JP3862589B2 - Optical glass outflow device and method of manufacturing optical glass block - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for producing a predetermined amount of optical glass block.
[0002]
[Prior art]
Many inventions related to the structure of a molten glass outflow pipe for obtaining an optical glass lump as a molding material of a molding optical element have been proposed in the past. The points of the invention are the following two points.
-Optical glass satisfying optical performance can be obtained.
・ A wide range of optical glass masses with various weights can be obtained, and the weight variation is small and the weight accuracy is high.
[0003]
As such an invention, for example, those disclosed in JP-A-9-59030, JP-A-8-290922, JP-A-8-188419, and JP-A-10-36123 are known. .
[0004]
Japanese Patent Laid-Open No. 9-59030 discloses the following configuration.
[0005]
A large-diameter nozzle is provided at the bottom of the crucible, and the flow rate of the molten glass is controlled by controlling the gap between the large-diameter nozzle opening with a valve mechanism. Allow the glass to drain. Then, the flow rate of the molten glass is controlled by the opening height and opening time of the valve mechanism. The crucible and valve mechanism are made of platinum.
[0006]
Japanese Patent Laid-Open No. 8-290922 discloses the following configuration.
[0007]
The molten glass supply nozzle and the dropping means installed at the lower end of the supply nozzle are configured to be separable. And after cooling a supply nozzle lower end, a supply nozzle and a dripping means are isolate | separated, and the molten glass supply amount is changed by joining the dripping means with a different internal diameter to a supply nozzle.
[0008]
Japanese Patent Laid-Open No. 8-188419 discloses the following configuration.
[0009]
In the supply nozzle for supplying molten glass dropwise, the inner diameter of the tip of the supply nozzle is formed larger than the inner diameter of the supply nozzle. Thereby, it is possible to supply a molten glass larger than the conventional one.
[0010]
Japanese Patent Laid-Open No. 10-36123 discloses the following configuration.
[0011]
In casting the molten glass flowing out of the conduit into the mold, the diameter of the conduit outlet is made larger than that of the conduit body. Thereby, the residence time of the molten glass at the conduit outlet can be lengthened.
[0012]
[Problems to be solved by the invention]
However, the above conventional methods have the following problems.
[0013]
First, the method disclosed in JP-A-9-59030 has the following problems.
[0014]
Since the molten glass flows out from the opening of the small-diameter nozzle near the crucible, the temperature of the molten glass in the crucible and the temperature of the molten glass flowing out from the opening are different. Is difficult. Therefore, a considerably high temperature molten glass flows out from the opening. When the high-temperature molten glass is allowed to flow out in this way, the readily volatile components in the glass evaporate from the surface layer of the molten glass, and the refractive index of the glass surface layer changes. That is, an optical defect called “striation” occurs in the optical glass that has flowed out at such a high temperature.
[0015]
Also, when adjusting the amount of molten glass flowing out by the opening height of the valve mechanism, the opening height of the valve mechanism actually changes slightly due to deformation due to thermal expansion of the valve mechanism and the crucible. Variations in glass outflow will be significant.
[0016]
In addition, the amount of outflow of molten glass at one time is determined by the diameter of the large nozzle, the opening height of the valve mechanism, and the opening time, so it is easy to obtain a relatively large amount of molten glass, but conversely, a minute amount It is difficult to obtain the molten glass with high weight accuracy.
[0017]
Furthermore, since both the crucible and the valve mechanism are made of platinum, if the crucible and the valve mechanism come into contact with each other, the crucible and the valve mechanism are fused and become inoperable, so that workability is poor. In other words, the molten glass outflow by the valve mechanism (so-called plunger method) that is generally used for the outflow of molten glass for bottle glass and the like is an optical glass that requires melting in a platinum crucible because of its high quality characteristics. It is unsuitable for melting.
[0018]
Further, the method disclosed in Japanese Patent Application Laid-Open No. 8-290922 has the following problems.
Even if it is attempted to separate the supply nozzle and the dropping means after cooling the lower end of the supply nozzle, in reality, the separation is extremely difficult. This is because the glass between the supply nozzle and the dropping means is cooled and solidified in a state where the glass has entered, and the supply nozzle and the dropping means cannot be separated unless the glass is broken.
-In addition, in this way, when the glass is melted and flowed out with an apparatus having a structure that can separate the supply nozzle and the dropping means, fine bubbles are often generated in the flowed glass, and this glass can be used as an optical glass. Can not. This is because fine bubbles continue to flow out from the bubbles trapped in the separation part.
[0019]
Further, the techniques disclosed in JP-A-8-188419 and JP-A-10-36123 are almost the same, and it is possible to obtain a larger molten glass lump by these techniques.
