JP2009096684A - Flow passage for flowing-out molten glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flow passage for feeding molten glass which does not cause wetting-up even in molten glass having low viscosity, thus can mold a preform having no degenerated parts caused by wetting-up and having no presence of striae. <P>SOLUTION: A flow passage is provided which is connected to a molten glass tank and flows out molten glass. The distal end part is branched into an inside tube and an outside tube arranged on the outside thereof at prescribed intervals, the inside diameter of the inside tube is ≥50% of the inside diameter of the outside tube, and the lower side edge of the inside tube is projected more downward than the lower side edge of the outside tube. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a flow path that is connected to a molten glass tank and allows molten glass to flow out in order to produce a glass molded body by flowing molten glass into a mold, and particularly uses the surface tension of the molten glass and its own weight. The present invention relates to a flow path suitable for preform molding in which a glass gob is dropped from a nozzle and molded into a precision press molding preform by a preform molding die.

  In general, there are a spherical lens and an aspheric lens as lenses constituting the optical system. Many spherical lenses are manufactured by grinding and polishing a glass molded product obtained by reheat press molding a glass material. On the other hand, an aspherical lens is a method in which a heat-softened preform material is press-molded with a mold having a high-precision molding surface, and the shape of the mold with a high-precision molding surface is transferred to the preform material. Manufacturing by press molding has become the mainstream.

  As a precision press-molding preform, a spherical, elliptical or flat glass molded body (glass gob) is often used. These materials are melted in a melting apparatus such as a crucible and then put into a melting apparatus. It can be manufactured by allowing it to flow out from a connected nozzle or the like onto a mold, forming it into plate-like glass or rod-like glass, and further cold-working them. In recent years, the molten glass flowing out from the nozzle is cut with a shear, or separated by utilizing surface tension and its own weight, and, for example, dropped onto a porous mold capable of ejecting gas, and is appropriately floated. A technique for forming a glass gob of size and shape is used. When a glass stream is cut with a shear, the cutting trace may remain on the glass gob. In recent years, a method of dropping the glass gob using surface tension and its own weight is often used.

  In recent years, as the refractive index of optical glass increases, the liquidus temperature tends to increase or the molten glass tends to decrease in viscosity. One of the problems that occur with such a tendency of glass physical properties is the problem of wetting from the nozzle opening of molten glass. That is, molten glass accumulates up to a predetermined amount at the nozzle outlet, and in the process of dropping from the glass flow due to surface tension and its own weight, a part of the molten glass may get wet and stay at the outer lower end of the nozzle. When such a stay occurs, it becomes easy to cause alteration in the staying part, and when this falls onto the preform mold together with the molten glass flow flowing out from the nozzle, the striae occurs when it is molded into the preform. There is. Various countermeasures have been proposed for the problem of wetting up, but there is not yet anything that can provide a sufficient effect with a simple device.

Patent Document 1 discloses an apparatus for supplying molten glass from a first glass melting tank to a second glass melting tank as an apparatus for obtaining glass with high homogeneity. As a nozzle of the glass supply device described in this document, a nozzle in which a tubular member is disposed as a molten glass guide member inside an outer tube is disclosed. However, in this nozzle, a relatively small amount of molten glass flows down through the guide member, and most of the molten glass flows down through the gap between the outer tube and the guide member. The glass flow flowing down the gap between the members is hardly affected by the guide member. Therefore, when this nozzle is applied as a glass gob dropping nozzle, it is impossible to prevent the low-viscosity molten glass from getting wet from the mouth of the outer tube to the outer lower end of the outer tube.
JP 2006-199554 A

  The present invention has been made in view of the problems in molding a glass gob from the above low-viscosity molten glass, and does not cause wetting even in low-viscosity molten glass that tends to cause wetting. An object of the present invention is to provide a flow path for supplying molten glass that can form a preform having no alteration due to ascent and having no striae.

  A first configuration of the present invention that solves the above-described problems is a flow path that is connected to a molten glass tank and allows molten glass to flow out, and a tip portion thereof is spaced apart from the inner tube by a predetermined distance. The inner tube has an inner diameter of 50% or more of the inner diameter of the outer tube, and the lower edge of the inner tube protrudes below the lower edge of the outer tube. It is characterized by that.

  In the second configuration of the flow channel of the present invention, in addition to the first configuration, the wettability of the molten glass with respect to the outer tube outer wall is better than the wettability of the molten glass with respect to the outer tube outer wall in the vicinity of the outlet. It is characterized by that.

