Wire body manufacturing method and wire body manufacturing device

Abstract

A wire body manufacturing method according to the present invention comprises: a step for measuring the width of a wire body at each of a first position in the axial direction and a second position in the axial direction; and a step for determining twisting of the wire body. A first width direction of the width of the wire body measured at the first position and a second width direction of the width of the wire body measured at the second position are parallel to each other. In the determination step, when a first change over time in the width of the wire body at the first position and a second change over time in the width of the wire body at the second position are different from each other, it is determined that twisting of the wire body has occurred.

Description

Method for manufacturing a filament and apparatus for manufacturing a filament

[0001] This application claims priority to Japanese Patent Application No. 2024-043288, filed March 19, 2024, and incorporates by reference all of the contents of that application.

[0002] Patent Document 1 discloses a method for measuring the twist of a filament, in which the twist of the filament is measured based on the intensity distribution of light transmitted through the filament.

[0003] International Publication No. 2023 / 095916

[0004] A method for manufacturing a wire according to one aspect of the present disclosure includes the steps of: pulling the wire along an axial direction of the wire; measuring the width of the wire at a first position in the axial direction and a second position in the axial direction; and determining whether the wire is twisted. The first width direction of the wire measured at the first position and the second width direction of the wire measured at the second position are parallel to each other. In the determining step, it is determined that the wire is twisted if the first change in the width of the wire at the first position and the second change in the width of the wire at the second position are different from each other.

[0005] Fig. 1 is a schematic diagram of a filament manufacturing apparatus according to one embodiment. Fig. 2 is a partially enlarged view of the manufacturing apparatus shown in Fig. 1. Fig. 3 is a partially enlarged view of the manufacturing apparatus shown in Fig. 1. Fig. 4 is a flowchart showing each step of a filament manufacturing method using the manufacturing apparatus shown in Fig. 1. Fig. 5 is a flowchart showing the twist determination step of the manufacturing method shown in Fig. 4. Parts (a) to (d) of Fig. 6 are schematic diagrams showing changes in the width of the filament at each position over time. Parts (a) to (d) of Fig. 7 are schematic diagrams showing changes in the width of the filament at each position over time.

[0006] [Problem to be Solved by the Present Disclosure] In the method for manufacturing a filament described in Patent Document 1, there are cases where it is required to determine the twist of the filament by a simpler method.

[0007] Effect of the Present Disclosure According to the present disclosure, it is possible to provide a method and an apparatus for manufacturing a filament that are capable of determining the twist of a filament with a simple configuration.

[0008] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described.

[0009] (1) A method for manufacturing a wire according to one aspect of the present disclosure includes the steps of: pulling the wire along an axial direction of the wire; measuring the width of the wire at a first position in the axial direction and a second position in the axial direction; and determining whether the wire is twisted. A first width direction of the wire measured at the first position and a second width direction of the wire measured at the second position are parallel to each other. In the determining step, it is determined that the wire is twisted if a first change in the width of the wire at the first position and a second change in the width of the wire at the second position are different from each other.

[0010] In the determining step in the method for manufacturing a filament (1), if a first change in width of the filament at the first position and a second change in width of the filament at the second position are different from each other, it is determined that twisting of the filament has occurred. This method for manufacturing a filament allows twisting of the filament to be determined in a simple manner.

[0011] (2) A method for manufacturing a wire according to another aspect of the present disclosure may include the steps of: pulling the wire along an axial direction of the wire; measuring the width of the wire at a first position in the axial direction and a second position in the axial direction; and determining whether the wire is twisted. A first width direction of the wire measured at the first position and a second width direction of the wire measured at the second position are parallel to each other. In the determining step, it is determined that no twist has occurred in the wire when a first change in the width of the wire at the first position and a second change in the width of the wire at the second position match each other.

[0012] In the determining step in the method for manufacturing a filament (2), if the first change in width of the filament at the first position and the second change in width of the filament at the second position are equal to each other, it is determined that the filament is not twisted. This method for manufacturing a filament allows for a simple method for determining whether the filament is twisted.

