Apparatus for manufacturing optical fiber

Abstract

To provide an apparatus for manufacturing an optical fiber, capable of preventing a drawn optical fiber from contacting the optical fiber introduction part of a cooling pipe in a cooling device and breaking.SOLUTION: An apparatus 1A for manufacturing an optical fiber includes: a heating furnace 3 for heating an optical fiber preform; and a cooling device 4 for cooling an optical fiber F drawn from the optical fiber preform G1. The cooling device 4 includes: a cooling pipe 11 for traveling the optical fiber F in the inside; and a fiber breakage prevention contact member 13 installed so as to surround an optical fiber F introduction part 12 in the cooling pipe 11 and for preventing the optical fiber F passing through the inside of the cooling pipe 11 from breaking. The inner diameter of the contact member 13 is smaller than that of the cooling pipe 11.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an optical fiber manufacturing apparatus. [Background technology]

[0002] Patent Document 1 describes an optical fiber manufacturing device that is equipped with a control unit that can suppress shaking of the drawing tower during an earthquake. Patent Document 2 describes an optical fiber drawing and manufacturing apparatus that includes a cooling device that can cool the drawn glass fiber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-178633 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-168245 Summary of the Invention [Problem to be solved by the invention]

[0004] Some optical fiber manufacturing devices include a tower for suspending the optical fiber preform to be drawn, which has a heating furnace for heating the optical fiber preform and a cooling device for cooling the drawn optical fiber. In such optical fiber manufacturing equipment, when the tower vibrates due to an earthquake, for example, the drawn optical fiber may vibrate, causing the optical fiber to come into contact with the optical fiber entry portion of the cooling pipe in the cooling device, which may result in the optical fiber breaking.

[0005] An object of the present disclosure is to provide an optical fiber manufacturing apparatus that can prevent the drawn optical fiber from coming into contact with a cooling device and breaking. [Means for solving the problem]

[0006] An optical fiber manufacturing apparatus according to one aspect of the present disclosure includes: a heating furnace for heating the optical fiber preform; a cooling device for cooling the optical fiber drawn from the optical fiber preform; and The cooling device is a cooling pipe through which the optical fiber runs; a contact member for preventing breakage, which is installed so as to surround an entrance portion of the optical fiber in the cooling pipe and prevents breakage of the optical fiber passing through the inside of the cooling pipe; and The inner diameter of the contact member is smaller than the inner diameter of the cooling pipe. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to prevent the drawn optical fiber from coming into contact with the cooling device and breaking. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating a configuration of an optical fiber manufacturing apparatus according to a first embodiment of the present disclosure. [Figure 2] 1 is a perspective view showing an upper portion of a cooling pipe and a contact member in an optical fiber manufacturing apparatus. FIG. [Figure 3] 3 is a vertical cross-sectional view of the cooling pipe and the contact member shown in FIG. 2. FIG. [Figure 4] FIG. 10 is a cross-sectional view showing a modified example of the contact member used in the first embodiment. [Figure 5] FIG. 10 is a perspective view showing an upper portion of a cooling pipe and a contact member in an optical fiber manufacturing apparatus according to a second embodiment of the present disclosure. [Figure 6] 6 is a vertical cross-sectional view of the cooling pipe and the contact member shown in FIG. 5. [Figure 7] FIG. 10 is a plan view showing an upper portion of a cooling pipe and a contact member in an optical fiber manufacturing apparatus according to a third embodiment of the present disclosure. [Figure 8] FIG. 8 is a front view of the cooling pipe and the contact member shown in FIG. [Figure 9] 9 is a vertical cross-sectional view of the cooling pipe and the contact member shown in FIG. 8. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Description of Embodiments of the Present Disclosure) First, embodiments of the present disclosure will be listed and described. An optical fiber manufacturing apparatus according to one aspect of the present disclosure includes: (1) a heating furnace for heating an optical fiber preform; a cooling device for cooling the optical fiber drawn from the optical fiber preform; and The cooling device is a cooling pipe through which the optical fiber runs; a contact member for preventing breakage, which is installed so as to surround an entrance portion of the optical fiber in the cooling pipe and prevents breakage of the optical fiber passing through the inside of the cooling pipe; and The inner diameter of the contact member is smaller than the inner diameter of the cooling pipe. According to the optical fiber manufacturing apparatus, even if the drawn optical fiber vibrates when the optical fiber manufacturing apparatus vibrates due to an earthquake or the like, the optical fiber comes into contact with the contact member for preventing breakage at the entrance of the cooling tube. Therefore, the optical fiber manufacturing apparatus can prevent the drawn optical fiber from coming into contact with the entrance of the optical fiber in the cooling device and breaking.

