JP4504823B2 - GLASS MANUFACTURING METHOD, GLASS MANUFACTURING DEVICE, AND PROTECTIVE MEMBER USED FOR THEM - Google Patents

Description

  The present invention provides a glass manufacturing method in which a glass material is continuously or intermittently supplied to a melting container, the material is melted in the melting container, and then continuously supplied to the next step, and such a method. More particularly, the present invention relates to an apparatus and method suitable for manufacturing optical glass in which the material is melted using a melting container made of a noble metal such as platinum or a noble metal alloy.

  Glass is produced mainly by using powdered glass component oxide (glass raw material batch) as a material and melting it at a high temperature. In particular, optical glass requires accurate and homogeneous optical characteristics, so that it is required to put the materials into a melting container in an appropriate amount after strictly mixing the materials.

  It is known to use a melting container made of platinum or a platinum alloy in the step of supplying the optical glass material to the melting container and heating it into the molten glass. These precious metal melting containers such as platinum are not only easy to process, but also contain relatively little erosion when containing molten optical glass, and are therefore suitable for melting optical glass.

  However, such a melting container is used under severe conditions of about 1000 to 1400 ° C., which is the melting temperature of the optical glass, and may be deformed or cracked by heat, so measures such as reinforcement are taken in advance. There is a need (see, for example, Patent Document 1).

  In patent document 1, in order to prevent the deformation | transformation of the welding part in a platinum container or a platinum pipe, the forge welding reinforcement by a platinum tape is performed. Further, the platinum tape has a corrugated end, and prevents cracks from occurring at the boundary of the forging position.

Japanese Patent Publication No. 64-6854

  In the melting container of Patent Document 1 described above, the welded portion is reinforced, but in the melting process of the optical glass, cracks and the like are also generated inside the melting container and in contact with the liquid surface of the molten glass. There is a problem of doing. As the first cause, the contact point between the liquid surface of the molten glass and the melting vessel is a coexistence point of the gas phase, the liquid phase, and the solid phase. This is because the melting vessel is easily eroded because the coexisting point of the gas phase, liquid phase, and solid phase is chemically active.

  In the production of optical glass, so-called continuous melting can be performed in order to increase production efficiency. In this case, the glass material to be melted is supplied to the melting container continuously or intermittently.

  When the glass material is continuously or intermittently supplied to the melting container, the temperature near the liquid surface of the molten glass already melted in the melting container is instantaneously lowered by supplying the glass material having a temperature lower than that. Usually, since there is a temperature difference exceeding 1000 ° C. between the glass material to be supplied and the molten glass in the melting container, the portion inside the melting container and in contact with the liquid surface of the molten glass is subjected to a large thermal shock. It will be. This is the second cause of the above problem.

  In order to alleviate the above thermal shock, it may be possible to preheat the glass material, but even in that case, the temperature difference between the glass material and the molten glass is around 1000 ° C. Is big.

  Therefore, in the melting container to which the glass material is continuously supplied, a large stress is caused near the liquid surface due to local volume shrinkage due to temperature drop. Furthermore, in the melting container in which the glass material is intermittently charged, the thermal shock is repeated in the glass material supply cycle, and a large stress is applied near the liquid surface of the melting container each time. As a result, the vicinity of the liquid surface of the melting vessel is not only gradually fatigued and the strength is impaired, but also a crack or the like may occur and be damaged.

  When even a part of the melting container is broken, the molten glass leaks out and it is difficult to continue the production, so that the melting container needs to be repaired or replaced. In order to repair or replace the melting container, in addition to a large amount of cost, it is forced to suspend production for a considerable period of time.

Furthermore, in the production of optical glass, a glass raw material batch (referred to as powder raw material before vitrification) is mainly used as a glass material, and this is intermittently or continuously supplied to a melting vessel to vitrify (directly). There is a (continuous melting) method (hereinafter referred to as a direct continuous melting method) in which the obtained molten glass is continuously supplied to the next step (for example, a clarification step, a homogenization step, a viscosity adjustment step, etc.). .
Direct melting is different from the method of melting a glass material (so-called cullet) once melted and vitrified into a desired optical glass by melting it again in a melting container (hereinafter referred to as indirect melting method). The chemical reaction starts near the liquid surface of the molten glass in the container at the moment when it is supplied to the container. Therefore, compared to the temperature drop of the liquid level that occurs when a low-temperature material is supplied, the temperature drop accompanying the heat of reaction (for example, the heat of vaporization of water accompanying the reaction) and the subsequent temperature recovery (temperature rise). ) Occurs.

  Further, when continuous melting is performed, the vitrified material is sequentially sent to the next process in order, and a series of processes such as clarification, homogenization, and viscosity adjustment are sequentially performed. That is, the time required for production in a time series is performed at two-dimensionally different positions, so that a substantial production time can be significantly shortened. However, in this case, it is necessary to balance the supply of the glass material in the melting container and the delivery to the next process. At this time, the liquid level of the molten glass in the melting container (the height of the liquid surface of the molten glass) is It is always substantially constant, that is, within a predetermined range. Therefore, the fixed part of the melting container always corresponds to the vicinity of the liquid surface, and the thermal shock due to the temperature drop and temperature rise is concentrated.

