS. 3 and 4 are respectively for straight connection of cables. FIG. (Explanation of symbols) ■=Inner semiconductor, 2: Insulating layer, 3: External semiconductor [body,
31: Stress cone part, 33; Cylinder part, 5: Mold, 7: Core

Claims (1)

[Claims] The pre-molded inner semiconductor body and outer semiconductor cylindrical part are placed in a mold for forming an insulating layer, and after insulating rubber is cast into the mold to form the rubber insulating layer, A method for manufacturing an insulating cylinder for connecting a power cable, characterized by casting semiconductive rubber on both sides of a cylindrical part of a semiconductor, and molding a stress cone part of an external semiconductor on an insulating layer.