JP6609469B2 - Optical fiber cable for strain measurement and manufacturing method thereof - Google Patents

Description

  The present invention relates to an optical fiber cable for strain measurement in which an optical fiber is inserted into a metal tube in order to measure strain of a structure, a crust, and the like using an optical fiber, and a manufacturing method thereof.

  2. Description of the Related Art Optical fiber cables that are sensitive to strain and can easily measure strain are widely used to measure strain of structures, crusts, and the like. Since an optical fiber is easily damaged when exposed, it is used as an optical fiber cable inserted into a metal tube or the like as a protective member for protection. When such an optical fiber cable is arranged at a location to be measured such as a structure or the crust, if the stress received by the metal tube from the location to be measured can be transmitted as it is to the optical fiber in the metal tube, the strain of the optical fiber is measured. The strain at the location to be measured can be measured. Therefore, it is required that the metal tube and the optical fiber behave integrally.

  In order to fix the optical fiber integrally to the metal tube, in Patent Document 1, an optical fiber coated with a resin is inserted into the metal tube, and mechanical pressure is directly applied to the metal tube from the outside. This metal tube is compressed and caulked in the inner diameter direction, and the optical fiber is fixed to the metal tube so that a constant frictional force is generated between the optical fiber and the inner wall of the metal tube. The caulking is performed in the longitudinal direction of the optical fiber at a position having an interval of, for example, 1 mm or more according to Patent Document 1.

  Patent Document 2 discloses an optical fiber cable in which an optical fiber is inserted into a stainless steel tube serving as a protective tube, and a gap in the tube is filled with a filler to integrate the optical fiber and the stainless steel tube. .

JP 2001-281077 A JP-A-11-0945547

  However, in Patent Document 1, since the metal tube is caulked from the outside, a local force is applied to the optical fiber, the optical fiber is damaged during caulking, or the optical fiber deteriorates with time during long-term use. There is a concern of losing reliability.

  On the other hand, Patent Document 2 does not explain how to fill the metal tube with the filler, but it is difficult to fill from the open end after the metal tube is formed into a long shape. That is, in the process of forming a metal pipe by joining and welding its side edges while feeding out the metal tape, it is common to use a method in which a filler is injected simultaneously with the insertion of an optical fiber from the opening side of the metal pipe It is. In order to make the optical fiber and the metal tube behave integrally, it is necessary to fill the metal tube with a filler so that there is no gap, but if you try to fill the filler without leaving a gap in the metal tube, There is a concern that the filler may leak from the opening side, or that welding failure may occur at the butt portion due to the influence of adhesion of the leaked filler.

  Furthermore, in this way, when the filler is injected by applying injection pressure in order to fill the filler into the metal tube without gaps, the optical fiber is inserted from the opening side under the injection pressure. When injected together, tension is applied to the optical fiber due to the injection pressure of the filler, making it difficult to secure the slack (extra length) of the optical fiber, and the tension becomes particularly large on the opening side, resulting in the longitudinal direction of the optical fiber. There is also a problem of optical fiber functionality that makes it difficult to maintain the uniformity of slack. This tendency is further increased when the injection pressure is increased.

  In view of such circumstances, the present invention fills the metal tube with a filler without leaving a gap in the metal tube, and ensures the extra length while appropriately securing the extra length without damaging the optical fiber or reducing the reliability. It is an object of the present invention to provide a strain-measuring optical fiber cable that can integrate an optical fiber with a metal tube, and a manufacturing method thereof.

  According to the present invention, the above-described problems are solved by an optical fiber cable configured as follows and a manufacturing method thereof.

<Optical fiber cable>
An optical fiber cable for strain measurement of the present invention has an optical fiber arranged in a metal tube. In the present invention, the metal tube has holes for filling material injection at a plurality of locations distributed in the longitudinal direction, The tube is filled with a filler, and the metal tube integrally holds the optical fiber through the filler.

