JP5821443B2 - Manufacturing method of glass base material and sintering furnace for manufacturing glass base material - Google Patents

Description

  The present invention relates to a method for producing a glass base material in which a glass particulate deposit is heated and sintered in a heating furnace, and a sintering furnace for producing a glass base material.

  Conventionally, for example, a sintering furnace for producing a glass base material as described in Patent Document 1 is known. As shown in FIG. 8, a sintering apparatus 100 as a sintering furnace includes a core tube 106 having a lid 109 and a heating furnace 105 having a heat source 104 disposed around the core tube 106. The sintering apparatus 100 inserts a porous glass preform 111, which is a glass particulate deposit body obtained by depositing glass particulates on a starting rod 112, which is a seed rod, into the core tube 106, and rotates the porous glass preform 111. Then, it is lowered and sintered by the heating furnace 105. The sintering apparatus 100 includes an inert gas introduction pipe 102 that supplies He gas or the like to the lower end of the furnace core tube 106, and an exhaust device 108 above the furnace core tube 106.

  In the sintering apparatus 100, the upper heat shield 107 is installed above the porous glass base material 111, and the lower heat shield 103 is installed below the sintering completion part 116 of the porous glass base material 111. ing. The upper heat shield 107 is placed on the cone body 113 above the porous glass base material 111, and the lower heat shield 103 is fixed to the furnace core tube 106. The upper heat shield 107 and the lower heat shield 103 are made of quartz glass, and are installed above and below the porous glass base material 111 to control the escape of radiant heat from the cone body 113 to control the temperature of the core tube 106. It suppresses unevenness and natural convection.

JP 2000-219519 A

  In the step of sintering the porous glass base material 111, the heat is not transferred well or dissipated, so that the upper part of the porous glass base material 111 becomes unsintered, or conversely, it is heated more than necessary. 112 may be stretched. If the upper end portion of the porous glass base material 111 is unsintered, cracks may occur due to the difference in shrinkage from the sintered portion, and the porous glass base material 111 may fall. In addition, the unsintered portion is sintered in the subsequent drawing step, and the porous glass preform 111 is bent in the drawing furnace. In addition, the soot powder in the unsintered part may fall and adhere to the sintered part, thereby breaking the wire during drawing. In addition, problems such as cracking and dropping due to the difference in coefficient of thermal expansion occur at the boundary between the unsintered part and the sintered part during flame polishing.

  If the upper portion of the porous glass base material 111 is heated more than necessary, the starting rod 112 is excessively heated and the starting rod 112 is stretched. When the starting bar 112 is stretched, problems such as bending and dropping of the porous glass base material 111 occur. Note that the porous glass base material 111 tends to increase in size, and the weight of the porous glass base material 111 is increased, so that the starting rod 112 is easily stretched.

  In the sintering apparatus 100 described in Patent Document 1, the escape of radiant heat from the cone body 113 is controlled by the upper heat shield 107, but before the porous glass base material 111 is inserted into the core tube 106. At least the upper heat shield 107 needs to penetrate from above the porous glass base material 111 and be placed on the cone body 113. During this mounting operation, the heat shield 107 and the soot body come into contact with each other, which may cause problems such as damage to the porous glass base material 111.

  In the sintering apparatus 100, the installation position of the heat shield 107 is fixed by the porous glass base material 111, and the position adjustment of the heat shields 103 and 107 with respect to the heat zone cannot be performed for each base material. It is difficult to completely solve the elongation of the starting bar 112 during sintering and the prevention of unsintering of the upper end portion of the porous glass base material 111.

  The object of the present invention is made in view of the above-described circumstances, and is a method for producing a glass base material that eliminates unsintered portions and prevents excessive heating of the seed rod and eliminates elongation. It is providing the sintering furnace which manufactures a glass base material.

  The method for producing a glass base material according to the present invention capable of solving the above-mentioned problem is to deposit glass fine particles on a starting seed rod, and to form glass fine particles comprising a seed rod portion, a tapered glass fine particle deposition portion, and a glass fine particle steady deposition portion A method for producing a glass base material in which a deposit is heated and sintered by heat from a heat zone, the longitudinal direction of the glass particulate deposit near the upper portion of the tapered glass particulate deposit on the glass particulate deposit By disposing a heat shielding jig whose position can be adjusted, the glass particulate deposit is sintered while heat transmitted from the heat zone and the glass base material to the seed rod portion is shielded. Yes.

