JP6677123B2 - Seal structure of optical fiber drawing furnace and method of manufacturing optical fiber - Google Patents

Description

  The present invention relates to a sealing structure for an optical fiber drawing furnace, a method for manufacturing an optical fiber, and more particularly, to an upper end opening of an optical fiber drawing furnace and a glass base material for an optical fiber inserted from an upper end opening. The present invention relates to a seal structure of an optical fiber drawing furnace for closing a gap between the optical fibers, and a method of manufacturing an optical fiber.

  For the optical fiber, a glass preform for optical fiber containing quartz as a main component (hereinafter, referred to as a glass preform) is inserted into a furnace core tube from an upper end opening of an optical fiber drawing furnace (hereinafter, referred to as a drawing furnace), The front end of the glass base material is heated and melted to reduce the diameter, whereby the glass base material is drawn from below the drawing furnace. At this time, the temperature in the drawing furnace is as high as about 2000 ° C., and therefore, carbon having excellent heat resistance is used for components in the drawing furnace.

  In this case, the inside of the drawing furnace is set to a positive pressure to prevent outside air (oxygen) from entering the inside of the drawing furnace, but the airtightness is well established in the gap between the upper opening of the drawing furnace and the glass base material. If not (unsealed), outside air is drawn into the drawing furnace, which affects the life of the drawing furnace. For example, Patent Literatures 1 and 2 disclose a technology of a seal structure for closing a gap between an upper end opening of a drawing furnace and a glass base material.

JP 2012-106915 A JP 2014-152083 A

By the way, since the blade member of Patent Document 1 is formed so as to constantly press the side surface of the glass base material, the load on the blade member increases. On the other hand, according to the blade member of Patent Literature 2, the load on the blade member can be reduced because the blade member can be moved in the radial direction of the glass base material by supplying and discharging the gas into and from the internal space of the housing. .
However, if the blade member does not move to the expected position, the drawing operation may be affected. In particular, when at least one of the plurality of blade members is not opened, the glass base material and the seal structure are damaged when the glass base material is inserted or removed. Therefore, in order to prevent breakage of the glass base material and the seal structure beforehand, it is desirable to operate the blade member after detecting the completion of the opening / closing operation of the blade member.

  The present invention has been made in view of the above circumstances, and has as its object to provide a seal structure of an optical fiber drawing furnace capable of detecting completion of opening and closing operations of a blade member, and a method of manufacturing an optical fiber. .

  The seal structure for an optical fiber drawing furnace according to one embodiment of the present invention closes a gap between an upper end opening of the optical fiber drawing furnace and an optical fiber glass base material inserted from the upper end opening. A plurality of blade members provided so as to abut on the circumferential side surface of the glass base material for optical fiber, the blade member is housed, and the blade member A guide member movably supported, a push-pull action mechanism for moving the blade member in a radial direction of the optical fiber glass preform, and an action detection mechanism detecting that the operation of the push-pull action mechanism is completed. , Is provided.

  According to the above, it is possible to prevent the glass base material and the seal structure from being damaged when the glass base material is inserted or removed.

It is a figure explaining the outline of the drawing furnace for optical fibers by one embodiment of the present invention. It is a figure showing the seal structure of the 1st example. FIG. 3 is a diagram illustrating a blade member and a guide member of FIG. 2. FIG. 4 is a sectional view taken along line IV-IV of FIG. 2. It is a figure showing the seal structure of the 2nd example. It is a figure showing the seal structure of the 3rd example. It is a figure showing the seal structure of the 4th example and the 5th example.

[Description of Embodiment of the Present Invention]
First, the contents of the embodiment of the present invention will be listed and described.
The seal structure for an optical fiber drawing furnace according to one embodiment of the present invention is as follows: (1) The space between the upper end opening of the optical fiber drawing furnace and the glass base material for an optical fiber inserted from the upper end opening. A seal structure of an optical fiber drawing furnace for closing the gap, a plurality of blade members provided so as to contact the circumferential side surface of the optical fiber glass preform, accommodating the blade members, A guide member that movably supports the blade member, a push-pull action mechanism that moves the blade member in the radial direction of the optical fiber glass preform, and an operation that detects completion of the operation of the push-pull action mechanism A detection mechanism. Since the operation detection mechanism is provided, it is possible to detect that the operations of the push-pull action mechanisms of all blade members are completed. Therefore, breakage of the glass base material and the seal structure at the time of insertion and removal of the glass base material can be prevented.

