JP2010189231A - Apparatus and method for thermoforming silica glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for thermoforming a silica glass each of which can give a high-quality thermoformed silica glass by retaining its axis. <P>SOLUTION: An apparatus 10 for silica glass thermoforming is provided with a carbon vessel 11 in which a columnar silica glass 1 is housed and a vacuum heating furnace 12 which heats the carbon vessel 11 to process the silica glass 1. The thermoforming apparatus 10 is further provided with a fall-preventive member 13 which prevents the silica glass 1 from falling while preventing the axis Ax of the silica glass 1 from deviating from the initial position. Next, the silica glass 1 is placed in the center of the bottom plate 16 of the carbon vessel 11, and the fall-preventive member 13 is fitted on the upper end surface 3 of the silica glass 1. Thereafter, the carbon vessel 11 is housed in the vacuum heating furnace 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a silica glass thermoforming apparatus and a thermoforming method for expanding the diameter of silica glass housed in a carbon container in a vacuum heating furnace.

  As an example of a conventional silica glass thermoforming apparatus and thermoforming method, as shown in FIG. 4, silica glass 102 is accommodated in a carbon container 101, and a load is applied to the silica glass 102 by a weight 104 through a felt material 103. There is a silica glass thermoforming apparatus 100 (see, for example, Patent Document 1).

JP 2002-53330 A

  In silica glass thermoforming, the silica glass base material made by the VAD method or the like has a characteristic (for example, refractive index distribution) that is symmetrical in the radial direction from the axial center. It is desirable to mold while maintaining the properties.

However, in the conventional silica glass thermoforming apparatus 100 disclosed in Patent Document 1, the length / outer diameter ratio is large in the process of crushing the columnar (cylindrical, rectangular parallelepiped, etc.) silica glass 102. It may become unstable and the silica glass 102 may fall or buckle, resulting in a displacement in the center position of the crushing. For these reasons, the shaft core of the silica glass 102 may be crushed while being tilted or bent during the heat forming.
As a result, the above-described symmetry is lost, and it becomes necessary to perform heat treatment for homogenization, which requires extra steps and time, leading to a decrease in productivity. In addition, since the surface portion of the silica glass is taken into the interior, it becomes impossible to remove the surface dirt, deposits, and the like, leading to a reduction in quality.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a silica glass thermoforming apparatus and a thermoforming method that can form a high-quality silica glass while holding the shaft core. There is.

  A silica glass thermoforming apparatus according to the present invention that can solve the above-mentioned problems comprises a carbon container in which a columnar silica glass is stored, and a heating furnace in which the carbon container is installed, and the carbon container A silica glass thermoforming apparatus for expanding the diameter of the silica glass within, contacting the top of the silica glass at the bottom, sliding the side surface with the inner surface of the carbon container, It is characterized by having a fall prevention member that prevents the silica glass from falling while preventing the shaft core from shifting from the initial position.

According to the silica glass thermoforming apparatus configured as described above, when the silica glass is heated to a high temperature in a vacuum heating furnace and is expanded while being melted, the shaft core is not displaced by the fall prevention member. Are positioned as follows.
As a result, the shaft core is held during the processing of the silica glass, so that it does not fall down or buckle, and a high-quality silica glass that maintains symmetry can be obtained. In addition, this makes it possible to minimize the time for heat treatment for homogenization and improve productivity.

  The silica glass thermoforming apparatus according to the present invention preferably includes a stopper member for preventing the collapse preventing member from being lowered below a certain height.

  According to the silica glass thermoforming apparatus configured as described above, when the fall-preventing member in contact with the silica glass is lowered to the set position, the fall is stopped by hitting the stopper member. This stop position is a position where the fall prevention member is separated from the silica glass when the axis of the silica glass is crushed to a state where the fall does not occur. Therefore, excessive interference of the fall prevention member with respect to the silica glass can be suppressed, and for example, the fall prevention member can be reliably prevented from being hardened while being embedded in the silica glass.