[0010] (2) In the above (1), the surface of the contact member facing the position where the optical fiber passes through may have a surface roughness Ra of 1 μm or less at a portion closest to the center of the cooling pipe. According to the optical fiber manufacturing apparatus, the roughness Ra of the surface of the contact member for preventing breakage that may come into contact with the optical fiber is 1 μm or less, so that friction between the surface that comes into contact with the optical fiber and the optical fiber is low, thereby further preventing breakage of the optical fiber.

[0011] (3) In the above (1) or (2), the cooling pipe and the contact member may have a half-split structure that can be opened and closed. According to the optical fiber manufacturing apparatus, the tip of the optical fiber at the start of drawing can be passed through with the cooling pipe and contact member of the half-split structure open, and then the cooling pipe and contact member can be closed to perform drawing. Furthermore, keeping the half-split structure open facilitates maintenance of the optical fiber manufacturing apparatus. Therefore, the optical fiber manufacturing apparatus is easy to handle during optical fiber manufacturing.

[0012] (4) In any one of the above (1) to (3), the cross-sectional shape of the contact member in a plane including the central axis of the cooling pipe may be chamfered. According to the optical fiber manufacturing apparatus, the portion of the optical fiber that comes into contact when the optical fiber swings is chamfered, so that the optical fiber comes into surface contact with the contact member, and therefore the risk of the optical fiber breaking is reduced compared to when the contact member is not chamfered.

[0013] (5) In the above (4), the contact member is A flat surface parallel to the central axis may be present in a portion of the contact member other than the chamfered portion where the inner diameter is smallest. According to the optical fiber manufacturing apparatus, the part of the contact member other than the chamfered part that has the smallest inner diameter has a flat surface parallel to the optical fiber running axis. When the drawn optical fiber vibrates, the optical fiber comes into surface contact with this flat surface, reducing contact stress. Therefore, there is little risk of the optical fiber breaking.

[0014] (6) In the above (1) or (2), the contact member includes a plurality of rollers each having a circumferential groove with a U-shape, The rollers may be arranged such that their rotation axes are perpendicular to the central axis of the cooling pipe and their circumferential grooves face each other relative to the optical fiber through which it runs. According to the optical fiber manufacturing apparatus, when the drawn optical fiber vibrates, the surface that may come into contact with the drawn optical fiber is the circumferential groove of the U-shaped roller. Because the drawn optical fiber travels at high speed, even if the optical fiber comes into contact with the circumferential groove of the roller, the roller rotates, reducing friction with the optical fiber. Furthermore, because the circumferential groove of the roller is U-shaped, i.e., the surface that comes into contact with the optical fiber has no corners, there is little risk of the optical fiber breaking when it hits the circumferential groove of the roller.

[0015] (Details of the embodiments of the present disclosure) A specific example of an optical fiber manufacturing apparatus according to an embodiment of the present disclosure will be described below with reference to the drawings. It should be noted that the present invention is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0016] (First embodiment) An optical fiber manufacturing apparatus 1A according to a first embodiment will be described with reference to FIGS. Fig. 1 is a configuration diagram of an optical fiber manufacturing apparatus 1A. As shown in Fig. 1, the optical fiber manufacturing apparatus 1 is an apparatus for drawing an optical fiber preform G1. The optical fiber manufacturing apparatus 1A includes a tower 2, a heating furnace 3, a cooling device 4, a resin coating device 5, a guide roller 6, a winding device 7, and a gripping unit 9.

[0017] The tower 2 is erected in a substantially vertical direction on the ground 10 to hang the optical fiber preform G1. The holding unit 9 is provided at the top of the tower 2 and is movable in the vertical direction. The holding unit 9 holds a support rod provided at the top of the optical fiber preform G1 and descends to send the optical fiber preform G1 into the heating furnace 3.

[0018] The heating furnace 3 is provided below the holding part 9 in the tower 2, and has a heater 3a for heating the optical fiber preform G1. The optical fiber preform G1 sent into the heating furnace 3 is heated and melted at its lower end, and is stretched downward to reduce its diameter, thereby forming the optical fiber F in a glass body.

