Optical fiber manufacturing device

Abstract

In this optical fiber manufacturing device, formed in a cooling device are: an insertion path through which a glass fiber advancing in a first direction can pass; and a cooling gas supply port through which a cooling gas can be supplied to the insertion path. In the interior of the recovery jig, formed are: a recovery space that communicates with the insertion passage; a cooling gas recovery port that is formed so as to communicate with the recovery space and that is capable of discharging the cooling gas; and an outlet port through which the glass fiber can be drawn out from the recovery space in the first direction. The inner surface of the cooling device having the insertion passage formed therein is cooled as a result of a refrigerant flowing through the interior of the cooling device, and the refrigerant does not flow through the recovery jig.

Description

Optical Fiber Manufacturing Apparatus

[0001] This application claims priority based on Japanese Patent Application No. 2024-198282 filed on November 13, 2024, and incorporates all the descriptions contained in the said application. This disclosure relates to an optical fiber manufacturing apparatus.

[0002] Patent Document 1 discloses cooling a glass fiber as a pre-process of the coating process of an optical fiber. When cooling the glass fiber, introducing a cooling gas into a cooling device is disclosed.

[0003] Japanese Patent Application Laid-Open No. 2005-119901

[0004] An optical fiber manufacturing apparatus according to an aspect of this disclosure includes a cooling device that cools a glass fiber drawn from a heated and softened glass base material and traveling in a first direction, and a recovery jig externally attached to the cooling device. The cooling device is formed with an insertion passage through which the glass fiber traveling in the first direction can pass, and a cooling gas supply port for supplying a cooling gas to the insertion passage. Inside the recovery jig, a recovery space communicating with the insertion passage is formed, and a cooling gas recovery port formed so as to communicate with the recovery space for discharging the cooling gas, and an outlet through which the glass fiber can exit from the recovery space in the first direction are formed. The inner surface of the cooling device forming the insertion passage is cooled by a refrigerant flowing inside the cooling device, and no refrigerant flows through the recovery jig.

[0005] FIG. 1 is a diagram illustrating an optical fiber manufacturing apparatus. FIG. 2 is a diagram illustrating a predetermined detection range detected by a sensor. FIG. 3 is an enlarged view of part III in FIG. 2. FIG. 4 is a perspective view of the insertion passage of the third cooling pipe, the incoming line space, and the sudden expansion space in the recovery jig for the manufacturing apparatus according to a modified example. FIG. 5 is a graph showing the outflow path of helium and the flow rate of the outflowing helium in the manufacturing apparatus. FIG. 6 is a graph showing the recovery rate of helium when the inner diameter of the outlet is changed.

[0006] Since cooling gases are generally expensive, it is desirable to be able to recover the cooling gas used to cool the glass fibers. Furthermore, it is desirable that the recovery of the cooling gas be carried out in a way that does not affect the control of the outer diameter of the glass fibers.

[0007] According to this disclosure, an apparatus for manufacturing optical fibers that stabilizes the coating diameter of the optical fiber is provided.

[0008] Embodiments of the present disclosure will be listed and described first. (1) An optical fiber manufacturing apparatus according to one aspect of the present disclosure comprises a cooling device for cooling a glass fiber drawn from a heated and softened glass matrix and traveling in a first direction, and a recovery jig provided externally attached to the cooling device, wherein the cooling device has an insertion passage through which the glass fiber traveling in the first direction can pass, and a cooling gas supply port for supplying cooling gas to the insertion passage, the recovery jig has a recovery space communicating with the insertion passage, a cooling gas recovery port formed to communicate with the recovery space and capable of discharging the cooling gas, and an outlet for which the glass fiber can exit the recovery space in the first direction, the inner surface of the cooling device forming the insertion passage is cooled by a refrigerant flowing inside the cooling device, and no refrigerant flows through the recovery jig.

[0009] According to the optical fiber manufacturing apparatus with the above configuration, the recovery jig allows for the recovery of the cooling gas used in the cooling device. Furthermore, since the recovery jig is not cooled, the temperature of the glass fiber exiting the output port remains stable regardless of whether or not the cooling gas is recovered. This makes it easier to control the coating diameter of the glass fiber, resulting in a stable coating diameter for the optical fiber.