[0020]
However, these prior arts also have problems, in that thin “streaks” occur in the resulting glass mass.
[0021]
Here, the hypothesis presumed by the inventor of the present application as the generation process of the “striation” will be described with reference to FIG.
[0022]
In FIG. 2, 1 is a molten glass outlet pipe, 11 is a tapered molten glass outlet, 2 is molten glass, 3 is a molten glass lump, 4 is a receiving mold, 5 is volatile glass, and 6 is an extraordinary refractive index molten glass. is there.
[0023]
The molten glass outflow pipe 1 is connected to a melting crucible (not shown), and a larger molten glass lump 3 can be obtained by opening the molten glass outlet 11 at the lower end in a tapered shape. The receiving mold 4 is made to stand by at a position immediately below the molten glass outlet 11, and the molten glass 2 flowing out in the form of droplets from the molten glass outlet 11 is received on the receiving mold 4 in a continuous state. After receiving the weight of molten glass, the receiving mold 4 is lowered by a predetermined distance and then stops there. Then, constriction occurs in the molten glass, and the constriction progresses due to the surface tension of the molten glass, and the molten glass is immediately spontaneously cut to obtain the molten glass lump 3. This state is shown in FIG.
[0024]
In addition, when the taper angle of the molten glass outlet 11 is large, the molten glass 2 that has flowed out does not spread to the full extent of the molten glass outlet 11, and as shown in FIG. Only spread.
[0025]
Moreover, the easily volatile component in a glass component volatilizes from the surface of the glass of a high temperature molten state. In FIG. 2, this state is schematically shown as the volatile glass 5. This volatilization of the glass occurs both from the molten glass 2 at the molten glass outlet 11 and from the molten glass lump 3 on the receiving mold 4. Further, some of the volatilized glass is agglomerated again and returned to the molten glass 2 or the molten glass lump 3 or deposited on the receiving mold 4 or the molten glass outlet 11.
[0026]
On the other hand, the molten glass 2 flowing through the molten glass outflow pipe 1 flows out of the molten glass outlet 11 after flowing a sufficiently long distance from a melting crucible (not shown). The flow inside the molten glass outflow pipe 1 has a high viscosity, a small pipe inner diameter, and a low flow velocity. Therefore, the Reynolds number is low and the flow is a laminar pipe flow. Therefore, as the molten glass 2 flows inside the molten glass outflow pipe 1, a flow velocity distribution is generated due to viscous resistance, and the flow is fast at the center of the tube, and conversely, the flow is slow near the tube wall. This flow velocity distribution becomes a parabolic velocity distribution.
[0027]
That is, near the pipe wall, the flow velocity is extremely slow and is stagnant. This state continues even when the molten glass spreads through the tapered molten glass outlet 11. Also on the surface of the molten glass, the flow velocity is very slow near the wall of the molten glass outlet 11.
[0028]
On the other hand, volatilization of the molten glass occurs on the surface of the molten glass. In the vicinity of the wall of the molten glass outlet 11, the volatilization continues in the absence of inflow of new glass, so that the glass component is altered and becomes an abnormal refractive index. The extraordinary refractive index molten glass 6 is shown in FIG.
[0029]
Further, the altered glass produced by re-adhering the volatile glass 5 volatilized from the molten glass to the molten glass outlet is also smoldered at this position to become the extraordinary refractive index molten glass 6.
[0030]
And, in the step of obtaining the molten glass lump 3, a slight flow rate is also generated in the extraordinary refractive index molten glass 6 stagnating at this position, so that the extraordinary refractive index molten glass 6 is on the surface layer of the molten glass lump 3, Slightly flows in. This is considered to be observed as “striation” which is an optical defect.
[0031]
Further, even when the molten glass outlet 11 does not spread in a taper shape, this “striation” occurs.
[0032]
This is shown in FIG. The symbols are the same as in FIG.
[0033]
Near the wall surface of the molten glass outlet 11, the flow rate is extremely slow, so that the abnormal refractive index molten glass 6 is stagnated on the surface of the molten glass, and the abnormal refractive index molten glass 6 is obtained in the process of obtaining the molten glass lump 3. Slightly flows and "striation" occurs.
[0034]
On the other hand, since this “striation” is caused by volatilization of the molten glass, the state of occurrence is reduced if the temperature of the outflow molten glass is lowered. However, this time, the viscosity of the glass becomes high, making it difficult to perform so-called “Cherless Cut” (cutting without scissors), and during “Cherless Cut”, filamentous glass is generated and optical defects called “rolling” occur. appear.
