CN100339734C - Method for manufacturing the spacer for optical fiber cable - Google Patents

Abstract

This invention provides a method for manufacturing a spacer for an optical fiber cable by which a groove inclination of a spiral groove housing an optical fiber is controlled. A coated high-tensile wire 4 in which a preliminary coating layer is provided in the outer periphery of a high-tensile body is pre-heated by passing through a heating tank 5, thereafter the wire is introduced into an extruder 7 having a rotating die 6 corresponding to the cross section shape of the spacer, the wire is guided to a cooling zone 9 to cool it after rotating, extruding and coating a spacer main body resin layer at prescribed speed, and whereby a PE spacer 10 is obtained. Three stages of ring shaped air nozzles are set up in the cooling zone 9 along the running direction of the spacer 10. Air is almost orthogonally brown out of the nozzles toward the spacer 10 and is brown against the groove bottom of the spacer 10, and the root part of a rib is cooled preferentially more than the middle part. The spacer 10 is specified by nearly 1.5 mm in the minimum rib thickness at the root of the rib demarcating the spiral groove, 11.9 degrees in the advancing angle and nearly 15 degrees in the groove inclination angle [alpha].

Description

Manufacturing method of bushing for optical fiber cable

This application is a divisional application of Chinese patent application No. 01142934.8.

technical field

The present invention relates to a bushing for an optical fiber cable, an optical fiber cable using the bushing, and a method for manufacturing the bushing, and particularly relates to a technique for controlling the inclination angle of the inversion portion of a spiral groove for accommodating an optical fiber.

Background technique

In order to reduce the price and laying cost of optical fiber cables, great progress has been made in the research of reducing the diameter of optical fibers, reducing the weight, and increasing the density of light. Therefore, it is strictly required to use polyethylene (PE) materials to accommodate optical fibers The diameter of the bushing should also be small and the groove should be deep.

In addition, for the optical fiber cable of the empty frame, in addition to requiring high optical density, it has begun to require better branching performance at the end of the optical fiber. In order to meet these requirements, SZ optical fiber cables have been widely used. This kind of fiber optic cable uses a bush made of polyethylene material. The direction of rotation of the helical groove of the bush to accommodate the optical fiber is periodically reversed (SZ type), and a plurality of ribbons or ribbons are contained in each helical groove. single core fiber.

When accommodating a rigid tape (tape) in the SZ-type bushing, it should be ensured that only the space necessary for the tape is formed as the size of the storage groove.

In addition, the polyethylene resin used for the flange of the spiral groove will produce three-dimensional molding shrinkage during extrusion molding, that is, the sum of shrinkage caused by recrystallization when polyethylene is solidified and volume shrinkage caused by temperature drop.

When such molding shrinkage occurs, unlike the one-way spiral groove with no shrinkage allowance in the longitudinal direction, in the case of the SZ type bush, only at the reverse position, the rotation direction can be reversed to approach the form The flange shrinks longitudinally, and its structure is such that the flange on the inner side of the reversal of rotation is inclined.

Moreover, the higher the flange of the spiral groove (the deeper the groove), the more serious the inclination phenomenon. This problem and the problem of ensuring sufficient space for the spiral groove mentioned above all limit the deepening of the spiral groove of the SZ-type bushing. major factor.

Incidentally, regarding the inclination of the flange, in addition to the molding shrinkage of the resin, the stress generated between the coating resins is also a factor due to the difference in the conditions for the resin to fall out when extruding from the nozzle.

Contents of the invention

In view of the above problems, the purpose of the present invention is to suppress the inclination of the bushing with SZ-shaped helical groove for optical fiber cables in the groove of the inversion part, and to deepen the groove of the SZ-shaped bushing without deteriorating the transmission loss. depth.

