JPH06345443A - Flow controlling method for glass and apparatus therefore - Google Patents

Abstract

PURPOSE:To maintain a stable flow and viscosity over a long time of glass outflow by controlling the viscosity at the downstream side of a region provided with a temperature controlling means for a duct from a melting tank. CONSTITUTION:Glass G is charged in a platinum crucible 12 held on a crucible supporting body 14 placed in a furnace 16 provided with heat sources 42 and a thermo-couple 44. The glass is molten under stirring with stirrer blades 38 attached at the lower end of a rotary shaft 40 and made homogeneous. Then, the molten glass G is allowed to flow out into a tubular duct 32 for glass outflow provided with 3 circuits of heat sources 46 and 3 units of thermo-couples 50. At the first and the second zone, glass temperatures are adjusted and the flow of the molten glass is controlled and thereafter the viscosity of the molten glass is adjusted by temperature change at the third zone.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass flow rate control method and control apparatus which is characterized by adjusting the flow rate and viscosity of glass flowing out in a glass melting apparatus for flowing molten glass out of a furnace through a conduit.

[0002]

2. Description of the Related Art Conventionally, in order to obtain a molding material or the like by flowing a highly homogeneous molten glass such as an optical glass from a refiner (melting furnace) and supplying it as a glass gob (glass lump) or a glass flow, the bottom of the refiner is used. A glass melting device with a conduit connected is used.

In order to let this molten glass flow out, it is necessary to heat the conduit appropriately. In particular, in order to always stably supply glass to the molding machine outside the furnace in a suitable state in terms of glass flow rate, glass viscosity, shape of glass gob and glass flow, etc., the temperature setting of the conduit And heating means are important. Also, the shape of the conduit (tube inner diameter, length, etc.)
, Material, outflow end (orifice), conduit heating means,
When designing the equipment, including the temperature control method for the conduit, it is necessary to fully consider the high temperature physical properties of the molten glass, the specifications of the product to be produced, and the productivity.

For example, in order to manufacture molten optical glass into various lenses, prisms, or slab-shaped continuous molded products, it is required to manufacture products of various shapes and weights with the same melting apparatus. It is desirable that the same conduit be used to change the outflow rate in a wide range of several cc to 100 cc / min. In addition, various molding methods (
Casting method for slab-shaped compact, casting method for drain cast type direct press, gob feeding method for rotary type molding machine, method for feeding gobs in droplet form by shearless method, horizontal press molding the viscosity of the glass suitable for the supply system, etc.) of the glass rod to the machine, 10 ¹ to 10
It is desirable to be able to adjust in a wide range of ⁸ dPa · s.

Further, a new problem arises when a number of kinds of glasses having different chemical compositions and high temperature viscosity characteristics are produced in the same melting apparatus. In other words, these glasses have different physical properties at high temperatures such as liquidus temperature, devitrification, high-temperature volatility, and bubble re-generation temperature, so even if the desired flow rate and the viscosity of the glass gob or glass flow can be adjusted, the quality of the glass will not be improved. It may be insufficient. For example, devitrification occurs in the conduit and the tube wall, which impairs the homogeneity of the glass flow, contains fine crystal particles, regenerates bubbles on the tube wall of the conduit, and enters the glass flow as it is. Will end up. Further, it is known that striae are generated in the glass flow in the entire outflow system including the holding temperature and stirring conditions of the refiner and the atmosphere of the outflow orifice.
Therefore, there is a need for a technique for flowing out glass so that these problems do not occur.

There are roughly two types of melting methods. The continuous type in which the liquid level change of the refiner slightly fluctuates within a range of several mm to several cm, and the system in which the glass is melted, clarified and homogenized, and then intermittently flows out according to the passage of the outflow time. It is a batch type in which the liquid level changes greatly in the range of 20 cm to 1 M as the depth of the pot corresponding to the refiner. For example, when the glass is discharged from a one-pot type crucible through a conduit, the flow rate due to the drop in the liquid level changes with time according to Hagen-Poiseuille's law. Therefore, Japanese Patent Publication No. 52-1404 discloses a method of temporally changing the cutting interval of a glass flow for the purpose of continuously producing a glass gob having a constant weight.
As a further improvement thereof, Japanese Patent Publication No. 53-35573 discloses that the vertical length of the conduit in the downward direction is made sufficiently large for the purpose of reducing the decrease amount of the flow rate and making the time change of the cutting interval linear. There is.

