JPH0439192B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a reinforcing insulator at a cable joint used for connecting rubber-plastic insulated cables.

Traditionally, for example, to form a reinforcing insulator when connecting plastic insulated cables, a synthetic resin molding extruder is used to inject the reinforcing insulator into a mold placed around the cables to be connected. Usually, it is solidified. However, it must be noted here that a crosslinking agent is mixed into the reinforcing insulator and crosslinking is performed by heating, but at that time, crosslinking may occur within the extruder.
Alternatively, since bridging takes place within the piping, cleaning after use is extremely troublesome, and in some cases, expansion of the reinforcing insulator during bridging may destroy these devices.

The purpose of the present invention is to solve the above-mentioned problems, and to facilitate cleaning of the pipeline by providing a three-way switching valve in the pipeline to switch between a reinforcing insulator containing a crosslinking agent and a resin without a crosslinking agent. The purpose of this invention is to provide a method for forming reinforcing insulators at cable joints that do not adversely affect equipment. a first step of filling the insulating reinforcing material containing a cross-linking agent into the injection pipe, and discharging the resin without the cross-linking agent in the injection pipe from the open end via a three-way switching valve; a second step of extruding, then switching the three-way switching valve to inject the insulation reinforcement into the mold, and switching the three-way switching valve again to push the resin that does not contain a crosslinking agent into the injection pipe. a third step of discharging the insulating reinforcement in the injection conduit from the open end, and a fourth step of heating the mold to bridge the insulating reinforcement in the mold. It is characterized by

The present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a schematic diagram of an apparatus for applying the method according to the present invention, in which 1a and 1b are, for example, cross-linked polyethylene insulated power cables to be connected, and the conductors 2a and 2b are connected by a sleeve 3. has been done. Further, insulators 5a and 5b are provided around the cable conductors 2a and 2b via an internal semiconducting layer.
is formed in the shape of a pencil sharpener, and after covering the upper layer of the sleeve 3 with a semiconducting layer 4, a reinforcing insulator is formed around it. A mold 6 is provided at this connection portion, and the molten reinforcing insulator is injected into the mold 6 from an extruder 7 via an injection conduit 8. Further, a three-way switching valve 9 is provided in the vicinity of the mold 6 of the injection pipe line 8, so that the end of the injection pipe line 8 from the extruder 7 can be selectively branched into the mold 6 and the open end 10. It's becoming like that. Furthermore, a heater 11 is arranged around the mold 6, and a pressure gauge 12 is provided to measure the pressure of the insulation reinforcement inside the mold 6 during crosslinking. As the extruder 7, a small portable rubber/plastic extruder with a portable trolley type is used, which is advantageous for on-site work where cables are connected in tunnels, manholes, etc.

In addition, in FIG. 2, first, second, and third molds 6a, 6b, and 6c are provided for each part of the three-phase power cable where each phase line is to be connected, and one extruder 7 , second and third injection pipes 8a, 8b, 8c
Then, the insulation reinforcement can be injected into each of the molds 6a, 6b, and 6c. here,
Injection pipe 8a near each mold 6a, 6b, 6c,
First, second, and third three-way switching valves 9a, 9b, and 9c are respectively disposed in 8b and 8c, and the molds 6a, 6b, and 6c are connected to the first, second, and third open ends. 10a, 10b, and 10c can be selectively switched. Furthermore, there is also a switching section from the extruder 7 to each injection pipe 8a, 8b, 8c.
Three-way switching valves 13a and 13b for branching are provided.

There are different types of three-way switching valves 9, 13, such as those shown in FIG. By rotating the opening, the two entrances and exits are selectively communicated with each other.

First, when injecting the reinforcing insulator into the first mold 6, the branching switching valve 13a is switched to the first injection pipe 8a side, as shown in FIG. 9a is switched to the first open end 10a side, and here, a synthetic resin R made of, for example, a colorless polyethylene resin compound that does not contain a crosslinking agent is extruded from the extruder 7 to clean the inside of the first pipe line 8a.

Next, as shown in FIG. 4b, the first three-way switching valve 9a is switched to the mold 6 side, and a supplementary insulator P made of, for example, polyethylene resin mixed with a crosslinking agent is inserted into the mold.
Inject into the mold 6 at a filling pressure of about 15 kg/cm ² .
Here, when extruding the reinforcing insulator P from the extruder 7, the first three-way switching valve 9a is closed at the open end 10 for a while.
It is preferable to switch to the a side after confirming that the reinforcing insulator P has reached the three-way switching valve 9a. Note that the reinforcing insulator P containing a crosslinking agent has a pale yellow color, whereas the resin R that does not contain a crosslinking agent is colorless and transparent, so that it can be easily distinguished.

