JP4593499B2 - Glass rod stretching apparatus and glass rod stretching method - Google Patents

Description

  The present invention relates to a glass rod stretching apparatus and a glass rod stretching method for stretching a solid or hollow glass rod such as an optical fiber preform or a quartz tube.

  Conventionally, a glass rod stretching apparatus for stretching a solid glass rod such as an optical fiber preform or a hollow glass rod such as a quartz tube has been proposed. The glass rod stretching apparatus has, for example, an oxyhydrogen flame burner or an electric heating furnace as a heating means for heating the glass rod, heats the glass rod gripped at both ends in the stretching direction, and removes the glass rod from the end. Sequentially melt and soften and pull in the stretching direction. In this case, for example, the glass rod stretching apparatus sequentially heats the glass rod inserted into the core tube of the electric heating furnace from the lower end portion toward the upper end portion, and stretches the melt softening portion of the glass rod vertically downward. . In this way, the glass rod stretching device stretches the glass rod to a desired outer diameter.

  In such a glass rod drawing apparatus, a cylinder that covers one open end (glass rod insertion port) of the furnace core tube together with the glass rod at the upper end portion of the electric heating furnace, that is, one end portion on the side where the glass rod is inserted into the furnace core tube. Some are provided with parts. For example, as shown in FIG. 12, such a glass rod stretching apparatus 500 includes an electric heating furnace 501 that heat-treats the glass rod 600, and a cylindrical portion 502 that covers the glass rod insertion port of the electric heating furnace 501 together with the glass rod. Have.

  Specifically, the electric heating furnace 501 has a furnace core tube 504 made of carbon that forms an insertion pipe for the glass rod 600 inside the furnace body 503, and further a heater 505 disposed on the outer periphery of the furnace core tube 504. And a heat insulating material 506 disposed on the outer periphery of the core tube 504 or the heater 505. On the other hand, the cylindrical part 502 is provided in the upper part of the electric heating furnace 501, covers the upper opening part 501a of the core tube 504 which is a glass rod insertion port inside, and forms a through-hole communicating with the core tube 504. Further, a lid 502 a that forms a through-hole through which the support rod 601 can be inserted and that substantially closes the upper opening end of the cylindrical portion 502 is attached to the upper opening end of the cylindrical portion 502. The cylindrical portion 502 to which the lid 502a is attached prevents inflow of outside air from the upper opening 501a that is a glass rod insertion port.

  In addition, when extending | stretching, generally the support rods 601 and 602 are each attached to the upper end part and lower end part of the glass rod 600. FIG. The support bars 601 and 602 are gripped by chucks 603 and 604, respectively.

  Here, when the glass rod stretching apparatus 500 stretches the glass rod 600, the electric heating furnace 501 heats the glass rod 600 introduced into the furnace core tube 504 by the heater 505, and the glass rod 600 is moved to the lower end portion. To melt and soften sequentially from top to bottom. At the same time, the glass rod 600 is tensioned in the vertical direction by the support rods 601 and 602 held by the chucks 603 and 604, and the glass melt 600 is stretched so that the melted and softened portions are gradually reduced to a desired outer diameter. The glass rod 600 thus stretched is drawn out of the core tube 504 through the lower opening 501b.

  In this case, in order to prevent the outside air from flowing into the core tube 504 into the internal space of the glass rod stretching apparatus 500, that is, the internal space formed by the cylindrical portion 502 to which the lid 502a is attached and the core tube 504. In addition, an inert gas such as argon gas (Ar gas) is supplied. By supplying the inert gas to the internal space, the internal space is filled with the inert gas and is maintained in a high pressure state (that is, a positive pressure state) as compared with the external atmospheric pressure. . This is to prevent the core tube 504, which is a carbon component, from being oxidized (ie, damaged) by oxygen in the outside air.

  In addition, as such a glass rod stretching apparatus, a cylindrical portion that can be expanded and contracted in the longitudinal direction of the cylindrical structure is provided at the upper end portion of the electric heating furnace, and the glass rod insertion port is covered together with the glass rod by the expandable and contractible cylindrical portion. (For example, see Patent Documents 1 and 2). The length of the support rod attached to the upper end portion of the glass rod can be made relatively short by making the upper cylindrical portion of the electric heating furnace extendable.

Japanese Patent Laid-Open No. 6-256034 JP 11-349342 A

  However, the above-described conventional glass rod stretching apparatus exposes the lower opening of the core tube, which is the outlet of the glass rod after the stretching process, to the outside of the apparatus, so that the internal space of the glass rod stretching apparatus is filled. A large amount of inert gas flows out from the lower opening of the core tube to the outside of the apparatus. This is because the inner diameter of the core tube is such that the glass rod before drawing can be inserted, and a large gap is generated between the glass rod after drawing and the inner wall of the core tube. That is, there is a problem that a large amount of inert gas has to be supplied to the internal space in order to maintain the inside of the core tube at a positive pressure. In addition, since the inert gas supplied to the internal space is generally expensive, it is desired to reduce the supply amount.

  The present invention has been made in view of the above circumstances, and provides a glass rod stretching apparatus and a glass rod stretching method capable of reducing the supply amount of inert gas necessary for maintaining the inside of a furnace core tube at a positive pressure. The purpose is to do.

  In order to solve the above-mentioned problems and achieve the object, a glass rod stretching apparatus according to claim 1 is a glass rod introduced into a furnace core tube of a heating furnace by heat treatment, and melted and softened by the heat treatment. In the glass rod drawing apparatus that draws the glass rod after the drawing into a desired outer diameter and draws out the glass rod after the drawing from the furnace core tube, the drawer that draws out the opening on the outlet side of the heating furnace and the glass rod after the drawing The tubular member is covered with a telescopic tubular member, and the tubular member is disposed vertically below the heating furnace to form a closed space communicating with the internal space of the furnace core tube. To do.

  According to a second aspect of the present invention, there is provided the glass rod stretching apparatus according to the above invention, wherein the gas supply unit that supplies an inert gas to the inner space of the core tube and the pressure detection that detects the pressure in the inner space of the cylindrical member. And a control unit that controls the inert gas flow rate of the gas supply unit based on the pressure detected by the pressure detection unit, and maintains the internal space of the cylindrical member in a positive pressure state by the inert gas. And.

According to a third aspect of the present invention, there is provided the glass rod stretching apparatus according to the above invention, wherein a gas supply unit that supplies an inert gas to the internal space of the core tube and a concentration for detecting a CO ₂ concentration in the internal space of the core tube. The flow rate of the inert gas in the gas supply unit is controlled based on the CO ₂ concentration detected by the detection unit and the concentration detection unit, and the internal space of the core tube is maintained in a positive pressure state by the inert gas. And a control unit.

According to a fourth aspect of the present invention, there is provided the glass rod stretching apparatus according to the above invention, wherein the pull-out means is connected to the glass rod from a vertical upper end portion, and stretches the melted and softened glass rod from the core tube. a support bar to draw the said closed space, and a grip portion for gripping the vertical vicinity of the lower end portion of the support rod, said tubular member is inserted through the support rod slidably, wherein the gripping And a lid for isolating the closed space and the gripping part by being positioned vertically above the part .

  According to a fifth aspect of the present invention, in the glass rod stretching apparatus according to the present invention, the lid variably adjusts the diameter of the opening through which the support rod is inserted.

According to a sixth aspect of the present invention, there is provided a glass rod stretching method in which a glass rod introduced into a core tube of a heating furnace is subjected to a heat treatment, and the glass rod melted and softened by the heat treatment is stretched to a desired outer diameter. In the glass rod stretching method for drawing out the processed glass rod from the furnace core tube, a tubular member that can expand and contract between the opening on the outlet side of the heating furnace and the drawing means for drawing out the glass rod after the drawing processing is used. The glass rod after covering is formed by forming a closed space that communicates with the internal space of the furnace core tube by arranging the cylindrical member vertically below the heating furnace, and extending the cylindrical member Is extracted into the closed space. According to a seventh aspect of the present invention, in the glass rod stretching method according to the present invention, an inert gas is supplied to the inner space of the furnace core tube, the pressure in the inner space of the cylindrical member is detected, and the detected pressure is reduced. Originally, the flow rate of the inert gas is controlled, and the internal space of the cylindrical member is maintained in a positive pressure state by the inert gas. The glass rod stretching method according to claim 8 is the above invention, wherein an inert gas is supplied to the internal space of the core tube, the CO ₂ concentration in the internal space of the core tube is detected, and the detected CO ₂ is detected. The flow rate of the inert gas is controlled based on _two concentrations, and the internal space of the furnace core tube is maintained in a positive pressure state by the inert gas.

  According to the present invention, the amount of inert gas discharged from the inert gas supplied to the inner space of the reactor core tube to the outside of the apparatus can be reduced, and the inner space of the reactor core tube is maintained in a positive pressure state. The glass rod stretching apparatus and the glass rod stretching method that can reduce the supply amount of the inert gas necessary to achieve the effect are achieved.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a glass rod stretching apparatus and a glass rod stretching method according to the present invention will be described in detail with reference to the accompanying drawings. The embodiment according to the present invention is an example embodying the present invention, and does not limit the technical scope of the present invention.

(Embodiment 1)
First, the glass rod stretching apparatus according to the first embodiment of the present invention will be described. FIG. 1 is a schematic diagram illustrating a configuration example of a glass rod stretching apparatus according to a first embodiment of the present invention. As shown in FIG. 1, the glass rod stretching apparatus 100 includes a heating furnace 1 that heat-treats a glass rod 15 that is an optical fiber preform, for example. The glass rod stretching apparatus 100 stretches the glass rod 15 melted and softened by the heat treatment of the heating furnace 1 to a desired outer diameter, and the stretched glass rod (hereinafter referred to as a stretched rod) 15a. Pull out from the heating furnace 1. In this case, for example, quartz glass support rods 16 and 17 are connected to the upper and lower ends of the glass rod 15, respectively. The upper support rod 16 is the upper chuck 18, and the lower support rod 17 is the lower chuck 19. The tension is applied to the glass rod 15 by moving the upper chuck 18 and the lower chuck 19 relatively apart from each other. The support rod 17 and the lower chuck 19 function as a drawing unit that draws the glass rod 15 melted and softened by the heat treatment of the heating furnace 1 from the heating furnace 1 while drawing the glass rod 15 to a desired outer diameter.

  Moreover, the glass rod extending | stretching apparatus 100 has the cylinder part 2 which covers the opening part (for example, lower opening part 3b of the furnace body 3 mentioned later) on the outlet side of the heating furnace 1. The cylindrical portion 2 is realized by using an expandable and contractible cylindrical member, and is disposed vertically below the heating furnace 1. As shown in FIG. 1, such a cylindrical portion 2 covers a space between the opening on the outlet side of the heating furnace 1 and the above-described extraction means (that is, the support rod 17 and the lower chuck 19), and the heating furnace 1. A closed space communicating with the inner space (the inner space of the core tube 4 described later) is formed.

  Next, the configuration of the heating furnace 1 described above will be described. As shown in FIG. 1, the heating furnace 1 includes a furnace core tube 4 into which a glass rod 15 is introduced into a furnace body 3, and a heater 5 that heat-treats the glass rod 15 introduced into the furnace core tube 4. And a heat-resistant heat insulating material 6 disposed on the outer periphery of the furnace core tube 4 or the heater 5. The heating furnace 1 includes Ar gas supply units 7 and 8 for supplying argon gas (Ar gas) to the internal space of the furnace core tube 4, a radiation thermometer 9 for measuring the temperature of the heater 5, and an extended rod 15a. And an outer diameter measuring instrument 10 for measuring the outer diameter. Furthermore, the heating furnace 1 is formed in the furnace body 3 for the Ar gas ejection section 11 for ejecting Ar gas to the temperature measurement window formed in the furnace body 3 for the radiation thermometer 9 and the outer diameter measuring instrument 10. The outer diameter measurement window has Ar gas ejection portions 12 and 13 for ejecting Ar gas.

  The furnace core tube 4 is realized using, for example, carbon, and forms an internal space into which the glass rod 15 is introduced, that is, the internal space of the heating furnace 1 described above. In such a core tube 4, for example, a glass rod 15 is introduced via an upper opening 3 a (opening side opening of the heating furnace 1) of the furnace body 3, and a lower opening 3 b (heating furnace) of the furnace body 3. The drawn rod 15a is pulled out through the opening 1 of the first drawing side. In this case, the gap between the inner wall of the furnace body 3 and the glass rod 15 at the upper opening 3a is smaller than the gap between the inner wall of the furnace body 3 and the stretched rod 15a at the lower opening 3b.

  The heater 5 is an electric heater, for example, and is disposed on the outer periphery of the core tube 4. Such a heater 5 heat-treats the glass rod 15 introduced into the core tube 4 and melts and softens the glass rod 15 so that it can be stretched. In this case, the heater 5 heat-processes sequentially, for example from the lower end part of the glass rod 15 toward an upper end part by changing the relative position of the heating furnace 1 and the glass rod 15 gradually.

  Ar gas supply units 7 and 8 supply Ar gas to the internal space of the core tube 4. Specifically, the Ar gas supply unit 7 supplies Ar gas in the vicinity of the outlet side opening of the core tube 4 through the air supply pipe 7a. In this case, the Ar gas supply unit 7 sufficiently supplies Ar gas to the internal space of the core tube 4 and the closed space formed by the above-described tube portion 2, and the internal space of the core tube 4 and the tube portion 2 are closed. The space is filled with Ar gas and the internal space of the core tube 4 is maintained in a positive pressure state. In addition, in the air supply pipe 7a shown in FIG. 1, the pipe line A1 and the pipe line A2 communicate with each other.

  Here, it is preferable that the ejection direction of the air supply pipe 7a is downward. This is because the pressure in the tube portion 2 is difficult to increase because the upward flow in the core tube 4 is strengthened when the direction of ejection of the air supply tube 7a is upward. Further, it is preferable that the outlets of the air supply pipe 7 a are installed on the entire circumference in the circumferential direction of the core tube 4, and Ar gas is ejected uniformly in the circumferential direction of the core tube 4. As a result, the effect of confining the Ar gas in the cylindrical portion 2 is enhanced, and the pressure in the cylindrical portion 2 is likely to increase.