However, the change in the weight of the glass gob is not only affected by the change in the flow rate due to the change in the liquid level, but is also slightly affected by the change in the manufacturing environment and the change in the operating condition of the molding machine in the continuous molding for a long time. In order to suppress the fluctuation within 1%, a unique control technique is required, and it is desired to reduce the fluctuation to 0.5% or less. These changes are temperature variations of the glass in the refiner, changes in the temperature distribution over the entire conduit over time, changes over time in temperature measurement that often occur when using thermocouples and compensation leads, changes in the air flow at the orifice,
There are temporal changes in temperature due to the heating means of the orifice, changes in mold temperature of the molding machine directly below the orifice, changes in temperature, and the like.

In order to adjust the glass flow rate and viscosity to satisfy the above various requirements, the heating means of the conduit and the method of controlling the temperature thereof are extremely important. As a means for heating the conduit, there is a direct current heating method for the conduit, as disclosed in Japanese Patent Publication No. 40-11742. This is a method of directly applying a DC or AC voltage to a platinum or platinum alloy pipe-shaped conduit to heat the entire conduit.The temperature of the thermocouple attached to the conduit is monitored, and that point is directly responsive and temperature-controlled. It is a method of controlling the glass flow rate by controlling the viscosity of the glass.

A method is also known in which the direct electric heating of the conduit is divided into a plurality of zones and is constituted by several circuits for heating. However, in this method, heat is dissipated by heat conduction from the feeding flange, and the temperature of the flange becomes lower than that of the central part between the flanges, which often causes the glass to crystallize on the inner wall of the conduit. Causes problems such as striae of the glass, deterioration of quality, and instability of flow rate.

On the other hand, in Japanese Examined Patent Publication No. 4-43849, a large number of perforations are provided in the flange portion to increase the current density in the flange portion while maintaining the mechanical strength to increase the amount of heat generation. A heating device for improving the temperature distribution is disclosed. However, in this heating device, when trying to flow out by changing the flow rate and the viscosity of the glass, the balance of the heat balance is disturbed, which results in a temperature difference, and in the flange shape having the same many perforations,
It is considered that it is not possible to take sufficient measures to produce many glasses having different chemical compositions and high-temperature physical properties (specific heat, specific gravity, thermal conductivity, viscosity, etc.).

Another method for controlling the temperature of the conduit is divided into an upper part and a lower part of the conduit for the purpose of dropping the glass liquid from the tip of the orifice, and the temperature of the upper part is 50 to 2 from the lower part.
Japanese Patent Publication No. 4-32772 discloses that the temperature is controlled to be higher by 00 ° C. In this method, the temperature of the glass drop is measured with a radiation thermometer, the interval between the signal and the dropping time of the glass is calculated by the control unit, and each heating source of the furnace, the pipe upper part, the pipe lower part, and the nozzle tip part is calculated. The necessary energization amount is added to control.

However, this indirect heating method cannot provide a quick response of the flow rate and the viscosity of the glass. In addition, there is no description of a longer-term fluctuation even if the weight accuracy of 100 glass drops within 1% within a short time due to the outflow from a 2-liter one-pot type melting crucible, and the flow rate and glass weight accuracy are stable. There is no specific description about the control method for conversion. If the viscosity of the glass fluctuates unnecessarily during continuous molding for a long time, for example, a gob-shaped variation occurs,
Further, the temperature distribution of the gob fluctuates, which adversely affects the yield when the gob is press-molded. Particularly, in the method of supplying the glass rod to the horizontal press molding machine, the descending speed also changes, and as a result, the weight variation of the lens and the formability itself are adversely affected.

Further, in the above-mentioned prior art relating to the outflow of molten glass, there has been no suggestion of individually controlling the flow rate and viscosity of glass.

[0014]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems. That is, even in the continuous type glass melting / flowing apparatus, the glass is melted batchwise and intermittently flows out, and even in the one-pot type apparatus in which the glass liquid level changes in accordance with the elapse of the flowing time, Flow rate control method and device for glass capable of adjusting flow rate and viscosity separately, maintaining stable flow rate and viscosity even during long-term glass outflow, and stably supplying glass gob and glass flow without devitrification and bubbles To provide.

