JPH11190813A - Spacer for optical fiber cable and spacer manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the groove slope in a spacer cross section regardless of the cross-sectional structure of the spacer and the inversion pitch and to reduce the fluctuation of the groove volume in the longitudinal direction by making the inclination index to be more than a prescribed value and suppressing the groove tilt angle in the spacer cross section to be less than a specific value. SOLUTION: Plural recessed shape optical fiber housing grooves 20 are provided on the outer peripheral edge of a main body coating layer 16 of the spacer at intervals in the peripheral direction. The grooves 20 are separated by ribs 22, provided along the longitudinal direction of the layer 16 and formed in a so-called SZ helical shape in which a prescribed strand pitch and a lead angle are provided and the helical direction is reversed for every prescribed pitch. Let a rib inclination index (F) = one rib cross-sectional area (S) ×a rib center of gravity distance (XG) × a helical advance angle (α)/a minimum rib thickness (T), the index F is set to be more than a prescribed value and the groove inclination angle in the spacer cross section is made less than 10 deg.. Thereby, the fluctuation of the effective cross section of the grooves is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spacer for an optical fiber cable, which has a small groove inclination at a reversal portion of a spiral groove which is alternately reversed, and consequently a fluctuation of a groove volume in a longitudinal direction is small, and a manufacturing method thereof.

[0002]

2. Description of the Related Art As a spacer for an optical fiber cable having a helical groove, a spacer having a helical groove continuous in one direction along a longitudinal direction is provided. In some cases, the spiral direction of the groove is periodically reversed in order to facilitate the operation of branching and connecting the optical fiber.

In the manufacture of the optical fiber cable spacer having the alternately inverted spiral grooves, the spiral grooves are subjected to a contraction force during cooling and solidification of a synthetic resin forming the spacer body and an inertial force due to a change in the rotation direction. In particular, in the spacer cross section at the portion where the direction of the spiral groove is reversed, the groove is inclined,
As a result, there is a problem that the fluctuation of the groove volume in the longitudinal direction becomes large.

[0004] In particular, recently, in order to secure an extra length of an optical fiber for the purpose of improving workability at the time of laying a cable, a short pitch of an inversion pitch and a groove volume ratio for the purpose of increasing the density of a cable have been increased. With the increase, the rib base thickness is reduced in thickness and the depth of the groove is promoted, the groove inclination becomes remarkable, and as a result, the longitudinal fluctuation of the groove volume tends to be larger. It is known that the change in the inclination and the volume of the groove causes the existing position of the optical fiber housed in the groove to be shifted from the design position, thereby increasing the transmission loss of the optical fiber.

That is, in the design of the conventional optical fiber cable spacer, it is necessary to consider the existence of the groove inclination at the design stage. Therefore, the diameter of the spacer body, the length of the inversion pitch, and the groove shape are increased. Thus, the spacer structure has to be compromised, for example, and it has been very difficult to obtain an ideal spacer.

As means for solving these problems, Japanese Utility Model Application Laid-Open Publication No. Sho 16-16522 proposes an apparatus for co-extruding a resin material for forming a groove and a resin material for forming a main body forming a rib. . However, the manufacturing apparatus disclosed in this publication has the technical problems described below.

[0007] In an apparatus (coextrusion method), a molten groove retaining resin material is filled from the outer peripheral side into a linear recess provided on the outer periphery thereof in a state in which the resin material for forming the spacer main body is not yet solidified. It was found that deformation occurred in a linear concave shape and spread from the groove bottom toward the surface side, and it was found that the expected effect was not exhibited.

An apparatus (wire material supply method) for supplying a resin material for forming a spacer main body in a molten state while supplying a wire material having a predetermined cross-sectional shape, which has been solidified into a groove shape resin material, has two steps. If the extrusion speed is increased while directly leading to an increase in cost, troubles such as roughening and flaws on the groove surface occur due to imbalance with the supply speed of the wire, which is not practical.

Further, it is difficult to twist a wire made of a hard groove-preserving resin material into SZ.

[0010]

SUMMARY OF THE INVENTION For a spacer in which the direction of the spiral groove is alternately inverted, the cross-sectional structure of the spacer,
The present invention was completed by diligent studies for the purpose of reducing the inclination of the groove in the cross section of the spacer and reducing the fluctuation of the groove volume in the longitudinal direction, regardless of the inversion pitch and the like.