The direct continuous melting method is extremely advantageous as a mass production method even if a severe burden as described above is given to the melting vessel. That is, a series of steps of glass solidification and pulverization in the indirect melting method can be omitted completely.
In order to protect the glass melting container, the present inventors previously proposed a detachable protective member that alleviates the thermal shock during temperature rise and fall (Japanese Patent Application No. 2003-284303). However, although a certain effect was obtained in terms of protecting the melting container, the life of the protective member was not always sufficient. That is, the protective member is damaged by the erosion of the optical glass, and a part of the protective member is dropped into the melting container.

For example, optical glasses required for recent imaging devices and the like have a high refractive index (for example, nd is 1.7 to 2.0) and low refractive index and low dispersion (for example, nd is 1.6 or less, νd (Abbe number) is 60 or more). Among these, in order to obtain a high refractive index, an optical glass containing a large amount of a high refractive index component (such as Ti) has an extremely high erodibility to platinum. Further, the low refractive index and low dispersion optical glass also has high erosion due to the influence of fluorine or the like contained as a component.
In addition, in the case of containing boric acid as a main skeleton component (borate glass), if the direct continuous melting described above is performed, the heat of vaporization during the vitrification reaction is large, and the temperature recovery at the reaction site is slow. The effect on the container is large.
The present inventors have completed the present invention for the purpose of sufficiently obtaining the function of protecting the melting vessel even under the severe conditions as described above and extending the life of the protective member itself.

  The present invention has been considered in view of the above circumstances, and when supplying the glass material to the melting vessel, the thermal shock generated in the inner portion of the melting vessel and in the portion in contact with the liquid surface of the molten glass is mitigated. An object of the present invention is to provide a glass manufacturing apparatus and manufacturing method capable of preventing fatigue and breakage of a melting container due to thermal shock, and a protective member used for these. In particular, the object is to provide a method suitable for the production of optical glass of a type in which the melting temperature is high, the viscosity at the melting temperature is low, and the melting vessel is easily eroded in order to meet the required optical performance, and the apparatus. The purpose is to reduce the damage to the protective member and extend its life. Another object is to produce glass with extremely high productivity by a direct continuous method.

In order to achieve the above object, the method for producing glass in the present invention comprises a step of supplying a glass material continuously or intermittently to a melting container and continuously supplying the glass melted in the melting container to the next step. The melting container is made of a noble metal or a noble metal alloy, and the portion in contact with the molten glass liquid surface on the inner surface of the melting container and the material on the molten glass liquid surface are supplied. This is a method in which a protective member formed such that a portion in contact with the molten glass liquid surface is composed of a plurality of divided bodies is interposed between the two portions.

According to such a method, in the continuous production process of glass, when the glass material is supplied to a melting container made of a noble metal or a noble metal alloy , it contacts the inner surface of the melting container and the liquid surface of the molten glass. The thermal shock generated in the part can be alleviated, and fatigue and breakage of the melting container due to the thermal shock can be prevented. Thereby, not only can the lifetime of the melting container be extended, but also a decrease in productivity due to breakage of the melting container and repair costs of the melting container can be suppressed.
Moreover, the protective member is formed to have a plurality of divided parts in contact with the molten glass liquid surface, and when the thermal shock is alleviated, it is allowed to expand and contract instantaneously. Since the amount of expansion and contraction of the body can be reduced, the internal stress is further reduced and it is difficult to damage. Thereby, the lifetime of the protective member itself can be extended.

In the glass production method of the present invention, the material is preferably a glass raw material batch.
In this way, even when a glass raw material batch with a large temperature fluctuation of the molten glass liquid surface generated during material supply is used, the large thermal shock generated on the molten glass liquid surface is quickly alleviated and damage to the melting container and the protective member is suppressed. it can. For this reason, it can be set as the method advantageous for mass production using a glass raw material batch.

In the glass production method of the present invention, the glass is a borate optical glass, an optical glass having a refractive index nd of 1.7 or more, or an optical having a refractive index nd of 1.6 or less and a dispersion νd of 65 or more. It is preferably any of glass.
Thus, even when using an optical glass of a type that easily erodes the melting container, it is possible to quickly relieve the large thermal shock that occurs on the surface of the molten glass and to prevent damage to the melting container and the protective member, The effect of the present invention becomes remarkable when this type of optical glass that easily erodes the melting vessel is used.

Moreover, the glass manufacturing method in the present invention can be a method in which the protective member is detachably supported on the upper peripheral edge of the melting container, and the lower end of the protective member is a free end.
With such a method, even when the protective member is damaged or deteriorated despite its long life, it can be replaced as appropriate, and damage to the melting container can be reduced for a long period of time. In addition, if the lower end of the protective member is a free end, even if the protective member receives a thermal shock, shrinkage and expansion on the lower end side are allowed, so that the internal stress accompanying it is reduced, and the protective member is deformed or damaged. Can be prevented.

