JPH0132636B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for molding reinforcing insulation layers of rubber-plastic insulated cable connections.

[Conventional technology] The connection part of rubber/plastic insulated cable is
A reinforcing insulating layer is provided on a semiconducting layer formed by winding and heating a semiconducting tape on the cable conductor connection portion, and this reinforcing insulating layer is formed by forming an internal semiconducting layer 22 as shown in the second figure. A split mold 23 is placed over the cable conductor connection portion 21 coated with , this mold and an insulating synthetic resin extruder 24 are heated, and the insulating synthetic resin is extruded and filled into the mold 23 to form a reinforcing insulating layer 25 . was being molded.

This reinforcing insulating layer molding method has the disadvantage that the internal pressure of the filled synthetic resin in the mold decreases due to curing shrinkage of the filled synthetic resin when the mold is cooled, resulting in voids and cracks inside the molded reinforcing insulating layer. When this crack occurs at the interface between the conductor connection and the internal semiconducting layer, the internal semiconducting layer swells up to fill the crack.
This bulge causes protrusions on the internal semiconducting layer, which has the disadvantage of deteriorating the electrical characteristics of the connection portion.

In order to prevent such a reduction in internal pressure due to cooling and hardening of the resin filled in the mold, Japanese Patent Application No. 57-217556
No. 59-108288), it has been proposed to cool and solidify the resin while gradually pressuring it into the mold from the resin injection port.

[Problems to be Solved by the Invention] As described above, in the method of cooling and solidifying the resin while gradually pressuring it into the mold, it is more difficult to cool and solidify the resin located deep inside the mold than to cool and solidify the filled resin near the resin injection port. If the mold is cooled and solidified more quickly, the resin that is press-fitted later will be blocked by the resin that has solidified earlier near the injection port, and will not be fully press-fitted into every corner of the mold, resulting in voids inside the reinforcing insulating layer. There was a problem that it was not possible to completely prevent the occurrence of cracks and cracks.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for molding a reinforcing insulating layer of a rubber/plastic insulated cable connection part, which can completely prevent the occurrence of voids and cracks in the reinforcing insulating layer.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the reinforcing insulating layer molding method of the present invention includes a method for forming a reinforcing insulating layer by placing a mold over a conductor connection portion coated with an internal semiconducting layer, and forming a mold around the outer periphery of the mold. A cooling pipe is provided, the area cooled by this cooling pipe is divided to form a plurality of divided cooling areas, and the synthetic resin for the insulating layer is extruded and filled into the mold, and after this filling, the synthetic resin is continued. is extruded and injected into the mold, and cooling is performed using a cooling pipe while extruding and injecting. At this time, cooling is performed by dividing multiple cooling zones from the cooling zone at the end of the mold to the synthetic resin injection port side. The reinforcing insulating layer on the conductor connection part is cooled and hardened sequentially from both ends toward the synthetic resin injection port by sequentially cooling the conductor to a certain cooling area.

[Function] The synthetic resin for the insulating layer extruded and filled into the mold is cooled by the cooling pipe and hardened, thereby forming a molded insulating layer on the conductor connection portion.

The volume reduction due to shrinkage when the filled resin extruded into the mold cools and hardens is compensated for by the resin that is continuously injected even after extrusion and filling into the mold.
This continuous injection of supplementary resin prevents the internal pressure of the filled resin in the mold from decreasing.

The cooling pipes on the outer circumference of the mold have multiple divided cooling zones, and the cooling zone on the mold end side is cooled first, and the cooling zone on the resin injection port side is cooled later, and by this sequential cooling, the filling resin on the end side is cooled down. The filling resin on the resin injection port side is cooled and hardened first, and the filling resin on the resin injection port side is finally cooled and hardened, so that the continuous injection of the supplementary resin described above can be carried out without hindrance.

In this way, the occurrence of voids and cracks inside the reinforcing insulating layer when the filled resin is cooled and hardened, which conventionally occur, can be completely prevented.

[Example] An example of the present invention will be described below with reference to FIG.
1 and 1' are the connection terminals of the power cables to be connected;
2 and 2' are cable conductors at both cable connection terminals, 3 is a sleeve that compressively connects both cable conductors 2 and 2', and 4 is a sleeve that is connected to the compression sleeve, and a semiconductive tape is wound and heat-fused thereon. It is an internal semiconducting layer.

Reference numeral 5 designates a two-split mold that surrounds and covers this cable conductor connection portion, 6 designates a synthetic resin injection port of this mold 5, and 7 designates a resin extruder coupled to this injection port 6.

8 is a cooling pipe wound around the outer circumference of the mold 5, and the area cooled by this cooling pipe 8 is divided into a plurality of divided cooling areas 9, 10, 1.
form 1. The winding density in the divided cooling zones 9, 10, 11 of the cooling pipe 8 is set to an appropriate winding pitch, for example, the windings become tighter toward both ends of the mold 5 to form the divided cooling zones 9, 10, 11.

