JP2010037122A - Manufacturing apparatus of porous glass preform and manufacturing method of porous glass preform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep the inside of a quartz furnace core pipe clean, to prevent abnormality of treated glass surface and to prevent deposition substances from floating. <P>SOLUTION: Disclosed is a manufacturing method of porous glass preform, in which porous glass preform 3 is heated by supplying treating gas to a furnace core pipe 1 to which the porous glass preform 3 is inserted, wherein the heated porous glass preform 3 is taken out from the furnace core pipe 1 and, thereafter, purge gas is jetted to low temperature regions LT1, LT2 adjoining a heating part HT of the furnace core pipe 1 and, at the same time, is exhausted to the outside. Gas blowing nozzles gn1, gn2 of jetting the purge gas and exhaust pipes ep1, ep2 are disposed in the low temperature regions LT1, LT2. The gas blowing nozzles gn1, gn2 are arranged on the lower side of the low temperature regions LT1, LT2 of the reactor core pipe 1 of which the axial line 15 is arranged in the vertical direction, and the exhaust pipes ep1, ep2 are desirably arranged on the upper side of the low temperature regions LT1, LT2. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a porous glass base material manufacturing apparatus and a porous glass base material manufacturing method for supplying a processing gas to a furnace core tube having a porous glass base material inserted therein to heat the porous glass base material.

Conventionally, for example, when manufacturing a porous glass preform for optical fibers, fluorine is added as a cladding material, and therefore, after applying SiO ₂ soot, it is heated to a high temperature of about 1200 to 1650 ° C. in a fluorine atmosphere. A method has been proposed in which the sintering of glass proceeds with the addition (see Patent Document 1).

In this method, SiF ₄ is used as a processing gas, and the obtained SiO ₂ soot is heated to 1200 to 1600 ° C. in an atmosphere containing SiF ₄ to perform F addition and transparent vitrification treatment, and F is added to the outer periphery of the core. forming a cladding made of SiO ₂ glass containing. As described above, the fluorine-added sintering treatment method in which F is added and sintered after sooting is referred to as “F-added sintering method” in the present specification.

FIG. 5 is a schematic configuration diagram of a conventional manufacturing apparatus used in the F-added sintering method.
The manufacturing apparatus 500 includes a vertical core tube 501 having an axial line arranged in the vertical direction, a heater 505 for heating a porous glass preform (optical fiber preform) 503 from the outer periphery of the core tube 501, and the heater 505 and the core tube. A furnace casing (not shown) covering the periphery of 501. An exhaust gas treatment device (not shown) is connected to the core tube 501 via an exhaust pipe 507. An upper lid 509 is provided on the upper portion of the core tube 501, and the upper lid 509 is inserted through a support rod 511 that holds the porous glass base material 503 so as to be movable up and down.

As shown by an arrow G in the figure, the manufacturing apparatus 500 supplies a processing gas such as SiF ₄ at a predetermined pressure from a processing gas supply port 513 below the core tube 501 into the core tube 501, and deposits the deposits with a fluorine compound. Heat-sinter in a gas atmosphere.

  By the way, in the F-added sintering method as described above, suspended substances in the exhaust gas may be accumulated, and the problem is that the exhaust pipe is clogged by the accumulation of the suspended substances. For this reason, a floating substance recovery pipe having a gas reservoir that collides and stays exhaust gas is provided in the middle of the exhaust pipe, and the floating substance generated in the reactor core pipe is attached and recovered by this floating substance recovery pipe. A technique is known (see Patent Document 2).

