JPS6362071B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Background of the Invention The mold joint process is generally performed as follows (FIG. 1).

On the conductor connection 10 and the cable insulation 20 in the vicinity thereof, an insulation layer 30 is formed using an uncrosslinked rubber or plastic material containing a crosslinking agent, forming the basis of the reinforcing insulation. The rubber or plastic material may be rolled into a tape or sheet, or formed by injection molding at a temperature below the crosslinking temperature.

Then, a pressing means such as a pressing winding 40 or a mold is applied thereto, and heating and pressure are applied.

Then, the insulating layer 30, which is the basis of the reinforcing insulator, melts and undergoes a crosslinking reaction, and the cable insulator 20
They fuse together and become one.

At that time, the temperature change on the top A of the conductor connection part 10 and the surface B of the insulating layer 30, which is the basis of the reinforcing insulator, is the "second temperature change".
It will look like this.

The relationship between the crosslinking temperature and the required heating time is shown in Figure 3 (for PE with a degree of crosslinking of 80%).

Since heating is generally performed from the outside, the temperature on the conductor connection portion 10 is the lowest in the insulating layer 30, and its rise is also slower than that at the surface of the insulating layer 30.

Heating during molding is carried out at a constant temperature and is continued until a constant degree of crosslinking is obtained even at the lowest temperature point (A in FIG. 1).

If the heating temperature is increased as shown in Figure 3, the molding time can be shortened. However, the heating temperature is different from the materials used (the outside of the insulating layer 30 and the pressing tape 4).
0) is limited to a range that does not deteriorate.

It is already known that, even at the same heating temperature, when a large amount of crosslinking agent is blended, the separation start time of the crosslinking agent becomes earlier and the crosslinking rate becomes faster.

However, conventionally, the reinforcing insulator at the connection part was expected to have the same electrical characteristics as the cable insulator 20, and when the cable insulator 20 was made of cross-linked PE, it was made of the same material, that is, to the same degree as the cable insulator 20. The insulating layer 30, which is the basis of the reinforcing insulator, was formed using PE tape mixed with a crosslinking agent. Also, since the same type of crosslinking agent is used for EP rubber,
The mixing ratio was also about the same as that of the cable insulator 20.

Objects and Structure of the Invention By using rubber or plastic containing more crosslinking agent than the cable insulation 20 as a material for forming the insulation layer 30 which is the basis of the reinforcing insulation, the molding time is shortened.

That is, dicumyl peroxide, benzoyl peroxide, t-butyl peroxybenzoate, etc. are generally used as the crosslinking agent, and are mixed in the cable insulator 20 in an amount of about 2 to 3%.

Therefore, in the present invention, for example, the entire insulating layer 30, which is the basis of the reinforcing insulator, is treated with a crosslinking agent 8.
It is made of rubber or plastic with a content of ~10%, which is higher than that of the cable insulator 20. Formation is conventionally performed using tape, sheet, or compound. Then, heat and pressure molding is performed.

Alternatively, as shown in FIG. 4, only the innermost thin part 31 of the insulating layer 30 is made of rubber or plastic containing a large amount of cross-linking agent, and the outer part 32 is as thin as the cable insulator 20 as before. A crosslinking agent may be included.

Note that this technology can also be applied to cable heads.

Effects of the Invention The amount of crosslinking agent contained in the innermost thin layer of the insulating layer, which is the source of the reinforcing insulator, is reduced by the amount of crosslinking agent contained in the rubber or plastic that constitutes the cable insulator (conventionally, an appropriate amount (approximately equal to the amount of crosslinking agent added to the reinforcing insulation, which was supposed to be the same), so even when heated from the outside, the crosslinking of the innermost part of the insulation layer will not be particularly delayed.

Therefore, the overall molding time can be shortened.

[Brief explanation of drawings]

Figure 1 is a general explanatory diagram of the rubber mold joint method, Figure 2 is a diagram of the relationship between heating time and temperature change,
Fig. 3 is a diagram showing the relationship between temperature and time for crosslinking, and Fig. 4 shows the insulating layer 30 which is the basis of the reinforcing insulator in the present invention.
An explanatory diagram of an example of a method of forming. 10: Conductor connection part, 20: Cable insulator, 3
0: Insulating layer that is the basis of reinforcing insulator, 31: Innermost thin layer part.

Claims (1)

[Claims] 1. An insulating layer is formed on the cable insulation at and near the conductor connection using an uncrosslinked rubber or plastic material containing a crosslinking agent, and is then used as a reinforcing insulation layer. When performing a mold joint of a rubber/plastic cable by applying a pressing means to the mold joint and applying heat and pressure from the outside, A method for mold jointing a rubber/plastic cable, characterized in that the amount of the crosslinking agent is greater than the amount of the crosslinking agent contained in the rubber or plastic constituting the cable insulation.