  On the other hand, the Ar gas supply unit 8 supplies Ar gas to the vicinity of the inlet side opening of the furnace core tube 4 through the supply tube 8a. In this case, the Ar gas supply unit 8 supplies Ar gas to the internal space of the core tube 4 and forms an Ar gas film or wall near the inside of the upper opening 3a. The Ar gas supply unit 8 prevents the inflow of outside air from the upper opening 3a into the inner space of the core tube 4 by forming such an Ar gas film or wall, and the core tube 4 and outside air (especially oxygen). To prevent contact.

  The radiation thermometer 9 radiates, for example, infrared rays to the heater 5 through a temperature measurement window formed in the furnace body 3 and measures the surface temperature of the heater 5. The outer diameter measuring device 10 is obtained by, for example, emitting laser light to the extended rod 15a in the core tube 4 through the outer diameter measuring window formed in the furnace body 3, thereby scanning the extended rod 15a. The outer diameter of the drawn rod 15a is measured based on the projected image.

  The Ar gas ejection section 11 ejects Ar gas into a temperature measurement window formed in the furnace body 3 so that the radiation thermometer 9 measures the surface temperature of the heater 5, and an Ar gas film or wall is formed in the temperature measurement window. Form. The Ar gas ejection section 11 forms such an Ar gas film or wall, thereby allowing the outside air to flow into the furnace body 3 from the temperature measurement window, that is, contact between the core tube 4 and the outside air (especially oxygen). To prevent. The Ar gas ejection parts 12 and 13 eject Ar gas into an outer diameter measurement window formed in the furnace body 3 so that the outer diameter measuring instrument 10 measures the outer diameter of the stretched rod 15a. An Ar gas film or wall is formed. The Ar gas ejection parts 12 and 13 prevent the inflow of the outside air from the outside diameter measurement window into the core tube 4 by forming the film or wall of the Ar gas. ) To prevent contact.

  Next, the configuration of the cylindrical portion 2 described above will be described. As shown in FIG. 1, the cylindrical portion 2 includes a telescopic cylindrical body 21 that is stretchable, an upper lid 22 that connects one open end of the telescopic cylindrical body 21 and the heating furnace 1, and the other of the telescopic cylindrical body 21. And a lower lid 23 that closes the open end. Moreover, the cylinder part 2 has an inner lid 24 through which the support rod 17 is slidably inserted. The lower chuck 19 that holds the support rod 17 is fixed to the support plate 20. The support plate 20 is detachably attached to the outside of the lower lid 23.

  The telescopic cylinder 21 is a telescopic cylinder having, for example, a bellows structure, and one open end is connected to the upper lid 22 and the other open end is connected to the lower lid 23. The telescopic cylinder 21 in which the upper lid 22 and the lower lid 23 are connected to both ends includes a lower opening 3 b of the furnace body 3 (that is, an opening on the outlet side of the heating furnace 1), a support rod 17, and a lower chuck 19. And a closed space communicating with the internal space of the core tube 4 (closed space of the cylinder portion 2 described above) is formed.

  The upper lid 22 has one end fixed to the lower end portion of the furnace body 3 and the other end connected to the telescopic cylinder 21, and a conduit that communicates the closed space of the cylinder portion 2 and the internal space of the core tube 4. Form. In this case, the closed space communicates with the internal space of the core tube 4 through a pipe line formed in the upper lid 22. Further, the upper lid 22 is formed with a window in which a glass or plastic light transmissive member 22a is fitted in a part of the pipe line. The operator can visually recognize the extended rod 15a in the closed space of the cylindrical portion 2 through the light transmissive member 22a.

  The lower lid 23 has a telescopic cylinder body 21 connected to a surface facing the upper lid 22, and a support plate 20 is detachably connected to a surface opposite to the connection surface of the telescopic cylinder body 21. The lower lid 23 has a cylindrical portion that forms a storage portion 23 a that stores the lower chuck 19 in the closed space of the cylindrical portion 2, and has an inner lid 24 in the vicinity of the end of the cylindrical portion. In this case, the lower lid 23 removably connects the support plate 20 to which the lower chuck 19 is fixed, and stores the lower chuck 19 in the storage portion 23a.

  The inner lid 24 is realized by using, for example, a carbon felt material, and an opening through which the support rod 17 is slidably inserted is formed.

  The glass rod stretching apparatus 100 having such a configuration is a heating furnace that drives the heating furnace 1 so that the glass rod 15 fixed at a predetermined position using the upper chuck 18 is displaced along the furnace core tube 4. A driving unit (not shown), an extension driving unit (not shown) that moves the support rod 17 and the lower chuck 19 while extending the cylindrical part 2 and applies tension to the glass rod 15, and a heating furnace driving unit, And a control unit that controls each drive of the stretching drive unit. In this case, the control unit controls each drive of the heating furnace driving unit and the stretching driving unit based on the outer diameter of the stretched rod 15a measured by the outer diameter measuring instrument 10, and the outer portion of the stretched rod 15a is controlled. Adjust the diameter to the desired outer diameter. The controller controls the driving of the heater 5 based on the surface temperature of the heater 9 measured by the radiation thermometer 9 and adjusts the temperature of the heater 5 to a temperature suitable for the heat treatment of the glass rod 15. To do.

  Next, the configuration of the telescopic cylinder 21 described above will be described. FIG. 2 is a schematic view illustrating the cross-sectional structure of the telescopic cylinder 21. As shown in FIG. 2, the telescopic cylinder 21 is mainly composed of glass fibers 21 a formed in a stretchable bellows structure or bellows structure, and is formed on the inner wall of the glass fibers 21 a, that is, on the wall on the closed space side of the cylindrical portion 2. This is realized by forming the metal film 21b. In this case, the metal film 21b can improve the heat resistance and airtightness of the glass fiber 21a. In addition, a shape holding ring 21c for holding the shape of the telescopic cylinder 21 is inserted into each part that protrudes outside the telescopic cylinder 21 and inside the glass fiber 21a.

  The telescopic cylinder 21 formed by the glass fiber 21a and the metal film 21b has heat resistance that can withstand a high temperature of about 200 ° C., for example, and between the closed space of the cylinder part 2 and the outside of the cylinder part 2. To achieve high airtightness. In addition, as a metal material of the metal film 21b formed into a film (that is, coating) on the glass fiber 21a, for example, aluminum, copper, nickel, and the like can be given.

  Below, the glass rod extending | stretching method concerning Embodiment 1 of this invention is demonstrated. FIG. 3 is a schematic view illustrating a state in which the glass rod 15 as a base material is conveyed onto the glass rod stretching apparatus 100. FIG. 4 is a schematic view illustrating a state in which the glass rod 15 is introduced into the furnace core tube 4 of the heating furnace 1. FIG. 5 is a schematic view illustrating a state in which the glass rod 15 is stretched. FIG. 6 is a schematic view illustrating a state where the drawn rod 15a and the support rod 17 are cut. FIG. 7 is a schematic view illustrating the state after the glass rod has been stretched. Hereinafter, the glass rod stretching method according to the first embodiment will be described with reference to FIGS.