As mentioned above, the mold 5 placed over the cable conductor connection part is heated and set to an appropriate temperature above the melting point of the injected synthetic resin by electrical heating when extruding and injecting the synthetic resin. The synthetic resin is extruded from the resin extruder 7 to the injection port 6 at a temperature higher than its melting point, and is injected and filled into the mold 5. After the synthetic resin for the insulating layer is filled into the mold 5, the heating power for the mold is turned off, and then the synthetic resin is further extruded and injected into the mold 5 while being cooled by a cooling pipe.

To carry out this cooling, divided cooling zones 9, 1
0 and 11 are sequentially cooled from the cooling zone on the end side of the mold 5 to the cooling zone on the synthetic resin injection port 6 side.

After the synthetic resin for the insulating layer is extruded and filled into the mold 5 in this way, voids and cracks are caused by sequentially cooling the divided cooling areas with the cooling pipe 8 while extruding and injecting the synthetic resin. A molded reinforcing insulating layer 12 is formed.

When the temperature of the mold 5 becomes approximately 80° C. or lower, the mold is removed. In addition, if necessary, mold reinforcing insulation layer 1
A semiconductive tape is wound around the outer periphery of 2 and heat fused to form an external semiconductive layer.

The synthetic resin for the molded reinforcing insulating layer 12 includes polyolefins such as polyethylene and polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-vinylmethoxysilane copolymer. One or more of polyolefin copolymers such as polymers, rubbers such as polybutadiene, acrylonitrile-butadiene-styrene rubber, and polyolefin graft copolymers such as chlorinated polyethylene, styrene-grafted polyethylene, and vinylmethoxysilane-grafted polyethylene. If a compound such as a blender or crosslinkable low-density polyethylene is used, and crosslinking treatment is required, the molded reinforcing insulating layer 12 is heated to 200°C.
The reinforcing insulating layer 12 is crosslinked by heat treatment for about 4 hours.

According to the experimental results, the method of the present invention allows
Shave the end of a 66KV cross-linked polyethylene insulated power cable into a pencil shape and compress the cable conductor into a sleeve 3
After forming the internal semiconducting layer 4 by winding a semiconductive tape thereon and heat-sealing it, a mold 5 is formed.
A water-cooled copper pipe was wrapped around the outer circumference of the mold to form three cooling zones, and polyethylene containing a cross-linking agent was extruded and injected into the mold 5 using a 25 mmφ extruder.
The three cooling zones are sequentially cooled by the method of the present invention described above, and after the temperature at both left and right ends of the mold reaches 50°C, resin is continuously injected until the temperature at the center reaches 50°C to form a reinforcing insulating layer. 12 was molded and subjected to heat-crosslinking post-treatment, the AC breakdown voltage value was measured by applying voltage at 170 KV for 3 hours and increasing the pressure in steps of 15 KV/30 minutes. In contrast, as a comparative example, polyethylene mixed with a cross-linking agent was extruded and injected into the mold as described above, and the mold was 50
The reinforcing insulating layer of the comparative example was formed by natural cooling until the temperature reached ℃, and no resin was injected during this natural cooling, and the reinforcing insulating layer was molded after thermal crosslinking. The value was 170KV/5 minutes.

Note that the present invention can be applied not only to the above-mentioned cable connection part but also to the formation of a reinforcing insulating layer of a cable terminal connection part.

[Effects of the Invention] As described above, the present invention is capable of extruding and filling a synthetic resin into a mold, and then sequentially injecting the resin into a plurality of divided cooling zones from the end side of the mold to the synthetic resin injection port side. Since the reinforcing insulating layer is molded on the conductor connection portion after cooling, it is possible to completely prevent voids and cracks from forming in the molded reinforcing insulating layer.
It is something.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of one embodiment of the method of the present invention, and FIG.
The figure is an explanatory diagram of a conventional example. 4: Internal semiconductive layer coating, 5: Mold, 6: Synthetic resin injection port, 8: Cooling pipe, 9, 10, 11: Divided cooling zone, 12: Reinforced insulating layer.

Claims (1)

[Claims] 1. After attaching a cooling pipe to the outer periphery of a mold that covers a conductor connection portion having an internal semiconductive layer coating to form a cooling area divided into a plurality of parts, and extruding and filling a synthetic resin for an insulating layer into the mold, Subsequently, while extruding and injecting the synthetic resin into the mold, the plurality of divided cooling zones are sequentially cooled from the end side of the mold toward the synthetic resin injection port side to form a reinforcing insulating layer on the conductor connection portion. A method for forming a reinforcing insulating layer for a rubber/plastic insulated cable connection part, characterized by: