Resin coating device and method for manufacturing optical fiber

Abstract

This resin coating device comprises: a point that has a point lower surface and a point hole; a first die that is disposed directly below the point and has a first die upper surface that is in contact with the point lower surface, a first die lower surface, and a first die hole; a second die that is disposed directly below the first die and has a second die upper surface that is in contact with the first die lower surface, and a second die hole; a first resin supply path; and a second resin supply path. The first die lower surface and the second die upper surface are tapered surfaces that are rotationally symmetric about a reference axis that follows the direction in which glass fibers extend and that passes through the first die hole. The first die lower surface and the second die upper surface have the same tilt angle relative to the reference axis.

Description

Resin application device and optical fiber manufacturing method

[0001] This disclosure relates to a resin coating device and a method for manufacturing an optical fiber. This application claims priority to Japanese Application No. 2024-118738, filed on July 24, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] Patent Document 1 discloses an optical fiber resin coating device for forming a coating on the surface of an optical fiber.

[0003] Japanese Patent Application Publication No. 10-226540

[0004] A resin application device for applying resin to a surface of a glass fiber by passing the glass fiber includes: a point having a point lower surface and a point hole through which the glass fiber is inserted; a first die disposed directly below the point and having a first die upper surface abutting the point lower surface, a first die lower surface, and a first die hole through which the glass fiber is inserted; a second die disposed directly below the first die and having a second die upper surface abutting the first die lower surface and a second die hole through which the glass fiber is inserted; a first resin supply path connected to a first inlet located between the point and the first die; and a second resin supply path connected to a second inlet located between the first die and the second die. The first die lower surface and the second die upper surface are tapered surfaces that are rotationally symmetric about a reference axis that extends along the traveling direction of the glass fiber and passes through the first die hole. The first die lower surface and the second die upper surface have the same inclination angle with respect to the reference axis.

[0005] Fig. 1 is a schematic cross-sectional view of a resin application apparatus according to a first embodiment of the present disclosure. Fig. 2 is a schematic cross-sectional view of a first die of the resin application apparatus of Fig. 1. Fig. 3 is a schematic cross-sectional view of a resin application apparatus according to a first modified example. Fig. 4 is a schematic cross-sectional view of a resin application apparatus according to a second modified example. Fig. 5 is a schematic cross-sectional view of a resin application apparatus according to a third modified example. Fig. 6 is a schematic cross-sectional view of a resin application apparatus according to a fourth modified example.

[0006] If an attempt is made to form a thinner coating layer, there is a risk that uneven thickness may occur.

[0007] An object of the present disclosure is to provide a resin application device and an optical fiber manufacturing method that can reduce uneven thickness when two types of resin are thinly applied to a glass fiber.

[0008] According to the present disclosure, it is possible to provide a resin application device and an optical fiber manufacturing method that reduce uneven thickness when two types of resin are thinly applied to a glass fiber.

[0009] First, embodiments of the present disclosure will be described. (1) A resin application device according to one aspect of the present disclosure is a resin application device that applies resin to a surface of a glass fiber by passing the glass fiber through the resin application device, the resin application device comprising: a point having a point lower surface and a point hole through which the glass fiber is inserted; a first die disposed directly below the point and having a first die upper surface abutting the point lower surface, a first die lower surface, and a first die hole through which the glass fiber is inserted; a second die disposed directly below the first die and having a second die upper surface abutting the first die lower surface and a second die hole through which the glass fiber is inserted; a first resin supply passage connected to a first inlet located between the point and the first die; and a second resin supply passage connected to a second inlet located between the first die and the second die. The first die lower surface and the second die upper surface are tapered surfaces that are rotationally symmetric about a reference axis that extends along the traveling direction of the glass fiber and passes through the first die hole. The first die lower surface and the second die upper surface have the same inclination angle with respect to the reference axis.

[0010] According to the present disclosure, a resin application device includes a first die having a first die lower surface and a first die hole, and a second die having a second die upper surface and a second die hole. The first die lower surface and the second die upper surface are both tapered surfaces that are rotationally symmetrical about a reference axis that extends along the glass fiber traveling direction and passes through the first die hole. The first die lower surface and the second die upper surface have the same inclination angle with respect to the reference axis. Therefore, an operator can axially align the first die hole and the second die hole simply by abutting the first die lower surface and the second die upper surface. This reduces thickness unevenness when applying two types of resin to a glass fiber.

[0011] If the lower surface of the first die and the upper surface of the second die were parallel to the direction of travel of the glass fiber, in other words, if the inclination angle were 0 degrees, the friction between the first die and the second die would be too great, making it difficult to attach and detach the first die and the second die. In this embodiment, the lower surface of the first die and the upper surface of the second die are tapered, making it easy to attach and detach the first die and the second die. Therefore, the handleability of the first die and the second die is improved.

[0012] (2) In the above (1), the inclination angle of the upper surface of the second die may be 2 degrees or more and 30 degrees or less.

[0013] If the inclination angle is less than 2 degrees, processing is difficult, friction between the first die and the second die increases, and the first die and the second die are difficult to detach. If the inclination angle exceeds 30 degrees, it is difficult to improve the accuracy of the axis alignment, and the sizes of the first die and the second die become larger than necessary. According to the present disclosure, the inclination angle of the upper surface of the second die is between 2 degrees and 30 degrees. This makes it easy to detach the first die and the second die. Furthermore, the accuracy of the axis alignment is high, and the sizes of the first die and the second die can be reduced.

