JP2020026355A - Lower lid body, heating furnace, and optical fiber preform replacement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To replace a lower lid body which can be mounted on a heating furnace and can prevent the pressure in the heating furnace from exceeding a certain value by a simple mechanism, a heating furnace provided with the lower lid body, and an optical fiber base material. Provide a method. SOLUTION: The lower lid 30 is provided with an upper opening 25 into which an optical fiber base material 10 is inserted in the upper part of a wire drawing furnace 20, and the upper opening 25 seals between the optical fiber base material 10 and the lower opening 25. The sealing mechanism 26 is provided, and is mounted on the drawing furnace provided with the lower opening 28 for taking out the optical fiber 11 at the lower part of the drawing furnace 20. The lower lid 30 has a pressure relief valve mechanism provided with a valve for releasing the gas in the drawing furnace when the gas pressure in the drawing furnace 20 becomes a predetermined value or more. [Selection diagram] Fig. 1

Description

  The present invention relates to a lower lid, a heating furnace, and an optical fiber preform replacement method.

  At the upper part of the drawing furnace of the wire drawing machine for manufacturing optical fibers, there is an insertion port for a glass base material for optical fiber (hereinafter, referred to as an optical fiber base material), and the atmosphere gas in the furnace is not unnecessarily released. Thus, a sealing mechanism is required. Conventionally, a gas is blown into a gap between an optical fiber preform and an airtight plate provided with a certain gap to seal the gap, or as disclosed in Patent Document 1, a material such as graphite or quartz glass is used. A method of sealing by contacting with an optical fiber preform has been adopted. Further, a sealing method using graphite sealing pieces has also been proposed.

JP 2006-342030 A

  When the optical fiber preform is set in the drawing furnace at the start of drawing or when the optical fiber preform is removed at the end, the upper opening is released in a heated state. Since carbon parts are used as furnace components, it is necessary to prevent oxidation in the furnace. FIG. 4 is a view for explaining a method for taking out an optical fiber preform at the time of completion of drawing using a conventional heating furnace. At the time of drawing, as shown in FIG. 4A, the optical fiber 11 is drawn by heating the optical fiber preform 10 inserted into the core tube 21 of the drawing furnace 20 by the heater 22. The optical fiber preform 10 is inserted into the furnace through the upper opening 25 of the drawing furnace 20, and is taken out from the upper opening 25 when the drawing is completed.

  At this time, in order to avoid mixing of the air flowing into the furnace, the gas purge amount in the furnace is increased in advance, and the lower opening 29 at the lower part of the drawing furnace is closed with a lid 40 as shown in FIG. It was blocking. Then, as shown in FIG. 4 (C), the drawn optical fiber preform 10 is taken out of the furnace, and a new optical fiber preform 10 is inserted into the furnace, thereby keeping the furnace at an elevated temperature. This enabled continuous drawing while standing.

  However, as shown in FIG. 4B, the lower opening 29 of the drawing furnace is closed with a lid 40, and a sealing mechanism 26 such as a blade shutter provided on the upper part of the drawing furnace closes the gap with the optical fiber preform. If the amount of gas purge in the furnace is increased in the sealed state, the internal pressure in the furnace increases, and the seal mechanism 26 in the upper part of the drawing furnace, which has relatively low strength, may be broken. For this reason, the amount of gas purge in the furnace had to be adjusted while detecting the internal pressure in the furnace.

  The present invention has been made in view of these circumstances, and is provided with a lower lid body that can be mounted on a heating furnace and that can prevent the pressure in the heating furnace from reaching a certain value or more, and the lower lid body. It is an object of the present invention to provide a heating furnace and an optical fiber preform replacement method.

In order to solve the above problems, a lower lid according to one embodiment of the present invention has an upper opening in which an object to be heated is inserted in an upper part of a furnace, and a lower opening in which the object to be heated is taken out in a lower part of the furnace. A lower lid mounted on a heating furnace having a sealing mechanism for sealing between the upper opening and the object to be heated, wherein the lower lid is mounted on the lower opening and a gas pressure in the furnace is equal to or higher than a predetermined value. It has a pressure relief valve mechanism to release gas in the furnace when it becomes.
Further, a heating furnace according to one embodiment of the present invention includes the above-described lower lid.

  An optical fiber preform replacement method according to an aspect of the present invention is an optical fiber preform replacement method for replacing an optical fiber preform disposed in a heating furnace, wherein the heating furnace has an upper opening. And a sealing mechanism for sealing between the lower opening and the optical fiber preform inserted into the upper opening from the upper opening, and replaces the optical fiber preform inserted into the heating furnace. Mounting the lower lid, and removing the optical fiber preform inserted into the heating furnace while the gas pressure in the furnace is increased, wherein the lower lid comprises the furnace A pressure relief valve mechanism for releasing gas in the furnace when the gas pressure in the furnace becomes equal to or higher than a predetermined value.

  According to the present invention, since it is possible to prevent the pressure in the heating furnace from becoming a fixed value or more, it is not necessary to adjust the pressure while detecting the internal pressure, for example, when exchanging the optical fiber preform. This prevents the in-furnace components from being broken while preventing the inflow of air.

It is a figure for explaining a method at the time of taking out an optical fiber preform at the time of completion of drawing in a heating furnace provided with a lower lid concerning an embodiment of the present invention. It is a figure showing the schematic section of the lower lid concerning one embodiment of the present invention. It is a figure showing the schematic section of the lower lid concerning other embodiments of the present invention. It is a figure for explaining the method at the time of taking out the optical fiber preform at the time of drawing completion using the conventional heating furnace.

(Description of the embodiment of the present invention)
First, embodiments of the present invention will be listed and described.
(1) The lower lid according to one aspect of the present invention includes an upper opening into which an object to be heated is inserted at the upper part of the furnace, a lower opening at which the object to be heated is taken out at the lower part of the furnace, and an upper opening. A lower lid attached to a heating furnace having a seal mechanism for sealing between the object to be heated, the lower lid being attached to the lower opening, and when a gas pressure in the furnace becomes a predetermined value or more, the furnace It has a pressure relief valve mechanism to release gas inside.

  As a result, the pressure in the heating furnace can be prevented from reaching a predetermined value or more, so that when the optical fiber preform is replaced, the in-furnace components can be broken while preventing the air from flowing into the heating furnace. Disappears.

(2) an arm rotatably supported by the lower lid body, a valve provided at one end of the arm for closing the lower opening, and a pressure relief valve mechanism at the other end of the arm. It has a weight provided.
This simplifies the structure of the pressure relief valve mechanism and enables fine adjustment of the furnace pressure by adjusting the position of the weight.

(3) an arm rotatably supported by the lower lid body, a valve provided at one end of the arm to close the lower opening, and a pressure relief valve mechanism at the other end of the arm. It may have a spring provided.
Thereby, one form of the pressure relief valve mechanism can be provided.

(4) The heating furnace according to one embodiment of the present invention is a heating furnace provided with the above-described lower lid, and (5) the heating furnace can be adjusted in an internal pressure range of 100 Pa or more and 1000 Pa or less. (6) The heating furnace may be a drawing furnace for producing an optical fiber, and (7) the heating furnace may be a drawing furnace for producing an optical fiber preform.
Thereby, the pressure in the heating furnace can be prevented from becoming equal to or more than a certain value, and the value can also be adjusted, so that the air can be prevented from flowing into the heating furnace when the optical fiber preform is replaced. In addition, the parts in the furnace are not broken.

  (8) An optical fiber preform replacement method according to an aspect of the present invention is an optical fiber preform replacement method for replacing an optical fiber preform disposed in a heating furnace, wherein the heating furnace has an upper opening. Part, a lower opening, a seal mechanism for sealing between the optical fiber preform inserted from the upper opening to the upper opening, the optical fiber preform inserted into the heating furnace At the time of replacement, the step of mounting the lower lid, and, with the gas pressure in the furnace increased, the step of taking out the optical fiber preform inserted into the heating furnace, the lower lid, the lower lid, A pressure relief valve mechanism for releasing gas in the furnace when the gas pressure in the furnace becomes equal to or higher than a predetermined value;

  This makes it possible to prevent the pressure in the heating furnace from reaching a certain value or more when exchanging the optical fiber preform, thereby preventing the inflow of air into the heating furnace and breaking the components in the furnace. Disappears.