[0019] The cooling device 4 is provided below the heating furnace 3. The cooling device 4 has a cooling pipe 11 through which the optical fiber F runs. The cooling pipe 11 has a long cylindrical shape along the running direction of the optical fiber F, and a circular insertion hole 14 (see Figure 2) is formed in the center inside the cooling pipe 11, through which the optical fiber F runs in the longitudinal direction. The running axis of the optical fiber F usually coincides with the central axis of the insertion hole 14, which is the central axis of the cooling pipe 11. A cooling gas for cooling the optical fiber F is sent into the insertion hole 14. By inserting the optical fiber F into the insertion hole 14, the optical fiber F can be cooled to an appropriate temperature after drawing.

[0020] The resin coating device 5 is provided below the cooling device 4. The resin coating device 5 is configured to coat the outer periphery of the optical fiber F with resin. The resin-coated optical fiber F is guided by a guide roller 6 and sent to the winding device 7, where it is wound around a winding bobbin 7a.

[0021] Next, the upper structure of the cooling device 4 will be described in detail with reference to FIGS. Fig. 2 is a perspective view showing the cooling pipe 11 and the contact member 13 attached to the inlet portion 12 of the cooling pipe 11. Fig. 3 is a vertical cross-sectional view of the cooling pipe 11 and the contact member 13 shown in Fig. 2.

[0022] As shown in Figures 2 and 3, a contact member 13 is provided in the inlet section 12, which is the entrance section where the optical fiber F enters, of the insertion hole 14 of the cooling pipe 11. The contact member 13 is provided so as to cover and surround the inlet section 12 of the optical fiber F in the cooling pipe 11. The contact member 13 is a member for preventing breakage, which prevents the optical fiber F from coming into contact with the inlet section 12 and prevents breakage of the optical fiber F passing through the cooling pipe 11. The contact member 13 is formed, for example, in a cylindrical shape with a short length in the central axis direction. The contact member 13 is configured so as to be attached, for example, by fitting it into the insertion hole 14 of the inlet section 12 from above the cooling pipe 11.

[0023] The contact member 13 is chamfered so that an inner circumferential surface 15, which is the surface facing the optical fiber F passing through the cooling pipe 11, has a shape without corners in the cross section of the contact member 13 in a plane including the central axis of the cooling pipe 11. For example, the inner circumferential surface 15 of the contact member 13 is chamfered so as to have a convex curved surface toward the central axis of the cooling pipe 11. The inner circumferential surface 15 of the contact member 13 is formed into a curved shape such that the diameter gradually decreases from the upper end to the central portion 16 in the vertical direction along the central axis of the cooling pipe 11, the inner diameter is smallest at the central portion 16, and the diameter gradually increases from the central portion 16 to the lower end.

[0024] The inner circumferential surface 15 of the contact member 13 is formed, for example, so that the longitudinal cross section has a circular arc shape or an elliptical arc shape. Furthermore, as in the modified contact member 13a shown in Fig. 4, the inner circumferential surface 15a may have a flat surface 17 that is parallel to a plane including the central axis of the cooling pipe 11 at a portion (central portion 16) where the inner diameter of the contact member 13a is smallest other than the chamfered portion. The inner diameter of the contact member 13 is formed to be smaller than the inner diameter of the cooling pipe 11. The inner diameter of the contact member 13 is preferably about 60% of the inner diameter of the cooling pipe 11.

[0025] The contact member 13 has a surface roughness Ra of 1 μm or less on the inner circumferential surface 15, at least at the surface closest to the central axis of the cooling pipe 11. The contact member 13 is made of a material that has excellent heat resistance, wear resistance, etc. For example, the contact member 13 is made of ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4), or stainless steel (SUS). The contact member 13 may also be made of a metal surface that has been coated. Examples of coatings include CDC-ZAC (registered trademark) coating, which is a composite ceramic film; diamond-like carbon coating, which is a thin film made of a material whose main component is carbon and has both diamond and graphite bonds; and electroless nickel plating.

[0026] As described above, the optical fiber manufacturing apparatus 1A of the first embodiment is provided with the contact member 13 so as to surround the entrance portion 12 of the cooling pipe 11. The contact member 13 is also provided with a curved, chamfered inner peripheral surface 15. For this reason, if the optical fiber manufacturing apparatus 1A vibrates due to an earthquake or the like and the drawn optical fiber F swings, the optical fiber F may come into contact with the inner peripheral surface 15 of the contact member 13 at the entrance portion 12 of the cooling pipe 11, for example, as shown by arrow A in FIG.