  In the third configuration of the flow path of the present invention, in addition to the second configuration, the inner tube is made of a platinum group alloy or a reinforced platinum group alloy thereof, and the outer tube is a platinum group alloy containing gold, or reinforced. It consists of a platinum group alloy or gold or reinforced gold.

  The fourth configuration of the flow path of the present invention is characterized in that, in addition to the second or third configuration, the surface roughness of the outer wall of the inner tube is rougher than the surface roughness of the outer wall of the outer tube.

  In the fifth configuration of the flow path of the present invention, in addition to any of the first to fourth configurations, the length in the outflow direction of the protruding portion of the inner tube is a flow formed between the inner tube and the outer tube. It is 1 to 10 times the road width.

  In addition to any of the first to fifth configurations, the sixth configuration of the flow channel of the present invention is such that the flow path cross-sectional center of gravity perpendicular to the molten glass outflow direction is It has the site | part which has shifted | deviated.

  According to a seventh configuration of the flow path of the present invention, in addition to the sixth configuration, a baffle plate is provided inside the flow path.

  In the eighth configuration of the flow path of the present invention, in addition to the seventh configuration, the thickness of the baffle plate is such that the flow path cross-sectional center perpendicular to the molten glass outflow direction is shifted from the upstream flow path cross-section center. It is characterized by being 0.1 to 10 times the flow path diameter of the part.

  The ninth structure of the flow channel of the present invention is characterized in that, in addition to any of the first to eighth configurations, the flow channel outer wall has a portion that expands in the flowing direction of the molten glass.

  According to a tenth configuration of the flow path of the present invention, a glass raw material is melted in a molten glass tank, and the molten glass is formed into a mold through the flow path according to claim 1 connected to the molten glass tank. It is the manufacturing method of the glass forming body including making it flow out and shape | molding a glass forming body.

  The eleventh configuration of the present invention is a glass including melting a glass raw material in a molten glass tank, and flowing the molten glass into a mold through a flow path connected to the molten glass tank to form a glass molded body. In the manufacturing method of a molded object, this flow path is the flow path in any one of the structures 1-10, It is a manufacturing method of the glass molded object characterized by the above-mentioned.

  According to the said structure, an optical glass preform without a striae can be shape | molded by acquiring a glass lump from low-viscosity molten glass and carrying out float forming.

Hereinafter, embodiments of the present invention will be described.
In this specification, the “flow path” includes an entire flow path through which the glass flow passes and an outlet, which are connected to a molten glass tank that melts and / or holds molten glass and flows the molten glass into a mold. It is a concept, and pipes and orifices are included in the “flow path”.

  In the first configuration of the present invention, the flow path has its distal end portion, that is, the vicinity of the outlet, branched into an inner tube and an outer tube disposed at a predetermined interval on the outer side, and the inner diameter of the inner tube is It is 50% or more of the inner diameter of the outer tube, and the lower edge of the inner tube protrudes below the lower edge of the outer tube. Therefore, the glass flow at the outer lower end of the inner tube also flows in the molten glass flowing down from the outer tube along the outer wall of the inner tube, so that the amount of glass wetted on the outer wall portion of the outer tube can be drastically reduced. As a result, it becomes difficult to cause a problem that the glass is wet and changes in quality, and as a result, molding capable of reducing the striae of the preform becomes possible.

  Of course, a part of the molten glass flowing out from the outer tube along the outer wall of the inner tube also tries to wet up from the tube opening of the outer tube to the outer lower end of the outer tube, but this portion of the glass is not covered by the inner tube. Since the glass is pulled by the molten glass flow flowing down along the outer wall and the pulling force of the flowing glass resists the force of wetting, the glass in this portion is also difficult to wet from the mouth of the outer tube. As described above, in the flow channel of the present invention, wetting can be prevented by the action between the two glass flows of the inner tube and the outer tube, and a glass gob having a uniform and no striae can be supplied.

  It has now been empirically found that this is very effective if the ratio of the inner tube inner diameter to the outer tube inner diameter is within a predetermined range. If the diameter of the inner tube is too small, the pulling effect from the molten glass flowing between the inner tubes (against the glass flowing between the inner tube and the outer tube) will decrease, and the effect of preventing wetting on the outer wall of the outer tube will be prevented. Decline. On the other hand, if the diameter of the inner tube is too large, the thickness of the molten glass flowing down along the outer wall becomes thin, so that it is easy to be cooled, and thus devitrification may occur in the molten glass flowing out from the outer tube side.

