JP2004142988A - Method and apparatus for heating glass body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high quality glass article by preventing intrusion of outside air when a glass body is inserted into a vertical core tube. <P>SOLUTION: In the method for heating the glass body, a seal gas is blown into an insert space 10 from a spit hole 11 away from an opening part 9 positioned at the upper end of a upper cylinder 8 downward by a distance L equal to or above the inside diameter D of the core tube 2 when the glass body 30 is inserted from the upper side of the upper cylinder 8 (insert part) positioned in the upper side of the vertical core tube 2 toward the inside of the core tube 2, so that the glass body 30 inserted into a heating space 5 is heated. <P>COPYRIGHT: (C)2004,JPO

Description

【００３６】
表１及び図４から判るように、距離Ｌが内径Ｄと等しい場合（Ｌ／Ｄ＝１．０）を境として、酸素濃度とＬ／Ｄの関係は急激に変化した。Ｌ／Ｄ＜１．０ではＬ／Ｄの値が大きくなればなるほど酸素濃度は急激に低下し、Ｌ／Ｄ≧１．０ではＬ／Ｄが増加しても酸素濃度はあまり低下せず、Ｌ／Ｄ≧２では酸素濃度はほぼ一定となった。
すなわち、Ｌ／Ｄ＝１．０の点は、Ｌ／Ｄと酸素濃度との関係において臨界的意義を有する点であることが判った。
【００３７】
【発明の効果】
以上説明したように、本発明のガラス体の加熱方法及び加熱装置によれば、縦型の炉心管にガラス体を挿入するときに、外気の侵入を確実に防止することにより、高品質のガラス物品を得ることができる。
【図面の簡単な説明】
【図１】本発明に係るガラス体の加熱方法を実施するための加熱装置を示す概要図である。
【図２】図１に示した加熱装置の第２実施形態を示す概要図である。
【図３】図２に示した加熱装置を用いた線引きの状態を示す概要図である。
【図４】本発明に係る実施例の測定結果を示すグラフである。
【図５】従来の加熱装置を用いた線引きの状態を示す概要図である。
【図６】従来の加熱装置を用いた延伸の状態を示す概要図である。
【符号の説明】
１　ガラス体の加熱装置（第１実施形態）
２　炉心管
３　ヒータ
４　断熱材
５　加熱空間
６　下筒
７　下蓋
８　上筒（挿入部）
９　開口部
１０　挿入空間
１１　吹き出し口
１２　ガス導入部
１３　下部空間
１４　上蓋
２０　ガラス体の加熱装置（第２実施形態）
２１　挿入部
２２　蛇腹状円筒
３０　ガラス体
Ｄ　炉心管の内径
Ｌ　開口部と吹き出し口との距離[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for heating a glass body.
[0002]
[Prior art]
When a glass body is drawn or drawn to produce an optical fiber, the glass body is generally heated and softened by a heating device having a tubular core tube.
When heating the glass body, it is desirable to maintain the inside of the furnace tube in a clean atmosphere in order to prevent impurities that deteriorate the quality from being mixed in or attached to the heated glass body. ing. When a furnace tube made of carbon is used, if heating is performed in an atmosphere containing oxygen, the furnace tube is gradually oxidized and deteriorated. If the core tube deteriorates, dust is generated from the inner surface of the core tube and contaminates the atmosphere inside the core tube, and various measures are taken to prevent oxygen from entering the inside of the core tube. Has been done.
[0003]
As a countermeasure at the time of drawing, as shown in FIG. 5, as shown in FIG. 5, the inner tube 51 and the core tube 51 are connected from the gas inlet 52 of the inner tube 51 connected to the upper end of the vertical tube 50. A method has been proposed in which an inert gas such as helium, nitrogen, or the like is poured into the inside of 50 (for example, see Patent Document 1). In addition, in this method, the upper portion of the inner tube 51 is covered with an upper cover 55 having a hole through which a dummy rod 54 for supporting an optical fiber preform 53 as a glass body can move. To prevent the flow of inert gas.
The optical fiber preform 53 is drawn by heating the vicinity of the lower end of the optical fiber preform 53 with a heater 56 from the outside of the furnace tube 50 to soften the optical fiber preform 53, and pulling out the optical fiber 57 from the lower end of the optical fiber preform 53. Done.
[0004]
As a countermeasure for stretching, as shown in FIG. 6, a bellows-shaped cylinder 62 having a flange 61 through which a dummy rod 60 penetrates is provided above a vertical core tube 63, and during stretching, a glass body is formed. A method of lowering the flange 61 in synchronization with the lowering of the optical fiber preform 64 has been proposed (for example, see Patent Document 2). In this method, the airtightness is maintained by maintaining the clearance between the penetrating dummy bar 60 and the flange 61 without changing the relative position between the flange 61 and the dummy bar 60.
The optical fiber preform 64 is stretched by heating the optical fiber preform 64 by the heater 65 around the furnace tube 63 and controlling the moving speeds of the upper chuck 66 and the lower chuck 67 to tension the optical fiber preform 64. This is done by giving
[0005]
[Patent Document 1]
Japanese Patent No. 2965031 (page 3, FIG. 1)
[Patent Document 2]
JP-A-6-256034 (page 3, FIG. 1)
[0006]
[Problems to be solved by the invention]
By the way, when heating the glass body using the vertical furnace tube as described above, it is necessary to open the upper part of the furnace tube when inserting the glass body into the furnace tube. At that time, the airtightness inside the furnace tube is easily lost.
[0007]
An object of the present invention is to provide a method and apparatus for heating a glass body capable of obtaining a high-quality glass article by reliably preventing outside air from entering when inserting the glass body into a vertical furnace tube. To provide.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the method for heating a glass body according to the present invention is characterized in that when the glass body is inserted toward the inside of the furnace tube from above the insertion portion located above the vertical furnace tube, From the opening located at the upper end of the part, a seal gas is blown out toward the inside of the insertion part from a position below the inner diameter of the furnace tube, away from the inner diameter of the furnace tube, and the glass body is inserted inside the furnace tube. It is characterized by heating a glass body.
Note that an inert gas such as argon (Ar), nitrogen (N), or helium (He) is preferably used as the seal gas.
[0009]
In the above method for heating a glass body, it is preferable that the distance from the opening to the position from which the seal gas is blown out is at least twice the inner diameter of the furnace tube.
[0010]
Further, in the method for heating the glass body, the length of the insertion portion in the vertical direction can be expanded and contracted, and when the glass body is inserted from above the insertion portion, the distance to the position where the sealing gas is blown out from the opening is reduced. It is preferable that the diameter be equal to or larger than the inner diameter of the core tube.
[0011]
Further, the apparatus for heating a glass body according to the present invention for achieving the above object includes a vertical furnace tube, and an insertion portion located above the furnace tube, from an opening located at an upper end of the insertion portion. A blowout port capable of blowing out a seal gas toward the inside of the insertion portion is provided at a position below and at a distance greater than the inner diameter of the furnace tube.
[0012]
Further, in the above-described heating device for a glass body, it is preferable that the insertion portion is configured to be able to expand and contract the length in the vertical direction. For example, it is desirable that the insertion portion is formed in a bellows shape.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a heating method and a heating device for a glass body according to the present invention will be described with reference to FIGS.
(1st Embodiment)
In the first embodiment, when a glass body is inserted into a vertical furnace tube from above, a sealing gas is blown out from a position below the inner diameter of the furnace tube from an opening where the glass body is inserted, and the outside air is blown out. It is characterized by effectively preventing intrusion of heat and heating the inserted glass body.
[0014]
FIG. 1 shows a schematic view of a heating device for a glass body used in the present embodiment.
As shown in FIG. 1, a heating device 1 for a glass body includes a tubular core tube 2 arranged in a vertical shape, and a heater 3 for generating heat in the core tube 2. The periphery of the heater 3 is covered with a heat insulating material 4. The material of the furnace tube 2 is carbon, and the heater 3 can generate heat up to about 2000 ° C. When the glass body 30 is inserted into the heating space 5 inside the furnace tube 2, the glass body 30 can be heated to a desired temperature.
[0015]
Below the furnace tube 2, a lower cylinder 6 forming a lower space 13 continuous with the heating space 5 is provided. Further, a detachable lower lid 7 is attached to a lower end of the lower cylinder.