(Details of the embodiment of the present invention)
Hereinafter, preferred embodiments of the lower cover, the heating furnace, and the optical fiber preform replacement method of the present invention will be described with reference to the drawings. In the following description, configurations denoted by the same reference numerals in different drawings are the same, and description thereof may be omitted. It should be noted that the present invention is not limited to the exemplifications of these embodiments, but includes all changes within the scope of the matters described in the claims and within the equivalent scope. Further, the present invention includes a combination of any of the embodiments, as long as a combination of a plurality of embodiments is possible.

(First embodiment)
In the following description, as a heating furnace provided with a lower lid according to an embodiment of the present invention, a case of a drawing furnace will be described by taking as an example a case where an optical fiber preform is taken out of the drawing furnace after drawing is completed. . FIG. 1 is a view for explaining a method of taking out an optical fiber preform at the time of completion of drawing in a heating furnace provided with a lower lid according to an embodiment of the present invention, and FIG. It is a figure showing the schematic section of the lower lid concerning one embodiment.

  As shown in FIG. 1 (A), an optical fiber 11 is heated at its tip while lowering an optical fiber preform 10 mainly composed of quartz from above a drawing furnace 20 for an optical fiber into a furnace tube 21. It is manufactured by melting the optical fiber preform 10, reducing the diameter of the end of the optical fiber preform 10, and taking out the optical fiber 11 from below the drawing furnace 20. After the drawn optical fiber 11 is cooled by a cooling device (not shown), its outer diameter is measured by an outer diameter measuring device, and subsequently, the surface is protected by a resin layer to become an optical fiber element wire, which is formed into a bobbin or the like. It is wound up. Note that the optical fiber preform corresponds to the object to be heated in the present invention.

  The drawing furnace 20 includes a furnace tube 21, a heater 22 arranged to surround the furnace tube 21, and a heat insulating material 23 housed between the outside of the heater 22 and the housing 24. The heater 22 heats and melts the optical fiber preform 10 inserted into the furnace tube 21, and causes the melted and reduced optical fiber 11 to hang from the lower chamber 28. At this time, the temperature in the drawing furnace 20 is as high as about 2000 ° C., and therefore, for example, carbon having excellent heat resistance is used for the components in the drawing furnace 20.

  Carbon has a property of being oxidized and consumed in a high-temperature oxygen-containing atmosphere. For this reason, the inside of the drawing furnace 20 needs to be maintained in an atmosphere of a rare gas such as an argon gas or a helium gas, or a nitrogen gas (hereinafter, referred to as an inert gas or the like). Therefore, a sealing mechanism 26 is provided above the drawing furnace 20 to seal the gap between the upper opening 25 into which the optical fiber preform 10 is inserted and the optical fiber preform 10, and to prevent the gap from the upper gas inlet 27 through the upper gas inlet 27. An active gas or the like is sent into the furnace tube 21 to maintain the inside of the furnace tube 21 at a positive pressure, thereby preventing outside air (oxygen) from entering the drawing furnace 20.

  In addition, a lower chamber 28 having a shutter (not shown) is provided below the drawing furnace 20, for example. At the time of drawing, the opening of the shutter is narrowed down to a minimum size that can pass through the optical fiber 11, so that the drawing furnace 20 is drawn. It prevents the inflow of air into the interior. Although FIG. 1 illustrates an example in which the gas inlet for the inert gas or the like has only the upper gas inlet 27, a lower gas inlet may be provided below the drawing furnace 20.

  Here, referring to FIG. 1A, as shown in the figure, the optical fiber preform 10 is inserted into the drawing furnace 20 through an upper opening 25 serving as a preform supply port above the drawing furnace 20. You. On the upper side of the optical fiber preform 10, for example, a dummy member 12 is fixed, and the optical fiber preform 10 is inserted and lowered into the core tube 21 by a suspension device (not shown) with which the dummy member 12 is engaged. Then, the drawing process proceeds, and as shown in FIG. 1A, when the optical fiber preform 10 is shortened to a predetermined length, the drawing process is terminated, and the optical fiber preform 10 is removed from the drawing furnace 20. Remove and replace with a new optical fiber preform. In the drawing step shown in FIG. 1A, the diameter of the dummy member 12 is made substantially the same as the diameter of the optical fiber preform 10, and the entire optical fiber preform 10 is inserted into the drawing furnace 20. At this time, the dummy member 12 is sealed by the sealing mechanism 26, but other sealing mechanisms may be used as long as the upper opening of the drawing furnace 20 is sealed at the time of drawing. .