[0015]

The above object is to provide a glass flow rate control method for adjusting the flow rate of molten glass flowing out of a melting furnace through a conduit to the outside of the furnace in a glass flow rate control method. It can be achieved by a glass flow rate control method characterized by controlling the viscosity of molten glass by a temperature change in a region further downstream than a region for temperature control for control, and a glass outflow device having such means. .

[0016]

In the prior art relating to the outflow of molten glass, the flow rate and viscosity of the glass were not individually controlled by adjusting the temperature of the conduit. On the other hand, in the present invention, a zone where the temperature is adjusted for controlling the flow rate of the conduit (hereinafter referred to as FC zone), and a zone where the temperature is adjusted for viscosity control downstream thereof (hereinafter referred to as GC zone) are provided. By adjusting the flow rate and the viscosity individually, the flow rate and the viscosity can be controlled accurately in a wide range, and the above object can be achieved.

As a more specific example, the present invention provides, for example, that the conduit is sufficiently long and the conduit is divided into a plurality to set the temperature of each individual zone. The glass flow rate is adjusted by changing the temperature of the conduit portion of one zone (FC zone) in the multiple zones of the conduit.
In multiple zones of the conduit, the viscosity of the glass is adjusted by varying the temperature of the conduit portion of the final zone (GC zone) including the outlet end of the conduit. It consists of that point.

In the present invention, the GC zone is typically the area containing the glass outlet end of the conduit. Further, by providing at least one zone between the FC zone and the GC zone without contacting each other, and reducing the interference of temperature setting changes of the conduit sections of the two zones, the flow rate and the viscosity can be independently calculated with high accuracy. It can be controlled, and more excellent results can be obtained with respect to stability and the like in continuous molding for a long time.

As a method of controlling the temperatures of the FC zone and the GC zone of the conduit, there are a method of directly conducting electric heating and a method of using the direct conducting heating method together with the conduit arranged indirectly in a furnace. There are modes. Specifically, for example, the divided conduit is placed in a tubular or box-shaped furnace,
The furnace may have multiple heat sources corresponding to each zone so that the conduits can be indirectly heated individually, or the divided conduits can be arranged in a plurality of continuous furnaces and the individual conduits can be indirectly connected. For example, the heating method may be combined with the above heating method to individually heat the conduits. Further, in particular, in the method of directly heating by energization, when energizing a single-phase or three-phase alternating current, the combination of the electrical phases is adjusted for each electrode in the adjacent zones to adjust the temperature distribution in the vicinity of the electrodes. By doing so, it is possible to avoid partial overheating and overcooling and supply the glass to various molding machines in a better quality.

The FC zone is desirably 0 to 1,500 mm, preferably 20 to 1,000 from the end of the melting furnace.
It is preferable that they are located within an area separated by mm. On the other hand, the GC zone may be in a zone that is preferably 0-500 mm, preferably 0-350 mm away from the outlet of the conduit.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

<Embodiment 1> FIG. 1 (a) is an embodiment of the apparatus of the present invention, and is a schematic sectional view showing an apparatus for flowing molten glass from a one-pot type crucible using a conduit. 1 (b) is an enlarged view of the conduit portion.

In FIG. 1, 12 is a platinum crucible having an internal volume of 15 liters, 14 is a crucible supporting member made of a refractory material, and 28 through holes are provided to improve heat conduction. The crucible has a portion 12a having a smaller diameter by gradually narrowing the upper part, and a small-diameter portion 12b following the portion 12a.
A receiving portion 12c for introducing the raw material is formed in the small diameter portion. Such a crucible shape is suitable for highly volatile glass, and it is possible to reduce intra-lot variation in the refractive index due to selective volatilization of glass components.

The bottom of the crucible 12 is inclined in one direction, and the glass outflow pipe-like conduit 32 is connected to the side wall of the crucible at the lowest position. G shows the glass liquid level in the outflow start state. The crucible is installed inside the furnace 16 having a heat source 42 and a thermocouple 44 for measuring the temperature inside the furnace. The homogenization of the molten glass is carried out by rotating a screw-peller type stirring blade 38 attached to the lower end of a rotary shaft 40 extending from above into the furnace. The conduit 32 extends through the lower part of the side wall of the furnace 16 to the outside of the furnace,
The tip is a glass outflow orifice (outlet). The conduit has a total length of 1.6M and an inner diameter of φ6.8mm,
The outer diameter is 9.0 mm. 46 is a tubular furnace for controlling the temperature of the conduit 32, and 48 is its heat source.