In order to solve the above problems, the present invention takes the following technical solutions:

A method for manufacturing a bushing for an optical fiber cable, the body covering layer of the bushing is covered on the periphery of the middle covering layer, the bushing body covering layer is provided with a thermoplastic resin around the central tensile body, and the middle covering layer is formed, and It has a spiral groove for accommodating optical fibers that is periodically inverted in the longitudinal direction and is continuous in the longitudinal direction, and is characterized in that after the covering layer of the bushing body is formed, cooling air passes through it from a position at a certain distance from the outer periphery of the bushing The nozzle blows dry air substantially perpendicularly to the outer periphery of the bush to cool it.

The method for manufacturing a bushing for an optical fiber cable is characterized in that the cooling air nozzles are arranged in multiple stages at a certain distance apart from the bushing moving at a constant speed along the moving direction of the bushing.

The method of manufacturing the bushing for an optical fiber cable is characterized in that the cooling by the cooling air nozzle is preferentially performed at the root portion of the flange constituting the side surface of the spiral groove.

The method for manufacturing a bush for an optical fiber cable is characterized in that the coated tensile wire provided with the above-mentioned intermediate covering layer is preheated and introduced into an extruder for forming the above-mentioned main body covering layer.

The manufacturing method of the bushing for the optical fiber cable is characterized in that: the above-mentioned intermediate covering layer is made of thermoplastic resin compatible with polyethylene.

A bushing for an optical fiber cable, the body covering layer of the bushing is covered on the periphery of the middle covering layer, and the bushing body is provided with a thermoplastic resin around the central tensile body, and has a longitudinal periodicity The spiral groove for receiving optical fibers that is reversed in a vertical direction and continuous in the longitudinal direction is characterized in that: the minimum thickness of the flange constituting the side of the spiral groove is 1.5~1.85 mm, the depth of the groove is 2.5~2.8 mm, and the maximum spiral groove The angle is 8.3°~11.9°

The above-mentioned bushing for optical fiber cable is characterized in that: the inclination angle of the cross-section of the bushing at the inversion part of the above-mentioned spiral groove is less than 18°.

The above-mentioned bushing for optical fiber cable is characterized in that: the flange constituting the side of the spiral groove is set such that its density gradient gradually increases from the root to the top.

The above-mentioned bushing for an optical fiber cable is characterized in that the above-mentioned density gradient is such that the resin density at the root is the smallest compared with the resin density at the top and middle.

An optical fiber cable, characterized in that a fiber optic cable bushing according to claim 1 or 4 is used, and an optical fiber in a ribbon shape or the like is accommodated in at least one or more of the spiral grooves.

In the present invention, an intermediate covering layer of thermoplastic resin material is coated on the periphery of the central tensile body by extrusion molding; the outer periphery of the above-mentioned intermediate covering layer is covered with a bushing body covering layer, and the bushing body covering layer has a A spiral groove that is continuous in the longitudinal direction for accommodating optical fibers, and the direction of rotation of the spiral groove is periodically reversed in the longitudinal direction; the minimum thickness of the flange of the spiral groove is more than 1.0 mm, the depth of the groove is more than 2.0 mm, and the maximum helix angle is Above 8°.

Here, the helix angle of the present invention is described: as shown in Figure 5, a plurality of helical grooves are provided on the bushing, and the angle θ between the helical grooves and the longitudinal axis of the bushing or an axis parallel to it, in the present invention Defined as the helix angle, and its maximum value is called the maximum helix angle.

In the cross-section of the helical groove of the bush where the rotation direction is reversed, the inclination angle of the helical groove can be controlled below 18°.

In the bushing for an optical fiber cable according to the present invention, the material density of the flange of the spiral groove increases gradually from near the root to the top, and the resin density near the root is the smallest compared with the resin density at the top and middle.

In the bushing for optical fiber cable produced by the above method, at least one or more spiral grooves on the upper surface accommodate ribbon-shaped or other shaped optical fibers.