  In the optical fiber cable of the present invention having such a configuration, the filler in a flowing state is injected into the metal tube from the plurality of holes distributed in the longitudinal direction of the metal tube into the metal tube without damaging the optical fiber. Moreover, the metal tube is filled without any gaps at any position in the longitudinal direction. The filling material hardens with time after filling, and the metal tube integrally holds the optical fiber through the filling material. As a result, when the metal tube receives an external force and generates stress, the stress is transmitted to the optical fiber through the filler, and the strain of the metal tube can be measured.

  In the present invention, the metal tube is preferably provided with holes distributed in the longitudinal direction and the circumferential direction. Thus, if the holes are distributed not only in the longitudinal direction but also in the circumferential direction, the filler can be easily filled and the optical fiber is naturally positioned at the center of the metal tube. Become.

  In the present invention, the hole is preferably located in a spiral shape with the longitudinal direction of the metal tube as the axis. Thus, by positioning the hole in a spiral shape, the hole is uniformly distributed in both the longitudinal direction and the circumferential direction, so that the strength reduction of the metal tube due to the formation of the hole is small and the filler The filling is also made uniform.

  In the present invention, the metal tube is preferably filled with a filler in the hole, and the hole is locked to the filler in the axial direction. By doing so, even if the filler is a hole, the metal tube is locked with the metal tube, so that the holding force when the metal tube integrally holds the optical fiber via the filler is increased.

  In the present invention, it is preferable that the inner peripheral surface of the metal tube is a rough surface, and the filler is locked to the inner peripheral surface in the axial direction. By doing so, the holding force when the metal tube integrally holds the optical fiber through the filler is further increased.

  In the present invention, the metal tube may have a sealing member provided on the outer peripheral surface of the metal tube, and the hole portion may be sealed with the sealing member. By doing so, the filler in the hole is not covered with the sealing member and exposed to the external environment, so that the deterioration of the filler due to the external environment in the hole can be prevented, and the metal tube has a hole. The amount of strength reduction of the metal tube due to the formation of the portion can be reinforced with the sealing member.

  In the present invention, the outer peripheral surface of the metal tube may be a rough surface, and a coating layer may be provided on the outer peripheral surface. When forming the coating layer, the outer peripheral surface of the metal tube is rough, so that the coating layer is securely held by the metal tube.

<Manufacturing method>
According to the present invention, the above-described strain-measuring optical fiber can be manufactured by a manufacturing method having the following configuration. The method according to the present invention uses a metal tape provided with holes distributed in the longitudinal direction. In a method of manufacturing a strain-measuring optical fiber cable in which an optical fiber is disposed in a metal tube formed by welding after being abutted at the side end edge, from the outside of the metal tube to the inside of the metal tube through the hole of the metal tube After the filling material is filled, the optical fiber is integrally held by the metal tube through the filling material.

  In the method of the present invention having such a configuration, the filler is transferred from the hole to the inside of the metal pipe by passing the metal pipe welded to the butt portion through the filler bowl filled with the fluidized filler. And is uniformly and easily filled at any position in the longitudinal direction of the metal tube.

  The filler is cured with the passage of time after filling, and the metal tube integrally holds the cable through the filler.

  The present invention fills the metal tube into which the optical fiber has been inserted as described above, filling the metal tube with the filler distributed from the hole portion provided in the metal tube in the longitudinal direction, and the optical fiber to the metal tube through the filler. Therefore, the filling material can be easily and uniformly filled in the metal tube without any gap without damaging the optical fiber in the metal tube, and the metal tube and the optical fiber can be connected to each other. Make sure they are integrated. In addition, the extra length can be secured and the extra length can be made uniform in the longitudinal direction. In the present invention, according to the above-described method for manufacturing a strain-measuring optical fiber cable, the filler can be easily and uniformly filled.

1 shows an optical fiber cable as an embodiment of the present invention, in which (A) is a plan view of a metal tape before forming a metal tube of the optical fiber cable, and (B) is a perspective view showing a part of the optical fiber cable. It is. 1B shows a manufacturing apparatus for the optical fiber cable of FIG. 1B, FIG. 1A is a schematic configuration diagram of the apparatus, and FIG. 1B is an enlarged view of the optical fiber cable in the manufacturing process in the filler tank of FIG. It is sectional drawing. The optical fiber cable as other embodiment of this invention is shown, (A) is a perspective view which shows a part of optical fiber cable, (B) is a schematic block diagram of the manufacturing apparatus for it.

