JPS63143772A - Method of molding plastic cable joint - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for molding an insulator of a connecting portion of a cross-linked polyethylene cable (hereinafter referred to as a Cv cable).

[Conventional technology]

A conventional method of molding a CV cable connection part will be explained with reference to FIG. The connecting ends of the cables 1.1' to be connected are each penciled into cable conductors 2.2'
are exposed and abutted against each other, and a conductor sleeve 3 is fitted over this -H to electrically connect them together. Then, on this connection part, an insulating layer 4 is formed in a spindle shape by extruding uncrosslinked polyethylene or wrapping it with tape. Next, in order to mold this insulating layer 4, a mold 7 is fitted around the outer periphery of this connection part, and while an inert gas such as nitrogen gas is introduced into the mold and pressurized to a constant pressure, a heater (not shown) is used. The insulating layer 4 is molded integrally with the cable insulator by crosslinking the insulator of the insulating layer 4 by applying heat from the outside.

(Problems to be Solved by the Invention) However, one of the major problems when crosslinking the mold joint portion formed in this way is that when the insulating layer is melted during heating to perform the crosslinking reaction. Pressurization using only gas pressure causes eccentricity due to its own weight. That is, in order to cause the crosslinking reaction, it is necessary to heat the polyethylene of the insulating layer to a high temperature of 140 to 200° C., which is higher than the crystal melting point. In the molten state before polyethylene is crosslinked, the viscosity decreases, and as shown in Figure 3, C
The v-cable connection section may become eccentric due to the weight of the polyethylene 9 insulating layer.

As methods to prevent this, methods have been adopted so far, such as crosslinking in a liquid having the same specific gravity as polyethylene, and molding a thin metal piece in a cast shape along the insulating layer vertically. However, in the former method, the method of pressurizing, heating and sealing the liquid is very complicated and difficult, and in the latter method, there are problems such as local deformation caused by unbalanced pressurization.

The present invention has been made to overcome the above-mentioned drawbacks of the prior art and provides an improved method for molding a Cv cable connection.

(Means and effects for solving the problems) In the method of the present invention, when molding the insulating layer of the Cv cable connection part, firstly, as a preliminary crosslinking, the inside and middle layer of the insulating layer is heated inside the cable using a Takaoka wave induction heating device. The crosslinking reaction is carried out partially by heating from the cable conductor, and after this is once cooled, the entire insulating layer is crosslinked by being heated from the outside to carry out the main crosslinking. .

Therefore, in preliminary crosslinking, only a partial crosslinking reaction is performed from the inner layer to the middle layer of the insulating layer, and since the outer periphery of the insulating layer is kept in a solid state, there is no possibility that the entire insulating layer will melt and cause eccentricity. It's fleeting.

Furthermore, in the subsequent main crosslinking, the remaining outer layer portion of the insulating layer is integrally crosslinked.

(Embodiment) Hereinafter, an embodiment of the insulator molding method for a Cv cable connection portion of the present invention will be described based on the drawings. As shown in Figure 1, the connecting ends of the Cv cables 1.1" to be connected are each penciled to expose the cable conductors 2 and 2', which are butted together, and a conductor screen 3 is fitted over them for electrical connection. The insulating layer 4 is formed in the shape of a spindle at this connection part by extruding an uncrosslinked polyethylene material or by winding it with tape.

In this state, first, as a pretreatment work, the cable conductor 2.2' at the center of the Cv cable connection part is heated from the outside of the insulating layer 4 using a high-frequency induction heating device consisting of a high-frequency coil iron core 5 and a high-frequency induction coil 6 to insulate it. 7 Heat #4 from the inside. Then, the crosslinking reaction is caused to occur partially from the inner layer to the middle layer of the insulating layer 4.

After once cooling from this state, as shown in FIG. 2, it is placed in a crosslinking mold 7 and heated from the outside with a heater or the like (not shown) under a constant pressure of inert gas.
The entire connection portion insulating layer 4 is subjected to a crosslinking reaction to be integrated.

At the time of the above-mentioned pretreatment work for partially crosslinking, the insulating layer 4
The outer periphery of is completely solid at low temperatures.

Therefore, even if the insulator melts due to its own weight, it will not deform due to its own weight, and there is a uniform thermal gradient between the inner and outer layers of the insulating layer 4, which undergo crosslinking reaction at high temperatures. 811 minutes, there is no concentration of thermal stress. Therefore, there is no possibility of electrical defects occurring. Once crosslinked, the insulator of the insulating layer 4 will not be deformed by a force similar to its own weight even if the temperature is higher than its melting point. Therefore, eccentricity does not occur at all during main crosslinking.

(Effects of the Invention) As described above, according to the method of molding a Cv cable connection portion of the present invention, the operation is simple and it is possible to form a mold joint without eccentricity. Furthermore, since eccentricity can be prevented even without a metal piece or the like to hold it down, local stress concentration can be avoided and electrical defects are less likely to occur. Therefore, it is possible to manufacture a mold joint with excellent electrical performance.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view showing the state of preliminary cross-linking applied to the method of molding a Cv cable connection part applied to the present invention. FIG. 2 is a mold forming method of a Cv cable connection part applied to the present invention FIG. 4 is a cross-sectional view showing the state of crosslinking applied to the method. FIG. 3 is a cross-sectional view for explaining the eccentricity of the CV cable connection section. 1.1=-----Cable 2.2'--One cable conductor 3--One conductor sleeve 4--One insulation layer Patent applicant Hitachi Cable Co., Ltd. Agent Koyama 1) Mitsuo

Claims (1)

[Claims] In a method of molding an insulator for a cross-linked polyethylene cable connection part, the connection ends of the cables to be connected are each penciled to expose the cable conductors, and a conductor sleeve is fitted and connected, and then the unreacted An insulating layer is formed by extruding or wrapping the insulator with tape, and as a pre-crosslinking step, only the cable conductor is heated by high-frequency induction heating to perform a partial crosslinking reaction from the inner layer to the middle layer of the insulating layer. After cooling this, A molding method for a plastic cable connection part, characterized in that main crosslinking is performed by heating the entire connection part from the outside.