In addition, in the manufacturing method of the bushing for optical fiber cable of the present invention, the above-mentioned bushing body covering layer (the body covering layer of the bushing is covered on the periphery of the middle covering layer, and the body covering layer is provided with longitudinally continuous, accommodating The spiral groove for optical fiber, whose direction of rotation is periodically reversed along the longitudinal direction; the above-mentioned intermediate covering layer is made of thermoplastic resin material, and is covered around the central tensile body) Air nozzles for cooling are placed on the position; dry air is blown to the periphery of the above-mentioned bushing in an approximately vertical direction to cool the bushing.

The above-mentioned cooling air nozzles are aimed at the bushes advancing at a certain speed, and several groups are arranged along the advancing direction of the above-mentioned bushes, and the groups are separated by a certain distance.

The bushing for optical fiber cable is manufactured in this way. After the covering layer of the bushing body is formed, it is cooled by the following method: a cooling air nozzle is placed on the outer periphery of the bushing at a certain distance, and the dry air is blown in an approximately vertical direction. to the above bushing.

In this cooling method, the dry air can be directly blown to the bottom of the spiral groove, so that the root of the spiral groove flange is preferentially cooled earlier than the middle part, so it can effectively prevent the spiral groove flange from falling to the inner side of the reverse bend; A bushing with a smaller diameter can be produced, the minimum thickness of the helical groove flange in the bushing is more than 1.0mm, the groove depth is more than 2.0mm, the maximum helix angle is more than 8°, and the cross section of the reverse direction of the helix The inclination angle of the notch is below 18°.

In addition, if the inclination angle of the notch is less than 18°, the conduction loss can be reduced when the optical fiber is accommodated in the spiral groove to make an optical fiber cable.

In the present invention, the above-mentioned central tensile body coated with the intermediate covering layer may be introduced into an extrusion molding machine for processing the above-mentioned main covering layer after being preheated.

In addition, in the present invention, the material of the above-mentioned intermediate covering layer can be selected from polyethylene or a thermoplastic resin compatible with polyethylene.

Brief description of the drawings

Fig. 1 is an explanatory diagram of main parts of the manufacturing process in the manufacturing method of the optical fiber cable bushing according to the present invention

Fig. 2 Detailed diagram of the air nozzle used in the manufacturing method shown in Fig. 1

Fig. 3 is a sectional view of a bushing for an optical fiber cable manufactured by the manufacturing method shown in Fig. 1

Fig.4 Explanatory diagram of the inclination angle α of the notch of the bushing for optical fiber cables

Figure 5 Explanation of the helix angle of the helical groove of the bushing

Specific embodiments of the invention

The best embodiment of the present invention is illustrated below:

Example 1:

7 steel wires with an outer diameter of φ1.4 mm are twisted into a steel rope as the central tensile body 1 and introduced into the crosshead. Here, the outer periphery of the central tensile body 1 is press-coated with the standby inner covering layer 2 and the spare outer covering layer 3 at a temperature of 200° C. to obtain a coated tensile wire 4 . The inner covering layer 2 is ethylene-ethyl acrylate (Ethylene-Ethyl Acrylate) copolymer resin (GA-006, produced by Unika in Japan), and the outer covering layer 3 is a linear low-density polyethylene resin (NUCG5350, produced in Japan Unika-produced), the coated tensile wire 4 is that the outer diameter of the ethylene-ethyl acrylate copolymer resin layer is φ4.8 mm, and the outer diameter of the polyethylene resin coating on the outer periphery is φ9.7 mm.

As shown in FIG. 1 , the above-mentioned covered tensile wire 4 is preheated through a heating tank 5 so that the surface temperature of the covered tensile wire reaches 60°C. Then, the coated tensile wire is pulled into the extruder 7, and the rotating die 6 corresponding to the cross-sectional shape of the bush is housed in the extruder 7. As the resin for forming the resin layer 8 of the bushing body, a high-density polyethylene resin (Hizex6600M, produced by Mitsui Chemicals) with MI=0.03 (g/10min) was coated by rotary extrusion at a speed of 6 m/min, and then cooled. Zone 9 was cooled to obtain a PE bushing 10 with an outer diameter of 15.7 mm.

