JPWO2005091037A1 - Optical fiber cord - Google Patents

Abstract

An optical fiber cord according to the present invention includes an optical fiber (12), a spring cover (14) covering the outer periphery of the optical fiber (12), a net-like blade cover (16) covering the outer periphery of the spring cover, and a blade cover. And an outer cover (18) covering the outer periphery of (16).

Description

  The present invention relates to an optical fiber cord, and more particularly, to an optical fiber cord configured to regulate the bending radius of an optical fiber accommodated therein so as not to be a predetermined value or less.

  One of the most important requirements for an optical fiber cord that houses an optical fiber is to regulate the bending of the optical fiber cord so that the optical fiber does not bend at a bending radius smaller than its allowable bending radius. is there. If the optical fiber is bent below the allowable bending radius, the optical fiber core may be broken. For this reason, various structures that effectively prevent the bending of the optical fiber by restricting the bending radius so as not to become a predetermined value or less have been proposed and put into practical use.

  For example, Japanese Patent Application Laid-Open No. 3-231707 discloses an optical fiber cable in which an optical fiber is inserted into a flexible tube composed of a row of metal blocks connected to each other so as to be displaceable. ing. By housing the optical fiber in a metal flexible tube, the optical fiber is protected without being bent below the minimum bending radius of the flexible tube.

  When the optical fiber cord is actually used, it is preferable that the optical fiber cord is bent into a desired shape and then the shape is maintained, that is, plastically deformable. . For example, when an optical fiber cord is wired along a wall, it is preferable that the optical fiber cord is bent into a shape that matches the wall, and then the shape is maintained; the optical fiber cord is bent Returning to the original shape later complicates the work of wiring the optical fiber cord. In the optical fiber cable using the above-described flexible tube, when it is bent, a repulsive force against the contraction of the inner peripheral portion acts, and there is a tendency to return the bent state to a stable linear state. In other words, a known optical fiber cable often loses its wiring state after being wired in actual use.

  Accordingly, an object of the present invention is to provide an optical fiber cord having excellent shape retention (that is, plastically deformable) while suppressing the bending radius from becoming a predetermined value or less.

  In one aspect of the present invention, an optical fiber cord includes an optical fiber, a spring cover that covers the outer periphery of the optical fiber, a net-like blade cover that covers the outer periphery of the spring cover, and an outer periphery of the blade cover. An outer cover.

  Suitably, the said spring cover is comprised with the metal piece of the flat plate which was formed in the spiral shape and has elasticity. In this case, the spring cover is maintained in a state in which the side edges adjacent to each other are close to each other while being wound in a spiral shape.

  The blade cover is preferably formed of a net woven with metal wires.

  It is preferable that the optical fiber cord further includes a reinforcing fiber that is inserted between the spring cover and the blade cover and provided in a direction along the optical fiber.

  It is preferable that at least a part of the blade cover is embedded in the outer cover.

  The blade cover and the outer cover are preferably bonded to each other, and more preferably bonded to each other with an adhesive. As the adhesive, a thermosetting adhesive can be used. In a preferred embodiment, a one-component thermosetting silicone adhesive is used as the adhesive.

  The adhesive may be a room temperature curable adhesive. In a preferred embodiment, a one-component RTV rubber or a two-component RTV rubber is used as the adhesive.

  The outer cover is preferably formed from a heat-shrinkable resin.

  The outer diameter of the outer cover is preferably 3.0 mm or less. More preferably, the outer diameter of the outer cover is 2.0 mm or more.

FIG. 1 is a perspective view showing the configuration of the optical fiber cord of the first embodiment of the present invention; FIG. 2A is a partial cross-sectional view showing the position of an undesired optical fiber within the optical fiber cord; FIG. 2B is a partial cross-sectional view showing a preferred optical fiber position within the optical fiber cord. FIG. 3 is a perspective view showing the configuration of the optical fiber cord of the second embodiment of the present invention; FIG. 4 is a perspective view showing a configuration of an optical fiber cord according to the third embodiment of the present invention.

<First Embodiment>
FIG. 1 is a perspective view showing a configuration of an optical fiber cord 10 according to a first embodiment of the present invention. As shown in FIG. 1, the optical fiber cord 10 includes an optical fiber 12, a spring cover 14 that covers the outer periphery of the optical fiber 12, a net-like blade cover 16 that covers the outer periphery of the spring cover 14, An outer cover 18 that covers the outer periphery of the blade cover 16 is provided.

  As the optical fiber 12, an optical fiber having a general configuration can be used. In one embodiment, the optical fiber 12 has a core 12A made of pure silica glass having optical waveguide properties and extending along one direction, and a cladding layer 12B having a refractive index slightly higher than the refractive index of the core 12A. The clad layer 12B is provided with a core 12A and a protective layer 12C for protecting the clad layer 12B by covering the outer peripheral surface of the clad layer 12B.

