JPS6319042B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a jewelry-filled cable with a warning wire, and more particularly to a jewelry-filled cable with a tape-shaped warning wire.

Cables, especially communication cables, have voids in their cable sheaths, so when water enters the sheath, the water moves through the voids within the cable, expanding the flooded area and increasing the failure rate. Therefore, this void is filled with a waterproofing mixture, such as a mixture of petroleum-based jewelry and low molecular weight polyolefin.
It is commonly called a jelly-filled cable. Jewelry-filled cables have the voids inside the cable filled with jewelry and are intended to be maintenance-free, so if any damage occurs to the cable sheath, the damage will not be discovered until it develops into a communication failure. The structure is such that it cannot be done. However, in actual use, insulation failure may occur due to damage to the cable sheath or failure of the connection. Therefore, there is a need for a system for early detection of such failures, but to date no such system has been developed for Gielly-filled cables.

By the way, in non-Jiely filled cables, so-called air core cables, there are problems such as the above-mentioned problems.
In particular, warning wires are placed inside cables for early detection of flooding problems. In the early versions, two alarm wires were placed near opposite edges of the cable, and insulation between the two alarm wires, that is, a decrease in resistance, was detected. However, this structure had drawbacks, such as water intrusion being detected only after a considerable drop in insulation.To solve these problems, an alarm wire consisting of multiple conductor strips lined up on plastic tape was proposed. (Tokuko Akira)
36-13380). Furthermore, an alarm wire has been proposed in which each conductor is provided on both sides of the plastic tape, and a hole is provided that penetrates all the layers (Utility Model Publication No. 46-34029).

However, these systems were developed to detect water intrusion in air core cables, and when applied to cables filled with jelly, the degree of water intrusion is significantly lower than in air core cables due to the presence of jelly. In addition, it is often difficult to detect water intrusion in cables filled with jelly, where even if water floods in one place, the possibility of water running to other parts is very small.

As a result of intensive research into a water intrusion detection system for cables filled with cables, the present inventors discovered that water intrusion into the cable sheath can be effectively detected by arranging a tape-shaped warning wire inside cables filled with cables. The present invention has now been completed.

That is, the gist of the present invention is to provide a jewelry-filled cable comprising a tape-shaped alarm wire having two conductive metal strips arranged in parallel between a cable sheath and a cable core. The present invention relates to a cable filled with jelly, which is characterized by having a hygroscopically swellable polymer layer disposed so as to bridge between two conductive metal strips.

The present invention is applicable to communication and power cables, as long as the cable core is filled with jewelry.
Furthermore, it is also applied to optical fiber cables,
The following explanation will mainly be made regarding communication cables.

Tape-shaped alarm wires generally have at least two conductive metal strips laminated in parallel on a base tape. Examples of the base tape include polyester and polyolefin (eg, polyethylene).

Conductive metal strips include aluminum, copper,
Foil or ultrafine wire made of a highly conductive metal such as silver is used, but metal foil, especially aluminum foil, is preferred because it allows the tape-shaped alarm wire to be made thinner and have a larger cross-sectional area.

The spacing between the metal conductors is preferably 30 mm or less. If the interval is too wide, there is a risk that an abnormality may not be detected before a communication failure occurs.

A tape-shaped alarm wire made of a base tape and a metal conductor may not exhibit a sufficient detection function depending on the arrangement of the alarm wire, as will be described later. Therefore, a hygroscopic swellable polymer layer is provided to at least bridge the conductive metals, thereby retaining the water in a specific narrow area and lowering the insulation resistance of that area.

The moisture-swellable polymer layer may be provided between the base tape and the metal layer instead of being provided on the metal layer.

The hygroscopic swellable polymer used in the present invention refers to a polymer that has the property of swelling and retaining water by absorbing moisture or water. Examples of such polymers include starch or cellulose derivatives (for example, starch-sodium acrylate, Known materials such as starch-acrylonitrile, carboxymethylcellulose sodium or calcium salt), acrylic acid polymers (for example, sodium polyacrylate, polyvinyl alcohol-sodium acrylate, polyacrylamide-sodium acrylate), polyvinyl alcohol, etc. can be used.