[0013] (3) In the method for manufacturing a filament according to (1), the measuring step may measure the width of the filament at a third position in the axial direction and a fourth position in the axial direction. A third width direction of the width of the filament measured at the third position and a fourth width direction of the width of the filament measured at the fourth position may be parallel to each other. In the determining step, it may be determined that twisting of the filament has occurred if the first change over time and the second change over time of the width of the filament at the third position are different from each other and the third change over time of the width of the filament at the fourth position are different from each other. This allows for more accurate determination of twisting of the filament.

[0014] (4) The method for manufacturing a filament according to (1) or (3) above may further include a step of untwisting the filament if it is determined in the determining step that twisting of the filament has occurred, thereby suppressing twisting of the filament.

[0015] (5) In the method for manufacturing a filament according to any one of (1) to (4) above, the measuring step may determine the width of the filament based on an image of the filament captured by a camera, thereby enabling the width of the filament to be measured with high accuracy.

[0016] (6) A filament manufacturing apparatus according to an aspect of the present disclosure includes a traction mechanism that traction the filament along an axial direction of the filament, a first measuring device that is provided at a first position in the axial direction and that measures the width of the filament, and a second measuring device that is provided at a second position in the axial direction and that measures the width of the filament, wherein a first width direction of the filament measured at the first position and a second width direction of the filament measured at the second position are parallel to each other.

[0017] The wire manufacturing apparatus (6) above includes a first measuring device disposed at a first position in the axial direction and configured to measure the width of the wire, and a second measuring device disposed at a second position in the axial direction and configured to measure the width of the wire. Therefore, a first change in the width of the wire at the first position can be measured over time, and a second change in the width of the wire at the second position can be measured over time. This allows determination of the occurrence of twist in the wire when the first change and the second change over time are different from each other. Moreover, as described above, because the twist of the wire is determined based on the width of the wire, the twist of the wire can be determined by a simpler method than, for example, when light transmitted through the wire is used. Therefore, this wire manufacturing apparatus allows determination of the twist of the wire by a simple method.

[0018] [Details of the embodiments of the present disclosure] Specific examples of the method and apparatus for manufacturing a filamentous body according to the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. In the description of the drawings, the same elements are given the same reference numerals, and duplicate explanations will be omitted.

[0019] FIG. 1 is a schematic diagram of a wire manufacturing apparatus according to this embodiment. The wire manufacturing apparatus 1 shown in FIG. 1 is specifically an optical fiber manufacturing apparatus. As shown in FIG. 1, the wire manufacturing apparatus (hereinafter simply referred to as the "manufacturing apparatus") 1 includes a heating furnace 2, a cooler 3, a die 4, a light irradiator 5, a pulling mechanism 6, a guide roller 7, and a winding drum 8. The manufacturing apparatus 1 manufactures a wire. The wire is a long object having a certain diameter. The wire is, for example, an optical fiber, an electric wire, or a cable comprising a plurality of such wires. The material of the wire may be, for example, glass, metal, resin, fiber, or a composite thereof. The cross section of the wire has, for example, a circular shape. The circular shape referred to here does not need to be a strict perfect circle. The circular shape may be, for example, an ellipse with some distortion. In this embodiment, the wire is, for example, a single-core optical fiber, a multi-core optical fiber, or a polarization-maintaining optical fiber. In this embodiment, the manufacturing apparatus 1 manufactures, for example, an optical fiber 20 as the filament.

[0020] The heating furnace 2 has, for example, a container that contains the preform 21, a heater for heating the preform 21 contained in the container, etc. The heating furnace 2 heats the preform 21 until it melts. The melted preform 21 is drawn out of the heating furnace 2 as the optical fiber 20. In other words, the optical fiber 20 is drawn from the heating furnace 2. The optical fiber 20 runs along the axial direction (Z-axis direction) of the optical fiber 20.

[0021] The cooler 3 is disposed downstream (hereinafter simply referred to as the “downstream side”) of the heating furnace 2 in the travel path of the optical fiber 20. The cooler 3 cools the optical fiber 20 discharged from the heating furnace 2.