  When exchanging the optical fiber preform 10 in the drawing furnace 20, the optical fiber preform 10 is inserted into the drawing furnace 20 as shown in FIG. A lower lid 30 having a pressure relief valve mechanism is attached to the lower opening 29 of the drawing furnace 20 while maintaining a state in which 25 is sealed by the seal mechanism 26. At the time of mounting, an inert gas or the like is continuously supplied into the drawing furnace 20 as in the case of drawing. Next, with the pressure inside the drawing furnace 20 increased, the optical fiber preform 10 is removed from the drawing furnace 20 as shown in FIG. Then, a new optical fiber preform 10 to be drawn next is inserted into the drawing furnace 20, and after sealing with the seal mechanism 26, the lower cover 30 is removed.

  The lower lid 30 is attached so as to close the lower opening 29 of the lower chamber 28 as shown in FIG. In this embodiment, for example, the mounting flange 28a provided on the lower chamber 28 and the flange 30a provided on the lower lid 30 are abutted with each other, and both are fixed by the clamp member 50. The lower lid 30 may be mounted using other mounting structures such as screwing and hooks other than this mounting structure.

  The lower lid 30 has a through hole 31 at the center thereof communicating with the lower opening 29, and a valve 33 for closing a lower portion of the through hole 31 is provided. The valve 33 is provided at one end of an arm 34 supported by a shaft 35 at a position of an arm support 32 provided integrally with the lower lid 30. A weight 36 is provided at the other end of the arm 34 opposite to the valve 33 with respect to the shaft 35. The weight 36 is screwably attached to a screw 37 formed on the other end of the arm 34, and the distance from the shaft 35 can be adjusted. Since the arm 34 is rotatable about the shaft 35, the force with which the valve 33 provided on one side of the arm 34 closes the through hole 31 can be adjusted by adjusting the position of the weight 36.

  This seesaw-type depressurizing valve mechanism can prevent the valve 33 from opening when the pressure in the drawing furnace 20 becomes a predetermined value or more and increasing the pressure in the drawing furnace 20. As described above, the arm 34 rotates around the shaft 35 according to the magnitude of the pressure in the drawing furnace 20 and operates like a seesaw. The pressure relief valve mechanism in the lower cover 30 of the present embodiment is constituted by an arm 34 pivotally supported by the lower cover 30, a valve 33, and a weight 36.

  Actually, the above-mentioned seesaw-type lower cover 30 designed so that the pressure in the drawing furnace 20 could be adjusted to 100 to 1000 Pa was produced, and set to about 500 Pa for use. The drawn optical fiber preform 10 was inserted into the drawing furnace 20, and the lower lid 30 was attached while being sealed by the seal mechanism 26 above the drawing furnace 20. When the pressure inside the furnace gradually increases from the time when the lower lid 30 is attached, and when the purge gas amount is increased to about 10 times the normal drawn state for preventing the air from entering, the valve 33 is opened to exceed 500 Pa and the high-temperature gas Was discharged outside. Next, in this state, the optical fiber preform 10 was pulled out of the drawing furnace 20, and when the upper opening 25 of the drawing furnace 20 was opened, the valve 33 was closed. The optical fiber preform 10 to be drawn next was inserted through the upper opening 25 of the drawing furnace 20, and when the pressure in the furnace increased, the valve 33 was opened again to discharge gas. After confirming that the optical fiber preform 10 was sealed by the sealing mechanism 26 on the upper part of the drawing furnace 20, the seesaw type lower cover 30 was removed. After performing such a work, when the inside of the drawing furnace 20 and the seal mechanism 26 were damaged, no abnormality was found at all.