  Further, in the silica glass thermoforming apparatus according to the present invention, the fall prevention member is in contact with the side plate inscribed in the carbon container, and the top plate is in contact with the upper end surface of the silica glass and is larger than the upper end surface of the silica glass. It is preferable to provide an inclined plate that connects the peripheral edge of the top plate and the lower edge of the side plate.

  According to the silica glass thermoforming apparatus configured as described above, even when the silica glass falls down, the silica glass can be prevented from further falling down due to the inclination of the inclined plate.

  Further, in the silica glass thermoforming apparatus according to the present invention, the collapse prevention member includes a top plate having a central portion in contact with an upper end surface of the silica glass, and extends downward from a peripheral edge of the top plate. It is preferable that a side plate that is inscribed in the container, and three or more guide pins that are in contact with the side surface of the upper end portion of the silica glass on the lower surface of the central portion of the top plate.

  According to the silica glass thermoforming apparatus configured as described above, the silica glass shaft core is held by the three or more guide pins even when the silica glass is tilted, so that the silica glass is in a proper position. It can be corrected.

  The silica glass thermoforming apparatus according to the present invention includes a weight member that applies a load to the silica glass, and the fall prevention member abuts against the stopper member and stops descending. It is preferable that the guide pin starts to come off from the silica glass and the weight member continues to be loaded.

  According to the silica glass thermoforming apparatus thus configured, the silica glass can be crushed in a shorter time by setting the load for processing the silica glass by the weight member. Further, when the fall prevention member comes into contact with the stopper member and the lowering stops, the guide pin starts to come off from the silica glass, and the weight member continues to apply a load. Thereby, the excessive interference of the fall prevention member with respect to silica glass can be suppressed, and a higher quality silica glass can be obtained.

  Further, the silica glass thermoforming method according to the present invention capable of solving the above-described problems is caused by bringing the bottom surface of the fall prevention member into contact with the upper part of the columnar silica glass stored in the carbon container, and The side surface is slid with the inner surface of the carbon container, the carbon container is installed in a heating furnace, and the silica glass shaft core is not displaced from the original position by the fall prevention member, and the silica glass It is characterized in that the silica glass is subjected to diameter expansion processing so as not to fall down.

According to the silica glass thermoforming method configured as described above, when the silica glass is subjected to diameter expansion processing while being heated and melted at a high temperature in a vacuum heating furnace, the silica glass is positioned by the fall prevention member. While being processed.
Accordingly, since the shaft core is held during the processing of the silica glass, the possibility of falling or buckling is reduced, and a high-quality silica glass that maintains symmetry can be formed. In addition, this makes it possible to minimize the time for heat treatment for homogenization and improve productivity.

  According to the silica glass thermoforming apparatus and thermoforming method according to the present invention, since the shaft core is held by the fall-preventing member during the processing of the silica glass, the possibility of falling or buckling is reduced, and the symmetry is reduced. The held high quality silica glass can be molded. In addition, this makes it possible to minimize the time for heat treatment for homogenization and improve productivity.

The thermoforming apparatus which applies the thermoforming method of the silica glass which concerns on 1st Embodiment of this invention is shown, (a) is sectional drawing before thermoforming, (b) is sectional drawing during thermoforming, (c) is It is sectional drawing after heat forming. The thermoforming apparatus which applies the thermoforming method of the silica glass which concerns on 2nd Embodiment of this invention is shown, (a) is sectional drawing before thermoforming, (b) is sectional drawing during thermoforming, (c) is It is sectional drawing after heat forming. The thermoforming apparatus which applies the thermoforming method of the silica glass which concerns on 3rd Embodiment of this invention is shown, (a) is sectional drawing before thermoforming, (b) is sectional drawing during thermoforming, (c) is It is sectional drawing after heat forming. It is sectional drawing of the heat molding apparatus of the conventional silica glass.

  Hereinafter, a plurality of preferred embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a silica glass thermoforming apparatus according to a first embodiment of the present invention, wherein (a) is a cross-sectional view before thermoforming, (b) is a cross-sectional view during thermoforming, and (c) is after thermoforming. FIG.