  First, as shown in FIG. 3, the glass rod 15 as a base material is supported by using an upper chuck 18 that grips a support rod 16 connected to the upper end portion, and is set on the upper portion of the glass rod stretching apparatus 100. . In this case, the glass rod stretching device 100 is in a state in which the tubular portion 2 is contracted (that is, a state in which the telescopic tubular body 21 is folded). Further, the glass rod stretching apparatus 100 has a support plate 20 detachably connected to the lower lid 23, and includes a lower chuck 19 fixed to the support plate 20 and a support rod 17 held by the lower chuck 19. Have. In this case, the support rod 17 is slidably inserted into the inner lid 24, and this end is positioned in the vicinity of the heater 5 in the internal space of the core tube 4. Further, the lower chuck 19 is housed in the housing portion 23 a of the lower lid 23.

  Further, the glass rod stretching apparatus 100 is in a resting state at this point (specifically, before the glass rod 15 is introduced into the core tube 4). That is, in this resting state, the glass rod stretching apparatus 100 supplies Ar gas to the internal space of the core tube 4 and the closed space of the cylindrical portion 2 to maintain the internal space of the core tube 4 in a positive pressure state. The temperature of the inner space of the core tube 4 is raised to a high temperature by the heater 5 in advance. In this case, the upper opening 3 a of the heating furnace 1 is covered with a lid 25. The lid 25 is made of, for example, quartz, and a through hole 25a is formed at a substantially central portion. The effect of the lid 25 will be described later.

  Next, the glass rod stretching apparatus 100 is lifted toward the glass rod 15 after the lid 25 of the upper opening 3 a is removed. In this case, as shown in FIG. 4, the glass rod stretching apparatus 100 introduces the glass rod 15 into the core tube 4 from the upper opening 3 a and connects the lower end 15 b of the glass rod 15 and the support rod 17. To do. At the same time, the glass rod stretching apparatus 100 supplies Ar gas having a flow rate of 50 to 90 [l / min] to the internal space of the furnace core tube 4 and the closed space of the cylindrical portion 2 by the Ar gas supply unit 7 described above. In addition, Ar gas having a flow rate of 20 [l / min] was supplied to the vicinity of the inlet opening of the core tube 4 by the Ar gas supply unit 8 described above. Thereby, the internal space of the core tube 4 is always maintained in a positive pressure state filled with Ar gas.

  Thereafter, the glass rod stretching apparatus 100 heats the glass rod 15 with the heater 5 and sets the heating furnace 1 to gradually raise the heater 5 from the lower end portion to the upper end portion of the glass rod 15. Raise sequentially. At the same time, the glass rod stretching apparatus 100 lowers the lower lid 23 together with the lower chuck 19 to extend the cylindrical portion 2, and moves the support rod 17 gripped by the lower chuck 19 vertically downward. By such an operation of the glass rod stretching apparatus 100, the glass rod 15 is gradually heat-treated from the lower end portion toward the upper end portion to melt and soften, and tension is applied in the vertical direction as the support rod 17 moves. It is done. In this case, the melt softened portion of the glass rod 15 is stretched to a desired outer diameter while being stretched vertically downward.

  As shown in FIG. 5, the glass rod thus stretched, that is, the stretched rod 15 a is drawn out from the internal space of the core tube 4 to the closed space of the tube portion 2 together with the support rod 17. The glass rod stretching apparatus 100 continues to apply tension to the glass rod 15 that is sequentially melted and softened by moving the lower chuck 19 vertically downward while extending the cylindrical portion 2 further vertically downward. In this case, the glass rod 15 is sequentially stretched from the lower end portion toward the upper end portion. As a result, the extended rod 15a is sequentially drawn out from the core tube 4 to the closed space of the cylindrical portion 2 through the lower opening 3b. In this manner, the glass rod stretching apparatus 100 stretches, for example, a glass rod 15 having an outer diameter of 100 mm into a stretched rod 15a (an optical fiber preform or a quartz tube or the like) having an outer diameter of 50 mm.

  When the glass rod 15 has been stretched into a glass rod 15 having a desired outer diameter (stretched rod 15a), the temperature of the heater 5 is lowered and the cylindrical portion 2 is reduced and stretched. The lower end of the rod 15a is exposed to the outside. Thereafter, the stretched rod 15a and the support rod 17 are separated. Specifically, after the temperature of the heater 5 is lowered, the glass rod stretching apparatus 100 removes the support plate 20 from the lower lid 23 and leaves the support plate 20 and the lower chuck 19 on, for example, the floor or the work table. Next, the glass rod stretching device 100 raises the lower lid 23 and folds the telescopic cylindrical body 21 to contract the cylindrical portion 2. In this case, the inner lid 24 rises while making the closed space of the cylindrical portion 2 substantially airtight with respect to the outside and sliding sequentially along the side walls of the support rod 17 and the extended rod 15a. As a result, the stretched rod 15a exposes the vicinity of the end portion together with the support rod 17, as shown in FIG. The stretched rod 15a and the support rod 17 exposed in this way are separated by a predetermined cutting device 27.

  Note that a hook 26 is provided on the tubular portion 2 in a state where the telescopic tubular body 21 is folded (that is, in a contracted state) so that the tubular portion 2 does not extend, for example, in the cutting process of the stretched rod 15a and the support rod 17. It is attached. As shown in FIG. 6, the hook 26 connects the upper lid 22 and the lower lid 23 to prevent the lower lid 23 from dropping, that is, the cylinder portion 2 from being extended.

  The inner lid 24 is formed with an opening through which the support rod 17 is slidably inserted. Thus, when the support plate 20 is detached from the lower lid 23 and the telescopic cylinder 21 is folded, The closed space of the part 2 and the outside can be substantially blocked.

  Thereafter, the drawn rod 15a is taken out from the glass rod drawing apparatus 100 as shown in FIG. In this way, the glass rod stretching apparatus 100 realizes a stretched rod 15a having a desired outer diameter based on the glass rod 15 as a base material. Specifically, for example, based on a glass rod 15 (base material) having an outer diameter of 100 mm, a stretched rod 15a (an optical fiber base material or a quartz tube) having an outer diameter of 50 mm was obtained. On the other hand, the glass rod stretching device 100 is returned to the state shown in FIG. 3 (a state substantially the same as the stage before the glass rod 15 is introduced into the core tube 4), and enters the resting state described above. In this case, the upper opening 3 a of the heating furnace 1 is covered with the above-described quartz lid 25.

  When the lid 25 is put on the upper opening 3a of the heating furnace 1, the internal space of the furnace core tube 4 to which Ar gas is supplied is maintained in a positive pressure state, and high-temperature Ar gas is appropriately supplied from the through hole 25a. Discharge. As a result, the lid 25 can suppress the inflow of the high-temperature Ar gas into the closed space of the cylindrical portion 2 and can maintain the internal space of the furnace core tube 4 in a positive pressure state with a relatively small supply amount of Ar gas. . Thereby, it is possible to achieve both the prevention of deterioration of the cylindrical portion 2 (particularly the telescopic cylindrical body 21) caused by the contact with the high-temperature Ar gas and the reduction of the Ar gas supply amount. Specifically, when the lid 25 is placed on the upper opening 3a, the Ar supply units 7 and 8 described above supply Ar gas at a flow rate of 20 [l / min], respectively, thereby The space was maintained in a positive pressure state filled with Ar gas.