  Accordingly, the inner diameter of the inner tube is preferably 50% or more of the inner diameter of the outer tube, more preferably 55% or more, and most preferably 60% or more. Further, it is preferably 97% or less, more preferably 95% or less, and most preferably 93% or less.

  In the second configuration of the present invention, the wettability of the molten glass with respect to the outer wall of the inner tube is better than the wettability of the outer surface of the molten glass with respect to the outer wall near the outlet of the flow path. It can be further promoted. Thus, by making the wettability of the outer tube smaller than that of the inner tube, the glass that is going to get wet to the outer wall of the outer tube is easily drawn when pulled by the glass flow flowing inside.

  In the third configuration of the present invention, the inner tube is a platinum-based metal that has relatively good wettability with molten glass, and the outer tube is gold or a gold-containing alloy that has poor wettability with molten glass. While the glass flow flowing down along the inner and outer walls of the tube flows easily, the glass flow flowing down from the outer tube improves the wet-up preventing effect.

  The platinum group, platinum group alloy or their reinforcements used for the inner tube is preferably a known platinum group alloy or the like used as a glass melting member, specifically platinum and palladium, iridium, osmium, Rhenium can be used. Further, it does not prevent the gold from being contained in a certain amount, but it is preferable that the wettability with respect to the molten glass between the outer sides is improved. Further, as the reinforcement such as platinum group metal, a platinum group alloy containing a predetermined amount of a known reinforcing material such as zirconium oxide (dispersed) is used.

  The platinum group alloy containing gold used in the outer tube, or the reinforced platinum group alloy or gold or reinforced gold is preferably a known gold-containing platinum group alloy used as a glass melting member, and more preferably platinum. Gold or reinforced gold may be used without using a group alloy. Here, a reinforcing material containing (dispersing) a predetermined amount of a known reinforcing material such as zirconium oxide can be used.

  In the 4th structure of this invention, since the surface roughness of the outer wall of an inner side pipe is rougher than the surface roughness of the outer wall of an outer side pipe | tube, the said wet-up prevention effect can be promoted further.

  In the fifth configuration of the present invention, the length in the outflow direction of the protruding portion between the inner sides is set to a predetermined ratio in relation to the flow path width formed between the inner tube and the outer tube. An optimal flow path structure can be obtained by exhibiting the effect of preventing wetting. According to the results of intensive studies by the inventor, it is preferable that the length in the outflow direction of the protruding portion between the inner sides is 1 to 10 times the width of the flow path formed between the inner tube and the outer tube. It is more preferable to set it to -9 times, and it is most preferable to set it as 3-8 times. Here, the “length in the outflow direction of the protruding portion” between the inner sides means the distance in the outflow direction between the outer tube end portion and the inner tube end portion, that is, the distance d in FIG. 2 representing the embodiment of the present invention. .

  In the sixth and seventh configurations of the present invention, by providing a portion where the cross-sectional center of gravity of the flow path is shifted in the upstream portion of the nozzle, for example, a baffle plate, disadvantages such as striae of the glass lump to be formed are significantly reduced. be able to.

When the molten glass flowing out of the molten glass tank passes through the flow path, the temperature at the center of the cross section of the flow path is relatively much higher than in the vicinity of the inner wall. Non-uniformity in temperature, viscosity, and flow rate will increase during the glass flow, which is likely to cause pulse and devitrification. Accordingly, by providing a baffle plate in the middle of the flow path, for example, by providing a baffle plate in the middle of the flow path, the relatively high temperature glass flow that flows near the center of the cross section perpendicular to the traveling direction of the molten glass flow suddenly. The path is bent and mixed with a relatively cool glass stream near the inner wall of the inner tube, resulting in a relatively uniform temperature distribution. As a result, disadvantages such as devitrification and striae can be eliminated. A desired temperature and flow velocity distribution can be obtained by constructing an outflow portion having an appropriate diameter, length, shape, and temperature control method beyond this portion, thereby allowing striae and devitrification in the glass molded body. Can be further suppressed.
The means for shifting the cross-sectional center of gravity of the flow path in the upstream portion of the nozzle is not limited to the baffle plate.