Then, after checking that the reinforcing insulator P has been filled into the mold 6a using the pressure gauge 12 or the like, the three-way switching valve 9a is again turned to the open end 10a as shown in FIG. 4c.
Switch to the side and transfer resin R without crosslinking agent to extruder 7.
to clean the inside of the first injection pipe 8a. Thereafter, the mold 6a is heated by the heater 11 to heat the reinforcing insulator P therein to a crosslinking temperature, thereby crosslinking the reinforcing insulator P.

Next, when injecting the reinforcing insulator P into the second mold 6b, as shown in FIG.
a to the second pipe line 8b side, and the second switching valve 9
b is switched to the second open end 10b side, and then the resin R containing no crosslinking agent is extruded from the extruder 7 to clean the inside of the second conduit 8b. Next, as shown in FIG. 5b, the second switching valve 9b is switched to the second mold 6b side, and the reinforcing insulator P containing the crosslinking agent is transferred to the mold 6b.
Inject into. Then, as shown in FIG. 5c, the second three-way switching valve 9b is switched to the open end 10b side again, and the resin R containing no crosslinking agent is extruded from the extruder 7 to clean the inside of the second pipe line 8b. Then, the reinforcing insulator P in the mold 6b is crosslinked.

Further, in order to inject the reinforcing insulator P into the third mold 6c, the switching valve 13b is switched to the third injection pipe 8c side, the third switching valve 9c is switched to the open end 10c side, and the switching valve 13b is switched to the open end 10c side. As shown in Figure 6a, the resin R containing no crosslinking agent is extruded from the third pipe line 8c to the open end 10c to clean the pipe line 8c, and then the third switching valve 9c is
by operating the first and first molds 6a, 6 mentioned above.
Perform the same operation as in case b to open the third conduit 8c.
The inside of the third mold 6c is cleaned and the inside of the third mold 6c is crosslinked.

Even after the work is completed, the switching valves 9, 1
3. The injection pipe 8 is made of synthetic resin R that does not contain a crosslinking agent.
will remain, but since this resin R will not crosslink or gel even if it is heated as it is, it can be extruded during the first cleaning during the next connection operation.

In the embodiment, a plastic insulated cable has been described, but even in the case of a rubber insulated cable, the present device can be used in the same way as long as the insulation reinforcement is made of a rubber material containing a crosslinking agent.

As explained above, in the method for forming a reinforcing insulator for a cable connection part according to the present invention, a resin containing no crosslinking agent is injected into the mold before and after injecting a reinforcing insulator containing a crosslinking agent into a mold using a three-way switching valve. Since cleaning is performed through the injection pipe, there is no need for the reinforcing insulator containing the crosslinking agent to remain in the extruder or the injection pipe, and there is no need for any negative effects on the equipment, and there is no need for special cleaning by hand or the like after use.

[Brief explanation of drawings]

The drawings show an embodiment of the method for forming a reinforcing insulator at a cable connection part according to the present invention, and FIG. 1 is a schematic diagram thereof, and FIG. 2 shows an example of forming a reinforcing insulator at a connection part of a three-phase power cable. An explanatory diagram, FIG. 3 is a configuration diagram of a three-way switching valve, and FIGS. 4, 5, and 6 are explanatory diagrams, respectively. 1a and 1b are cables, 2a and 2b are conductors, 4a and 4b are insulators, 6 is a mold, 7 is an extruder, 8 is an injection pipe, 9 and 13 are three-way switching valves, P is a reinforcing insulator, R is a synthetic resin containing no crosslinking agent.

Claims (1)

[Claims] 1. A first step of filling an injection pipe of a mold used for connecting a rubber/plastic insulated cable with a resin that does not contain a crosslinking agent, and injecting an insulation reinforcing material containing a crosslinking agent into the injection pipe and performing the injection. a second step of extruding the resin not containing the crosslinking agent in the conduit from the open end via a three-way switching valve, and then switching the three-way switching valve to inject the insulation reinforcement into the mold; a third step of switching the three-way switching valve again to push resin that does not contain a crosslinking agent into the injection pipe and discharging the insulation reinforcement in the injection pipe from the open end; and heating the mold. A method for forming a reinforcing insulator for a cable connection portion, comprising a fourth step of bridging the insulating reinforcing member in the mold.