JP 10-59737 A JP 2003-246628 A

As described above, in the production of an optical fiber preform to which F is added, glass particles are deposited on the outer periphery of the silica glass for the core, and then this deposited body is heated and sintered in a fluorine compound gas atmosphere to contain fluorine. A cladding layer made of silica glass is formed.
However, in the conventional F-added sintering method, since the fluorine compound gas is added, the optical fiber preform 503 and the quartz core tube 501 are etched, and its components (mainly SiO ₂ ) are in the low temperature region LT1 of the core tube 501. , LT2 and deposited on the inner wall of the core tube and deposited. When the deposit grows in the form of a film (therefore, a film that is deposited in one production does not cause a problem), it peels off from the inner wall, falls off, floats, and adheres to the surface of the optical fiber preform 503. Therefore, the attached trace may remain on the surface, and the quality of the optical fiber preform 503 is deteriorated.
In addition, a film floating during the process enters the exhaust pipe 507 and narrows the exhaust passage, which may cause an unstable exhaust factor. Further, when the optical fiber preform 503 is taken out from the core tube 501, the upper cover 509 at the top of the core tube is released. At that time, outside air is mixed into the core tube, turbulent flow is generated, and the attached film is peeled off. Soar. The suspended matter also adhered to the surface of the optical fiber preform.

  The film can be removed by heating the part attached to the inner wall of the core tube 501 to a high temperature, but when the quartz glass tube is heated to a high temperature (1000 ° C. or higher), the quartz glass tube is cristobalite (devitrification phenomenon). It will turn. If the temperature is returned to the original low steady state maintenance temperature (300 ° C.) or lower in this state, cracks may occur, which may cause a serious problem that the expensive core tube 501 is broken.

In addition, in order to improve the operating rate of the apparatus described in Patent Document 2, the technology for preventing clogging of the exhaust pipe can prevent clogging of the exhaust pipe, but the film on the inner wall surface of the reactor core pipe is prevented. Adhesion could not be prevented and the core tube could not be kept clean.
The present invention has been made in view of the above circumstances, and it is possible to keep the inside of a quartz furnace core tube clean, to prevent abnormalities on the surface of the treated glass, and to prevent the floating of the precipitated substances. An object of the present invention is to provide a material manufacturing apparatus.

The above object of the present invention is achieved by the following configuration.
(1) A porous glass preform manufacturing apparatus that supplies a processing gas to a core tube into which a porous glass preform is inserted and heat-treats the porous glass preform, and is adjacent to a heating section of the core tube An apparatus for producing a porous glass base material, characterized in that a gas blowing nozzle for ejecting a purge gas along the inner wall of the core tube and an exhaust pipe are provided in a low temperature region.

  According to this porous glass base material manufacturing apparatus, the purge gas blown from the gas blowing nozzle to the low temperature region is discharged from the exhaust pipe provided in the low temperature region, and the gas blowing nozzle is discharged from the gas blowing nozzle to the exhaust pipe. A high-speed airflow that flows toward is formed. This flow should just flow along the wall surface. In this high-speed air stream, the optical fiber preform generated in the low temperature region and the deposited substance due to the etching of the quartz core tube are transported and discharged out of the core tube from the exhaust pipe. The high-speed air flow also peels off the silica film deposited on the inner wall of the furnace core tube, and similarly discharges the peeled silica film from the exhaust pipe to the outside of the furnace core tube.

(2) The porous structure according to (1), wherein the gas blowing nozzle is disposed below a low temperature region of the vertical core tube, and the exhaust pipe is disposed above the low temperature region. Glass base material manufacturing equipment.

According to this porous glass base material manufacturing apparatus, the etching component adheres to the low temperature region in the core tube, and by blowing gas from the lower side of the region, the silica film adhering and peeling is peeled off. Can do. Since the peeled silica film has an exhaust pipe at the top, it is discharged from there. The fine silica film that cannot be exhausted is exhausted from the processing gas exhaust pipe. However, since it is in a very small amount, the exhaust pipe does not become so large that it is clogged with the silica film. Since the core tube has a low temperature region above and below the high temperature part, it is preferable to dispose a nozzle and an exhaust pipe on each of the upper part and the lower part on both ends of the heating part.
The inside of the furnace is hot and an updraft is generated near the wall of the core tube. For this reason, the silica film can be smoothly discharged by blowing the gas from the bottom to the top.

(3) According to (1) or (2), the gas spray nozzle and the exhaust pipe are arranged on an extension of a spiral passing through the vicinity of the inner diameter of the core tube centering on the axis of the core tube. Porous glass base material manufacturing equipment.