  A silica glass thermoforming apparatus 10 according to a first embodiment of the present invention includes a carbon container 11 that houses a silica glass base material 1, and a vacuum heating furnace that melts and processes the silica glass base material 1 in the carbon container 11. 12. Furthermore, the thermoforming apparatus 10 is placed on the upper part of the silica glass base material 1, and the collapse preventing member 13 housed in the carbon container 11 and the stopper member 14 placed on the bottom of the carbon container 11 are provided. It is equipped with.

  As shown in FIG. 1A, the silica glass base material 1 has, for example, a cylindrical shape having a height dimension L1 of 350 mm and an outer diameter dimension D1 of 160 mm.

Desirable dimensions of the silica glass base material 1 suitable for use in the present embodiment are that the relationship between the height dimension L1 and the outer diameter dimension D1 of the silica glass base material 1 is 2 ≦ L1 / D1 ≦ 10. is there. By processing the silica glass base material 1 applicable to this, a more remarkable effect appears.
In addition, when L1 / D1 is 2 or less, the possibility of falling of the silica glass base material 1 is low even without the fall prevention member 13, and when L1 / D1 is 10 or more, the fall prevention member 13 is present. However, the possibility that the silica glass base material 1 falls due to buckling or the like increases.

The carbon container 11 is formed into a bottomed cylindrical shape using a carbon material, and includes a peripheral plate 15 and a bottom plate 16. The carbon container 11 is preferably a high-purity product having an ash content of 10 wtppm or less. If the amount of ash is large, impurities contained in the carbon components of the carbon container 11 and the fall prevention member 13 penetrate into the silica glass base material 1. Therefore, it becomes necessary to remove impurities by, for example, scraping the surface of the silica glass molded body 2 in a subsequent process.
The vacuum heating furnace 12 includes a heater (not shown) for installing the carbon container 11 therein and heating the carbon container 11.

Like the carbon container 11, the fall prevention member 13 is formed in a substantially lid shape using a carbon material. The fall prevention member 13 is arranged at a cylindrical side plate 17 inscribed in the carbon container 11 and a central position inside the side plate 17, abuts on the upper end surface of the silica glass base material 1, and the silica glass base material 1 The top plate 18 is larger than the upper end surface, and the inclined plate 19 connects the lower end edge of the side plate 17 and the peripheral edge of the top plate 18.
The outer diameter formed by the side plate 17 is slightly smaller than the inner diameter of the peripheral plate 15 of the carbon container 11. Further, the outer diameter of the top plate 18 is set to be about 0.1 mm to 4 mm larger than the outer diameter D1 of the upper end surface of the silica glass base material 1.

  The stopper member 14 is formed in a cylindrical shape, and is assembled on the bottom plate 16 of the carbon container 11 so as to be inscribed in the peripheral plate 15. The stopper member 14 has a set height dimension L3 in order to restrict the descent of the fall prevention member 13.

Next, with reference to FIG. 1 (a)-(c), the thermoforming method to which the silica glass thermoforming apparatus 10 of 1st Embodiment is applied is demonstrated.
First, the silica glass base material 1 is placed in the center of the bottom plate 16 of the carbon container 11, and the fall prevention member 13 is assembled to the upper end surface 3 of the silica glass base material 1. Thereafter, the carbon container 11 is accommodated in the vacuum heating furnace 12. Thereby, the axis | shaft core Ax of the silica glass base material 1 is hold | maintained because the top plate 18 of the fall prevention member 13 is contact | abutted to the upper end surface 3 of the silica glass base material 1 (refer Fig.1 (a)). .

  Next, the heater of the vacuum heating furnace 12 is driven and held at 1800 ° C. for 1 hour, then the heater is stopped, rapidly cooled to 1200 ° C., held for 1 hour, and then again at 0.5 ° C./min by program operation. The temperature is decreased to 1000 ° C. at a rate of Thereby, the silica glass base material 1 is crushed while expanding its diameter by its own weight with the upper end surface 3 kept in contact with the top plate 18 of the fall prevention member 13 (see FIG. 1B). ).