  Here, the glass rod stretching apparatus 100 described above covers the lower opening 3b, which is the outlet of the stretched rod 15a, in the closed space of the cylindrical portion 2, and the inner wall of the lower opening 3b and the stretched rod 15a The upper opening 3a having a smaller gap between the glass rod 15 and the inner wall than the gap is exposed to the outside. Since such a glass rod stretching apparatus 100 discharges Ar gas through the upper opening 3a having a small gap, conventional glass rod stretching that discharges Ar gas to the outside through the lower opening on the outlet side. Compared with the apparatus (see FIG. 12), the amount of Ar gas discharged to the outside of the apparatus is small.

  Further, the glass rod stretching apparatus 100 described above has a cylindrical portion 2 vertically below the heating furnace 1 and stretches the glass rod 15 melted and softened inside the furnace core tube 4 so as to stretch vertically downward. It was. For this reason, Ar gas supplied to the internal space of the core tube 4 is heated by the heater 5 and flows vertically upward, and is discharged through the gap of the upper opening 3a. That is, high-temperature Ar gas (for example, Ar gas at 1000 to 2000 ° C.) heated by the heater 5 is difficult to flow into the closed space of the cylindrical portion 2 located vertically below the heating furnace 1. As a result, even if the lower chuck 19 is completely covered with the telescopic cylinder 21, there is little fear of failure due to heat, so that the lower chuck 19 can be completely covered with the telescopic cylinder 21. In a conventional glass rod stretching apparatus (see FIG. 12) having a cylindrical portion vertically above the heating furnace, the upper chuck cannot be completely covered because there is a concern about failure due to the heat of the upper chuck. Therefore, it is necessary to provide a through-hole communicating with the outside of the apparatus in order to insert the support rod in the upper lid attached to the cylindrical portion of the conventional glass rod stretching apparatus, thereby reducing the confidentiality in the closed space. . Therefore, the glass rod stretching apparatus 100 has a smaller amount of Ar gas discharged to the outside of the apparatus than the conventional glass rod stretching apparatus (see FIG. 12). In addition, Ar gas (for example, Ar gas having a temperature of 200 ° C. or less) less affected by the heater 5 flows into the closed space of the cylindrical portion 2, and the closed space of the cylindrical portion 2 becomes excessively hot. This can be prevented, and the heat resistance design of the cylindrical portion 2 (particularly the telescopic cylindrical body 21) is facilitated.

  Further, since the Ar gas in the reactor core tube 4 flows vertically upward (upper flow), even if a foreign matter exists in the internal space of the reactor core tube 4, the foreign matter is moved upward by the Ar gas in the upper flow. It is discharged from the opening 3a to the outside of the apparatus. Therefore, it is possible to prevent such foreign matter from adhering to the stretched rod 15a.

  As described above, in the first embodiment of the present invention, the opening on the outlet side of the heating furnace from which the glass rod after the drawing process is drawn out, and the drawing means (for example, the support) for drawing out the glass rod after the drawing process The space between the rod 17 and the lower chuck 19) is covered with an expandable and contractible cylindrical member so as to form a closed space communicating with the internal space of the core tube of the heating furnace. For this reason, the gap between the glass rod and the inner wall is small compared with the gap between the inner wall at the opening on the outlet side and the glass rod after the drawing process. Gas will be discharged. As a result, it is possible to reduce the amount of inert gas discharged from the inert gas supplied to the interior space of the reactor core tube to the outside of the apparatus, and to maintain the interior space of the reactor core tube in a positive pressure state. A glass rod stretching apparatus and a glass rod stretching method that can reduce the supply amount of the necessary inert gas can be realized.

  Moreover, since such a cylindrical member is arrange | positioned vertically below the heating furnace, inflow of the high temperature inert gas to the internal space (namely, closed space mentioned above) of this cylindrical member can be suppressed. As a result, the lower chuck can be completely covered with the telescopic cylinder, and the closed space of the cylindrical member can be prevented from becoming excessively hot, and the heat resistance design of the cylindrical member can be facilitated. .

  Further, since the glass rod is stretched vertically downward while extending the cylindrical member vertically below, the inert gas can flow vertically upward while maintaining the internal space of the reactor core tube in a positive pressure state. . For this reason, even if there is a foreign substance in the inner space of the core tube, the foreign substance can be discharged to the outside by the inert gas of the upper flow, and such a foreign substance adheres to the glass rod after the drawing process. This can be prevented.

  In addition, since the cylindrical member has a stretchable structure such as a bellows structure, it is necessary to stretch the glass rod as compared to the case of using a cylinder with a predetermined shape that is difficult to freely expand and contract. The length of the support bar can be further shortened.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. In the first embodiment described above, Ar gas adjusted to a predetermined flow rate is supplied to the inner space of the core tube 4, but in this second embodiment, Ar supplied to the inner space of the core tube 4 is supplied. The gas flow rate is controlled based on the pressure in this internal space.

  FIG. 8 is a schematic diagram illustrating a configuration example of the glass rod stretching apparatus according to the second embodiment of the present invention. As shown in FIG. 8, the glass rod stretching apparatus 200 according to the second embodiment includes a heating furnace 50 instead of the heating furnace 1 of the glass rod stretching apparatus 100 according to the first embodiment described above. The heating furnace 50 has the same configuration as that of the heating furnace 1 of the glass rod stretching apparatus 100 described above, and is further detected by a pressure detection unit 51 that detects the pressure in the internal space of the tube part 2, and the pressure detection unit 51. And a control unit 52 for controlling the Ar gas flow rate of the Ar gas supply unit 7 based on the determined pressure. In this case, the pressure detection unit 51 communicates with the internal space of the cylinder part 2 via the pipe 51a. Other configurations are the same as those of the first embodiment, and the same reference numerals are given to the same components.

  The pressure detection part 51 detects the pressure of the internal space of the cylinder part 2 via the pipe | tube 51a. The pressure detection unit 51 transmits the pressure detection result of the internal space to the control unit 52. The pressure detection unit 51 detects the pressure in the internal space of the cylinder unit 2 based on the control of the control unit 52. In this case, the pressure detection unit 51 may detect the pressure every time a predetermined time elapses (that is, periodically), may always detect the pressure, or may detect a desired timing (for example, the glass rod 15). The pressure may be detected at the time of introduction or when the cylinder portion 2 is extended.