[0022] The die 4 is disposed downstream of the cooler 3. The die 4 applies resin to the surface of the optical fiber 20. The die 4 has a metal jig including a hole and liquid resin contained in the metal jig. When the optical fiber 20 passes through the hole of the die 4, the liquid resin is applied to the surface of the optical fiber 20. The resin is, for example, an ultraviolet-curable resin.

[0023] The light irradiator 5 is disposed downstream of the die 4. The light irradiator 5 irradiates the optical fiber 20 with ultraviolet light, thereby hardening the liquid resin applied to the surface of the optical fiber 20.

[0024] The pulling mechanism 6 pulls the optical fiber 20 drawn from the heating furnace 2 along the axial direction of the optical fiber 20. As a result, the optical fiber 20 runs along the Z-axis direction between the heating furnace 2 and the guide rollers 7.

[0025] The guide roller 7 is disposed downstream of the light irradiator 5. In this embodiment, the guide roller 7 is a roller disposed directly below the preform 21 in the Z-axis direction (vertical direction). The guide roller 7 changes the running direction of the optical fiber 20. After passing the guide roller 7, the optical fiber 20 running along the Z-axis direction runs in a direction intersecting the Z-axis direction.

[0026] The pulling mechanism 6 is disposed downstream of the guide roller 7. The pulling mechanism 6 takes up the optical fiber 20. The winding drum 8 is disposed downstream of the pulling mechanism 6. The winding drum 8 takes up the optical fiber 20.

[0027] The manufacturing apparatus 1 further includes a first camera 11 (first measuring device), a second camera 12 (second measuring device), a third camera 13 (third measuring device), and a fourth camera 14 (fourth measuring device). In this embodiment, the first camera 11, the second camera 12, the third camera 13, and the fourth camera 14 are arranged between the cooler 3 and the die 4. All of the first camera 11, the second camera 12, the third camera 13, and the fourth camera 14 may be arranged between the die 4 and the guide roller 7.

[0028] FIG. 2 is a partially enlarged view of the manufacturing apparatus 1 as viewed from the Y-axis direction. FIG. 3 is a partially enlarged view of the manufacturing apparatus 1 as viewed from the X-axis direction. As shown in FIGS. 2 and 3 , the first camera 11 is provided at a first position P1 in the Z-axis direction. In this embodiment, the first position P1 is downstream of the cooler 3. The first optical axis 11a of the first camera 11 intersects with the Z-axis direction (the axis of the optical fiber 20). In this embodiment, the first optical axis 11a of the first camera 11 is parallel to the X-axis direction. The first camera 11 captures an image of the optical fiber 20 at the first position P1. The first camera 11 measures the width of the optical fiber 20 at the first position P1. The first width direction of the width of the optical fiber 20 measured at the first position P1 is parallel to the Y-axis direction. The "width of the optical fiber (filament)" refers to the outer diameter of the optical fiber (filament). The "width of the optical fiber (filament)" may be the outer diameter of either the portion of the optical fiber 20 located upstream of the die 4 (the portion before the resin is applied) or the portion of the optical fiber 20 located downstream of the light irradiator 5 (the portion after the resin is applied).

[0029] The second camera 12 is provided at a second position P2 in the Z-axis direction. In this embodiment, the second position P2 is located downstream of the first position P1. The second optical axis 12a of the second camera 12 intersects with the Z-axis direction (the axis of the optical fiber 20). In this embodiment, the second optical axis 12a of the second camera 12 is parallel to the X-axis direction. That is, the second optical axis 12a of the second camera 12 is parallel to the first optical axis 11a of the first camera 11. The second camera 12 faces the same direction as the first camera 11. The second camera 12 captures an image of the optical fiber 20 at the second position P2. The second camera 12 measures the width of the optical fiber 20 at the second position P2. A second width direction of the width of the optical fiber 20 measured at the second position P2 is parallel to the Y-axis direction.