The moisture-swellable polymer layer is formed by adding a moisture-swelling polymer to a base film (e.g., polyethylene terephthalate, polybutylene terephthalate, polypropylene, polyethylene, polyvinyl chloride, cellulose paper, cloth of natural or synthetic fibers, etc.).
Formed by bonding as a woven or non-woven fabric. Adhesion is adhesive (for example, acrylic adhesive, etc.)
This is done using a hot melt adhesive (for example, ionomer resin, thermoplastic polyester, etc.) or a thermosetting adhesive (for example, urethane adhesive, epoxy adhesive, acrylic adhesive, etc.).

If the moisture-swellable polymer is a powder, it may be kneaded with a binder (eg, natural rubber) and applied onto the base film.

The tape-shaped warning wire can be provided at any position between the cable sheath and the cable core. However, for early detection of water intrusion, a metal tape or a metal laminate tape is provided between the cable core and the sheath, especially in the case of a longitudinally-aligned cable, between the core and the longitudinally-aligned tape. In the case of a cable in which a metal tape or metal laminate tape is run lengthwise, there is a high possibility that water will infiltrate from the overlapped part of the tape, so it is preferable to run the tape-shaped warning wire vertically in parallel under the overlapped part.

If the tape-shaped alarm wire is laid vertically parallel to the longitudinal axis of the cable as described above, or if it is wound spirally at equal pitches, the location of the fault can be found accurately if the gaps between the conductors are kept constant. can do. As methods for this purpose, methods such as the high voltage Murray method (marlay) and the pulse echo method are known.

According to the present invention, it is possible to detect the occurrence of water intrusion in a cable filled with jewelry, which is originally sufficiently prevented from entering and penetrating water, before it is slight. Also,
If jewelry is filled between the metal conductors of a tape-shaped alarm wire, the conductivity between the conductors will deteriorate, but since a tape-shaped alarm wire with a hygroscopic swelling polymer layer is used,
Since the conductors are not filled with jewelry, conductivity is improved, and the polymer absorbs moisture and swells.
Because it retains water, it prevents water running and enables early detection of water intrusion, making it highly desirable for cable maintenance.

Next, the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 shows a jewelry-filled communication cable 1 containing a tape-shaped warning wire according to the present invention.

The cable 1 has the required number of conductor units,
A core 2 filled with jewelry, a rough wrap 3 of polyethylene tape gap-wound around the core 2, a presser wrap 4 longitudinally stretched around the rough wrap 3, a rough wrap 5 of nylon thread around it, a rough wrap 5 It consists of an aluminum laminate tape 6 stretched longitudinally around the periphery, and a sheath 7. The surface of the rough roll 5 is coated with a jelly compound (not shown).

The tape-shaped alarm wire 8 is provided directly below the overlapping portion 9 of the aluminum laminate tape 6. Immediately below this overlapping part, the tape 6 is insufficiently fused and water runs most easily, so it is most effective to provide a warning line here.

In addition, at least one other tape-shaped warning wire may be provided between the coarse winding 5 and the tape 6 other than directly below the overlapped portion, preferably on the opposite side of the overlapped portion.

The tape-shaped warning wire can not only be provided parallel to the longitudinal direction, but also be spirally wound around the coarse winding 5.

2 and 3 show cross-sections of other jelly-filled cables.

The cable 21 in FIG. 2 has a core 22, around which an aluminum tape 23 and an iron tape 24 are vertically laid, and a sheath 25 covering the outside thereof.

The tape-shaped alarm wires 26, 26' are connected to each tape 23.
and 24 are provided directly below the overlapping portions 27 and 28, respectively. In this case, alarm wire 2
Only one of 6 and 26' may be provided.