[0014] (3) In the above (1) or (2), the height of the upper surface of the second die in the traveling direction may be 3 mm or more and 20 mm or less.

[0015] If the height of the upper surface of the second die is less than 3 mm, the contact surface between the lower surface of the first die and the upper surface of the second die is small, making attachment unstable. If the height exceeds 20 mm, processing is difficult. According to the present disclosure, the attachment of the first die and the second die is stable and processing is relatively easy.

[0016] (4) In any one of the above (1) to (3), at least a portion of the first die may be formed of a super-rigid member.

[0017] According to the present disclosure, at least a portion of the first die is formed of an ultra-rigid material, which is less susceptible to thermal expansion and allows for more accurate axial alignment. The ultra-rigid material is a material made of a material harder than ordinary metals, such as tungsten carbide (WC) or cobalt (Co).

[0018] (5) In any one of the above (1) to (4), the difference in the thermal expansion coefficients of the first die, the second die, and the point is 3.0 × 10 －６ It may be the following:

[0019] If the difference in the thermal expansion coefficients of the first die, the second die, and the points is large, one of the members may thermally expand more than the other due to temperature changes after these members are assembled, which may cause the axes to become misaligned. According to the present disclosure, the difference in the thermal expansion coefficients of the first die, the second die, and the points is 3.0 × 10 －６ Since the temperature is less than 100°C, the shaft is unlikely to become misaligned even if there is a temperature change after these members are assembled.

[0020] (6) In any of (1) to (5) above, the point lower surface and the first die upper surface may be tapered surfaces that are rotationally symmetric about the reference axis, and the point lower surface and the first die upper surface may have the same inclination angle with respect to the reference axis.

[0021] According to the present disclosure, the point lower surface and the first die upper surface are tapered surfaces that are rotationally symmetric about the reference axis and have the same inclination angle with respect to the reference axis, so that an operator can align the axes of the point hole and the first die hole simply by bringing the point lower surface and the first die upper surface into contact with each other.

[0022] (7) In any of (1) to (6) above, the first die further has an upper alignment portion and a lower alignment portion, the lower alignment portion being arranged lower than the upper alignment portion in the traveling direction, the upper alignment portion having an upper tapered portion whose diameter narrows downward from an entrance in the traveling direction, and an upper land portion arranged directly below the upper tapered portion, connected to the upper tapered portion, and having a constant diameter in the traveling direction, the lower alignment portion having a lower tapered portion whose diameter narrows downward from an entrance in the traveling direction, and a lower land portion arranged directly below the lower tapered portion, connected to the lower tapered portion, and having a constant diameter in the traveling direction, and the upper tapered portion, the upper land portion, the lower tapered portion, and the lower land portion may each be a part of the first die hole.

[0023] According to the present disclosure, the first die has an upper tapered portion and a lower tapered portion, the diameter of which narrows in the advancing direction. Since the deflection of the glass fiber in a direction perpendicular to the advancing direction is restrained at two points of the upper tapered portion and the lower tapered portion, the glass fiber is less likely to vibrate. As a result, thickness deviation can be reduced, and resin can be applied to the glass fiber with higher dimensional accuracy.

[0024] (8) In (7) above, the upper aligning portion has an aligning lower surface, the lower aligning portion has an aligning upper surface that abuts the aligning lower surface, the aligning lower surface and the aligning upper surface are tapered surfaces that are rotationally symmetrical around the reference axis, and the aligning lower surface and the aligning upper surface may have the same inclination angle with respect to the reference axis.

[0025] According to the present disclosure, the lower and upper aligning surfaces are tapered surfaces that are rotationally symmetrical about the reference axis and have the same inclination angle with respect to the reference axis, allowing an operator to align the upper and lower aligning parts simply by bringing the lower and upper aligning surfaces into contact with each other.

[0026] (9) A method for manufacturing an optical fiber according to one aspect of the present disclosure includes a step of applying resin to a surface of the glass fiber using a resin application device described in any one of (1) to (8) above.

[0027] According to the present disclosure, thickness unevenness is unlikely to occur and two types of resin can be thinly applied to the glass fiber.

[0028] (Details of an embodiment of the present disclosure) Specific examples of a resin application device 1 according to an embodiment of the present disclosure will be described with reference to the drawings. Note that 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.

[0029] First Embodiment Fig. 1 is a schematic cross-sectional view of a resin application device 1 according to a first embodiment of the present disclosure. The resin application device 1 is configured to pass a glass fiber G1 through the resin application device 1 and apply a resin to the surface of the glass fiber G1. The diameter of the glass fiber G1 is, for example, φ80 μm or more and 125 μm or less. As illustrated in Fig. 1, the resin application device 1 includes a point 10, a first die 20, a second die 30, a first resin supply path 40, and a second resin supply path 50.

