JPS59201377A - Method of forming cable connector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for forming cable connections by injection molding of crosslinkable rubber-plastic compositions.

[Technical Background of the Invention] Conventionally, a method using injection molding of a crosslinkable polyolefin composition has been known as a method for forming a connection portion of a crosslinked polyethylene cable.

In this method, a split mold is fitted around the outer periphery of the conductor connection part of a cross-linked polyethylene cable that has been stripped in stages and conductor connections are made, and a heat-melted crosslinkable plastic composition is press-fitted into the cavity of this mold. After forming an insulator mold, the insulator mold is cooled and solidified, the mold is removed, and the insulator mold is crosslinked by heating it again while pressurizing it in a pressure-type heating furnace.

[Problems with the Background Art] However, in such a conventional method, in the formation of an insulator mold and the subsequent crosslinking process, C1 heating and cooling are repeated, and the inner semiconducting layer and the outer semiconducting layer are If molding of the conductive layer is required, heating and cooling must be repeated, making the manufacturing process complicated and time-consuming, as well as degrading the electrical and mechanical properties of the cable connection. This was causing an increase in production costs.

Moreover, since cable connections are often made in narrow places such as tunnels, there is a strong desire to simplify the work T culm and perform the work with fewer tools. There were also drawbacks such as the need for a pressurized heating furnace for crosslinking in addition to the split mold for forming the joints.

[Object of the Invention] The present invention was made to solve these drawbacks, and provides a method that can easily form a molded connection part with excellent electrical and mechanical properties in a short period of 1 hour. This is what I am trying to do.

[Summary of the Invention] That is, the method for forming a cable connection part of the present invention includes a split mold having a cavity corresponding to the shape of the molded insulator connection part and a resin press-fit hole communicating with the cavity. is fitted onto the outer periphery of the conductor connection part of a rubber/plastic insulated cable with a cross-linked semiconductive layer formed on the conductor connection part by peeling off the conductor connection part in stages, and heated and melted into the cavity through the resin press inlet. After filling the split mold with a crosslinkable rubber/plastic composition and cooling the composition filled in the split mold to its solidification temperature while press-fitting the rubber/plastic composition, the resin injection port is closed. After sealing, the front split mold is heated to crosslink the rubber/plastic composition in the cavity, and a vacuum is drawn from the cable conductor side to allow volatile crosslinked products to pass through the crosslinked semiconductive layer. It is characterized by the fact that it is removed by

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

3- In the figure, reference numeral 1 denotes a spindle-shaped cavity 2 which is composed of an upper die 1a and a lower die 1b, and corresponds to the shape of the insulator connection part to be molded, and a cylindrical insulator gripping part 3 connected to both ends of the spindle-shaped cavity 2. This figure shows a split mold for molding a cable connection part, which has a built-in heater i.

A four part d is formed in the center of the mold 1a of the split mold 1, and a resin pressure inlet 4a and a resin discharge port 4b, which can be sealed by on-off valves Vl and V2, are opened in this recessed part d. Further, in the vicinity of both ends of the upper mold 1a, deaeration ports 5.5 are provided for discharging the air remaining in the cavity 2 and allowing the press-fitted polyolefin composition to overflow. 5.5 is provided with an on-off valve V3.

On the other hand, a split mold 1 is attached to both ends of the insulator gripping part 3 of the mold 1.
A heat shield adapter 6.6 made of heat-resistant plastic is fitted to isolate the cable from the cable insulation.

The method of the present invention uses such a split mold 1 and 4- For example, this is done as follows.

First, the rubber/bratic insulated cable to be connected, for example, the cross-linked polyethylene cable 7.7', is stripped, and the cable conductor 8.8' is connected by the connecting sleeve 9 using a conventional method. After forming the crosslinked semiconductive layer 10 using a half-11 heat-shrinkable tube, a split mold 1 is fitted around its outer periphery.

Also, one cross-linked polyethylene cable 7' to be connected
A sealing part 11 is formed at the end of the cross-linked polyethylene cable 7, and a vacuum pump 1 is connected to the end of the other cross-linked polyethylene cable 7 via an intake pipe 12.
Connect 3.

Next, the polyolefin composition mixed with a crosslinking agent is extruded into the split mold 1 through the resin injection port 4a to form the insulator mold 14 by a normal injection molding method.

That is, first, the on-off valve V1 of the resin press-fitting lower 'Ia is fully opened, the on-off valve V2 of the resin discharge port 4b is fully closed, and the on-off valves V3 and V3 of the deaeration port 5.5 are fully opened, and then The outer end of the resin injection port 5 of the mold 1 is connected to the extrusion port of an extruder (not shown), and the polyolefin composition containing a crosslinking agent heated and melted by this extruder is transferred to the cavity 2.
Replenish yourself within.

When the polyolefin composition is filled into the cavity 2 and begins to flow out from the deaeration port 5.5, the on-off valves V3 and V3 of these deaeration lTl15.5 are closed, and the on-off valve V2 of the resin discharge port/lb is closed. Open the cavity and continue filling the polyolefin composition. Ru.