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

  Regarding the strain-measuring optical fiber cable of this embodiment, an optical fiber is inserted into a long metal tube and a filler is filled therein.

  FIG. 1 is a plan view of the optical fiber cable before the metal tube is formed into a tubular shape in FIG. 1 (A), and the metal tape is formed into a metal tube in FIG. 1 (B). The metal tubes are respectively shown in perspective views with the optical fiber inserted and filled with filler.

  The metal tape 11 in FIG. 1A is a material suitable as a metal tube for an optical fiber cable, for example, a tape of a material such as stainless steel, iron, aluminum, nickel, etc., and is obtained in a state of being wound around a drum or the like. Is possible. The expanded metal tape 11 has small-diameter holes 11A formed at intervals in the longitudinal direction. In the present embodiment, the holes 11A are formed at regular intervals in the longitudinal direction. The holes 11A are provided in a distributed manner on a line inclined in the longitudinal direction from one width direction side edge to the other width direction side edge with a plurality of pieces, for example, every 5 pieces in the illustrated example as one segment. As shown in FIG. 1B, when the metal tape 11 is joined at the side edges in the width direction and formed as the metal tube 12, the plurality of holes 11A are arranged in the longitudinal direction of the metal tube 12. It comes to be located in a spiral as an axis. The position of the hole 11A may be a ring shape instead of a spiral shape.

  The metal pipe 12 has a joint portion 12A in which the side edges in the width direction of the metal tape 11 are joined and welded in the longitudinal direction, and one or a plurality of optical fibers 13 are inserted therein, and the interior space is substantially The filler 14 is filled with no gap, and the metal tube 12 integrally holds the optical fiber 13 through the filler 14 to form the optical fiber cable 10 of the present embodiment. That is, when the metal tube 12 is distorted by receiving an external force, the stress due to the strain is reliably transmitted to the optical fiber 13 through the filler 14.

  Such an optical fiber cable 10 is manufactured by the apparatus shown in FIG.

  In this apparatus, while the metal tape 11 is fed out, the metal tape 11 is rolled in the width direction and joined as a tube to form a metal tube 12, and at the same time, an optical fiber 13 is inserted into the metal tube 12 to manufacture the metal tube 12. An optical fiber cable 10 suitable for strain measurement is obtained by filling a filler 14 into a metal tube 12 by a line.

  The metal tape 11 is wound around a drum D1 that is rotatably supported. The metal tape 11 is drawn out from the drum D1, passes through a turning roller 21, and is fed to the tip of the metal tape 11 in the feed direction (FIG. 2A). To the right).

  On the other hand, the optical fiber 13 is wound around a bobbin B that is rotatably supported, pulled out from the bobbin B, and fed forward through a turning roller 22.

  The diverting roller 21 and the diverting roller 22 are arranged close to each other, and the metal tape 11 and the optical fiber 13 to be fed run substantially on the same line ahead of the diverting rollers 21 and 22. Yes.

  A metal tube forming device 23 having a tube-forming roll pair 23A, 23B, 23C, 23D and the like is disposed at a position ahead of the turning rollers 21 and 22. In the metal tube forming apparatus 23, the metal tape 11 is sequentially bent in the width direction by the tube-forming roll pairs 23A, 23B, 23C, and 23D provided at a plurality of locations, and the bending amount is gradually increased to make the final structure. In the tube roll 23D, the metal tape 11 has a tubular shape in which the side edges in the width direction are butted together.

  A laser welding device 24 is provided at the end of the metal tube forming device 23, and the butted portion of the tubular metal tape 11 is laser-welded to form a metal tube 12 having a joint 12A.