[0030] The point 10 is disposed at the entrance of the resin coating device 1. The point 10 is disposed directly above the first die 20 in the traveling direction D1 of the glass fiber G1. The point 10 has a point lower surface 11 and a point hole 19. The point hole 19 is formed to allow the glass fiber G1 to pass through. The cross section of the point hole 19 in a plane perpendicular to the traveling direction D1 is circular.

[0031] At least a portion of the point 10 is formed from a super-rigid material. The main components of the super-rigid material are, for example, tungsten carbide (WC) and cobalt (Co). The entire point 10 may be formed from a super-rigid material. Only the portion that forms the point hole 19 may be formed from a super-rigid material, or only the portion that forms the point lower surface 11 may be formed from a super-rigid material.

[0032] The second die 30 is disposed at the outlet of the resin coating device 1. The second die 30 is disposed directly below the first die 20 in the traveling direction D1 of the glass fiber G1. The second die 30 has a second die upper surface 31 and a second die hole 39. The second die hole 39 is formed to allow the glass fiber G1 to pass through. The cross section of the second die hole 39 in a plane perpendicular to the traveling direction D1 is circular.

[0033] At least a portion of the second die 30 is formed of a super-rigid material. The entire second die 30 may be formed of a super-rigid material. Only the portion that forms the second die hole 39 may be formed of a super-rigid material, or only the portion that forms the second die upper surface 31 may be formed of a super-rigid material.

[0034] The first die 20 is disposed between the point 10 and the second die 30 in the traveling direction D1 of the glass fiber G1. The first die 20 has a first die upper surface 21, a first die lower surface 22, and a first die hole 29. The first die upper surface 21 is formed to abut against the point lower surface 11. The first die lower surface 22 is formed to abut against the second die upper surface 31. The first die hole 29 is formed to allow the glass fiber G1 to pass through. The cross section of the first die hole 29 in a plane perpendicular to the traveling direction D1 is circular.

[0035] At least a portion of the first die 20 is formed of a super-rigid material. The entire first die 20 may be formed of a super-rigid material. Only the portion that forms the first die hole 29 may be formed of a super-rigid material. Only the portion that forms the first die upper surface 21 and the portion that forms the first die lower surface 22 may be formed of a super-rigid material.

[0036] The difference in the thermal expansion coefficients of the first die 20, the second die 30, and the point 10 is 3.0×10 －６ The following is the result.

[0037] 1 , the first die lower surface 22 and the second die upper surface 31 abutting against the first die lower surface 22 are tapered surfaces that are rotationally symmetrical about a reference axis A that extends along the traveling direction D1 of the glass fiber G1 and passes through the first die hole 29. For example, the diameters of the first die lower surface 22 and the second die upper surface 31 both gradually increase downward in the traveling direction D1.

[0038] Fig. 2 is a schematic cross-sectional view of the first die 20. As illustrated in Fig. 2, the "inclination angle" in this embodiment is the angle formed when an imaginary extension line of the tapered surface intersects with the reference axis A, and is an angle that extends rotationally symmetrically around the reference axis A. The first die lower surface 22 and the second die upper surface 31 both have an inclination angle θ2 with respect to the reference axis A. The inclination angle θ2 is equal to or greater than 2 degrees and equal to or less than 30 degrees. The height H2 of the first die lower surface 22 and the height of the second die upper surface 31 in the traveling direction D1 of the glass fiber G1 are both equal to or greater than 3 mm and equal to or less than 20 mm (see Figs. 1 and 2 ).

[0039] Furthermore, the first die upper surface 21 and the point lower surface 11 abutting against the first die upper surface 21 are tapered surfaces that are rotationally symmetric about the reference axis A. For example, the diameters of the first die upper surface 21 and the point lower surface 11 both gradually decrease downward in the traveling direction D1.

[0040] The first die upper surface 21 and the point lower surface 11 both have an inclination angle θ1 with respect to the reference axis A. The inclination angle θ1 is 2 degrees or more and 30 degrees or less. The height H1 of the first die upper surface 21 and the height of the point lower surface 11 in the traveling direction D1 of the glass fiber G1 are both 3 mm or more and 20 mm or less (see FIGS. 1 and 2 ).

[0041] 1 , the first resin supply path 40 is connected to a first inlet 41 located between the point 10 and the first die 20. The first inlet 41 is connected to the outlet of the point hole 19 and to the inlet of the first die hole 29 in the traveling direction D1 of the glass fiber G1. The first resin supply path 40 is formed to supply the primary resin to be applied to the surface of the glass fiber G1 to the first die hole 29. The primary resin is, for example, a urethane acrylate-based ultraviolet-curable resin.

[0042] The second resin supply path 50 is connected to a second inlet 51 located between the first die 20 and the second die 30. The second inlet 51 is connected to the outlet of the first die hole 29 and to the inlet of the second die hole 39 in the traveling direction D1 of the glass fiber G1. The second resin supply path 50 is formed to supply a secondary resin, which is different from the primary resin, to the second die hole 39. The secondary resin is applied onto the primary resin that covers the surface of the glass fiber G1. The secondary resin is, for example, a urethane acrylate-based ultraviolet-curable resin.

[0043] Next, we will explain how to use the resin coating device 1. First, the glass fiber G1 is inserted into the point hole 19 of the point 10 located at the entrance of the resin coating device 1. The glass fiber G1 inserted into the point hole 19 is then inserted into the first die 20.