As shown in Figure 2, in the cooling zone 9, the annular air nozzle 11 moves along the direction of the liner 10,

Three sections are set every 300 mm.

The air nozzle 11 used in this example has a nozzle holder 11a, an annular space 11b provided inside the nozzle holder 11a, and a cooling nozzle 11c. The cooling nozzle 11c surrounds the inner peripheral opening of the annular space 11b, and the tip opening protrudes inwardly. Dry air as a cooling medium is fed in from the outer edge side of the annular space 11b.

The bush 10 is inserted in the middle of the cooling nozzle 11c, and passes in the direction indicated by the arrow at a given speed. The dry air sent to the annular space 11b passes through the cooling nozzle 11c, and blows to the bushing 10 approximately vertically at a flow rate of 20 m3 ^/ s, and blows to the bottom of the spiral groove 12 of the bushing 10, so that the spiral groove 12 is formed The root of the side flange 13 is cooled earlier than the middle part.

In addition, in this case, in the above-mentioned embodiment, the amount of dry air blown out by each nozzle 11 provided in three stages is set to the same condition, but for example, the amount of dry air blown out may be reduced as the stage reaches a later stage. , or reduce the amount of dry air blown out of the middle section. Furthermore, the number of stages in which the air nozzles 11 are installed can be appropriately selected according to the cooling capacity or the size of the cooling medium, for example.

Furthermore, the resin discharge nozzle of the rotary mold 6 is designed using its hole cross-sectional area: the cross-sectional area obtained by subtracting the cross-sectional area St of the coated tensile wire 4 from the cross-sectional area Ss of the PE bushing 10 to be made. The value Sb/Snb obtained by dividing Sb (Sb=Ss-St) by the nozzle hole cross-sectional area Sn and subtracting the cross-sectional area St of the covered tensile wire 4 from the cross-sectional area Snb (Snb=Sn-St) was 0.95.

The obtained PE bushing 10 has a cross-section as shown in Figure 3, and the outer periphery of the bushing body covering layer 8 is provided with 8 spiral grooves 12, the groove depth of each spiral groove 12 is 2.8 mm, and the width is 2.8 mm. It is slightly U-shaped, with 8 evenly distributed in the circumferential direction.

The helical groove 12 has a helical structure twisted into an SZ shape with a reverse pitch of 235 mm and a reverse angle of 360°; this helical groove has a target size and shape and can meet various specifications.

In the polyethylene bush 10, the basic minimum flange thickness of the flange 13 constituting the helical groove 12 is 1.5 mm, and the maximum helical advance angle is 11.9°.

When measuring the notch inclination a, it is quite possible to control the notch inclination at about 15°. The notch inclination angle a is defined as shown in FIG. 4 .

Take a cross-section at the inverted portion of the PE bushing 10 . As a straight line L1 connecting the center O of the bushing and the center portion A of the groove bottom, and a straight line L2 connecting the center portion A of the groove bottom and the center portion B of the groove top, the inclination angle a of the notch is defined by the distance between these straight lines L1 and L2. indicated by the angle.

In addition, one flange 13 of the SZ-shaped bush 10 formed by the bush body resin layer 8 is removed, as shown in FIG. 3 . After dividing the flange into four sections from the root of the flange to the top, when measuring the density of the resin with a density gradient tube, the flange root a is 0.9497, the flange center b is 0.9505, and the flange center c is 0.9505 , The flange top d is 0.9503.

That is to say, in the present embodiment, the density gradient of the flange 13 constituting the spiral groove 12 of the bushing 10 is set to gradually increase from near the root to the tip, and the density gradient is approximately the ratio of the resin density at the root to the tip. The resin density of the top part is the smallest compared to that of the central part.

