JPS59139585A - Method of forming reinforced insulating layer of rubber and plastic cable connector - 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 The present invention relates to a method for forming a reinforcing insulating layer for intermediate or terminal connections of rubber or plastic cables.

As is well known, at the joints of rubber and plastic cables, in order to electrically insulate and reinforce the joints, an internal semiconductive layer is formed by wrapping a semiconductive tape over the cable conductor joints and heating them. After that, a reinforcing insulating layer is provided thereon. Conventionally, this reinforcing insulating layer was created by placing a chive split mold 14 over the cable conductor connection portion 11 provided with the internal semiconducting layer 12, as shown in FIG. The reinforcing insulating layer 13 was formed by extruding and injecting resin into the mold 14 while heating the machine 15. However, according to this conventional method, the injected resin shrinks when the mold is cooled, causing the molded reinforcing insulating layer to shrink. If voids or cracks are formed in the conductor connection area, especially at the interface where the conductor connection part contacts the internal semiconducting layer 12, the internal semiconducting layer bulges to fill the crack and a protrusion is generated on the semiconducting layer 12. The present invention was made with the aim of solving the above-mentioned problem, and one embodiment of the present invention will be explained below with reference to the drawings. After connecting the cable conductors with a compression sleeve and forming an internal semiconductive layer by winding and heat-sealing a semiconductive tape thereon, the cable conductor connection section is coated with a semiconductive layer 2 as shown in Fig. 2. A reinforcing insulating layer 3 is formed by surrounding the mold 1 with a chive-splitting mold 4 and extruding and injecting resin into the mold to fill it, and then cooling the mold 4 while continuously injecting the resin.

The mold 4 can be cooled by cooling the mold naturally, or by winding a vibro around the outside of the mold 4 at a predetermined pitch as shown in Figure 2, and passing a cooling medium through the vibro to cool the mold. Alternatively, in order to allow the mold to be cooled sequentially from both ends toward the resin injection port, for example, the cooling pipe wound around the outside of the mold may be wound more densely toward both ends. The mold is cooled in a plurality of parts, and cooled in such a way that resin can be smoothly injected into the mold during cooling. When the mold temperature drops to about 80°C or less, the mold is removed, and if necessary, a semiconductive tape is wrapped around the outer circumferential surface of the molded reinforcing insulating layer 3 and heat fused to form an external semiconductive, electrically conductive layer (Fig. (omitted). In the method of the present invention, the molding resin extruded into the mold includes polyolefins such as polyethylene and polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene/ethyl acrylate copolymer, ethylene - Polyolefin copolymers such as vinylmethoxylan copolymers, rubbers such as polybutadiene, acrylonitrile-butadiene-styrene rubber, and polyolefin graft copolymers such as chlorinated polyethylene, styrene-grafted polyethylene, vinylmethoxysilane-blatted polyethylene, etc. Alternatively, use two or more types of Prene Fmer or a compound that can be crosslinked, such as crosslinked low-density polyethylene, and if crosslinking is required, heat-treat the molded reinforced insulation wJ3 at 200°C for 4 hours to create reinforced insulation. Crosslink mold M3.

Next, to explain a specific example of the present invention, the end of a 66Kv cross-linked polyethylene insulated cable is shaved into a lead-like shape, the internal conductor is connected with a compression sleeve, and a semiconductive tape is wound and heat-fused on top of the end. After forming the internal semiconductor 'tJi layer 2, the conductor connection part 1 is covered with a split mold 4 of 25'mm.
A reinforcing insulating layer is formed by extruding and injecting a polyethylene resin containing a crosslinking agent and a vinylmethoxysilane grafted polyethylene resin into the mold using a φ extruder 5, and then the mold is cooled by the method shown in Table 1. , the reinforcing insulating layer 3 according to the embodiment of the present invention, which was molded by continuously injecting resin until the mold temperature reached a predetermined temperature, and the reinforcing insulating layer 3 according to the comparative example, which was molded by continuously injecting resin until the mold temperature reached a predetermined temperature.
The pressure was increased in 30 minute steps.

Table 1 There was 1.

According to the present invention, after filling the resin into the mold 4 placed over the conductor connection portion as described above, the mold is cooled while continuously extruding and injecting the resin, and the volume of the filled resin increases as the mold cools. Since the reinforcing insulating layer 3 is molded by replenishing the amount of resin corresponding to the change, there is no risk of voids or cracks occurring in the molded reinforcing insulating layer, and there is no risk of voids or cracks occurring in the internal semiconducting layer due to cracks. There is no fear of the formation of protrusions, and as is clear from the above table, a reinforcing insulating layer with excellent electrical properties can be obtained. Furthermore, even better electrical characteristics can be obtained by cooling the mold in multiple parts after filling with resin so that the resin can be smoothly replenished into the mold during cooling. It should be noted that the present invention is not limited to the above-mentioned embodiments, but can of course be applied to the formation of a reinforcing insulating layer at a cable terminal connection portion.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing a conventional molding method for reinforcing insulating layers;
FIG. 2 is an explanatory diagram showing one embodiment of the reinforcing insulating layer forming method according to the present invention. 1: Conductor connection part 2 = Internal semiconductive resin 3z reinforcing insulating layer 4: Mold 5; Extruder 6: Pipe

Claims (1)

[Scope of Claims] L A mold is placed over the cable conductor connection portion with an internal semiconducting layer applied to the outer circumferential surface, and after filling the mold with resin, the mold is cooled while continuously extruding and injecting the resin. A method for forming a reinforcing insulating layer for a rubber or plastic cable connection part, characterized in that a reinforcing insulating layer is formed on a conductor connection part by molding the reinforcing insulating layer on the conductor connection part. A method for forming reinforcing insulating layers for rubber and plastic cable connections, which is characterized by cooling separately.