JP2007249020A - Method of manufacturing optical cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical cable, in which the positional deviation of a tear cord by the twist of an optical fiber unit can be eliminated and in which tearing of a sheath covering can be ensured, by maintaining adhesion between the tear cord and the sheath covering at a prescribed value or higher. <P>SOLUTION: The optical fiber unit 3 is accompanied by the tear cord 5 and lump covered with the sheath covering 6. In the nipple 13 for extrusion molding of a coating material 6', there is arranged a tip end of the guide tube 14c for the tear cord, to the rear by 4.0-11.0 mm from the tip end of the guide tube 14a for the optical fiber unit. If Ra is the curtailment rate on the outside of the coating (outside diameter D2, after cable coating/inner diameter D1 of a die), and Rb is the curtailment ratio on the inside of the coating (outside diameter d2 of the optical fiber unit/outside diameter d1 of the guide tube for the optical fiber unit), the cable sheath covering 6 is extrusion molded in a manner where the curtailment ratio (Ra/Rb) becomes 0.9-1.00. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical cable manufacturing method in which a tension member and a tear string are embedded in a sheath together with an optical fiber unit.

  As a general optical cable, a tension member is disposed on both sides of a bundle in which a plurality of optical fiber cores are bundled or an optical fiber unit (also referred to as an optical cable core) containing a plurality of tape-shaped optical fiber cores. There is known a structure in which a unit is provided with a sheath covering along a tear string along a unit. FIG. 1 is a diagram schematically illustrating the above-described optical cable. FIG. 1A is a self-supporting configuration example having a support line when the optical cable is stretched over the air, and FIG. 1B is a configuration having no support line. It is the figure which showed the example.

  A self-supporting type optical cable 1 in FIG. 1A has a configuration in which a cable main body 2 and a support wire portion 8 are integrally connected by a neck portion 9, and an optical cable 1 ′ in FIG. It is comprised only by the cable main-body part 2 of FIG. 1 (A) of circular cross section which does not have the neck part 9. FIG. The cable body 2 is provided with an optical fiber unit 3 in the center, and tension members (also referred to as strength members) 4 for giving tensile strength to the optical cable on both sides of the optical fiber unit 3 in parallel. The tear string 5 for tearing the sheath covering is arranged so as to be in contact with each other, and these are collectively covered.

  The two tension members 4 are arranged on a straight line passing through the center of the optical fiber unit 3 and are embedded in the sheath coating 6 so as to enhance the unity. The tear string 5 is disposed at a position that does not overlap with the tension member 4, for example, on a line orthogonal to a straight line passing through the two tension members 4. Further, the tear string 5 needs to be along the surface of the optical fiber unit 3 for the purpose of peeling off the sheath coating 6 from the optical fiber unit 3. And the protrusion 7 which shows the embedding position of the tear string 5 is provided in the outer surface of the sheath coating | cover 6, so that the tear string 5 can be taken out easily.

However, when the sheath coating 6 is formed, the tear string 5 is twisted before reaching the die exit, and the relative position is not stable, so that it may be separated from the surface of the optical fiber unit 3, or the ridge 7 May be displaced from the position. Therefore, for example, as disclosed in Patent Document 1, in an extrusion molding apparatus using a nipple, a guide tube that guides a tear string is connected to a guide tube of an optical fiber unit (cable core) before the nipple outlet, It is known to collectively coat an optical fiber unit in a state where a tear string is placed.
JP 2002-192591 A

  As disclosed in the above-mentioned Patent Document 1, the tearing string guide tube is joined from the middle of the nipple to the guide tube of the optical fiber unit so that the tearing string is in contact with the optical fiber unit and collectively covered. Is possible. However, when the optical fiber unit is twisted and moved in the nipple, the tear string also rotates along the optical fiber unit and may deviate from the ridge indicating the embedded position. Moreover, since it coat | covers in the state integrated with the optical fiber unit, a tear string is buried in the optical fiber unit side, and the adhesiveness of a tear string and a sheath coating | cover falls. For this reason, there has been a problem that when the sheath covering is torn, the tear string is easily pulled out, and the tearing cannot be performed.

  The present invention has been made in view of the above-described circumstances, and can eliminate the positional deviation of the tear string due to the twist of the optical fiber unit, and can maintain the adhesion force between the tear string and the sheath covering at a predetermined value or more, thereby improving the sheath covering. An object of the present invention is to provide a method of manufacturing an optical cable capable of reliably cutting the cable.