Then, in each spiral groove 12 of this SZ-shaped bushing 10, accommodate 8 double-core ribbon optical fibers with a thickness of 0.4 millimeters and a width of 0.6 millimeters, and fill with jelly to prevent the core wire from moving or immersing in water. Afterwards, the sheath was coated by crimping (加きえ巻き) to produce a 128-core SZ-type optical fiber cable.

When the optical transmission performance of the optical fiber cable was measured, it was confirmed that it had a good performance of 0.21 to 0.22 dB/km.

Example 2:

Twist 7 steel wires with an outer diameter of φ1.0 mm into a steel rope as the central tensile body 1 and guide it into the crosshead. Here, the outer periphery of the central tensile body 1 is press-coated with the standby inner covering layer 2 and the spare outer covering layer 3 at a temperature of 200° C. to obtain a coated tensile wire 4 . The inner covering layer 2 is ethylene-ethyl acrylate (Ethylene-Echiluacryl) copolymer resin (GA-006, produced by Unica, Japan), and the outer covering layer 3 is a linear low-density polyethylene resin (NUCG5350 , produced by Unica, Japan), the coated tensile wire 4 is that the outer diameter of the ethylene-ethyl acrylate copolymer resin layer is φ3.6 millimeters, and the coated outer diameter of the polyethylene resin on its periphery is φ5.8 millimeters.

As in Example 1, pass the above-mentioned coated tensile wire 4 through the heating tank 5, preheat to 60°C, and then pull it into the extruder 7, which is equipped with a rotating die corresponding to the cross-sectional shape of the bushing. 6. As the resin for forming the bushing body resin layer 8, high-density polyethylene resin (Hizex6600M, produced by Mitsui Chemicals) with MI=0.03 (g/10min) was coated by rotary extrusion at a speed of 7.5 m/min, and then cooled. Zone 9 was cooled to obtain a PE bushing 10 with an outer diameter of 11.2 mm.

As in Embodiment 1, in the cooling zone 9, a three-stage air nozzle 11 is provided. In addition, the resin nozzle of the rotary mold 6 was designed so that the Sb/Snb value was 0.93 as described in the above-mentioned Example 1.

The prepared PE bushing 10a has 6 spiral grooves 12 evenly arranged along the circumferential direction, each spiral groove 12 is 2.5 mm deep and 2.5 mm wide, and is roughly U-shaped. The helical groove 12 has a reverse pitch of 240 mm and a reverse angle of 360°, twisted into an SZ-shaped helical structure, has a target size and shape, and meets various specifications.

The minimum thickness of the root of the flange of the PE bushing 10a is 1.85 mm, and the maximum helix angle is 8.3°.

When measuring the notch inclination angle a of the cross-section of the inverted portion of the PE bush 10a, it is sufficient to control the notch inclination to about 12°.

Furthermore, remove a flange of the SZ-shaped bushing 10a formed by the body resin layer, start from the root of the flange, and divide it into four parts to the top. When measuring the density of each section of resin with a density gradient tube, the flange The flange base a is 0.9496, the flange center b is 0.9503, the flange center c is 0.9504, and the flange top d is 0.9502.

Then, as in Example 1, 4 double-core ribbon optical fibers with a thickness of 0.4 mm and a width of 0.6 mm are accommodated in each groove, filled with jelly, and coated by crimping to form a 48-core SZ type. optic fibre cable. After measurement, the optical fiber cable has a good optical transmission performance of 0.20-0.22dB/kmd.