[0027] The drawn optical fiber F has a thin cylindrical shape with a diameter of, for example, about 125 μm. As described above, the shape of the inner circumferential surface 15 of the contact member 13 is a curved surface that is convex toward the center of the cooling pipe 11. Furthermore, the running direction of the optical fiber F and the circumferential direction of the inner circumferential surface 15 of the contact member 13 intersect with each other. When two objects having such shapes come into contact with each other, the contact stress generated at the contact point can be reduced by increasing the contact area between the two objects.

[0028] Therefore, by making the longitudinal cross section of the inner peripheral surface 15 of the contact member 13 into a circular arc shape or an elliptical arc shape, the contact area caused by elastic deformation between the optical fiber F and the inner peripheral surface 15 of the contact member 13 can be increased, and contact stress can be reduced. Therefore, according to the optical fiber manufacturing apparatus 1A, when the drawn optical fiber F is shaken by an earthquake or the like, the optical fiber F is brought into contact with the contact member 13 rather than the incoming line portion 12, thereby preventing the optical fiber F from coming into contact with the incoming line portion 12 of the cooling pipe 11 in the cooling device 4 and breaking.

[0029] 4, the optical fiber manufacturing apparatus 1A can form a flat surface 17 parallel to a plane including the central axis of the cooling pipe 11 in the portion of the contact member 13a other than the chamfered portion where the inner diameter is smallest. Therefore, when the drawn optical fiber F vibrates, the optical fiber F comes into contact with this flat surface 17 of the contact member 13a, and the contact area between the optical fiber F and the contact member 13a can be further increased. This can further reduce the contact stress generated at the contact portion between the optical fiber F and the contact member 13a, and further suppress breakage of the optical fiber F.

[0030] Furthermore, the optical fiber manufacturing apparatus 1A is configured so that the surface roughness of the portion with which the drawn optical fiber F is likely to come into contact, i.e., the roughness Ra of the surface (e.g., central portion 16, etc.) closest to the central axis of the cooling pipe 11 on the inner circumferential surface 15 of the contact member 13, is 1 μm or less. This makes it possible to reduce friction between the optical fiber F and the inner circumferential surface 15 with which the optical fiber F comes into contact. Therefore, breakage of the optical fiber F can be further suppressed.

[0031] Second Embodiment An optical fiber manufacturing apparatus 1B according to a second embodiment will be described with reference to Figures 5, 6, and 1. Note that the same components as those of the optical fiber manufacturing apparatus 1A according to the first embodiment will be assigned the same reference numerals, and descriptions thereof will be omitted.

[0032] Fig. 5 is a perspective view showing the upper part of cooling pipe 21 provided in optical fiber manufacturing apparatus 1B and contact member 23 attached so as to surround inlet portion 22 of cooling pipe 21. The upper view in Fig. 5 shows a state in which half-split cooling pipes 21A and 21B are integrated. The lower view in Fig. 5 shows a state in which half-split cooling pipes 21A and 21B are separated. Fig. 6 is a cross-sectional view taken along the central axis direction of cooling pipe 21 at the upper part of cooling pipe 21 and contact member 23 shown in Fig. 5.

[0033] As shown in FIGS. 5 and 6, in the optical fiber manufacturing apparatus 1B, the cooling pipe 21 (21A, 21B) of the cooling device 4 has a split-halve structure that can be opened and closed by dividing it into two halves in a direction away from the central axis of the cooling pipe 21. The cooling device 4 is usually used in an integrated state by being joined together during drawing (see the upper diagram in FIG. 5). The cooling device 4 has a circular insertion hole 24 formed in the center of the closed cooling pipes 21A, 21B, through which the optical fiber F is passed in the longitudinal direction. The cross-sectional shape of each of the insertion holes 24 formed in the cooling pipes 21A, 21B is semicircular. Similar to the insertion hole 14 in the first embodiment, a cooling gas is fed into this insertion hole 24, and the optical fiber F inserted into the insertion hole 24 is cooled.