[0030] The third camera 13 is provided at a third position P3 in the Z-axis direction. In this embodiment, the third position P3 is between the first position P1 and the second position P2. The third optical axis 13a of the third camera 13 intersects with the Z-axis direction (the axis of the optical fiber 20). In this embodiment, the third optical axis 13a of the third camera 13 is parallel to the Y-axis direction. In this embodiment, when viewed from the Z-axis direction, the third optical axis 13a is perpendicular to the first optical axis 11a. The third camera 13 captures an image of the optical fiber 20 at the third position P3. The third camera 13 measures the width of the optical fiber 20 at the third position P3. A third width direction of the width of the optical fiber 20 measured at the third position P3 is parallel to the X-axis direction.

[0031] The fourth camera 14 is provided at a fourth position P4 in the Z-axis direction. In this embodiment, the fourth position P4 is located downstream of the second position P2. The fourth optical axis 14a of the fourth camera 14 intersects with the Z-axis direction (the axis of the optical fiber 20). In this embodiment, the fourth optical axis 14a of the fourth camera 14 is parallel to the Y-axis direction. That is, the fourth optical axis 14a of the fourth camera 14 is parallel to the third optical axis 13a of the third camera 13. The fourth camera 14 faces the same direction as the third camera 13. In this embodiment, when viewed from the Z-axis direction, the fourth optical axis 14a is perpendicular to the second optical axis 12a. The fourth camera 14 captures an image of the optical fiber 20 at the fourth position P4. The fourth camera 14 measures the width of the optical fiber 20 at the fourth position P4. A fourth width direction of the width of the optical fiber 20 measured at the fourth position P4 is parallel to the X-axis direction.

[0032] In this embodiment, as described above, the first position P1, the second position P2, the third position P3, and the fourth position P4 are different from one another. The position of the first camera 11 in the X-axis direction and the position of the second camera 12 in the X-axis direction may be the same or different from one another. The position of the third camera 13 in the Y-axis direction and the position of the fourth camera 14 in the Y-axis direction may be the same or different from one another. "Parallel" means substantially parallel within a margin of error. "Orthogonal" means substantially perpendicular within a margin of error.

[0033] Next, a method for manufacturing a filament using the manufacturing apparatus 1 (hereinafter simply referred to as the "manufacturing method") will be described. Fig. 4 is a flowchart showing each step of the method for manufacturing a filament using the manufacturing apparatus 1.

[0034] As shown in Figure 4, the manufacturing method includes a drawing step S1, a cooling step S2, a coating step S3, a curing step S4, a take-up step S5, a winding step S6, and a twist-removing step S7. In the drawing step S1, the preform 21 is heated by a heating furnace 2. An optical fiber 20 is drawn from the end of the molten preform 21. In the cooling step S2, the optical fiber 20 is cooled by a cooler 3. In the coating step S3, a liquid resin is applied to the surface of the optical fiber 20 by a die 4. In the curing step S4, the liquid resin applied to the surface of the optical fiber 20 is cured by a light irradiator 5. In the take-up step S5, the optical fiber 20 is pulled along the Z-axis direction. In the take-up step S5, the optical fiber 20 is pulled by a pulling mechanism 6. The take-up step S5 corresponds to a pulling step. In the winding step S6, the optical fiber 20 is wound around a winding drum 8. In the twist elimination step S7, if it is determined in the twist determination step described below that a twist has occurred in the optical fiber 20, the twist of the optical fiber 20 is eliminated. Specifically, for example, the guide roller 7 is moved along the Y-axis direction, or the angle of the rotation axis of the guide roller 7 with respect to the Y-axis direction is adjusted, thereby eliminating the twist of the optical fiber 20. The twist elimination step S7 corresponds to the elimination step.

[0035] The manufacturing method further includes a twist determination step. Fig. 5 is a flowchart showing the twist determination step. As shown in Fig. 5, in the twist determination step, first, images of the optical fiber 20 are captured by the first camera 11, the second camera 12, the third camera 13, and the fourth camera 14 (step S11). In step S11, images of the optical fiber 20 are repeatedly captured while the optical fiber 20 is running.