Example 3:

A single steel wire with an outer diameter of 2.6 mm is introduced into the crosshead as a central tensile body. On the periphery of the central tensile body, the spare inner covering layer 2 and the spare outer covering layer are co-extruded at a temperature of 200° C. to obtain a coated tensile wire 4 a. The inner covering layer is ethylene-acrylic acid ethyl ester (エチレン-エチルアルクルト) copolymer resin (GA-006, produced by Japan Unica), and the outer covering layer is a linear low-density polyethylene resin (NUCG5350, Japan Produced by Unica), the coated tensile wire 4a is that the outer diameter of the ethylene-ethyl acrylate copolymer resin layer is φ3.2 millimeters, and the coated outer diameter of the polyethylene resin on its periphery is φ4.5 millimeters.

As in Example 1, the above-mentioned coated tensile wire 4a is passed through the heating tank 5, preheated to 60°C, and then pulled into the extruder 7, which is equipped with a rotating die corresponding to the cross-sectional shape of the bushing. 6. As the resin for forming the resin layer 8 of the bushing body, a high-density polyethylene resin (Hizex6600M, produced by Mitsui Chemicals) with MI=0.03 (g/10min) was coated by rotary extrusion at a speed of 7 m/min, and then passed through the cooling zone 9. After cooling, a PE bushing 10b with an outer diameter of 10.2mm was obtained.

As in Embodiment 1, in the cooling zone 9, a three-stage air nozzle 11 is provided. In addition, the resin nozzle of the rotary mold 6 was designed so that the Sb/Snb value was 0.94 as described in the above-mentioned Example 1.

The obtained PE bushing 10b has five spiral grooves 12 evenly arranged along the circumferential direction, and each spiral groove 12 has a groove depth of 2.5 mm and a groove width of 3.0 mm, and is roughly U-shaped. The spiral groove 12 has an SZ-shaped structure with a reverse pitch of 150 mm and a reverse angle of 270°, and has a target size and shape to meet various specifications.

The root of the flange of the PE bushing 10b has a minimum thickness of 1.85mm and a maximum helix angle of 8.3°.

When measuring the notch inclination angle a of the cross-section of the inverted portion of the PE bushing 10a, the inclination of the notch is sufficiently controlled at about 13°.

Furthermore, a flange of the SZ-shaped bush 10ab formed by removing the body resin layer is divided into four parts from the root of the flange to the top. When measuring the density of each section of resin with a density gradient tube, the convex The flange base a is 0.9498, the flange center b is 0.9505, the flange center c is 0.9504, and the flange top d is 0.9503.

Then, as in Example 1, five 4-core ribbon optical fibers with a thickness of 0.40 mm and a width of 1.1 mm are accommodated in each groove, filled with jelly, and coated by crimping to form a 100-core SZ type. optic fibre cable. It has been determined that the optical fiber cable has a good optical transmission performance of 0.22dB/km.

Example 4:

Aramid fiber (Kebra-3120dtex: manufactured by Toray Dupon Co., Ltd.) was used as a reinforcing fiber, which was impregnated with vinyl resin (Esta-H-6400, manufactured by Mitsui Chemicals), shrink-molded to an outer diameter of 4.5 mm, and introduced into the cross In the head mold, extrusion-coated LLDPE resin (NUCG5350, manufactured by Unika Japan); after cooling the surface-coated resin, harden the inner vinyl resin in a steam curing tank at 145°C to obtain an outer diameter of 5.8 mm The coated tensile wire 4b.

As in Example 1, the above-mentioned coated tensile wire 4ab is passed through the heating tank 5, preheated to 60°C, and then pulled into the extruder 7, which is equipped with a rotating die corresponding to the cross-sectional shape of the bushing. 6. As the resin for forming the resin layer 8 of the bushing body, a high-density polyethylene resin (Hizex6600M, produced by Mitsui Chemicals) with MI=0.03 (g/10min) was coated by rotary extrusion at a speed of 7.5m/min, and then passed through the cooling zone. 9. Cool to obtain a PE bushing 10c with an outer diameter of 11.2 mm.

As in Embodiment 1, in the cooling zone 9, a three-stage air nozzle 11 is provided. In addition, the resin nozzle of the rotary mold 6 was designed so that the Sb/Snb value was 0.93 as described in the above-mentioned Example 1.

