JPS6258088B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a waterproof power cable, and more particularly to a method for manufacturing a power cable that completely prevents moisture from entering from the conductor side and from outside.

Conventionally, in power cables, a method has been used to prevent moisture from entering from the conductor side inside the cable by filling the gaps between the electric conductors with a water run-preventing compound. However, it is a very difficult method to completely fill the spaces between electrical conductors with anti-water running compound, and in order to fill it evenly and evenly, the viscosity of the compound must be low, and in this case, the viscosity of the compound must be low. It is easy to create voids in the cable compound, and the effect of preventing water running is small. Furthermore, if a compound with high viscosity is used, the effect of preventing water running will be increased, but it will be difficult to fill the compound uniformly and evenly. Furthermore, considering the permeation of moisture during long-term use, it can be said that the method of waterproofing power cables by filling them with compound is inferior to the waterproofing method using metal coating. On the other hand, there are methods to prevent water running by coating the cable with metal, such as wrapping or attaching a metal tape vertically, but in this case, it is impossible to completely waterproof the laps of the tape. Ta. Another method is to extrude metal into a pipe shape, but this eliminates the problem of water seepage through the laps of the tape, but since the temperature during extrusion coating is high, plastic is coated as an insulating layer. It was impossible to apply it to cables.

The present invention was created as a result of intensive research to improve the drawbacks of these conventional methods. That is, after a low-temperature melting metal tape is vertically spliced and wrapped over an electrical conductor and/or an insulating layer using a metal tape vertical splicing machine, the metal tape is heated and melted and integrated using an induction heating device. In some cases, a metal water-blocking layer is formed on the conductor and/or the insulating layer to prevent moisture from entering from the conductor side.

As the material of the low-temperature melting metal tape used for the vertical attachment, any metal with a low melting point that allows the insulating layer to withstand induction heating can be used.

For example, if the insulator layer is a heat-sensitive PE coating layer, the coating layer is made of a metal with a melting point of about 330℃ under conditions that do not lead to thermal decomposition (approximately 10 minutes at 370℃ in the absence of oxygen). Easily fusible metals such as lead and lead alloys can be used. Examples of materials other than lead alloys include Wood alloy, Lipowitz alloy, and Rose alloy.

Further, as the low-temperature melting metal tape used in the present invention, for example, a laminate tape made of a combination of a lead tape and an easily fusible metal tape may be used.

Next, aspects of the method of the present invention will be explained in more detail using figures.

Figure 1 is an explanatory cross-sectional view of a waterproof power cable manufactured by the method of the present invention. In the figure, 1 is a conductor, 2 and 2' are a water-shielding layer made of low-temperature melting metal, 3 is a waterproof compound layer, and 4 is an insulator. Layer 5 is a protective sheath layer.

The waterproof and water-shielding layer in a power cable may have one layer or two layers. In the case of one layer of waterproof metal water-shielding layer, the cable conductor 1 supplied from the cable conductor supply device 6 in the layout diagram of the cable manufacturing equipment shown in FIG. 2 is filled with waterproof compound by the waterproof compound extruder 7, and then A low-temperature melting metal tape is vertically applied and wrapped around the outer periphery by a metal tape longitudinal applicator 8, and then an insulating coating is applied by an extruder or tape winder 9. If necessary, the insulating coating is crosslinked in a subsequent heated crosslinking chamber 10. Then, the metal tape is heated by the induction heating device 11 under pressure of nitrogen gas or the like in the pressure chamber 12 to melt and integrate. The purpose of pressurizing with nitrogen gas or the like here is to prevent foaming of the insulator. When crosslinking treatment is not performed, the low-temperature melting metal tape is heated and melted using the induction heating device 11. The cable that has passed through the cooling tank 13 is wound around a winding drum 14 and sheathed on the outer periphery in a separate process.

When two waterproof metal shielding layers are provided, a low-melting metal tape is vertically applied and wrapped again on the cable core after passing through the pressurizing chamber 12 during the above process using the metal tape vertically applying machine 8'. Induction heating device 1
The cable is heated and melted and integrated in step 1', then cooled in a cooling bath 13 and wound onto a take-up drum 14. Furthermore, in this case, induction heating is performed using induction heating device 1.
It is also possible to melt and integrate two layers at the same time using only 1'. In this case, the induction heating device 11 becomes unnecessary. Further, in the present invention, the induction heating device does not need to be installed in a special induction heating chamber, but may be installed in a crosslinking chamber or a cooling chamber. Furthermore, it is not a requirement to fill the conductor with a watertight compound. A protective sheath of plastic or the like is applied to the outer periphery of the cable core thus produced in a separate process to complete a waterproof cable.