  The control unit 52 functions to control the Ar gas flow rate of the Ar gas supply unit 7 based on the pressure in the internal space of the tube unit 2 and to maintain the internal space of the reactor core tube 4 in a positive pressure state with Ar gas. Specifically, the control unit 52 causes the pressure detection unit 51 to detect the pressure in the internal space of the cylinder unit 2 and acquires the pressure detection result detected by the pressure detection unit 51. Next, the control unit 52 controls the Ar gas flow rate of the Ar gas supply unit 7 based on the pressure detection result. In this case, the control unit 52 controls the Ar gas flow rate of the Ar gas supply unit 7 so that the internal space of the cylinder part 2 is maintained in a positive pressure state by Ar gas filling the internal space of the cylinder part 2. For example, the control unit 52 controls the Ar gas flow rate of the Ar gas supply unit 7 so that the pressure in the internal space of the cylinder unit 2 is increased by about 5 to 10 [Pa] with respect to the atmospheric pressure.

  Here, the glass rod stretching apparatus 200 gradually increases the volume of the closed space of the tube portion 2 when the glass rod 15 is stretched while extending the tube portion 2 as in the first embodiment. As the volume of the closed space increases, the pressure in the inner space of the core tube 4 gradually decreases. In this case, the control unit 52 grasps the pressure drop in the internal space of the core tube 4 based on the pressure detection result acquired from the pressure detection unit 51, and the internal space of the tube unit 2 is in a negative pressure state (that is, atmospheric pressure). The Ar gas flow rate of the Ar supply unit 7 is increased so that the pressure state is not low). Thus, the control part 52 always maintains the internal space of the cylinder part 2 at the time of the extending | stretching process of the glass rod 15 in a positive pressure state.

  On the other hand, the glass rod stretching apparatus 100 gradually reduces the volume of the closed space of the tube portion 2 when the tube portion 2 is reduced in the same manner as in the first embodiment described above after the glass rod 15 is stretched, for example. . As the volume of the closed space decreases, the pressure in the internal space of the cylinder portion 2 gradually increases. In this case, the control unit 52 grasps the pressure increase in the internal space of the core tube 4 based on the pressure detection result acquired from the pressure detection unit 51, and the internal space of the core tube 4 is in an excessive positive pressure state (for example, The Ar gas flow rate of the Ar supply unit 7 is reduced to the minimum necessary so as not to be in a high pressure state exceeding the range of +5 to +10 [Pa] with respect to the atmospheric pressure. In this way, the control unit 52 maintains the internal space of the cylinder part 2 in a proper positive pressure state (a state in which the pressure is about 5 to 10 [Pa] higher than the atmospheric pressure), while supplying the Ar gas. To save money.

  Thus, the control unit 52 always reduces the Ar gas flow rate of the Ar supply unit 7 to the minimum necessary in accordance with the pressure in the internal space of the cylindrical part 2 that increases or decreases with the volume change of the closed space of the cylindrical part 2 described above. The amount of Ar gas supplied to the internal space of the core tube 4 can be saved to the minimum necessary while maintaining the internal space of the cylindrical portion 2 at a positive pressure state.

  The pressure detection unit 51 may be configured to detect the pressure in the inner space of the furnace core tube 4, but the temperature inside the furnace core tube 4 becomes high, so that the heat detection problem of the pressure detection unit 51 occurs. By detecting the pressure in the internal space of the cylinder portion 2 as in the present embodiment, more stable pressure control is possible.

  In addition, the glass rod extending | stretching method concerning this Embodiment 2 is the same as that of Embodiment 1 mentioned above except controlling the flow volume of Ar gas based on the pressure of the internal space of the cylinder part 2. FIG. That is, in the glass rod stretching method according to the second embodiment, the Ar gas in the Ar supply unit 7 further corresponds to the pressure in the internal space of the cylindrical part 2 that increases or decreases with the volume change of the closed space of the cylindrical part 2. The flow rate is always controlled to the minimum necessary, and the supply amount of Ar gas is saved.

  As described above, in the second embodiment of the present invention, in addition to the configuration of the first embodiment described above, the pressure in the internal space of the cylindrical portion is detected, and based on the pressure detection result in the internal space, The flow rate of the inert gas supplied to the internal space of this cylinder part was controlled. For this reason, the flow rate of this inert gas can always be controlled to the minimum necessary in accordance with the pressure in the internal space of the cylindrical portion that increases or decreases with the volume change of the closed space of the cylindrical portion. As a result, while enjoying the operational effects of the first embodiment described above, the supply amount of the inert gas supplied to the internal space of the cylindrical portion is kept to a minimum while maintaining the internal space of the core tube in a positive pressure state. Can save you money.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. In the second embodiment described above, the flow rate of Ar gas supplied to the inner space of the cylindrical portion 2 is controlled based on the pressure in the inner space. However, in the third embodiment, the inside of the reactor core tube 4 is controlled. The flow rate of Ar gas is controlled based on the CO ₂ concentration in the space.

FIG. 9 is a schematic diagram illustrating a configuration example of the glass rod stretching apparatus according to the third embodiment of the present invention. As shown in FIG. 9, a glass rod stretching apparatus 300 according to the third embodiment includes a heating furnace 60 instead of the heating furnace 50 of the glass rod stretching apparatus 200 according to the second embodiment described above. The heating furnace 60 includes a CO ₂ concentration detection unit 61 instead of the pressure detection unit 51 of the tube unit 2 of the glass rod stretching apparatus 200 described above, and includes a control unit 62 instead of the control unit 52. In this case, the CO ₂ concentration detector 61 communicates with the internal space of the core tube 4 via the tube 61a. Other configurations are the same as those of the second embodiment, and the same components are denoted by the same reference numerals.

The CO ₂ concentration detector 61 detects the concentration of carbon dioxide (CO ₂ ) contained in the internal space of the core tube 4 based on the gas flowing from the internal space of the core tube 4 via the tube 61a. The CO ₂ concentration detection unit 61 transmits the concentration detection result of the internal space to the control unit 62. Such CO ₂ concentration detection unit 61 detects the CO ₂ concentration in the internal space of the core tube 4 under the control of the control unit 62. In this case, the CO ₂ concentration detector 61 may detect (i.e. periodically) CO ₂ concentration each time the predetermined time elapses, may be detected at all times CO ₂ concentration, the desired The CO ₂ concentration may be detected at timing (for example, when the glass rod 15 is introduced and when the cylindrical portion 2 is extended).

The control unit 62 controls the Ar gas flow rate of the Ar gas supply unit 7 based on the concentration of CO ₂ contained in the inner space of the reactor core tube 4 and maintains the inner space of the reactor core tube 4 in a positive pressure state by Ar gas. To function. Specifically, the control unit 62 causes the CO ₂ concentration detection unit 61 to detect the CO ₂ concentration in the internal space of the reactor core tube 4 and acquires the concentration detection result detected by the CO ₂ concentration detection unit 61. Next, the control unit 62 controls the Ar gas flow rate of the Ar gas supply unit 7 based on the concentration detection result. For example, the control unit 62 controls the Ar gas flow rate of the Ar gas supply unit 7 so that the CO ₂ concentration in the internal space of the core tube 4 is 400 [ppm] or less.