(2) The operation detection mechanism is provided for each of the blade members. This makes it possible to reliably detect that the operations of the push-pull action mechanisms of all the blade members have been completed.
(3) The push-pull action mechanism moves the blade member in the radial direction of the optical fiber glass base material by supplying or discharging gas from the internal space of the guide member. Accordingly, the opening or closing operation of the blade member can be easily performed using the gas.
(4) The operation detection mechanism detects a pressure or a flow rate of a gas passage communicating with the internal space of the guide member. This makes it possible to detect that the opening or closing operation of the blade member has been completed.
(5) The operation detection mechanism detects an end position of the blade member. This makes it possible to detect that the opening or closing operation of the blade member has been completed.
(6) The operation detection mechanism is sandwiched between the blade member and the guide member to detect pressure. This makes it possible to detect that the opening or closing operation of the blade member has been completed.
(7) The operation detection mechanism detects that the opening operation of the blade member has been completed. By detecting the opening operation, it is possible to prevent the glass base material and the seal structure from being damaged when the glass base material is inserted or removed.
(8) The operation detection mechanism detects that the closing operation of the blade member has been completed. The airtightness of the drawing furnace can be reliably maintained by detecting the closing operation.
(9) An optical fiber manufacturing method in which an optical fiber is drawn by using the seal structure of the optical fiber drawing furnace. Since the above-described seal structure is used, breakage of the glass base material and the seal structure at the time of inserting and removing the glass base material can be prevented.

[Details of Embodiment of the Present Invention]
Hereinafter, preferred embodiments of a seal structure of an optical fiber drawing furnace and an optical fiber manufacturing method according to the present invention will be described with reference to the accompanying drawings. In the following, a resistance furnace in which a furnace tube is heated by a heater will be described as an example, but the present invention is also applicable to an induction furnace in which a high-frequency power is applied to a coil and the furnace tube is induction-heated. Also, the mechanism for suspending the glass base material and the configuration of the heat insulating material are described below by way of example, and the present invention is not limited thereto.

  FIG. 1 is a diagram schematically illustrating an optical fiber drawing furnace according to an embodiment of the present invention. The drawing furnace 1 includes a furnace housing 2, a furnace tube 3, a heating source (heater) 4, and a seal structure 10. The furnace housing 2 has an upper end opening 2a and a lower end opening 2b, and is made of, for example, stainless steel. The furnace tube 3 is formed in a cylindrical shape at the center of the furnace housing 2 and communicates with the upper end opening 2a. The furnace tube 3 is made of carbon, and the glass base material 5 is inserted into the furnace tube 3 from the upper end opening 2 a while being sealed by the seal structure 10.

  In the furnace housing 2, a heater 4 is arranged so as to surround the furnace tube 3, and a heat insulating material 7 is housed so as to cover the outside of the heater 4. The heater 4 heats and melts the glass base material 5 inserted into the furnace tube 3, and causes the optical fiber 5b whose diameter has been reduced from the lower end 5a to hang down. The glass preform 5 can be moved in the drawing direction (downward direction) by a separately provided moving mechanism, and a support bar 6 for suspending and supporting the glass preform 5 is provided above the glass preform 5. Are connected. The drawing furnace 1 is provided with a furnace gas supply mechanism (not shown) using an inert gas or the like. The inert gas or the like for preventing oxidation and deterioration is provided inside the furnace tube 3 and around the heater 4. Can be supplied.

  Although FIG. 1 shows an example in which the upper end of the inner wall of the furnace tube 3 forms the upper end opening 2a as it is, the present invention is not limited to this. For example, an upper lid, which is an upper end opening narrower than the inner diameter d of the furnace tube 3, may be provided above the furnace tube 3. In this case, the gap to be sealed is formed by the narrow upper opening and the glass base material 5. Between the two. Although the cross-sectional shape of the glass base material 5 is basically generated with the aim of obtaining a perfect circle, a non-circle may exist partially regardless of the accuracy, and the cross-sectional shape may be elliptical. You may. In addition, the cross section of the upper end opening 2a may be circular, but the accuracy is not limited.