[0011]

According to the present invention, there is provided an optical fiber cable spacer having a continuous spiral groove whose direction is periodically reversed along the longitudinal direction on the outer periphery thereof. Inclination index (F) of rib defining a spiral groove = rib cross-sectional area (S) × rib center of gravity distance (X
When G) × helical advancing angle (α) / minimum rib thickness (T), the inclination index was set to a predetermined value or more, and the groove inclination angle in the spacer cross section was suppressed to 10 ° or less. In the spacer configured as described above, particularly, the groove inclination angle at the reversal portion of the alternate reversal spiral groove is as small as 10 ° or less, so that the variation of the effective cross-sectional area of the groove is reduced. Further, in the optical fiber cable spacer having a rib inclination index of 100 or more, the groove inclination angle in the cross section of the spacer is suppressed to 10 ° or less, and the optical fiber cable spacer has a small variation in the groove volume in the longitudinal direction. This configuration is effective for a spacer having a large rib inclination index, that is, a groove in which a groove is easily inclined. Further, in the manufacturing method of the present invention, when extruding the synthetic resin for molding the spacer main body of the optical fiber cable spacer, a resin having no compatibility with the synthetic resin for forming the main body is formed in a portion to be the spiral groove. After filling, the resin having no compatibility was peeled off. With this configuration, it is more reliable to keep the groove inclination at 10 ° or less, and if this spacer is used, the transmission performance of the optical fiber can be ensured, as will be clear from the embodiments described later.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings, but they do not limit the scope of the present invention.

FIG. 1 shows an embodiment of an optical fiber cable spacer according to the present invention.

The optical fiber cable spacer 10 shown in FIG. 1 is a cross-sectional view thereof. The optical fiber cable spacer 10 has a tensile member 12 disposed at the center and a thermoplastic resin on the outer periphery of the tensile member 12. And a main body coating layer 16 formed on the outer periphery of the preliminary coating layer 14.
In the spacer 10 of the present invention, the preliminary coating layer 14
Naturally, it may be formed by extrusion coating a plurality of times.

On the outer peripheral edge of the main body coating layer 16 of the spacer,
A plurality of concave optical fiber storage grooves 20 are provided at intervals in the circumferential direction.

The optical fiber accommodating groove 20 is defined by a rib 22 and extends along the longitudinal direction of the spacer main body coating layer 16, and the helical direction is formed at a predetermined twist pitch and lead angle at a predetermined pitch. It is formed in an inverted SZ spiral shape.

In the spacer 10 of the present invention, attention was paid to the rib inclination index. First, the rib inclination index is defined by the following equation. Rib inclination index (F) = one rib cross-sectional area (S) × rib center of gravity distance (XG) × spiral advancing angle (α) / minimum rib thickness (T) From this definition, the rib inclination index F is It is understood that the cross-sectional area of each piece, the center of gravity distance of the rib, and the spiral advance angle are directly proportional to the minimum rib thickness.

That is, when the depth of the groove is large, the rib is also large, so that the center of gravity distance XG of the rib is large, or the cross-sectional area of the rib is large, the root of the rib is small, and the spiral advancing angle (α) is large. That is, it has been found that when the reversal pitch is small, the rib inclination in the reversal portion is large.

In particular, when the rib inclination index is 100 or less, the inclination of the rib at the inversion portion is 10 ° or less, but when it exceeds this, the inclination angle of the rib exceeds 10 ° and the volume variation of the cross-sectional area of the rib is large. That is to say, when the optical fiber is housed in the groove and formed into a cable, it leads to an increase in transmission loss.

Therefore, when the rib inclination index F exceeds 100, a resin having no compatibility with the resin for forming the main body is co-extruded into the groove, solidified by cooling, and then the resin in the groove is peeled off to remove the spacer. Just get it.

Generally, the rib inclination index F is large in a spacer having a square groove and small in a spacer having a U groove. That is, in the SZ type spacer of the square groove in which the rib base thickness is necessarily reduced, the inclination of the groove is particularly problematic.