  According to this porous glass preform manufacturing apparatus, the spray nozzle and the exhaust pipe are arranged on the extension of the spiral that passes through the vicinity of the inner diameter of the core tube, so that the purge gas blown from the lower side can be removed from the inner wall of the core tube. , As well as swirling along, and discharged from an exhaust pipe provided on the upper side of the low temperature region. That is, a swirling flow rising from the gas spray nozzle toward the exhaust pipe is formed. In this swirl flow, the optical fiber preform generated in the low temperature region and the deposited substance due to the etching of the quartz core tube are transported and discharged out of the core tube from the exhaust pipe. Further, the swirling flow also peels off the silica film deposited on the inner wall of the core tube, and similarly discharges the peeled silica film out of the core tube from the exhaust pipe. Compared with a high-speed air flow whose flow direction is unspecified, the swirl flow flows evenly along the inner wall of the core tube, enhancing the peeling effect and the conveying action.

(4) The porous glass preform manufacturing apparatus according to any one of (1) to (3), wherein a plurality of the gas spray nozzles and the exhaust pipes are arranged.

  According to this porous glass preform manufacturing apparatus, high-speed airflow and swirl flow are densely formed along the inner wall of the core tube, and the effect of separating the silica film and its transporting action are increased.

(5) The apparatus for producing a porous glass base material according to any one of (1) to (4), wherein the gas spray nozzle is inclined upward.

  According to this porous glass preform manufacturing apparatus, a swirl flow that rises toward the exhaust pipe along the inner wall of the core tube from the gas spray nozzle is easily formed.

(6) The apparatus for producing a porous glass base material according to any one of (1) to (5), wherein purge gas heating means for heating purge gas ejected from the gas spray nozzle is provided.

  According to this porous glass base material manufacturing apparatus, the purge gas that has been preheated (200 to 800 ° C.) is ejected, so that the purge gas at room temperature is blown to the cristobalite portion of the core tube, Generation of cracks due to cooling of the core tube is prevented.

(7) A method for producing a porous glass base material, wherein the porous glass base material is heat-treated using the porous glass base material producing apparatus described in (1) to (6) above, wherein the heat treatment The porous glass base material is taken out from the core tube, and then discharged to the outside while ejecting a purge gas along the inner wall of the core tube with respect to a low temperature region adjacent to the heating portion of the core tube Manufacturing method of glass base material.

  According to this method for producing a porous glass base material, a high-speed updraft is generated in a low-temperature region where a silica film is generated, and the deposited substance adhering to the inner wall of the core tube is conveyed by the high-speed airflow, And can be discharged out of the core tube efficiently. In addition, since the silica film peeling in the furnace core tube occurs when the film grows to some extent and the film thickness increases, it is sufficient to spray and exhaust to the extent that the peeling is regularly promoted.・ There is no need to exhaust.

  According to the method for producing a porous glass base material according to the present invention, after the heat-treated porous glass base material is taken out from the core tube, a purge gas is ejected to a low temperature region adjacent to the heating portion of the core tube. Since the exhaust gas is exhausted to the outside, a high-speed updraft is generated in the low-temperature region where the silica film is generated, and the deposited material adhering to the inner wall of the core tube is transported by the high-speed airflow, quickly and efficiently outside the core tube. Can be discharged. As a result, the inside of the quartz furnace core tube can be kept clean, abnormalities on the treated glass surface can be prevented, and precipitation substances can be prevented from floating.

  According to the porous glass base material manufacturing apparatus of the present invention, the gas spray nozzle for ejecting the purge gas and the exhaust pipe are provided in the low temperature region adjacent to the heating portion of the core tube. The purge gas blown out is discharged from an exhaust pipe provided in the same low temperature region, and a high-speed airflow flowing from the gas spray nozzle toward the exhaust pipe is formed in the low temperature region. In this high-speed air stream, the optical fiber preform generated in the low temperature region and the deposited substance due to the etching of the quartz core tube are transported and discharged out of the core tube from the exhaust pipe. The high-speed air flow also peels off the silica film deposited on the inner wall of the furnace core tube, and similarly discharges the peeled silica film from the exhaust pipe to the outside of the furnace core tube. As a result, the inside of the quartz furnace core tube can be kept clean, abnormalities on the treated glass surface can be prevented, and precipitation substances can be prevented from floating.