[0036] Next, the width of the optical fiber 20 is measured (step S12). In step S12, the width of the optical fiber 20 at each of the first position P1, the second position P2, the third position P3, and the fourth position P4 is determined based on the images of the optical fiber 20 captured by the first camera 11, the second camera 12, the third camera 13, and the fourth camera 14. Specifically, in step S12, based on the first captured image by the first camera 11, the width of the optical fiber 20 in, for example, the Y-axis direction is measured as the width of the optical fiber 20 at the first position P1. In step S12, based on the second captured image by the second camera 12, the width of the optical fiber 20 in, for example, the Y-axis direction is measured as the width of the optical fiber 20 at the second position P2. In step S12, based on the third captured image by the third camera 13, the width of the optical fiber 20 in, for example, the X-axis direction is measured as the width of the optical fiber 20 at the third position P3. In step S12, based on the fourth image captured by the fourth camera 14, for example, the width of the optical fiber 20 in the X-axis direction is measured as the width of the optical fiber 20 at the fourth position P4.

[0037] In step S12, the width of the optical fiber 20 is continuously measured at each position while the optical fiber 20 is running. That is, in step S12, the change in the width of the optical fiber 20 at each position over time is measured (see, for example, FIG. 6 or FIG. 7). The width of the optical fiber 20 is measured, for example, by image processing. Steps S11 and S12 correspond to measuring steps.

[0038] Next, the twist of the optical fiber 20 is determined based on the first captured image by the first camera 11, the second captured image by the second camera 12, the third captured image by the third camera 13, and the fourth captured image by the fourth camera 14. Specifically, it is determined whether a first change over time in the width of the optical fiber 20 at the first position P1 measured based on the first captured image and a second change over time in the width of the optical fiber 20 at the second position P2 measured based on the second captured image are different from each other, and it is determined whether a third change over time in the width of the optical fiber 20 at the third position P3 measured based on the third captured image and a fourth change over time in the width of the optical fiber 20 at the fourth position P4 measured based on the fourth captured image are different from each other (step S13). Here, the start time of the first change over time is the same as the start time of the second change over time, the end time of the first change over time is the same as the end time of the second change over time, the start time of the third change over time is the same as the start time of the fourth change over time, and the end time of the third change over time is the same as the end time of the fourth change over time. "The changes in the width of the optical fiber (filament) are different from each other" means that the behavior of the change in width of the optical fiber (filament) is substantially different from each other. "Behavior" refers to, for example, the difference between the maximum and minimum values ​​of the width.

[0039] If the first and second time-dependent changes are different from each other (step S13: YES), it is determined that twisting has occurred in the optical fiber 20 (step S14). In step S14, if the third and fourth time-dependent changes are different from each other, it is determined that twisting has occurred in the optical fiber 20. This improves the accuracy of the determination.

[0040] 6A to 6D are graphs showing examples in which the changes over time are different from one another. Part (a) of Fig. 6 is a schematic diagram showing a first change over time in the width of the optical fiber 20 at the first position P1. Part (b) of Fig. 6 is a schematic diagram showing a second change over time in the width of the optical fiber 20 at the second position P2. Part (c) of Fig. 6 is a schematic diagram showing a third change over time in the width of the optical fiber 20 at the third position P3. Part (d) of Fig. 6 is a schematic diagram showing a fourth change over time in the width of the optical fiber 20 at the fourth position P4. Note that each graph shown in parts (a) to (d) of Fig. 6 shows the results of measurements taken over the same time period, with the horizontal axis representing time and the vertical axis representing the width of the optical fiber 20.

[0041] As shown in parts (a) and (b) of Figure 6, the difference between the maximum and minimum width values ​​in the first change over time is greater than the difference between the maximum and minimum width values ​​in the second change over time. Similarly, as shown in parts (c) and (d) of Figure 6, the difference between the maximum and minimum width values ​​in the third change over time is greater than the difference between the maximum and minimum width values ​​in the fourth change over time. When parts (a) to (d) of Figure 6 are visually observed, it is clear that the first change over time is clearly different from the second change over time, and that the third change over time is also clearly different from the fourth change over time. In such cases, it is determined that twisting has occurred in the optical fiber 20 from the difference between the first change over time and the second change over time or the difference between the third change over time and the fourth change over time.

