JPS63131481A - Method of molding plastic insulated cable joint - 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 (Industrial Application Field) The present invention relates to a method for molding an insulating layer of a connecting portion of a plastic insulated cable (hereinafter referred to as a Cv cable).

[Conventional technology]

Since Cv cables are easy to handle and maintain, they have recently come to be widely used as high-voltage cables for main trunk lines. The straight connection part of this Cv cable can be formed by wrapping an uncrosslinked polyethylene tape made of the same material as the cable insulator to form an insulating layer and molding it by heating, or by extrusion molding a molten polyolefin insulator, etc. has been put into practical use.

In the case where the connection part of the Cv cable is wrapped with chemically cross-linked polyethylene tape to form an insulating layer and then heated and molded, the cross-linking reaction occurs after the mold tape melts, so the weight of the polyethylene tape causes It inevitably sags, and the insulating layer ends up being molded eccentrically. Therefore, in order to prevent this, a method has been adopted in which a metal mold 6 is fitted around the outer periphery of the connecting portion 1 of the Cv cables 2, 2' and molding is performed, as shown in FIG. That is, the tip of the CV cable 2.2' is ventilated to expose the connecting conductors 3, 3', and the connecting conductors 3, 3' are butted and covered with a conductor connecting screen 4 to form an electrically integrated CV cable. An insulating layer 5 is formed by wrapping an unreacted crosslinked polyethylene tape around the connecting portion 1. Then, a metal mold 6 that matches the outer peripheral shape of the insulation M5 is fitted, and heating is performed from outside using a heater or the like. However, even with this method, the thickness of the insulating layer 5 is not uniform, so expansion due to heating of the polyethylene tape may cause deformation of the Cv cables 2, 2' and cracks inside the joint part 1, making it difficult for ultra-high voltage applications. could not be used.

Therefore, as shown in FIGS. 4 and 5, the insulating layer 5 of the CV cable connection part 1 is similarly formed by wrapping an unreacted cross-linked polyethylene tape, and the outer periphery is held down with a heat-shrinkable tube 7. A method has also been adopted in which a narrow metal plate 8 is placed vertically along the outer periphery of the connecting portion insulating layer 5, fixed with a presser tape 9, and heated and molded. Also 1
Although not shown, a method has also been adopted in which the cable connection part l is immersed in a liquid having a specific gravity equal to that of polyethylene, heated, and molded.

(Problems to be Solved by the Invention) However, in the conventional technology described above, the method using the metal mold shown in Figure 3 causes deformation of the cable and cracks inside the joint due to expansion of polyethylene. However, it could not be used for ultra-high voltage cables, and was limited to connections for low-voltage cables such as power distribution lines. Also,
Although the method shown in FIGS. 4 and 5 is an effective method, it is necessary to wrap the presser tape 9 strongly in order to obtain a sufficient effect of wrapping the metal plate. Therefore, when the metal plate 5 is brought into contact with it, its outer shape is deformed into a polygonal shape. Further, the effect cannot be obtained with a thin metal plate that does not undergo deformation. The biggest problem is that, as shown in Figure 6, when plates are attached to the rising parts of both ends of the connection insulator 5, the unbalanced presser pressure causes the polyethylene resin to undergo a crosslinking reaction, as shown by the arrows. The problem is that a flow occurs, which adversely affects the withstand voltage performance of the joint part.

The present invention has been made in view of these drawbacks, and is an improved mold joint that prevents the eccentricity of the mold joint portion during mold crosslinking work and manufactures a mold joint that has excellent withstand voltage performance. The purpose of the present invention is to provide a mold forming method.

[Means and effects for solving the problem] In the present invention, a plurality of metal plates are brought into contact with the lower half or the lower circumference of the flat part of the outer periphery of the insulating layer formed in the mold joint part. The metal plate is supported at a position away from the joint, and is heated from the outside and molded. Therefore, the melted resin does not flow in the insulating layer to be molded due to unbalanced pressing pressure, and molding can be performed without eccentricity.

(Example) Hereinafter, an example of the molding method for a plastic insulated cable connection part of the present invention will be described based on the drawings.

FIG. 1 is a side sectional view of the cable connection portion, and FIG. 2 is a sectional view taken along the line ■-■ in FIG. That is, in this invention,
A plurality of narrow metal plates are placed vertically along the lower side of the flat part of the connecting portion insulating layer 5 and molded.

The molded connection part 1 of the Cv cable 2.2' is connected to the third
Similar to the prior art shown in the figure, the cable 2.2' is formed by penciling, exposing the conductor connection portion 3.3' at the tip, abutting against each other, and fitting the conductor connection sleeve 4 thereon. An insulating layer 5 is formed by wrapping an unreacted east end polyethylene tape around this connection part 1.
, 5a', and the outer periphery of the central conductor connection sleeve 4 has a chevron-shaped cross section with a horizontal portion 5b that is thicker than the diameter of the cables 2, 2'.

Then, a thickness of 0.5~
Narrow metal plate 10, 1 with a slight deflection of about 2cm
0. ---- along vertically. These metal plates 10, 10.
Both ends of ---- are supported horizontally along the circumference of the Keetz by a support pedestal 11.11 at a place detached from the cable connection part 1, and a heater (not shown) is wound around the outside of this to heat and mold. let

When the heater is heated, the surface layer of the insulating layer 5 first melts and a crosslinking reaction occurs. At this time, the middle and inner layers of the insulation M5 are still in a solid state. Thereafter, as the heating progresses, the middle and inner layers of the insulating layer 5 melt and cause a crosslinking reaction to be molded, but as the insulating layer 5 melts, a force tends to be eccentric due to its own weight. By supporting this force with a slight force due to the deflection of the metal plate 10.10--1, the insulating layer 5 does not become eccentric and its outer periphery is naturally maintained in a shape close to roundness. It will be molded. As a result, good molding is achieved without any unnecessary stress being applied to the insulating layer 5, so that the electrical characteristics of the connecting portion 1 are maintained in good condition without any damage. .

In the above example, the metal plate is placed vertically around the outer periphery of the lower flat part of the insulating layer 5, but it is also effective to perform molding by placing the metal plate vertically around the lower half of the flat part. (It's the same.

(Effects of the Invention) As explained above, in this invention, eccentricity can be prevented without applying extra stress to the insulating layer to be molded, so a mold joint with excellent insulating properties can be easily produced. I can do something.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of an apparatus used in a molding method for a plastic insulated cable connection part showing one embodiment of the present invention, and FIG. 2 is a sectional view taken along line nn in FIG. 1 above. , Figures 3 to 5 show the apparatus used in the conventional molding method for plastic insulated cable connections, Figure 3 is a side sectional view of the one using a mold, and Figure 4 is a metal molding method. Figure 5 is a side sectional view of what holds the board vertically.
A cross-sectional view taken along the line nn in the figure, and FIG. 6 is a partial side cross-sectional view for explaining the state of the resin during molding. 1--------CV cable connection part 2.2'
---CV cable 5-----Insulating layer 5b-------One flat part 10---One metal plate 11--One----- -Support frame

Claims (1)

[Claims] In a method of molding a mold joint part for a plastic insulated cable by extrusion or tape wrapping, during crosslinking work, the lower half or lower 1/3 of the flat part of the outer periphery of the insulating layer formed in the joint part Mold-forming of a plastic insulated cable connection part, characterized in that a plurality of metal plates are brought into contact with each other, these metal plates are supported at positions apart from the joint part, and the mold-forming is performed by heating from the outside. Method.