JP2013045038A - Optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber cable that secures a sheath thickness capable of preventing increase in transmission loss, allows a tear string to linearly tear a cable without being twisted, and is capable of acknowledging a print on a projection thread part.SOLUTION: An optical fiber cable 1 has a hollow structure in which a plurality of coated optical fibers 4 are accommodated in a fiber housing part 3 provided on a sheath 2. In the sheath, there are provided tear strings 9 buried at the location in the vicinity of the fiber housing part in a cable lengthwise direction, and projection thread parts 11 each having a flat-surface tear face 12 at a corresponding part to the tear string 9 on a straight line X connecting the tear string 9 and the cable center axis, and tear position deviation prevention parts 13 provided on both side edges 12a and 12b of the tear face 12 and preventing positional deviation from occurring when the tear string 9 is torn.

Description

  The present invention relates to an optical fiber cable having a structure for tearing a jacket by pulling a tear string.

  For example, in a hollow optical fiber cable in which an optical fiber core wire is directly covered with a sheath (outer jacket), a tear string (also referred to as a lip cord) is placed in the length of the cable in order to facilitate the intermediate post-branching operation. It is embedded in the direction (for example, described in Patent Documents 1, 2, 3, etc.).

  The sheath has a ridge that functions to prevent the increase in transmission loss due to insufficient sheath thickness during an impact test that drops the weight on the cable and a mark function that indicates the position of the tear string when the optical fiber core is taken out from the optical fiber cable. The part is formed.

  The protruding portion is formed in the longitudinal direction of the cable with a semicircular cross-sectional shape. The ridge portion is more excellent in impact resistance as the sheath thickness on the tear string is thicker, but the tearing force of the sheath by the tear string is increased, the tearability is lowered, and the workability is deteriorated. Therefore, it is necessary to form the ridge portion to a thickness that satisfies both.

JP 2001-343569 A JP 2002-98868 A JP 2002-341212 A

  By the way, when the tear string under the semicircular ridge part is taken out and torn in the longitudinal direction of the cable, the cable is twisted by the tear string coming out from the boundary between the ridge part and the cable in the middle of the tear . Therefore, when the wrist holding the cable is twisted, the wrist is burdened and the workability is deteriorated.

  In addition, the optical fiber cable is printed to identify the type and company name and to indicate the length. Main printing methods include hot stamp printing and inkjet printing. Hot stamp printing is a method of imprinting with a heated letterpress stamp via an ink ribbon and transferring it to a cable with excellent identification, friction, abrasion, and weather resistance. It is easy to generate. Ink jet printing sprays ink onto the cable, so it is not easily affected even if the cable surface is uneven. Inkjet printing is excellent in cost reduction because it is not necessary to prepare a stamp for each cable type. However, ink-jet printing has a feature that it is more easily worn away than hot stamp printing due to rubbing or the like when laying cables. Generally, a printing method is selected depending on the application and specifications.

  In each of the optical fiber cables of Patent Documents 1 to 3, there is a convex portion (protruding portion) at a position facing the outer jacket, and a portion directly below the convex portion is a tear string. In addition, this optical fiber cable has a structure in which a tensile body is provided at a position where the position of the lip cord is rotated 90 degrees around the cable, and an optical fiber is disposed at the center of the cable. Since the strength member is formed of, for example, a steel wire, a drag force is generated against tension and compression. Therefore, when the cable is bent, it is not bent in the direction of the line connecting the two strength members, and can be bent only in the direction of the line connecting the two lip cords.

  When the optical fiber cable is wound around the drum, it bends only in the direction of the line connecting the two tear strings, so that the ridge portion just above it can be seen on the surface of the cable. On the other hand, when the optical fiber cable is wound around the drum, it is important that printing can be confirmed for cable identification and remaining length management, so printing is performed on the protruding portion of the cable.

However, when printing with a hot stamp on the ridge, printing is likely to be lost due to the convex shape, causing a problem in discrimination.
Therefore, the present invention is an optical fiber cable that can ensure a sheath thickness that can prevent an increase in transmission loss, can be torn linearly without being twisted by a tearing string, and can recognize printing on the ridge. The purpose is to provide.