A spacer for an optical fiber cable to which the present invention is applied is provided with a tension wire or a wire material in which the outer periphery of the tension wire is preliminarily coated with a thermoplastic resin to a cross head of a melt extruder and a rotating die. An optical fiber cable spacer obtained by extruding a molten thermoplastic resin while alternately rotating at a predetermined rotation angle to form ribs and a spacer body at the bottom of a groove.

When a tensile strength wire is used, it may be a single steel wire, a stranded steel wire, or a single or stranded fiber reinforced plastic wire composed of various reinforcing fibers.

In consideration of the accuracy of the cross-sectional shape of the spacer, the outer periphery of the tensile strength wire has been proposed by the present applicant,
As in the method of No. 81763, a preliminary coating layer is formed on the outer periphery of the tensile strength line with a thermoplastic resin compatible with the resin for forming the spacer main body, and its outer diameter is fixed to the outer diameter only at the groove bottom of the spacer main body. Or a case where the main body resin for forming the spacer is directly extruded to the outer periphery of the thermoplastic resin linear material without using the tensile strength wire.

The resin for forming the groove is not particularly limited as long as it is not compatible with the resin for the spacer body forming the ribs and can be separated after cooling and solidifying. Close ones are preferred in terms of coextrusion.

As the spacer main body resin, a polyolefin-based crystalline thermoplastic resin, particularly a polyethylene-based resin, is generally used from the viewpoint of physical properties and economy when used as a spacer in a cable. However, the present invention has an object to reduce the inclination of the rib in the process of solidifying the crystalline thermoplastic resin from the molten state, and the thermoplastic resin of the spacer main body is preferably made of the above-mentioned polyolefin resin. It is not limited to resin, but may be a copolymer of these, a blend with another thermoplastic resin, polybutylene terephthalate (PBT), polycarbonate (PC), polyamide resin, or the like.

As the groove-preserving resin material of the present invention, a resin having no compatibility with the spacer main body resin, that is, a resin which is easy to peel off after solidification by cooling is selected. Is used,
A homopolymer of polypropylene, or a copolymer or blend of polypropylene, etc. is used, and if these resins are appropriately added with a release aid such as a fatty acid amide-based, silicone-based, or fluorine-based resin, the exfoliation after the removal is easy. Is preferable.

In order to co-extrude the spacer main body resin and the groove-retaining synthetic resin, Japanese Patent Application No. Hei 9 (1996) -197, filed by the present applicant.
The method and apparatus of 195665 are preferred. In the method of the present applicant, the portion to be a spiral groove is separated by a partition, and after supplying the groove-retaining synthetic resin to the back side of the partition, the portion to be a spiral groove on the downstream side of the partition. It is characterized by being filled into.

Specific Embodiment 1 FIG. In the cross-sectional shape shown in FIG. 5, an adhesive polyethylene (MI006: manufactured by Nippon Unicar: GA006) and a low-density linear polyethylene (LLDPE, Nippon Unicar Co., Ltd .; trade name NUCG5350)
A pre-coated tensile strength wire 14 having an outer diameter of 4.6 mm was obtained.

The surface of the pre-coated tensile wire 14 is 60 ° C.
The resin is introduced into a rotating die while preheating so as to obtain a resin having a melt index (MI) of 0.068 as a resin for forming a spacer body while rotating the die so as to form a spiral in which ribs and grooves are alternately inverted. And extruded polypropylene having an MI of 0.237 as a groove-preserving resin at a resin temperature of 200 ° C. at the die portion, and cooled and solidified to take out.

The specifications of the SZ spacer to be obtained include five grooves having an outer diameter of 9.8 mm, an opening having a groove width of 2.4 mm, a groove bottom width of 2.0 mm, and a groove depth of 2.3 mm. The inversion pitch was 165 mm and the inversion angle was 290 °. In this specification, the spiral advancing angle α is 8.55 ° because it is approximated by tan α = (9.8 × π × 290/360) / 165. The cross-sectional area of one rib is 55.1 mm ² , and the distance to the center of gravity XG
Substituting 1.31 mm and the minimum rib thickness T of 1.26 mm, the rib inclination index F is: F = 55.1 × 1.31 × 8.55 / 1.26 = 48
9.8.