Moreover, the glass manufacturing method in the present invention can be a method in which the protection member is supported on the bottom of the melting container and the upper end of the protection member is a free end.
With such a method, even if the protective member is subjected to a thermal shock, shrinkage and expansion on the upper end side are allowed, so that the internal stress associated therewith can be reduced, and deformation and breakage of the protective member can be prevented. it can.

Further, the glass manufacturing apparatus in the present invention is a glass manufacturing apparatus including a melting container made of a noble metal or a noble metal alloy for melting a glass material, and a part in contact with a molten glass liquid surface on the inner surface of the melting container; A protective member is disposed so as to be interposed between the molten glass liquid surface and the portion to which the material is supplied, and the protective member is formed so that a portion in contact with the molten glass liquid surface is composed of a plurality of divided bodies. The configuration is as follows.
By adopting such a configuration, not only can the life of the melting container be extended, but also a reduction in productivity due to breakage of the melting container and the repair cost of the melting container can be suppressed, and the long life of the protective member itself It is also possible.

Further, in the glass manufacturing apparatus of the present invention, the horizontal cross-sectional shape of the melting container is a circle, and the protective member is the melting container so that the central axis of the protective member substantially coincides with the central axis of the melting container. It can be set as the structure arrange | positioned in.
If comprised in this way, the intensity | strength of a melting container can be made high and the buffering effect of the thermal shock by a protection member can be exhibited more effectively.

Moreover, the glass manufacturing apparatus in this invention can be set as the structure which has arrange | positioned the said protection member in the said melting container so that a clearance gap may arise between the inner surfaces of the said melting container.
If comprised in this way, the buffer effect of the thermal shock by a protection member can be exhibited more effectively.

The protective member in the present invention, a portion a protective member disposed melt vessel made of a noble metal or noble metal alloy to melt the material of glass, in contact with molten glass liquid surface in the inner surface of the melting vessel, It is arranged so as to be interposed between the molten glass liquid surface and the portion to which the material is supplied, and has a portion in contact with the molten glass liquid surface, and the portion is formed of a plurality of divided bodies. The configuration is as follows.
According to this structure, when the glass material is supplied to the molten glass in the melting container made of the noble metal or the noble metal alloy, the thermal shock generated by supplying the material to the molten glass liquid surface is reduced, In addition to preventing fatigue and breakage of the melting container due to impact, the life of the protective member itself can be extended.

Further, the protective member according to the present invention includes a support portion that is detachably supported on the upper peripheral edge of the melting container so that a gap is formed between the inner surface of the melting container when the protective member is disposed in the melting container. It can be set as the structure provided.
If comprised in this way, while the buffering effect of the thermal shock by a protective member can be exhibited more effectively, it will replace | exchange suitably, even when the protective member is damaged and deteriorated despite its long life. And damage to the melting container can be reduced for a long time.

As described above, according to the present invention, along a portion in contact with molten glass liquid surface in the inner surface of the melting vessel, by using a protective member disposed melt vessel, the materials of glass noble metal or noble metal alloy When the molten container is supplied, the thermal shock generated at the portion of the inner surface of the molten container that contacts the liquid surface of the molten glass can be alleviated, and fatigue or breakage of the molten container due to the thermal shock can be prevented. In addition, the protective member disposed in the melting container in order to mitigate thermal shock is less likely to be damaged by forming a part in contact with the molten glass liquid surface so as to be composed of a plurality of divided bodies. .
As a result, not only can the life of the melting container be extended, but the life of the protective member itself can be extended, resulting in a decrease in productivity due to breakage of the melting container, and further the repair cost of the melting container and the protective member. Can be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In addition, although the following embodiment demonstrates the apparatus and method which manufacture optical glass, this invention is applicable also to the apparatus and method in the case of manufacturing glass other than optical glass.

[Optical glass manufacturing equipment]
First, the optical glass manufacturing apparatus according to the present invention will be described. FIG. 1 is a front view showing an outline of an optical glass manufacturing apparatus, and FIG. 2 is a schematic perspective view of a protective member.

  As shown in these drawings, the optical glass manufacturing apparatus accommodates a material supply unit (material supply means) 10 for continuously or intermittently supplying optical glass material, and a material supplied from the material supply unit 10. And a melting tank (melting vessel) 20 for melting this, a clarification tank 40 connected to the melting tank 20 via a connecting pipe 30 and performing a defoaming treatment of the molten glass supplied from the melting tank 20, and the like. A work tank 60 connected to the clarification tank 40 through the pipe 50 and adjusting the viscosity of the molten glass supplied from the clarification tank 40 is provided.