  The invention according to claim 1 is a hollow-structure optical fiber cable in which a plurality of optical fiber cores are housed in a fiber housing portion provided in the sheath, and the sheath includes a tensile body embedded in a longitudinal direction of the cable; A tear string embedded in the longitudinal direction of the cable in a position near the fiber storage portion, a tear surface having a flat surface, and both side edges of the tear surface, corresponding to the tear string on the line connecting the tear string and the cable central axis And a ridge portion having a tearing position deviation preventing portion for preventing a position deviation when the sheath is torn by pulling the tear string.

  Invention of Claim 2 is the optical fiber unit of Claim 1, Comprising: The said protrusion part is made into the trapezoid shape which made the said tear surface the upper base, the upper base is L1, and the lower base is L2. In this case, L1 + 0.5 <L2 <L1 + 1.5.

  A third aspect of the present invention is the optical fiber unit according to the first or second aspect, wherein a V-shaped groove is provided on the tear surface.

  According to the present invention, the protrusion on the tear string is provided with a misalignment prevention part that prevents misalignment when the tear string is torn, so that the misalignment prevention part prevents the tear position from shifting, The tear string can be teared linearly at the tear plane. Therefore, since the cable is not twisted, workability can be facilitated without placing a burden on the wrist gripping the cable. In addition, since the surface of the ridge is a flat tear surface, printing by the hot stamp on the tear surface is clear and the discrimination is high.

FIG. 1 is a cross-sectional view of the optical fiber cable of this embodiment. FIG. 2 is an enlarged cross-sectional view of the main part of the protrusion of the optical fiber cable shown in FIG. FIG. 3 is a diagram showing a print example printed on the surface of the ridge portion. FIG. 4 is a schematic diagram showing a tearing state of the optical fiber cable of the present embodiment. FIG. 5 is an enlarged cross-sectional view of a main part of a semicircular protrusion in a comparative example of the present invention. FIGS. 6A and 6B show an example of tearing an optical fiber cable having a semicircular ridge, which is a comparative example of the present invention, FIG. 6A is a cross-sectional view thereof, and FIG. 6B shows a state in which the tearing position is shifted. FIG. FIG. 7 is a diagram showing an impact test for dropping a weight on the optical fiber cable of this embodiment. FIG. 8 is a cross-sectional view of an optical fiber cable showing another embodiment of the present embodiment.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 1 shows an example of a slotless self-supporting type optical fiber cable to which the present invention is applied. The optical fiber cable 1 has a hollow structure in which a plurality of optical fiber core wires 4 are accommodated in a fiber accommodation portion 3 provided in the sheath 2 without having a slot core.

  Specifically, as shown in FIG. 1, the optical fiber cable 1 includes a cable portion 5, a support wire portion 6, and a neck portion 7 for connecting them. The cable portion 5 is formed by housing a plurality of optical fiber core wires 4 in a fiber housing portion 3 and covering the periphery thereof with a sheath 2.

  In the cable portion 5, two strength members 8 and two tear strings 9 are embedded in the sheath 2 and provided in the longitudinal direction of the cable. Two tensile bodies 8 and two tear strings 9 are arranged opposite to each other at a position rotated 90 degrees around the center of the cable. A support wire 10 is provided on the support wire portion 6 in the cable longitudinal direction and is covered with the sheath 2 so as to cover the periphery thereof. For example, one support line 10 is arranged at the center and a plurality of support lines 10 are arranged so as to form a circle around the support line 10. The neck portion 7 connects the cable portion 5 and the support wire portion 6, and is formed by the same sheath (outer sheath) 2 that constitutes the cable portion 5 and the support wire portion 6.

  Examples of the optical fiber core 4 include a quartz glass fiber provided in the center and a colored optical fiber formed by coating an ultraviolet curable resin and a colored layer around the quartz glass fiber. In addition to this, an optical fiber ribbon in which a plurality of colored optical fiber strands or a plurality of colored optical fiber strands are arranged and collectively covered with an ultraviolet curable resin, or an optical fiber tape in which adjacent optical fiber strands are intermittently fixed An optical fiber core 4 such as a core is stored in the fiber storage 3.

  The tensile body 8 is on a straight line Y connecting the center of the cable part 5 (cable center axis) and the center of the support line part 6 (support line center axis), and one on each side of the fiber storage part 3. It is provided one by one. The tear string 9 passes through the center of the cable portion 5 (cable center axis) and is provided on each side of the fiber storage portion 3 on a straight line X orthogonal to the straight line Y. Further, the tear string 9 is disposed so that a part of the tear string 9 is exposed to or close to the fiber housing 3.