The spacer obtained by peeling off the groove-retaining polypropylene has a spiral angle of 4.7 ° at the spiral portion by normal rotation, and a groove inclination angle of the inverted portion at 8.9 °, The groove inclination angle was smaller than that of the comparative example to be described next, and thus the fluctuation of the groove cross-sectional volume in the longitudinal direction was small.

Comparative Example 1 SZ of the same specification as the first embodiment
In order to obtain a spacer of the type, it was manufactured without filling with a groove-shaping resin as in Example 1. The groove inclination angle of the normal rotating part of the obtained SZ spacer is 14.1 °, and the groove inclination angle of the reversing part is 26.8 °, and the groove volume cross-sectional ratio of the normal rotating part and the reversing part is significantly different. However, there is a problem in using the same as an optical fiber cable as a spacer.

The groove inclination angle is shown in FIG. As shown in FIG. 3, an angle β formed by a line l ₂ connecting the center point A of the groove bottom and a center point B of the opening of the groove with respect to a line l ₁ connecting the center point A of the groove bottom and the rotation center O, The obtained spacer was determined from a cross-sectional enlarged photograph.

Embodiment 2 FIG. The groove has a U-shaped cross-sectional shape as shown in
The apparent diameter of 4.2 strands of 1.4 mm steel wire is 4.2
mm = 1 (mm tensile strength body 12)
0 adhesive polyethylene (manufactured by Nippon Unicar: GA00
6) and a low-density linear polyethylene (LLDPE, manufactured by Nippon Unicar Co., Ltd .; trade name NUCG5350) are coated by coextrusion, and a pre-coated tensile strength wire 14 having an outer diameter of 9.3 mm is coated.
I got

The surface of the pre-coated tensile strength wire 14 is 60 ° C.
The resin is introduced into a rotating die while preheating so as to obtain a resin having a melt index (MI) of 0.068 as a resin for forming a spacer body while rotating the die so as to form a spiral in which ribs and grooves are alternately inverted. And a polypropylene resin having an MI of 0.237 as a groove-preserving resin was extruded at a resin temperature of 200 ° C. at the die portion, and was taken out while being cooled and solidified.

The specifications of the SZ spacer to be obtained are such that the outer diameter is 15.5 mm, and the width of the opening and the groove at the center of the groove is 2.9 m.
m, 8 grooves with a groove depth of 2.8 mm, reversal pitch 23
5 mm, reversal angle 300 °, minimum rib thickness T 1.88
mm.

In this specification, the spiral advancing angle α is 9.8 ° when determined in the same manner as described above. The cross-sectional area of one rib is 45.3 mm ² , and the distance to the center of gravity XG1.05
mm and the minimum rib thickness of 1.88 mm, the rib inclination index F is: F = 45.3 × 1.05 × 9.80 / 1.88 = 24
7.9.

The spacer obtained by stripping the groove-preserving resin has an inclination angle of the groove of the spiral portion by normal rotation.
Comparative Example 2 in which the groove inclination angle of the reversal part was 4 ° and the angle of inclination was 6.5 °. Thus, the groove inclination was small, and the fluctuation of the groove cross-sectional volume in the longitudinal direction was small.

Comparative Example 2 SZ having the same specifications as in the second embodiment.
In order to obtain a U-shaped groove spacer of the type, it was manufactured without filling the groove-shaping resin as in Example 2. The groove inclination angle of the normal rotating part of the obtained SZ spacer is 2.6 °, and the groove inclination angle of the reversing part is 17.4 °, and the groove volume cross-sectional ratio of the normal rotating part and the reversing part is remarkably different. However, there is a problem in using the same as an optical fiber cable as a spacer.

Embodiment 3 FIG. The groove has a U-shaped cross-sectional shape as shown in
The apparent diameter of three 1.0 mm steel wires twisted is 3.0.
mm = 1 (mm tensile strength body 12)
0 adhesive polyethylene (manufactured by Nippon Unicar: GA00
6) and a low-density linear polyethylene (LLDPE, manufactured by Nippon Unicar Co., Ltd .; trade name NUCG5350) are coated by co-extrusion, and a pre-coated tensile strength wire 14 having an outer diameter of 6.5 mm is coated.
I got Introducing the pre-coated tensile wire 14 into the rotating die while preheating the surface to 60 ° C., and rotating the die so that the ribs and the grooves are spirally inverted alternately, the resin for forming the spacer body is formed. A high-density polyethylene having a melt index (MI) of 0.068 and a polypropylene resin having a MI of 0.237 as a groove-preserving resin are extruded at a resin temperature of 200 ° C. at the die portion, and are drawn while being cooled and solidified. I took it.