  On the other hand, the optical fiber 13 is sent out toward the metal tube forming device 23, and when the metal tape 11 is formed into a tubular shape by the tube forming rolls 23A to 23D, the optical fiber 13 is formed at the left side position that is in front of the metal tape 11 in the feed direction. It is fed into the metal tube 12 from the tube roll 23A side. A method and an apparatus for inserting the optical fiber 13 into the metal tube 12 while the metal tape 11 is made into the metal tube 12 by the tube-making rolls 23A to 23D and the laser welding device 24 are well known, and detailed description thereof is omitted. To do.

  At the tip of the laser welding device 24, a filling device 25 for filling the metal tube 12 with the filler 14 through the hole 11A of the metal tube 12 is disposed. The filling device 25 is in a fluid state and contains a filling material tank 25A containing a filling material 14 that hardens over time, and a filling material supply device 25B that supplies the filling material 14 to the filling material tank 25A. And a pressurizing device 25C such as a compressor for pressurizing the filler 14 in the filler tank 25A through the filler in the filler supply device 25B. As a material for the filler that cures with time after being filled into the metal tube, a silicone resin, an epoxy resin, or the like that cures at room temperature (the former) can be used. As other fillers, a thermosetting resin in which the filler is cured by heating after injecting a filler having fluidity at room temperature or a filler having fluidity in a heated state is injected over time. A thermoplastic resin (the latter) that cures by lowering the temperature can also be used. There are various types of fillers that cure over time, but the latter requires both a thermosetting resin and a thermoplastic resin to heat the filler, so in the present invention, the former is kept at the normal temperature. Curing fillers are suitable because of their excellent manufacturability. Examples of silicone resins include silicone rubber. There are silicone rubbers that cure at room temperature and those that cure when heated, but those that cure at room temperature have fluidity when filled and existed in the metal tube when injected into the metal tube. Examples include those that react with moisture in the air and cure with time after filling.

  Specific examples of the former resin that cures over time at room temperature include silicone rubber TSE39 series (TSE3975, TSE3995, etc.) manufactured by Momentive Performance Materials, and silicone manufactured by Shin-Etsu Chemical Co., Ltd. Examples thereof include rubber KE-48 series (KE-4895, KE-4896, KE-4897, etc.). These silicone rubbers have elasticity after curing, and excessive stress is applied to the optical fiber even after the filler is cured while holding the optical fiber and the metal tube integrally through the filler. Can be prevented.

  The filling material tank 25A is formed with an opening through which the metal tube 12 into which the optical fiber 13 is inserted passes, and the opening is pressurized in the filling material tank 25A when the metal tube 12 is penetrated. The sealing material 14 is sealed with a sealing member so as not to leak from between the metal tubes 12 to the outside through the opening. Thus, the filler 14 is filled into the metal tube 12 through the hole 11A, and the optical fiber cable 10 is obtained.

  Further, a winding device 26 is disposed at the front side of the filling device 25. The winding device 26 has a drum D2 for winding the optical fiber cable 10 obtained by filling the metal tube 12 into which the optical fiber 13 is inserted with the filler 14.

  According to such an apparatus, the metal tape 11 having the holes 11 </ b> A distributed in the longitudinal direction of the metal tape 11 passes through the turning roller 21 and reaches the metal tube forming apparatus 23. The metal tape 11 is formed into a tubular shape by gradually increasing the amount of bending by the tube forming rolls 23A to 23D. On the other hand, the single or plural optical fibers 13 reach the metal tube forming device 23 through the deflecting roller 22 and are inserted from the entrance side (left side in FIG. 2) of the portion where the metal tape 11 is tubular. The side edges in the width direction of the metal tape 11 that are tubular are welded by a laser welding device 24 to form a joint 12A, and the metal tube 12 is formed. The optical fiber 13 is inserted forward in the metal tube 12.

  The metal tube 12 in which the optical fiber 13 is inserted travels through the filler tank 25A of the filling device 25.

