JP2552614Y2 - Fire resistant fiber optic cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application field] The present invention relates to a fire-resistant optical fiber cable used for communication of disaster prevention equipment and the like.

[Related Art] In a communication cable used for disaster prevention equipment such as a building, it is necessary to secure a communication function for a certain period of time in order to allow the disaster prevention equipment to function even during a fire.

According to the standards of the Fire and Disaster Management Agency, fireproof cables used for disaster prevention equipment must pass a fire resistance test in which they are heated according to the heating curve specified in JIS A1304. The heating conditions are a maximum temperature of 840 ° C. and a heating time of 30 minutes.

Conventionally, metal communication lines have often been used as fire-resistant cables. In recent years, however, it has been required to use optical fibers for the purpose of quickly collecting detailed data on disaster situations. In response to such demands, for example, there has been proposed a fire-resistant optical fiber cable using an FRP-coated optical fiber core having an optical fiber surface coated with FRP.

[Problem to be Solved by the Invention] With the structure of the conventional ordinary optical fiber cable, it is not possible to sufficiently suppress the temperature rise in the cable at the time of fire, and the acrylate resin used for plastic coating of the optical fiber or Silicon resin is thermally degraded due to combustion or thermal decomposition, and its strength cannot be secured.If vibration or external force is applied, the wire is easily broken, and the communication function cannot be secured. there were.

Also, even with a fire-resistant optical fiber cable using an FRP-coated optical fiber core wire, the rise in temperature inside the cable cannot be sufficiently suppressed, and the plastic constituting the FRP coating will burn or thermally decompose, causing a similar problem. There was a problem.

An object of the present invention is to provide a fire-resistant optical fiber cable capable of suppressing a temperature rise in a cable for a certain period of time and ensuring a communication function even in a fire.

[Means for Solving the Problems] The configuration of the present invention for achieving the above object will be described. In the present invention, a paper layer is provided around a cable core on which an optical fiber is mounted, and a cable jacket is provided around the outer periphery thereof. In the fire-resistant optical fiber cable provided with, the paper forming the paper layer is a high-density paper having a density of 1.0 g / cm ³ or more, and the cable jacket is at least partially made of flame-retardant plastic. Features.

[Function] It has been known that paper made from pulp has good thermal insulation because of its low thermal conductivity. However, paper conventionally used for communication cables may be made from pulp. Under the above heating conditions, combustion or thermal decomposition occurred in a short time, and the effect as a heat insulating material was not exhibited.

The present inventor has discovered that depending on the material of paper (hereinafter simply referred to as paper) made from pulp, thermal decomposition is small even under the above-mentioned heating conditions, and heat insulation can be maintained. Such a paper material is a high-density paper containing a large amount of cellulose and having a density of 1.0 g / cm ³ or more. This type of high-density paper is commonly called glassine paper and is commercially available.

First, the burning or pyrolysis characteristics of paper can be known by the following simple experiment.

As shown in FIG. 2, paper cut into the size of A4 size is overlapped to a thickness of 2 mm to form a paper layer 1, and the paper layer 1 is blown from below with a burner 2. The temperature of the lower part (the side where the burner 2 is lit) of the layer 1 and the upper part (the side opposite to the heating side of the paper layer 1) are measured with thermocouples 3A and 3B. The present inventors conducted experiments on various paper layers 1A to 1D having different densities shown in Table 1.

The paper layer 1D among the paper layers 1A to 1D is a high-density paper layer having a higher density than the other paper layers 1A to 1C. In the experiment, as shown by the solid line in FIG. 3, the temperature at the upper part of each paper layer 1A to 1D clearly shows a difference in the temperature rising tendency depending on the type of paper layer 1A to 1D.
It was discovered that the higher the density of 1A-1D, the more the rise in temperature was suppressed. Then, density of 0.56 g / cm ³ or less of the paper layer 1A~1
In C, the upper part temperature becomes almost equal to the lower part temperature within about 3 minutes, while the density of the high-density paper layer 1D is 1.07 g / cm ^3.
After about 5 minutes, the temperature at the top became constant, and the state continued for more than 10 minutes. Also, when observing the state of each paper layer 1A to 1D during the experiment, the paper layers 1A to 1C having a density of 0.56 g / cm ³ or less are carbonized as the carbonization progresses from the lower side of the burner 2 where the fire is blown. Was lost by burning, and the thickness of the paper layer was observed to decrease substantially rapidly.
On the other hand, in the high-density paper layer 1D, the rate of carbonization and combustion was extremely slow, and the thickness of the paper layer during the test was substantially the same as before the test. From these experimental results, as the density of the paper is higher, carbonization and combustion are less likely to occur, and the thickness of the paper layer is less reduced. It is presumed that the temperature of the upper part of the paper layer) does not easily rise. Also, the higher the density, the more difficult it is for thermal decomposition to occur because the paper originally contains less oxygen,
It is considered that since the density of the carbide generated by carbonization is high, it is difficult to supply oxygen to the paper inside.