  A well-known material can be employed for the core 12A and the cladding layer 12B. The core 12A and the clad layer 12B are not limited to being made of pure quartz glass. For example, if the optical waveguide property is ensured and the durability (life) is ensured, the core 12A and the cladding layer 12B are made of transparent plastics. It may be made of multi-component glass.

  The protective layer 12C is formed of a polymer synthetic resin, for example, UV acrylate or pyrocoat (trade name: manufactured by Lucent Specialty Fiber Technology (Connecticut, USA)). The protective layer 12C may be formed of a synthetic resin having a predetermined mechanical strength, for example, Tefzel (trade name: manufactured by Lucent Specialty Fiber Technology (Connecticut, USA)). The protective layer 12C is not an essential component of the optical fiber 12, and the optical fiber 12 can be configured even when the protective layer 12C is omitted.

  The spring cover 14 is formed of a long flat plate-like metal piece 14A having a spring property around a protective layer 12C of the optical fiber 12 in a spiral shape to form a tube shape, thereby being flexible and elastic against bending. It is possible to have sex. In this case, the spring cover 14 is spirally wound around the protective layer 12 </ b> C of the optical fiber 12, and the side edges adjacent to each other are kept close to each other and a slight gap is generated. The widths of the gaps 14B, 14C, 14D, 14E, 14F, 14G, 14H, and 14J between the adjacent side edges in FIG. 1 are almost the same when the optical fiber cord 10 is placed in a straight line. . As the material of the metal piece 14A, stainless steel such as SUS304AB which is easy to bend is suitable. However, iron, aluminum, other steel, etc. may be used.

  The blade cover 16 is for covering the outer periphery of the spring cover 14 and has a structure in which thin metal wires are assembled in a net shape. As the material, stainless steel such as SUS304 having a high tensile strength is suitable.

  The outer cover 18 is excellent in stretchability covering the outer periphery of the blade cover 16, and for example, heat shrinkable resin such as soft vinyl chloride having excellent waterproofness and oilproofness is used. In addition, flame-retardant vinyl chloride, heat-resistant vinyl chloride, polyethylene, fluororesin, polyurethane, silicon rubber, and the like can be used.

  The outer cover 18 and the blade cover 16 are bonded together. That is, the blade cover 16 contains an adhesive before the outer cover 18 is coated, and the outer cover 18 and the blade cover 16 are bonded to each other after the outer cover 18 is coated. The adhesive includes a heating adhesive and a room temperature curable adhesive, and any of these adhesives can be used. When a heating adhesive is used, a one-component thermosetting silicone adhesive that cures in a short time by heating is suitable. On the other hand, when a room temperature curable adhesive is used, a one-component RTV (Room Temperature Vulcanizing) rubber or a two-component RTV rubber having low viscosity, excellent workability, and excellent heat resistance and cold resistance is preferable. It will be apparent to those skilled in the art that other adhesives can be used.

  By pulling the outer cover 18 portion of the optical fiber cord 10 shown in FIG. 1 downward and bending the optical fiber cord 10, the spring cover 14 wound in a spiral shape around the protective layer 12C of the optical fiber 12 is also bent. In that case, the width of the gap between the adjacent side edges of the spring cover 14 changes, and the width G of the gaps 14B, 14C, 14D, 14E located at the outer periphery of the bend widens and is located at the inner periphery of the bend. The widths of the gap portions 14F, 14G, 14H, and 14J to be narrowed. When the bending radius is further reduced, the widths of the gaps 14F, 14G, 14H, and 14J in the inner periphery of the bending become zero, and adjacent side edges are in contact with each other. In this state, the bending radius cannot be reduced any further, and the bending radius becomes the minimum value.

となる。式（１）から最小曲げ半径Ｒｍｉｎを一定とすると，スプリングカバー１４の長尺の平板状の幅ｗを大きくし、スプリングカバー１４の側縁との隙間部の幅ｄを小さくすることによりスプリングカバー１４の巻き半径ｒを小さくすることができる。これにより、スプリングカバー１４によりスパイラル状に巻きつけられる光ファイバコード１０の細径化が容易に実現できる。Therefore, the minimum bending radius at which the widths of the gap portions 14F, 14G, 14H, and 14J at the side edges adjacent to each other on the inner peripheral portion of the spring cover 14 become zero matches the minimum bending radius at which the optical fiber 12 is not damaged. This is possible by setting the width of the gap portion of the spring cover 14 placed in a straight line in advance. The width of the long flat plate-like metal piece 14A of the spring cover 14 is w, the winding radius of the spring cover 14 wound spirally around the protective layer 12C of the optical fiber 12 is r, and the straight line before bending is placed. Assuming that the width of the gap with the side edge of the spring cover 14 is d, the minimum bending radius Rmin is:
Rmin = r · (w / d + 1).
When this equation is modified, the winding radius r of the spring cover 14 is expressed by the following equation:

It becomes. Assuming that the minimum bending radius Rmin is constant from the equation (1), the spring cover 14 is increased by increasing the long flat plate width w of the spring cover 14 and decreasing the width d of the gap with the side edge of the spring cover 14. The winding radius r of 14 can be reduced. Thereby, the diameter reduction of the optical fiber cord 10 wound spirally with the spring cover 14 is easily realizable.