In addition, in the present invention, the reason why we have specified the vertical application method as the method of coating the cable core with low-temperature melting metal tape is that low-temperature melting metal tape has poor mechanical properties, especially tensile strength, so general wrap wrapping etc. This is because, if applied, there is a risk that problems such as breakage may occur during winding.

Next, examples of the present invention will be shown.

Example: On the production line shown in Figure 3, the conductor size
Waterproof compound extruder 7 for 150SQ stranded conductor 1
A waterproofing compound is extruded and filled using a metal tape vertical application machine 8, and a lead tape with a thickness of 0.2 m/m is vertically applied and wrapped thereon, and then an uncrosslinked polyethylene composition is extruded on top of this using a metal tape vertical application machine 8. 9 to extrude and coat to a thickness of 4.5 m/m to form an insulating layer, immediately lead it to a heating cross-linking chamber 10 for heat cross-linking, and then lead it to a pressurizing chamber 12 where it is heated at a frequency of 100 KHz. The overlapping portions of the lead tapes were heated and melted into one piece using an induction heating device 11. Subsequently, a metal tape with a thickness of 0.2m/m is applied onto this cable using a vertical spreading machine 8'.
After wrapping the lead tape vertically, the overlapping parts of the lead tape are heated by an induction heating device 11' with a frequency of 100 KHz to melt and integrate them, and then placed in a cooling tank 13'.
After cooling inside, it was wound up once, and a polyethylene sheath layer was formed in a separate process on the thus produced cable core.

Comparative Example A product was manufactured in the same manner as in the example without induction heating of the vertically attached lead tapes 2, 2'.

A waterproof test was conducted on each of the 10 m long cables manufactured in the above Examples and Comparative Examples.

The test method is 10 from the conductor side and the outside of the cable.
Kg/cm ² of pressurized water was injected. As a result, in the cable of the example, no water leakage phenomenon was observed from the cable terminal part, but in the cable of the comparative example, water leaked from the cable terminal part 10 minutes after the test.

As explained above, in the case of providing two waterproof layers, the method for manufacturing a waterproof cable according to the present invention involves impregnating and coating a conductor with a waterproof compound, and then heating the conductor with an induction heating device at this point to cover it by longitudinally splicing it. After melting and integrating the metal tape, the insulating layer is again covered with a low-temperature melting metal tape, which is again heated using an induction heating device to melt and integrate the metal tape. Since the outer layer is coated with a sheath, it is possible to obtain the same complete waterproofing effect as when waterproofing is achieved by applying a metal sheath over a conventional insulating layer. It is possible to obtain a cable with the highest waterproofness that can be manufactured using current equipment, without causing uneven filling or voids, and without water infiltration from the laps unlike when wrapping metal tape with metal coating. becomes. Further, even if a method of providing a metal sheath for waterproofing is developed to technically overcome the effects of high temperatures on the insulating coating layer, which is a problem when forming a metal sheath, the cable produced by the manufacturing method of the present invention will not be waterproofed by the metal sheath. The cable itself can be manufactured lighter and at lower cost, and the manufacturing method of the present invention has many advantages in terms of waterproofness, form, and economy, and its practical value is extremely great. be.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a waterproof cable having two waterproof layers made by melting and integrating lead tape according to the manufacturing method of the present invention, Fig. 2 is a production line layout diagram in the case of only one waterproof layer using the manufacturing method, and Fig. 3 2 is a production line layout diagram in the same case where two waterproof layers are provided. 1... Electric conductor, 2, 2'... Low melting metal tape layer, 3... Waterproof compound layer, 4... Insulating coating layer, 5... Sheath layer, 6... Supply drum, 7... Waterproof compound. Extruder, 8,8'...
...Metal tape longitudinal addition machine, 9...Uncrosslinked plastic compound extruder, 10...Heating crosslinking chamber, 1
1, 11'... Induction heating device, 12... Pressurizing zone, 13, 13'... Cooling tank.

Claims (1)

[Claims] 1. In manufacturing a waterproof power cable having a water-blocking layer on a conductor and/or an insulating layer, a low-temperature melting layer is provided on the conductor and/or an insulating layer formed on the conductor. After vertically splicing and winding a metal tape, it is heated with an induction heating device to melt and integrate the overlapping parts of the metal tape to form a water-shielding layer made of a low-temperature melting metal on the conductor and/or insulator layer. A method for manufacturing a waterproof power cable, characterized by providing a waterproof power cable. 2. The method for manufacturing a waterproof power cable according to claim 1, characterized in that a lead tape is used as the low-temperature melting metal tape. 3. The method for manufacturing a waterproof power cable according to claim 1, characterized in that an easily fusible metal tape is used as the low-temperature melting metal tape. 4. The method for manufacturing a waterproof power cable according to claim 3, characterized in that a lead alloy tape is used as the easily fusible metal tape.