  According to the manufacturing method of the glass base material configured as described above, the heat shielding jig whose position can be adjusted is disposed in the vicinity of the upper portion of the tapered glass fine particle depositing portion on the upper portion of the glass fine particle depositing body. Even if it is close to the zone, the heat transmitted to the seed rod side can be shielded. As a result, it is possible to reliably prevent the seed rod portion from being stretched and to reduce the area of the unsintered portion at the upper end portion of the glass fine particle deposit. Further, since the position of the heat shield jig can be adjusted in the longitudinal direction of the glass particulate deposit, the position of the heat shield jig can be adjusted for each glass particulate deposit without contacting the glass particulate deposit.

  The sintering furnace for producing the glass base material according to the present invention capable of solving the above-mentioned problems is to deposit glass fine particles on a starting seed rod, and from the seed rod portion, the tapered glass fine particle accumulation portion, and the glass fine particle steady accumulation portion. A furnace core tube containing the glass fine particle deposit, and a heating furnace for heating and sintering the glass fine particle deposit, and in the vicinity of the upper portion of the tapered glass fine particle deposit portion on the glass fine particle deposit, A heat shielding jig capable of adjusting the position in the longitudinal direction of the glass fine particle deposit is provided.

  According to the sintering furnace for producing the glass base material configured in this way, the heat shielding jig whose position can be adjusted is disposed in the vicinity of the upper portion of the tapered glass fine particle depositing portion on the upper portion of the glass fine particle depositing body. Even if the part is brought close to the heat zone, the heat transmitted to the seed bar part side can be shielded. Thereby, the elongation of the seed rod part can be reliably prevented. Moreover, the area | region of the unsintered part of the upper end part of a glass particulate deposit can be made small. Further, since the position of the heat shield jig can be adjusted in the longitudinal direction of the glass particulate deposit, the position of the heat shield jig can be adjusted for each glass particulate deposit without contacting the glass particulate deposit.

  In the sintering furnace for manufacturing the glass base material, it is preferable that the heat shield jig is fixed to the furnace core tube or the seed rod part.

  According to the sintering furnace for producing the glass base material having the above-described configuration, the heat shield jig is, for example, a support rod, a fitting portion, or a seed rod for fitting an upper lid or a seed rod portion that is a part of the core tube. Since it is fixed to the part itself and does not come into contact with the glass fine particle deposit, the glass fine particle deposit can be reliably prevented from being damaged.

  According to the method for producing a glass base material and the sintering furnace for producing the glass base material according to the present invention, the position-adjustable heat shield jig is disposed in the vicinity of the upper tapered portion of the glass fine particle deposit. The tool can be adjusted to an optimum position between the tapered glass fine particle deposition portion and the seed rod portion. Therefore, the heat transmitted to the seed rod part side can be reliably shielded by the heat shield jig even if the seed rod part is close to the heat zone, and it is possible to reliably prevent the seed rod part from being stretched. The area | region of the unsintered part of the upper end part of a deposit can be made small.

  In addition, since the position of the heat shield jig can be adjusted in the longitudinal direction of the glass particulate deposit body, the position of the heat shield jig can be adjusted for each glass particulate deposit body without contacting the glass particulate deposit body. It is possible to prevent problems such as damaging the glass particulate deposit.

It is the schematic which shows 1st Embodiment of the sintering furnace which manufactures the glass base material which concerns on this invention. It is a principal part enlarged view of the heat shield jig periphery of FIG. The state before fitting of the lower jig | tool of FIG. 2 is shown, (a) is a top view, (b) is a side view. The state after the lower jig | tool of FIG. 2 is fitted is shown, (a) is a top view, (b) is a side view. 2 shows a modification of the lower jig in FIG. 2, (a) is a plan view before fitting, and (b) is a plan view after fitting. FIG. 2 is an upper jig in FIG. 2, (a) is a plan view, and (b) is a side view. FIG. It is a principal part enlarged view of the heat shield jig periphery which shows 2nd Embodiment of the sintering furnace which manufactures the glass base material which concerns on this invention. It is the schematic which shows the sintering furnace of the conventional glass base material.

  Hereinafter, embodiments of a method for producing a glass base material and a sintering furnace for producing the glass base material according to the present invention will be described in detail with reference to FIGS.

(First embodiment)
As shown in FIG. 1, the sintering furnace 10 for producing the glass base material according to the first embodiment of the present invention has a glass fine particle in which the upper part is closed by a lid part 13 and glass fine particles are deposited on a starting seed bar 3. A core tube 11 that houses the deposit 1 and a heater 12 that is a heat source for heating and sintering the glass particulate deposit 1 on the outer peripheral side of the core 11 are provided.