[0044] The glass fiber G1 inserted from the point 10 passes through a first die hole 29 of the first die 20. At this time, a primary resin is supplied from a first resin supply path 40 into the first die hole 29 of the first die 20. By inserting the glass fiber G1 into the first die hole 29 to which the primary resin has been supplied, the primary resin is applied onto the surface of the glass fiber G1. After passing through the first die hole 29, the glass fiber G1 is inserted into a second die 30.

[0045] The glass fiber G1 coated with the primary resin passes through the second die hole 39 of the second die 30. At this time, the secondary resin is supplied into the second die hole 39 of the second die 30 from the second resin supply path 50. By inserting the glass fiber G1 into the second die hole 39 to which the secondary resin has been supplied, the secondary resin is coated onto the primary resin of the glass fiber G1. In this way, the resin coating device 1 coats the glass fiber G1 with the primary resin and the secondary resin.

[0046] Next, the assembly of the resin coating device 1 will be described. First, an operator assembles the point 10 from above the first die 20 in the traveling direction D1 of the glass fiber G1. At this time, the point lower surface 11 and the first die upper surface 21 abut against each other. Both the point lower surface 11 and the first die upper surface 21 are tapered surfaces that are rotationally symmetrical about the reference axis A and have the same inclination angle θ1 with respect to the reference axis A. Therefore, the operator can align the axis of the point hole 19 with the reference axis A that passes through the first die hole 29 simply by abutting the point lower surface 11 against the first die upper surface 21.

[0047] After aligning the axes of the point hole 19 and the first die hole 29, the worker assembles the first die 20 together with the point 10 from above the second die 30 in the traveling direction D1 of the glass fiber G1. At this time, the first die lower surface 22 and the second die upper surface 31 abut against each other. Both the first die lower surface 22 and the second die upper surface 31 are tapered surfaces that are rotationally symmetric about the reference axis A and have the same inclination angle θ2 with respect to the reference axis A. Therefore, simply by abutting the first die lower surface 22 and the second die upper surface 31, the worker can align the axis of the second die hole 39 with the reference axis A that passes through the first die hole 29. In this manner, the point 10 and the second die 30 are assembled to the first die 20.

[0048] The resin coating device 1 uses multiple types of first dies 20 and multiple types of second dies 30 depending on the type of resin to be coated on the glass fiber G1 and the desired coating thickness. Furthermore, the diameters of the first die holes 29 and the second die holes 39 are both small, and the axes of these small holes must be aligned each time the resin to be coated or the coating thickness is changed. The diameter of the first die hole 29 is, for example, 100 μm or more and 300 μm or less. The diameter of the second die hole 39 is, for example, 150 μm or more and 400 μm or less.

[0049] If either the first die lower surface 22 or the second die upper surface 31 were not tapered, the first die lower surface 22 and the second die upper surface 31 would not abut against each other, resulting in a large clearance between the first die lower surface 22 and the second die upper surface 31. In such a case, the axial alignment accuracy of the first die hole 29 and the second die hole 39 would be reduced.

[0050] However, the resin application apparatus 1 of this embodiment includes a first die 20 and a second die 30. The first die 20 has a small-diameter first die hole 29 and a first die lower surface 22 that is a tapered surface rotationally symmetrical about the reference axis A. Furthermore, the second die 30 has a small-diameter second die hole 39 and a second die upper surface 31 that is a tapered surface rotationally symmetrical about the reference axis A. Both the first die lower surface 22 and the second die upper surface 31 have the same inclination angle θ2 with respect to the reference axis A. Therefore, when the second die 30 is assembled to the first die 20, the first die lower surface 22 and the second die upper surface 31 abut against each other. The clearance between the first die lower surface 22 and the second die upper surface 31 is small. By simply abutting the first die lower surface 22 and the second die upper surface 31, an operator can precisely align the axis of the small-diameter second die hole 39 with the reference axis A of the first die hole 29. In particular, because the first die 20 having the small-diameter first die hole 29 has a tapered first die lower surface 22, and the second die 30 having the small-diameter second die hole 39 has a tapered second die upper surface 31, the axes of the first die hole 29 and the second die hole 39 can be aligned with high precision. This reduces thickness deviation when thinly applying two types of resin to the glass fiber G1. The axial misalignment of the second die hole 39 with respect to the reference axis A is, for example, within 3 μm. If the axial misalignment of the second die hole 39 with respect to the reference axis A is within 1.5 μm, thickness deviation can be further reduced.

[0051] Here, if the clearance is made as small as possible to minimize the axial misalignment, the friction generated during assembly and removal may become too great. In particular, if the first die lower surface 22 and the second die upper surface 31 are not tapered but are parallel to the traveling direction D1 of the glass fiber G1, in other words, if the inclination angle θ2 is set to 0 degrees and the clearance is reduced, the friction generated between the first die lower surface 22 and the second die upper surface 31 during assembly and removal becomes too great. This makes it difficult to remove the second die 30 from the first die 20 after resin application. In this embodiment, the first die lower surface 22 and the second die upper surface 31 are tapered, making it easy to remove the second die 30 from the first die 20. Therefore, the handleability of the first die 20 and the second die 30 is improved.