In this experiment, the maximum temperature in the lower part of the paper layer was 600 to 640 ° C., and the characteristic lower temperature pattern is shown by a broken line in FIG.

Therefore, by providing the high-density paper layer 1D on the outer periphery of the cable core on which the optical fiber is mounted, it is possible to configure a heat insulating layer that suppresses a rise in the temperature of the cable core even in a fire.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the fire-resistant optical fiber cable according to the present invention. In this embodiment, the outer diameter is 1.2 mm,
Six optical metal-filled metal tubes 6 each having an optical fiber 5 inserted into a small-diameter metal tube 4 made of a stainless steel tube having an inner diameter of 0.8 mm are twisted around the outer periphery of a tension member 7 made of a galvanized steel wire having a diameter of 1.2 mm. The outer periphery is coated with flame-retardant polyethylene to an outer diameter of 7 mm, and the inner layer of flame-retardant plastic 8
To form a cable core 9. A high-density paper layer 10 having a density of 1.0 g / cm ³ or more was wound around the outer periphery of the cable core 9 to a thickness of 5 mm to form a high-density paper layer 10. The cable core 9 with the high-density paper layer 10 is placed in a steel corrugated pipe 11 having an outer diameter of 25 mm, and the outer periphery of the corrugated pipe 11 is coated with a 1.5 mm thick flame-retardant polyethylene to form an outer layer of a flame-retardant plastic. 12 formed. These corrugated tubes with corrugations
A cable jacket 13 is composed of 11 and the flame-retardant plastic outer layer 12. The flame-retardant polyethylene forming the flame-retardant plastic inner layer 8 is composed of magnesium hydroxide Mg (OH) ₂ of 180.
Part is a flame-retardant polyethylene containing magnesium hydroxide. The flame-retardant polyethylene forming the flame-retardant plastic outer layer 12 is a phosphorus-containing flame-retardant polyethylene. The metal tube 4 has an effect of preventing the optical fiber 5 from directly pressing due to deformation of the cable jacket 13 and other components under high-temperature conditions, and makes it difficult for the optical fiber 5 to break.

Comparative Example 1 In the above cable structure, instead of the high-density paper layer 10,
A low-density paper layer using a paper having a density of 0.56 g / cm ³ was provided. Instead of the flame-retardant plastic inner layer 8, a plastic inner layer using ordinary polyethylene was provided. A thermocouple was inserted into the gap between the corrugated corrugated tube and the low-density paper layer and the metal tube of such a sample of the optical fiber cable having a length of about 1.3 m, and the sample was held horizontally on the pearlite plate. FIG. 4 shows the results of measuring the temperature while heating in a heating furnace according to the heating curve specified in JIS A1304. In Comparative Example 1, the temperature in the metal tube was about 70 minutes in about 15 minutes after the start of heating.
The temperature has risen to 0 ° C, and the temperature at which the plastic coating of the optical fiber is sufficiently degraded by thermal decomposition (about 400 ° C)
Is over.

Example 1 The result of measuring the temperature inside the fire-resistant optical fiber cable shown in FIG. 1 as an example in the same manner as in the comparative example is shown in FIG. It can be seen that in Example 1, the rise in temperature inside the metal tube 4 was extremely suppressed as compared with Comparative Example 1. Among them, the effect of the endothermic reaction of Mg (OH) ₂ contained in the flame-retardant polyethylene forming the flame-retardant plastic inner layer 8 appears at a place where the temperature rise is suppressed at about 400 ° C. The heat insulating effect of the high-density paper layer 10 appears in a temperature range of 400 ° C. or less.