  The glass fine particle deposit 1 includes a cylindrical glass fine particle deposition unit 4, tapered glass particle deposition units 2 and 5 at the upper and lower ends of the glass fine particle deposition unit 4, and an upper tapered glass particle deposition unit 2. A seed rod portion 8 in which glass fine particles are not deposited in the upper portion, and is suspended in the core tube 11 by a connecting member 14. A gas supply unit 15 that supplies an inert gas such as He gas and a gas discharge unit 16 are provided at the lower portion of the core tube 11 and the upper portion thereof.

  As shown in FIG. 2, the sintering furnace 10 is a heat shield made of carbon capable of adjusting the position of the glass fine particle deposit 1 in the longitudinal direction in the vicinity of the tapered glass fine particle deposit 2 at the top of the glass fine particle deposit 1. A jig 20 is provided. The heat shield jig 20 includes an upper jig 21 fixed to a predetermined position of the starting seed bar 3, a disk-shaped lower jig 22 having a heat shield function, three suspension bolts 23, and each suspension bolt. And adjustment nuts 26 </ b> A and 26 </ b> B screwed to 23. A seed bar stepped portion 7 for engaging the upper jig 21 is provided at an intermediate portion of the starting seed bar 3 for fixing the upper jig 21.

  The outer diameter D1 of the heat shield jig 20 is set to an outer diameter dimension that falls within a range of 0.3D0 <D1 <0.98D0, where D0 is the inner diameter of the core tube 11. For example, when the inner diameter D0 is 210 mm, the substantially outer diameter D1 is set within a range of 63 mm to 206 mm. The height H1 of the heat shield jig 20 is set to about 200 mm when the position H0 of the lower jig 22 is, for example, 300 mm from the upper end of the starting seed bar 3.

  As shown in FIGS. 3A and 3B, the lower jig 22 includes a first heat shield plate 24 having a notch 27 and a second heat shield plate 25 fitted to the first heat shield plate 24. And is composed of. The first heat shield plate 24 has a seed rod through-hole 28 through which the seed rod portion 8 penetrates at the center thereof, and a notch portion 27 for attachment to the seed rod portion 8 and the suspension bolt 23 are inserted through the first heat shield plate 24. There are two bolt through holes 29. The notch portion 27 is for disposing the seed rod portion 8 from the notch portion 27 in the seed rod through hole 28 by removing the second heat shield plate 25 when attached to the seed rod portion 8. A first step portion 24A for fitting is provided at both end edges.

  The second heat shield plate 25 has, for example, a fan shape so as to cover the notch portion 27 by being fitted from above the notch portion 27 of the first heat shield plate 24. The cutout shape of the cutout portion 27 is not limited to a fan shape, and the cutout portion 27 may be substantially rectangular as shown in FIG. The second heat shield 25 is formed wider than the notch 27 so as to be placed on both ends of the notch 27 on the first heat shield 24, and has second step portions 25A at both edges. The second heat shield plate 25 is fixed to the first heat shield plate 24 by fitting the second step portion 25 </ b> A to the first step portion 24 </ b> A of the first heat shield plate 24.

  In addition, when creating the recess 24B in a part of the first step 24A and fitting with the second step 25A, by creating the projection 25B at the position of the second step 25A corresponding to the recess 24B, The second heat shield plate 25 can be fixed so as not to slide down. The positions of the concavo-convex portions 24B and 25B may be created at the end of the notch 27 as shown in FIG. 3A, or near the center of the notch 27 as shown in FIG. There may be. Since it can be fixed in the front-rear direction as long as it is near the center, it can be fixed more firmly.

  When the notch 27 has a fan shape, the notch angle θ1 of the notch 27 of the first heat shield 24 is, for example, about 130 °, and the center angle θ2 of the second heat shield 25 is wider than the notch angle θ1 ( For example, θ2> θ1) is set in a range of 135 ° to 140 °.

  As shown in FIGS. 4A and 4B, in the state where the second heat shield plate 25 is fitted on the first heat shield plate 24, a circular seed rod through hole 28 is formed, and a notch portion is formed. 27 is completely covered. The outer diameter D2 of the lower jig 22 is equal to the outer diameter D1 of the heat shield jig 20, and the ratio D2 / D3 with the inner diameter D3 of the seed rod through hole 28 is in a range where 1.25 <D2 / D3 <5. And preferably 3 ≦ D2 / D3 ≦ 4. For example, when the outer diameter D2 is 200 mm, the inner diameter D3 of the seed rod through hole 28 is set within a range of about 50 mm to 66 mm.

