JPS6023476B2 - Method for forming connections of insulated cables - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming connections in rubber or plastic insulated cables.

Cables with rubber or plastic insulation layers are now used in connection, but the deterioration of the electrical properties due to connection is a serious problem, especially when they are used for very high voltages.

To solve this problem, conventionally, the connection part exposes the conductor at the end of the cable, and after the conductor is properly connected, an internal semiconducting layer and a reinforcing insulating layer are provided on the conductor connection part. By heating this under pressure, the insulating layer of the cable and this reinforcing insulating layer are integrated. This insulating layer is designed so as not to impair the electrical properties of the cable, and to ensure that the dimensions of the connection itself are 4.
It is generally formed in a mold using a material that is the same as or similar to the insulating material of the cable so that it can be folded. Due to the stability of the electrical properties of molded connections using such insulating materials, it is common practice to wrap an internal semiconducting layer over the conductor connections, such as by wrapping a semiconducting tape or using a semiconducting heat source. A shrink tube made by heating and shrinking is placed in a mold, and after heating the mold to a predetermined temperature, insulating material heated to an appropriate temperature is injected and molded using, for example, a kamide machine. It will be done.

In such prior art, the insulating materials extruded by the extruder are generally highly viscous and require a considerable extrusion force, and the insulating materials are not easily extruded at the interface between the surface of the cable element covered by these materials and this material. Adhesiveness remains a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a connection part of an insulated cable that allows easy extrusion of the insulating material and has excellent adhesiveness to various elements of the insulated cable.

According to the present invention, the above-mentioned object is achieved by first injecting the insulating material into the connecting part of the cable with a relatively low melt index when extruding the insulating material after placing the conductor connecting part of the insulated cable in the mold. The material is sprayed to form a relatively thin layer so that at least the cable elements are covered by the material, and then extruded and injected at a relatively high melt index to coat the trailing section. The figure is formed by molding.

Based on the drawings below, cross-linked polyethylene insulated cable (
An embodiment of the present invention will be described using a CV cable (hereinafter referred to as a CV cable) as an example. FIG. 1 is a schematic partial cross-sectional view of an example of an apparatus for carrying out the method of the present invention, in which the ends of a CV cable are suitably processed to expose conductors, and these conductors are connected using conductor connection tubes. A semiconductive polyolefin inner semiconductive layer 2 is formed thereon.

Furthermore, the melt index at the cable connection is 0,
Thin layers 1, 0 are formed by spraying 6 to 3.5 (1 skin inch) of polyolefin insulation material and the connections thus formed are placed in molds 3, 4. An extruder 6 is connected to the lower mold 3 via a separating and cutting device 5.
Furthermore, a crosslinking agent injection device 7 is suitably connected.

The upper mold 4 is provided with a plurality of overflow holes 9 and a ram 8 filled with the overflow.

The molds 3 and 4, which house the connecting parts inside, are heated with a suitable heating device (
extruder 6 after being heated to a predetermined temperature by
Melt index is 5.0 (evening/1 仇njn)
The above polyolefin insulation material is extruded and injected.

A crosslinking agent (organic peroxide) is added by the injection device 7 during extrusion injection of this material with a large melt index.
When the inside of the mold is completely filled with the material having a high melt index, the excess material flows out from the overflow hole 9, and the material also enters the ram 8. In this state, the injection of the insulating material by the extruder is stopped, and at the same time, pressure is applied by the ram 8 to effect crosslinking, and then the entire mold is formed to form the cable connection part. By doing so, the material with a low melt index is present at the interface between the cable insulation and the material with a high melt index, improving the adhesion and facilitating crosslinking, and the extrusion itself is facilitated. become.

The method of the present invention has been explained above regarding CV cables.
Not limited to V-cables, the method of the present invention can be applied to any rubber or plastic insulated cables.

[Brief explanation of drawings]

FIG. 1 is a schematic partial sectional view showing an example of an apparatus for carrying out the method of the present invention. 1...Insulated cable, 2...Conductor connection part,
3, 4... Mold, 5... Separation sliding door device, 6
...Extruder, 7...Crosslinking agent injection device, 8...
- Ram, 9... Overflow hole, 10... Thin layer of low melt index material. spear figure

Claims (1)

[Scope of Claims] 1. A method of forming a connection part of an insulated cable by extruding an insulating material that is the same as or similar to the insulator of the insulated cable using a mold at a predetermined temperature, which has a relatively low melt index. The insulating material having a relatively high melt index is sprayed in advance around the connection portion to form a thin layer, and then the insulating material having a relatively high melt index is extruded into the mold and molded. A method of forming a connection part of a rubber or plastic insulated cable. 2. The insulated cable is a cross-linked polyethylene insulated cable, and the insulating material is polyolefin and has a melt index of 0.6 to 3.5 at initial injection.
2. The method for forming a connection portion of an insulated cable according to claim 1, wherein the melt index in the next injection is 5.0 g/10 min or more.