[0035]
That is, the present invention solves the production of an optical glass lump of extremely high optical quality free of optical defects such as “striation” that could not be solved by the prior art with high weight accuracy for various weights. It should be a challenge.
[0036]
And the objective of this invention is providing the optical glass outflow apparatus which can manufacture the optical glass excellent in optical quality.
[0037]
Another object of the present invention is to provide an optical glass outflow device that is excellent in optical quality and can produce an optical glass lump having a desired size.
[0038]
Furthermore, still another object of the present invention is to provide an optical glass outflow device capable of stably producing optical glass with excellent optical quality.
[0039]
Still another object of the present invention is to provide an optical glass outflow device capable of producing optical glass lumps having various weights with high optical quality and weight accuracy.
[0040]
Still another object of the present invention is to provide a high-quality optical glass lump suitable as a material for producing a molded optical element.
[0041]
[Means for Solving the Problems]
In order to solve the above-mentioned problems and achieve the object, an optical glass outflow apparatus according to the present invention is provided for melting a glass of crucible, and for discharging the molten glass in the crucible connected to the crucible. An outflow pipe, and the outflow pipe has a throttle portion in the middle thereof, The opening cross-sectional area of the throttle part is 1/3 to 1/20 of the opening cross-sectional area upstream of the throttle part of the outflow pipe, The dimensions are gradually increased from the throttle part toward the tip of the outflow pipe, and the temperature of the throttle part of the outflow pipe is controlled to be higher than the temperature of the part other than the throttle part. It is a feature.
[0043]
In the optical glass outflow device according to the present invention, the throttle portion is provided at a position within 80 mm from the tip of the outflow pipe.
[0047]
In addition, the method for producing an optical glass lump according to the present invention comprises a crucible for melting optical glass. , An optical glass lump manufacturing method for obtaining an optical glass lump by causing molten glass to flow out through an outflow pipe, wherein the molten glass is disposed at an intermediate position of the outflow pipe. Aperture part Provided, Of the throttle Open sectional area of the outflow pipe Upstream of the throttle. 1/3 to 1/20 of the opening cross-sectional area The molten glass In the throttling part, after heating and passing so as to be higher than the temperature of the part other than the throttling part of the outflow pipe, by gradually increasing the size from the throttling part toward the tip of the outflow pipe, A supply step of supplying a predetermined amount onto the receiving mold and a cutting step of cutting the molten glass by the surface tension of the molten glass are provided.
[0049]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described.
[0050]
First, an outline of one embodiment will be described.
[0051]
In one embodiment of the present invention, in the molten glass outflow pipe connected to the optical glass melting crucible, the inner diameter of the pipe is reduced in the middle of the outflow pipe.
[0052]
By letting the molten glass flow out through the molten glass outlet pipe connected to the melting crucible, it becomes possible to make a temperature difference between the molten crucible and the molten glass outlet, and the temperature of the molten glass outlet is relatively low. As a result, "striation" can be prevented. For that purpose, the length of the molten glass outlet pipe is desirably long.
[0053]
On the other hand, if the length of the molten glass outflow pipe is long, the molten glass has a high viscosity, so that it is greatly affected by the viscous resistance and develops into a flow having a parabolic velocity distribution. That is, the flow velocity is fast at the center of the outflow pipe, but conversely, the flow velocity is very slow near the wall of the outflow pipe.
[0054]
However, such a flow also becomes a uniform flow with a uniform flow velocity distribution by reducing the inner diameter of the pipe in the middle of the outflow pipe. By narrowing the inner diameter of the pipe near the molten glass outlet, the flow velocity distribution can be kept close to the molten glass outlet. That is, even at the molten glass outlet, the flow velocity near the wall is sufficient, and the molten glass outflowed by volatilization does not stay in the portion where the molten glass surface and the wall of the molten glass outlet are in contact with each other. Is done. This is shown in FIG.
[0055]
As a result, it is possible to produce high-quality optical glass without “streaks”.
[0056]
FIGS. 4 to 8 are schematic diagrams showing the development of the flow velocity distribution due to viscosity and the uniform flow velocity due to the restriction when the viscous fluid flows in the pipe.
[0057]
FIG. 4 shows a state in which the molten glass flows from the molten crucible 7 to the molten glass outflow pipe 1, and since the molten crucible 7 is in a quasi-static state, the molten glass flowing in from here is almost uniform. The flow rate of
[0058]
5, 6 and 7 are diagrams showing the flow development inside the molten glass outflow pipe. Due to the viscous resistance from the tube wall, the flow velocity distribution in the tube becomes slower as the flow velocity near the tube wall becomes as shown in FIG.
[0059]
As the flow further proceeds in the outflow pipe, the velocity distribution becomes more prominent, resulting in a state as shown in FIG. 6, and finally has a parabolic velocity distribution as shown in FIG. .