  The portion corresponding to the tear string 9 on the straight line X connecting the tear string 9 and the center of the cable part 5 (cable center axis) has a mark function indicating the position of the tear string and an increase in transmission loss due to insufficient sheath thickness at the impact test. The ridge part 11 which has the function to prevent is provided. As shown in FIG. 2, the protrusion 11 has a tear surface 12 having a flat surface and a tearing position shift that prevents a positional shift when the tear string 9 is torn on both side edges 12 a and 12 b of the tear surface 12. A prevention unit 13 is provided. The tearing position shift prevention portion 13 is an inclined portion surrounded by an inclined surface 14 that inclines from both side edges 12a and 12b of the tearing surface 12 so as to spread from the bottom (shaded portion in FIG. 2). As shown in FIG. 3, a print M indicating the cable length is marked on the tear surface 12 by a hot stamping method. In FIG. 3, the printing M is 01125m.

  The protrusion 11 has a trapezoidal shape with the tear surface 12 as an upper base, and when the length of the upper base is L1 and the length of the lower base is L2, L1 + 0.5 <L2 <L1 + 1.5 , Referred to as a relational expression). The length L2 of the lower base is a distance between the intersections 14a and 14b between the inclined surface 14 and the circular sheath 2.

  The reason why the relation between the upper base and the lower base is desirable will be described. The distance on the straight line X perpendicular to the tear surface 12 from the tear string 9 is S1, the distance from the tear string 9 to both side edges 12a, 12b of the tear surface 12 is S2, and the distance from the tear string 9 to the intersections 14a, 14b. Let the distance be S3. In addition, an angle formed by a line perpendicularly dropped from the tear string 9 to the tear plane 12 and a line connecting the tear string 9 and both side edges 12a and 12b of the tear plane 12 is defined as θ. Under these conditions, the relationship between S2 and S1 is S2 = S1 / cos θ. The angle θ is 0 <θ <90 °. For this reason, S2 and S1 have a relationship of S2> S1.

  Under these conditions, the sheath (outer jacket) 2 on the tear string 9 is removed by shaving or the like to expose the tear string 9, and the sheath 2 of the cable portion 5 is torn by grasping the tear string 9 with pliers or the like. The torn string 9 is difficult to move in the direction of the inclined surface 14. If S3 is the same length as S2, the movement of the tear string 9 can be suppressed. However, since the distinguishability of the ridge 11 decreases, the length of S3 is smaller than L1 + 1.5 mm. 11 is improved. Further, when L2≈L1, the tear string 9 moves beyond the tear surface 12 to the inclined surface 14. Therefore, it is possible to prevent the tear string 9 from moving when L2 is larger than L1 + 0.5 mm. From the above, it is desirable that L2 has a relationship of L1 + 0.5 <L2 <L1 + 1.5.

  As shown in FIG. 4, when the optical fiber cable 1 of this embodiment is grasped with the hand 15 and the tear string 9 is pulled out to tear the jacket, the tear string 9 does not protrude from the tear surface 12 and linearly extends in the longitudinal direction of the cable. Can be pulled.

  On the other hand, as shown in FIG. 5, in the optical fiber cable having the ridge portion 11 that is in the relationship of S1> S2> S3, it is the apex position of the ridge portion 11 when the tear string 9 starts to be drawn. Gradually, the distances S2 and S3 from the tear string 9 to the ridge 11 move in the direction of shortening. Therefore, as shown in FIG. 6, when the tear string 9 comes out from the boundary 16 between the protrusion 11 and the cable portion 5 during the tearing, the cable is twisted in the direction indicated by the arrow A, and the optical fiber cable 1 is moved by the hand 15. A burden is applied to the supporting wrist 15A, and workability is deteriorated. Moreover, since the surface of the protrusion 11 is semicircular, the printing on the surface is easy to be lost and the discrimination is poor.