[0034] Contact members 23A and 23B for preventing breakage of the optical fiber F are provided at the inlet portions 22A and 22B of the cooling pipes 21A and 21B, respectively. The contact members 23A and 23B are made of, for example, rectangular members, and are attached to the top surfaces of the cooling pipes 21A and 21B, respectively, with screws. The contact members 23A and 23B have a split-half structure that can be opened and closed together with the cooling pipes 21A and 21B, and semicircular recesses 28A and 28B are formed in the contact members 23A and 23B so as to correspond to the insertion holes 24 of the cooling pipes 21A and 21B, respectively.

[0035] The contact members 23A, 23B are attached to the upper surfaces of the cooling pipes 21A, 21B so that the side surfaces on which the recesses 28A, 28B are formed slightly protrude beyond the surfaces of the cooling pipes 21A, 21B on which the semicircular insertion holes 24 are formed. The contact members 23A, 23B are attached to the upper surfaces of the cooling pipes 21A, 21B so that their positions in the running direction of the optical fiber F are staggered. In this example, the contact member 23B is attached via a base 27 at a position higher than the contact member 23A. Therefore, when the cooling pipes 21A, 21B are closed, the protruding portions 29A, 29B of the contact members 23A, 23B are vertically offset and overlap each other when closed. As a result, when the cooling pipes 21A, 21B in the closed state are observed from above, the optical fiber F inserted into the insertion hole 24 is surrounded without any gaps by the recesses 28A, 28B of the contact members 23A, 23B.

[0036] In the contact members 23A, 23B, the surfaces of the recesses 28A, 28B facing the inserted optical fiber F become the inner circumferential surfaces 25 of the contact members 23A, 23B. The configuration etc. of the inner circumferential surface 25 is similar to that of the inner circumferential surfaces 15, 15a of the contact members 13, 13a in the first embodiment.

[0037] According to the optical fiber manufacturing apparatus 1B of the second embodiment, the contact member 23 is provided so as to surround the optical fiber F passing through the cooling pipe 21. Therefore, similar to the optical fiber manufacturing apparatus 1A of the first embodiment, it is possible to prevent the drawn optical fiber F from coming into contact with the inlet portion 22 of the cooling pipe 21 in the cooling device 4 and breaking.

[0038] Furthermore, with the optical fiber manufacturing apparatus 1B, the tip of the drawn optical fiber F can be passed through the insertion hole 24 of the cooling pipe 21 with the halved cooling pipe 21 and the contact member 23 open, and then the cooling pipe 21 and the contact member 23 can be closed to perform drawing. Furthermore, with the halved structure open, maintenance of the optical fiber manufacturing apparatus 1B can be performed. Therefore, the optical fiber manufacturing apparatus 1B is easy to handle during optical fiber manufacturing.

[0039] (Third embodiment) An optical fiber manufacturing apparatus 1C according to a third embodiment will be described with reference to Figures 7 to 9 and Figure 1. Note that the same components as those of the optical fiber manufacturing apparatus 1A according to the first embodiment will be assigned the same reference numerals, and descriptions thereof will be omitted.

[0040] Fig. 7 is a plan view of the upper part of cooling pipe 31 provided in optical fiber manufacturing apparatus 1C and contact member 33 attached so as to surround entrance portion 32 of cooling pipe 31, as viewed from above. Fig. 8 is a front view of the upper part of cooling pipe 31 and contact member 33 shown in Fig. 7. Fig. 9 is a cross-sectional view of the upper part of cooling pipe 31 and contact member 33 shown in Fig. 7, taken along the central axis of cooling pipe 31.

[0041] As shown in Figures 7 and 8, the contact member 33 in the optical fiber manufacturing apparatus 1C is composed of, for example, four rollers 33A to 33D each having a U-shaped circumferential groove 37 (37A to 37D). The rollers 33A and 33D are rotatably attached to a support 42A extending vertically upward from the top surface of a base 41A via rotation shafts 38A and 38D, respectively. The rollers 33B and 33C are rotatably attached to a support 42B extending vertically upward from the top surface of a base 41B via rotation shafts 38B and 38C, respectively. The bases 41A and 41B are attached to the top surface of the cooling pipe 31 with screws, respectively. The rotation shafts 38A to 38D are attached to the support 42A and 42B so as to be perpendicular to the central axis of the cooling pipe 31.