[0010] (2) In the optical fiber manufacturing apparatus according to (1) above, the inner diameter of the output port may be 8 mm or less.

[0011] With the above configuration, the inner diameter of the wire outlet is 8 mm or less, making it difficult for the cooling gas to be discharged from the wire outlet of the recovery jig. As a result, the amount of cooling gas recovered by the recovery jig increases.

[0012] (3) In the optical fiber manufacturing apparatus according to (1) or (2) above, the recovery space includes an entry space which is a space in communication with the insertion passage, and a rapidly expanding space which is located in the first direction relative to the entry space and is in communication with the entry space, and the cross-sectional area in a section perpendicular to the first direction is discontinuously larger than that of the entry space, and the cooling gas recovery port may be formed to communicate with the rapidly expanding space.

[0013] According to the above configuration, the recovery space includes an entry space and a rapidly expanding space. Therefore, cooling gas entering the rapidly expanding space from the entry space is decelerated and tends to accumulate in the rapidly expanding section. In this state, the cooling gas is recovered from the cooling gas recovery port, thus improving the cooling gas recovery rate.

[0014] (4) In the optical fiber manufacturing apparatus according to (3) above, the rapidly expanding space is a space formed along a second direction perpendicular to the first direction and a third direction perpendicular to the first direction and intersecting the second direction, wherein the dimension of the rapidly expanding space in the second direction is five times or more the minimum dimension of the insertion passage in the second direction, and the dimension of the rapidly expanding space in the third direction may be 1.5 times or less the minimum dimension of the insertion passage in the third direction.

[0015] With the above configuration, increasing the second dimension of the rapidly expanding space increases the distance between the cooling gas recovery port and the moving optical fiber, thereby reducing the flow velocity of the cooling gas in the rapidly expanding space. Furthermore, because the third dimension of the rapidly expanding space is small, turbulence is less likely to occur inside the recovery jig. This makes it less likely for the moving optical fiber to wobble.

[0016] (5) In the optical fiber manufacturing apparatus according to any of (1) to (4) above, the first direction is a direction directed vertically downward, and the recovery jig may be provided at the bottom of the cooling device.

[0017] According to the above configuration, since the recovery jig is provided in the cooling device in the direction of vertical downward, which is the direction of glass fiber propagation, the cooling gas accelerated as the glass fiber moves can be recovered. This improves the efficiency of cooling gas recovery.

[0018] (6) In an optical fiber manufacturing apparatus according to any of (1) to (5) above, the cooling gas is helium (He) and hydrogen (H ２ ) may include any of the following.

[0019] According to the optical fiber manufacturing apparatus with the above configuration, relatively expensive helium (He) and hydrogen (H) are used. ２ The optical fiber coating diameter can be stabilized while recovering a cooling gas containing one of the following:

[0020] (Details of Embodiments of the Disclosure) Specific examples of optical fiber manufacturing apparatus according to embodiments of the Disclosure are described below with reference to the drawings. However, the Disclosure is not limited to these examples and is intended to include all modifications within the meaning and scope of the claims, as indicated by the claims.

[0021] In the attached drawing, arrow F indicates the front direction of the illustrated structure. Arrow B indicates the rear direction of the illustrated structure. Arrow U indicates the upward direction of the illustrated structure. Arrow D indicates the downward direction of the illustrated structure. Arrow R indicates the right direction of the illustrated structure. Arrow L indicates the left direction of the illustrated structure. These directional expressions are used for explanatory purposes only and do not limit the actual orientation or direction of the illustrated structure in use.

[0022] Figure 1 illustrates a manufacturing apparatus 1 for optical fiber G2. The optical fiber manufacturing apparatus 1 manufactures glass fibers G1 by drawing a glass base material G0, and then manufactures optical fiber G2 by coating the glass fibers G1 with resin. As illustrated in Figure 1, the manufacturing apparatus 1 is equipped with a cooling device 12. The manufacturing apparatus 1 may also be equipped with at least one of the following: a heating furnace 11, a glass outer diameter measuring unit 13, a resin coating unit 14, a resin curing unit 15, an outer diameter measuring unit 16, a direct-down roller 17, a capstan 18, and a winding roller 19.

