JP4409111B2 - Manufacturing method of SZ slot for optical cable - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing an SZ slot for an optical cable used for a slot type optical cable or the like.
[0002]
[Prior art]
Such SZ slots are disclosed in Japanese Patent Laid-Open Nos. 11-109194 and 11-174295.
As shown in FIG. 5, the SZ slot is provided with a lower layer 2 made of polyethylene or the like on the outer periphery of a tension member 1 made of a steel wire, a steel stranded wire or the like, and one or more helical grooves 3 on the outer periphery of the lower layer 2. 3 is a slot layer 4 formed of polyethylene or the like formed in the SZ direction.
[0003]
Here, the SZ direction is formed by repeating a spiral groove in the S direction and a spiral groove in the Z direction alternately at a certain period, similarly to “SZ twist” known in the field of metal twisted wire. In other words, when one spiral groove is developed on a plane, the spiral groove draws a substantially sinusoidal locus.
[0004]
In this SZ slot manufacturing method, the metal wire to be the tension member 1 is supplied to the crosshead die of the extruder, and polyethylene or the like is extrusion coated on the metal wire to form the lower layer 2 having a circular cross section first. To do.
Next, the metal wire covered with the lower layer 2 is supplied again to the crosshead die on which the rotary die of the extruder is mounted, and the rotary die is alternately rotated forward and reversely, and the SZ direction is formed on the lower layer 2. The slot groove 4 in which one or more helical grooves 3 and 3 are formed is coated and formed.
[0005]
In the manufacturing method of the prior invention, when the slot layer 4 is extrusion-coated, the temperature of the metal wire on which the lower layer 2 supplied to the crosshead die is formed is 30 to 60 ° C. It is said that it is important to obtain 4.
However, in this manufacturing method, since the extrusion operation is performed twice for forming the lower layer 2 and the slot layer 4, there is a disadvantage that the workability is poor and the cost is increased.
[0006]
For this reason, a method of manufacturing an SZ slot by forming a layer composed of a lower layer and a slot layer on a metal wire serving as a tension member at a stroke by a single extrusion operation is considered.
However, in this new manufacturing method, if the temperature of the metal wire supplied to the crosshead die of the extruder is kept at 30 to 60 ° C. as in the previous manufacturing method, it is clear that the following defects occur. became.
[0007]
That is, it has been clarified that the inversion angle of the spiral groove of the obtained SZ slot varies and becomes unstable.
Here, the inversion angle of the spiral groove refers to the rotation angle from the start of normal rotation of the rotary die to the inversion. In other words, it refers to the rotation angle between one pitch of one sinusoidal helical groove.
The reason for the change in the reversal angle is that the rib of the slot part falls down inside the reversal part in the reversal part of the spiral groove. When the temperature of the metal wire is 30 to 60 ° C., the extruded molten resin is cooled. It is thought that the upper part of the rib located outside cools down first, solidifies and falls down.
[0008]
[Problems to be solved by the invention]
Therefore, the subject in this invention is obtaining the manufacturing method which can prevent the fluctuation | variation of the inversion angle of a spiral groove, when manufacturing an SZ slot by one extrusion coating operation.
[0009]
[Means for Solving the Problems]
Such a problem is that a metal wire serving as a tension member is supplied to a crosshead die of an extruder, a molten resin is extrusion coated thereon, a tension member is inserted in the center, and one or more helical grooves are formed on the outer periphery. When manufacturing the slot formed in the direction, a cooling device is arranged in front of the crosshead die to cool the metal wire serving as the tension member, and the temperature of the metal wire supplied to the crosshead die is 0 ° C. or higher. This can be solved by a method of lower than 30 ° C.
It is desirable to apply an adhesive to the metal wire in advance to improve the adhesion with the slot portion formed thereon.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
FIG. 1 shows an example of a production apparatus for carrying out the production method of the present invention.
In FIG. 1, first, a metal wire 11 such as a steel wire or a steel stranded wire serving as a tension member is continuously fed from a feed reel 12 and sent to an adhesive application device 13. The metal wire 11 is coated with an adhesive such as styrene-ethylene-butylene-styrene block copolymer, and then sent to a drying furnace 14 where it is heated to about 150 to 250 ° C. The solvent is volatilized and removed.
[0011]
Next, the metal wire 11 coated with this adhesive is sent to a cooling device 15 where it is cooled to 0 ° C. or more and less than 30 ° C. As the cooling device used here, for example, a device that blows low-temperature air from a Freon refrigerator is used.
When the temperature of the metal wire 11 is lower than 0 ° C., icing occurs on the surface of the metal wire 11 and unevenness is generated on the bottom surface of the spiral groove of the obtained SZ slot. Further, when the temperature is 30 ° C. or higher, the spiral groove inversion angle varies.
[0012]
Next, the metal wire 11 maintained at a temperature of 0 ° C. or higher and lower than 30 ° C. is fed into the crosshead die 17 of the extruder 16.