Hereinafter, preferred embodiments of a method for producing a porous glass preform and an apparatus for producing a porous glass preform according to the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an outline of a manufacturing apparatus according to the present invention.
The manufacturing apparatus 100 according to the present embodiment includes a core tube 1 whose axis is arranged in the vertical direction, a heater 5 that heats a porous glass preform (optical fiber preform) 3 from the outer periphery of the core tube 1, a heater 5, A furnace casing (not shown) covering the periphery of the furnace core tube 1, gas spray nozzles gn1, gn2, and exhaust pipes ep1, ep2 are provided. An exhaust gas treatment device (not shown) is connected to the core tube 1 through a treatment gas exhaust pipe 7. An upper lid 9 is provided on the upper portion of the core tube 1, and the upper lid 9 is inserted through a support rod 11 that rotatably supports the optical fiber preform 3 so as to be movable up and down.

As shown by an arrow G in the figure, the manufacturing apparatus 100 supplies a processing gas such as SiF ₄ at a predetermined pressure into the core tube 1 from a processing gas supply tube 13 provided with a processing gas supply port at the bottom of the core tube 1. Then, the deposited body is heated and sintered (F-added sintering) in a fluorine compound gas atmosphere. The core tube 1 is made of quartz, and the temperature of the core tube 1 is raised around a portion (heating part) HT located inside the heater 5 in the core tube 1 by heat generation of the heater 5. The optical fiber preform 3 is integrally formed with the support bar 11 so as to be suspended by the support bar 11, and can be moved up and down by an elevating device (not shown) to which the support bar 11 is attached. . The lifting device can also rotate the optical fiber preform 3 together with the support rod 11 about its axis. The upper lid 9 opens and closes the opening at the upper end of the core tube when the optical fiber preform 3 is introduced or removed.

A gas supply control device (not shown) for supplying a processing gas is connected to the processing gas supply pipe 13. The gas supply control device supplies a processing gas into the core tube 1 from a processing gas supply tube 13 provided at the lower part of the core tube 1. As the processing gas, SiF ₄ is used for the above reason.

  Further, a reactor core pressure monitor (not shown) is provided near the upper end of the reactor core tube 1 so that the pressure in the reactor space can be monitored in a timely manner. Data measured by the reactor core pressure monitor is sent to the gas supply control device and used to adjust the supply amount of the processing gas to the processing gas supply pipe 13. By maintaining the pressure in the furnace space at atmospheric pressure or higher, it is possible to prevent outside air from entering the furnace space, and it is possible to maintain the quality of the glass base material to be manufactured well.

Gas blowing nozzles gn1, gn2 for ejecting purge gas and exhaust pipes ep1, ep2 are provided in the low temperature regions LT1, LT2 in the vertical direction of the core tube 1 adjacent to the heating section HT of the core tube 1. As the purge gas, an inert gas such as N ₂ is used. In the present embodiment, the gas blowing nozzles gn1 and gn2 are arranged below the low temperature regions LT1 and LT2 of the core tube 1 with the axis 15 arranged in the vertical direction, and the exhaust pipes ep1 and ep2 are arranged in the low temperature regions LT1 and LT2. It is arranged on the upper side.

  Etching components adhere to the low temperature regions LT1 and LT2 in the furnace core tube 1, and when the purge gas is blown from the lower side of the regions, the adhering and peeling silica film is peeled off. The peeled silica film is exhausted from the exhaust pipes ep1 and ep2 at the top. Even if there is a fine silica film that cannot be discharged, it can be discharged from the processing gas exhaust pipe 7. Since the core tube 1 has two low temperature regions LT1 and LT2 above and below the high temperature part, gas blowing nozzles gn1 and gn2 and exhaust pipes ep1 and ep2 are provided respectively at the upper and lower parts on both ends of the heating part HT. It is good to arrange two sets.