[0060]
FIG. 8 shows a state in which the flow state having the velocity distribution is made uniform by narrowing the inner diameter of the pipe.
[0061]
In addition, although the knowledge about such a flow velocity distribution is obtained from an experiment related to a general liquid pipe flow at room temperature, according to the viscous fluid theory, the same phenomenon occurs in the molten glass outflow pipe, It is thought that it has occurred.
[0062]
Moreover, in this embodiment, in the molten glass outflow pipe connected to the optical glass melting crucible, the pipe inner diameter is once reduced in the middle of the outflow pipe, and the pipe inner diameter is expanded again to a desired dimension.
[0063]
It is the same as that described above that the flow velocity distribution of the molten glass in the pipe becomes a uniform flow by narrowing the pipe inner diameter in the middle of the molten glass outflow pipe. After that, even if the pipe inner diameter is continuously expanded to a desired dimension, the molten glass flow is sufficiently close to the wall in the continuously expanding molten glass outflow portion. Even at the portion where the wall of the outlet comes into contact, molten glass that has deteriorated due to volatilization does not stay and the molten glass flows out.
[0064]
As a result, it is possible to produce high-quality optical glass without “streaks”.
[0065]
In the present embodiment, since the pipe inner diameter of the molten glass outlet is expanded to a desired dimension, when obtaining a large glass lump, it is possible to instantaneously perform the process of receiving the molten glass in the receiving mold, As a result, it is possible to prevent the occurrence of irregularities called gob-in marks generated on the lower surface of the optical glass block.
[0066]
Moreover, in this embodiment, the pipe internal diameter is restrict | squeezed within the range of the distance of 80 mm from the outflow port of a molten glass outflow pipe.
[0067]
By narrowing the pipe inner diameter in the middle of the molten glass outflow pipe, the flow velocity distribution of the molten glass in the pipe becomes uniform, and by flowing the molten glass in a state where there is a sufficient flow velocity near the pipe wall. It has already been explained that molten glass can flow out without stagnation of molten glass whose refractive index has changed due to volatilization.
[0068]
However, if the throttle part of the inner diameter of the pipe is installed at a position far from the molten glass outlet, the length of the molten glass outflow pipe after passing through the throttle part becomes long. Then, the flow velocity near the wall becomes extremely slow at the molten glass outlet, and the volatile glass stays and optical defects such as “streaks” occur.
[0069]
The inventor of the present application conducts an experimental study on the installation position of the throttle of the pipe inner diameter, and obtains high-quality optical glass by reducing the pipe inner diameter within a range of a distance of 80 mm from the outlet of the molten glass outflow pipe. I found out that I can.
[0070]
Further, in this embodiment, the restriction of the inner diameter of the pipe is in the range from 1/3 to 1/20 in terms of the cross-sectional area ratio.
[0071]
By squeezing the pipe diameter in the middle of the molten glass outflow part, the molten glass is made to flow uniformly, the flow velocity near the wall at the glass outlet is sufficient, the retention of the altered glass is eliminated, and high quality glass can flow out. Already explained.
[0072]
If the restriction of the inner diameter of the pipe is loose, that is, the ratio of the inner cross-sectional area of the pipe before drawing and the inner cross-sectional area of the pipe of the drawing part (= the inner cross-sectional area of the pipe of the drawing part / the inner cross-sectional area of the pipe before drawing) ) Is large, the effect of the aperture may not be sufficiently obtained. The inventor of the present application has conducted an experimental study on the diameter of the pipe inner diameter. When the diameter of the pipe inner diameter is larger than 1/3 in the cross-sectional area ratio, the effect of the diaphragm cannot be sufficiently obtained, and the optical glass obtained can be obtained. We found that the quality is low.
[0073]
Conversely, when the pipe inner diameter is tight, that is, the ratio of the inner cross-sectional area of the pipe before throttling to the inner cross-sectional area of the pipe of the throttling section (= the inner cross-sectional area of the pipe of the throttling section / the inner section of the pipe before throttling) When the cross-sectional area is small, the flow rate of the molten glass at the narrowed portion is considerably high, while the pressure in the portion is considerably reduced by Bernoulli's theorem. Then, the gas component dissolved in the molten glass is generated as fine bubbles.
[0074]
The inventor of the present application has conducted an experimental study on the diameter of the pipe inner diameter, and when the pipe inner diameter is smaller than 1/20 in the cross-sectional area ratio, the pressure in the molten glass is reduced due to the increase in the flow velocity at the throttle. It was found that fine bubbles were generated.