The crosshead die 17 is equipped with a rotating die, and a helical groove in the SZ direction is formed by extruding a molten resin such as polyethylene from the extruder 16 while rotating and rotating the rotating die alternately. The manufactured SZ slot 18 is manufactured.
[0013]
Thus, the SZ slot 18 having the structure shown in FIG. 2 is continuously manufactured from the crosshead die 17 of the extruder 16. In the SZ slot 18 having this structure, the slot layer 4 is directly formed on the tension member 1 via a thin adhesive layer (not shown). As shown in FIG. It does not have.
[0014]
According to such a manufacturing method, since the temperature of the metal wire 11 when entering the crosshead die 17 is set to a low temperature, the molten resin extruded to the periphery of the metal wire 11 is rapidly cooled, and the ribs of the spiral groove 3 are formed. Deformation is suppressed and fluctuation of the inversion angle is prevented.
Further, since the SZ slot can be manufactured at a time by one extrusion coating operation, the manufacturing cost can be suppressed.
[0015]
Further, in the production method of the present invention, the metal wire 11 is subjected to surface treatment such as sandblasting and pickling so as to increase the affinity for the resin forming the slot layer 4 made of polyethylene or the like. In such a metal wire, the application of the adhesive can be omitted .
[0016]
Specific examples are shown below.
An outer diameter of 8.0 mm, an inversion angle of 275 degrees, an inversion pitch of 175 mm, five spiral grooves, a tension member diameter of 2.0 mm steel wire, and a polyethylene SZ slot were manufactured by the above-described manufacturing method.
At this time, the cooling condition of the adhesive-coated steel wire entering the crosshead die was changed to change the temperature of the steel wire, and the reversal angle of the spiral groove of the obtained SZ slot was measured.
First, when the temperature of the steel wire is around 13 ° C., the rotation angle of the rotary die of the crosshead die is adjusted so that the reversal angle is 275 degrees, and then the temperature of the steel wire is gradually increased to obtain The inversion angle of the SZ slot was measured.
The relationship between the inversion angle of the measurement result and the temperature of the steel wire is shown in the graph of FIG.
[0017]
From the graph of FIG. 3, it can be seen that when the temperature of the steel wire exceeds 30 ° C., the inversion angle becomes smaller than the specified value.
Next, in order to elucidate the cause of this phenomenon, the cross section of the slot in the inverted part of the spiral groove was observed, and it was found that the rib fell inside the inverted part, and therefore the inversion angle was reduced. It was.
FIG. 4 shows the relationship between the rib collapse (degree) and the temperature of the steel wire.
[0018]
From the graph of FIG. 4, the change state of the rib collapse also increases when the temperature of the steel wire exceeds 30 ° C., similarly to the inversion angle. From this point, it has been clarified that, by setting the temperature of the metal wire to less than 30 ° C., an SZ slot with stable inversion angle and rib collapse can be manufactured by one extrusion coating operation.
[0019]
【The invention's effect】
As described above, according to the method of manufacturing the SZ slot for an optical cable of the present invention, the metal wire serving as the tension member is supplied to the crosshead die of the extruder, the molten resin is extrusion coated thereon, and the tension member is at the center. When manufacturing a slot that is inserted and has one or more helical grooves formed in the SZ direction on the outer periphery, the temperature of the metal wire supplied to the crosshead die is set to 0 ° C. or more and less than 30 ° C.
Therefore, there is an effect that an optical cable SZ slot with a small fluctuation of the spiral groove inversion angle can be manufactured efficiently and inexpensively by one extrusion coating operation.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of a production apparatus that can be suitably used in the production method of the present invention.
FIG. 2 is a schematic cross-sectional view showing an example of an SZ slot for an optical cable obtained by the manufacturing method of the present invention.
FIG. 3 is a chart showing test results of examples.
FIG. 4 is a chart showing test results of examples.
FIG. 5 is a schematic cross-sectional view showing an SZ slot for an optical cable obtained by a conventional manufacturing method.
[Explanation of symbols]
11 ... Metal wire, 16 ... Extruder, 17 ... Crosshead die

Claims (2)

A metal wire serving as a tension member is supplied to the crosshead die of the extruder, and the molten resin is extrusion coated on the die. The tension member is inserted in the center, and one or more helical grooves are formed in the SZ direction on the outer periphery. When manufacturing the slot
An optical cable characterized in that a cooling device is disposed in front of the crosshead die to cool the metal wire serving as a tension member, and the temperature of the metal wire supplied to the crosshead die is set to 0 ° C. or higher and lower than 30 ° C. Manufacturing method for SZ slot. 2. The method for producing an SZ slot for an optical cable according to claim 1, wherein an adhesive is applied in advance to the metal wire used as the tension member.

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