  In the optical cable manufacturing method according to the present invention, two tension members are arranged in parallel so as to be linearly arranged on both sides of the optical fiber unit, and the optical fiber unit is collectively covered with a tear string. The nipple portion for extrusion molding of the coating material is provided with a guide tube through which the optical fiber unit, the tension member and the tear string are passed, and the tip of the guide tube for the optical fiber unit is disposed at the exit position of the die for tearing. The tip of the string guide tube is disposed 4.0 mm to 11.0 mm after the tip of the optical fiber unit guide tube. Then, (outer diameter D2 / cable inner diameter D1 / die inner diameter D1) is defined as a reduction ratio Ra on the outside of the coating, and (optical fiber unit outer diameter d2 / guide fiber outer diameter d1 for the optical fiber unit) is defined as a reduction ratio Rb on the inner side of the coating. When this is done, the cable covering is extruded so that the reduction ratio (Ra / Rb) is 0.9 to 1.00.

  According to the present invention, since the optical fiber unit and the tear string are guided independently from each other, it is possible to eliminate the displacement of the tear string due to the twist of the optical fiber unit. In addition, by controlling the relationship between the distance between the tip of the guide tube for the optical fiber unit and the tear string and the reduction ratio of the sheath coating at the die outlet, the adhesion between the tear string and the sheath is optimized. Pull-out can be prevented.

  Embodiments of the present invention will be described with reference to the drawings. 1 is a diagram for explaining the outline of an optical cable, FIG. 2 is a diagram for explaining the outline of an extrusion molding apparatus used in the present invention, FIG. 3 is a diagram showing a partial cross section of FIG. 2, and FIG. FIG. 5 is a view for explaining a molded state, and FIG. 5 is a view for explaining a reduced state of the sheath covering according to the present invention. In the figure, 1 and 1 'are optical cables, 2 is a cable body, 3 is an optical fiber unit, 4 is a tension member, 5 is a tear string, 6 is a sheath coating, 6' is a coating material, 7 is a ridge, 8 is Support wire part, 9 is a neck part, 10 is a support line, 11 is an extrusion molding device, 12 is a die part, 12a is an outlet hole, 12b is an inner chamber part, 13 is a nipple part, 14a, 14b, 14c and 14d are guide tubes Indicates.

  As shown in FIG. 1A, the self-supporting optical cable 1 manufactured by the manufacturing method of the present invention has a configuration in which the cable body 2 and the support wire 8 are integrally connected by a neck 9. Further, the optical cable 1 ′ of FIG. 1B is configured by only the cable main body 2 having a circular cross section without the support wire portion 8 and the neck portion 9. The cable main body 2 has an optical fiber unit 3 in the center, tension members 4 for giving tensile strength to the optical cable in parallel on both sides thereof, and a sheath coating 6 so as to be in contact with the optical fiber unit 3. A tear string 5 for tearing is formed, and these are collectively covered with a sheath coating 6.

  The optical fiber unit 3 has, for example, a structure in which a plurality of bundles of a plurality of optical fiber cores are twisted, or a buffer material such as polypropylene yarn is wound around an outer side where a plurality of optical fiber tape cores are laminated. Things are used. The tension member 4 is made of a high tensile strength wire such as a steel wire, and is arranged in parallel at a predetermined interval on both sides of the optical fiber unit 3 on a straight line passing through the center of the optical fiber unit 3 and embedded in the sheath coating 6. It arrange | positions so that it may closely_contact | adhere.

The tear string 5 is disposed at a position that does not overlap with the tension member 4, for example, on a line orthogonal to a straight line passing through the two tension members 4. Further, for the purpose of peeling off the sheath coating 6 from the optical fiber unit 3, the sheath coating 6 is embedded so as to be in contact with the surface of the optical fiber unit 3 and not pulled out from the sheath coating 6. And the protrusion 7 which shows the embedding position of the tear string 5 is provided in the outer surface of the sheath coating | cover 6, so that the tear string 5 can be taken out easily.
The support wire 10 of the support wire portion 8 is made of a steel stranded wire or the like having sufficient strength to suspend an optical cable, and is arranged on a straight line extending through the centers of the optical fiber unit 3 and the tension member 4. The