[0042] If the first and second time-dependent changes are consistent with each other and the third and fourth time-dependent changes are consistent with each other (step S13: NO), it is determined that no twisting has occurred in the optical fiber 20 (step S15). "Time-dependent changes in the width of the optical fiber (filament) are consistent with each other" means that the behaviors of the changes in the width of the optical fiber (filament) are substantially consistent with each other (there is essentially no difference).

[0043] Fig. 7 is a graph showing an example in which the changes over time are consistent with each other. Part (a) of Fig. 7 is a schematic diagram showing a first change over time in the width of the optical fiber 20 at the first position P1. Part (b) of Fig. 7 is a schematic diagram showing a second change over time in the width of the optical fiber 20 at the second position P2. Part (c) of Fig. 7 is a schematic diagram showing a third change over time in the width of the optical fiber 20 at the third position P3. Part (d) of Fig. 7 is a schematic diagram showing a fourth change over time in the width of the optical fiber 20 at the fourth position P4. Note that each graph shown in parts (a) to (d) of Fig. 7 is the result of measurement during the same time period, with the horizontal axis representing time and the vertical axis representing the width of the optical fiber 20.

[0044] As shown in parts (a) and (b) of Figure 7, the difference between the maximum and minimum width values ​​in the first change over time is substantially equal to the difference between the maximum and minimum width values ​​in the second change over time. Similarly, as shown in parts (c) and (d) of Figure 7, the difference between the maximum and minimum width values ​​in the third change over time is substantially equal to the difference between the maximum and minimum width values ​​in the fourth change over time. When parts (a) to (d) of Figure 7 are visually observed, it can be seen that the first change over time is equal to the second change over time, and that the third change over time is equal to the fourth change over time. In such cases, it is determined that no twisting has occurred in the optical fiber 20. Steps S13, S14, and S15 correspond to the determination steps.

[0045] The present disclosure is not limited to the above-described embodiments.

[0046] In the embodiment, the first camera 11, the second camera 12, the third camera 13 and the fourth camera 14 are arranged between the cooler 3 and the die 4, but all of the first camera 11, the second camera 12, the third camera 13 and the fourth camera 14 may be arranged at any position between the light irradiator 5 and the guide roller 7, for example.

[0047] The distance between the first position P1 and the second position P2 and the distance between the third position P3 and the fourth position P4 may be the same or different. Depending on the distance between the cameras, it may appear that no twisting of the optical fiber 20 has occurred. For example, if the distance between the first position P1 and the second position P2 is equal to the length of the optical fiber 20 when twisted one turn, even if a twist has occurred in the optical fiber 20, the measurement results at the first position P1 and the measurement results at the second position P2 will match, and it may be determined that no twisting has occurred in the optical fiber 20. In this case, one or more additional cameras may be installed, and the width of the optical fiber 20 may be measured at the third position P3 from the same direction as the second position P2, thereby making the distance between the second position P2 and the third position P3 different from the distance between the first position P1 and the second position P2, and measuring the width of the optical fiber 20. If it is determined that no twisting occurs between the first position P1 and the second position P2, and further if it is determined that no twisting occurs between the second position P2 and the third position P3, it can be determined that no twisting occurs in the optical fiber 20. Since the length of the optical fiber 20 when twisted one turn is often 50 mm or more, if the distance between the cameras is set to about 50 mm, it is possible to accurately determine the twisting of the optical fiber 20 between the cameras.

[0048] In the embodiment, the third camera 13 is provided at the third position P3, but the third camera 13 may be provided at the first position P1. In the embodiment, the fourth camera 14 is provided at the fourth position P4, but the fourth camera 14 may be provided at the second position P2.

[0049] In the embodiment, when viewed from the Z-axis direction, the third optical axis 13a is perpendicular to the first optical axis 11a, and the fourth optical axis 14a is perpendicular to the second optical axis 12a, but when viewed from the Z-axis direction, the third optical axis 13a may intersect the first optical axis 11a obliquely, and the fourth optical axis 14a may intersect the second optical axis 12a obliquely.

[0050] In the embodiment, the manufacturing apparatus 1 includes the first camera 11, the second camera 12, the third camera 13, and the fourth camera 14. However, the manufacturing apparatus 1 may not include, for example, the third camera 13 and the fourth camera 14. In this case, if the first change over time and the second change over time are different from each other, it may be determined that twisting has occurred in the optical fiber 20. Furthermore, if the first change over time and the second change over time are the same from each other, it may be determined that twisting has not occurred in the optical fiber 20.