  The filler 14 in the fluidized state in the filler tank 25A is pressurized by the pressurizing device 25C through the filler 14 in the filler supply device 25B. When the metal tube 12 in which the optical fiber 13 is inserted travels through the filler tank 25A, when the metal tube 12 enters the filler tank 25A, as shown in FIG. Is surrounded by the filler 14 in the pressurized state, and the filler 14 in the fluidized state flows into the metal tube 12 through the holes 11A of the metal tube 12. The holes 11A are formed distributed in the longitudinal direction of the metal tube 12, and the filler 14 flows into the metal tube 12 radially inward from the holes 11A. Since the optical fiber 13 is uniformly filled in the longitudinal direction and does not cause the optical fiber 13 to be tensioned in the longitudinal direction, the optical fiber 13 maintains a uniform extra length (slack) in the longitudinal direction. In this way, the filler 14 is filled into the metal tube 12 uniformly and without gaps in the longitudinal direction. In the example of the metal tube 12 in FIG. 1B, the holes 11A are also distributed in the circumferential direction, so that the optical fiber 13 receives the inflow pressure of the filler toward the inside in the radial direction over the entire circumference. It comes to lie on the center line of the metal tube 12.

  The filler 14 filled in the metal tube 12 gradually hardens in the process of the optical fiber cable 10 in which the metal tube 12 is filled with the filler 14 passing through the filler tank 25A toward the winding device 26. The metal tube 12 and the optical fiber 13 are fixed to each other so that the metal tube 12 integrally holds the optical fiber 13 via the filler 14, thus obtaining the strain-measuring optical fiber cable 10. The take-up device 26 is wound around the drum D2 to prepare for use.

  In the optical fiber cable 10 thus manufactured, if the filler 14 enters the hole 11A of the metal tube 12 as well, the axis of the filler 14 is the axis relative to the metal tube 12 even if the hole 11A. Since the metal tube 12 is firmly locked in the direction, the effect of the metal tube 12 holding the optical fiber 13 integrally through the filler 14 is enhanced.

  Next, another embodiment of the present invention will be described. In the optical fiber cable 10 shown in FIG. 3A, a tape-shaped sealing member 15 that covers the hole 11 </ b> A is spirally wound around the outer peripheral surface of the metal tube 12. In this embodiment, since the hole 11A is covered with the sealing member 15, the filler 14 in the metal tube 12 is not exposed to the outside through the hole 11A. Therefore, even when the optical fiber cable 10 is used for a long period of time, the filler 14 can avoid a situation of deterioration due to contact with the external environment at the position of the hole 11A.

  Furthermore, since the sealing member 15 covers the hole portion 11A, the metal tube 12 can be reinforced and the strength reduction due to the formation of the hole portion 11A of the metal tube 12 can be minimized. In the present embodiment, since the hole 11 </ b> A is located in a spiral with respect to the metal tube 12, the sealing member 15 may be wound around the metal tube 12 in a spiral manner. If the sealing member 15 is a metal tape, it can be welded and attached to the metal tube 12. FIG. 3B shows a sealing member mounting apparatus in such a form.

  In FIG. 3B, a rotation applying device 27 that supports the drum D2 supported by the winding device 26 in FIG. 2 is disposed at the left end. The rotation applying device 27 includes a fixed support base 27A and a rotation support portion 27B that receives a driving force so as to rotate with respect to the fixed support base 27A about an axis X oriented in the lateral direction in FIG. 3B. The rotation support portion 27B supports the drum D2 removed from the winding device 26 so that the direction perpendicular to the paper surface is the axis Y of the drum D2. . Therefore, the drum D2 is rotatable around its own axis Y, and the entire drum D2 rotates together with the rotation support portion 27B around the axis X.

  On the other hand, a drum D3 around which a metal tape 15A serving as a sealing member is wound is disposed at the left end position of the apparatus, and the metal tape 15A is pulled out. At the right end of the apparatus, there is provided a rotation applying device 28 having the same configuration as the rotation applying device 27 at the left end described above, and the rotation support portion 28A rotating around the axis X at the same speed. The rotation applying device 28 is arranged in the direction of the axis X opposite to the rotation applying device 27, and an empty drum D4 is supported by the rotation support portion 28B at the beginning of operation.