  The optical cable described above is sheathed 6 by an extrusion molding apparatus 11 as shown in FIG. The extrusion molding apparatus 11 includes a die portion 12 and a nipple portion 13, and the nipple portion 13 includes a plurality of guide tubes 14 a to 14 d. FIG. 3A shows a cross section taken along the line AA in FIG. 2, and the outlet hole 12a of the die portion 12 has a shape substantially equal to the outer shape of the optical cable. 3B shows a cross section taken along the line B-B of FIG. 2, and is an inner chamber portion 12 b of the die portion 12 between the outlet hole 12 a of the die portion 12 and the tip portion of the nipple portion 13. Formed in the chamber. Then, the guide tubes 14 a to 14 d of the nipple portion 13 are arranged so that the optical fiber unit 3, the tension member 4, the tear string 5 and the support line 10 are in a predetermined arrangement state as shown in FIG. It is provided so as to protrude from the tip side.

  As shown in FIG. 2, the coating material is extruded into a gap portion formed between the inner chamber portion 12 b of the die portion 12 of the extrusion molding apparatus 11 and the nipple portion 13. This coating material is extruded from the inner chamber portion 12b to the outlet hole 12a, introduced from the rear of the nipple portion 13, and drawn from the tips of the guide tubes 14a to 14d, the optical fiber unit 3, the tension member 4, the tear string 5, and the support line. Cover around 10 at once.

  The guide tube 14 a guides the optical fiber unit 3, and the distal end of the guide tube 14 a is disposed so as to substantially coincide with the distal end position of the outlet hole 12 a of the die portion 12. The guide tube 14 b guides the tension member 4, and the tip of the guide tube 14 b is disposed so as to be located inside the outlet hole 12 a of the die portion 12. The guide tube 14 c guides the tear string 5, and the tip of the guide tube 14 c is disposed inward of the guide tube 14 a of the optical fiber unit 3 by a predetermined distance in the vicinity of the outlet hole 12 a of the die portion 12. . The guide tube 14 d is formed on the support wire 10, and the tip of the guide tube 14 d is disposed so as to be located inside the outlet hole 12 a of the die portion 12, similarly to the guide tube 14 b of the tension member 4.

  The guide tube 14b of the tension member 4 and the guide tube 14d of the support wire 10 are formed with short tips (behind the outlet hole 12a of the die portion), but are completely embedded in the sheath covering so as to be tightly integrated. In order to increase the thickness, the coating material is sufficiently filled (attached) in the periphery of the die portion 12. The guide tube 14c of the tear string 5 is desirably embedded in a state in which the entire outer periphery of the tear string 5 is not completely embedded in the sheath, and a part thereof is in contact with the outer surface of the optical fiber unit 3. However, if the adhesion with the sheath is weak, pull-out occurs when the sheath is cut, so that it is necessary to have a certain degree of adhesion integrity. For this reason, the guide tube 14c of the tear string 5 is positioned behind the guide tube 14a of the optical fiber unit 3 by a predetermined distance as will be described later.

  Formation of the sheath coating by the above-described extrusion molding apparatus is carried out in the form of FIG. 4 shown in the CC section of FIG. The coating material 6 ′ extruded into the inner chamber portion 12 b between the die portion 12 and the nipple portion 13 is extruded into a tube shape from the outlet hole 12 a in a molten state with a predetermined viscosity. The coating material 6 ′ extruded into a tube shape reduces the tube diameter to the surface of the optical fiber unit 3 drawn from the guide tube 14a in which the outlet end 12a of the die portion 12 and the outlet end are substantially at the same position. Reduced and applied to form a sheath coating 6.

  The tear string 5 is also pulled out from the guide tube 14c at the same time as the optical fiber unit 3, but the difference (distance) L in length between the distal end of the guide tube 14a of the optical fiber unit 3 and the distal end of the guide tube 14c of the tear string 5 is large. Then, the pressurized coating material 6 ′ also flows between the guide tube 14 a of the optical fiber unit 3 and the tear string 5, and the tear string 5 is buried in the sheath coating 6. When the distance L is small, the tear string 5 contacts the optical fiber unit 3 and is extruded into a tube shape before the coating material 6 ′ sufficiently flows between the guide tube 14a of the optical fiber unit 3 and the tear string 5. The coating material 6 'is reduced so as to be integrally coated along the surface of the optical fiber unit 3. However, the adhesion between the tear string 5 and the sheath coating 6 is somewhat lowered, and the pull-out force of the tear string 5 is reduced.