At this time, the fall prevention member 13 that abuts the top plate 18 on the upper end surface 3 of the silica glass base material 1 is lowered according to the amount of collapse of the silica glass base material 1. Then, at the position of the height dimension L3 of the stopper member 14 (downward stop position), the lower end of the fall prevention member 13 comes into contact with the upper end of the stopper member 14, and the fall of the fall prevention member 13 is stopped. During this time, the fall prevention member 13 prevents the silica glass base material 1 from falling even when a force that causes the silica glass base material 1 to fall toward the inclined surface 19 is generated.
The required height of the stopper member 14 varies depending on the size and viscosity of the glass to be processed, and therefore needs to be set optimally according to the silica glass base material to be processed.

  Next, the silica glass base material 1 is cooled after being crushed at a high temperature and then cooled, and, for example, formed into a silica glass molded body 2 having a height dimension L2 of 96 mm and an outer diameter dimension D2 of 305 mm (FIG. 1 (c)).

  As described above, according to the silica glass thermoforming apparatus 10 of the first embodiment of the present invention, the silica glass base material 1 is processed while being melted by being heated to a high temperature in the vacuum heating furnace 12. Further, the axis Ax is positioned by the fall prevention member 13. Thereby, since the axial center Ax is held during the processing of the silica glass base material 1, the possibility of falling or buckling is reduced, and a high-quality silica glass molded body 2 that maintains symmetry can be obtained. . In addition, this makes it possible to minimize the time for heat treatment for homogenization and improve productivity.

Further, when the fall prevention member 13 that is in contact with the silica glass base material 1 is lowered to the stop position H, the fall prevention member 13 is brought into contact with the stopper member 14 and stops descending.
This stop position is a position where the fall prevention member 13 is separated from the silica glass base material 1 when the axial center of the silica glass base material 1 is crushed to a state where it does not fall down. Therefore, excessive interference of the fall prevention member 13 with respect to the silica glass base material 1 can be suppressed. Thereby, for example, it can be reliably prevented that the fall prevention member 13 is hardened while being in the silica glass base material 1.

Moreover, according to the silica glass thermoforming method of the first embodiment of the present invention, when the silica glass base material 1 is processed while being heated and melted at a high temperature in the vacuum heating furnace 12, The fall prevention member 13 is brought into contact with the upper portion of the stored silica glass base material 1, and the carbon container 11 is installed in the heating furnace 12. Then, the silica glass base material 1 is heated so that the tilt prevention member 13 prevents the axis Ax of the silica glass base material 1 from deviating from the initial position and the silica glass base material 1 does not fall down. Is called.
Thereby, since the axial center Ax is held during the processing of the silica glass base material 1, the possibility of falling or buckling is reduced, and a high-quality silica glass molded body 2 that maintains symmetry can be formed. it can. In addition, this makes it possible to minimize the time for heat treatment for homogenization and improve productivity.

(Second Embodiment)
Next, a silica glass thermoforming apparatus and thermoforming method according to a second embodiment of the present invention will be described. FIG. 2 shows a thermoforming apparatus to which the silica glass thermoforming method according to the second embodiment of the present invention is applied, wherein (a) is a cross-sectional view before thermoforming, (b) is a cross-sectional view during thermoforming, c) is a cross-sectional view after thermoforming. In the following embodiments, the same or functionally similar components as those in the first embodiment described above are denoted by the same reference numerals in the drawings, and the description thereof is simplified or omitted.

  As shown in FIG. 2A, the silica glass thermoforming apparatus 20 according to the second embodiment of the present invention uses a fall prevention member 21 having three guide pins 22.

  The fall prevention member 21 has a top plate 24 whose central portion is in contact with the upper end surface 3 of the silica glass base material 1, and a side plate 23 extending downward from the periphery of the top plate 24. The guide pins 22 are integrally formed at substantially equal intervals in the circumferential direction so as to form an inner diameter dimension slightly larger than the outer diameter dimension of the silica glass base material 1 at the center portion of the lower surface of the top plate 24. It abuts on the upper side surface of the base material 1. The guide pin 22 may be assembled to the fall prevention member 21 as a separate part.