[0075]
That is, it has been found that high-quality optical glass can flow out if the aperture of the inner diameter of the pipe is in the range of 1/3 to 1/20 in cross-sectional area ratio.
[0076]
Further, in this embodiment, the temperature can be individually controlled in the pipe inner diameter restricting portion and the other portions.
[0077]
In the optical glass melting apparatus described above, the pipe inner diameter restricting portion becomes the rate-limiting portion in the molten glass outflow pipe. This is because the flow resistance at the throttle portion is larger than that at other portions of the pipe.
[0078]
Therefore, it is possible to control the outflow amount of the molten glass to a desired value by individually controlling the temperatures of the pipe inner diameter restricting portion and the other portions.
[0079]
Further, in the present embodiment, when the molten optical glass is caused to flow out from the optical glass melting crucible through the molten glass outflow pipe, the molten glass flows out while the pipe inner diameter is reduced in the middle of the outflow pipe. To do.
[0080]
As already explained, by narrowing the pipe diameter in the middle of the molten glass outflow part, the molten glass is made to flow uniformly, the flow velocity near the wall at the glass outlet is sufficient, the retention of the modified glass is eliminated, and high quality Can drain the glass. Therefore, the optical glass obtained in this way has no optical defects such as striae and is of high quality.
[0081]
Further, in this embodiment, the molten optical glass that has flowed out with the pipe inner diameter reduced is received on the receiving mold by a predetermined weight, and then the molten glass is cut by the surface tension of the molten glass, A glass lump is obtained.
[0082]
In order to cut the molten glass with the surface tension of the molten glass by so-called shearless cutting and obtain a molten optical glass lump, it is necessary to lower the viscosity of the molten glass, and therefore the temperature of the molten glass must be increased. .
[0083]
However, on the other hand, when such a high-temperature molten glass is caused to flow out, volatilization from the surface is intense and denatured glass is generated.
[0084]
Here, in this embodiment, by narrowing the pipe diameter in the middle of the molten glass outflow part, the molten glass is made to be a uniform flow, the flow velocity near the wall at the glass outlet is sufficient, and the residence of the modified glass is eliminated, High quality glass can flow out. Therefore, the optical glass block obtained in this way has no optical defects such as striae and is of high quality.
[0085]
Next, an embodiment of the present invention will be specifically described with reference to FIGS.
[0086]
FIG. 1 is a diagram for explaining the vicinity of the molten glass outlet, and FIG. 9 is a diagram for explaining the entire molten glass outflow device.
[0087]
In FIG. 1, 1 is a molten glass outflow pipe, 2 is a molten glass, 3 is a molten glass lump, 4 is a receiving mold, 5 is a volatile glass, 8 is an inner diameter throttle part of the molten glass outflow pipe, and 11 is a molten glass outlet. is there. In FIG. 9, 1 is a molten glass outflow pipe, 7 is a melting crucible, 8 is an inner diameter restricting portion of the molten glass outflow pipe, and 9a and 9b are individually energized and heated for the molten glass outflow pipe 1 and the inner diameter restricting portion 8. 11 is a molten glass outlet.
[0088]
The melting crucible 7 is made of platinum, and is heated and held at the glass melting temperature by a heater (not shown) installed around the melting crucible 7. An optical glass material (not shown) is put into a melting crucible 7 and melted.
[0089]
The molten glass outflow pipe 1 is made of platinum and connected to the lower part of the melting crucible 7.
[0090]
The inner diameter restricting portion 8 provided in the molten glass outflow pipe 1 is provided near the lower end of the molten glass outflow pipe 1, as shown in FIG. As shown in FIG. 1, after passing through the inner diameter restricting portion 8, the pipe inner diameter spreads smoothly in a tapered shape and reaches the molten glass outlet 11.
[0091]
The molten glass outflow pipe 1 and the inner diameter restricting portion 8 are each heated by energization by separate electric circuits 9a and 9b and controlled to a desired temperature, whereby the outflow amount of the molten glass can be controlled. By controlling the electric circuits 9a and 9b, the molten glass flows out from the molten glass outlet 11 in the form of droplets.
[0092]
The receiving die 4 is connected to an NC (numerical control) device, and can control its moving position and moving speed with high accuracy.
[0093]
In the process of receiving the glass lump 3 on the receiving mold 4, the receiving mold 4 first rises to a position directly below the molten glass outlet 11. Then, the molten glass is continuously received on the receiving mold 4 and begins to accumulate. Thereafter, the receiving mold 4 is lowered at a minute speed, and a desired weight of molten glass is obtained on the receiving mold 4. Therefore, the receiving mold 4 is rapidly lowered by a predetermined distance. Then, constriction occurs in the molten glass, and the constriction progresses due to the surface tension of the molten glass, the molten glass is naturally cut, and the molten glass lump 3 is obtained.
