JPS59169307A - Method of forming rubber/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 molding rubber-plastic cable connections, that is, intermediate and terminal connections of cables, and relates to a method for molding rubber-plastic cable connections with good performance. . Conventional methods for forming rubber/plastic insulated cable connection parts, that is, cable terminations and intermediate connection parts, are as follows, taking the intermediate connection part as an example.

That is, first, shave the ends of the two cables to be connected into a pencil point shape, connect the exposed conductors with a compression sleeve, etc., and then use a semiconductive shrink tube or the like to
forming an inner semiconducting layer;

Then, on top of the internal semiconducting layer of the connection part and the cable ° insulation (penciling part), cover the desired mold, and into the mold, insulating composition, e.g. In such a case, a semiconductive composition, such as a semiconductive horizontal filler, is injected using an extruder or the like to form a reinforcing insulating layer at the cable connection portion. If crosslinking of the reinforcing rim layer is required, this can be done by heating the mold to a temperature necessary for crosslinking or by using a suitable crosslinking mold (not shown).

However, such a conventional method for forming a cable connection part has the following problems.

That is, after injecting an insulating or semiconductive composition into the mold, the mold was opened, and the resulting cable connection was subjected to a breakdown test, resulting in dielectric breakdown with a low breakdown value. When we looked at the fracture hole, we found that a large void had formed in the rising part of the penciling slope of the insulator of the connected cable, and water had accumulated in this void, and the fracture was progressing from this void. .

As a result of our earnest efforts to elucidate this phenomenon, the inventors found that
This phenomenon occurs when the mold is heated to a temperature suitable for the extrusion or injection temperature of the composition such as the resin after the mold is covered, but the moisture that has adhered to the surface of the cable insulator is removed from the mold. It is assumed that this is because moisture trapped in the air condenses on, for example, the cable conductor, which is a metal body with a relatively low temperature.

Based on the above estimation and as a result of intensive research, the present invention has found that in order to prevent the generation of the above-mentioned voids, the relative humidity should be adjusted to io
It was discovered that dew condensation on the cable could be prevented by reducing the amount to less than 0%, and the present invention was completed.

That is, as shown in FIG. 1, the present invention provides a method for coating and molding the conductor connecting portions 8 of the rubber/plastic cables (A) and (B) to be connected with a semiconductive composition or an insulating composition 2. After covering the desired molding die δ on the cable conductor connection portion 8 and its vicinity la, and before injecting the semiconductive composition or the insulating composition 2 into the molding die 8, and It is characterized in that the space 4 covered by the molding die 3 is dried to a relative humidity of less than 100% during injection.

In the method of the present invention, there are various ways to reduce the relative humidity of the space 4 covered by the molding die 8 to less than 100%. After heating the cable conductor 6 and the inner and outer conductive layers 7 to a temperature of 90°C or less by appropriate means,
A method of immediately covering the molding die 8.

That is, before covering the molding die 8, the conductor connection part 8, pencil ring part 9, etc. covered by the molding die 8 are heated to 9°C or less to remove moisture adsorbed on their surfaces. In the case of the method, the heating temperature was limited to 90'C or less.
This is because if the load exceeds 1.0, the rubber/plastic cable insulator 5 will easily be heated and deformed by the load of the conductor 6.

Another method is to
There is a method in which a desired mold 8 is covered on top of the mold 8, and then the inside of the mold δ is replaced with dry gas0. In other words, after the mold 8 is covered, the inside of the mold δ is dried. The inside of the molding die 8 is dried by replacing with gas. The type of dry gas is not particularly limited, but nitrogen gas and dry air are preferred from the viewpoint of ease of handling, and dry air is preferably used during construction at construction sites, particularly in manholes. As a gas replacement method, the extruder 10 of the molding die/mold 8 is used.
Possible methods include injecting gas from the resin injection hole 11 according to the invention. As a means for drying the gas, there are methods such as supplying the gas through a commercially available drying gas or a dryer such as molecular sheep.

Still another method is to cover the cable conductor connection portion 8 and its vicinity la with a desired mold 8, and then contain a desiccant (not shown) in the mold 8. .