The melting tank 20 is a container having an upper opening, and is made of, for example, a platinum-containing alloy such as platinum / rhodium or platinum / gold, or a noble metal such as platinum, rhodium, gold, iridium, or palladium.
Moreover, the melting tank 20 is provided with heating means such as high-frequency induction, and the optical glass material is melted by the heating. The heating means performs heating so as to keep the temperature of the molten glass substantially constant. However, when a low-temperature material is supplied to the melting tank 20, the temperature rapidly decreases near the liquid surface of the molten glass, and the liquid in the melting tank 20 is heated. The surface contact portion receives a large thermal shock. Moreover, the thermal shock by vitrification reaction also arises by supply of a glass raw material batch. In the present invention, the protective member 70 is used to solve this problem.

The protection member 70 is attached to the melting tank 20 so as to be disposed in the melting tank 20 along a portion of the inner surface of the melting tank 20 that contacts the molten glass liquid surface.
In disposing the protective member 70 in the melting tank 20, the protective member 70 includes, for example, a portion in contact with the molten glass liquid surface on the inner surface of the melting tank 20 and a glass material on the molten glass liquid surface inside the melting tank 20. It arrange | positions so that it may interpose between the site | parts supplied. That is, it is arranged so that the temperature drop / temperature increase of the molten glass liquid surface generated by the supply of the glass material is applied to the protective member 70 before the thermal shock is applied to the melting tank 20. It is attached.
In this embodiment, it can be provided with the cylinder part 71 which contact | connects the liquid level of molten glass, and the flange part 72 extended outward from the upper end of the cylinder part 71. FIG. In this case, the protective member 70 is detachably supported on the upper peripheral edge portion of the melting tank 20 with the flange portion 72 as a support portion so that replacement when the protective member 70 is damaged or deteriorated is facilitated. It can be attached to the melting tank 20.

  The protective member 70 attached to the melting tank 20 as described above absorbs the thermal shock caused by the rapid temperature drop of the molten glass generated when the optical glass material is put into the melting tank 20, and enters the melting tank 20. It works to alleviate the thermal shock. Further, by suppressing the thermal shock due to the temperature drop, the thermal shock (expansion) accompanying the temperature rise of the molten glass after the glass material is charged is also suppressed.

For example, when an optical glass material is intermittently charged into the melting tank 20, if there is no protective member 70, the thermal shock caused by temperature vibrations in the vicinity of the liquid level in the melting tank 20 every several hundred degrees C. to over 1000.degree. Will receive. At this time, as in this embodiment, when the vitrified glass melt is continuously supplied from the melting tank 20 to the clarification tank 40 or the work tank 60 where the next step is performed, glass melting, and Since subsequent processes (clarification, homogenization, viscosity adjustment, etc.) always proceed in parallel at different positions, the liquid level of the molten glass in the melting tank 20 is substantially constant. Therefore, the thermal shock described above is constantly generated at the substantially same level of the melting tank 20.
This temperature vibration becomes larger as the input amount is larger, and becomes prominent when a glass raw material batch is used as the glass material. Moreover, it is so large that the diameter of the melting tank 20 is small. When the protective member 70 is attached, the thermal shock due to temperature vibration can be suppressed to a fraction of a fraction.

As a more specific example, as shown in FIG. 6, if the protective member 70 is not attached to the melting tank 20, the temperature outside the melting tank 20 near the liquid surface of the molten glass immediately decreases due to the charging of the material. Then, the temperature oscillation of recovery is repeated periodically. When the protection member 70 is attached, as shown in FIG. 5, the temperature fluctuation range is suppressed to a fraction of a fraction.
5 and 6 show the temperature change on the outside of the melting tank 20 when the optical glass material is intermittently charged into the melting tank 20, the details will be described later.

  In order for the buffering effect to reduce the thermal shock to the melting tank 20 to be exhibited more effectively, the protective member 70 has a gap between the cylindrical portion 71 and the inner surface of the melting tank 20. In order to generate, it is preferable to attach so that it may oppose the inner surface of the melting tank 20 at predetermined intervals.

For this purpose, for example, as shown in FIG. 3, a protection piece is provided by providing a hanging piece 75 along the outer peripheral edge of the flange portion 72 and bringing the hanging piece 75 into contact with the outer surface of the melting tank 20. 70 may be positioned. The outer side of the melting tank 20 can be covered with the heat-resistant protective material 80. For example, the drooping piece 75 can be brought into contact with the outer surface of the heat-resistant protective material 80 as shown in the figure. The hanging piece 75 may be provided over the entire circumference of the flange portion 72. For example, two or more hanging pieces are provided at equal intervals along the outer peripheral edge of the flange portion 72. As many parts as necessary for positioning may be partially provided at appropriate positions.
These configurations have an effect of further reducing the thermal shock applied to the melting tank 20 by buffering the thermal shock received by the protective member 70 on the molten glass liquid surface by the molten glass in the gap. Furthermore, the contact area between the melting tank 20 and the protective member 70 can be reduced, the transmission of the thermal shock from the protective member 70 to the melting tank 20 is suppressed, the difference between the contraction amount and the expansion amount, the volume It is also effective to avoid applying stresses to each other due to the difference in direction of change.
In FIG. 3, each member is separated for drawing, but the melting tank 20, the flange portion 72, and the hanging piece 75 are in close contact with or in contact with the heat-resistant protective material 80. 20 is in contact with the peripheral edge of the upper end.