Here, the glass rod stretching apparatus 300 gradually increases the volume of the closed space of the tube portion 2 when, for example, the glass rod 15 is stretched while extending the tube portion 2 as in the first embodiment. . As the volume of the closed space increases, the pressure in the inner space of the core tube 4 gradually decreases. If the pressure continues to decrease in this way, the internal space of the core tube 4 may be in a negative pressure state relative to the atmospheric pressure and may flow in outside air. When outside air flows into the inner space of the furnace core tube 4, oxygen contained in the outside air oxidizes and deteriorates the carbon core tube 4. In such an oxidation reaction, CO ₂ is generated, and as a result, the CO ₂ concentration in the internal space of the core tube 4 increases. In this case, the control unit 62 grasps the increase in the CO ₂ concentration in the internal space of the core tube 4 based on the concentration detection result acquired from the CO ₂ concentration detection unit 61, and oxidizes (that is, deteriorates) the core tube 4. The Ar gas flow rate of the Ar supply unit 7 is increased so as to inhibit the progress of the above.

In this way, the control unit 62 always needs the Ar gas flow rate of the Ar supply unit 7 in accordance with the CO ₂ concentration in the inner space of the core tube 4 that changes with the volume change of the closed space of the tube unit 2, for example. The supply amount of Ar gas supplied to the inner space of the core tube 4 can be saved to the minimum necessary while controlling to the minimum and maintaining the inner space of the core tube 4 in a positive pressure state. The Ar gas supply unit 7 controlled by the control unit 62 has an Ar gas flow rate (desirably, a minimum necessary Ar gas necessary for setting the CO ₂ concentration in the inner space of the core tube 4 to 400 ppm or less, for example). The Ar gas is supplied to the interior space of the furnace core tube 4 at a flow rate. As described above, when the CO ₂ concentration in the inner space of the core tube 4 is maintained at 400 ppm or less, the progress of oxidation (deterioration) of the core tube 4 is substantially prevented, and the core tube 4 in this case deteriorates. It is almost equivalent to what is not.

The glass rod stretching method according to the third embodiment is the same as that of the first embodiment described above except that the flow rate of Ar gas is controlled based on the CO ₂ concentration in the inner space of the core tube 4. That is, in the glass rod stretching method according to the third embodiment, the Ar gas flow rate in the Ar supply unit 7 is always controlled to the minimum necessary in accordance with the CO ₂ concentration in the inner space of the furnace core tube 4. To save on the supply.

As described above, in the third embodiment of the present invention, in addition to the configuration of the first embodiment described above, the concentration of CO ₂ contained in the inner space of the core tube is detected, and the concentration detection result of this inner space is detected. Based on the above, the flow rate of the inert gas supplied to the interior space of the core tube was controlled. For this reason, the flow rate of the inert gas is always set to the minimum necessary (that is, the flow rate of the inert gas necessary to prevent the deterioration of the core tube) corresponding to the CO ₂ concentration in the inner space of the core tube. Can be controlled. As a result, while enjoying the operational effects of the first embodiment described above, the supply amount of the inert gas supplied to the internal space of the core tube is kept to a minimum while maintaining the internal space of the core tube in a positive pressure state. Can save you money.

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described. In the first embodiment described above, the support rod 17 or the stretched rod 15a is slid into the opening of a predetermined size formed in the inner lid 24. In the fourth embodiment, the support rod 17 or the stretched rod 15a is stretched. The diameter of the opening of the inner lid for sliding the used rod 15a is made variable.

  FIG. 10 is a schematic diagram illustrating a configuration example of the glass rod stretching apparatus according to the fourth embodiment of the present invention. As shown in FIG. 10, a glass rod stretching apparatus 400 according to the fourth embodiment has a tubular portion 70 instead of the tubular portion 2 of the glass rod stretching apparatus 100 according to the first embodiment described above. The cylinder part 70 has an inner lid 71 instead of the inner lid 24 of the cylinder part 2 of the glass rod stretching apparatus 100 described above. The inner lid 71 has an adjusting portion 71a that can change the diameter of the opening through which the support rod 17 or the extended rod 15a is slidably inserted and adjusts the diameter of the opening. Other configurations are the same as those of the first embodiment, and the same reference numerals are given to the same components.

  FIG. 11 is a perspective view schematically showing a configuration example of the inner lid 71. As shown in FIG. 11, the inner lid 71 has, for example, an iris structure, and has an opening 71b whose diameter is changed by the iris structure. In this case, the inner lid 71 changes the diameter of the opening 71b by operating the adjusting portion 71a. For example, when the glass rod stretching device 400 completes the stretching process of the glass rod 15, the inner lid 71 adjusts the diameter of the opening 71 b in accordance with the outer diameter of the support rod 17, and the opening 71 b having this diameter. The support rod 17 is slidably inserted through the base. Thereafter, the inner lid 71 adjusts the diameter of the opening 71b in accordance with the outer diameter of the extended rod 15a, and the extended rod 15a is slidably inserted into the opening 71b having this diameter.

  In this way, the inner lid 71 can adjust the gap between the support rod 17 or the extended rod 15a and the opening 71b to a minimum. As a result, as shown in FIG. 6, in the state where the support plate 20 is removed from the lower lid 23, the telescopic cylinder 21 is folded, and the cylindrical portion 2 is contracted, the inner lid 71 has a member with a different outer diameter as the opening 71b. Even if it is made to pass through, the closed space of the cylinder part 70 and the exterior can be substantially interrupted | blocked. On the other hand, when there is no member (for example, the support rod 17 or the extended rod 15a) to be inserted into the inner lid 71, the inner lid 71 fully closes the opening 71b by the operation of the adjusting portion 71a.

  In addition, the glass rod extending | stretching method concerning this Embodiment 4 is the same as that of Embodiment 1 mentioned above except adjusting the diameter of the opening part 71b of the inner cover 71. FIG. That is, in the glass rod stretching method according to the fourth embodiment, when the support rod 17 or the stretched rod 15a is slidably inserted into the opening 71b of the inner lid 71, the support rod 17 or the stretched rod The diameter of the opening 71b of the inner lid 71 is adjusted according to the outer diameter of 15a.

  As described above, in the fourth embodiment of the present invention, in addition to the configuration of the first embodiment described above, the outer diameter of a member (for example, the support rod 17 or the stretched rod 15a) inserted through the inner lid is adjusted. The diameter of the opening of the inner lid was changed. For this reason, the gap between the member inserted into the opening of the inner lid and the opening can be adjusted to the minimum. As a result, the effects of the first embodiment described above can be enjoyed, and the airtightness between the closed space of the cylindrical member via the inner lid and the outside of the apparatus can be further enhanced.

  In the first to fourth embodiments of the present invention, the glass rod 15 that is an optical fiber preform is stretched to obtain a stretched rod 15a (that is, an optical fiber preform) having a desired outer diameter. Not limited to this, a hollow glass rod such as a quartz tube may be stretched using a base material to obtain a hollow glass rod having a desired outer diameter (that is, a quartz tube).

In the first to fourth embodiments of the present invention, Ar gas is supplied to the inner space of the core tube 4. However, the present invention is not limited to this, and other inert gases such as He gas and N ₂ gas are used as Ar gas. Instead of this, it may be supplied to the internal space of the core tube 4. In this case, an inert gas supply unit that supplies such other inert gas may be provided in place of the Ar gas supply units 7 and 8 described above.