  One embodiment of the present invention is directed to a seal structure 10 for closing a gap S between an upper end opening 2a of a drawing furnace 1 and an outer periphery of a glass base material 5 inserted from the upper end opening 2a. In particular, the glass base material 5 in the drawing furnace is heated by the heater 4 while the outside air outside the furnace is not entrained by the seal structure 10 provided in the upper end opening 2a.

Hereinafter, an example of the seal structure will be described with reference to FIGS. FIG. 2 is a view showing a seal structure of a first example, FIG. 3 is a view for explaining a blade member and a guide member of FIG. 2, and FIG. 4 is a sectional view taken along line IV-IV of FIG.
The seal structure 10 includes a plurality of blade members 14 and 15 having heat resistance, a guide member 17 that accommodates the blade members 14 and 15 and linearly slides and moves the blade members 14 and 15, And a mechanism (hereinafter, referred to as a push-pull action mechanism) having an action of pressing the blade members 14 and 15 inward or outward by utilizing a pressure difference. Have.

  As shown in FIG. 2, the housing 11 is a disk-shaped member having concentric through holes, and allows the blade member 15 to pass through as shown in FIG. 3A in which a part of FIG. 2 is enlarged. As shown in FIG. 3B, which is a cross-sectional view deeper than FIG. 3A, an opening 11 b for inserting the blade member 14 is provided on the inner peripheral surface of the housing 11. , For example, are provided alternately. The housing 11 is made of, for example, stainless steel, and cools the blade members 14 and 15 to, for example, 400 ° C. or less (preferably 300 ° C. or less in the case of a carbon blade member). A mechanism (for example, a water cooling system) may be provided.

  The blade members 14 and 15 extend radially with respect to the central axis of the housing 11 and are installed in the housing 11. A plurality of blade members 14 are provided at equal intervals along the inner peripheral surface of the housing 11. Also, a plurality of blade members 15 are provided at equal intervals along the inner peripheral surface of the housing 11. The blade members 14 and 15 have, for example, a substantially rectangular parallelepiped shape in which the cross-sectional shape in a plane perpendicular to the moving direction is substantially rectangular, and are arranged alternately in two upper and lower stages.

Further, as shown in FIG. 3, the blade members 14 and 15 protrude from the housing 11 and can be in contact with the side surfaces of the glass base material. The outer peripheral surface portions 14b and 15b of the four side surfaces that slide and slide, and the rear end portions 14c and 15c arranged in an operating pressure applying space 40 described later.
When the tip portions 14a and 15a come into contact with the side surfaces of the glass base material, it is necessary to minimize the gap between the front end portions 14a and 15a and the glass base material. For this reason, it is preferable that the tips of the tip portions 14a and 15a have an arc shape having a curvature that matches the maximum value (the maximum diameter of the glass base material used) assumed as the radius of the glass base material.

  When the tips 14a and 15a abut against the side surface of the glass base material, no gap is formed between the tips 14a and 15a in the vertical direction, and furthermore, the gap created between the adjacent tips 14a. Is filled in with the tip 15a, and the gap generated in the adjacent tip 15a is filled with the tip 14a. Thereby, the gap S in FIG. 1 can be closed, and sealing can be performed so that outside air is not drawn into the furnace.

  The material of the blade members 14, 15 is preferably carbon. Carbon is not only excellent in heat resistance, but also a soft material, so there is no fear of damaging the glass base material. In particular, it is preferable to use soft carbon having a Shore hardness of 100 or less for the blade members 14 and 15 of this embodiment. In addition, carbon is preferable in that it can be easily formed by press molding or shaving.

Further, as a material of the blade members 14 and 15, for example, quartz glass, SiC-coated carbon, or the like can be adopted in addition to carbon. Even when another hard material is used, it is possible to prevent the glass base material from being damaged, for example, by using soft carbon only in the tip portion alone.
The width and the number of the blade members 14 and 15 described above may be appropriately selected according to the outer diameter of the glass base material to be used, the amount of change in the outer diameter, the amount of bending, and the like.

  The guide member 17 is formed, for example, in a cylindrical shape through which the outer peripheral surface portions 14b, 15b of the blade members 14, 15 are inserted, and is installed on the bottom surface of the housing 11, for example. More specifically, as shown in FIG. 3B, the guide member 17 has four sliding surfaces 17c that divide the working pressure application space 40, and the sliding surfaces 17c are provided on the outer peripheral surface 14b of the blade member 14. It is configured to be able to abut from the surroundings. Further, as shown in FIG. 3A, the sliding member 17 also has four sliding surfaces 17 b that divide the working pressure application space 40 at a position lower than the sliding surface 17 c. It is configured to be able to contact the surface portion 15b from the periphery.