  When exhibiting a buffering effect to alleviate the thermal shock to the melting tank 20, the protective member 70 itself is also locally contracted near the liquid surface of the molten glass due to the temperature drop due to the temperature drop of the molten glass due to the material supply and the subsequent temperature rise. And the expansion will be repeated. For this reason, erosion of the protective member 70 due to long-term use is inevitable, but even if the erosion of the protective member 70 progresses, the molten glass will not flow out to the outside, so the influence on production is negligible. In addition, when the protective member 70 deteriorates due to erosion, the melting member 20 can be continuously protected from thermal shock over a long period of time by repairing or replacing the protective member 70, but the life of the protective member 70 is possible. It is desirable to make it as long as possible.

In the illustrated example, in order to minimize the stress acting on the protective member 70 due to local contraction and expansion, and to extend the life of the protective member 70, the portion in contact with the molten glass liquid surface of the protective member 70 is A plurality of divided bodies 73 are formed.
More specifically, when the protective member 70 is disposed in the melting tank 20, the cylindrical portion 71 of the protective member 70 is immersed in the molten glass at the lower end side. By providing a plurality of slits 74 that open to the lower end side of the cylindrical portion 71 in a range extending from the lower end of the portion 71 to the portion exposed on the liquid surface of the molten glass, the portion in contact with the molten glass liquid surface is divided into a plurality of portions. Yes.

At this time, each divided body 73 is integrally connected to the remaining portion of the cylindrical portion 71 on the upper end side, but both ends divided by the lower end and the slit are free ends, The shape allows horizontal contraction and expansion. Thereby, each divided body 73 of the protection member 70 is allowed to expand and contract instantaneously, and further, by dividing and reducing the volume, the amount of expansion and contraction of each individual divided body 73 can be reduced. Therefore, the internal stress acting on the protection member 70 is further reduced, and deformation and breakage of the protection member 70 are prevented.
Further, if the divided body 73 is formed by being divided by the plurality of slits 74, it is not necessary to combine a large number of divided bodies into a single body, the protection member 70 can be easily formed, and the protection member 70 can be used throughout the period of use. It is possible to sufficiently exhibit the above-described thermal shock buffering effect in a state where the integrity is maintained, and it is easy to perform work such as repair or replacement when the protective member 70 is damaged or deteriorated.

The slits 74 that divide the portion of the protective member 70 that contacts the molten glass liquid surface are preferably formed at substantially equal intervals over the entire circumference of the protective member 70.
At this time, the number of slits 74 is determined by the heat received by the protective member 70 in consideration of the melting temperature due to the composition of the glass to be melted, the size of the melting tank 20, the thickness of the melting tank 20, the frequency of material supply, and the like. It is determined appropriately according to the degree of impact.

When the number of the slits 74 is large, the number of the divided bodies 73 to be formed is also increased, and the responsiveness of contraction / expansion to the thermal shock is enhanced, and the contraction amount and the expansion amount can be dispersed, and the stress relaxation effect is enhanced. . However, when the number of the slits 74 is too large, the thermal shock shielding effect (the effect of shielding the thermal shock applied to the melting tank 20) by the protective member 70 is lowered, and the size of each divided body 73 is reduced. There is a tendency for physical strength to decrease.
For this reason, the number of slits 74 is preferably in the range of 4 to 50, and the slit width s is preferably in the range of 1 to 10 mm. The horizontal width of each divided body 73 is preferably selected in the range of 20 to 1000 mm. If the size of the divided body 73 is too large, the stress relaxation effect is lowered, and if it is too small, the physical strength is lowered. .

  In the illustrated example, the slit 74 is formed so that the lower end side of the cylindrical portion 71 is a starting point and the end point is located at a portion exposed on the liquid surface of the molten glass of the cylindrical portion 71. The length from the end point to the end point can be appropriately set in consideration of the fluctuation of the liquid level of the molten glass. As will be described later, in the continuous melting furnace, it is possible to prevent the liquid level of the molten glass from greatly fluctuating, but there may still be some fluctuation. For this reason, it is preferable to set the immersion depth of the slit 74 so that the divided body 73 formed by the slit 74 is always in contact with the molten glass liquid surface.

Furthermore, when the vertical length of the slit 74 is a predetermined length L, a portion of L / 2 or higher is always exposed above the molten glass liquid surface, and a portion of less than L / 2 is below the liquid surface. It is preferable to be immersed.
This is very effective in the following points. That is, the protective member 70 receives a thermal shock in the vicinity of the molten glass liquid surface, but this influence does not occur equally on the liquid surface and below the liquid surface, but is greatly affected by the portion above the liquid surface. The local temperature oscillation generated in the vicinity of the molten glass liquid surface of the protective member 70 has a predetermined temperature due to contact with the glass melt having a large heat capacity (and therefore always within the predetermined temperature range) in the portion below the liquid surface. Although the fluctuation from the range is slight, there is no buffer action by the glass melt above the liquid level, so the strain due to thermal expansion due to the temperature rise reaches the part at a predetermined distance above the liquid level. . Thus, the breakage of the protective member to be solved by the present invention (or the breakage of the melting container itself) tends to occur in a predetermined range portion above the molten glass liquid surface.
Therefore, it is preferable that the slit 74 is provided over the portion where the strain reaches above the molten glass liquid surface. In other words, when a protective member with slits of a predetermined size is used, it is most efficient to position most of the slits 74 above the molten glass liquid surface, and more preferably, the liquid level of the molten glass in the slits 74. The dimensional ratio (a / b) between the upper part (a) and the lower part (b) is 7/3 or more. In this way, the slit 74 acts more efficiently.