  Here, the inner diameter of the outlet hole 12a of the die portion 12 for molding the cable main body portion 2 of the optical cable is D1, and the outer diameter of the sheath coating (not including the protrusion 7) 6 of the cable main body portion 2 is D2. The reduction ratio Ra on the outside of the sheath coating 6 is (D2 / D1). Also, the outer diameter of the guide tube 14a of the optical fiber unit 3 is d1, the inner diameter of the sheath coating 6 of the cable body 2 is d2, and the reduction ratio Rb inside the sheath coating 6 at this time is (d2 / d1). . Then, the molding conditions are set so that the ratio (Ra / Rb) of the reduction ratio between the outside and the inside of the sheath coating 6 is within a predetermined range as will be described later.

  FIG. 5 is a diagram for explaining the action state of the sheath coating 6 based on the above reduction ratio ratio (Ra / Rb). FIG. 5A shows a case where the outer reduction ratio Ra is larger than the inner reduction ratio Rb. The inner side of the sheath coating 6 tries to eliminate the difference between the reduction rate and the outer rate, and the optical fiber unit 3 is tightened. For this reason, the pulling force of the tear string 5 is increased, but it is embedded in the sheath coating 6. FIG. 5B shows a case where the outer reduction ratio Ra is smaller than the inner reduction ratio Rb, and the inside of the sheath coating 6 is separated from the optical fiber unit 3 and expands outward in order to eliminate the difference in the reduction ratio. I will try again. For this reason, a cavity is formed around the tear string 5 and the pulling force is reduced.

  FIG. 6 and FIG. 7 are diagrams showing evaluation results of manufacturing the above-described optical cable test product and testing the state in which the tear string is embedded in the sheath coating. As the test optical cable, the self-supporting optical cable structure shown in FIG. 1A is used, and the optical fiber unit 3 is twisted with three bundles of eight optical fiber core wires, and polypropylene. A yarn wound to an outer diameter of 5.1 mm was used. The support wire 10 was a steel stranded wire in which seven steel wires having an outer diameter of 1.4 mm were twisted, and the tension member 4 was a steel wire having an outer diameter of 0.72 mm. As the tear string 5, a polyethylene terephthalate (PET) string having an outer diameter of 0.9 mm was used. And as a material of the sheath coating 6, linear low density polyethylene (L-LDPE) is used, the outer diameter of the cable body 2 is 10.5 mm, and the cable height including the support wire 8 is 18.0 mm. Extrusion molding was performed.

  The optical cable of the test product has a length difference (distance) L between the tip of the guide tube 14a of the optical fiber unit 3 and the tip of the guide tube 14c of the tear string 5 of 0.0 mm (the guide tube 14a and the guide tube 14c The tip position was the same), and multiple types were prepared by setting 5.0 mm, 10.0 mm, and 15.00 mm. Further, the length difference L is made different, and the molding condition is set such that the reduction ratio (Ra / Rb) of the sheath coating 6 is 0.80, 0.90, 1.00, and 1.10. (For example, the viscosity of the coating material, the forming linear velocity, etc.) were set to produce a plurality of types.

  As a result, when the length difference L between the tear pipe guide tube 14c and the optical fiber unit guide pipe 14a is 0.0 mm, the coating material 6 'enters between the tear string 5 and the optical fiber unit 3. There is no allowance, and the tear string 5 is covered with the optical fiber unit 3 without being buried in the sheath cover 6. However, when the reduction ratio (Ra / Rb) was 0.80 to 1.10, the pulling force of the tear string 5 was small (12.0 N / 10 m or less), and the determination results were all poor. In addition, since the pulling-out force of the tear string 5 is not 30 N / 10 m or more, it will come off when the sheath coating 6 is torn, and therefore, if the pulling-off force is less than 30 N / 10 m, it is regarded as defective.

  When the length difference L is 5.0 mm, when the reduction ratio (Ra / Rb) is 0.80 to 1.00, the tear string 5 is not embedded in the sheath coating 6 and the optical fiber unit 3 It was coated in a state in contact with However, if the reduction ratio (Ra / Rb) is 1.10, the inner side of the sheath coating 6 swells away from the optical fiber unit 3 and is covered between the tear string 5 and the optical fiber unit 3. Since the material 6 'wraps around, the tear string 5 is buried in the sheath coating 6 and becomes defective. The pulling force of the tear string 5 was insufficient at 16 N / 10 m when the reduction ratio (Ra / Rb) was 0.80, and 30 N / 10 m or more was secured at 0.90 to 1.10. As a result, when the length difference L was set to 5.0 mm, the reduction ratio (Ra / Rb) was preferably 0.90 to 1.00.