After this, the press-fitting part from the resin press-fitting hole /Ia is pressed down to such a level that the polyolefin composition does not solidify in the middle of the process, and the polyolefin composition in the cavity 2 is constantly
'k(If/cj or more) Adjust the opening/closing degree of the on-off valve V2 of the resin discharge port 4b so that the internal pressure is applied to the -C resin discharge hole 4.
Adjust the flow rate of the composition discharged from b. The polyolefin composition filled in the cavity 2 is inserted into the resin press-fit hole 4.
The molten polyolefin composition gradually cools and solidifies from the portions away from a and the resin discharge holes 4b, and eventually flows only through the recesses d of the upper mold 2, but because of this flowing polyolefin composition, The polyolefin composition within the cavity 2 will be pressurized until it is completely solidified. During this time, the cable conductor 8 is
．． Infiltration of the polyolefin composition into the strand gaps of 8' is prevented.

In this way, when the temperature of the polyolefin composition has decreased to the solidification flow rate, for example, about 190°C, the resin injection inlet 4a and resin outlet 4b of the split mold 1 are opened and closed by the on-off valves VI and V2. Seal.

In this state, the insulator mold 14 is in close contact with the inner wall of the cavity 2 of the split mold 1 because the shrinkage of the polyolefin composition due to cooling regression is compensated by the push.

After that, the heater h is energized to heat the split mold 1, and the induction coil C is wound around the heat-insulating adapter 6.6, and an alternating current is applied to inductively heat the cable conductor 8.8' and insulate it. The temperature of the body mold 14 is set to a predetermined crosslinking temperature, for example, 20
Warm your arms to around 0°C. At this time, the vacuum pump 13 is driven to evacuate the inside of the cable conductor 8.8'.

Insulator mold 14 inside cavity 2 due to humidity
expands in volume, while inside cavity 2 each on-off valve V1~
Since it is sealed by V3, the internal pressure inside the cavity 2 rises, and as a result, the crosslinking of the insulator mold 1/I is performed under pressure.

Further, the water and volatile crosslinking products generated in the crosslinking reaction diffuse through the insulator mold 14, pass through the -C crosslinked semiconductive layer 10, and are sucked and removed from the cable conductor 8.8' side. .

After heating is continued for a predetermined period of time in this manner to sufficiently crosslink the insulator mold 14, cooling is started. At this time, the cooling rate is slow while the temperature is high, and increases when the temperature reaches a low temperature.

Usually, it is appropriate that the cooling rate is slow cooling of about 30° C./hour or less. After cooling to a temperature of about 80° C. at which the insulator mold 14 in the cavity 2 is completely solidified, the split mold 1 is removed and the outer shape is adjusted by finishing processing to complete the insulator connection portion.

8- Note that the outer diameter of the insulator mold 14 becomes smaller than the inner diameter of the cavity 2 of the split mold 1 due to thermal contraction, but the inner diameter of the cavity 2 is set in advance to a diameter that takes into account the thermal contraction of the insulator mold 14 due to cooling. If this is done, an insulator mold with predetermined dimensions can be obtained at room temperature.

[Effects of the Invention] As explained above, according to the method of the present invention, the plastic composition in the mold is crosslinked under pressure without removing the mold, so a cable with good properties and no voids can be produced. Connections can be made efficiently and easily. It also eliminates the need for a pressurized heating furnace used only for crosslinking.

Furthermore, since water and other volatile crosslinking products are removed from the cable conductor side, there is no fear that the crosslinking products will degrade the electrical properties of the insulator.

In addition, in the above embodiment, an example in which the present invention was applied to the formation of a connection part of a cross-linked polyethylene insulated cable was explained, but the present invention should not be limited to such an embodiment. It is similarly applicable to forming connections for other crosslinked rubber/plastic insulated cables, such as n-pyrene insulated cables. In this case, it is desirable that the crosslinkable insulator composition 'C' be of the same quality as the cable insulator.

[Brief explanation of the drawing]

The drawings are longitudinal sectional views for explaining one embodiment of the present invention. １・・・・・・・・・・・・Split mold ２・・・・・・・・・・・・Ki 1? Bitty 3...
・・・・・・Insulator grip part 4a・・・・・・Resin press-fit [] 4b・・・・・・Resin discharge port 6・・・・・・・・・・・・・Heatproof adapter 7.7′・
...Cross-linked polyethylene cable 8.8'...Cable conductor 9...Connection sleeve 10...
......Bridged semiconducting layer 11...
... Sealing part 12 ... Intake pipe 13 ... River ... Vacuum pump 14 ... Town ... Insulator mold agent attorney scholar
Suyama Sa - (1 idiot)

Claims (1)

[Claims] (1) It has a cavity corresponding to the shape of the insulator connection part to be molded. () A split mold with a resin press-fit hole that communicates with this cavity is peeled off in steps to connect the conductor, and then cross-link it on the conductor connection part. The semiconductive layer is fitted onto the outer periphery of the conductor connection portion of the rubber/plastic insulated cable, and the heated and melted crosslinkable rubber/plastic snack composition is filled into the cavity through the resin injection port, and the After cooling the composition filled in the split mold to its assimilation temperature while press-fitting the rubber/plastic composition, the resin injection port is sealed, and then the front distribution mold is heated. Formation of a cable connection part characterized in that the rubber/plastic composition in the cavity is crosslinked and a vacuum is drawn from the cable conductor side to remove volatile crosslinked products by permeating the crosslinked semiconductive layer. Method.