[0042] The rollers 33A and 33B are arranged such that their respective circumferential grooves 37A and 37B face each other with respect to the running optical fiber F. The rollers 33C and 33D are arranged such that their respective circumferential grooves 37C and 37D face each other with respect to the running optical fiber F. The circumferential grooves 37A to 37D are formed so that the central angle θ with respect to the central axis of the insertion hole 34 in the cooling pipe 31 is 90 degrees or greater. The rollers 33A and 33B and the rollers 33C and 33D are attached to the supports 42A and 42B, respectively, so that their positions in the running direction of the optical fiber F are staggered. In this example, the rollers 33A and 33B are attached at a higher position than the rollers 33C and 33D. As a result, when the cooling pipe 31 is observed from above, the optical fiber F inserted into the insertion hole 34 is tightly surrounded by the circumferential grooves 37A to 37D of the rollers 33A to 33D.

[0043] In the contact member 33, the surface of the circumferential groove 37 (37A to 37D) that faces the inserted optical fiber F becomes the inner circumferential surface 35 (35A to 35D) of the contact member 33 (rollers 33A to 33D). The material of the contact member 33 and the surface roughness of the inner circumferential surface 35 are the same as those of the contact member 13 in the first embodiment. However, while the inner circumferential surface 15 of the contact member 13 in the first embodiment is a convex curved surface facing the central axis of the cooling pipe 11, the inner circumferential surface 35 of the contact member 33 is a concave curved surface facing the central axis of the cooling pipe 31.

[0044] According to the optical fiber manufacturing apparatus 1C of the third embodiment, the contact member 33 is provided to surround the optical fiber F passing through the cooling tube 31. The contact member 33 is provided with a curved inner circumferential surface 35 (circumferential groove 37). Therefore, if the optical fiber manufacturing apparatus 1C vibrates due to an earthquake or the like and the drawn optical fiber F swings, the optical fiber F may come into contact with the inner circumferential surface 35D of the roller 33D at the entrance portion 32 of the cooling tube 31, for example, as shown by arrow A in FIG. 9. Note that FIG. 9 shows the lower rollers 33C and 33D among the rollers 33A to 33D. The optical fiber F being drawn travels at high speed, and when the optical fiber F comes into contact with the inner circumferential surface 35D of the roller 33D, friction with the optical fiber F causes the roller 33D to rotate in the direction of arrow B. This rotation of the roller 33D reduces friction when the optical fiber F comes into contact with the inner circumferential surface 35D. Furthermore, the inner peripheral surface 35D of the roller 33D is curved and has no corners, which further reduces friction when the optical fiber F comes into contact with the inner peripheral surface 35D. Therefore, similar to the optical fiber manufacturing apparatus 1A of the first embodiment, it is possible to prevent the drawn optical fiber F from coming into contact with the inlet portion 32 of the cooling pipe 31 in the cooling device 4 and breaking.

[0045] Example 1 The optical fiber F was manufactured by drawing an optical fiber preform G1 using the optical fiber manufacturing apparatus according to this embodiment, and the frequency of fiber breakage during drawing during an earthquake was evaluated. The evaluation results are shown in Table 1.

[0046] [Table 1]

[0047] In Table 1, Sample No. 1 is an example for comparison in which an optical fiber manufacturing apparatus without a contact member was used. Sample No. 2 is an example in which an optical fiber manufacturing apparatus 1A of the first embodiment equipped with contact member 13 was used. Sample No. 3 is an example in which an optical fiber manufacturing apparatus 1B of the second embodiment equipped with contact member 23 was used. Sample No. 4 is an example in which an optical fiber manufacturing apparatus 1C of the third embodiment equipped with contact member 33 was used.

[0048] As shown in Table 1, when an earthquake of seismic intensity 0 to 2 occurred, the frequency of drawing breakage in sample No. 1, which was not equipped with a contact member (no breakage prevention measures were implemented), was 90%. In contrast, the frequency of drawing breakage in samples Nos. 2 to 4, which were equipped with contact members, was 30%. Therefore, even when an earthquake of seismic intensity 0 to 2 occurs, the frequency of drawing breakage can be significantly reduced by providing a contact member in the optical fiber manufacturing equipment. Furthermore, even when an earthquake of seismic intensity 3 or higher occurs, providing a contact member has the effect of reducing the frequency of drawing breakage.

[0049] Example 2 In the optical fiber manufacturing apparatus 1A according to the first embodiment (or the optical fiber manufacturing apparatus 1B according to the second embodiment), the frequency of breakage and the lifespan were evaluated for a number of samples (Nos. 1 to 6) of contact members with different surface roughness, inner diameter, longitudinal cross-sectional shape, and material. The evaluation results are shown in Table 2.