[0023] The heating furnace 11 heats the glass base material G0 with the heater 11a. The heated and softened glass is stretched downwards to become glass fibers G1.

[0024] The cooling device 12 is located below the heating furnace 11. The cooling device 12 can cool the heated glass fiber G1. The glass fiber G1 exiting the heating furnace 11 has a temperature of approximately 700°C when it enters the cooling device 12. The cooling device 12 cools the glass fiber G1 so that its temperature is approximately 70°C when it exits the cooling device 12.

[0025] The glass outer diameter measuring unit 13 is located below the cooling device 12. The glass outer diameter measuring unit 13 can measure the outer diameter of the glass fiber G1. For example, a laser-type outer diameter measuring instrument may be used as the glass outer diameter measuring unit 13.

[0026] The resin coating section 14 is located below the glass outer diameter measuring section 13. The resin coating section 14 applies resin to the cooled glass fiber G1. The resin coating section 14 includes a die 141 that stores the resin and is formed so that the glass fiber G1 can pass through its interior. As the resin is supplied to the die 141, the glass fiber G1 passes through the inside of the die 141, thereby coating the outer surface of the glass fiber G1 with resin. The resin supplied to the resin coating section 14 may be, for example, an ultraviolet (UV) curing resin that hardens when irradiated with ultraviolet light.

[0027] The resin curing unit 15 is located below the resin coating unit 14. The resin curing unit 15 can cure the resin applied to the outer surface of the glass fiber G1 in the resin coating unit 14. For example, if the resin applied in the resin coating unit 14 is a UV-curable resin, the resin curing unit 15 is equipped with an ultraviolet lamp (not shown). The ultraviolet lamp can emit ultraviolet light. When the ultraviolet light emitted from the ultraviolet lamp irradiates the resin applied to the outer surface of the glass fiber G1, the resin applied to the outer surface of the glass fiber G1 hardens, and a resin layer is formed on the outer surface of the glass fiber G1. By forming a resin layer on the outer surface of the glass fiber G1, an optical fiber G2 is manufactured.

[0028] The outer diameter measuring unit 16 is located below the resin curing unit 15. The outer diameter measuring unit 16 can measure the outer diameter of the optical fiber G2. For example, a laser-type outer diameter measuring instrument may be used as the outer diameter measuring unit 16.

[0029] The thickness of the resin coating layer covered by the glass outer diameter measuring unit 13 and the outer diameter measuring unit 16 can be estimated. Based on the thickness of the coating layer, the manufacturing apparatus 1 performs feedback control on the temperature at which the glass fiber G1 exits the cooling device 12.

[0030] The lower roller 17 is positioned below the outer diameter measuring section 16. The lower roller 17 changes the direction in which the optical fiber G2 travels. In this embodiment, the optical fiber G2 upstream of the lower roller 17 travels downward, while the optical fiber G2 downstream of the lower roller 17 travels to the right and upward.

[0031] In this embodiment, the capstan 18 is located above and to the right of the lower roller 17. The capstan 18 comprises a capstan belt 181 and a capstan roller 182. The optical fiber G2 is sandwiched between the capstan belt 181 and the capstan roller 182 and pulled in. As a result, the optical fiber G2 is subjected to a predetermined tension by the capstan 18 and continues to move downstream. The optical fiber G2 that has moved downstream of the capstan 18 is wound onto the winding roller 19.

[0032] Figure 2 illustrates a longitudinal cross-section of the cooling device 12. As illustrated in Figure 2, the cooling device 12 comprises a first cooling pipe 121, a second cooling pipe 122, and a third cooling pipe 123. The first cooling pipe 121, the second cooling pipe 122, and the third cooling pipe 123 are connected in this order from top to bottom.

[0033] The first cooling tube 121, the second cooling tube 122, and the third cooling tube 123 each have an insertion passage P that penetrates them along the vertical direction. The first cooling tube 121, the second cooling tube 122, and the third cooling tube 123 are connected so that their respective insertion passages P are in communication with each other. The insertion passage P is formed so that a glass fiber G1 traveling downwards can pass through. Downward is one example of the first direction. The horizontal cross-section of the insertion passage P formed in the first cooling tube 121, the second cooling tube 122, and the third cooling tube 123 is circular. The insertion passages P formed in the first cooling tube 121, the second cooling tube 122, and the third cooling tube 123 are formed so that their inner diameters decrease in that order.