FIG. 2 is a schematic view of the positional relationship between the gas blowing nozzle and the exhaust pipe, in which the cross-sectional view including the axis of the low temperature region is represented by (a) and the plan view is represented by (b).
As shown in FIG. 2, the gas blowing nozzles gn1, gn2 and the exhaust pipes ep1, ep2 are preferably arranged on an extension of the spiral 17 with the axis 15 of the core tube 1 as the center. Note that the spiral 17 is a line that turns about the axis 15 and, strictly speaking, an ideal spiral space curve that is formed when traveling at a constant speed in the axial direction while rotating on the cylindrical surface. There may be some variation in the turning radius R and the interval P between the turning curves of each stage. Further, in the illustrated example, the lower low temperature region LT1 is shown, but the configuration in the upper low temperature region LT2 is also the same.

  Thus, by arranging the gas blowing nozzles gn1, gn2 and the exhaust pipes ep1, ep2 almost on the extension of the spiral, the purge gas PG blown from the lower side rises while turning along the inner wall 1a of the core tube 1. And it is discharged | emitted from exhaust pipe ep1, ep2 provided in the upper side of the same low temperature range. That is, a swirl flow from the gas blowing nozzles gn1, gn2 toward the exhaust pipes ep1, ep2 is formed. In this swirl flow, the precipitates produced by etching the optical fiber preform 3 and the quartz core tube 1 generated in the low temperature regions LT1 and LT2 are transported and discharged out of the core tube through the exhaust pipes ep1 and ep2. The swirling flow also peels off the silica film deposited on the inner wall 1a of the core tube, and similarly discharges the peeled silica film from the exhaust pipes ep1 and ep2 to the outside of the core tube. Compared with a high-speed air flow whose flow direction is unspecified, the swirling flow flows evenly along the core tube inner wall 1a, and the peeling effect and the conveying action can be enhanced.

FIG. 3 is a plan view of a low temperature region in which a plurality of gas spray nozzles are provided.
A plurality of gas blowing nozzles gn1, gn2 and exhaust pipes ep1, ep2 may be arranged. For example, as shown in FIG. 3, the gas spray nozzle gn1 provided in the lower low temperature region LT1 has four gas spray nozzles gn1A, gn1B, gn1C, and gn1D in the tangential direction of the core tube 1 at equal intervals in the circumferential direction (90 Degree intervals). The gas spray nozzle gn2 and the exhaust pipes ep1 and ep2 can be similarly configured. Thereby, a high-speed air flow and a swirl flow are densely formed along the core tube inner wall 1a, and the peeling effect of the silica film and its conveying action can be increased.

  Moreover, it is preferable that the gas spray nozzles gn1 and gn2 are inclined upward. The swirl flow that rises toward the exhaust pipes ep1 and ep2 from the gas spray nozzles gn1 and gn2 along the inner wall 1a of the core by inclining the gas spray nozzles gn1 and gn2 upward and ejecting the purge gas PG obliquely upward. Is more easily formed.

  Furthermore, the manufacturing apparatus 100 may be equipped with a purge gas heating means (not shown) for heating the purge gas ejected from the gas spray nozzles gn1 and gn2. The purge gas heating means may be attached to each of the gas spray nozzles gn1 and gn2, or may be attached to the main portion to be supplied to the individual gas spray nozzle before that. As a result, the purge gas that has been preheated (200 to 800 ° C.) is ejected, so that the purge gas at normal temperature is blown onto the cristobalite portion of the core tube 1 and the core tube 1 in the high temperature region is cooled. Occurrence is prevented.