[0050] [Table 2]

[0051] In Table 2, surface roughness indicates the roughness of the surface closest to the center of the cooling pipe on the inner surface of the contact member. Inner diameter indicates the ratio of the inner diameter of the contact member to the inner diameter of the cooling pipe. Longitudinal cross-sectional shape indicates the cross-sectional shape of the inner surface. Wire breakage frequency indicates the frequency of wire breakage when an earthquake with a seismic intensity of 0 to 2 occurs. Lifespan indicates the period until the effect of preventing wire breakage is reduced due to the surface roughness of the contact member.

[0052] According to the evaluation results in Table 2, as can be seen from a comparison between Samples No. 1 and 2, by increasing the surface roughness Ra from Ra = 1.6 μm to 0.2 μm, it is possible to reduce the friction between the optical fiber F and the inner surface, and to reduce the frequency of fiber breakage during drawing from 60% to 50%.

[0053] As can be seen from a comparison between Samples No. 2 and 3, by reducing the inner diameter from 90% to 60%, when the optical fiber F vibrates due to an earthquake or the like, the optical fiber F can be brought into contact with the contact member even when the vibration is small, and the frequency of fiber drawing breakage can be reduced from 50% to 40%.

[0054] As can be seen from a comparison of Samples No. 3 and 4, by changing the cross-sectional shape from a semicircle to a semiellipse, the contact area generated by elastic deformation between the optical fiber F and the inner surface can be increased, and the frequency of fiber breakage during drawing can be reduced from 40% to 30%.

[0055] As can be seen from a comparison of samples Nos. 4, 5, and 6, when the longitudinal cross-sectional shape is semi-elliptical, the contact area between the optical fiber F and the inner surface can be increased, as described above, and the frequency of fiber breakage during drawing can be reduced to 30% regardless of whether the material of the contact member is stainless steel, silicon carbide, or silicon nitride.

[0056] As can be seen from a comparison of Sample No. 4 with Samples No. 5 and 6, by using ceramics such as silicon carbide or silicon nitride, which have excellent heat resistance and wear resistance, for the contact members, the lifespan can be extended to three years.

[0057] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to any number, position, shape, etc. that is suitable for implementing the present invention. For example, the cooling pipes 11 and 31 may have a half-split structure similar to the cooling pipe 21. [Explanation of symbols]

[0058] 1A, 1B, 1C: Optical fiber manufacturing equipment 2: Tower 3:Heating furnace 4: Cooling device 11,21(21A,21B),31: Cooling pipe 12, 22 (22A, 22B), 32: Incoming line 13, 23 (23A, 23B), 33: Contact members 14, 24, 34: Through holes 15,25,35(35A~35D): Inner surface 28A, 28B: recess 33A~33D: Roller 37(37A~37D): Circumferential groove F: Optical fiber G1: Optical fiber base material

Claims

1. a heating furnace for heating the optical fiber preform; a cooling device for cooling the optical fiber drawn from the optical fiber preform; and The cooling device is a cooling pipe through which the optical fiber runs; a contact member for preventing breakage, which is installed so as to surround an entrance portion of the optical fiber in the cooling pipe and prevents breakage of the optical fiber passing through the inside of the cooling pipe; and the inner diameter of the contact member is smaller than the inner diameter of the cooling pipe; Optical fiber manufacturing equipment.

2. the contact member has a surface facing a position where the optical fiber passes, the surface closest to the central axis of the cooling pipe having a roughness Ra of 1 μm or less; 2. The optical fiber manufacturing apparatus according to claim 1.

3. The cooling pipe and the contact member have a half-split structure that can be opened and closed.

3. The optical fiber manufacturing apparatus according to claim 1.

4. The cross-sectional shape of the contact member in a plane including the central axis of the cooling pipe is 3. The optical fiber manufacturing apparatus according to claim 1, wherein the optical fiber has a chamfered shape.

5. The contact member is a flat surface parallel to the central axis is present in a portion of the contact member with the smallest inner diameter other than the chamfered portion; 5. The optical fiber manufacturing apparatus according to claim 4.

6. the contact member includes a plurality of rollers each having a U-shaped circumferential groove; The plurality of rollers are arranged such that the roller rotation axes are perpendicular to the central axis of the cooling pipe, and the circumferential grooves of each roller are opposed to the optical fiber running therethrough.

3. The optical fiber manufacturing apparatus according to claim 1.

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