As shown in FIG. 1 (b), the conduits 32 have lengths of 400 mm and 6 mm from the top inside the tubular furnace 46, respectively.
With 3 circuits (A, B, C) of 00mm and 215mm,
The first zone, the second zone (FC zone), and the third zone (GC zone) are configured so that direct electric heating can be performed.

The tubular furnace 46 is also composed of heat sources 46 for three circuits so as to correspond to the above three circuits, and three thermocouples 50 are welded to the conduit at the center of each zone. The temperature can be controlled individually by heating in the temperature range of ° C. That is, the heating corresponding to the three zones of the conduit can be performed only by indirect heating up to 1100 ° C., and above that by direct current heating alone or in combination.

Using this apparatus, the flow rate and viscosity of glass were controlled under various conditions shown in Table 1 below. In Examples 1-1 to 1-4 and Comparative Example 1 below, a photoelectric sensor detects the lower end of the glass flow when the glass flow out flows to a certain position, and works in conjunction with a shear mechanism (not shown). About 20 mm
A long rod-shaped gob was formed. At this time, the time interval between shear timings in which the flow-down speed is continuous is monitored and used as a molding tact. Then, the tubular furnace was energized only in the zone A corresponding to the conduit portion of the first zone, and the temperature near the heat source was controlled so as to be 1000 ° C, and the energization was performed directly 3
Table 1 shows the set temperature and temperature change range for each circuit. The orifice temperature means the monitor temperature of the thermocouple fused near the outlet of the tip of the conduit, and the orifice was burner heated as an auxiliary heating, but in Example 1-3, the heating was stopped. The variation in the orifice temperature is affected by the shear cutting condition (instantaneous temperature change during shear operation, temperature change during lubricant spraying on the shear blade), so measure the change at the time when the glass flow stably flows down. did.

The flow rate is a value obtained for each molding, which is calculated by measuring the weight of a continuously molded gob and calculating the molding tact required to mold the gob. There, the measurement accuracy of the weight is ± 0.03 g, and the mechanical time error of shear timing is included. The glass flow viscosity is shown by calculating the measured value of the radiation thermometer from the temperature-viscosity curve. Since this measurement also varies depending on the shear cutting state, the measurement system was arranged so that it was recorded only at the time of stable flow-down.

Example 1-1 Heavy Crown Glass (SK
(12, made by OHARA CORPORATION) is melted in the crucible 12 for clarification and homogenization, and as shown in Table 1 below, each zone is kept at a constant temperature under standard conditions for about 30 minutes to remove the glass from the conduit 32. When it was made to flow out, the almost constant flow rate and viscosity shown in Table 1 were obtained.

(Example 1-2) As shown in Table 1, when the glass flowed out from the conduit 32 while changing the temperature of the second zone (FC zone), the flow rate of the glass also changed accordingly. The result is shown in FIG. That is, when only the temperature of the second zone (FC zone) is changed from 850 ° C. to 1150 ° C., 1.47 cc / min to 22.88 cc / min.
It can be seen that the desired flow rate can be obtained in a wide range up to the minute. At the same time, the change in viscosity of the glass is ^10.38.
It can also be seen that it is 10 ^2.51 dPa · s from dPa · s.

Example 1-3 As shown in Table 1, when the glass was caused to flow out from the conduit 32 while changing the temperature of the third zone (GC zone), the viscosity of the glass also changed accordingly. The result is shown in FIG. That is, when changing the temperature only 800 ° C. in the third zone (GC zone) to 1150 ° C., adjusted over a wide range the viscosity of the glass to a low viscosity of 10 ^{2. 36} dPa · s from the high viscosity of 10 ^6.55 dPa · s I see that it is possible. At the same time, it is also understood that the flow rate change is from 6.01 cc / min to 13.17 cc / min.

From the above Examples 1-2 and 1-3, in order to adjust and change the flow rate, the second zone (FC zone)
It is possible to adjust the temperature of the conduit part of the glass, the temperature of the conduit part of the third zone (GC zone) including the outflow end for the viscosity of the glass, and to adjust them in a wide range using the same conduit system. I understand.

