JP2009132586A - Drawing method for glass preform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drawing method for a glass preform which can repeatedly use fitting members supporting dummy rods connected to a glass preform. <P>SOLUTION: Regarding the drawing method for a glass preform where dummy rods 21 connected to both the sides of a glass preform 20 are fitted with fitting members 22, respectively, so as to be connected, the fitting members 22 are grasped by chucks 23, respectively, and, while heating and softening the glass preform 20, the spacing between the dummy rods 21 is widened, so as to draw the glass preform 20, each fitting member 22 has a fitting part 22b in which the dummy rod 21 is fitted into one end side with a recessed shape, so as to be fitted, also, the other end side with a rod shape is grasped by the chuck 3, and, on drawing, in a state where the dummy rod 21 is inserted through, the upper end face 22e of the fitting part 22b is mounted with a heat shielding member 23 having an outside diameter equal to or larger than that of the upper end face 22e. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for stretching a glass base material.

In a manufacturing process of a glass base material such as a glass base material for an optical fiber, there is a process of stretching a glass base material obtained by sintering a glass fine particle deposit synthesized by a VAD method or the like to form a transparent glass. As the stretching process, the dummy rods connected to both ends of the glass base material are fitted and connected to the fitting members made of quartz glass, respectively, the fitting members are each gripped by the chuck, and the glass base material is heated. It is known that the glass base material is stretched by widening the gap between the dummy bars while being softened (see, for example, Patent Document 1).
It is also known to define a difference between the outer diameter of the dummy bar and the inner diameter of the fitting portion of the fitting member so that the dummy bar and the fitting member can be sufficiently fixed (see, for example, Patent Document 2). ).

JP-A-6-24784 JP-A-6-40737

In the glass base material stretching method described in Patent Document 1, the dummy bar can be shortened by the length of the fitting member, which is suitable for manufacturing a large glass base material. However, since the dummy rod and the fitting member are integrated by passing the pins through both sides and fixing them with screws, the glass base material is not a perfect connection, and the drawing direction changes during drawing. May bend.
As described in Patent Document 2, even when the gap between the outer diameter of the dummy rod and the inner diameter of the fitting portion of the fitting member is defined, if the fitting member is repeatedly used, the fitting member is Because it is heated by the heat during stretching and deteriorates (devitrifies and scrapes, etc.), the tip of the fitting member deforms, the inner diameter of the fitting part changes, the screw loosens, and fixing is insufficient There was. In this case, there is a problem that a deviation occurs in the stretching direction during stretching of the glass base material, and the glass base material after stretching is bent. Moreover, the manufacturing cost of a glass base material will start by the replacement frequency of a fitting member becoming high.

  Although it is possible to keep the fitting member away from the heating furnace, which is a heat source for drawing, to prevent deterioration due to heat, in this case, when setting the glass base material in the heating furnace, It becomes impossible to set, and accurate stretching cannot be performed.

  Accordingly, an object of the present invention is to provide a glass base material stretching method that can repeatedly use a fitting member that supports a dummy rod connected to a glass base material.

  The glass base material stretching method according to the present invention capable of solving the above-described problems is achieved by connecting and connecting the dummy rods connected to both ends of the glass base material to the fitting members, respectively. The glass base material is stretched by extending the glass base material by widening the gap between the dummy bars while being softened by heating the glass base material with a chuck, wherein the fitting member has a concave shape The other end side of the rod shape is gripped by a chuck, and the dummy rod is inserted into the concave one end side end surface while being stretched. A heat shield member having an outer diameter equal to or larger than the end surface on one end side is mounted.

  Moreover, in the extending | stretching method of the glass base material which concerns on this invention, it is preferable that the material of the said dummy rod, the said fitting member, and the said heat insulation member is quartz glass.

  In the glass base material stretching method according to the present invention, it is preferable that the heat shield member is configured to reduce light transmission by reflecting light or scattering transmitted light.

  Moreover, in the extending | stretching method of the glass base material which concerns on this invention, it is preferable that the space | interval of the said heat-shielding member and the said dummy rod which penetrates the said heat-shielding member is 0.05 mm or more and 1.0 mm or less.

  In the glass base material stretching method according to the present invention, it is preferable that a thickness of the heat shield member is 5 mm or more.

  According to the present invention, the concave one end side end surface, which is the side facing the glass base material, of the fitting member that connects the dummy rods connected to both ends of the glass base material is equal to or larger than the one end side end surface. By mounting the heat shield member having the outer diameter, it is possible to prevent the fitting member from being heated by the heat of the heating furnace during stretching. As a result, it is possible to prevent deterioration of the fitting member due to heat at the time of stretching, so that the glass base material is reliably supported by preventing changes in the inner diameter of the fitting portion due to deterioration, loosening of screws, etc. Can do. Moreover, since a fitting member can be used repeatedly, the manufacturing cost of a glass base material can be restrained low.