FIG. 4 is a configuration diagram of a modified example that also serves as a processing gas supply pipe and a processing gas exhaust pipe.
As shown in FIG. 4, the manufacturing apparatus 100 </ b> A may have a configuration in which the gas spray nozzle gn <b> 1 and the exhaust pipe ep <b> 2 provided in the low temperature regions LT <b> 1 and LT <b> 2 are omitted. In the configuration according to this modification, the processing gas supply pipe 13 may be connected at the position of the gas blowing nozzle gn1 shown in FIG. 1 in addition to being connected from below in the direction of the axis 15 as shown in the figure. With such a configuration, the purge gas PG can be caused to flow spirally, and the gas spray nozzle gn1 and the exhaust pipe ep2 can be omitted to reduce the apparatus cost. The processing gas or the purge gas PG is selectively supplied to the processing gas supply pipe 13 by a switching valve (not shown). Further, the purge gas PG is exhausted from the processing gas exhaust pipe 7 in the low temperature region LT2. The processing gas or the purge gas PG may be selectively exhausted from the processing gas exhaust pipe 7 by a switching valve.

Next, the manufacturing method of the porous glass base material using the manufacturing apparatus 100 which has the said structure is demonstrated.
In the method of manufacturing the optical fiber preform 3 using the manufacturing apparatus 100, after the F-added and sintered optical fiber preform 3 is taken out from the core tube 1, the low temperature region LT1, adjacent to the heating section HT of the core tube 1, is obtained. The purge gas PG is ejected from the gas spray nozzles gn1 and gn2 to the LT2.

  The purge gas PG blown from the gas blowing nozzles gn1 and gn2 to the low temperature regions LT1 and LT2 is discharged from exhaust pipes ep1 and ep2 provided in the same low temperature region LT1 and LT2. As a result, high-speed airflows flowing from the gas blowing nozzles gn1 and gn2 toward the exhaust pipes ep1 and ep2 are formed in the low temperature regions LT1 and LT2. Although this flow should just be ejected along a wall surface, Preferably it is the said swirl | flow.

  In this high-speed air stream, the precipitates produced by etching the optical fiber preform 3 and the quartz core tube 1 generated in the low temperature regions LT1 and LT2 are transported and discharged out of the core tube through the exhaust pipes ep1 and ep2. The high-speed air flow also peels off the silica film deposited on the inner wall 1a of the core tube, and similarly discharges the peeled silica film out of the core tube through the exhaust pipes ep1 and ep2.

  As described above, a high-speed air flow is generated for the low temperature regions LT1 and LT2 in which the silica film is generated, and the deposited material adhering to the inner wall 1a of the furnace core tube is conveyed by the high-speed air flow, and the core tube is quickly and efficiently produced. It becomes possible to discharge outside. Note that the silica film peeling in the furnace core tube occurs when the film thickness grows to a certain extent and the film thickness increases. Therefore, spraying and exhausting may be performed to the extent that the peeling is regularly promoted. There is no need to blow or exhaust.

  Therefore, according to the method for manufacturing the porous glass preform described above, after the F-added and sintered optical fiber preform 3 is taken out from the core tube 1, the low temperature regions LT1 and LT2 adjacent to the heating portion HT of the core tube 1 are used. In contrast, since the purge gas PG is exhausted to the outside while flowing, a high-speed air flow is generated in the low temperature regions LT1 and LT2 where the silica film is generated, and the deposited substances adhering to the core tube inner wall 1a are generated by the high-speed air flow. It can be transported and discharged out of the core tube quickly and efficiently. As a result, it is possible to keep the inside of the quartz furnace core tube clean, to prevent the deposited material from adhering to the surface of the optical fiber preform, and to prevent the deposited material from floating.

  As described above, according to the porous glass preform manufacturing apparatus 100, the gas spray nozzles gn1 and gn2 for ejecting the purge gas PG to the low temperature regions LT1 and LT2 adjacent to the heating part HT of the core tube 1 and the exhaust pipe Since ep1 and ep2 are provided, the purge gas PG blown from the gas blowing nozzles gn1 and gn2 to the low temperature range LT1 and LT2 is discharged from the exhaust pipes ep1 and ep2 provided in the same low temperature range LT1 and LT2, and the low temperature range LT1 , LT2 is formed with a high-speed airflow flowing from the gas blowing nozzles gn1, gn2 toward the exhaust pipes ep1, ep2. In this high-speed air stream, the precipitates produced by etching the optical fiber preform 3 and the quartz core tube 1 generated in the low temperature regions LT1 and LT2 are transported and discharged out of the core tube through the exhaust pipes ep1 and ep2. The high-speed air flow also peels off the silica film deposited on the inner wall 1a of the core tube, and similarly discharges the peeled silica film out of the core tube through the exhaust pipes ep1 and ep2. As a result, the inside of the quartz furnace core tube can be kept clean, abnormalities on the treated glass surface can be prevented, and precipitation substances can be prevented from floating.