The material of the guide member 17 is also preferably carbon. However, in the case of a metal such as boron nitride (BN), a metal such as stainless steel or molybdenum disulfide (MoS ₂ ) may be employed. Alternatively, a metal having an oxide film, a metal having various coatings such as a fluorine coat, a gold plating, a chromium nitride coat, a DLC (diamond-like carbon) coat, or a quartz glass may be used. Note that, similarly to the case, the guide member 17 preferably has a cooling mechanism (for example, a water cooling system) for preventing the carbon blade member from being oxidized and degraded.

  As shown in FIG. 3, the housing 11 is provided with supply / discharge ports 12 a and 12 b for connecting the working pressure application space 40 in the guide member 17 to the outside of the housing 11 and introducing air from the outside. The gas from the gas supply unit 21 shown in FIG. 2 can be stored in the working pressure application space 40. Further, the gas accumulated in the working pressure application space 40 can be discharged (sucked out) from the gas discharge part 22 shown in FIG. 2 through the supply / discharge ports 12a and 12b. It should be noted that even if the blade member is operated in the same direction as when suction is performed by applying pressure to the opposite end surface of the blade member without pushing the gas in the operating pressure applying space 40 and pushing the blade member in the opposite direction. Good.

  The pressures of the supply / discharge ports 12a and 12b are detected by the pressure sensors 60a and 60b shown in FIG. The gas supply unit 21 and the gas discharge unit 22 are electrically connected to the controller 20. The supply / discharge ports 12a and 12b correspond to a part of the gas passage of the present invention, the pressure sensors 60a and 60b correspond to the operation detecting mechanism of the present invention, and the controller 20, the gas supply unit 21 and the gas discharge unit 22 correspond to each other. This corresponds to the push-pull action mechanism of the present invention.

  Note that the push-pull action mechanism can individually press the plurality of blade members 14 and 15 in the radial direction of the glass base material (more precisely, in the radial direction of the housing 11), and the distal end portions 14 a of the blade members 14 and 15. , 15a are brought into contact with the side surfaces of the glass base material. This pressing force is weak enough not to hinder the lowering of the glass base material.

  When the controller 20 described in FIG. 2 outputs a drive signal to the gas supply unit 21 based on an instruction from an operator or the like, the gas is supplied to the supply / discharge port 12a described in FIG. 3A or described in FIG. 3B. The pressure is supplied to each working pressure application space 40 through the supply / discharge port 12b. The operating pressure applying space 40 is pressurized and becomes a positive pressure atmosphere (pressure P1: for example, +1000 Pa to +5000 Pa> the pressure of the furnace internal pressure space 30) with respect to the furnace internal pressure space. The blade members 14 and 15 are moved closer to the side surface of the glass base material (close operation) by a pressure difference from 30, and the blade members 14 and 15 are brought into contact with the side surfaces of the glass base material.

As the drawing progresses, the glass base material 5 descends as shown by the arrow in FIG. 2, and when the outer diameter of the glass base material 5 increases, for example, from φ1 to φ2 (> φ1), the blade members 14 and 15 Continue to abut on the side of base material 5. Conversely, even when the outer diameter of the glass base material 5 decreases, the blade members 14 and 15 abut the side surfaces of the glass base material 5 due to the pressing force of the gas in the working pressure application space 40.
When the closing operation of all the blade members 14 and 15 is not completed, the pressure in the furnace pressure space 30 decreases. Therefore, by measuring the pressure in the furnace pressure space 30, the controller 20 determines whether or not the closing operation of all the blade members 14, 15 has been completed (whether or not the blade members 14, 15 are in the closed state). ) Can be determined.