  Further, two laser welding devices 29 and 30 are disposed adjacent to the optical fiber cable 10 at the front position of the drum D3 of the metal tape 15A. The distance between the two laser welding devices 29 and 30 is substantially equal to the width of the metal tape 15A.

  In the apparatus of FIG. 3B, the drum D2 wound with the optical fiber cable removed from the winding device 26 is supported by the rotation support portion 27B of the rotation applying device 27 at the left end, and the empty drum D4 is used. Is supported by the rotation support portion 28B of the rotation-equipped device 28 at the right end, and the optical fiber cable 10 is rotated around its axis X while being pulled out from the drum D2 and wound around the drum D4. The metal tape 15A drawn from the drum D3 is wound around the optical fiber cable 10. The winding position is determined so as to coincide with the hole 11 </ b> A formed in the metal tube 12 of the optical fiber cable 10. In this way, when the optical fiber cable 10 travels around the axis X by the two rotation support devices 28, 30 while being pulled out from the left end drum D2 and wound around the right end drum D4, The metal tape 15 </ b> A is spirally wound around the outer circumference of the metal tube 12 so as to cover the hole 11 </ b> A and is formed as a sealing member 15. At that time, the sealing member 15 is welded and attached to the metal tube 12 by two laser welding devices 32 and 33 on both side edges. The sealing member may cover the entire outer peripheral surface of the metal tube as a wide tape or sheet member, rather than a tape having a width corresponding to the diameter of the hole as shown. Moreover, as a material of sealing member itself, resin and a fiber material may be sufficient besides the illustrated metal.

  The present invention can be further modified in addition to the illustrated embodiment. For example, the surface of the metal tape forming the metal tube can be made rough to improve the locking force with the resin. If the inner surface of the metal tube is made rough, the locking force between the filler filled in the metal tube and the metal tube is improved, and the holding force of the optical fiber through the filler of the metal tube is made stronger. If the outer surface of the metal tube is a rough surface, an optical fiber cable having improved locking force between the coating layer and the metal tube when a coating layer is provided on the outer peripheral surface of the metal tube is obtained.

DESCRIPTION OF SYMBOLS 10 Optical fiber cable 11A Hole part 12 Metal pipe 13 Optical fiber 14 Filler 15 Sealing member

Claims (8)

In strain-measuring optical fiber cables in which optical fibers are arranged in metal tubes,
The metal tube has holes for injecting filler at a plurality of locations distributed in the longitudinal direction. The metal tube is filled with the filler, and the metal tube integrally holds the optical fiber through the filler. An optical fiber cable for strain measurement, characterized by   2. The strain-measuring optical fiber cable according to claim 1, wherein the metal tube is provided with holes distributed in the longitudinal direction and the circumferential direction.   The strain-measuring optical fiber cable according to claim 1 or 2, wherein the hole is helically positioned with the longitudinal direction of the metal tube as an axis.   The strain measurement according to any one of claims 1 to 3, wherein the metal tube has a hole filled with a filler, and the hole is locked with the filler in an axial direction. Fiber optic cable.   5. The strain measurement light according to claim 1, wherein the metal tube has a rough inner peripheral surface and a filler is axially locked to the inner peripheral surface. Fiber cable.   6. The metal tube according to claim 1, wherein a sealing member is provided on an outer peripheral surface of the metal tube, and a hole is sealed with the sealing member. Optical fiber cable for strain measurement. Metal tube forms a rough surface outer peripheral surface, a strain measuring according to one of claims 1 to 6 coating layer on the outer peripheral surface and that are provided to lock Fiber optic cable. In a method of manufacturing a strain-measuring optical fiber cable in which an optical fiber is arranged in a metal tube formed by welding metal tapes provided with holes distributed in the longitudinal direction at the side edges thereof, and then welding them ,
An optical fiber cable for strain measurement, comprising filling a filler from the outside of the metal tube into the metal tube through the hole of the metal tube, and then holding the optical fiber integrally with the metal tube via the filler. Manufacturing method.

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