(Second embodiment)
FIG. 3 is a diagram showing a schematic cross section of a lower lid according to another embodiment of the present invention. In the first embodiment, the lower lid 30 ′ is of a seesaw type using the weight 36, but in the present embodiment, a spring 38 is used. As shown in FIG. 3, the lower lid 30 'is attached so as to close the lower opening 29 of the lower chamber 28 in the same manner as in the first embodiment. The lower cover 30 ′ has a valve 33 attached to one end of an arm 34 pivotally supported by a shaft 35, and a spring 38 provided at the other end of the arm 34 to a spring support portion of the lower cover 30 ′. Mounted between 39 and arm 34. By adjusting the spring coefficient of the spring 38 and the distance of the spring 38 from the shaft portion 35, the force with which the valve 33 closes the through hole 31 is adjusted. Since the lower lid 30 ′ is attached in contact with the lower chamber 28, the temperature becomes high. Therefore, it is desirable that the spring 38 be provided at a certain distance from the lower chamber 28.

  As described above, the embodiment of the present invention has been described. However, the lower lid body is not attached to only the drawing furnace, and the furnace body which needs to protect the inside of the furnace with a purge gas for preventing oxidation in a vertical penetration furnace, for example, It is also effective for a drawing furnace for producing an optical fiber preform. Also, an example in which the lower lid is attached to the lower opening 29 of the lower chamber 28 of the drawing furnace 20 has been described. However, the lower lid may be made of another member as long as the lower lid is a lower opening from which an object to be heated is taken out. It may be attached to the opening.

DESCRIPTION OF SYMBOLS 10 ... Optical fiber preform, 11 ... Optical fiber, 12 ... Dummy member, 20 ... Drawing furnace, 21 ... Furnace tube, 22 ... Heater, 23 ... Heat insulating material, 24 ... Housing, 25 ... Upper opening part, 26 ... Sealing mechanism, 27: upper gas inlet, 28: lower chamber, 28a: flange, 29: lower opening, 30, 30 ': lower lid, 30a: flange, 31: through hole, 32: arm support, 33 ... Valve, 34 ... Arm, 35 ... Shaft, 36 ... Weight, 37 ... Screw, 38 ... Spring, 39 ... Spring support, 40 ... Lid, 50 ... Clamp member.

Claims (8)

Heating having an upper opening into which an object to be heated is inserted at the upper part of the furnace, a lower opening at the lower part of the furnace through which the object to be heated is taken out, and a seal mechanism for sealing the object to be heated with the upper opening. A lower lid attached to the furnace,
A lower lid body mounted on the lower opening and having a pressure relief valve mechanism for releasing gas in the furnace when the gas pressure in the furnace becomes a predetermined value or more.   The pressure relief valve mechanism is provided on an arm rotatably supported by the lower lid, a valve provided on one end of the arm to close the lower opening, and provided on the other end of the arm. The lower lid according to claim 1 having a weight.   The pressure relief valve mechanism is provided on an arm rotatably supported by the lower lid, a valve provided on one end of the arm to close the lower opening, and provided on the other end of the arm. The lower lid according to claim 1, further comprising a spring.   A heating furnace provided with the lower lid according to claim 1.   5. The heating furnace according to claim 4, wherein the heating furnace can be adjusted in an internal pressure range of 100 Pa or more and 1000 Pa or less.   The heating furnace according to claim 4, wherein the heating furnace is a drawing furnace for producing an optical fiber.   The heating furnace according to claim 4, wherein the heating furnace is a drawing furnace for producing an optical fiber preform. An optical fiber preform replacement method for replacing an optical fiber preform disposed in a heating furnace,
The heating furnace has an upper opening, a lower opening, and a sealing mechanism that seals between the optical fiber preform inserted into the upper opening from the upper opening,
A step of mounting the lower lid when exchanging the optical fiber preform inserted in the heating furnace,
In a state where the gas pressure in the furnace is increased, having a step of taking out the optical fiber preform inserted into the heating furnace,
The optical fiber preform replacement method, wherein the lower lid has a pressure release valve mechanism for releasing gas in the furnace when the gas pressure in the furnace becomes equal to or higher than a predetermined value.

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