  Next, with reference to FIG. 2 (a)-(c), the thermoforming method of the silica glass to which the thermoforming apparatus 20 of 2nd Embodiment is applied is demonstrated.

  First, the silica glass base material 1 is placed in the center of the bottom plate 16 of the carbon container 11, and the guide pin 22 of the fall prevention member 21 is assembled to the upper end surface 3 of the silica glass base material 1. And the carbon container 11 is accommodated in the vacuum heating furnace 12 (refer Fig.2 (a)). Thereby, the fall prevention member 21 positions the axis Ax of the silica glass base material 1 by the guide pins 22.

  Next, after the heater of the vacuum heating furnace 12 is driven and heated, the temperature is lowered. Thereby, the silica glass base material 1 is crushed while expanding its diameter by its own weight with the upper end surface 3 held by the guide pins 22 (see FIG. 2B).

  At this time, the fall prevention member 21 is lowered according to the amount of collapse of the silica glass base material 1. Then, when the stopper member 14 is brought into contact with the upper end of the stopper member 14 at the height dimension L3 (lowering stop position H), the falling prevention member 21 is stopped from descending (see FIG. 2C). During this time, the fall prevention member 21 holds the axis Ax of the silica glass base material 1 by the guide pins 22 even if the silica glass base material 1 is tilted, so the silica glass base material 1 falls. Can be prevented.

  Next, the silica glass base material 1 is formed into a silica glass molded body 2 having a set size by being cooled after expanding the diameter while continuing to be crushed at a high temperature.

  As described above, according to the silica glass thermoforming apparatus 20 and the thermoforming method of the second embodiment of the present invention, the same effects as those of the first embodiment can be obtained. In particular, according to the present embodiment, since the fall prevention member 21 can be created with a simple configuration, man-hours and costs can be reduced.

(Third embodiment)
Next, a silica glass thermoforming apparatus and thermoforming method according to a third embodiment of the present invention will be described. FIG. 3 shows a thermoforming apparatus to which the silica glass thermoforming method according to the third embodiment of the present invention is applied, (a) is a cross-sectional view before thermoforming, (b) is a cross-sectional view during thermoforming, c) is a cross-sectional view after thermoforming.

  As shown in FIG. 3A, the silica glass thermoforming apparatus 30 according to the third embodiment of the present invention includes a fall prevention member 31 having three guide pins 32 and a weight member 33.

The fall prevention member 31 has a side plate 34 and a bottom plate 35. The guide pins 32 are integrally formed at substantially equal intervals in the circumferential direction so as to form an inner diameter dimension slightly larger than the outer diameter dimension of the silica glass base material 1 at the central portion of the lower surface of the bottom plate 35. .
The weight member 33 has a preset weight and is formed in a disk shape having a through hole 36 corresponding to the guide pin 32. The weight member 33 is disposed under the bottom plate 35 of the fall prevention member 31 by the guide pin 32 passing through the through hole 36, and is assembled so as to be movable in the vertical direction along the guide pin 32.

  Next, with reference to FIG. 3 (a)-(c), the thermoforming method of the silica glass to which the silica glass thermoforming apparatus 30 of 3rd Embodiment is applied is demonstrated.

First, the silica glass base material 1 is placed in the center of the bottom plate 16 of the carbon container 11. And the guide pin 32 of the fall prevention member 31 is assembled | attached to the upper end surface 3 of this silica glass base material 1. FIG. At this time, the weight member 33 comes into contact with the lower part of the bottom plate 35 of the fall prevention member 31 with the guide pin 32 passing through the through hole 36, and the center part of the lower surface of the weight member 33 is on the upper end surface 3 of the silica glass base material 1. It is in contact.
Next, the carbon container 11 is accommodated in the vacuum heating furnace 12 (see FIG. 3A). The fall prevention member 31 positions the axis Ax of the silica glass base material 1 with the guide pins 32, and the weight member 33 applies a load set on the silica glass base material 1.