(Example 1-4) As a continuous molding for a long time, about 13 liters of glass was allowed to flow out for about 27 hours, and stable outflow for a long time was evaluated as follows. The result is shown in FIG. Target flow rate and forming tact is 7.84
cc / min, 4.50 seconds, about 27 hours of continuous molding experiment, temperature control of FC zone and GC zone was performed along the curve as shown in Fig. 4. Even if the surface changes greatly, the glass flow rate change is ± 0.08 cc / min and the viscosity change is 1
It could be stabilized at 0 ^-0.04 to 10 ^+0.04 dPa · s.

In this embodiment, the temperature changes with respect to the conduits of the FC zone and the GC zone are ± 0.5 and ±, respectively.
The temperature was fed back to the temperature controller by communication from the control unit in steps of 1 ° C. In other words, a certain algorithm is used for the calculated temporal change curve of each gob, and the temperature of the FC zone is changed in steps of ± 0.5 ° C.
The temperature change curve of the molding tact measured in units of 0.01 seconds was also calculated by another algorithm, and the temperature of the GC zone was changed in steps of ± 1.0 ° C.

(Comparative Example 1) As a comparative example, the flow rate and the glass viscosity change were measured when the temperatures of the second and third zones were maintained at a constant temperature. The result is shown in FIG.

In this comparative example, as shown in FIG. 5, it was found that the flow rate and the viscosity including the molding tact changed significantly, so that the process was interrupted.

Next, in the case where the glass to be melted is lanthanum glass (LasF010, manufactured by OHARA CORPORATION),
Examples 1-5, 1-6, and Reference Example 1 will be described. (Example 1-5) In accordance with the standard conditions shown in Table 1, Example 1
Same as -1 to 1-4, except that the molding apparatus was a direct press molding of a drain cast system, and a meniscus lens of about 1.7 cc was manufactured with a tact time of 6 seconds. The same conditions were used. Further, in this case, all three zones A, B and C of the tubular furnace were heated. In particular, the temperature of the conduit due to direct electric heating was kept above 1030 ° C because the liquidus temperature of this glass was 1024 ° C.

(Example 1-6) The temperature of the conduits in the first to third zones was set to the same set temperature, and the temperature was changed from 1040 ° C to 1200 ° C.
Molding was performed by changing the temperature to 0 ° C and changing the molding tact according to the outflow amount. As a result, the flow rate is 9.03 ~
It was found that the viscosity could be adjusted in a wide range up to 74.49 cc / min, and the viscosity decreased from 10 ^2.77 to 10 ^1.40 dPa · s. Being able to flow out low viscosity glass at a large flow rate is advantageous because it can improve the productivity in the case of glass molding, especially in the case of casting into a slab-shaped continuous molded body or a round bar, and it is possible to form a glass molded body with a large product weight. It is also preferable when manufacturing by direct pressing by the drain cast method.

Reference Example 1 Further, as a comparative reference of Examples 1-5, an example in which a tubular furnace by indirect heating is not energized in three zones in this case is shown. As a result, the flow rate was gradually decreased, and minute crystal grains of glass were precipitated in the glass molded body, and striae that were thought to be caused by it were found by observing the cross section of the glass. This is the effect of indirect heating. In particular, it was found that the setting temperature of the tubular furnace A was set to 1050 ° C. to suppress the loss of dialysis. That is, tubular furnace A
If you don't heat directly to the furnace, set the furnace temperature to 1
It was clarified that if the temperature was 030 ° C or lower, the temperature near the welded portion of the electrode 2 which was directly energized and heated with the conduit portion was lowered.

[0040]

[Table 1] <Embodiment 2> FIG. 6 shows an embodiment of the apparatus of the present invention.
It is sectional drawing which shows from the refiner part of a continuous melting device to the orifice of an outflow lower part through a conduit. The fluctuation range of the glass liquid level G in the crucible 12 of the refiner in the furnace 16 is ±
The raw material charging system is operated so that it is within 2 mm. The stirring for homogenization is always performed on the side surface of the rotary shaft 40 by the helical blades 38 for two turns. 2 conduits
There are various types of drain conduit 31 with an inner diameter of 15 mm and a total length of 5
It is attached to the center of the bottom of the refiner at 50 mm, is bent downward, and is then attached at an angle to the outside of the furnace.