That is, a desiccant is placed at an appropriate location on the mold 8 to maintain the mold 8 in a low-humidity atmosphere. Possible methods include creating a desiccant container at a suitable location within the mold 8, or placing the desiccant in a suitable container and placing it inside the mold 8.

Still another method is to use a desired molding die 8 in which a portion of the mold 8 communicates with the outside air so that the air inside the mold can be easily exchanged with the outside air.

That is, the highly humid air inside the mold 8 is pushed out together with resin injection to prevent dew condensation 3 inside the mold a, and an overflow hole (
(not shown).

The method of the present invention is not limited to the above method, but the initial effect can be obtained by reducing the relative humidity in the molding die 3 to less than 100 degrees using an appropriate method.

The present invention will be further described below with reference to Examples and Comparative Examples.

Comparative Example 66 After cutting both ends of a KV eV 250- cable into a pencil point shape, and connecting the exposed conductors with each other with a compression sleeve, the internal semiconductive layer 7 was formed using a semiconductive heat shrink tube. Molded. After that, the formed internal semiconducting layer 7
A molding die 8 is installed on top, and a polyethylene resin (product name: HFDJ 4201 E manufactured by Nippon Unicar Co., Ltd.) 2
was injected into the mold 8, and at the same time as the injection was completed, the mold 8 was heated to crosslink.

After crosslinking, a semiconductive raw rubber tape was wrapped as an external semiconductive layer and subjected to an alternating current destructive test, which resulted in failure at 120 KV. When the fracture hole was observed, it was found that the inner semiconducting layer 7 and the insulating layer 5
A void existed at the interface, and destruction started from there. Also, water had accumulated in the voids.

Example I As in the comparison above, the conductor connection part 8 of the 66 KV OV 250- was covered with a molding die 8 as shown in FIG. After drying, the same resin as the clam used in the comparative example (HFDJ 4
201 K) was injected into the mold 8 through the injection port 11 using the extruder 10, and then heated and crosslinked to form a cable connection part with a rounded surface.The AC breakage value was measured and The presence or absence of voids was investigated. The results are also listed in Table 1.

As is clear from the table, according to the method of the present invention, it is possible to prevent the generation of voids at the interface between the internal semiconducting layer and the insulator, and to obtain a cable connection portion with significantly improved AC breakdown characteristics.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating a process according to an embodiment of the present invention. A, B...a [rubber/plastic cable Ia
... Near the cable connection part 1 2 ... Semiconductive composition or insulating composition δ ...
Molding mold 4...Space covered by molding die 8 5...Cable insulator 6...Cable conductor 7...Inner and outer semiconducting layers 8...Conductor connection portion 9...・Penciling section
10...Extrusion state 11...Resin injection port. Patent applicant Furukawa Electric Co., Ltd.

Claims (1)

[Claims] L: When molding a continuous part of a four-piece connecting part of a rubber/plastic cable with a semiconductive composition or an insulating composition, a desired molding is performed on the cable conductor joint part and its vicinity. After covering the mold, before and during injection of the semiconductive composition or insulating composition into the mold, dry the space covered by the mold to a relative humidity of less than 100%. A method for molding a rubber-plastic cable connection part characterized by: Warm the cable insulator, cable conductor, and inner and outer cable layers in the space to be covered with the desired mold at a temperature of 90°C.
A method for molding a plastic cable connection part includes heating the mold, immediately covering the mold, and injecting a semiconductive composition or an insulating composition into the mold. & After covering the cable conductor connection portion and its vicinity with a desired mold, and after replacing the inside of the mold with dry gas, immediately fill the mold with a semiconductive composition or an insulating composition. A method for molding a rubber/plastic cable connection part according to claim 1, characterized in that the composition is injected. Table: After covering the cable conductor connection portion and its vicinity with a desired mold, a desiccant is contained in the mold, and a semiconducting composition or an insulating composition is injected into the mold. Method for molding a rubber-plastic cable connection section according to claim 1, characterized in that: (5) a desired molding die in which a part communicates with the outside air so that the internal air can easily be exchanged with the outside air; A patent characterized in that a semiconducting composition or an insulating composition is injected into the forming mold by covering the cable connection portion and its vicinity.
How to form a pull connection.