JPH0410285B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objects of the Invention] The present invention relates to a method for producing polyolefin bellmouth.

There are two ways to configure the termination connection for CV cables: using an oil-immersed capacitor and using a bell mouth and insulating oil. The latter option is considered practical.

In this way, the method of shielding the electric field using a bell mouth is considered to be extremely useful as a means of constructing a terminal connection part for CV cables, but in this case,
The bell mouth needs to be configured to absorb the thermal expansion and contraction of the CV cable. To satisfy this requirement, it is basically best to construct the bell mouth with polyolefin, which is the same material as the insulation of the CV cable.

However, large bell mouths made of a large amount of polyolefin are extremely difficult to manufacture and have not yet been put to practical use. For this reason, there is an urgent need to establish a method for producing a bell mouth using polyolefin, especially a method for producing a large bell mouth using a large amount of polyolefin, and a new technical idea is required.

An object of the present invention is to provide a method for manufacturing a polyolefin bellmouth suitable for a terminal connection part for an ultra-high voltage CV cable.

[Summary of the Invention] That is, the gist of the present invention is to prepare a special mold in the shape of a bell mouth, directly connect an extrusion device to this mold, extrude and mold polyolefin, process and finish it, and finally The purpose is to produce a polyolefin bellmouth by conducting a conductive layer treatment.

[Example] Fig. 1 is a side view showing a partially sectional view of an extrusion molding machine used in carrying out the present invention, and Fig. 2 shows a manufacturing process of an embodiment of the present invention. It is a block diagram.

The mold of the molding machine used to manufacture polyolefin bell mouth consists of an upper mold 1 and a lower mold 2, inside which is a core 3 and outside of this core 3, which is integrated with the core 3. An overflow nozzle 5 is provided on the outer wall of the expansion absorber 4, and heaters 6 are provided on the outer periphery of the upper mold 1 and the lower mold 2 and on the inside of the core bar 3, respectively.
The mold thus constructed is directly connected to an extrusion device 8 via a connecting pipe 7, and a polyolefin replenishment hopper 9 is attached to this extrusion device 8. The inflatable absorbent body 4 is made of rubber or plastic such as silicone rubber, ethylene-propylene rubber, or fluorocarbon resin, and is preferably made of foamed material of these rubbers or plastics.

Next, the manufacturing process of the present invention will be explained.

Step () For example, molten polyolefin containing a crosslinking agent heated to a predetermined temperature of 100 to 140° C. is extruded in a molten state from an extrusion device 8 through a connecting pipe 7 and filled into a mold. After that, overflow nozzle 5
When the molten polyolefin comes out, the operation of the extrusion device 8 is stopped, the connecting pipe 7 is removed, and a sealing plate (not shown) is fixed to the mold.

Step () The heating heater 6 of the mold is raised to a crosslinking temperature of, for example, 180 to 250°C to thermally crosslink the polyolefin, and then the overflow nozzle 5 is passed into the mold to e.g. 2 to 20 kg/ ^cm2. The polyolefin insulator 10 is formed by cooling the crosslinked molten polyolefin while applying gas pressure. Thereafter, the core metal 3 is extracted from the cross-linked polyolefin insulator 10, and the upper mold 1 and the lower mold 2 are further removed.

At this time, due to the presence of the expansion absorber 4, the removal of the core bar 3 becomes extremely smooth. In addition, a heating heater 6 provided inside the core metal 3
As a result, the inside of the polyolefin insulator 10 is effectively heated, and therefore the entire large-sized polyolefin insulator 10 can be heated extremely smoothly.

Step () The thus crosslinked polyolefin insulator 10 is machined into a bell mouth shape.

Step () Finally, a semiconductive polyolefin is applied to the finished polyolefin bellmouth insulator 10 to form a conductive layer.

[Effect of the invention] The present invention has the following excellent effects.

(1) Since extrusion production is performed using a mold and an extrusion device 8 directly connected to the mold via a connecting pipe 7, a polyolefin bell mouth with excellent reliability and electrical properties can be manufactured with almost no foreign matter or voids. .

(2) It has an expansion absorber 4 on the outside of the core metal 3 and is integrated with the core metal 3, and further has heating heaters on the outer periphery of the upper mold 1 and the lower mold 2 and on the inside of the core metal 3, respectively. 6, the core bar 3 can be removed very smoothly, and the entire large polyolefin insulator 10 can be heated very smoothly, thus speeding up the manufacturing process. can.

(3) CV cable thermal expansion, heat absorption, ultra high voltage
We can manufacture polyolefin bell mouths suitable for CV cable terminations.

[Brief explanation of drawings]

FIG. 1 is a side view, partially in section, of an extrusion molding machine used in carrying out the present invention, and FIG.
FIG. 2 is a block diagram showing the manufacturing process of an embodiment of the present invention. 1; Upper mold, 2; Lower mold, 3; Core bar, 4; Expansion absorber, 5; Overflow nozzle, 6; Heater, 7; Connection pipe, 8; Extrusion device, 9; Hopper for replenishing polyolefin, 10; Polyolefin insulator (polyolefin bellmouth insulator).

Claims (1)

[Scope of Claims] 1. Consists of an upper mold and a lower mold, has a core metal inside and an expansion absorber integrated with the core metal on the outside of the core metal, and the upper mold and the lower mold have A step of directly connecting a mold provided with heaters on the outer periphery and inside the core metal to an extrusion device, and extruding and filling molten polyolefin containing a crosslinking agent heated to a predetermined temperature from the extrusion device into the mold. a step of heating the molten polyolefin to a predetermined crosslinking temperature to crosslink it; a step of cooling the crosslinked molten polyolefin while applying a predetermined pressure in a mold to form a polyolefin insulator; The process consists of processing and finishing the cross-linked polyolefin insulator into a bellmouth shape, and applying semiconductive polyolefin to the processed polyolefin/bellmouth insulator to form a conductive layer. A method for producing a polyolefin bell mouth characterized by: 2. The manufacturing method according to claim 1, wherein the expandable absorbent body is made of rubber or plastic such as silicone rubber, ethylene propylene rubber, or fluorocarbon resin. 3. The manufacturing method according to claim 2, wherein the rubber or plastic of the expandable absorbent body is made of a foam.