[0034] The first cooling tube 121, the second cooling tube 122, and the third cooling tube 123 have a coolant flowing between their inner and outer surfaces. The coolant is, for example, water. This cools the inner surfaces that form the insertion passage P in the first cooling tube 121, the second cooling tube 122, and the third cooling tube 123.

[0035] The first cooling tube 121 has a cooling gas supply port I. The cooling gas supply port I is formed to allow cooling gas to be supplied to the insertion passage P. The cooling gas is, for example, helium (He) and hydrogen (H ２ It is a gas containing either helium (He) or hydrogen (H) as a cooling gas. ２ The higher the concentration of ), the easier it is for the glass fiber G1 to cool.

[0036] A recovery jig 20 is attached externally to the cooling device 12. The recovery jig 20 is located at the bottom of the cooling device 12.

[0037] Figure 3 is an enlarged view of part III in Figure 2. The recovery jig 20 is equipped with a partition 21. The partition 21 is formed to partially divide the internal space and external space of the recovery jig 20. As illustrated in Figure 3, the recovery jig 20 has a recovery space S, a cooling gas recovery port O1, and a wire outlet O2 formed inside.

[0038] The recovery space S is provided as a space communicating with the insertion passage P. The recovery space S includes an incoming line space S1 and a rapidly expanding space S2. The incoming line space S1 is a space communicating with the insertion passage P. The rapidly expanding space S2 is a space located downward and communicating with the incoming line space S1. The rapidly expanding space S2 is formed such that the cross-sectional area in a horizontal cross-section orthogonal to the downward direction increases discontinuously with respect to the incoming line space S1. For example, the cross-sectional area of the horizontal cross-section in the rapidly expanding space S2 may be 5 times or more the cross-sectional area of the horizontal cross-section in the incoming line space S1. Also, the volume of the rapidly expanding space S2 may be 1 cc or more.

[0039] In the present embodiment, the cooling gas recovery port O1 is formed in the rapidly expanding space S2. The mixed gas containing the cooling gas in the rapidly expanding space S2 can be sucked from the cooling gas recovery port O1. In the present embodiment, the cooling gas recovery port O1 is located in the right direction from the center of the rapidly expanding space S2.

[0040] The outgoing line port O2 is a circular opening formed in the partition portion 21 located below the rapidly expanding space S2. The outgoing line port O2 has a size through which the glass fiber G1 can pass and is formed to have a horizontal cross-section smaller than the horizontal cross-section of the rapidly expanding space S2. The inner diameter D1 of the outgoing line port O2 may be 8 mm or less. Also, preferably, the inner diameter D1 of the outgoing line port O2 may be 5 mm or less. In the present embodiment, the inner diameter D1 of the outgoing line port O2 is 4 mm.

[0041] The first cooling pipe 121, the second cooling pipe 122, and the third cooling pipe 123 cool the inner surface forming the insertion passage by flowing a refrigerant inside. On the other hand, no refrigerant is flowed through the recovery jig 20. Therefore, the inner surface of the recovery jig 20 is not cooled.

[0042] Next, referring to FIGS. 2 and 3, the cooling of the glass fiber G1 will be described. The glass fiber G1 is traveling downward in the insertion passage P in the first cooling pipe 121, the second cooling pipe 122, and the third cooling pipe 123.

[0043] The cooling gas is supplied from the cooling gas supply port I to the insertion passage P. In the mixed gas containing the cooling gas, a part of the mixed gas flows out from the upper part of the insertion passage P of the first cooling pipe 121, and the remaining mixed gas flows downward due to the downward progress of the glass fiber G1.

[0044] The mixed gas that has flowed downward reaches the recovery jig 20. In the present embodiment, the mixed gas flowing from the wire inlet space S1 into the rapidly expanding space S2 is blocked by the partition portion 21. The mixed gas staying in the rapidly expanding space S2 is discharged from the cooling device 12 by being sucked from the cooling gas recovery port O1, and the cooling gas is recovered.