  In consideration of the above, for example, the reference liquid level that is the target to keep the liquid level constant by appropriately adjusting the supply amount of the glass material, the supply amount of the molten glass to the next process, and the timing thereof, etc. In this case, the end point of the slit 74 is preferably located in the range of 30 to 100 mm from the reference surface, and the start point of the slit 74 is located in the range of 5 to 40 mm from the reference surface. Is preferred.

In the above example, the protective member 70 is attached to the peripheral edge of the upper end of the melting tank 20 by the flange portion 72, but the specific mode of attaching the protective member 70 to the melting tank 20 is not particularly limited. For example, as shown in FIG. 4 , it can be supported at the bottom of the melting tank 20.

More specifically, the protective member 70 includes a main body 76 that contacts the liquid surface of the molten glass along the portion of the inner surface of the melting tank 20 where the upper side contacts the liquid surface of the molten glass on the inner surface of the melting tank 20, and the main body A plurality of foot portions 77 formed on the lower side of the portion 76 can be provided. In this case, the protective member 70 can be attached to the melting tank 20 while being placed on the bottom surface of the melting tank 20 by the plurality of legs 77.
4 (a) is an explanatory view conceptually showing a state of attaching the protective member 70 to the molten bath 20, Fig. 4 (b) is a schematic perspective view of a protective member 70. Further, the perforation indicated by reference numeral 78 in the figure is for allowing the molten glass to flow out of the protective member 70, and the formation position and number thereof are appropriately set according to the shape, size, etc. of the protective member 70. The

When the protective member 70 is attached to the melting container 20 in such a manner, it is preferable that at least the bottom of the main body 76 of the protective member 70 is formed in a substantially spherical shape. As a result, physical strength can be obtained. In particular, when a glass material is charged in the form of cullet, the cullet that sinks in the molten glass may contact the bottom surface of the protective member 70 without being completely melted. The damage of the protective member due to the contact at this time hardly occurs.
Further, in order to more effectively exert a buffering effect to alleviate the thermal shock to the melting tank 20, the protective member 70 includes the main body 76 and the inner surface of the melting tank 20, as in the above example. It is preferable that the shape and size are appropriately set so that a gap is formed between them, and they are attached so as to face the inner surface of the melting tank 20 at a predetermined interval.

The protective member 70 shown in FIG. 4 is immersed under the liquid surface of the molten glass except for a part on the upper side of the main body portion 76, but from the upper end of the main body portion 76 in a state of being disposed in the melting tank 20. By providing a plurality of slits 74 opened on the upper end side of the main body portion 76 in the range over the portion immersed under the liquid surface of the molten glass, the molten glass liquid surface of the protective member 70 is provided. The contacting portion can be formed to be composed of a plurality of divided bodies 73. At this time, each divided body 73 is integrally connected to the remaining portion of the main body portion 76 on the lower end side, but the upper end and both side ends divided by the slit 74 are free ends, as in the above example. In addition, vertical contraction and expansion due to temperature vibration are allowed.

  When the protection member 70 is configured in such a manner, the end point of the slit 74 is located in a portion immersed under the liquid surface of the molten glass of the main body portion 76. Similarly, when the length difference in the vertical direction of the slit 74 is set to a predetermined length L, it is preferable that L / 2 or more is always exposed above the liquid surface of the molten glass. The dimension ratio (a / b) between the part (a) above the liquid level and the part (b) below the liquid level is 7/3 or more. If it does in this way, the protection member 70 exposed on the liquid level can buffer the thermal fluctuation of a molten glass liquid surface more effectively, and the slit 74 acts most efficiently in that case.

  In any case, the horizontal cross-sectional shape of the melting tank 20 is circular, and the horizontal cross-sectional shape of the protection member 70 is provided with a rotationally symmetrical central axis such as a circular shape or a polygonal shape. It is preferable that the protective member 70 is disposed in the melting container so as to have a shape such that the central axis of the melting tank 20 and the central axis of the protective member 70 substantially coincide with each other. Thereby, the intensity | strength of the melting tank 20 can be made high and the buffering effect of the thermal shock by a protection member can be exhibited more effectively.