In the second and third embodiments of the present invention, the flow rate of the inert gas is controlled based on the pressure in the internal space of the cylindrical portion 2 or the CO ₂ concentration in the internal space of the reactor core tube 4. Not limited to this, a combination of the second and third embodiments described above may be used. In this case, for example, to the glass rod elongating apparatus 200 according to the second embodiment described above, and add the CO ₂ concentration detection unit 61 for detecting a CO ₂ concentration in the internal space of the core tube 4, the control unit 52, the pressure sensing The flow rate of the inert gas may be controlled based on the pressure detection result from the unit 51 and the concentration detection result from the CO ₂ concentration detection unit 61.

  Furthermore, in the fourth embodiment of the present invention, the glass rod stretching apparatus 400 having the configuration in which the inner lid 71 is provided instead of the inner lid 24 of the glass rod stretching apparatus 100 according to the first embodiment described above is illustrated. In addition to the above, the glass rod stretching apparatus having a configuration in which the inner lid 71 is provided instead of the middle lid 24 of the glass rod stretching apparatus 200 according to the second embodiment described above may be used. A glass rod stretching apparatus having an inner lid 71 instead of the inner lid 24 of the glass rod stretching apparatus 300 may be used.

  Moreover, in Embodiment 1-4 of this invention, the position of the upper part of a glass rod was fixed, the heating furnace was raised along this glass rod, and the glass rod was extended by extending a cylinder part. However, the present invention is not limited thereto, and the glass rod or the heating furnace may be moved so that the relative position between the glass rod and the heating furnace (specifically, the heater) changes. In this case, for example, the position of the heating furnace may be fixed, the glass rod may be moved in a direction (for example, vertically downward) to be introduced into the core tube, and the cylindrical portion may be extended. While being introduced, both the heating furnace and the glass rod may be moved and the cylindrical portion may be extended.

  Furthermore, in Embodiments 2 and 3 of the present invention, the Ar gas flow rate of the Ar gas supply unit 7 is controlled. The Ar gas flow rate may be controlled.

It is a schematic diagram which shows one structural example of the glass rod extending | stretching apparatus concerning Embodiment 1 of this invention. It is a schematic diagram which illustrates the cross-section of an expansion-contraction cylinder. It is a schematic diagram which illustrates the state which set the glass rod which is a base material on the glass rod extending | stretching apparatus. It is a schematic diagram which illustrates the state which introduce | transduced the glass rod in the furnace core tube of a heating furnace. It is a schematic diagram which illustrates the state which extended | stretched the glass rod. It is a schematic diagram which illustrates the state cut | disconnected with the glass rod and support rod after an extending | stretching process. It is a schematic diagram which illustrates the state after completion | finish of the extending | stretching process of a glass rod. It is a schematic diagram which shows one structural example of the glass rod extending | stretching apparatus concerning Embodiment 2 of this invention. It is a schematic diagram which shows one structural example of the glass rod extending | stretching apparatus concerning Embodiment 3 of this invention. It is a schematic diagram which shows one structural example of the glass rod extending | stretching apparatus concerning Embodiment 4 of this invention. It is a perspective view which shows typically one structural example of the inner cover of the glass rod extending | stretching apparatus concerning Embodiment 4. FIG. It is a schematic diagram which shows one structural example of the conventional glass rod extending | stretching apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,50,60 Heating furnace 2,70 Cylinder part 3 Furnace body 3a Upper opening part 3b Lower opening part 4 Core tube 5 Heater 6 Heat insulating material 7,8 Ar gas supply part 7a, 8a Supply pipe 9 Radiation thermometer 10 Outer diameter Measuring instrument 11-13 Ar gas ejection part 15 Glass rod 15a Stretched rod 16, 17 Support bar 18 Upper chuck 19 Lower chuck 20 Support plate 21 Telescopic cylinder 21a Glass fiber 21b Metal film 22 Upper lid 23 Lower lid 23a Storage part 24 Inner lid 51 Pressure detection unit 52, 62 Control unit 61 CO ₂ concentration detection unit 71 Inner lid 71a Adjustment unit 71b Opening part 100, 200, 300, 400, 500 Glass rod stretching device

Claims (8)

A glass rod that heats a glass rod introduced into a core tube of a heating furnace, stretches the glass rod melted and softened by the heat processing to a desired outer diameter, and draws the glass rod after the stretching processing from the core tube In the stretching device,
A space between the opening on the outlet side of the heating furnace and the drawing means for pulling out the glass rod after the drawing process is covered with a stretchable tubular member, and the tubular member is vertically below the heating furnace. A glass rod stretching apparatus that is disposed and forms a closed space that communicates with an internal space of the core tube. A gas supply unit for supplying an inert gas to the internal space of the furnace core tube;
A pressure detector for detecting the pressure in the internal space of the tubular member;
A control unit that controls the flow rate of the inert gas in the gas supply unit based on the pressure detected by the pressure detection unit, and maintains the internal space of the cylindrical member in a positive pressure state by the inert gas; The glass rod stretching apparatus according to claim 1, further comprising a glass rod stretching apparatus. A gas supply unit for supplying an inert gas to the internal space of the furnace core tube;
A concentration detector for detecting the CO ₂ concentration in the internal space of the furnace core tube;
A control unit that controls the flow rate of the inert gas in the gas supply unit based on the CO ₂ concentration detected by the concentration detection unit, and maintains the internal space of the furnace core tube in a positive pressure state by the inert gas; The glass rod stretching apparatus according to claim 1, comprising: The withdrawal means is
A vertical rod upper end is connected to the glass rod, and a support rod that draws out the melted and softened glass rod from the core tube to the closed space, and
A gripping part for gripping the vicinity of the lower end in the vertical direction of the support bar, and
The cylindrical member is provided with a lid that slidably inserts the support bar and isolates the closed space and the gripping portion by being positioned vertically above the gripping portion. The glass rod extending | stretching apparatus as described in any one of Claims 1-3.   The glass rod stretching apparatus according to claim 4, wherein the lid variably adjusts a diameter of an opening through which the support rod is inserted. A glass rod that heats a glass rod introduced into a core tube of a heating furnace, stretches the glass rod melted and softened by the heat processing to a desired outer diameter, and draws the glass rod after the stretching processing from the core tube In the stretching method,
Covering between the opening on the outlet side of the heating furnace and the drawing means for pulling out the glass rod after the drawing process is covered with an elastic cylindrical member, and the cylindrical member is arranged vertically below the heating furnace. Then, a closed space communicating with the internal space of the furnace core tube is formed, and the glass rod after drawing is drawn into the closed space while the cylindrical member is extended. Supplying an inert gas to the interior space of the core tube,
Detecting the pressure in the internal space of the tubular member;
The glass rod according to claim 6, wherein the flow rate of the inert gas is controlled based on the detected pressure, and the internal space of the cylindrical member is maintained in a positive pressure state by the inert gas. Stretching method. Supplying an inert gas to the interior space of the core tube,
CO in the inner space of the core tube ₂ Detect the concentration,
CO detected ₂ The glass rod stretching method according to claim 6, wherein the flow rate of the inert gas is controlled based on the concentration, and the internal space of the furnace core tube is maintained in a positive pressure state by the inert gas.

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