[0094]
The glass lump 3 thus obtained is free from optical defects such as striae and is of high quality.
[0095]
Thus, according to the present embodiment, a glass lump having no striae is obtained because the flow velocity distribution of the molten glass in the molten glass outflow pipe 1 becomes uniform due to the restriction, and even at the molten glass outlet, It is considered that there is a sufficient flow rate near the glass, and the retention of the modified glass can be prevented.
[0096]
In the present embodiment, it is desirable that the pipe inner diameter is reduced within the range of a distance of 80 mm from the outlet 11 of the molten glass outflow pipe 1, and the restriction of the pipe inner diameter is a cross-sectional area ratio, It is desirable to be in the range of 1/3 to 1/20.
[0097]
【Example】
Hereinafter, specific examples of the present embodiment and comparative examples will be described.
[0098]
Example 1
In Example 1, the pipe inner diameter squeezed part is located at the lower end of the molten glass outflow pipe, and after the pipe inner diameter is squeezed, it again tapers and reaches the molten glass outlet, from this optical glass melting device. The example which obtains an optical glass lump from the molten optical glass which flows out is demonstrated.
[0099]
The apparatus configuration of Example 1 is shown in FIGS.
[0100]
In Example 1, the inner diameter of the molten glass outlet pipe 1 is 6 mm, and the length of the outlet pipe 1, that is, the length from the lower end of the melting crucible 7 to the outlet 11 is 300 mm.
[0101]
The inner diameter restricting portion 8 is provided at a position 15 mm above the glass outlet 11, the inner diameter of the inner diameter restricting portion is 1.5 mm, and the area ratio is 1/16. The length of the aperture is 5 mm. After the throttle part, the inner diameter of the pipe continuously tapers, and the inner diameter of the pipe at the outlet 11 is 10 mm.
[0102]
The receiving mold 4 is made of porous carbon and receives molten glass in a state in which gas is blown from the back surface thereof, thereby receiving the molten glass floating from the receiving mold 4 to obtain a glass lump 3. .
[0103]
In Example 1, optical glass equivalent to SK12 was melted. The melting crucible 7 was maintained at 1100 ° C., the outflow pipe 1 was maintained at 900 ° C., the inner diameter restricting portion 8 was maintained at 1000 ° C., and the molten glass was discharged from the outflow port 11 in the form of droplets. The amount of molten glass flowing out at this time was 40 g per minute.
[0104]
The receiving mold 4 is set at a position 5 mm below the outlet 11 and lowered at a speed of 0.1 mm per second. After 10 seconds, the receiving mold 4 is rapidly lowered by 7 mm, the molten glass is naturally cut, and the molten glass lump is removed. Obtained. In this way, a glass block having a weight of 7 g was obtained.
[0105]
This glass lump was free from optical defects such as striae and was a high-quality glass lump suitable as an optical element molding material.
[0106]
Even when the pipe inner diameter of the inner diameter narrowed portion 8 is in the range of 1.3 mm to 3.5 mm, that is, even when the sectional area ratio of the narrowed portion is in the range of 1/3 to 1/20, the high quality is similarly obtained. A glass lump can be obtained.
[0107]
Thus, according to the present Example, a comparatively big high quality glass lump can be obtained.
[0108]
(Comparative example)
The comparative example with respect to Example 1 is shown.
・ Conventional method
An explanation will be given of a case where the outflow pipe is not provided with a restriction but flows out with an outflow pipe having a constant inner diameter, and the outflow port is expanded in a tapered shape.
[0109]
As the molten glass outflow pipe, a pipe having a length of 300 mm and an inner diameter of 4 mm was used, and a pipe expanded in a tapered shape so that the inner diameter of the pipe became 10 mm at the outlet. The outflow pipe temperature was set to 800 ° C. and the outlet temperature was set to 900 ° C. to obtain a molten glass lump. However, the obtained glass lump had striae and had low optical quality.
[0110]
When the outlet temperature is lowered, the striae is reduced, but so-called shearless cutting becomes difficult and is not suitable as an optical element molding material.
・ If the aperture is too weak
The case where the restriction of the outflow pipe is too weak and ineffective will be described.
[0111]
The inner diameter of the pipe inner diameter throttle portion was 4 mm, that is, the throttle cross-sectional area ratio was 1 / 2.25, and other conditions were the same as in Example 1, and the molten glass was flowed out. The glass lump obtained in this way had striae and low optical quality.
[0112]
This is because the effect of the present embodiment did not appear because the diaphragm was too weak.