  On the other hand, when the controller 20 outputs a drive signal to the gas discharge unit 22, the gas accumulated in each operating pressure applying space 40 is supplied to the supply / discharge port 12a described in FIG. 3A or described in FIG. 3B. It is discharged out of the housing 11 through the supply / discharge port 12b. The operating pressure applying space 40 is decompressed and becomes a negative pressure atmosphere (pressure P2: for example, −1000 Pa to −5000 Pa <the pressure of the furnace internal pressure space 30) with respect to the furnace internal pressure space. The blade members 14, 15 are moved away from the side surface of the glass base material (opening operation) by the pressure difference from the space 30, and the blade members 14, 15 are separated from the side surface of the glass base material.

  The pressure sensors 60a and 60b detect the pressures of the supply / discharge ports 12a and 12b, and the rear ends 14c and 15c of the blade members 14 and 15 illustrated in FIG. 3 close the supply / discharge ports 12a and 12b, respectively. Thus, it is possible to detect that the pressure in the working pressure applying space 40 changes to a negative pressure equal to or lower than a certain level with respect to the furnace pressure space. Therefore, the controller 20 determines whether or not the opening operation of the blade members 14 and 15 has been completed (the blade members 14 and 15 are in the open state) when the negative pressure becomes equal to or lower than the certain level. . If the operating pressure application spaces 40 for pushing and pulling the blade members are connected to each other, the completion of the opening operation of all the blade members can be detected by monitoring the pressure values in the spaces.

Since the pressure sensor is provided in this manner, it is possible to detect that the opening and closing operations of all the blade members have been completed. Therefore, breakage of the glass base material and the seal structure at the time of inserting or removing the glass base material can be prevented.
As shown in FIG. 3, it is more preferable to provide sheet-like packings 61a, 61b surrounding the openings of the supply / discharge ports 12a, 12b on the inner wall surface of the housing 11. In this case, when the rear ends 14c, 15c close the supply / discharge ports 12a, 12b with the packings 61a, 61b interposed therebetween, the differential pressure when changing from positive pressure to negative pressure becomes larger, and the blade member 14, 15 can be determined more clearly.

Further, instead of the above pressure sensor, a flow rate sensor that detects the amount of exhaust gas flowing from the supply / discharge port to the outside of the housing may be used. Also in this case, it is possible to reliably detect that all the blade members have been opened.
It should be noted that it may be used in combination with a position sensor or the like, which will be described later, and if used together, the completion of the opening operation of all blade members can be detected more reliably.

Subsequently, another embodiment will be described. FIG. 5 is a diagram showing a seal structure of a second example, FIG. 6 is a diagram showing a seal structure of a third example, and FIG. 7 is a diagram showing seal structures of a fourth example and a fifth example. The following description will be made with the same cross section as the blade member 14 described with reference to FIG.
In the example shown in FIG. 5, a position sensor (corresponding to the operation detecting mechanism of the present invention) is used. Specifically, a protrusion 14d is formed on the rear end 14c of the blade member 14. The protrusion 14 d extends in a substantially horizontal direction, and a rear end portion thereof is exposed outside the housing 11. Note that the blade member 15 also has a protrusion 15d that is exposed outside the housing 11. It is preferable that the gap between the projections 14d and 15d and the housing 11 be airtight by packing or the like.

Outside the housing 11, position sensors 62a and 62b are installed. The position sensors 62a and 62b are, for example, capacitance type proximity switches, and can detect the presence or absence of an object in a non-contact state. In addition, in addition to the capacitance type, a proximity switch of a high frequency oscillation type, a magnetic type, an ultrasonic type, a radio wave type, a pneumatic type, a photoelectric type, and an optical fiber type may be used.
When the protrusions 14d and 15d are provided, the completion of the operation of the blade members 14 and 15 can be determined visually by an operator, but the controller 20 illustrated in FIG. When the protrusions 14d and 15d are detected by the position sensors 62b and 62a, it is determined that the opening operation of the blade members 14 and 15 is completed.

Next, in the example shown in FIG. 6, a pressure sensor (corresponding to the operation detecting mechanism of the present invention) is used. Specifically, a protrusion 14e is formed on the rear end 14c of the blade member 14. The protrusion 14 e extends vertically downward, for example, and its lower end portion is in contact with the guide member 17.
A pressure sensor 63 is installed on the inner wall surface of the housing 11, for example, near the supply / discharge port 12a. Note that the pressure sensor 63 may be a proximity switch. Then, the controller determines that the opening operation of the blade member 14 is completed when the blade member 14 retreats and the pressing force due to the contact with the protrusion 14e exceeds a predetermined value.
Although illustration of the blade member 15 is omitted, a protrusion extending vertically upward, for example, is formed at a rear end portion thereof, and the blade member 15 is brought into contact with a pressure sensor installed on the inner wall surface of the housing 11 so as to contact the blade member 15. Completion of the opening operation of the member 15 can also be determined by the controller.