The specifications of the SZ spacer to be obtained are as follows: the outer diameter is 11.0 mm, the groove width at the opening and the center of the groove is 2.4 m.
m, 6 grooves with a groove depth of 2.0 mm, reversal pitch 23
5mm, reversal angle 360 °, minimum rib thickness T2.15
mm. In this specification, the spiral advancing angle α is 8.37 ° when determined in the same manner as described above.

The cross-sectional area of one rib is 36.7 mm
^2. Substituting the distance XG of 0.75 mm to the center of gravity and the minimum rib thickness of 2.15 mm, the rib inclination index F becomes: F = 36.7 × 0.75 × 8.37 / 2.15 = 10
7.2. In addition, as shown in FIG. 4, the rib cross-sectional area S of the specific embodiment 2 and the spacer of this embodiment is obtained by calculating an arc passing through both end points of the minimum rib thickness T, and determining a portion outside the arc. Area (hatched area in Fig. 4)
Was defined as the cross-sectional area S.

In the obtained spacer, the inclination angle of the groove in the spiral portion due to normal rotation was 2.3 °, and the groove inclination angle in the inverted portion was 5.7 °. Thus, the groove inclination was small, and the fluctuation of the groove cross-sectional volume in the longitudinal direction was small.

Comparative Example 3 SZ of the same specification as the third embodiment
In order to obtain a U-groove spacer of the type, it was manufactured without filling with a groove-shaping resin as in Example 3. The groove inclination angle of the normal rotating part of the obtained SZ spacer is 1.0 °, and the groove inclination angle of the reversing part is 12.6 °, and the groove volume cross-sectional ratio of the normal rotating part and the reversing part is different. Therefore, there has been a demand for more uniformity when used in an optical fiber cable as a spacer.

[0046]

As described in detail in the above embodiments, according to the spacer for an optical fiber cable according to the present invention,
When the rib inclination index is a predetermined value, more specifically, 100 or more, the groove inclination angle is set to 10 ° or less, so that the variation in groove cross-sectional volume in the longitudinal direction of the spacer is small. It can be made smaller, which contributes to miniaturization of cables and higher density of optical fibers. In addition, the variation in the groove cross-sectional volume is small, and in particular, the inclination of the groove at the inversion portion is small, so that the optical fiber can be securely stored and protected even in this portion, and the adverse effects such as an increase in the optical fiber transmission loss can be eliminated. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view and an explanatory view showing one embodiment of a square groove of an optical fiber cable spacer according to the present invention.

FIG. 2 is an explanatory diagram of a method for measuring a groove inclination angle of an optical fiber cable spacer according to the present invention.

FIG. 3 is an explanatory cross-sectional view showing one embodiment of a U-groove of the optical fiber cable spacer according to the present invention.

FIG. 4 is an explanatory cross-sectional view showing another embodiment of the U-groove of the optical fiber cable spacer according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Spacer 12 Strength member 14 Preliminary coating layer (with tensile strength line) 16 Body coating layer 20 Optical fiber storage groove 22 Rib

Claims (3)

[Claims] 1. An optical fiber cable spacer having a continuous spiral groove whose direction is periodically reversed along the longitudinal direction on the outer periphery and has a slope index (F) of a rib defining the spiral groove = rib Cross-sectional area (S) x rib center of gravity distance (X
G) × helical advancing angle (α) / minimum rib thickness (T), wherein the inclination index is set to a predetermined value or more, and the groove inclination angle in the cross section of the spacer is suppressed to 10 ° or less. Cable spacer. 2. The spacer for an optical fiber cable according to claim 1, wherein said rib inclination index is 100 or more. 3. When extruding a synthetic resin for molding a spacer main body of an optical fiber cable spacer, a resin which is not compatible with the synthetic resin for forming a main body is filled in a portion to be the spiral groove. 3. The method of manufacturing an optical fiber cable spacer according to claim 1, wherein the resin having no compatibility is peeled off later.