[0051] In the embodiment, when the first change over time and the second change over time are different from each other and the third change over time and the fourth change over time are different from each other, it is determined that twisting of the optical fiber 20 has occurred. However, when the first change over time and the second change over time are different from each other and the third change over time and the fourth change over time are consistent with each other, or when the first change over time and the second change over time are consistent with each other and the third change over time and the fourth change over time are different from each other, it may also be determined that twisting of the optical fiber 20 has occurred.

[0052] In the embodiment, the measuring devices are the first camera 11, the second camera 12, the third camera 13, and the fourth camera 14. However, each measuring device may have, for example, a light emitting unit that emits laser light and a light detecting unit that detects the laser light. The light detecting unit detects the laser light that has passed through the optical fiber 20 or the laser light that has been reflected by the optical fiber 20. The width of the optical fiber 20 at each of the first position P1, the second position P2, the third position P3, and the fourth position P4 may be measured based on the detection results of the laser light. The manufacturing apparatus 1 may be provided with at least the first measuring device and the second measuring device, but may be provided with, for example, five or more measuring devices.

[0053] The manufacturing method does not necessarily include step S7.

[0054] In the embodiment, the optical fiber 20 is a filament, but the filament may be, for example, an electric wire.

[0055] REFERENCE SIGNS LIST 1... Manufacturing apparatus 2... Heating furnace 3... Cooler 4... Die 5... Light irradiator 6... Traction mechanism 7... Guide roller 8... Winding drum 11... First camera 11a... First optical axis 12... Second camera 12a... Second optical axis 13... Third camera 13a... Third optical axis 14... Fourth camera 14a... Fourth optical axis 20... Optical fiber (filament) 21... Preform P1... First position P2... Second position P3... Third position P4... Fourth position

Claims

1. A method for manufacturing a filament, comprising: a step of pulling the filament along its axial direction; a step of measuring the width of the filament at a first position in the axial direction and a second position in the axial direction; and a step of determining twist of the filament, wherein a first width direction of the filament measured at the first position and a second width direction of the filament measured at the second position are parallel to each other, and in the determining step, it is determined that twist has occurred in the filament if a first change in width of the filament at the first position and a second change in width of the filament at the second position are different from each other.

2. A method for manufacturing a filament, comprising: a step of pulling the filament along its axial direction; a step of measuring the width of the filament at a first position in the axial direction and a second position in the axial direction; and a step of determining twist of the filament, wherein a first width direction of the width of the filament measured at the first position and a second width direction of the width of the filament measured at the second position are parallel to each other, and in the determining step, it is determined that no twist has occurred in the filament if a first change in the width of the filament at the first position and a second change in the width of the filament at the second position match each other.

3. The method for manufacturing a filament according to claim 1, wherein in the measuring step, the width of the filament is measured at a third position in the axial direction and a fourth position in the axial direction, respectively; a third width direction of the width of the filament measured at the third position and a fourth width direction of the width of the filament measured at the fourth position are parallel to each other; and in the determining step, it is determined that twisting of the filament has occurred if the first change over time and the second change over time are different from each other and the third change over time of the width of the filament at the third position and the fourth change over time of the width of the filament at the fourth position are different from each other.

4. The method for manufacturing a filament according to claim 1 or claim 3, further comprising a step of eliminating the twist in the filament if it is determined in the determining step that twisting has occurred in the filament.

5. A method for manufacturing a filament according to any one of claims 1 to 4, wherein in the measuring step, the width of the filament is determined based on an image of the filament taken by a camera.

6. A filament manufacturing device comprising: a traction mechanism that traction the filament along its axial direction; a first measuring device that is provided at a first position in the axial direction and that measures the width of the filament; and a second measuring device that is provided at a second position in the axial direction and that measures the width of the filament, wherein a first width direction of the width of the filament measured at the first position and a second width direction of the width of the filament measured at the second position are parallel to each other.

Images