The cable 31 in FIG. 3 has a structure in which a core 32 is covered with a sheath 33.

The tape-shaped warning wire 34 has a core 32 and a sheath 33.
It is placed vertically between the Further, the alarm wire 34 may be spirally wound around the core instead of being laid vertically.

4-6 are cross-sectional views of various tape-shaped warning wires.

Mylar, which is preferably used for the base tape, is
It has the disadvantage that water easily runs on its surface. Therefore, in order to prevent water running and to be able to detect even a small amount of water intrusion, the alarm wire can be provided with a hygroscopic swellable polymer layer.

In the embodiment of FIG. 6, the hygroscopic swellable polymer layer 13
is laminated on the aluminum foil 11.

Further, in the embodiment shown in FIG. 7, a polymer layer 13 is interposed between the base tape 10 and the aluminum foil 11.

The embodiment of FIG. 8 is a powdery hygroscopic swelling polymer 1
4 is attached to the entire length of the warning wire.

It goes without saying that in the present invention, a round conductor can be used instead of aluminum foil.

Next, examples will be shown to further explain the present invention.

Example 1 A 6.5φ hole was formed from the opposite side of the alarm wire installation point through the polyethylene sheath, through the aluminum laminate tape, and then through the longitudinal presser wrapping tape in the alarm wire-filled cable with the same structure as shown in Figure 1. did. A 1m high water column was placed in the hole.

When I measured the resistance before and after filling with water using a super megohmmeter, it was 2.8×10 ¹⁰ Ω before filling with water, and 10 ⁵ after filling with water.
It was below Ω.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an example of a cable filled with warning wire according to the present invention, and FIGS. 2 and 3 are
4 to 6 are cross-sectional views of other examples of the alarm wire-containing jewelry-filled cable of the present invention, and FIGS. 4 to 6 are cross-sectional views of various tape-shaped alarm wires. DESCRIPTION OF SYMBOLS 1... Jewelry filled cable, 2... Core, 3... Roughly wound, 4... Presser wound, 5... Roughly wound, 6... Aluminum laminate tape, 7... Sheath, 8... Tape-shaped warning wire, 9... Overlapping part, 10... Base tape, 11,
11'... Aluminum foil, 13... Hygroscopic swelling polymer layer, 21... Cable, 22... Core, 23... Aluminum tape, 24... Iron tape, 25... Sheath, 26, 26'... Tape-shaped alarm wire, 27, 2
8... Overlapping part, 31... Cable, 32... Core,
33...Sheath.

Claims (1)

[Scope of Claims] 1. A jewelry-filled cable comprising a tape-shaped alarm wire with two conductive metal strips arranged in parallel between a cable sheath and a cable core, wherein the tape-shaped alarm wire is A jewelry-filled cable characterized by having a hygroscopically swellable polymer layer arranged so as to bridge between two conductive metal strips. 2. The jewelry-filled cable has a metal tape or metal laminate tape that is laid lengthwise on the cable core and overlapped at the end, and the tape-shaped warning wire is placed under the overlapped part of the metal tape or metal laminate. The jelly-filled cable according to claim 1, which is laid vertically. 3. The jewelry-filled cable according to claim 1, wherein the tape-shaped warning wire is spirally wound around the cable core at equal pitches. 4. Claims 1 to 3 in which the tape-shaped warning wire comprises a hygroscopic swellable polymer layer laminated to bridge two conductive metal strips laminated in parallel on a base tape. Jewelry-filled cable according to any of paragraphs. 5. Claims 1 to 3 in which the tape-shaped alarm wire comprises a base tape, a hygroscopic swelling polymer layer laminated on the base tape, and two conductive metal strips laminated in parallel on the polymer layer. Jewelry-filled cable according to any of paragraphs. 6. A jewelery-filled cable according to any one of claims 1 to 5, wherein the moisture-swellable polymer layer comprises a moisture-swellable polymer layered on a base material.