The length between the electrodes 6 and 7 is 450 mm.
The electric heating of the conduit 31 is performed only when the bottom seed of the molten glass is discharged, and is maintained in the non-energized state during the normal production of the same glass. The conduit 32 is connected to the corner of the lower part of the side wall of the refiner and, like the part 31, extends through the lower part of the side wall of the furnace 16 to the outside of the furnace. The tip is a glass outflow orifice. The conduit 32 has a total length of 2.0 M, an inner diameter of 10.0 mm, and an outer diameter of 12.0 mm. The electrodes for direct energization are indicated by 1 to 5, and the distances between the electrodes are 440, 850, 300, and 255 mm, and are composed of four circuits. The position of the electrode 2 is 30 m from the end 16a of the melting furnace.
It is at a distance of m. The temperature control of the conduit portion in each of these zones is performed by the thermocouple 50 welded to the substantially central portion of the electrodes. Further, a total of 24 thermocouples for monitoring are attached to each position as shown in FIG. 7A so that the temperature distribution of the whole thermocouple can be measured. The conduit length design can be freely extended to connect the equipment of the melting device and the molding machine,
It may reach 5 to 10 m. Further, the minimum required conduit length is determined by the conduit inner diameter, the glass flow train, the difference between the temperature of the molten glass of the refiner and the glass temperature at the outflow end, and the like. In this embodiment, the inner diameter of the conduit is 10 mm and the maximum flow rate is 1
It was set to 2 M based on 00 cc / min. If the inner diameter of the conduit is further increased and the flow rate is increased, it is necessary to further increase the length of the conduit. The design criterion is in the heat transfer calculation of whether the temperature in the glass flow reaches close to the temperature setting of the conduit. The electrodes 1 to 4 have the same shape as shown in FIG. 8, and have a width of 40 mm and a thickness of 1.5 mm.

The shapes of the electrode 5 and the orifice are shown in FIG.
Shown in. The material of this orifice is a Pt alloy of 5% Au and the glass is hard to slip at the tip of the orifice, and is welded to the pipe of the platinum conduit 32. With respect to the conduit having the inner diameter φ10, the sleeve 9 on the outside and the connecting portion 8 with the conduit are designed so that electricity is supplied from the lead portion to the conduit through these. This allows the tip of the orifice to be sufficiently heated, and a heat insulating material is attached to the gap between the conduit and the sleeve 9 and the outer circumference of the sleeve. Since this apparatus does not use indirect heating as in Example 1, the entire conduit is sufficiently heat-insulated. That is 1
A 2.5 mm-thick ceramic blanket and a silica tape were evenly wound in a spiral shape to further sufficiently maintain heat insulation in the vicinity of the electrode portion. The electricity is supplied to each electrode by fixing the platinum lead plate shown in FIG. 8 with a brass water-cooled jacketed holder. At that time, the point to be noted is that the distance between the conduit portion and the holder, that is, the lead length is required to be 50 mm or more. This length strongly affects the temperature near the electrode mounting portion of the conduit. That is, a temperature difference between the water cooling holder and the conduit temperature is generated in the lead portion, and the temperature gradient affects the conduit temperature near the electrode portion. In this embodiment, the lead length is 100 mm. The drain conduit 31 was also treated in the same manner, but the drain process will not be described below because it is not related to the present invention.

Although the temperature control of the furnace is not shown, it is omitted because it is the same as that of the first embodiment. However, the energization method was such that the primary side power supply was 200 V three-phase alternating current and the secondary side energization was also three-phase alternating current. Direct energization heating in 4 zones of the conduit is performed by using a low voltage insulating transformer that can be set to switch from 1V to 1V in 1V increments, and is supplied to each circuit using a three-phase power source of R, S, and T. The phase of electricity is R between the electrodes
S, ST, TR. The circuit configuration is such that six types can be switched so that SR, TS, and RT can be selected. (Example 2-1) Having a chemical composition different from that of Example 1,
A low-viscosity heavy crown glass (BAL62, manufactured by OHARA CORPORATION) was continuously melted, and the glass was discharged from a conduit. In this Example 2-1, the conditions shown in Table 2 were used as standard conditions,
A glass gob of about 1 cc was continuously produced in a 3-second tact by adopting a molding method of receiving the glass gob with a mold by cutting the flowing glass without using a shear mechanism. It should be noted that this type of shearless gob molding can be performed with a glass having a low viscosity of 10 ^2.5 dPa · s or less. Since it is a continuous melting method with very little fluctuation of the glass liquid level, fluctuations in the flow rate are due to fluctuations in the glass liquid level and fluctuations in the control temperature within ± 0.2 ° C of the conduit section, with good results of 0.02 cc / min Has become.