  By the way, if it is desired to detect the completion of the closing operation of the blade member, another pressure sensor may be used. More specifically, as shown in FIG. 7A, a pressure sensor 64 different from the pressure sensor 63 is provided on the guide member 17 at a position facing the pressure sensor 63 in the horizontal direction. When the opening operation is detected by the pressure sensor 63 and the diameter of the glass base material is constant, the controller determines when the blade member 14 advances and the pressing force due to the contact with the protrusion 14e exceeds a predetermined value. Can be determined that the closing operation of the blade member 14 has been completed.

  Alternatively, another pressure sensor (not shown) for detecting the pressure of the opening 13 shown in FIG. 7B may be used. In this case, another communication passage 65 communicating with the communication passage 17a and the opening 13 is opened at a position facing the supply / discharge port 12a in the horizontal direction in the guide member 17. Note that a packing 66 surrounding the opening of the communication passage 65 is provided on the inner wall surface of the guide member 17. When the opening operation is detected, the blade member 14 moves forward, and when the projection 14e closes the communication passage 65 with the packing 66 interposed therebetween, the pressure in the furnace pressure space is changed from a positive pressure to a negative pressure of a certain level or less. Therefore, the controller can determine at that time that the closing operation of the blade member 14 has been completed.

  The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 ... Drawing furnace for optical fiber, 2 ... Furnace housing, 2a ... Upper opening part, 2b ... Lower opening part, 3 ... Furnace tube, 4 ... Heater, 5 ... Glass base material for optical fiber, 5a ... Lower part part, 5b: optical fiber, 6: support rod, 7: heat insulating material, 10: seal structure, 11: housing, 11a, 11b: opening, 12a, 12b: supply / discharge port, 13: opening, 14, 15: blade member .., 14a, 15a... Tip, 14b, 15b... Outer peripheral surface, 14c, 15c... Rear end, 14d, 14e, 15d. Surface, 20: controller, 21: gas supply unit, 22: gas discharge unit, 30: furnace pressure space, 40: operating pressure application space, 60a, 60b, 63, 64: pressure sensor, 61a, 61b, 66: packing , 62a, 62b... .

Claims (9)

A seal structure of an optical fiber drawing furnace for closing a gap between an upper end opening of the optical fiber drawing furnace and a glass base material for an optical fiber inserted from the upper end opening,
A plurality of blade members provided so as to be in contact with a circumferential side surface of the glass preform for optical fiber; a guide member which accommodates the blade members and movably supports the blade members; and A sealing structure for an optical fiber drawing furnace, comprising: a push / pull action mechanism for moving the fiber glass preform in the radial direction; and an operation detection mechanism for detecting completion of the operation of the push / pull action mechanism. .   The seal structure for an optical fiber drawing furnace according to claim 1, wherein the operation detection mechanism is provided for each of the blade members.   3. The optical fiber according to claim 1, wherein the push / pull action mechanism moves the blade member in a radial direction of the glass base material for optical fiber by supplying or discharging gas in an internal space of the guide member. 4. Sealing structure for drawing furnace.   The seal structure for an optical fiber drawing furnace according to any one of claims 1 to 3, wherein the operation detection mechanism detects a pressure or a flow rate of a gas passage communicating with the internal space of the guide member.   The seal structure of an optical fiber drawing furnace according to any one of claims 1 to 4, wherein the operation detection mechanism detects an end position of the blade member.   The seal structure for an optical fiber drawing furnace according to any one of claims 1 to 4, wherein the operation detection mechanism is sandwiched between the blade member and the guide member to detect pressure.   The seal structure of the optical fiber drawing furnace according to any one of claims 1 to 6, wherein the operation detection mechanism detects that the opening operation of the blade member has been completed.   The seal structure of an optical fiber drawing furnace according to any one of claims 1 to 7, wherein the operation detection mechanism detects that the closing operation of the blade member has been completed. An optical fiber manufacturing method, wherein an optical fiber is drawn using the seal structure of the optical fiber drawing furnace according to claim 1.

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