[0016]
Above the furnace tube 2, an upper tube 8 forming an insertion space 10 continuous with the heating space 5 is provided. The upper tube 8 is an insertion portion for inserting the glass body 30 from the opening 9 at the upper end toward the heating space 5 of the furnace tube 2. An upper lid 14 for opening and closing the opening 9 can be attached to the upper end of the upper cylinder 8.
A plurality of outlets 11 are formed in the upper cylinder 8 so as to be arranged in a row in the circumferential direction. Further, around the upper cylinder 8, there is provided a gas introduction part 12 formed so as to communicate with the outlet 11. The gas introduction unit 12 is connected to a gas control panel (not shown) that supplies a seal gas, and blows out the seal gas supplied from the gas control panel through the outlet 11 toward the insertion space 10. It is configured to be able to.
In addition, it is desirable that the outlet 11 is provided so as to almost uniformly discharge the seal gas in the circumferential direction of the upper cylinder 8. The outlets 11 may be arranged in one or more rows, or may be formed in a slit shape continuous in the circumferential direction.
[0017]
Further, the outlet 11 is provided at a position where the distance L from the opening 9 of the upper tube 8 is equal to or longer than the inner diameter D of the core tube 2. Preferably, the distance L is at least twice the inner diameter D. Further, it is preferable that the inner diameter of the upper tube 8 is equal to the inner diameter D of the furnace tube 2. In addition, as a material of the upper cylinder 8, carbon, metal, ceramics, or the like can be used.
As described above, in the glass body heating apparatus 1 according to the present embodiment, the outlet 11 for blowing the seal gas is provided at a sufficient distance from the opening 9, and thus faces downward from the opening 9. Even if outside air may enter, the seal gas can effectively prevent outside air from entering the heating space 5.
[0018]
Next, a method of heating a glass body using the above-described glass body heating device 1 will be described.
First, the vertical furnace core tube 2 is heated by the heater 3 with the lower lid 7 attached to the lower cylinder 6 and the upper lid 14 attached to the upper cylinder 8. Then, the temperature of the heating space 5 is raised to a temperature at which the glass body 30 is heated. At that time, the purge gas is flown from the outlet 11 into the insertion space 10, the heating space 5, and the lower space 13. The purge gas may be started to flow before heating the furnace tube or simultaneously with the heating.
[0019]
The heating of the furnace tube 2 and the blowing of the purge gas are continuously performed, and when the temperature of the heating space 5 reaches a desired value, the sealing gas is blown out from the blowing port 11, the upper lid 14 is removed, and the glass body 30 is removed. Is lowered from above the opening 9 toward the insertion space 10. Further, the upper lid 14 may be attached to the opening 9 until the space 10, 5, 13 is filled with the purge gas.
Note that an inert gas from which dust such as argon, nitrogen, and helium is removed is used as the seal gas and the purge gas. The same gas can be used as the purge gas and the seal gas. Further, the flow rate of the purge gas may be smaller than the flow rate of the seal gas.
[0020]
The temperature of the insertion space 10 is lower in the upper part than in the heating space 5. Due to this temperature difference, the seal gas blown out from the blowout port 11 becomes an ascending airflow that rises in the insertion space 10, and flows out from the opening 9 to the outside because only the opening 9 is open. Go. In this state, the glass body 30 is inserted into the insertion space 10 from the opening 9.
At that time, even if the glass body 30 and the rising airflow of the sealing gas interfere with each other and outside air enters through the opening 9, the outlet 11, which is a source of the rising airflow, passes from the opening 9 to the furnace tube 2. Since the distance L equal to or larger than the inner diameter D is at the lower position, it is possible to prevent outside air that has been caught and entered the insertion space 10 from reaching the heating space 5.
[0021]
Therefore, even if the glass body 30 is inserted into the heating space 5 with the opening 9 opened, it is possible to prevent oxygen and dust contained in the outside air from entering at least into the heating space 5 and the lower space 13. be able to.
Further, since the blowout port 11 can blow out the purge gas and the seal gas almost uniformly in the circumferential direction of the upper cylinder 8, the upward airflow is less likely to be biased and the outside air is hardly entrained.
In addition, by appropriately adjusting the amount of purge gas to be blown out and keeping each of the spaces 10, 5, 13 at a positive pressure, the invasion of outside air can be more effectively prevented.
[0022]
As described above, the glass body 30 is heated while the heating space 5 is maintained in the atmosphere of the purge gas, and a high-quality glass article can be obtained.