The protective member 70 may be formed by molding one member into a predetermined shape, but may be formed by combining a plurality of members in the circumferential direction. In any case, it is preferable to provide the free end 79 in the circumferential direction. In the former case, for example, as shown in FIG. 2, the band-shaped member can be formed into a cylindrical shape so that both ends overlap, and the end portion can be formed as a free end 79. In the latter case, the edges of the plurality of members can be overlapped in the same manner and combined in the circumferential direction so that the edges become free ends 79.
If the protective member 70 is configured in this way, the circumferential contraction and expansion of the protective member 70 are allowed, and the internal stress associated with the thermal shock can be further reduced.

  In addition to platinum, platinum-containing alloys such as platinum / rhodium and platinum / gold, and noble metals such as rhodium, gold, iridium, and palladium can be used as the material of the protective member 70. In the melting step, when the eroded melting tank component or the protective member component is mixed into the molten glass, the molten glass may be colored. Therefore, it is preferable to select a material with low erosion such as platinum or a platinum alloy. However, in the case of a glass component that increases in color when platinum is used, other materials are appropriately selected. Moreover, it is preferable that the raw material of the protection member 70 contains a common component with the raw material of the melting tank 20. In this way, even if the component of the protective member 70 is mixed into the molten glass due to erosion, since the component is the same as the component of the melting tank 20, the influence on the optical glass to be manufactured can be reduced. .

  The melting tank 20 to which the present invention is applied is preferably used in a continuous melting furnace that performs continuous melting. In this case, the glass melted in the melting tank 20 continuously moves to the next step. The next step can be a clarification tank 40, for example. In the clarification tank 40, defoaming and homogenization of the molten glass are performed. Furthermore, the post-process of the clarification tank 40 can be a work tank 60. In the work tank 60, the molten glass is adjusted to a viscosity suitable for molding. Needless to say, in addition to the melting tank 20, the clarification tank 40, and the work tank 60, other processes may be added as an intermediate process or a post-process. For example, an agitation tank may be provided as an intermediate step to further increase the homogeneity of the glass.

  In such a continuous melting furnace, unlike the case of pot melting, the liquid level of the molten glass does not vary greatly. That is, the glass material is supplied simultaneously with the outflow of the molten glass, and the glass liquid level is maintained at a substantially constant position. Therefore, since the vicinity of the liquid surface of the melting tank 20 is intensively subjected to thermal shock, the effect is remarkable when the present invention is applied.

  There is no restriction | limiting in particular in the composition of the optical glass applied to this invention. For example, it is suitably used for phosphate glass, borate glass, silicate glass, borosilicate glass, fluorophosphate glass, and the like. In particular, it can be applied to a glass containing an alkali component and having a strong erosion action, and the effect is remarkable in a low-viscosity glass having a viscosity at the time of melting of 30 poise or less.

The apparatus and method of the present invention are particularly effective when used in the step of mixing and reacting glass raw materials to vitrify, but remelting a so-called cullet obtained by pulverizing the material once vitrified, It can also be used to produce an optical glass having the following detailed physical properties. In particular, when the former is used, the effect of the present invention is remarkable when platinum or a platinum alloy is used as the melting container and borate glass is used as the glass seed. Borate glass has a large generation of heat of vaporization during the vitrification process, and the temperature fluctuation of the molten glass liquid surface is severe. Therefore, the effect of the present invention is great, and the apparatus of the present invention provides a high transmittance optical glass. Is obtained. Moreover, a favorable effect is acquired also by applying the optical glass which does not contain lead to the apparatus of this invention which consists of platinum or a platinum alloy. Furthermore, high-quality optical glass can be obtained by using the apparatus of the present invention for fluorophosphate glass, which is difficult to control precise optical properties. In particular, it can be suitably applied to optical glass containing a large amount of a high refractive index component and having a refractive index nd of 1.7 or more, and a fluorophosphate glass having a refractive index nd of 1.6 or less and a dispersion νd of 65 or more.

[Optical glass manufacturing method]
Below, the manufacturing method of the optical glass which concerns on this invention is demonstrated.
The optical glass manufacturing method according to the present invention can be applied to a step of supplying a material of optical glass continuously or intermittently to a melting container and melting the material in the melting container. Specifically, the protective member 70 formed so that the portion in contact with the molten glass liquid surface is composed of a plurality of divided bodies 73 along the portion in contact with the molten glass liquid surface on the inner surface of the melting tank 20 is provided. The material is supplied to the molten glass liquid surface disposed inside and surrounded by the protective member 70 and melted.

  If such an optical glass manufacturing method is used, when the material of the optical glass is supplied to the melting bath 20, the thermal shock generated at the portion of the inner surface of the melting bath 20 that comes into contact with the liquid surface of the molten glass is alleviated. It is possible to prevent fatigue and breakage of the melting tank 20 due to the above, and it is also possible to make the protection member 70 itself difficult to be damaged. Thereby, not only can the life of the melting tank 20 be extended, but the life of the protective member 70 itself can be lengthened, the productivity is lowered due to breakage of the melting tank 20, and further, the melting tank 20 and the protective member The repair cost of 70 can be suppressed.