  The optical fiber 12 is preferably located at the center of the optical fiber cord 10 even when the optical fiber cord 10 is bent. As shown in FIG. 2A, when the optical fiber 12 is out of the center of the optical fiber cord 10 when the optical fiber cord 10 is bent, the optical fiber 12 bends inside the optical fiber cord 10, and the optical fiber There is a possibility that the bending radius of 12 becomes larger than the bending radius of the optical fiber cord 10. This is not suitable for protecting the optical fiber 12. On the other hand, as shown in FIG. 2B, when the optical fiber 12 is positioned at the center of the optical fiber cord 10 even when the optical fiber cord 10 is bent, the bending radius of the optical fiber 12 is as follows. The bend radius of the cord 10 is kept the same.

  Since the blade cover 16 in which thin metal wires are assembled in a mesh shape covers the outer periphery of the spring cover 14, the mesh metal is formed in the gap portions 14B, 14C, 14D, and 14E located at the outer periphery of the spring cover 14 in bending. The thin wire made of metal shrinks in the width direction and extends in the vertical direction, and in the gap portions 14F, 14G, 14H, and 14J located in the inner periphery of the bend, the thin metal wire made of net-like metal extends in the width direction and contracts in the vertical direction. Due to such expansion and contraction of the blade cover 16, it is possible to realize the minimum bending radius of the spring cover 14.

  The outer cover 18 is bonded to the blade cover 16. For this reason, it is possible to prevent the outer cover 18 from pulling the optical fiber 12 too much and damaging the optical fiber 12, and to prevent peeling of the coating around the neck of the optical connector connected to the end of the optical fiber cord.

  The minimum bending radius of the spring cover 14 is realized when the widths of the gap portions 14F, 14G, 14H, and 14J in the inner peripheral portion of the spring cover 14 are zero and adjacent side edges are in contact with each other. . Further, the blade cover 16 has a structure in which fine metal wires are assembled in a net shape, and the outer cover 18 is a heat-shrinkable resin having elasticity, so that even if the optical fiber cord 10 is bent with a minimum radius, the blade cover 16 is not bent. The repulsive force hardly works on the inner circumference. More specifically, when an external force is applied to the optical fiber cord 10 to bend the optical fiber cord 10 into a desired shape, the position of the wire constituting the blade cover 16 moves minutely. Since the outer cover 18 has an action of holding the position of the wire, the optical fiber cord 10 remains bent into a desired shape even when the action of an external force is lost. Therefore, even if the optical fiber cord 10 is bent and wired in a place with a small radius, the wiring state does not collapse, and shape maintainability can be reliably achieved.

  The spring cover 14 wound in a spiral shape around the protective layer 12C of the optical fiber 12 can be easily realized by a normal coil forming machine for spiral forming. Therefore, the inexpensive optical fiber cord 10 can be manufactured. In this normal spiral forming coiling machine, the ratio d / w between the width w of the flat metal piece wound around the spiral and the width d of the gap between the metal pieces wound spirally is about 0. It is the most suitable condition for production to be about 1 to 0.15. Since the minimum bending radius Rmin of the optical fiber 12 is about 10 mm, if this value is the minimum bending radius of the spring cover 14, the winding radius r of the spring cover 14 is substituted into the above formula (1) by 0.9 mm. Or 1.3 mm, and 1 mm to 1.5 mm when the thicknesses of the blade cover 16 and the outer cover 18 are taken into consideration. Therefore, the outer diameter of the optical fiber cord 10 is appropriately 2 mm or more and 3 mm or less.

<Second Embodiment>
FIG. 3 is a perspective view showing a configuration of an optical fiber cord 10A according to the second embodiment of the present invention. In the present embodiment, a reinforcing fiber 15 is inserted between the spring cover 14 and the blade cover 16 so that the outside of the spring cover 14 is aligned in the same direction as the optical fiber 12. Except for this point, the optical fiber cord 10A of the second embodiment has the same configuration as the optical fiber cord 10 of the first embodiment.