・ If the aperture is too strong
An explanation will be given of a case where the outflow pipe is too narrow and a defect occurs.
[0113]
The inner diameter of the pipe inner diameter squeezed portion was set to 1 mm, that is, the squeezed cross-sectional area ratio was set to 1/36, and other conditions were the same as those in Example 1, and the molten glass was discharged. In this way, fine bubbles are generated in the molten glass that has flowed out, and bubbles remain in the obtained glass lump, so that the quality is low.
[0114]
This is because the squeezing is too strong, the pressure decreases as the flow rate of the molten glass at the squeezed portion increases, and the gas dissolved in the molten glass is foamed.
[0115]
(Example 2)
In the second embodiment, a case will be described in which, after the outflow pipe is narrowed, the inside diameter of the pipe is left as it is, and the outflow pipe is allowed to flow out.
[0116]
The structure other than the molten glass outlet is the same as that of the first embodiment. The molten glass outlet has a pipe shape with an inner diameter of 1.5 mm and an outer diameter of 3 mm.
[0117]
Also in Example 2, optical glass equivalent to SK12 was melted. The melting crucible 7 was kept at 1100 ° C., the outflow pipe 1 was kept at 800 ° C., the pipe inner diameter constricted portion was kept at 900 ° C., and the molten glass flowed out in the form of droplets from the outlet 11. The amount of molten glass flowing out at this time was 10 g per minute.
[0118]
The receiving mold 4 is set at a position 3 mm below the outlet 11 and lowered at a speed of 0.1 mm per second. After 3 seconds, the receiving mold 4 is rapidly lowered by 4 mm, the molten glass is naturally cut, and the molten glass lump is removed. Obtained. In this way, a glass lump with a weight of 0.5 g was obtained.
[0119]
This glass lump was free from optical defects such as striae and was a high-quality glass lump suitable as an optical element molding material.
[0120]
Thus, according to the present Example, a comparatively small high quality glass lump can be obtained.
[0121]
(Comparative example)
The comparative example by the conventional method with respect to Example 2 is shown.
[0122]
An explanation will be given of a case where the outflow pipe is not provided with a restriction but flows out to the outflow port with an outflow pipe having a constant inner diameter.
[0123]
A molten glass outlet pipe having a length of 300 mm and an inner diameter of 1.5 mm was used. The outflow pipe temperature was set to 800 ° C. and the outlet temperature was set to 900 ° C. to obtain a molten glass lump. However, the obtained glass lump had striae and had low optical quality.
[0124]
When the outlet temperature is lowered, the striae is reduced, but so-called shearless cutting becomes difficult and is not suitable as an optical element molding material.
[0125]
Example 3
In the third embodiment, the case where the throttle portion of the outflow pipe is located slightly away from the outflow port will be described.
[0126]
In the apparatus configuration of Example 3, as shown in FIG. 10, the inner diameter restricting portion 8 was provided at a position 80 mm above the outlet 11 of the outflow pipe. The throttle part has an inner diameter of 1.5 mm and a length of 5 mm.
[0127]
The inner diameter of the outflow pipe other than the throttle is 4 mm, and the entire length of the outflow pipe is 300 mm. The outflow part has a pipe shape with an inner diameter of 4 mm and an outer diameter of 6 mm.
[0128]
In Example 3 as well, optical glass equivalent to SK12 was melted. The melting crucible 7 was maintained at 1100 ° C., the outflow pipe 1 was maintained at 850 ° C., the pipe inner diameter throttle was maintained at 950 ° C., and the molten glass was flowing out from the outlet 11 in the form of droplets. The amount of molten glass flowing out at this time was 20 g per minute.
[0129]
The receiving mold 4 is set at a position 3 mm below the outlet 11 and lowered at a speed of 0.1 mm per second. After 6 seconds, the receiving mold 4 is rapidly lowered by 4 mm, the molten glass is naturally cut, and the molten glass lump is removed. Obtained. In this way, a glass block having a weight of 2 g was obtained.
[0130]
This glass lump was free from optical defects such as striae and was a high-quality glass lump suitable as an optical element molding material.
[0131]
As described above, according to this embodiment, since the wiring of the electric circuit for heating the throttle portion can be installed at a high position, contact between the wiring and the receiving mold can be prevented, and as a result, the degree of freedom of the device configuration can be reduced. It becomes possible to raise.
[0132]
(Comparative example)
As a comparative example of Example 3, a case will be described in which the effect of the present embodiment is not seen because the installation position of the inner diameter throttle portion is too far from the outlet.
[0133]
In the same structure as in Example 3, the molten glass flowed out in a state where the inner diameter restricting portion was installed at a position of 100 mm from the outlet, there was a slight striae in the obtained glass lump, which was not a preferable quality. .
