JPH0442887B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of forming a cable connection part by injection molding.

[Technical Background of the Invention] Conventionally, as a method of forming a connection part of a cross-linked polyethylene insulated cable, a split mold is fitted to the outer periphery of the conductor connection part of a cross-linked polyethylene insulated cable which has been stripped in stages and conductor connections have been made. After press-fitting a crosslinkable polyolefin composition heated and melted into the cavity of this mold to form an insulating mold, the mold is cooled and solidified, and the mold is removed. The insulator mold is cross-linked by heating again to form an insulator connection part, and then after this insulator connection part is sufficiently cooled, a semiconductive polyethylene tape is wrapped around the outer periphery and this is heat-fused, or Alternatively, a method is known in which a semiconductive polyethylene heat-shrinkable tube is attached and the tube is heat-shrinked to form an outer semiconductive layer.

[Problems in the Background Art] However, in such conventional methods, it is necessary to repeat the formation of an insulator mold, the subsequent crosslinking, and the formation of an outer semiconducting layer, and each time heating and cooling, which slows down the manufacturing process. The problem was that the process was complicated and took a long time, especially cooling.

[Object of the Invention] The present invention has been made in order to solve these drawbacks, and it is an object of the present invention to provide a method for easily forming cable connections with excellent electrical and mechanical properties in a short time. That is.

[Summary of the Invention] That is, the method for forming a cable connection part of the present invention involves step-peeling a split mold having a cavity corresponding to the shape of the cable connection part to be molded and having a resin injection port communicating with the cavity. the outer periphery of the conductor connection portion of the rubber/plastic insulated cable to which the conductor connection has been made, and press-fitting a heated and melted crosslinkable insulating rubber/plastic composition into the cavity from the resin injection port; Next, after sealing the resin injection port, the split mold is heated to crosslink the insulating rubber/plastic composition in the cavity, and then the surface of the crosslinked composition and the inner surface of the split mold are heated. The composition is cooled until a gap is formed between which a semiconductive layer can be formed, and then the semiconductive rubber/plastic composition is press-fitted into the gap through the resin injection port and solidified by cooling. It is said that

[Embodiment of the Invention] The details of the present invention will be described below with reference to an embodiment shown in the drawings.

In the figure, reference numeral 1 has a spindle-shaped cavity 2 corresponding to the shape of the cable connection part to be molded, and a cylindrical insulator grip part 3 connected to both ends of the cavity.
It also shows a split mold for molding a cable connection part that has a built-in heater h. A part of the center of this split mold 1 has a resin pressure inlet 5 that can be sealed with a shutoff valve 4.
is provided, and degassing ports 6, 6 are provided on both sides of the resin injection port 5 to release the air remaining in the cavity 2 and to allow the press-fitted rubber/plastic composition to overflow. . Valves 7, 7 that can be opened and closed are provided at the outer opening ends of these deaeration ports 6, 6. Furthermore, heat shield adapters 8 made of heat-resistant plastic are fitted to both ends of the insulator gripping part 3 to isolate the split mold 1 from the cable's external semiconductive layer.

The method of the present invention is carried out using such a split mold 1, for example, as follows.

First, the rubber/plastic insulated cable to be connected, for example, the cross-linked polyethylene insulated cable 9,
9' is stripped in steps, and the cable conductor 10,
10' are connected by a connecting sleeve 11, and a cross-linked semi-conductive layer 12 is formed using a semi-conductive heat-shrinkable tube made of cross-linked rubber or plastic such as cross-linked semi-conductive polyethylene. fit. Next, the insulating polyolefin composition containing a crosslinking agent is extruded into the split mold 1 by a conventional injection molding method to form an insulator mold 13.

That is, after fully opening the on-off valves 7, 7 of the degassing ports 6, 6, an extruder (not shown) for extruding the insulating polyolefin composition is placed at the outer open end of the resin press inlet 5 of the split mold 1. The extrusion port is connected, and the cavity 2 is filled with an insulating polyolefin composition containing a crosslinking agent that has been heated and melted by the extruder. At this time, the cable conductors 10 and 1 are
Infiltration of the insulating polyolefin composition into the 0' strand gap is prevented. When the insulating polyolefin composition is filled into the cavity 2 and begins to flow out from the two deaeration ports 6, 6, the on-off valves 7, 7 of these deaeration ports 6, 6 are closed, and when the composition is sufficiently pressurized. The resin press inlet 5 of the split mold 1 is sealed by the shutoff valve 4 .