[0045] Here, the manufacturing apparatus 1 performs feedback control on the temperature of the glass fiber G1 when the glass fiber G1 exits the cooling device 12 in order to stabilize the coating diameter of the resin coated on the outer peripheral surface of the glass fiber G1. In the cooling device 12, the amount of heat by which the glass fiber G1 is cooled is determined by the length of the insertion passage P and the concentration of helium or hydrogen in the cooling gas. Therefore, the manufacturing apparatus 1 adjusts at least one of the flow rate of the cooling gas supplied to the insertion passage P and the flow rate of the mixed gas sucked. By stabilizing the concentration of helium or hydrogen in the insertion passage P, the temperature of the glass fiber G1 is controlled to be a desired temperature.

[0046] By the way, the recovery of the cooling gas, that is, the suction of the mixed gas, is not always performed during the operation of the manufacturing apparatus 1. Therefore, the concentration of helium or hydrogen inside the recovery jig 20 varies depending on whether the suction of the mixed gas is performed or not. However, since no refrigerant flows through the recovery jig 20 and thus the recovery jig 20 is not cooled, even when the concentration of helium or hydrogen varies, the control of the temperature of the glass fiber G1 is hardly affected.

[0047] Furthermore, the mixed gas flowing from the entry space S1 into the rapidly expanding space S2 entrains the surrounding gas, forming a vortex in the corner of the rapidly expanding space S2. As a result, the pressure of the mixed gas decreases and its flow velocity decreases as it flows from the entry space S1 into the rapidly expanding space S2. This decrease in the flow velocity of the mixed gas makes it easier for the mixed gas to be drawn in through the cooling gas recovery port O1.

[0048] According to the optical fiber G2 manufacturing apparatus 1 of this embodiment, the recovery jig 20 makes it possible to recover the cooling gas used in the cooling device 12. Furthermore, since the recovery jig 20 is not cooled, the temperature of the glass fiber G1 exiting from the outlet O2 remains stable regardless of whether or not the cooling gas is recovered. This makes it easier to control the coating diameter of the glass fiber G1, and thus makes it easier to stabilize the coating diameter of the optical fiber G2.

[0049] In the optical fiber G2 manufacturing apparatus 1 of this embodiment, the inner diameter D1 of the outlet O2 is 5 mm or less. Therefore, cooling gas is less likely to leak out of the outlet O2 of the recovery jig 20. As a result, the amount of cooling gas recovered by the recovery jig 20 increases.

[0050] According to the optical fiber G2 manufacturing apparatus 1 of this embodiment, the recovery space S includes a rapidly expanding space S2 in which the flow path expands discontinuously with respect to the input space S1, and the cooling gas recovery port O1 is formed to communicate with the rapidly expanding space S2. As a result, pressure loss occurs in the cooling gas due to the rapidly expanding space S2. This reduces the downward flow velocity of the cooling gas during recovery, thus increasing the amount of cooling gas recovered by the recovery jig 20.

[0051] In the optical fiber G2 manufacturing apparatus 1 of this embodiment, the recovery jig 20 is provided in the cooling device 12 in a direction that is vertically downward, which is the direction of travel of the glass fiber G1. Therefore, the cooling gas accelerated as the glass fiber G1 travels can be recovered. This improves the efficiency of cooling gas recovery.

[0052] In the optical fiber G2 manufacturing apparatus 1 of this embodiment, the cooling gas is helium (He) and hydrogen (H ２) includes any of the above. The manufacturing apparatus 1 of this embodiment can manufacture optical fibers G2 while recovering cooling gases containing helium and hydrogen, which are generally expensive.

[0053] Next, a modified optical fiber manufacturing apparatus will be described. Figure 4 is a perspective view of the insertion passage P of the third cooling tube 123, the cable entry space S1A in the retrieval jig 20A, and the rapidly expanding space S2A of the modified manufacturing apparatus. As illustrated in Figure 4, the cable entry space S1A is formed to have a circular horizontal cross-section, similar to the insertion passage P. The rapidly expanding space S2A is formed to have a rectangular horizontal cross-section with a side extending to the right and a side extending to the front. The rightward direction is perpendicular to the downward direction and is an example of a second direction. The front direction is perpendicular to the downward direction and intersects with the rightward direction and is an example of a third direction.