  The reinforcing fiber 15 is for increasing the tensile strength of the optical fiber cord 10 by extending the outer side of the spring cover 14 in the same direction as the optical fiber 12, and is an aromatic having excellent cut resistance, friction resistance, and heat resistance. Polyamide fibers are preferably used. A plurality of thin aromatic polyamide fibers are bundled into one bundle, and a plurality of bundles of reinforcing fibers 15 are incorporated into the optical fiber cord 10 according to the purpose. FIG. 2 shows a case where the reinforcing fiber 15A, the reinforcing fiber 15B, the reinforcing fiber 15C, and the back side (not shown) have a total of four bundles. It will be apparent to those skilled in the art that the number of bundles of reinforcing fibers 15 is not limited to four.

  A tensile test was performed for the case where the reinforcing fiber 15 was not incorporated into the optical fiber cord 10 and the case where the bundle of reinforcing fibers 15 was incorporated. As the reinforcing fiber 15, Kevlar (registered trademark of DuPont, USA) was used. As a result, it was confirmed that when one bundle of reinforcing fibers 15 was incorporated, the tensile strength was increased about 1.5 times compared to when no reinforcing fibers 15 were incorporated. Thus, by incorporating the reinforcing fiber 15 into the optical fiber cord 10, the tensile strength can be dramatically increased.

<Third Embodiment>
FIG. 4 is a cross-sectional view showing a configuration of an optical fiber cord 10B according to the third embodiment of the present invention. In the optical fiber cord 10 of the first embodiment, the outer cover 18 is bonded to the outer surface of the blade cover 16, but in the optical fiber cord 10B of the present embodiment, the blade cover 16 is embedded in the outer cover 18. Except for this point, the optical fiber cord 10B of the third embodiment has the same configuration as the optical fiber cord 10 of the first embodiment.

  The structure in which the blade cover 16 is embedded in the outer cover 18 is effective for improving shape retention. As described above, when an external force is applied to the optical fiber cord 10 in order to bend the optical fiber cord 10 to a desired shape, the position of the wire constituting the blade cover 16 moves minutely. The outer cover 18 has an action of maintaining the position of the wire. The structure in which the blade cover 16 is embedded in the outer cover 18 enhances the action of the outer cover 18 holding the wires constituting the blade cover 16, thereby effectively improving the shape retainability of the optical fiber cord 10.

  The blade cover 16 need not be entirely embedded in the outer cover 18. However, as shown in FIG. 4, when the entire blade cover 16 is embedded in the outer cover 18, the outer cover 18 strengthens the action of holding the wire of the blade cover 16, and the shape of the optical fiber cord 10 is retained. It is suitable for improving the effect effectively.

  The blade cover 16 is embedded in the outer cover 18 and the blade cover 16 is bonded to the outer cover 18 with an adhesive, which is effective for further improving the shape retention. In this case, after the adhesive is applied to the surface of the blade cover 16, the blade cover 16 is molded with resin, whereby the blade cover 16 is embedded in the outer cover 18. As the adhesive, a one-component heat-curable silicone adhesive, a one-component RTV rubber, and a two-component RTV rubber can be suitably used.

  The present invention should not be construed as limited to the embodiments described above. It will be apparent to those skilled in the art that various modifications can be made to the present invention without departing from the scope of the following claims.

Claims (16)

Optical fiber,
A spring cover covering the outer periphery of the optical fiber;
A net-like blade cover covering the outer periphery of the spring cover;
An optical fiber cord comprising: an outer cover that covers an outer periphery of the blade cover. The optical fiber cord according to claim 1, wherein the spring cover includes an elastic flat metal piece formed in a spiral shape. The optical fiber cord according to claim 2, wherein the spring cover is maintained in a state in which adjacent side edges are close to each other in a spirally wound state. The optical fiber cord according to claim 1, wherein the blade cover includes a net made of a metal wire. The optical fiber cord according to claim 1, further comprising a reinforcing fiber inserted between the spring cover and the blade cover and provided in a direction along the optical fiber. The optical fiber cord according to claim 1, wherein at least a part of the blade cover is embedded in the outer cover. The optical fiber cord according to claim 1, wherein the blade cover and the outer cover are bonded to each other. The optical fiber cord according to claim 7, wherein the blade cover and the outer cover are bonded by an adhesive. The optical fiber cord according to claim 8, wherein the adhesive is a thermosetting adhesive. The optical fiber cord according to claim 9, wherein the heat curable adhesive is a one-component heat curable silicone adhesive. The optical fiber cord according to claim 8, wherein the adhesive is a room temperature curable adhesive. The optical fiber cord according to claim 9, wherein the room temperature curable adhesive is a one-component RTV rubber. The optical fiber cord according to claim 9, wherein the room temperature curable adhesive is a two-component RTV rubber. The optical fiber cord according to claim 1, wherein the outer cover is made of a heat-shrinkable resin. The optical fiber cord according to claim 1, wherein an outer diameter of the outer cover is 3.0 mm or less. The optical fiber cord according to claim 15, wherein an outer diameter of the outer cover is 2.0 mm or more.

Images