  Further, during the process, processing gas is introduced from the lower side of the core tube 1 and exhausted from the upper side. This is because the processing gas flows from the bottom to the top due to the upward air flow. However, when the silica film is peeled from the top to the bottom with such a core tube 1, the silica film is formed at the bottom of the core tube. It accumulates and soars during the process due to the updraft. In the above embodiment, a swirl flow that flows from the lower side to the upper side is formed and peeled from the lower side to the upper side, thereby avoiding a rise during the process.

  The above-described method for producing a porous glass preform is effective not only for a sintering furnace for optical fibers but also for a glass production method for heating in another fluorine compound gas atmosphere.

  In the above-described embodiment, the sintering furnace that performs F addition sintering has been described. However, the present invention is effective even when applied to a dehydration furnace.

  Moreover, in the said embodiment, since the swirl | vortex flow which raises is formed, it employ | adopts especially for the cylindrical core tube 1, and a remarkable effect is acquired.

  The purge gas PG can flow spirally by accurately positioning the gas blowing nozzles gn1, gn2 and the exhaust pipes ep1, ep2. However, a spiral groove is provided on the wall surface as an auxiliary. It is also possible.

It is a block diagram showing the outline of the manufacturing apparatus which concerns on this invention. It is the schematic diagram of the positional relationship of the gas spray nozzle and exhaust pipe which represented the cross-sectional view containing the axis line of a low temperature area (a), and the planar view was represented by (b). It is a top view of the low temperature range in which the some gas spray nozzle was provided. It is a block diagram of the modification which serves as a process gas supply pipe and a process gas exhaust pipe. It is a schematic block diagram of the conventional manufacturing apparatus used for F addition sintering method.

Explanation of symbols

1 Core tube 3 Optical fiber preform (porous glass base material)
15 Axis 17 Spiral 100 Manufacturing apparatus for porous glass base material ep1, ep2 Exhaust pipe gn1, gn2 Gas spray nozzle HT Heating part LT1, LT2 Low temperature region PG Purge gas

Claims (7)

An apparatus for producing a porous glass base material, wherein a processing gas is supplied to a furnace tube into which the porous glass base material is inserted to heat-treat the porous glass base material,
An apparatus for producing a porous glass base material, comprising a gas blowing nozzle for ejecting a purge gas along an inner wall of the core tube and an exhaust pipe in a low temperature region adjacent to the heating section of the core tube.   2. The porous glass mother according to claim 1, wherein the gas spray nozzle is disposed below a low temperature region of the vertical core tube, and the exhaust tube is disposed above the low temperature region. Material manufacturing equipment.   3. The porous structure according to claim 1, wherein the gas blowing nozzle and the exhaust pipe are arranged on an extension of a spiral passing through the vicinity of the inner diameter of the core tube with the axis of the core tube as a center. Quality glass base material manufacturing equipment.   The said glass spray nozzle and the said exhaust pipe are arranged with two or more, The manufacturing apparatus of the porous glass base material of any one of Claims 1-3 characterized by the above-mentioned.   The said glass spray nozzle was inclined toward the upper side, The manufacturing apparatus of the porous glass base material of any one of Claims 1-4 characterized by the above-mentioned.   The apparatus for producing a porous glass base material according to any one of claims 1 to 5, further comprising purge gas heating means for heating the purge gas ejected from the gas spray nozzle. A manufacturing method of a porous glass preform using the porous glass preform manufacturing apparatus according to any one of claims 1 to 6, wherein the porous glass preform is heated.
After the heat-treated porous glass base material is taken out from the core tube, it is exhausted to the low temperature region adjacent to the heating portion of the core tube while ejecting purge gas along the inner wall of the core tube. A method for producing a porous glass base material.

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