After that, the heater h is energized to heat the split mold 1, and if necessary, the induction coil 14 is wound around the heat-insulating adapter 8, and an alternating current is applied to inductively heat the cable conductors 10, 10' to insulate them. body mold 1
3 is raised to a predetermined crosslinking temperature, for example, about 200° C., and the insulator mold 13 is crosslinked under pressure. Note that heating may be performed by disposing a band heater around the outer periphery of the split mold 1 and applying electricity to the band heater.

After the insulator mold 13 is sufficiently crosslinked by continuing heating for a predetermined period of time in this manner, cooling is started while the pressurization is continued.

The outer diameter of the insulator mold 13 within the cavity 2 becomes smaller than the inner diameter of the cavity 2 due to thermal contraction as it cools. When the surface of the insulating mold 13 has cooled to a temperature of about 140 to 150°C, which creates a gap where a semiconducting layer can be formed between the inner surface of the mold 1 and the surface of the insulating mold 13, the resin injection port is opened. The extrusion port of an extruder (not shown) for extruding a semiconductive polyethylene composition is connected to the outer open end of the mold 5, and the semiconductive polyethylene composition heated and melted by this extruder is transferred to the split mold 1 in the cavity 2. The gap between the inner surface of the insulator mold 13 and the insulator mold 13 is press-fitted and filled.

At this time, in the same way as when filling the insulating polyolefin composition for molding the insulator mold 13,
Leave the on-off valves 7, 7 of the deaeration ports 6, 6 fully open,
When the semiconductive polyethylene composition begins to flow out, the on-off valves 7, 7 are closed.

Next, cool the split mold 1 and mold the cavity 2.
solidify the semiconductive polyethylene composition within. 80
After solidifying the conductive polyethylene composition by cooling it to a temperature of about 100° C., the split mold 1 is opened, the outer shape is adjusted by finishing processing, and the outer semiconductive layer 15 is provided around the outer periphery of the insulating mold 13. The cable connection section is completed.

If an extruder dedicated to each rubber/plastic composition is used as in the above embodiment, mixing of the extruded materials can be avoided and the electrical characteristics of the cable connection portion will not be degraded.

In addition, in the above embodiment, an example in which the present invention is applied to the formation of a connection part of a crosslinked polyethylene insulated cable was explained, but the present invention is applicable not only to the formation of a connection part of a crosslinked polyethylene insulated cable shown in the above embodiment, but also to It is also widely applicable to forming connections for other crosslinked rubber/plastic insulated cables, such as crosslinked ethylene and propylene insulated cables.

[Effects of the Invention] As explained above, according to the method of the present invention, the formation of an insulating mold, its crosslinking, and the formation of an external semiconducting layer can be performed in one mold, and heating and cooling are only performed once. Since the cable connection part is formed through a simple work process, the time is significantly reduced compared to the conventional method, the work is easy, and the characteristics of the resulting cable connection part are excellent.

[Brief explanation of drawings]

The drawings are longitudinal sectional views for explaining one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Split mold, 2... Cavity, 3... Insulator grip part, 4... Shutoff valve, 5... Resin injection port,
6... Deaeration port, 7... Open/close valve, 8... Heat shield adapter, 9, 9'... Crosslinked polyethylene insulated cable, 10, 10'... Cable conductor, 11... Connection sleeve, 12... Crosslinked half Conductive layer, 13... Insulator mold, 14... Induction coil, 15... External semiconducting layer.

Claims (1)

[Scope of Claims] 1. A split mold having a cavity corresponding to the shape of the cable connection part to be molded and a resin injection port communicating with the cavity is stripped in stages to make a rubber/conductor connection. A cross-linkable insulating rubber/plastic composition that was heated and melted was fitted onto the outer periphery of the conductor connection portion of the plastic insulated cable and press-fitted into the cavity from the resin injection port, and then the resin injection port was sealed. After that, the split mold is heated to crosslink the insulating rubber/plastic composition in the cavity, and then a semiconductive layer can be formed between the crosslinked surface of the composition and the inner surface of the split mold. Cooling the composition until a gap is formed, then press-fitting a semiconductive rubber/plastic composition into the gap through the resin injection port,
A method for forming a cable connection portion, characterized by cooling and solidifying it. 2. Claim 1, in which the insulating rubber/plastic composition and the semiconductive rubber/plastic composition are press-fitted using separate extruders, respectively.
Method of forming cable connections as described in Section 1.