[0134]
Example 4
In the fourth embodiment, a case where two inner diameter throttle portions are provided in the outflow pipe will be described.
[0135]
FIG. 11 shows an apparatus configuration of the fourth embodiment. Inner diameter restricting portions are provided at two locations, the center portion and the lower end portion of the outflow pipe. The entire length of the outflow pipe is 300 mm, the central throttle is provided at a position 120 mm from the lower end of the pipe, and the throttle at the lower end is provided at a position 10 mm from the lower end of the pipe.
[0136]
The inner diameter of the outflow pipe is 4 mm, the inner diameter of the central throttle is 1.5 mm, the cross-sectional area ratio is 1/7, the inner diameter of the lower end is 2 mm, and the cross-sectional area ratio is 1/4.
[0137]
The outflow pipe is divided into three zones of a central throttle portion, a portion above it, and a portion below it, and electric circuits 9a, 9b, and 9c are provided so that the temperature can be controlled.
[0138]
In Example 4 as well, optical glass equivalent to SK12 was melted. The melting crucible 7 is kept at 1100 ° C., the upper part of the outflow pipe is 900 ° C., the central constricted part is kept at 850 ° C., the lower part of the outflow pipe is kept at 1000 ° C., and the molten glass flows out in the form of droplets from the outlet 11. I was in a state. The amount of molten glass flowing out at this time was 10 g per minute.
[0139]
The receiving mold 4 is set at a position 3 mm below the outlet 11 and lowered at a speed of 0.1 mm per second. After 5 seconds, the receiving mold 4 is rapidly lowered by 4 mm, the molten glass is naturally cut, and the molten glass lump is removed. Obtained. In this way, a glass lump with a weight of 0.8 g was obtained.
[0140]
This glass lump was free from optical defects such as striae and was a high-quality glass lump suitable as an optical element molding material.
[0141]
According to this example, a glass mass with extremely high weight accuracy could be obtained. This is because the glass flow rate can be controlled by independently controlling the temperature of the throttle portion at the center of the pipe.
[0142]
【The invention's effect】
As described above, according to the present invention, a high-quality optical glass lump free from optical defects such as striae can be produced.
[Brief description of the drawings]
FIG. 1 is an enlarged view of the vicinity of a glass outlet in a molten glass outlet according to an embodiment.
FIG. 2 is an enlarged view of the vicinity of a glass outlet in a conventional molten glass outlet.
FIG. 3 is an enlarged view of the vicinity of a glass outlet in a conventional molten glass outlet.
FIG. 4 is a diagram illustrating the operation of an embodiment of the present invention.
FIG. 5 is a diagram illustrating the operation of an embodiment of the present invention.
FIG. 6 is a diagram for explaining the operation of an embodiment of the present invention.
FIG. 7 is a diagram for explaining the operation of an embodiment of the present invention.
FIG. 8 is a diagram illustrating the operation of an embodiment of the present invention.
9 is a diagram illustrating Example 1. FIG.
10 is a diagram illustrating Example 3. FIG.
FIG. 11 is a diagram for explaining Example 4;
[Explanation of symbols]
1 Molten glass outflow pipe
3 Molten glass lump
4 receiving type
7 melting crucible
8 Inner diameter throttle
11 Outlet

Claims (3)

A crucible for melting optical glass;
An outflow pipe connected to the crucible for discharging the molten glass in the crucible;
The outflow pipe has a constriction part in the middle thereof, and the opening cross-sectional area of the constriction part is 1/3 to 1/20 of the opening cross-sectional area upstream of the constriction part of the outflow pipe, The dimensions are gradually increased from the throttle part toward the tip of the outflow pipe, and the temperature of the throttle part of the outflow pipe is controlled to be higher than the temperature of the part other than the throttle part. Optical glass drainage device characterized.   2. The optical glass outflow device according to claim 1, wherein the throttle portion is provided at a position within 80 mm from a tip of the outflow pipe. From a crucible for melting an optical glass, a method of manufacturing an optical glass gob to obtain an optical glass gob by the outflow molten glass through the outlet pipe,
Wherein a throttle portion is provided in the middle position of the flow pipe, Ri 1/3 1/20 der opening cross-sectional area of the upstream side of the narrowed portion of the aperture cross-section is the outlet pipe of the narrowed portion, the molten glass In the throttling part, after being heated and passed so as to be higher than the temperature of the part other than the throttling part of the outflow pipe, the size is gradually increased from the throttling part toward the tip of the outflow pipe. And a supply process for supplying a predetermined amount on the receiving mold,
And a cutting step of cutting the molten glass by surface tension of the molten glass.

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