JPS5810383A - Method and device for forming connector of insulated cable - 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 of forming connections in rubber or plastic insulated cables.

Rubber or plastic insulated cables are often used in splices, but the deterioration of electrical properties due to splices is a serious problem, especially when used for very high electrons. To solve this problem, the connection is conventionally made by exposing 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 over the conductor connection. By heating this under pressure, the insulating layer of the cable and this reinforcing insulating layer are integrated. This reinforcing insulating layer is made of the same or at least as good a material as the insulating material of the cable, so as not to impair the electrical properties of the cable and to allow the dimensions of the connection itself to be as small as possible. It is generally formed by molding using a similar material.

Molds using such insulating materials generally include an internal semiconducting layer on the conductor connections, for example, by winding semiconducting tape or heat-shrinking semiconductive heat shrink tubing. After the mold is preheated to a predetermined temperature using an appropriate heating device, an insulating material heated to an appropriate temperature using an extruder or the like is injected.

In such conventional methods, air bubbles often remain in the molded insulating layer due to the cooling of the mold after injection molding, which affects its thermal properties.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for solving the problem of bubble formation in conventional methods of forming connections of insulated cables.

It has been found that the cause of residual air bubbles in the insulating layer that is molded is mainly due to the cooling method of the mold after molding. In other words, if the material injection into the mold is stopped after the extrusion injection of insulating material is completed, and then the mold is immediately cooled, many air bubbles remain. It was found that the amount of remaining air bubbles was significantly reduced.

According to the present invention, insulating material is injected into the mold using an extruder, and a portion of the overflow is introduced into a small ram heated to a slightly higher temperature than in the extruder [7]
After the injection by the extruder is completed, the mold is cooled in stages while pressurizing the inside of the mold via the insulating material in the ram. By applying VC in this manner, the problem of bubbles remaining in the insulating layer after molding is substantially eliminated.

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a schematic partial sectional view showing an example of an apparatus for carrying out the method of the present invention. In the figure, the insulated cable to be connected is a cross-linked polyethylene insulated cable (
Taking a CV cable (hereinafter referred to as a CV cable) as an example, after shaping the end of the CV cable 2 into a desired shape to expose the conductors, and connecting these conductors appropriately, for example, a semiconductive polyolefin heat-shrinkable tube 7' or a semiconductive The internal semiconducting layer 1 is formed by a polyolefin pre-molded unit or the like.

After that, the connection part prepared in this way is inserted into the upper and lower molds 6.
．． Place it within 4.

Does the above mold have at least one piece? I=having an inlet hole 6 and having a plurality of overflow holes 7;

This injection hole 6 connects to a small ram 8. On the other hand, lower mold 4
has an injection hole 5 which is connected to the extruder 11 via a suitable isolation valve 16.

The ram 8 is filled with an insulating material 5 which is the same as or at least similar to the insulating material of the insulated cable, which is an overflow of insulating material due to extrusion, and this insulating material is heated by a heating device 9. For example 100-2
Heated to about 50C and nitrogen gas or SF
It is pressurized by an inert gas source 10 such as 6 gas.

An auxiliary heating device 14 is provided at a position close to the mold of the CV cable placed in the mold filter 4 to heat that part to about 60 to 1 ootr, and a main heating device 15, 16 is further provided in the mold. .17 is provided as shown. This main heating device is for heating the mold filter 4 to a predetermined temperature of about 80 to 200'C, for example, and the heating device 14.
15, 16, and 17 can be controlled independently.

The method of the present invention is carried out as follows. First, in the illustrated state, the heating devices 14, 15, 16, 17 are operated to raise the mold temperature to the above value and maintain it. Valve 13 is then closed and extruder 11 extrudes, for example, a polyolefin insulating material through inlet 5 until it flows out through overflow hole 7 and into ram 8 through inlet 6. At the same time, the heating device 9 of the ram 8 heats the insulating material flowing into the ram to a temperature higher than the mold temperature.

In this state, by operating the valve 16, the extruder 1
1 from the lower mold 4 and, by operation of appropriate valves, introduces inert gas from the gas source 10 into the ram 8, pressurizing the insulating material therein and causing it to flow back into the mold.

Simultaneously with this reverse flow, cooling of the mold is started by deenergizing the auxiliary heating device 14 and the outermost main heating device 15, and then at a predetermined point turning on the intermediate main heating device 16 and then the innermost main heating device. The mold is cooled by sequentially deenergizing the heating device 17.

By doing this, the insulation material in the mold is pressurized by the relatively high temperature insulating material by the ram 8, making it possible to fill the mold more densely and at the same time gradually cooling the mold.
The possibility of bubble generation is minimized, and a highly reliable insulating layer can be formed. Further, according to the present invention, management is easy because there is no need to use extrusion until the cooling is completed, and furthermore, since the insulating material is directly pressurized with an inert gas in the ram, the work is easy.

In addition, in order to reduce the amount of material extruded by the extruder, it is also possible to pre-form a split shape as shown by the broken line 20 using the same insulating material, place it in the mold, and then form the connection part as described above. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a schematic partial sectional view of an apparatus for carrying out the method of the invention. 2-m-insulated cable, filter, 4-m-mold, 5-m-extrusion inlet, 6--overflow and inlet, 7-
--1 overflow hole, 8-m-ram, 10-m-gas source, 11--extruder, 13-m-separation valve, 9.14.
15.16.17---Heating devices. Procedural amendment (spontaneous) 57.6.16 Showa year, month, day 1, case description 1978 Patent Application No. 106693 2 Title of invention Method and device for forming a connection part of an insulated cable a Person making the amendment t Agent 〒100 1 Tsume Takuze (216) 1611 (Major Representative) Column for detailed explanation of the invention of the specification to be amended. Contents of amendment (1) The following sentence is inserted between line 17 and line 18 on page 5 of the specification. "Instead of the inert gas source 10, it is also possible to pressurize with air using any compression device." Above 2-

Claims (1)

[Claims] 1. A connection part for connecting an insulated cable is placed in a mold equipped with a heating device, and an insulating material that is the same as or at least similar to the insulating material of the cable is extruded using an extruder. In this method, at least a portion of the overflow of the insulating material upon completion of extrusion is introduced into a ram using at least one inert gas as a pressurizing source and heated to a temperature higher than the mold temperature. The rubber or plastic is heated, the extruder is separated from the mold, and the mold is cooled in stages while the ram is operated to pressurize the inside of the mold via the overflow. Method of forming connections of insulated cables. 2. A mold that accommodates at least the conductor connection part of the insulated cable, an extruder selectively connected to this mold, and at least one ram connected to this mold and using an inert gas as a pressurizing source. , a heating device capable of heating the mold to a predetermined temperature and gradually canceling the heating, and a heating device capable of heating the ram to a higher temperature than the mold. Apparatus for carrying out the method described in Section 1.