JPS6334171Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a protective cover for an overhead communication cable suspended from a messenger wire.

In order to protect overhead communication cables from damage caused by fire, proposals have been made to protect the cables with a cylindrical body made of flame-retardant FRP.
Communication cables are usually suspended with hangers over short spans of about 10 cm, so from the perspective of simplifying the protection work, a protective cover with an inner diameter that envelops the communication cable together with the messenger wire is recommended. It is used. In the state in which the cover is applied, the interior of the cover includes a relatively large space.

By the way, in the event of a fire, if the protective cover is exposed to fire for a long time, for example, even if the protective cover maintains its initial shape, the temperature of the air inside the cover will rise due to the heat passing through the cover. For this reason, even if the cover is cooled from the outside during fire extinguishing operations, the inside of the cover is unlikely to be cooled unexpectedly, and the high temperature inside the cover may deform the low-melting-point insulation layer of the communication cable, such as polyethylene. There is a problem that the insulation properties of

Focusing on the fact that the above-mentioned increase in air temperature inside the cover is due to the poor insulation properties of conventional covers, the present invention provides a heat insulating layer made of heat-resistant material inside the cover, thereby preventing fires. At the same time, the temperature rise of the gas phase inside the cover should be kept small.

Hereinafter, the present invention will be explained in detail with reference to the drawings. The attached figure is a sectional view of an embodiment of the present invention, and 1 is a half-shaped protective cover, which has an outer layer 12 made of a flame-retardant or fire-resistant material and a heat insulating layer 13 provided inside the outer layer 12. Consisting of The upper and lower halves of the cover 1 are joined together by bolts and nuts 2. 3 and 4 are a communication cable and messenger wire, respectively, and 5 is a hanger.

The outer layer 12 may be made of conventionally known materials such as glass, phenolic resin, asbestos, short lengths of heat-resistant fibers such as carbon, woven fabric, non-woven fabric, etc., and reinforced with organic or inorganic flame retardants. Examples include epoxies, unsaturated polyesters, and furan-based thermosetting resins. The appropriate thickness of the outer layer 12 is about 1 to 4 mm. The constituent material of the heat insulating layer 13 is an organic polymer having a melting point or softening point of at least 150°C, for example,
Poly-4-methylpentene-1, polyamide, polyimide, fluororesin, polyester fiber mat foam, polyurethane, silicone rubber, crosslinked rubber foam such as chloroprene, glass wool, rock wool, ceramic wool, asbestos wool, foam glass, foam concrete,
Examples include inorganic materials such as asbestos foam. The appropriate thickness of the heat insulating layer 13 is about 2 to 40 mm.

The remarkable effects of the present invention can be understood, for example, by the following experimental examples.

A 0.85mm rubber sheet is placed on top of a core of 200 prime pairs (outside diameter 32mm) made of a 0.3mm thick polyethylene foamed copper conductor with an outside diameter of 0.65mm.
A communication cable with a 2.2 mm LAP sheath was covered with a 3 mm thick glass fiber-reinforced flame-retardant unsaturated polyester cover, including the messenger wire, as shown in Figure 1. There is a gap of approximately 25 mm between the bottom inner wall of the cover and the bottom of the communication cable,
There was a gap of about 20 mm between the inner wall on the cover side and the cable (this experimental example is used as a comparative example). Instead of the cover used in the above comparative example, a cover was used in which a 15 mm thick layer of silicone rubber foam (manufactured by Toray Silicon Co., Ltd., SE190-RTV Home; foaming ratio of about 3 times was used) was applied to the entire inner wall of the cover. Except for this, an experimental product (this experimental example will be referred to as an example) was prepared under the same conditions as the above comparative example.

When the comparative example and the example were heated along the JISA1301 outdoor class 2 heating curve, the temperature of the air inside the cover at 5 minutes, 10 minutes, 20 minutes, and 30 minutes after the start of heating was the same as that of the comparative example. If, respectively
The temperatures were 350℃, 480℃, 400℃, and 360℃. On the other hand, in the case of the example, 120℃, 140℃,
The temperature was 120℃ and 110℃. When the cable was disassembled after the heating experiment, in the case of the comparative example, the foamed polyethylene insulation layer was thermally deformed and insulation failure occurred, but in the case of the example, no deformation of the insulation layer was observed at all. .

[Brief explanation of the drawing]

The accompanying drawings show cross-sectional views of embodiments of the present invention, in which 1 is the protective cover of the present invention, 12 is its outer layer, and 13 is a heat insulating layer.

Claims (1)

[Scope of utility model registration request] Suspended from a messenger wire characterized by having a heat insulating layer made of an organic polymer or inorganic material having a melting point or softening point of at least 150°C or more on the inside of an outer layer made of a flame-retardant or fire-resistant material. Protective cover for overhead communication cables.