[0054] The rightward dimension L2 in the rapidly expanding space S2A may be five times or more the minimum rightward dimension L1 of the insertion passage P. In this embodiment, the third cooling tube 123 is formed such that the dimension of the insertion passage P is minimized, so the minimum rightward dimension L1 of the insertion passage P corresponds to the rightward dimension of the insertion passage P of the third cooling tube 123. For example, the minimum rightward dimension L1 of the insertion passage P is 3 mm, and the rightward dimension L2 in the rapidly expanding space S2A is 20 mm.

[0055] On the other hand, the forward dimension L4 in the rapidly expanding space S2A may be 1.5 times or less the minimum forward dimension L3 of the insertion passage P. In this embodiment, since the third cooling tube 123 is formed to minimize the dimension of the insertion passage P, the minimum forward dimension L3 of the insertion passage P corresponds to the rightward dimension of the third cooling tube 123 in the insertion passage P. For example, the minimum forward dimension L3 of the insertion passage P is 3 mm, and the forward dimension L4 in the rapidly expanding space S2A is 4 mm.

[0056] The rapidly expanding space S2A is formed such that its rightward dimension is five times or more than that of the insertion passage P. On the other hand, the rapidly expanding space S2A is formed such that its forward dimension is 1.5 times or less than that of the insertion passage P.

[0057] The flow velocity increases due to suction near the cooling gas recovery port O1. Therefore, if the cooling gas recovery port O1 is formed too close to the glass fiber G1, linear vibration is more likely to occur in the glass fiber G1. For this reason, it is preferable to form the cooling gas recovery port O1 as far away from the glass fiber G1 as possible.

[0058] However, if the rapidly expanding space S2A is too large, the suction device for drawing in the cooling gas may become too large. Also, if the suction force from the suction device is too strong, linear vibration is more likely to occur in the glass fiber G1.

[0059] Furthermore, if the horizontal cross-sectional area of ​​the rapidly expanding space S2A is excessively large compared to the insertion passage P and the wire entry space S1A, turbulence is more likely to occur when the mixed gas flows into the rapidly expanding space S2A. Turbulence can cause wire wobble in the glass fiber G1.

[0060] If the horizontal cross-section of the rapidly expanding space S2A is circular or square, even if the cross-sectional area of ​​the rapidly expanding space S2A is sufficiently large relative to the insertion passage P and the cable entry space S1A, the cooling gas recovery port O1 may be formed too close to the glass fiber G1. Conversely, even if the cooling gas recovery port O1 is formed at a sufficiently far distance from the glass fiber G1, the cross-sectional area of ​​the horizontal cross-section of the rapidly expanding space S2A may be excessively large relative to the insertion passage P and the cable entry space S1A.

[0061] According to the optical fiber G2 manufacturing apparatus 1 of this embodiment, the cooling gas recovery port O1 can be formed at a sufficiently large distance from the glass fiber G1, and the cross-sectional area of ​​the rapidly expanding space S2A in the horizontal cross-section is less likely to increase relative to the insertion passage P and the wire entry space S1A. As a result, wire wobble is less likely to occur in the glass fiber G1, making it possible to manufacture the optical fiber G2 in a stable state.

[0062] Next, we will explain the analysis results of the optical fiber manufacturing apparatus. Figure 5 is a graph showing the helium outflow path and the flow rate of the outflowing helium in the manufacturing apparatus. The mixed gas contains helium as a cooling gas. The solid line shows the flow rate of helium recovered at the cooling gas recovery port of the recovery jig. The dashed line shows the flow rate of helium supplied to the insertion passage. In Figure 5, the flow rate of helium supplied to the insertion passage is constant at 5 L / min. The dashed line shows the flow rate of helium outflow from the outlet. The dashed line shows the flow rate of helium outflow from the top of the insertion passage. The vertical axis shows the flow rate of helium. The horizontal axis shows the flow rate of the mixed gas. For each flow rate, a positive value indicates that helium is flowing into the insertion passage or the internal space of the recovery jig. A negative value indicates that helium is flowing out of the insertion passage or the internal space of the recovery jig.