Hereinafter, an example of an embodiment according to the glass base material stretching method of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing a lower part of a stretching apparatus for performing a glass base material stretching method according to an embodiment of the present invention, FIG. 2A is a plan view of a heat shield member fitted with a fitting member, and FIG. (B) is a longitudinal sectional view showing the fitting portion side of the heat shield member with the fitting member attached, and FIG. 3 shows the structure of the connecting portion between the dummy rod and the fitting member, and is taken along the line III-III in FIG. FIG.

  The glass base material stretching method according to the present embodiment uses the stretching device 10 as shown in FIG. 1 to heat the glass base material 20 and connect the dummy bars 21 and 21 connected to both ends of the glass base material 20. This is a method of extending the glass base material 20 by widening the gap. The glass base material 20 has, for example, a clad portion 20b that is made transparent after depositing glass particles on a glass rod 20a having a core, and dummy rods 21 are connected to both ends of the glass rod 20a, respectively. .

  A stretching apparatus 10 shown in FIG. 1 has a heating furnace 11 including a heater 12 and a furnace core tube 13 that heat and soften the vicinity of the lower end portion of the glass base material 20 in order to stretch the glass base material 20. A fitting member 22 is attached to each end of the dummy bar 21 connected to both ends of the glass base material 20, and the fitting member 22 is gripped by the stretching chuck 23. Although only the lower side is shown in FIG. 1, the upper side is provided with a fitting member 22 having the same structure with the up-down direction reversed and an extension chuck 23, and is connected to the upper dummy rod 21. Yes.

  When the glass base material 20 is stretched, the upper stretching chuck 23 is moved toward the heating region of the heating furnace 11 so that the glass base material 20 is gradually fed into the heating furnace 11 and the lower stretching chuck 23 is moved. By moving the glass base material 20 at a higher speed than the upper stretching chuck 23 and taking the glass base material 20, the softened portion of the glass base material 20 softened in the furnace core tube 13 is stretched downward. It has become. Thereby, the glass base material reduced in diameter to a desired diameter is obtained.

  As shown in FIGS. 1 and 2, a fitting section 22b having a large outer diameter is provided at the upper end of the rod-shaped portion 22a of the fitting member 22, and the upper end surface of the fitting section 22b. At the center, a recess 22c is formed in which the lower end of the dummy bar 21 can be inserted and fitted. The fitting portion 22b is provided with a mounting through hole 22d in the radial direction, and the dummy rod is formed by the pin 24 passing through the mounting through hole 22d and the through hole 21a formed in the lower end portion of the dummy rod 21. 21 and the fitting member 22 are connected. Further, as shown in FIG. 3, a plurality (four in this embodiment) of screws 25 are attached to the fitting portion 22b in the radial direction, and the lower end portion of the dummy bar 21 is firmly fixed. . The screws 25 are preferably provided on both the upper side and the lower side of the pin 24.

  As shown in FIG. 2A, a circular heat shield member 30 covering the entire upper end surface (one end surface) 22e of the fitting portion 22b is provided on the upper end surface 22e of the fitting portion 22b of the fitting member 22. It is installed. The heat shield member 30 has an outer diameter that is equal to or larger than the outer diameter of the fitting portion 22b. Further, the outer diameter of the heat shield member 30 is smaller than the inner diameter of the heating furnace 11. The heat shield member 30 can move up and down together with the fitting member 22 without contacting the inner wall 11 a of the heating furnace 11. A through hole 31 into which the dummy bar 21 can be inserted is provided in the center of the heat shield member 30. If the material of the dummy rod 21, the fitting member 22, and the heat shield member 30 is quartz glass, the respective thermal expansion coefficients are equal, and thus displacement of each other can be prevented. Moreover, since the upper and lower thickness of the heat shield member 30 is likely to be distorted if it is too thin, it is preferably 5 mm or more.

  Moreover, it is preferable that the heat shielding member 30 is a member that reflects light from the inside of the heating furnace 11 or scatters transmitted light to reduce the amount of transmitted light. For example, by rubbing the surface of the heat shield member 30 with sandpaper or the like to make frosted glass or an opaque member, the amount of light or heat energy reaching the fitting member 22 is reduced, and the fitting member 22 is deteriorated. Can be prevented.

  Moreover, it is preferable that the space | interval (alpha) (refer FIG. 2) of the thermal insulation member 30 and the dummy rod 21 which penetrates this thermal insulation member 30 is 0.05 mm or more and 1.0 mm or less. That is, it is desirable to provide the through hole 31 so that the inner diameter of the through hole 31 of the heat shield member 30 is larger than the outer diameter of the dummy rod 21 by α. In this way, by reducing the gap between the dummy bar 21 and the heat shield member 30 to 0.05 mm or more and 1.0 mm or less, it is easy to shield light and heat acting on the fitting member 22. Deterioration can be prevented more reliably.

  At the start of stretching, the glass base material 20 is introduced into the heating furnace 11 from above, and heating starts near the lower end of the glass base material 20. At that time, the lower fitting member 22 approaches the heating region in the heating furnace 11, but the light and heat reaching the fitting member 22 are shielded by the heat shielding member 30 as described above to prevent deterioration. At the end of stretching, the vicinity of the upper end of the glass base material 20 is introduced into the heating furnace 11, and the upper fitting member 22 approaches the heating region in the heating furnace 11. Light and heat reaching the joint member 22 are shielded to prevent deterioration.