  As shown in FIG. 6A, the upper jig 21 extends in three directions, and is directly fixed to the three connecting pieces 31 each having a bolt through hole 33 in the vicinity of the tip and the starting seed rod 3. It has a mounting hole 32 for the center. A heat escape space is formed on both sides of each connecting piece 31 so that heat does not accumulate in the vicinity of the seed bar portion 8 and heat from the heater 12 is released above the core tube 11. As shown in FIG. 6 (b), the mounting hole 32 has a mounting hole step portion 34 having a small diameter on the upper side and a large diameter on the lower side. By engaging with the rod step portion 7, the heat shield jig 20 is fixed at a predetermined position of the starting seed rod 3.

  Next, a procedure for attaching the heat shield jig 20 to the glass fine particle deposit 1 will be described.

(Assembly of heat shield jig)
As shown in FIGS. 2 to 6, first, three suspension bolts 23 are inserted from the lower side of the first heat shield plate 24 of the lower jig 22. Next, the first adjustment nut 26 </ b> A is screwed into each suspension bolt 23, and the suspension bolt 23 is inserted into the bolt through hole 33 of the upper jig 21. Thereafter, the second adjustment nut 26B is screwed into each suspension bolt 23. The screwing positions of the adjusting nuts 26A and 26B are such that when the heat shield jig 20 is engaged with the starting seed rod 3, the first heat shield plate 24 at the lower end deposits the tapered glass particles on the glass particle deposit 1. It is adjusted so as to be arranged in the vicinity of the upper part of the part 2.

(Installation of heat shield jig)
Next, the assembled heat shield jig 20 is lifted, and the upper end portion 6 of the seed rod portion 8 is inserted into the attachment hole 32 of the upper jig 21 from below with the second heat shield plate 25 removed. Since the glass particulate deposit 1 is heavy, when setting it on the connecting member 14, it is necessary to set it while holding the seed bar portion 8 with a balancer or the like. At this time, the cutout portion 27 of the first heat shield plate 24 is required. The first heat shield plate 24 is moved to the seed rod portion 8 side so as not to contact the glass fine particle deposit 1 with the seed rod portion 8 side facing. As a result, the lower portion of the seed rod portion 8 can be disposed in the seed rod through hole 28 from the cutout portion 27 of the first heat shield plate 24 even when the glass particulate deposit 1 is held by a balancer or the like. Then, the upper jig 21 is engaged with the seed rod step 7 of the starting seed rod 3 by lowering the heat shield jig 20 toward the glass particulate steady deposition portion 4 side of the glass particulate deposit 1.

  At this time, three sets of adjustment nuts 26A and 26B are arranged so that the first heat shield plate 24 is horizontally disposed at the boundary portion between the tapered glass particle depositing portion 2 and the seed rod portion 8 above the glass particle depositing body 1. Adjust the position. Finally, by fitting the second heat shield plate 25 on the first heat shield plate 24, the mounting of the heat shield jig 20 is completed.

(Installation of glass particulate deposit)
Thereafter, the glass particulate deposit 1 to which the heat shield jig 20 is attached is connected to the connecting member 14 and suspended in the sintering furnace 10.

  Next, as a method for manufacturing a glass base material, a sintering process of a glass fine particle deposit will be described.

(Sintering process of glass particulate deposits)
By heating the inside of the furnace tube 11 to about 1600 ° C. by the heater 12, the glass fine particle deposit 1 is sintered and made transparent. At this time, the lower jig 22 of the heat shield jig 20 is disposed at the boundary portion between the tapered glass fine particle deposition portion 2 and the seed rod portion 8 above the glass fine particle deposit body 1. As a result, the glass fine particle deposit 1 is sintered while heat transmitted from the heater 12 and the transparent glass base material to the seed rod portion 8 is shielded.

  Thereby, the elongation of the starting seed bar 3 due to the heat of the heater 12 can be reliably prevented, and the area of the unsintered portion on the upper part of the glass fine particle deposit 1 can be reduced. Further, since the position of the lower jig 22 of the heat shield jig 20 can be adjusted by the adjusting nut 26 in the longitudinal direction of the glass fine particle deposit 1, each glass fine particle deposit 1 does not contact the glass fine particle deposit 1. In addition, the position of the lower jig 22 can be adjusted.