[0052] If the inclination angle θ2 is less than 2 degrees, it is difficult to process the die to form such an inclination angle. Furthermore, the friction between the first die 20 and the second die 30 becomes too large, making it difficult to attach and detach the first die 20 and the second die 30. If the inclination angle θ2 exceeds 30 degrees, it becomes difficult to achieve high precision in aligning the axes, and the sizes of the first die 20 and the second die 30 become larger than necessary.

[0053] In this embodiment, the inclination angle θ2 of the first die lower surface 22 and the second die upper surface 31 is equal to or greater than 2 degrees and equal to or less than 30 degrees. This makes it easy to attach and detach the first die 20 and the second die 30. Furthermore, this provides high precision in axial alignment, and allows the first die 20 and the second die 30 to be made smaller in size.

[0054] The height H2 of the first die lower surface 22 and the second die upper surface 31 in the traveling direction D1 of the glass fiber G1 is 3 mm or more and 20 mm or less. If the height H2 is less than 3 mm, the contact surface between the first die lower surface 22 and the second die upper surface 31 is small, making the attachment of the first die 20 and the second die 30 unstable. If the height H2 exceeds 20 mm, processing is difficult. According to this embodiment, the attachment of the first die 20 and the second die 30 is stable and processing is relatively easy.

[0055] The point lower surface 11 and the first die upper surface 21 are tapered surfaces rotationally symmetrical about the reference axis A and have the same inclination angle θ1 with respect to the reference axis A. Therefore, simply by abutting the point lower surface 11 with the first die upper surface 21, an operator can precisely align the axis of the small-diameter point hole 19 with the reference axis A of the first die hole 29. In particular, because the first die 20 having the small-diameter first die hole 29 has the tapered first die upper surface 21, and the point 10 having the small-diameter point hole 19 has the tapered point lower surface 11, the axes of the first die hole 29 and the point hole 19 can be precisely aligned. Therefore, even if the resin coating thickness applied to the glass fiber G1 is made thinner, thickness deviation can be reduced. The axial misalignment of the point hole 19 with respect to the reference axis A is, for example, within 3 μm. Furthermore, because the point lower surface 11 and the first die upper surface 21 are tapered, the point 10 can be easily removed from the first die 20. Therefore, the handling of the first die 20 and the point 10 is improved.

[0056] (First Modification) Figure 3 is a schematic cross-sectional view of a resin coating apparatus 1A according to a first modification. In the configuration shown in Figure 3, the same components as those shown in Figure 1 are designated by the same reference numerals, and their description will be omitted. As illustrated in Figure 3, the resin coating apparatus 1A is provided with a first die 20A and a second die 30A. The diameter of the first die lower surface 22A of the first die 20A gradually decreases downward in the traveling direction D1 of the glass fiber G1. Furthermore, the diameter of the second die upper surface 31A of the second die 30A also gradually decreases downward in the traveling direction D1 of the glass fiber G1.

[0057] In this example, both the first die lower surface 22A and the second die upper surface 31A are tapered surfaces that are rotationally symmetric about the reference axis A and have the same inclination angle θ3 with respect to the reference axis A. Therefore, an operator can align the first die hole 29 and the second die hole 39 with the reference axis A simply by bringing the first die lower surface 22A and the second die upper surface 31A into contact with each other.

[0058] (Second Modification) Figure 4 is a schematic cross-sectional view of a resin coating apparatus 1B according to a second modification. In the configuration shown in Figure 4, the same components as those shown in Figure 1 are designated by the same reference numerals, and their description will be omitted. As illustrated in Figure 4, the resin coating apparatus 1B is provided with a point 10B and a first die 20B. The diameter of the first die upper surface 21B of the first die 20B gradually increases downward in the traveling direction D1. Furthermore, the diameter of the point lower surface 11B of the point 10B also gradually increases downward in the traveling direction D1.

[0059] In this example, both the first die upper surface 21B and the point lower surface 11B are tapered surfaces that are rotationally symmetric about the reference axis A and have the same inclination angle θ4 with respect to the reference axis A. Therefore, an operator can align the first die hole 29 and the point hole 19 with the reference axis A simply by bringing the first die upper surface 21B and the point lower surface 11B into contact with each other.

[0060] (Third Modification) FIG. 5 is a schematic cross-sectional view of a resin coating apparatus 1C according to a third modification. In the configuration shown in FIG. 5, the same components as those shown in FIG. 1 are designated by the same reference numerals, and their description will be omitted. As illustrated in FIG. 5, the resin coating apparatus 1C includes a point 10C, a first die 20C, and a second die 30C. The diameter of the first die upper surface 21C of the first die 20C gradually increases downward in the traveling direction D1. Furthermore, the diameter of the point lower surface 11C of the point 10C also gradually increases downward in the traveling direction D1. Furthermore, the diameter of the first die lower surface 22C of the first die 20C gradually decreases downward in the traveling direction D1. Furthermore, the diameter of the second die upper surface 31C of the second die 30C also gradually decreases downward in the traveling direction D1.

[0061] In this example, both the first die upper surface 21C and the point lower surface 11C are tapered surfaces that are rotationally symmetric about the reference axis A and have the same inclination angle θ5 with respect to the reference axis A. Therefore, an operator can align the first die hole 29 and the point hole 19 with the reference axis A simply by bringing the first die upper surface 21C and the point lower surface 11C into contact with each other.

