JPH0219996A - Optical cable type heat sensor - Google Patents

Abstract

PURPOSE:To identify a heat detected place with a simple arrangement by using the local microbending loss of a covered optical fiber caused by the contraction of a press-winding tape composed of a thermo-contracting material. CONSTITUTION:Covered optical fibers 12 are twisted together around a center tensile strength wire 11 having protrusions 11a on its surface, a press-winding tape 13 composed of the thermo-contracting material is wound on the fibers 12, and a metallic conduit 14 having high heat conductivity is applied as a housing. Consequently, when the ambient temperature becomes high, and heat is transmitted to the press-winding tape 13, the press-winding tape 13 contracts in its longitudinal direction, the covered optical fibers 12 are pressed against the protrusions and meander, and optical transmission loss by microbending increases. Thus, time of day and the place where the ambient temperature rises can be accurately detected by continuously monitoring the longitudinal directional optical transmission loss distribution of the covered optical fibers 12 by a back scattering light measuring instrument.

Description

[Detailed Description of the Invention] <Industrial Application Minute Hand> The present invention is applicable to fire detectors for lim materials, temperature sensors for storage containers of highly twisted substances such as gas tanks, and detection of oil leaks from pipelines for transporting heated oil. This invention relates to an optical cable type thermal sensor that can be used as a sensor, etc.

<Prior art> Fire detectors conventionally used for buildings, etc. include, for example, [Machine Research Vol. 38 No. 1 (19
86) There is a constant temperature spot type thermal sensor shown in P234J.

The principle of this constant temperature spot type thermal sensor is shown in FIG.

As shown in the figure, this thermal sensor utilizes a bimetal 1 made by gluing together two metal plates having different coefficients of expansion, such as brass and invar. That is, the sensor body 2 is provided with a contact point a at one end of the bimetal 1, as well as a contact point that is separated from the contact point a in normal conditions. Then, the contact point a and the contact point of the curved bimetal 1 come into contact, and the fire lamp 4 lights up and the alarm bell 5 sounds. In addition, in the figure, 6 indicates a battery.

<Problems to be Solved by the Invention> However, as described above, in the constant temperature spot type thermal sensor, when the temperature reaches a high temperature due to a fire, for example, when the contact point a and the contact point A come into contact, the fire lamp 4 And the alarm Pell 5 is energized, so the contact a.

There is a problem in that a spark must always occur the moment b come into contact with each other. For this reason, the use of this type of thermal sensor is limited to fire alarms in private houses and offices, and cannot be used as a temperature sensor for highly twisted material storage containers such as gas tanks.

In addition, this type of thermal sensor transmits information by turning on and off electric current, so for example, when using a system to identify the location of a fire, wiring such as one copper cable is required for one sensor. There is also the issue of becoming. Example or
When implementing a fire detection system to identify the location of a fire in a skyscraper that requires hundreds of thermal sensors,
Hundreds of copper cables and other wiring are required, resulting in an extremely large economic burden.

In view of these circumstances, it is an object of the present invention to provide an optical cable type thermal sensor that can be used as a temperature sensor for storage containers for highly twisted substances, and can also identify the detection location with simple installation. shall be.

Means for Solving the Problems> An optical cable type thermal sensor according to the present invention that achieves the above-mentioned object has a central tensile strength line having protrusions forming unevenness in the longitudinal direction on the surface, and a wire twisted around the central tensile strength line. The present invention is characterized in that it has an optical unit comprising a coated optical fiber to be combined with the coated optical fiber, and a press-wrap tape made of a heat-shrinkable material and press-wound on the coated optical fiber.

Function> When the temperature around the optical cable type thermal sensor configured as described above becomes high and heat is transmitted to the presser tape that forms the optical unit, the presser tape contracts in the length direction and the optical unit is closed. Strong radial tightening provides force. At this time, the coated optical fiber sandwiched between the holding tape and the central tensile strength wire is pressed against the protrusion on the surface of the central tensile strength wire and twists, increasing optical transmission loss due to microbending. Therefore, by continuously monitoring the optical transmission loss distribution in the length direction of the coated optical fiber using a backscattered light measuring device, it is possible to accurately detect the time and place at which the temperature around the optical cable type thermal sensor increases. Be able to do that.

Practical example Hereinafter, the present invention will be explained based on examples.