  Further, as shown in FIG. 7, the optical fiber cable 1 is required to prevent an increase in transmission loss when an impact test in which the weight 17 is dropped on the cable portion 5 is performed. In order to prevent an increase in transmission loss due to this impact test, the thickness T of the sheath (outer jacket) 2 of the cable portion 5 may be increased. However, if the thickness is too large, the tearing force of the outer jacket due to the tear string 9 increases. Decreases. In the present embodiment, the thickness T of the jacket on the tear string 9 is set to about 2.3 mm in consideration of tearability.

Below, the discriminability of the ridge 11, the tearing workability of the tear string 9 and the print discriminability when the length L1 of the upper base and the length L2 of the lower base of the trapezoidal ridge 11 are changed. I investigated. The height of the print M was 1.5 mm in all the samples A to D. As described with reference to FIG. 6, the optical fiber cable 1 was grasped with the hand 15, the ridge 11 was shaved with a cutter or the like, the tear string 9 was taken out, and the tear string 9 was pulled to tear the jacket. These results are shown in Table 1.

  As can be seen from the results shown in Table 1, in the case of Samples B and C, the results showed that all of the convex portion distinguishability, tearing workability, and print distinguishability were good (◯ marks). As can be seen from this result, it is preferable that the trapezoidal protrusion 11 satisfies L1 + 0.5 <L2 <L1 + 1.5. For example, when expressed by numerical values, the protrusion 11 preferably has an upper base length L1 of 2.0 to 3.5 mm and a lower base length L2 of 3.0 to 4.5 mm.

  As described above, according to the present embodiment, the misalignment prevention portion 13 that prevents the misalignment when the tear string 9 is torn is provided on the protruding portion 11 on the tear string 9, so this misalignment prevention is provided. The shift of the tearing position is prevented by the portion 13, and the tear string 9 can be torn linearly. As a result, since the cable is not twisted, workability can be facilitated without placing a burden on the wrist 15A that grips the cable. Further, since the surface of the ridge 11 is a flat tear surface 12, printing by the hot stamp on the tear surface 12 is clear and the discrimination is high.

  Further, according to the present embodiment, when the shape of the ridge portion 11 is a trapezoidal shape with the tear surface 12 as an upper base, the length of the upper base is L1, and the length of the lower base is L2, L1 + 0. Since 5 <L2 <L1 + 1.5, it is possible to tear the jacket linearly without twisting the cable, and to improve the distinguishability of the ridge 11 and the print distinguishability.

  Although specific embodiments to which the present invention is applied have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made. For example, in the above-described embodiment, the print M is formed on the tear surface 12 by the hot stamp method. However, when printing is performed by an ink jet printer, even if there is some unevenness on the print surface, it is difficult to be affected by discrimination. In order to further reduce the tearing force by the tear string 9, a V-shaped groove 18 may be formed on the tearing surface 12 as shown in FIG.

  INDUSTRIAL APPLICATION This invention can be utilized for the optical fiber cable of a structure which pulls a tear string and tears a jacket.

DESCRIPTION OF SYMBOLS 1 ... Optical fiber cable 2 ... Sheath (jacket)
DESCRIPTION OF SYMBOLS 3 ... Fiber accommodating part 4 ... Optical fiber core wire 5 ... Cable part 6 ... Support line part 7 ... Neck part 8 ... Tensile body 9 ... Tear string 10 ... Support line 11 ... Projection part 12 ... Tear surface 13 ... Position shift prevention part 18 ... V-shaped groove

Claims (3)

In a hollow structure optical fiber cable in which a plurality of optical fiber cores are stored in a fiber storage section provided in a sheath,
In the sheath,
A tensile body embedded in the longitudinal direction of the cable;
A tear string embedded in the longitudinal direction of the cable in the vicinity of the fiber storage portion;
Prevents misalignment when the sheath is torn by pulling the tear string on the tear surface having a flat surface and both side edges of the tear surface at the portion corresponding to the tear string on the line connecting the tear string and the cable central axis. An optical fiber cable, comprising: a protrusion having a tearing position shift prevention portion. The optical fiber cable according to claim 1,
The ridge portion has a trapezoidal shape with the tear surface as an upper base, and when the length of the upper base is L1 and the length of the lower base is L2, L1 + 0.5 <L2 <L1 + 1.5. An optical fiber cable characterized by that. The optical fiber cable according to claim 1 or 2,
An optical fiber cable comprising a V-shaped groove on the tear surface.

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