  Next, after the heater of the vacuum heating furnace 12 is driven and heated, the temperature is lowered. Thereby, the silica glass base material 1 is pressed by the load of the weight member 33 in a state where the upper end surface 3 is held by the guide pin 32, and is crushed while expanding the diameter (see FIG. 3B). .

  At this time, the fall prevention member 31 is lowered according to the amount of collapse of the silica glass base material 1. Then, at the position of the height L3 of the stopper member 14 (downward stop position H), the stopper member 14 comes into contact with the upper end to stop the downward movement (see FIG. 3C). During this time, the fall prevention member 31 holds the axis Ax of the silica glass base material 1 by the guide pins 32 even when the silica glass base material 1 is tilted. Therefore, the silica glass base material 1 falls. Can be prevented. In addition, the weight member 33 continues to descend along the guide pins 32 of the fall prevention member 31 while being in contact with the upper portion of the silica glass base material 1, and continues to pressurize the silica glass base material 1.

  After the fall prevention member 31 is stopped by the stopper member 14, the guide pin 32 starts to come off from the silica glass base material 1, and the weight member 33 continues to be pressed while being in contact with the upper part of the silica glass base material 1. Thus, the silica glass base material 1 continues to be crushed, and the silica glass molded body 2 is formed by cooling after expanding the diameter to the set size.

  As described above, according to the silica glass thermoforming apparatus 30 and the thermoforming method of the third embodiment of the present invention, the weight member 33 sets the load for expanding the diameter of the silica glass base material 1. Thereby, the silica glass base material 1 can be crushed in a short time, and the silica glass molded object 2 can be shape | molded efficiently.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimension, numerical value, form, number, arrangement 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.

10, 20, 30 Heat forming apparatus 11 Carbon container 12 Vacuum heating furnace 13, 21, 31 Fall prevention member 14 Stopper member 33 Weight member

Claims (6)

A silica glass thermoforming apparatus comprising a carbon container in which columnar silica glass is stored, and a heating furnace in which the carbon container is installed, and expanding the diameter of the silica glass in the carbon container,
The bottom surface comes into contact with the top of the silica glass, the side surface slides with the inner surface of the carbon container, and the silica glass falls down while keeping the axis of the silica glass from shifting from the initial position during the diameter expansion process. A silica glass thermoforming apparatus, comprising a fall prevention member for preventing the above.   2. The silica glass thermoforming apparatus according to claim 1, further comprising a stopper member for preventing the falling prevention member from being lowered below a certain height.   The fall prevention member includes a side plate that is inscribed in the carbon container, a top plate that is in contact with the upper end surface of the silica glass and that is larger than the upper end surface of the silica glass, a peripheral portion of the top plate, and a lower end edge of the side plate The silica glass thermoforming apparatus according to claim 1, further comprising an inclined plate that connects the two to each other.   The fall-preventing member includes a top plate whose central portion contacts the upper end surface of the silica glass, a side plate extending downward from the periphery of the top plate and inscribed in the carbon container, and a lower surface of the central portion of the top plate 3. The silica glass thermoforming apparatus according to claim 1, further comprising: three or more guide pins that come into contact with a side surface of the upper end portion of the silica glass.   The fall prevention member includes a weight member that applies a load to the silica glass, and when the fall prevention member comes into contact with the stopper member and stops descending, the guide pin starts to come off from the silica glass, The silica glass thermoforming apparatus according to claim 4, wherein the weight member continues to be loaded. The bottom surface of the fall prevention member is brought into contact with the upper part of the columnar silica glass stored in the carbon vessel, and the side surface of the fall prevention member is slid with the inner surface of the carbon vessel, and the carbon vessel is installed in the heating furnace. The silica glass is subjected to diameter expansion processing so that the axis of the silica glass is not displaced from the initial position by the fall-preventing member and the silica glass is not tilted. Glass thermoforming method.

Images