  In the eighth configuration of the present invention, the problem such as striae can be further reduced by forming the baffle plate in a predetermined shape. If the thickness of the baffle plate is too thick, the flow of the glass flow tends to stagnate, and on the contrary, it tends to cause devitrification and striae, and if it is too thin, it cannot withstand the heat and pressure of the glass flow and breaks or deforms. It becomes easy to do. Therefore, it is preferable that the thickness of the baffle plate is 0.1 to 10 times the flow path diameter of the portion where the cross-sectional center of gravity perpendicular to the molten glass outflow direction is shifted from the upstream cross-sectional center of gravity. It is more preferably 2 to 9 times, and most preferably 0.3 to 8 times.

  In the ninth configuration of the present invention, by expanding the flow path outer wall in the flowing direction of the molten glass, it is possible to perform molding in accordance with the size, shape, glass viscosity, and the like of the acquired glass lump.

  According to the tenth configuration of the present invention, the flow path is used in a press molding preform manufacturing apparatus that molds the molten glass supplied onto the molding die into a press molding preform, thereby providing a homogeneous and striae. It is possible to mold a press-molding preform without any.

Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic view showing the entire glass molded body manufacturing apparatus using the flow path of the present invention.
The glass molded body manufacturing apparatus 1 includes a melting device 2 including a molten glass tank 3, a flow path 4 connected to the molten glass tank 3, and a preform forming apparatus 5 in which molten glass supplied from the flow path 4 is formed into a preform. Is provided. Usually, the glass raw material is put into a molten glass tank 3 composed of a crucible or the like of the melting apparatus 2, heated, and melted at a predetermined temperature. The flow path 4 for supplying the molten glass to the preform molding apparatus 5 is usually made of a heat-resistant metal, and in many cases, the above-described platinum alloy, reinforced platinum alloy or the like is used. The molten glass passes through the flow path 4 or after being appropriately subjected to clarification, defoaming, stirring, and the like, and then flows down from the front end of the flow path 4 to the mold of the preform molding device 5. The mold can take various forms depending on the preform to be created. For example, when making a sheet glass, it flows down as a continuous flow on a substantially rectangular mold. When performing floating molding, it is common to use a porous mold having a circular depression or a trumpet-shaped mold having a gas outlet at the bottom.

FIG. 2 is a longitudinal sectional view showing an embodiment of the tip portion of the flow path of the present invention.
The flow path 2 is formed in a widened portion 6 whose tip portion widens in a tapered shape toward the downstream side, and the tip portion has a large diameter of molten glass whose inner diameter is 50% or more of the inner diameter of the outer tube. The inner pipe 7 is branched into a cylindrical inner pipe 7 that allows the portion to flow out, and a cylindrical outer pipe 8 that is arranged at a predetermined interval on the outer side thereof, and the lower end edge of the inner pipe 7 is the lower end edge of the outer pipe 8. It protrudes downward by a predetermined dimension. The inner tube 7 is integrally formed with support portions 7a extending in the radial direction at a plurality of locations at the upper end portion thereof, and the tip portions of the support portions 7a are fixed to the outer periphery of the outer tube 8 by welding. The length in the outflow direction of the protruding portion of the inner tube 7 is preferably 1 to 10 times the width of the flow path formed between the inner tube and the outer tube.

The inner tube 7 is made of platinum, platinum group alloy, reinforced platinum or reinforced platinum alloy having good wettability with respect to the glass flow, and the outer tube is made of platinum, platinum group alloy containing gold with poor wettability with respect to the glass flow, It is preferably made of reinforced platinum, reinforced platinum alloy, gold or reinforced gold. With this configuration, the glass flow flowing down along the inner and outer walls of the inner tube 7 easily flows, while the effect of preventing wetting is improved with respect to the glass flow flowing down from the outer tube 8.
FIG. 3 is a cross-sectional view showing an embodiment in which a baffle plate 10 is provided in a part of a flow path before branching into a double pipe.

  The flow path is discontinuously narrow at the site where the baffle plate 10 is located, and the flow path center of the site is shifted from the flow path center to the upstream portion.

  By adopting such a baffle plate 10, the high-temperature glass flow that has flowed near the center in the upstream portion of the flow path must be changed to the vicinity of the inner wall of the flow path by the baffle plate 10. It mixes with the low-temperature glass flow that has flowed near the inner wall of the flow path, and the temperature is made uniform. As a result, since temperature can be measured and controlled with higher accuracy when passing through the baffle plate 10, the outflow or inappropriate temperature of the high-temperature glass flow that causes striae in the glass gob that flows down Is less likely to occur. In FIG. 3, the glass flow passes through a narrow flow path formed by the baffle plate 10, but is formed by a single baffle plate 10 as long as it produces an effect due to the shift of the flow path. The flow path is not limited to one place.