The obtained PE bushing 10c has six spiral grooves 12 evenly arranged along the circumferential direction, and each spiral groove 12 has a groove depth of 2.5 mm and a groove width of 2.5 mm, and is roughly U-shaped. The spiral groove 12 has an SZ-shaped structure with a reverse pitch of 240 mm and a reverse angle of 360°, and has a target size and shape to meet various specifications.

The root of the flange of the PE bushing 10c has a minimum thickness of 1.85mm and a maximum helix angle of 8.3°.

When measuring the notch inclination angle a of the cross-section of the inverted portion of the PE bushing 10c, the inclination of the notch is sufficiently controlled to about 12°.

Furthermore, remove a flange of the SZ-shaped bushing 10c formed by the body resin layer, start from the root of the flange, and divide it into four parts to the top. When measuring the density of each section of resin with a density gradient tube, the convex The flange base a is 0.9497, the flange center b is 0.9504, the flange center c is 0.9505, and the flange top d is 0.9503.

Then, as in Example 1, 4 double-core ribbon optical fibers with a thickness of 0.40 mm and a width of 0.6 mm are accommodated in each groove, filled with jelly, and coated by crimping to form a 48-core SZ type. optic fibre cable. It has been determined that the optical fiber cable has a good optical transmission performance of 0.22dB/km.

Example 5:

7 steel twisted steel wires with an outer diameter of 1.4 mm are introduced into the crosshead as the central tensile body 1 . The outer periphery of the central tensile body 1 is coated with the spare inner covering layer 2 and the spare outer covering layer 3 together by extrusion at a temperature of 200° C. to obtain a covered tensile wire 4 . The inner covering layer 2 is ethylene-ethyl acrylate (Ethylene-Echiluacryl) copolymer resin (GA-006, produced by Unica, Japan), and the outer covering layer 3 is a linear low-density polyethylene resin (NUCG5350 , produced by Unica in Japan), the coated tensile wire 4 is that the outer diameter of the ethylene-ethyl acrylate copolymer resin layer is φ4.8 millimeters, and the coated outer diameter of the polyethylene resin on its periphery is φ9.7 millimeters.

As in Example 1, pass the above-mentioned coated tensile wire 4 through the heating tank 5, preheat to 60°C, and then pull it into the extruder 7, which is equipped with a rotating die corresponding to the cross-sectional shape of the bushing. 6. As the resin for forming the bushing body resin layer 8, a high-density polyethylene resin (Hizex6600M, produced by Mitsui Chemicals) with MI=0.03 (g/10min) was coated by rotary extrusion at a speed of 6 m/min, and then passed through the cooling zone 9a After cooling, a PE bush 10d with an outer diameter of 15.7 mm was obtained.

In the cooling zone 9, the air nozzles 11 having the same configuration as in the first embodiment are provided in four stages at intervals of 300 mm along the moving direction of the liner 10d.

In the case of this embodiment, the dry air sent into the annular space 11b is blown out at a wind speed of 20 m ³ /HR approximately perpendicular to the bush 10d through the cooling nozzles 11c and cooled.

In addition, the resin nozzle of the rotary mold 6 was designed so that the Sb/Snb value was 0.95 as described in the above-mentioned Example 1.

The obtained PE bushing 10d has 8 spiral grooves 12 evenly arranged along the circumferential direction, and each spiral groove 12 has a groove depth of 2.8 mm and a groove width of 2.8 mm, and is roughly U-shaped. The spiral groove 12 has an SZ-shaped structure with a reverse pitch of 235 millimeters and a reverse angle of 360°, and has a target size and shape to meet various specifications.

The root of the flange of the PE bushing 10d has a minimum thickness of 1.5 mm and a maximum helix angle of 11.9°.