In the present embodiment, the glass body 30 is a glass base material for an optical fiber, and can be subjected to stretching, drawing, and the like by heating.
[0023]
(2nd Embodiment)
Next, a second embodiment of the method and apparatus for heating a glass body according to the present invention will be described.
In the second embodiment, in addition to the features of the above-described first embodiment, the length of the insertion portion in the vertical direction can be expanded and contracted, and when the glass body is inserted into the vertical furnace tube from above, the opening portion is formed. It is characterized in that the distance from the seal gas to the position where the seal gas is blown out is set to be equal to or larger than the inner diameter of the core tube.
[0024]
FIG. 2 shows a schematic diagram of a heating device for a glass body used in the present embodiment. The same parts as those in the above-described first embodiment are denoted by the same reference numerals, and redundant description will be omitted.
As shown in FIG. 2, the heating device 20 for a glass body is different from the first embodiment in the configuration of the insertion portion (upper tube 8) in the above-described first embodiment, and the other portions are the same in configuration as the first embodiment. .
[0025]
The insertion portion 21 in the present embodiment includes an upper cylinder 8a and a bellows-shaped cylinder 22 connected to an upper end of the upper cylinder 8a. The above-described outlet 11 is provided in the upper cylinder 8a, and a gas introduction part 12 formed so as to communicate with the outlet 11 is provided therearound.
[0026]
The bellows-shaped cylinder 22 has an upper end suspended from a wire (not shown) or the like, and the length of the bellows-shaped cylinder 22 in the vertical direction can be expanded or contracted by winding the wire. That is, by expanding and contracting the bellows-shaped cylinder 22, the distance L from the opening 9 at the upper end to the outlet 11 can be changed.
The material of the bellows-shaped cylinder 22 is preferably selected in consideration of flexibility, airtightness, and heat resistance. For example, a composite material in which carbon fibers coated with aluminum and a silicone resin are bonded together can be used.
[0027]
A method of heating the glass body 30 using the above-described glass body heating device 20 will be described.
First, before inserting the glass body 30 into the heating space 5 of the furnace tube 2, the length of the bellows-shaped cylinder 22 is adjusted so that the distance L from the opening 9 to the outlet 11 is changed to the inner diameter D of the furnace tube 2. Set so as to be as described above.
Thereafter, in the same manner as in the first embodiment described above, heating of the furnace tube 2 and blowing of the sealing gas are performed, and the glass body 30 is inserted into the heating space 5. Then, while maintaining the heating space 5 in the atmosphere of the purge gas, the glass body 30 is heated to obtain a desired glass article.
[0028]
As shown in FIG. 3, when heating the glass body 30, the dummy bar 32 connected to the upper end of the glass body 30 is gripped by the upper chuck 33 and the upper chuck 33 is gradually lowered. . Thereby, the glass body 30 is gradually heated from the lower end side to the upper end side.
For example, as shown in FIG. 3, when the glass body 30 is drawn by heating, the descent speed of the upper chuck 33 and the drawing tension of the optical fiber 31 drawn from the glass body 30 are appropriately controlled. The optical fiber 31 having a desired diameter is manufactured. In order to ensure airtightness in the opening 9, the opening 9 is provided with an upper lid 23 having a hole formed such that the clearance with the dummy bar 32 is minute.
[0029]
As the drawing progresses, the upper chuck 33 gradually descends. By reducing the length of the bellows-shaped cylinder 22 in accordance with the lowering of the upper chuck 33, the relative position between the dummy rod 32 and the upper lid 23 is reduced. The target position is kept constant and airtightness can be easily maintained. Further, the distance between the upper chuck 33 and the upper end of the glass body 30 required at the end of drawing can be shortened as compared with the first embodiment, so that a short dummy rod 32 can be used.
The same effect can be obtained when the glass body 30 is stretched.
[0030]
Further, in the present embodiment, a bellows-shaped insertion portion is used as a configuration that allows the length of the insertion portion to be extendable, but the length of the insertion portion may be extended or reduced by another configuration. For example, by combining a plurality of cylinders having different diameters, the sliding pipes may be sealed with a magnetic fluid using a so-called slide pipe type insertion portion.
[0031]
Further, as the glass body used in the present invention, a glass base material for an optical fiber, which requires high quality, can be suitably used.