Next, in the experiments of Examples 2-2 to 2-4, not the production of the above-mentioned gobs but the operation of the shear was performed to measure the outflow amount at every predetermined time.

(Example 2-2) As shown in Table 2, when the glass was caused to flow out from the conduit 32 while changing the temperature of the second zone (FC zone), the flow rate of the glass also changed accordingly. The result is shown in FIG. That is, when the temperature of the second zone (FC zone) was changed from 810 ° C to 1100 ° C, the flow rate was 2.96 to 75.66 cc /
It can be adjusted within a wide range of about 25 times. Here, since the viscosity of the glass flow only slightly changes from 10 ^2.42 to 10 ^2.24 dPa · s, it is understood that the weight of the gob can be easily controlled by the same molding method and molding conditions.

Example 2-3 As shown in Table 2, when the glass was caused to flow out from the conduit 32 while changing the temperature of the fourth zone (GC zone), the flow rate of the glass also changed accordingly. The result is shown in FIG. That is, when the temperature of the fourth zone (GC zone) is changed from 840 ° C to 1140 ° C, conversely, the flow rate is 17.43 to 22.04.
However, the viscosity of glass is 10 ^3.06.
It is clear that the range of change is as large as -10 ^1.67 dPa · s, and that the viscosity of the glass can be adjusted by not changing the temperature of the GC zone only and not significantly affecting the flow rate.

Comparing Example 1-2 and Example 2-2, the viscosity change width decreased from 26% to 7% by the temperature change of 300 ° C., and Example 1-3 and Example 2-3 were compared. Then, similarly, the variation of flow rate decreased from 48% to 21%.
It can be seen that the flow rate in the zone and the GC zone and the selectivity for controlling viscosity are improved. This is F in Examples 2-2 and 2-3.
This is because there is a third zone between the C zone and the GC zone. That is, when the FC zone and the GC zone are adjacent to each other, if the temperature setting of one zone is changed, the temperature distribution of the conduit tends to affect the adjacent zone.

Further, in order to obtain a good result, it is considered to use two or more circuits in the intermediate zone or to change the temperature of the intermediate zone to further reduce the temperature interference between the FC zone and the GC zone. To be In the latter case, for example, the temperature setting of the intermediate zone can be set to an intermediate value between the temperatures of the FC zone and the GC zone.

(Example 2-4) When the temperatures of the FC zone and the GC zone were changed and the temperature of the conduit portion of the third zone (intermediate zone) was set to the middle thereof, the temperature of the intermediate zone was changed. In terms of selectivity, the variation range of viscosity in the FC zone was reduced to 4% and the variation range of flow rate in the GC zone was reduced to 13%. FIG. 12 shows the range in which the glass having this chemical composition can be stably discharged in the conduit system used in this example. As shown in this figure, it can be seen that the glass can flow out in a wide range of flow rates and viscosities.

In FIG. 12, the two cross-shaped curves located at the center are the standard curves at 960 ° C. and the vertical curve is the second curve.
It is the relationship between the flow rate and the viscosity when the zone temperature is changed from 810 ° C to 1100 ° C and the temperature of the third zone is changed from 885 ° C to 1030 ° C accordingly, and the horizontal curve is the temperature of the fourth zone. From 840 ° C to 1140 ° C,
The relationship between the flow rate and the viscosity when the temperature of the third zone is changed from 900 ° C to 1050 ° C is shown. For the allowable upper and lower temperature limits of the conduit system, foam re-emergence occurs at temperatures above 1150 ° C. in some of the conduits. In this, the bubble re-generation temperature changes depending on the viscosity of the glass and the type of the fining agent. Generally, it is said that the fining agent redox reaction in glass is initiated by re-heating to generate O ₂ bubbles, which is the upper limit temperature when the glass flows out through a conduit. The lower limit temperature is that the glass flow stops.