[0063] As illustrated in Figure 5, as the amount of mixed gas drawn in increased, the flow rate of helium flowing out from the outlet and the flow rate of helium flowing out from the top of the insertion passage decreased, while the flow rate of helium recovered at the cooling gas recovery port tended to increase. A similar trend was observed when the flow rate of helium supplied to the insertion passage and the inner diameter of the outlet were changed.

[0064] Here, we analyzed the effect of the inner diameter of the outlet on the helium recovery rate. Figure 6 is a graph showing the helium recovery rate when the inner diameter of the outlet is changed. The vertical axis represents the helium recovery rate, and the horizontal axis represents the inner diameter of the outlet. In this analysis, the flow rate of helium supplied to the insertion passage was 5 L / min. The flow rate of the mixed gas drawn in at the cooling gas recovery port was also 5 L / min.

[0065] As illustrated in Figure 6, the helium recovery rate remained almost constant when the inner diameter of the outlet was between 3 mm and 8 mm, and tended to decrease when the inner diameter of the outlet was greater than 8 mm. This confirmed that it is desirable for the inner diameter of the outlet to be 8 mm or less.

[0066] Although this disclosure 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 this disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the embodiments described above and can be changed to a number, position, shape, etc. that is suitable for carrying out this disclosure.

[0067] 1 Manufacturing equipment 11 Heating furnace 11a Heater 12 Cooling device 13 Glass outer diameter measuring section 14 Resin coating section 15 Resin curing section 16 Outer diameter measuring section 17 Direct roller 18 Capstan 19 Winding roller 20 Recovery jig 21 Partition section 121 First cooling tube 122 Second cooling tube 123 Third cooling tube 141 Die 181 Capstan belt 182 Capstan roller D1 Inner diameter G0 Glass base material G1 Glass fiber G2 Optical fiber I Cooling gas supply port O1 Cooling gas recovery port O2 Outlet port P Insertion passage S Recovery space S1 Inlet space S2 Rapid expansion space

Claims

1. An optical fiber manufacturing apparatus comprising: a cooling device for cooling glass fibers drawn from a heated and softened glass base material and traveling in a first direction; and a recovery jig attached externally to the cooling device, wherein the cooling device has an insertion passage through which the glass fibers traveling in the first direction can pass, and a cooling gas supply port for supplying cooling gas to the insertion passage; the recovery jig has a recovery space communicating with the insertion passage, a cooling gas recovery port formed to communicate with the recovery space and for discharging the cooling gas, and an outlet for allowing the glass fibers to exit the recovery space in the first direction; the inner surface of the cooling device forming the insertion passage is cooled by a refrigerant flowing inside the cooling device; and no refrigerant flows through the recovery jig.

2. The optical fiber manufacturing apparatus according to claim 1, wherein the inner diameter of the output port is 8 mm or less.

3. The optical fiber manufacturing apparatus according to claim 1 or claim 2, wherein the recovery space includes an entry space which is a space in communication with the insertion passage, and a rapidly expanding space which is located in the first direction relative to the entry space and is in communication with the entry space, and the cross-sectional area in a section perpendicular to the first direction is discontinuously larger than that of the entry space, and the cooling gas recovery port is formed to communicate with the rapidly expanding space.

4. The optical fiber manufacturing apparatus according to claim 3, wherein the rapidly expanding space is a space formed along a second direction perpendicular to the first direction and a third direction perpendicular to the first direction and intersecting the second direction, the dimension of the rapidly expanding space in the second direction is five times or more the minimum dimension of the insertion passage in the second direction, and the dimension of the rapidly expanding space in the third direction is 1.5 times or less the minimum dimension of the insertion passage in the third direction.

5. The optical fiber manufacturing apparatus according to any one of claims 1 to 4, wherein the first direction is a direction directed vertically downward, and the recovery jig is provided at the lower part of the cooling device.

6. The cooling gas is helium (He) and hydrogen (H ２ An apparatus for manufacturing optical fibers according to any one of claims 1 to 5, comprising any of the above.

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