[0032]
By the way, as another method different from the present invention, a method of preventing the invasion of outside air by blowing a sealing gas toward the glass body at the opening into which the glass body is inserted may be considered.
[0033]
However, since the inside of the furnace tube is heated to a higher temperature than the outside air, if the upper portion of the furnace tube is open, an upward airflow from below the opening to the upper side is generated. As a result, the upward flow of the sealing gas facilitates the upward flow of the sealing gas, and convection occurs near the opening due to interference with the glass body. There may not be. In that case, when the inserted glass body is heated to obtain a desired glass article, the quality of the glass article may be deteriorated.
In addition, it is possible to insert the glass body by lowering the temperature in the furnace tube, but it takes time to lower the temperature at that time and raise the temperature at the time of heating, which is not efficient.
[0034]
(Example)
Next, examples of the method and apparatus for heating a glass body according to the present invention will be described.
Using the glass body heating device 20 (see FIG. 2) described in the second embodiment, the ratio L / D of the distance L between the opening 9 and the outlet 11 to the inner diameter D of the furnace tube 2 is 4 It was made to become. Then, the oxygen concentration (%) at the center of the space at the position of L / D = 0.5 to 3.0 was measured.
Note that nitrogen (N ₂ ) was used as the seal gas, and the blowing amount was 50 liter / min.
The measurement results are shown in the following Table 1 and FIG.
[0035]
[Table 1]

[0036]
As can be seen from Table 1 and FIG. 4, the relationship between the oxygen concentration and L / D sharply changed when the distance L was equal to the inner diameter D (L / D = 1.0). When L / D <1.0, the oxygen concentration sharply decreases as the value of L / D increases, and when L / D ≧ 1.0, the oxygen concentration does not decrease so much even if L / D increases, When L / D ≧ 2, the oxygen concentration was almost constant.
That is, it turned out that the point of L / D = 1.0 has a critical significance in the relationship between L / D and oxygen concentration.
[0037]
【The invention's effect】
As described above, according to the glass body heating method and the heating apparatus of the present invention, when the glass body is inserted into the vertical furnace tube, the invasion of outside air is reliably prevented, so that high-quality glass can be obtained. Articles can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a heating device for carrying out a method for heating a glass body according to the present invention.
FIG. 2 is a schematic diagram showing a second embodiment of the heating device shown in FIG.
FIG. 3 is a schematic view showing a state of drawing using the heating device shown in FIG. 2;
FIG. 4 is a graph showing measurement results of an example according to the present invention.
FIG. 5 is a schematic diagram showing a state of drawing using a conventional heating device.
FIG. 6 is a schematic diagram showing a state of stretching using a conventional heating device.
[Explanation of symbols]
1 Heating device for glass body (first embodiment)
2 Furnace tube 3 Heater 4 Insulation material 5 Heating space 6 Lower cylinder 7 Lower lid 8 Upper cylinder (insertion part)
Reference Signs List 9 opening 10 insertion space 11 outlet 12 gas inlet 13 lower space 14 upper lid 20 glass body heating device (second embodiment)
21 Insertion part 22 Bellows-like cylinder 30 Glass body D Inner diameter L of furnace tube Distance between opening and outlet

Claims (4)

When inserting a glass body toward the inside of the core tube from above the insertion portion located above the vertical core tube,
From the opening located at the upper end of the insertion portion, a seal gas is blown out toward the inside of the insertion portion from a position below and at a distance equal to or more than the inner diameter of the furnace tube to remove the glass body inside the furnace tube. Insert
A method for heating a glass body, comprising heating the glass body in the furnace tube. The method for heating a glass body according to claim 1, wherein the length of the insertion portion in the vertical direction is expandable and contractable, and when the glass body is inserted from above the insertion portion,
A method for heating a glass body, wherein a distance from the opening to a position from which the seal gas is blown out is equal to or larger than an inner diameter of the furnace tube. A vertical furnace tube, and an insertion portion located above the furnace tube,
An outlet capable of blowing out a seal gas toward the inside of the insertion portion is provided at a position below the opening located at the upper end of the insertion portion at a distance equal to or more than the inner diameter of the furnace tube. A heating device for a glass body, characterized in that: The heating device for a glass body according to claim 3, wherein the insertion portion is configured to be able to expand and contract a length in a vertical direction.

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