FIG. 5 shows another embodiment of the fire-resistant optical fiber cable according to the present invention. Parts corresponding to those in FIG. 1 are denoted by the same reference numerals. In this embodiment, the outer diameter has four grooves 14 having a width of 0.6 mm and a depth of 0.6 mm.
An optical fiber 5 having a coating diameter of 0.25 mm was dropped into the groove 14 of a metal spacer 15 made of an aluminum alloy of 4 mm to form a cable core 9. A high-density paper layer 10 having a density of 1.07 g / cm ³ was wound around the cable core 9 to a thickness of 4 mm to form a high-density paper layer 10. The outer periphery of the cable core 9 with the high-density paper layer 10 is coated with a flame-retardant polyethylene to an outer diameter of 17 mm to form a flame-retardant plastic inner layer 8.
Was formed. The flame-retardant polyethylene forming the flame-retardant plastic inner layer 8 contains magnesium hydroxide Mg (OH) ₂
It is a flame-retardant polyethylene containing magnesium hydroxide containing 80 parts. This high-density paper layer 10 and the cable core 9 with the flame-retardant plastic inner layer 8 are put into a steel corrugated pipe 11 having an outer diameter of 25 mm, and the outer periphery of the corrugated pipe 11 is coated with a phosphorus-containing polyethylene 1.5 mm in thickness. Thus, a flame-retardant plastic outer layer 12 was formed.

Example 2 A fireproof optical fiber cable having such a structure has a length of 1.3 m.
A thermocouple is inserted between the corrugated corrugated tube 11 and the flame-retardant plastic inner layer 8 in the m-type sample and in the groove 14 of the metal spacer 15, and the sample is held horizontally on a pearlite plate and heated in accordance with JIS A1340. The result of measuring the temperature while heating in the heating furnace according to the curve is shown in FIG. As is apparent from the figure, the temperature inside the groove 14 of the metal spacer 15 is suppressed from rising more than the temperature inside the metal tube 4 of Comparative Example 1.

Other Embodiments Since the heat insulating property of the high-density paper layer 10 is ensured by the thickness of the high-density paper, the structure of the cable core 9 is not limited by this embodiment.

For example, the flame-retardant plastic inner layer 8 is not particularly necessary,
It can be omitted in some cases.

In addition, the use of corrugated corrugated pipe 11 is
Independently from the above, it has a function of suppressing a temperature rise in a different temperature range, and is not particularly necessary, and may be omitted in some cases.

[Effects of the Invention] As described above, the fire-resistant optical fiber cable according to the present invention is provided with a high-density paper layer made of high-density paper having a density of 1.0 g / cm ³ or more as a heat insulating layer. Compared to fiber cables, it is possible to reliably suppress the rise in the temperature inside the cable during a fire for a predetermined time, and to reliably suppress the thermal decomposition of the plastic coating covering the surface of the optical fiber for a predetermined time. The strength can be reliably secured for a predetermined time, and the communication function can be secured for a certain time without disconnection even when vibration or external force is applied. Also,
In the fire-resistant optical fiber cable according to the present invention, at least a part of the cable jacket is made of flame-retardant plastic, so that these effects can be further improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of the fire-resistant optical fiber cable according to the present invention, FIG. 2 is a side view showing a method of testing the heat insulation of a paper layer, FIG. FIG. 5 is a comparison diagram of the internal temperature characteristics of the fire-resistant optical fiber cable according to the present invention and the optical fiber cable of the comparative example. FIG. 5 is a cross-sectional view of another embodiment of the fire-resistant optical fiber cable according to the present invention. 4 ... metal tube, 5 ... optical fiber, 6 ... metal tube containing optical fiber, 7 ... tension member, 8 ... flame-retardant plastic inner layer, 9 ... cable core, 10 ... high-density paper layer,
11 Corrugated tube with corrugation, 12 Flame-retardant plastic outer layer, 13 Cable sheath, 14 Groove, 15 Metal spacer.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Seiji Ikegami 2-5 Kusunokikita-cho, Neyagawa-shi, Osaka Kyowa Electric Wire Co., Ltd. Referee Katsunori Ishii Judge Hidetomo Higashimori Judge Yoshiyuki Kawakami (56) 60-168118 (JP, U)

Claims (1)

(57) [Scope of request for utility model registration] 1. A fire-resistant optical fiber cable in which a paper layer is provided around a cable core on which an optical fiber is mounted and a cable jacket is provided on the outer periphery thereof, wherein the paper forming the paper layer has a density of 1.0 g. A high-density paper of at least / cm ³ , wherein the cable jacket is at least partially made of flame-retardant plastic.