When measuring the notch inclination angle a of the cross-section of the inverted portion of the PE bushing 10d, the inclination of the notch is sufficiently controlled to about 14°.

Furthermore, remove a flange of the SZ-shaped bushing 10c formed by the body resin layer, start from the root of the flange, and divide it into four parts to the top. When measuring the density of each section of resin with a density gradient tube, the convex The flange base a is 0.9498, the flange center b is 0.9505, the flange center c is 0.9506, and the flange top d is 0.9504.

Then, as in Example 1, 8 double-core ribbon optical fibers with a thickness of 0.4 mm and a width of 0.6 mm are accommodated in each groove, filled with jelly, and coated with a jacket by crimping to form a 128-core SZ type. optic fibre cable. It has been determined that the optical fiber cable has a good optical transmission performance of 0.21dB/km. Comparative Example 1

As a method of cooling the resin of the bushing body, while passing through a SUS pipe with a length of 1 meter and an inner diameter of 75 mm and a seal ring with a hole diameter of 16.5 mm at the outlet, warm water at 40 ° C is injected into the pipe from the bottom of the pipe to make the added The concentration of the interface catalyst (Maipon FL-30, manufactured by Matsumoto Yushi Co., Ltd.) was set to 0.1%, and water was allowed to overflow from the upper side of the tube to cool and solidify. Except for this method, a PE bush with an outer diameter of 15.7 mm was produced in the same manner as in Example 1.

Although the cross-sectional size, reverse pitch and reverse angle of the SZ bushing cooled and solidified by this method are exactly the same as those in Example 1, when the notch inclination a of the cross section of the reverse part is measured, it is about 25° , that is, the notch is heavily inclined.

Furthermore, a flange of the SZ-shaped bush 1 formed by removing the body resin layer is divided into four parts from the root of the flange to the top. When measuring the density of each section of resin with a density gradient tube, the convex The flange base a is 0.9512, the flange center b is 0.9511, the flange center c is 0.9508, and the flange top d is 0.9503.

Then, as in Example 1, 8 double-core ribbon-shaped optical fibers were respectively accommodated in each groove, filled with jelly, and coated with a jacket by crimping to make a 128-core SZ optical fiber cable. After measurement, the optical fiber cable has a good optical transmission performance of 0.25-0.55dB/km.

Effect of the present invention:

As described in the above-mentioned embodiments, the bushing for an optical fiber cable manufactured by the manufacturing method of the present invention and the optical fiber cable using the bushing can effectively control the inclination of the notch of the inversion portion, without deteriorating the transmission loss, It is possible to deepen the groove depth of the SZ-shaped bush.

Claims (3)

1. A manufacturing method of a bushing for an optical fiber cable, wherein a thermoplastic resin is used to implement an intermediate covering layer around a central tensile body, the main body covering layer of the bushing is coated on the periphery of the intermediate covering layer, and the bushing body is covered The layer has spiral grooves that are periodically inverted in the longitudinal direction and are continuous in the longitudinal direction for accommodating optical fibers. It is characterized in that: after the covering layer of the above-mentioned bushing body is formed, it is cooled by cooling Use air nozzles to blow dry air to approximately perpendicular to the outer circumference of the above-mentioned bushing for cooling; The above-mentioned cooling air nozzles are arranged in multiple stages at a certain distance apart from the bushing moving at a certain speed along the moving direction of the bushing; The cooling by the above-mentioned cooling air nozzle is preferentially carried out in advance at the base portion of the flange constituting the side surface of the above-mentioned spiral groove. 2. The method of manufacturing a bushing for an optical fiber cable according to claim 1, wherein the coated tensile wire provided with the intermediate covering layer is preheated and introduced into an extruder for forming the main body covering layer. 3. The method for manufacturing a bushing for an optical fiber cable according to any one of claims 1 to 2, wherein the intermediate covering layer is made of a thermoplastic resin compatible with polyethylene.

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