[0062] Furthermore, both the first die lower surface 22C and the second die upper surface 31C are tapered surfaces that are rotationally symmetric about the reference axis A and have the same inclination angle θ6 with respect to the reference axis A. Therefore, an operator can align the first die hole 29 and the second die hole 39 with the reference axis A simply by bringing the first die lower surface 22C and the second die upper surface 31C into contact with each other.

[0063] In this example, the first die 20C may have an upper intermediate hole 27 and a lower intermediate hole 28 through which the glass fiber G1 passes. Both the upper intermediate hole 27 and the lower intermediate hole 28 are part of the first die hole 29C. Both the upper intermediate hole 27 and the lower intermediate hole 28 have a constant diameter in the traveling direction D1 of the glass fiber G1, and each has a circular cross section in a plane perpendicular to the traveling direction D1. The diameters of the upper intermediate hole 27 and the lower intermediate hole 28 are both larger than the diameters of the point hole 19 and the second die hole 39. The provision of the upper intermediate hole 27 and the lower intermediate hole 28 increases the length over which the glass fiber G1 contacts the primary resin, thereby reducing vibration of the glass fiber G1 by the primary resin.

[0064] (Fourth Modification) Figure 6 is a schematic cross-sectional view of a resin coating apparatus 1D according to a fourth modification. In the configuration shown in Figure 6, the same components as those shown in Figure 1 are denoted by the same reference numerals, and their description will be omitted. As illustrated in Figure 6, in the resin coating apparatus 1D, the first die 200 has a structure in which two members are combined, and there are two systems of supply paths for the first resin (a first upper resin supply path 43 and a first lower resin supply path 44).

[0065] The first die 200 has a first die upper portion 230, a first die lower portion 240, and a first die hole 290. The first die upper portion 230 and the first die lower portion 240 are separate components. Both the first die upper portion 230 and the first die lower portion 240 are formed from a super-rigid member.

[0066] The first die upper portion 230 is disposed between the point 10 and the first die lower portion 240 in the traveling direction D1 of the glass fiber G1. The first die upper portion 230 is disposed directly below the point 10 at the entrance of the first die 20. The first die upper portion 230 has an upper aligning portion 231 and an intermediate portion 232.

[0067] The upper alignment portion 231 has an upper tapered portion 2311 and an upper land portion 2312. The diameter of the upper tapered portion 2311 narrows from the entrance to the bottom in the traveling direction D1 of the glass fiber G1. The upper land portion 2312 is disposed directly below the upper tapered portion 2311 and is connected to the upper tapered portion 2311. The diameter of the upper land portion 2312 is constant in the traveling direction D1 of the glass fiber G1. The upper tapered portion 2311 and the upper land portion 2312 are each part of the first die hole 290.

[0068] The cross section of the upper reduced diameter portion 2311 and the cross section of the upper land portion 2312 in a plane perpendicular to the traveling direction D1 of the glass fiber G1 are both circular. The diameter of the upper land portion 2312 is larger than the diameter of a lower land portion 2412 described later.

[0069] A first die upper surface 233 formed to abut against the point lower surface 11 of the point 10 is provided above the upper alignment section 231 in the traveling direction D1 of the glass fiber G1. Furthermore, a lower alignment surface 234 formed to abut against an upper alignment surface 242 of a lower alignment section 241 (described later) is provided below the upper alignment section 231.

[0070] The intermediate portion 232 has an intermediate hole 2321 through which the glass fiber G1 is inserted. The intermediate hole 2321 is part of the first die hole 290. The diameter of the intermediate hole 2321 is constant in the traveling direction D1 of the glass fiber G1. The cross section of the intermediate hole 2321 in a plane perpendicular to the traveling direction D1 of the glass fiber G1 is circular. The diameter of the intermediate hole 2321 is larger than the diameter of the upper land portion 2312 and the diameter of the lower land portion 2412.

[0071] The first die lower portion 240 is disposed between the first die upper portion 230 and the second die 30 in the traveling direction D1 of the glass fiber G1. The first die lower portion 240 is disposed directly below the upper aligning portion 231 of the first die upper portion 230 and at the entrance of the second die 30. The first die lower portion 240 has the lower aligning portion 241.

[0072] The lower alignment portion 241 has a lower tapered portion 2411 and a lower land portion 2412. The diameter of the lower tapered portion 2411 narrows from the entrance to the bottom in the traveling direction D1 of the glass fiber G1. The lower land portion 2412 is disposed directly below the lower tapered portion 2411 and is connected to the lower tapered portion 2411. The diameter of the lower land portion 2412 is constant in the traveling direction D1 of the glass fiber G1. The lower tapered portion 2411 and the lower land portion 2412 are each part of the first die hole 290.

[0073] The cross section of the lower reduced diameter portion 2411 and the cross section of the lower land portion 2412 in a plane perpendicular to the traveling direction D1 of the glass fiber G1 are both circular.