  Even when the length difference L is 10.0 mm, when the reduction ratio (Ra / Rb) is 0.80 to 1.00, the tear string 5 is not embedded in the sheath coating 6 and the optical fiber unit 3 It was coated in a state in contact with However, if the reduction ratio (Ra / Rb) is 1.10, the inner side of the sheath coating 6 swells away from the optical fiber unit 3 and is covered between the tear string 5 and the optical fiber unit 3. Since the material 6 'wraps around, the tear string 5 is buried in the sheath coating 6 and becomes defective. The pulling force of the tear string 5 was insufficient at 22 N / 10 m when the reduction ratio (Ra / Rb) was 0.80, and 40 N / 10 m or more was secured at 0.90 to 1.10. As a result, when the length difference L was 10.0 mm, the reduction ratio (Ra / Rb) was preferably 0.90 to 1.00.

  When the length difference L is 15.0 mm, the tear string 5 is buried in the sheath sheath 6 in any case where the reduction ratio (Ra / Rb) is 0.80 to 1.10. It became bad. Since the length difference L is large, the pressurized coating material 6 ′ also flows between the guide tube 14 a of the optical fiber unit 3 and the tear string 5, and the tear string 5 is embedded in the sheath coating 6. Because it will be. The pulling force of the tear string 5 can be ensured to be 30 N / 10 m or more in any case, but since the tear string 5 is buried in the sheath coating 6, it is not possible to perform good tearing, so it is generally poor. It became.

  From the above evaluation results, as shown in FIGS. 7A and 7B, the difference in length L between the guide tube of the optical fiber unit 3 and the guide tube of the tear string 5 within the range surrounded by the dotted line ( It is necessary to extrude the cable covering with the distance between the tips of both guide tubes and the reduction ratio (Ra / Rb). That is, the length difference L with respect to the guide tube is preferably in the range of 5.0 mm to 10.0 mm, and is within a range of 4.0 mm to 11.0 mm with some margin. Further, (outer diameter D2 / cable inner diameter D2 / die inner diameter D1) is a reduction ratio Ra on the outer side of the coating, and (optical fiber unit outer diameter d2 / guide fiber outer diameter d1 for the optical fiber unit) is a reduction ratio Rb on the inner side of the coating. In this case, it is necessary to set the molding conditions so that the reduction ratio ratio (Ra / Rb) is 0.9 to 1.0.

It is a figure explaining the outline of the optical cable made into object by this invention. It is a figure explaining the outline of the extrusion molding apparatus used by this invention. It is a figure which shows the partial cross section of FIG. It is a figure explaining the shaping | molding state of the sheath coating | cover by this invention. It is a figure explaining the reduced state of the sheath coating by this invention. It is a figure explaining the evaluation result of the present invention. FIG. 7 is a graph showing the evaluation results of FIG. 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1 '... Optical cable, 2 ... Cable main-body part, 3 ... Optical fiber unit, 4 ... Tension member, 5 ... Tear string, 6 ... Sheath coating, 6' ... Coating material, 7 ... Projection, 8 ... Support line part , 9 ... neck part, 10 ... support wire, 11 ... extrusion molding device, 12 ... die part, 12a ... outlet hole, 12b ... inner chamber part, 13 ... nipple part, 14a, 14b, 14c, 14d ... guide tube.

Claims (2)

A method of manufacturing an optical cable in which two tension members are arranged in parallel so as to be arranged in a straight line on both sides of an optical fiber unit, and the optical fiber unit is covered in a lump along a tear string,
The nipple portion for extrusion molding of the coating material includes a guide tube through which the optical fiber unit, the tension member, and the tear string are passed,
The distal end of the guide tube for the optical fiber unit is disposed at the exit position of the die, and the distal end of the guide tube for the tear string is 4.0 mm to 11.0 mm inward from the distal end of the guide tube for the optical fiber unit. Place and
When (outer sheath outer diameter D2 / die inner diameter D1) is the outer reduction ratio Ra and (optical fiber unit outer diameter d2 / guide fiber outer diameter d1 for the optical fiber unit) is the inner reduction ratio Rb. A method of manufacturing an optical cable, comprising extruding a sheath coating so that a reduction ratio ratio (Ra / Rb) is 0.9 to 1.00.   2. The method of manufacturing an optical cable according to claim 1, wherein a support line is disposed on an extension of a straight line passing through the centers of the two tension members and is collectively covered.

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