As shown in FIG. 1, the optical cable type thermal sensor 10 of the present embodiment has eight coated optical fibers 12 twisted around a central tensile strength line 11, and a pressure-wrapping tape 13 made of a heat-shrinkable material placed on top of the eight coated optical fibers 12. A highly thermally conductive metal 11 is used as an outer covering for the optical unit formed by winding the . ! ''14.Moreover, in detail, the center tensile strength cotton 11 has a diameter of 0.
A steel wire with a diameter of 3 mm is coated with polyethylene to have an outer diameter of 0.4 mm, and the height is 0.1 m.
The coated optical fiber 12 has a core diameter of 50 μm, a cladding diameter of 125 μm, and a relative refractive index difference of 1.0.
% ordinary multi-mode optical fiber coated with ultraviolet curing urethane acrylate resin to have an outer diameter of 250 μm, and the pressure winding tape 13 has a thickness of 0.2 m.
It is a heat shrinkable tape with a width of 15 mm, a heat shrinkage start temperature of 70°C, a heat shrinkage end temperature of 90°C, and a maximum shrinkage rate of 40%. As the metal tube 14, a stainless steel tube with a thickness of 0.1++w* was used, and the outer diameter was 1.6 .phi. Note that the single length of the optical cable type thermal sensor 10 of this example was 1 km+m.

The following experiment was conducted using the optical cable type thermal sensor 10 of this example.

First, as shown in FIG. 3, an optical cable type thermal sensor 10
One coated optical fiber 12 is taken out from one end of the coated optical fiber 12 and connected to a backscattered light measuring device 15 with a wavelength of 1.3 μm, and the total length of the coated optical fiber 12 in the optical cable type thermal sensor 10 is We measured the optical transmission loss distribution over The measurement results at this time are shown in FIG. 3 (al).

Next, the central part of the optical cable type thermal sensor 10, that is, a point 500 m from both ends, was immersed in boiling water at 100°C, and after 1 minute, the backscattered light of the coated optical fiber 12 was measured again. The results are shown in Figure 3 (bl).

From FIG. 3(a) and (bl), optical cable type thermal sensor 10
One minute after the central part of the specimen was immersed in a 100° C. vortex, an increase in optical transmission loss of approximately 0.9 dB occurred at that point, proving its effectiveness as a thermal sensor.

In addition, in the above embodiment, the protrusion formed on the surface of the central tensile force line was formed into a hemispherical shape, but it is not limited to this.
In short, it is sufficient to form irregularities in the longitudinal direction on the surface of the central tensile strength line using the pressure-wrapping tape so that micro-bending is likely to occur in the optical fiber when the coated optical fiber is pressed. For example, it may be a protrusion formed in a spiral shape.

In addition, in the above embodiment, one optical unit is covered with an outer cover to form a light-pull shape, but the present invention is not limited to this, and multiple units may be formed into a cable-like structure, or they may be loosely stored in a metal tube or the like. It may be something like this.

<Effects of the Invention> As explained above, the optical cable type thermal sensor of the present invention utilizes the local microbending loss of the coated optical fiber caused by the contraction of the pressure-wrapping tape made of a heat-shrinkable material. Since the location of optical transmission loss can be identified using scattered light, it can be applied, for example, to fire alarm systems in skyscrapers, which conventionally required hundreds of thermal sensors and hundreds of copper cables. In this case, - Optical cable type thermal sensors of appropriate length are continuously installed inside the building.
! Since only a few steps are required, the system construction cost can be significantly reduced.

Also, like a traditional thermal sensor, the contacts are turned on.

Since there is no need to worry about sparks caused by turning off, it can be used to detect oil leaks from temperature sensors in storage containers for highly twisted materials such as gas tanks, or oil transport pipelines that transport oil while heating it to lower the viscosity of the oil. It is also useful as an oil leak sensor, etc.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of an optical cable type thermal sensor according to Embodiment 1 of the present invention, Figure 2 is an explanatory diagram conceptually showing an example of optical transmission loss measurement, and Figure 3 (al, (bl is optical transmission loss). A graph showing the measurement results, and FIG. 4 is a configuration diagram showing a constant temperature spot type thermal sensor according to the conventional technology. A coated optical fiber, 13 a pressure tape, 14 a metal tube, and 15 a backscattered light measuring device. Fig. M2

Claims (1)

[Claims] A central tensile strength wire having projections forming irregularities in the length direction on the surface, a coated optical fiber twisted around the central tensile strength wire, and a heat-shrinkable material wrapped around the coated optical fiber. 1. An optical cable type thermal sensor characterized by having an optical unit consisting of a presser wrapping tape.