[0074] An upper aligning surface 242 formed to abut against the lower aligning surface 234 of the upper aligning portion 231 is provided above the lower aligning portion 241 in the traveling direction D1 of the glass fiber G1. Furthermore, a lower portion of the lower aligning portion 241 is provided with a first die lower surface 243 formed to abut against the second die upper surface 31 of the second die 30.

[0075] The diameter of the aligning lower surface 234 gradually decreases as it goes downward in the direction of travel D1. Furthermore, the diameter of the aligning upper surface 242 also gradually decreases as it goes downward in the direction of travel D1. Both the aligning lower surface 234 and the aligning upper surface 242 are tapered surfaces that are rotationally symmetric about the reference axis A and have the same inclination angle θ7 with respect to the reference axis A.

[0076] The first upper resin supply passage 43 is connected to a third inlet 431 located between the point 10 and the first die upper portion 230. The third inlet 431 is connected to the outlet of the point hole 19 and to the inlet of the first die upper portion 230 in the traveling direction D1 of the glass fiber G1. The first upper resin supply passage 43 is formed to supply the primary resin to an upper reduced diameter portion 2311, which is a part of the first die hole 290.

[0077] The first lower resin supply path 44 is connected to a fourth inlet 441 located between the upper land portion 2312 and the intermediate portion 232. The fourth inlet 441 is connected to an outlet of the upper land portion 2312 and an inlet of the intermediate portion 232 in the traveling direction D1 of the glass fiber G1. The first lower resin supply path 44 is formed to supply the primary resin to the intermediate portion 232, which is a part of the first die hole 290.

[0078] Next, a method of using the resin coating apparatus 1D will be described. First, the glass fiber G1 is inserted into the point hole 19 of the point 10 located at the entrance of the resin coating apparatus 1. The glass fiber G1 inserted into the point hole 19 is then inserted into the first die hole 290 of the first die 200.

[0079] The glass fiber G1 inserted through point 10 passes from the first die upper part 230 to the first die lower part 240 of the first die 200. Specifically, the glass fiber G1 passes through the upper tapered portion 2311 and the upper land portion 2312 of the upper alignment portion 231, the middle portion 232, and the lower tapered portion 2411 and the lower land portion 2412 of the lower alignment portion 241. At this time, the primary resin is supplied from the first upper resin supply path 43 and the first lower resin supply path 44 into the first die hole 290 of the first die 200, and the first die hole 290 is filled with the primary resin. By inserting the glass fiber G1 into the first die hole 290 filled with the primary resin, the primary resin is applied to the surface of the glass fiber G1.

[0080] First, the glass fiber G1 is inserted into the upper tapered portion 2311 of the upper alignment portion 231 of the first die 200. Because the diameter of the upper tapered portion 2311 gradually narrows along the advancing direction D1, the upper tapered portion 2311 exerts a strong aligning force due to the flow of the primary resin from the inlet toward the outlet. Because the glass fiber G1 passes through the upper tapered portion 2311, deflection of the glass fiber G1 in a direction perpendicular to the advancing direction D1 is reduced. The glass fiber G1 is then inserted into the upper land portion 2312.

[0081] Since the diameter of the upper land portion 2312 is relatively small within the first die hole 290, vibration of the glass fiber G1 inserted through the upper land portion 2312 is reduced, and the glass fiber G1 is less likely to come into contact with the point hole 19 or the first die hole 290. After passing through the upper land portion 2312, the glass fiber G1 is passed through the intermediate portion 232.

[0082] The intermediate section 232 is filled with primary resin through the first lower resin supply passage 44. The glass fiber G1 is inserted into the intermediate section 232 filled with the primary resin. Thereafter, the glass fiber G1 is inserted into the lower alignment section 241.

[0083] Because the diameter of the lower tapered diameter portion 2411 of the lower alignment portion 241 gradually narrows along the direction of travel D1, a strong aligning force is generated by the flow of primary resin from the inlet to the outlet in the lower tapered diameter portion 2411. Because the glass fiber G1 passes through not only the upper tapered diameter portion 2311 but also the lower tapered diameter portion 2411, it is restrained at two points, the upper tapered diameter portion 2311 and the lower tapered diameter portion 2411, and is therefore less likely to vibrate in a direction perpendicular to the direction of travel D1. The glass fiber G1 is then inserted from the lower tapered diameter portion 2411 into the lower land portion 2412.

[0084] The diameter of the lower land portion 2412 is the smallest in the first die hole 290. By passing through the lower land portion 2412, the glass fiber G1 is less likely to vibrate, and the coating diameter of the glass fiber G1 with the primary resin is determined by the diameter of the lower land portion 2412. The glass fiber G1 is then inserted into the second die 30.

[0085] The glass fiber G1 coated with the primary resin by the first die 200 passes through the second die hole 39 of the second die 30. At this time, the second die hole 39 is filled with the secondary resin supplied from the second resin supply path 50. When the glass fiber G1 is inserted into the second die hole 39 filled with the secondary resin, the secondary resin is coated onto the primary resin on the glass fiber G1. In this way, the resin coating device 1D coats the glass fiber G1 with the primary resin and the secondary resin.