  As described above, according to the manufacturing method of the glass base material and the sintering furnace for manufacturing the glass base material of the present embodiment, the heat shield jig 20 having the position-adjustable lower jig 22 is directly attached to the seed rod portion 8. The lower jig 22 was fixed and arranged in the vicinity of the upper portion of the tapered glass particle deposition portion 2 on the glass particle deposition body 1. Thereby, since heat from the heater 12 or the like can be shielded from being transmitted to the upper portion of the lower jig 22 so as not to be transmitted to the seed rod portion 8, the elongation of the seed rod portion 8 can be reliably prevented. In addition, on the lower side of the lower jig 22, the upper portion of the tapered glass fine particle deposition portion 2 can be brought close to the heat zone, so that the area of the unsintered portion at the upper end portion of the glass fine particle deposit 1 can be reduced. it can.

  Further, since the position of the lower jig 22 can be adjusted in the longitudinal direction of the glass fine particle deposit 1, the position of the heat shield plate can be adjusted to the optimum position for each glass fine particle deposit 1 without contacting the glass fine particle deposit 1. Adjustments can be made.

(Second Embodiment)
Next, the manufacturing method of the glass base material which is 2nd Embodiment of this invention, and the sintering furnace which manufactures a glass base material are demonstrated based on FIG. In addition, detailed description is abbreviate | omitted by attaching | subjecting the same code | symbol to the member of the same structure as the said 1st Embodiment. Further, the assembly and sintering steps of the heat shield jig are the same as those in the first embodiment, so that the description thereof is omitted.

(Installation of heat shield jig)
As shown in FIG. 7, the sintering furnace 40 of the second embodiment is different from the first embodiment in that the heat shield jig 50 is fixed to a connecting member 41 that connects the starting seed bar 3. The heat shield jig 50 is fixed to the connecting member 41 in advance before the connecting member 41 penetrates into the core tube 11. The upper jig 51 has the same configuration as that of the first embodiment except that the mounting hole 52 is a straight hole having no stepped portion. The connecting member 41 has a locking portion 42 that engages the heat shield jig 50. The mounting hole 52 of the upper jig 51 is engaged with the locking portion 42 from above the connecting member 41.

(Installation of glass particulate deposit)
In the sintering furnace 40 of the present embodiment, the glass particulate deposit 1 is suspended in the furnace core tube 11 with the heat shield jig 50 fixed to the connecting member 41 in advance. That is, the second heat shield plate 25 of the lower jig 22 is detached, and the glass particulate deposit 1 integrated with the starting seed rod 3 is connected to the connecting member 41 and suspended in the core tube 11.

  At this time, the boundary portion between the tapered glass particulate depositing portion 2 and the seed rod portion 8 on the upper portion of the glass particulate depositing body 1 is in the vicinity of the notch portion 27 of the first heat shield plate 24 engaged in the reactor core tube 11 in advance. Placed in. Position adjustment is performed by the three sets of adjustment nuts 26A and 26B so that the first heat shield plate 24 does not contact the glass particulate deposit 1 and is accurately disposed at the boundary portion. Finally, the second heat shield plate 25 is fitted onto the first heat shield plate 24 to complete the attachment of the glass particulate deposit 1 before sintering.

  When removing the glass particulate deposit 1, the second heat shield plate 25 can be removed, so that the glass particulate deposit 1 can be removed from the connecting member 41 with the thermal shield 50 attached. .

  The size of the heat shield jig 50 is determined by the sintering furnace 40 and the glass particulate deposit 1. For example, when the position H0 of the lower jig 22 is 300 mm from the upper end of the starting seed bar 3, the height H1 of the heat shield jig 50 is about 400 mm. Since other dimensions are the same as those of the first embodiment, description thereof is omitted.

  As described above, according to the glass base material manufacturing method and the sintering furnace for manufacturing the glass base material of the second embodiment, the heat shield jig 50 having the position-adjustable lower jig 22 is fixed to the connecting member 41. Then, the lower jig 22 was disposed in the vicinity of the upper portion of the tapered glass fine particle deposition portion 2 above the glass fine particle deposit body 1. Thereby, since heat from the heater 12 or the like can be shielded from being transmitted to the upper portion of the lower jig 22 so as not to be transmitted to the seed rod portion 8, the elongation of the seed rod portion 8 can be reliably prevented. Further, on the lower side of the lower jig 22, the upper part of the glass fine particle deposit 1 can be brought close to the heat zone, so that the area of the unsintered portion at the upper end of the glass fine particle deposit 1 can be reduced.