  According to the glass base material stretching method of the present embodiment described above, the fitting that is a surface facing the glass base material 20 in the fitting member 22 that connects the dummy rods 21 connected to both ends of the glass base material 20. The fitting member 22 is heated by the heat of the heating furnace 11 during stretching by mounting the heat shield member 30 having an outer diameter equal to or larger than the upper end surface 22e on the upper end surface 22e of the portion 22b. Can be prevented. Thereby, since the deterioration of the fitting member 22 due to heat at the time of stretching can be prevented, a change in the inner diameter of the concave portion 22c of the fitting portion 22b due to the deterioration, loosening of the screw 25, and the like are prevented, and the glass base material is prevented. 20 can be reliably supported. Moreover, since the fitting member 22 can be used repeatedly, the manufacturing cost of the glass base material 20 can be suppressed low.

In the embodiment described above, a circular flat plate is exemplified as the heat shield member 30 that shields light and heat, but a shape other than a flat plate or a shape other than a circle may be used. For example, like the heat shield member 30A shown in FIG. 4, it is possible to provide a cylindrical portion 32 that fits and covers the upper end portion of the fitting portion 22b along the outer periphery of the heat shield member 30A. In this case, the heat shield member 30 </ b> A can be reliably shielded by preventing the heat shield member 30 </ b> A from falling off the fitting member 22.
Further, as shown in FIG. 5, the heat shield member 30 </ b> B can be sandwiched between the dummy bar 21 and the fitting member 22. Also in this case, the heat shield member 30B can be prevented from falling off the fitting member 22, and can be reliably shielded.

  In the above-described embodiment, the vertical stretching method for stretching the glass base material 20 downward has been described. However, the horizontal stretching method for horizontally stretching the stretching apparatus 10 and the glass base material 20 is used. It is also possible to apply. When carrying out the horizontal stretching method, the glass base material 20 is preferably rotated with its central axis as the rotation axis.

  A quartz glass dummy rod 21 having an outer diameter of 30 mm and a length of 200 mm connected to both ends of a glass base material 20 having an outer diameter of 100 mm and a length of 600 mm is made of quartz glass having an inner diameter of 31 mm, an outer diameter of 40 mm, and a length of 200 mm. The fitting member 22 was inserted and connected. At this time, a heat shield member 30 made of quartz glass having an outer diameter of 60 mm and a thickness of 10 mm was attached to the end face of the fitting member 22. The fitting member 22 is gripped by the stretching chuck 23, and the lower end portion of the glass base material 20 is heated to 1800 ° C. in the heating furnace 11 and stretched to an outer diameter of 50 mm. Divided. After the above stretching process was repeated twice a day for 2 weeks, the bending of the stretched glass base material was measured. As a result, the maximum bending was 1 mm. On the other hand, as a result of performing the same drawing process without providing the heat shield member 30, the bending became a maximum of 4 mm. From this, it was found that when the heat shield member 30 is used, the glass base material at the time of stretching can be stably held and can be stretched straight.

It is a schematic block diagram which shows the lower part of the extending | stretching apparatus which enforces the extending | stretching method of the glass base material concerning embodiment of this invention. (A) is a top view of the thermal insulation member which fitted the fitting member, FIG.2 (B) is a longitudinal cross-sectional view which shows the fitting part side of the thermal insulation member which fitted the fitting member. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 1 showing a structure of a connection portion between a dummy bar and a fitting member. It is a longitudinal cross-sectional view which shows the modification of a heat shield member. It is a longitudinal cross-sectional view which shows the modification of a heat shield member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Stretching apparatus 11 Heating furnace 20 Glass base material 21 Dummy rod 22 Fitting member 22b Fitting part 22c Recess 23 Chuck 30, 30A, 30B Heat shielding member

Claims (5)

The dummy bars connected to both ends of the glass base material are fitted and connected to the fitting members, respectively, the dummy members are gripped by the chucks, and the glass base material is heated and softened while the dummy bars are connected. A glass base material stretching method that stretches the glass base material with a gap between each other,
The fitting member has a fitting portion for inserting and fitting the dummy rod on one end side of the concave shape, and the other end side of the rod shape is gripped by a chuck, and the concave shape is inserted in the state where the dummy rod is inserted when extending. A heat-shielding member having an outer diameter equal to or larger than that of the one end side end face is attached to one end side end face of the glass base material.   The glass base material stretching method according to claim 1, wherein the dummy rod, the fitting member, and the heat shield member are made of quartz glass.   3. The glass base material stretching method according to claim 1, wherein the heat shield member reflects light or scatters transmitted light to reduce the amount of transmitted light.   The glass according to any one of claims 1 to 3, wherein an interval between the heat shield member and the dummy bar penetrating the heat shield member is 0.05 mm or greater and 1.0 mm or less. Stretching method of base material.   The glass base material stretching method according to any one of claims 1 to 4, wherein a thickness of the heat shield member is 5 mm or more.

Images