[0086] As described above, the first die 200 of the resin coating apparatus 1D of this example has an upper tapered portion 2311 and a lower tapered portion 2411, the diameter of which narrows in the traveling direction D1. Because deflection perpendicular to the traveling direction D1 is restrained at two points, the upper tapered portion 2311 and the lower tapered portion 2411, the glass fiber G1 is less likely to vibrate. As a result, thickness deviation can be reduced, and resin can be coated onto the glass fiber G1 with higher dimensional accuracy.

[0087] Furthermore, in this example, both the aligning lower surface 234 and the aligning upper surface 242 are tapered surfaces that are rotationally symmetric about the reference axis A and have the same inclination angle θ7 with respect to the reference axis A. Therefore, an operator can align the first die upper surface 230 and the first die lower surface 240 with the reference axis A simply by bringing the aligning lower surface 234 and the aligning upper surface 242 into contact with each other.

[0088] Although the present 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 the present disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to the number, position, shape, etc. that are suitable for implementing the present disclosure.

[0089] The first lower resin supply path 44 may be connected to the middle or lower part of the intermediate portion 232. In this way, compared to when the first lower resin supply path 44 is not provided, the primary resin can be filled into the hole of the intermediate portion 232 and the primary resin can be applied to the glass fiber G1.

[0090] It should be understood that at least one configuration or feature described in each embodiment or example can be combined with other embodiments or examples, or can be modified in various ways.

[0091] 1, 1A, 1B, 1C, 1D Resin application device 10, 10B, 10C Point 11, 11B, 11C Point lower surface 19 Point hole 20, 20A, 20B, 20C, 200 First die 21, 21B, 21C, 233 First die upper surface 22, 22A, 22C, 243 First die lower surface 27 Upper intermediate hole 28 Lower intermediate hole 29, 29C, 290 First die hole 30, 30A, 30C Second die 31, 31A, 31C Second die upper surface 230 First die upper part 231 Upper aligning part 2311 Upper reduced diameter part 2312 Upper land part 232 Middle part 2321 Intermediate hole 234 Aligning lower surface 240 First die lower part 241 Lower alignment portion 2411 Lower reduced diameter portion 2412 Lower land portion 242 Aligning upper surface 39 Second die hole 40 First resin supply path 41 First inlet 43 First upper resin supply path 431 Third inlet 44 First lower resin supply path 441 Fourth inlet 50 Second resin supply path 51 Second inlet G1 Glass fiber D1 Traveling direction θ1, θ2, θ3, θ4, θ5, θ6, θ7 Inclination angle A Reference axis H1, H2 Height

Claims

1. A resin applicator for passing a glass fiber and applying resin to the surface of the glass fiber, comprising: a point having a point lower surface and a point hole through which the glass fiber is inserted; a first die located directly below the point and having a first die upper surface abutting the point lower surface, a first die lower surface, and a first die hole through which the glass fiber is inserted; a second die located directly below the first die and having a second die upper surface abutting the first die lower surface and a second die hole through which the glass fiber is inserted; a first resin supply path connected to a first inlet located between the point and the first die; and a second resin supply path connected to a second inlet located between the first die and the second die, wherein the first die lower surface and the second die upper surface are tapered surfaces that are rotationally symmetrical about a reference axis that extends along the traveling direction of the glass fiber and passes through the first die hole, and the first die lower surface and the second die upper surface have the same inclination angle with respect to the reference axis.

2. The resin application device according to claim 1, wherein the inclination angle of the upper surface of the second die is between 2 degrees and 30 degrees.

3. A resin application device according to claim 1 or 2, wherein the height of the upper surface of the second die in the direction of travel is 3 mm or more and 20 mm or less.

4. A resin application device according to any one of claims 1 to 3, wherein at least a portion of the first die is formed from a super-rigid material.

5. The difference in the thermal expansion coefficients of the first die, the second die, and the point is 3.0 x 10 －６ The resin application device according to any one of claims 1 to 4, wherein:

6. A resin application device described in any one of claims 1 to 5, wherein the point lower surface and the first die upper surface are tapered surfaces that are rotationally symmetrical around the reference axis, and the point lower surface and the first die upper surface have the same inclination angle with respect to the reference axis.

7. A resin application device according to any one of claims 1 to 6, wherein the first die further has an upper alignment portion and a lower alignment portion, the lower alignment portion being arranged lower than the upper alignment portion in the traveling direction, the upper alignment portion having an upper narrowing diameter portion whose diameter narrows as it goes downward from an entrance in the traveling direction, and an upper land portion which is arranged directly below the upper narrowing diameter portion, connected to the upper narrowing diameter portion, and has a constant diameter in the traveling direction, the lower alignment portion having a lower narrowing diameter portion whose diameter narrows as it goes downward from an entrance in the traveling direction, and a lower land portion which is arranged directly below the lower narrowing diameter portion, connected to the lower narrowing diameter portion, and has a constant diameter in the traveling direction, 8. A resin application device as described in claim 7, wherein the upper alignment portion has an alignment lower surface, the lower alignment portion has an alignment upper surface that abuts the alignment lower surface, the alignment lower surface and the alignment upper surface are tapered surfaces that are rotationally symmetrical about the reference axis, and the alignment lower surface and the alignment upper surface have the same inclination angle with respect to the reference axis.

9. A method for manufacturing an optical fiber, comprising a step of applying resin to the surface of the glass fiber using a resin application device according to any one of claims 1 to 8.

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