  Moreover, in the manufacturing method of the optical glass in this invention, the protection member 70 is comprised so that replacement | exchange is possible according to the deterioration, The protection effect of the melting tank 20 by the protection member 70 is maintained over a long period of time, and the lifetime of the melting tank 20 Can be further extended.

  In the optical glass manufacturing apparatus shown in FIG. 1, when the protective member 70 is attached to the melting tank 20 and the optical glass material is melted, and when the optical glass material is melted without attaching the protective member 70 to the melting tank 20 And compared. A material was intermittently charged from the material supply unit 10 into the melting tank 20, and the temperature change in the outer part facing the liquid glass surface of the melting tank 20 was observed.

In the melting tank 20 to which the protective member 70 is not attached, as shown in FIG. 6, when the material was put into the melting tank 20, the temperature of the side surface portion of the melting tank 20 immediately decreased, and then the temperature recovered. Inside the melting tank 20, a larger temperature fluctuation occurs.
Here, cullet (glass material solidified and crushed after vitrification) was used as the glass material. However, when a glass raw material batch is used, a melting tank of the same size and the same amount of glass material should be supplied. In this case, the temperature fluctuation is further increased and the damage to the melting tank is increased. In order to suppress this increase in temperature fluctuation, it is necessary to take a disadvantageous measure in terms of production efficiency, such as increasing the size of the molten layer or decreasing the supply amount.

On the other hand, the attached protective member 70 melting tank 20, as shown in FIG. 5, when turning on the material, but the temperature in the vicinity of the liquid surface in the melting bath 20 was lowered, the temperature difference is, the case of FIG. 6 Comparison Then, it is suppressed to less than one-sixth. This is because the protective member 70 covering the vicinity of the liquid surface of the melting tank 20 has absorbed the thermal shock.

  The present invention can be applied to a glass manufacturing apparatus and a manufacturing method in which a glass material is continuously or intermittently supplied to a melting container and the material is melted in the melting container. In particular, it is useful as an optical glass manufacturing apparatus or manufacturing method for melting the material using a melting container made of a noble metal such as platinum or a noble metal alloy.

It is a schematic front view which shows the manufacturing apparatus of optical glass. It is a schematic perspective view which shows an example of a protection member. It is explanatory drawing which shows notionally the state which attached an example of the protection member to the melting container. It is a figure which shows the other example of a protection member. It is explanatory drawing which shows the temperature change of the melting tank (liquid level vicinity) in an Example. It is explanatory drawing which shows the temperature change of the melting tank (liquid level vicinity) in a comparative example.

Explanation of symbols

10 Material supply unit 20 Melting tank (melting vessel)
70 Protective member 71 Tube portion 72 Flange portion 73 Divided body 74 Slit 75 Drooping piece 76 Body portion 77 Foot portion

Claims (9)

A method for producing glass comprising a step of supplying a glass material continuously or intermittently to a melting container, and continuously supplying glass melted in the melting container to the next step,
The molten container is made of a noble metal or a noble metal alloy, and the molten glass liquid is disposed between a portion in contact with the molten glass liquid surface on the inner surface of the molten container and a portion to which the material is supplied on the molten glass liquid surface. A method for producing glass, comprising a protective member formed such that a portion in contact with a surface is composed of a plurality of divided bodies.   The said material is a glass raw material batch, The manufacturing method of the glass of Claim 1 characterized by the above-mentioned.   The glass is any one of borate optical glass, optical glass having a refractive index nd of 1.7 or more, or optical glass having a refractive index nd of 1.6 or less and a dispersion νd of 65 or more. The manufacturing method of the glass of any one of Claims 1-2.   4. The glass according to claim 1, wherein the protective member is detachably supported on the upper peripheral edge of the melting container, and the lower end of the protective member is a free end. Production method.   The method for producing glass according to any one of claims 1 to 3, wherein the protective member is supported on the bottom of the melting container, and the upper end of the protective member is a free end. A glass manufacturing apparatus including a melting container made of a noble metal or a noble metal alloy for melting a glass material,
A protective member is disposed so as to be interposed between a portion in contact with the molten glass liquid surface on the inner surface of the melting container and a portion to which the material is supplied on the molten glass liquid surface,
The glass manufacturing apparatus, wherein the protective member is formed so that a portion in contact with the molten glass liquid surface is composed of a plurality of divided bodies.   The horizontal cross-sectional shape of the melting container is circular, and the protective member is disposed in the melting container so that the central axis of the protective member substantially coincides with the central axis of the melting container. The glass manufacturing apparatus according to claim 6.   The glass manufacturing apparatus according to claim 6, wherein the protective member is disposed in the melting container so that a gap is formed between the inner surface of the melting container. A protective member disposed in a melting vessel made of a noble metal or a noble metal alloy for melting a glass material,
It is arranged so as to be interposed between a portion of the inner surface of the molten container that is in contact with the molten glass liquid surface and a portion of the molten glass liquid surface to which the material is supplied,
A protective member having a portion in contact with the molten glass liquid surface, wherein the portion is formed of a plurality of divided bodies.

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