  Further, since the position of the lower jig 22 can be adjusted in the longitudinal direction of the glass fine particle deposit 1, the lower jig 22 can be moved to the optimum position for each glass fine particle deposit 1 without contacting the glass fine particle deposit 1. Position adjustment can be performed.

  In addition, this invention is not limited to each embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimension, numerical value, form, number, location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

  For example, although the sintering process has been described in the above embodiment, it can also be applied to a drawing furnace in the drawing process. Further, the mounting position of the heat shield jig may be a core tube or a lid part of a sintering furnace in addition to the starting seed bar and the connecting member.

  Next, the Example performed in order to confirm the effect of the manufacturing method of the glass base material which concerns on this invention is described.

Inner diameter D0 of used sintering furnace: 210mm
Used porous glass base material: Glass fine particle deposit with an outer diameter of 180 mm Sintering temperature: 1600 ° C
(Example)
Heat shielding jig used: Carbon type that is fixed directly to the starting seed rod (see the first embodiment)
Heat shield jig outer diameter D1: 200mm
Heat shield jig height H1: 220mm
Lower jig position H0: 320 mm from the upper end of the starting seed bar
Lower jig outer diameter D2: 200 mm, inner diameter D3: 55 mm
(Comparative example)
Heat shield jig used: None

  An example in which a glass particulate deposit was sintered in a sintering furnace for 1 month with a heat shield attached, and a glass particulate deposit for 1 month without a heat shield attached. In the comparative example sintered in the furnace, the frequency of occurrence of defects (base material falling, eccentricity of the upper end of the base material, fiber disconnection, base material crack) during sintering, wire drawing and pyrotechnics was tabulated. The results are shown in Table 1.

  As shown in Table 1, in the examples, the base material dropped and the base material crack did not occur at all. In addition, the eccentricity of the upper end of the base material and the fiber breakage could be kept low. This is because the lower jig can be adjusted to the optimum position on the lower side of the lower jig of the heat shield jig, so that the upper end of the glass particulate deposit is surely sintered. It can be inferred that the upper side was shielded by the heat shield jig, so that the elongation of the seed rod portion was suppressed. Even when the heat shield jig described in the second embodiment was used, substantially the same result was obtained.

  On the other hand, in the comparative example, the base material dropped and the base material crack occurred, and the eccentricity of the upper end of the base material and the fiber breakage occurred more than 10 times as much as the occurrence frequency of the example. Recognize. Therefore, the remarkable effect by attaching a heat shield jig | tool was able to be confirmed.

DESCRIPTION OF SYMBOLS 1 ... Glass fine particle deposit body, 2 ... Tapered glass fine particle deposition part, 3 ... Starting seed rod, 8 ... Seed rod part, 10,40 ... Sintering furnace, 11 ... Core tube, 12 ... Heater, 14, 41 ... Connection Members, 20, 50 ... heat shield jig, 21, 51 ... upper jig, 22 ... lower jig, 23 ... suspension bolt, 24 ... first heat shield plate, 25 ... second heat shield plate, 26 ... adjustment nut , 27 ... Notch, 28 ... Seed bar through hole, 31 ... Connecting piece, 32, 52 ... Mounting hole

Claims (3)

A glass base material manufacturing method in which glass particulates are deposited on a starting seed rod, and a glass particulate deposit comprising a seed rod portion, a tapered glass particulate deposition portion, and a glass particulate stationary deposition portion is heated and sintered by heat from a heat zone. There,
Near the top of the tapered glass particle deposition portion of the soot glass deposit body top, by arranging the heat shielding jig that enables position adjustment in the longitudinal direction for each of the glass particles deposit, said heat zone and the A method for producing a glass base material, comprising: sintering the glass fine particle deposit while shielding heat transmitted from the glass base material to the seed rod part. A core tube for depositing glass particulates on a starting seed rod and containing a glass particulate deposit comprising a seed rod portion, a tapered glass particulate deposition portion, and a glass particulate stationary deposition portion;
A heating furnace for heating and sintering the glass particulate deposit,
Near the top of the tapered glass particle deposition portion of the soot glass deposit body top, the glass base material, characterized in that a heat shield jig that enables position adjustment in the longitudinal direction for each of the glass particles deposit Sintering furnace. The thermal barrier jig sintering furnace of the glass base material according to claim 2, characterized in that it is fixed to the front Symbol seed rod portion.

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