Specific examples of the present invention will be described below.
In this example, the phosphorous phosphate optical glass is melted in a platinum crucible, and the molten glass is caused to flow out of the terminal outlet through a flow path connected to the crucible, and a porous gas made of tungsten carbide that ejects gas. A glass gob for use as a precision press molding preform was obtained by flotation molding on a mold.

As the flow channel, a reinforced platinum flow channel having the same shape as that in FIG. 2 was used. Here, the inner diameter of the flow path is 3 mm (cross-sectional area 7.07 mm ² ), and the outlet is expanded to 9 mm. The total length of the channel, that is, the length from the outlet of the crucible to the outlet at the end of the channel was 2 m.

  In the double pipe portion near the outflow port, the inner diameter of the inner pipe was 6 mm, and the inner diameter of the outer pipe was 9 mm. Between the outsides, reinforced platinum containing 5% gold was used. The length d of the protruding portion of the inner tube was 4 mm.

  The receiving mold was made of porous stainless steel, and received molten glass in a state where air was blown from the receiving surface thereof. Thus, the molten glass floated from the receiving mold to receive glass gob.

  The glass used was melted optical glass mainly composed of phosphorus pentoxide. The crucible was kept at about 900 ° C., and the outflow pipe was kept at about 850 ° C. by electric heating. From the outlet, the molten glass was separated into droplets. The amount of molten glass flowing out at this time was 20 g per minute.

  When this glass gob was visually observed for optical defects such as devitrification and striae, such a defect could not be found, and it was a high-quality glass gob that could be used as a preform for molding an optical element.

1 is an overall schematic view of an apparatus for producing a glass molded product. It is a longitudinal cross-sectional view which shows one Embodiment of the flow path of this invention. It is a longitudinal cross-sectional view which shows other embodiment of the flow path of this invention.

Explanation of symbols

4 Channel 7 Inner tube 8 Outer tube

Claims (11)

A flow path for flowing molten glass connected to the molten glass tank, the tip portion of which is branched into an inner tube and an outer tube arranged at a predetermined interval on the outer side, and the inner tube The inner diameter of the inner pipe is 50% or more of the inner diameter of the outer pipe, and the lower edge of the inner pipe protrudes below the lower edge of the outer pipe. 2. The flow path according to claim 1, wherein the wettability of the molten glass with respect to the inner tube outer wall is better than the wettability of the molten glass with respect to the outer tube outer wall in the vicinity of the outlet of the flow channel. The inner tube is made of a platinum group, a platinum group alloy or a reinforced material thereof, and the outer tube is made of a platinum group containing gold, a platinum group alloy or a reinforced material thereof, or gold or reinforced gold. The flow path according to claim 2. The flow path according to claim 2 or 3, wherein the surface roughness of the outer wall of the inner tube is rougher than the surface roughness of the outer wall of the outer tube. The length in the outflow direction of the protruding portion of the inner pipe is 1 to 10 times the width of the flow path formed between the inner pipe and the outer pipe. Flow path. The flow path according to any one of claims 1 to 5, wherein the flow path cross-sectional center of gravity perpendicular to the molten glass outflow direction has a portion shifted from the upstream-side flow path cross-section center of gravity. The flow path according to claim 6, wherein a baffle plate is provided inside the flow path. The thickness of the baffle plate is 0.1 to 10 times the flow path diameter of the portion where the flow path cross-sectional center perpendicular to the molten glass outflow direction deviates from the upstream flow path cross-section center. Item 7. The flow path according to item 7. The flow path according to any one of claims 1 to 8, wherein the flow path outer wall has a portion that expands in a flow direction of the molten glass. The flow path according to any one of claims 1 to 9, wherein the flow path is used in a press-molding preform manufacturing apparatus that molds molten glass supplied onto a mold into a press-molding preform. It melt | dissolves a glass raw material in a molten glass tank, and flows out a molten glass to a shaping | molding die through the flow path in any one of Claims 1-10 connected to the molten glass tank, and includes shape | molding a glass molded object. A method for producing a glass molded body.

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