Further, in this embodiment, when the temperature in the second to fourth zones was set to 800 ° C. or lower, it was found that the glass flow stopped after a few minutes even if the gas was heated at the tip of the orifice. There is. Within this flow rate and viscosity range, their long-term stability can be secured to the same extent as in Example 2-1. For example, flow rate is 10 cc / min Glass viscosity is 1
The conduit temperature is set to 861 ° C in the FC zone, 1022 ° C in the GC zone, and 941.5 ° C in the middle zone so that the pressure becomes 0 ^2.0 dPa · s, and 0.50 cc in continuous 24 hours 3.0 seconds tact. Molded gobs. As a result, the weight variation was within 0.5%, which was good. In this case, the FC zone is a constant value control within a fluctuation range of ± 0.2 ° C, and the temperature setting of the GC zone is controlled in increments / decrements of ± 1 ° C in accordance with the change of the measurement value of the radiation thermometer. Therefore, if measures such as further reducing the liquid level fluctuation range and further decreasing the set temperature increase / decrease temperature in the GC zone are taken, it is expected that the gob weight fluctuation for a longer time will become smaller.

(Embodiment 2-5) Next, the setting of the phase of the AC power source with respect to the direct conduction system of the conduit will be described. 2-
In the example of 5, the experiment was conducted under the standard conditions of 2-1 and mainly in FIG.
The temperature distribution of the conduit system was examined as the measurement result by the thermocouple in (a). 2-5-1 and 2-2 of the embodiment of FIG.
No. 5-4. 1-No. The RST combination of the secondary side AC three-phase power source was tested for the circuit of zone 4. Among them, 2-5-2 and 2-5-3 are R-
Since only the S phase is used, this means that the phase of the AC single-phase power supply is changed in each circuit. The measured temperature is plotted against the distance from the refiner in FIG. 7- (b) with each experimental result as a temperature distribution.

A characteristic is 2-5-3, in which the temperature in the vicinity of the electrode is 10 at maximum when the respective circuits are energized in the same direction and in the same phase.
When the temperature is lowered by 0 ° C. or more, and when the reverse phase is energized in the circuit order in 2-5-2, the temperature in the vicinity of the electrode portion tends to be high. When the combination of RST is sequentially changed like 2-5-1, the intermediate temperature is shown. In consideration of these points, 2-5-4 is adjusted by changing the phase for each circuit so that the temperature distribution of the conduit system is as uniform as possible. As a result, the temperature distribution within ± 10 ° C I was able to put it in. The change in the temperature distribution near the electrode part due to the phase change is that the current value in the part from the platinum lead part to the connection part to the conduit is a phase composite of the currents flowing to the adjacent circuits, and at the frequency of 50 Hz, Understand that there is an impact.

The fact that the temperature distribution in the vicinity of the electrode portion can be made uniform by the combination of the energization phases is the same as in Examples 1-5 to 1-
It is also convenient for flowing out a glass having a strong devitrification tendency as shown in 6 and a glass having a higher liquidus temperature, and it is also advantageous that indirect heating is not necessary. In addition, when the flow rate is increased and the viscosity is low, the temperature of the reboil is limited, but overheating in the vicinity of the electrode can be suppressed, so that the conduit temperature can be set close to that temperature. Become. Further, when the difference between the temperature in the vicinity of the electrode portion and the circuit control temperature exceeds 100 ° C. as in Example 2-5-3,
Striae quality deteriorates in the conduit system. Therefore, it is necessary to avoid local supercooling and overheating in the conduit system.

Further, the improvement of the temperature distribution in the vicinity of the electrode portion by adjusting the phase of the circuit is effective when the shape of the entire conduit, for example, the diameter of the conduit is partially increased or decreased in the middle zone or the final zone. is there. That is, if a taper tube used for a connecting portion of conduits having different inner diameters is placed near the electrode portion, a steep temperature distribution generated in response to a change in the heat generation amount of the taper tube can be relaxed.

[0056]

[Table 2] Although the conduit systems of Embodiments 1 and 2 described above are installed obliquely downward from the lower part of the side wall of the refiner, the present invention is not limited to this and may be arranged vertically from the bottom of the refiner.

The pipes used are all pipes, but the pipes are not limited to circular pipes, and in particular, the shape of the outflowing orifice may be angular or elliptical. The thickness is about 1 mm, but it may be thicker. Regarding the tip diameter of the orifice, a converter for changing the diameter or the opening shape may be attached to the orifice portion. In that case, since supercooling is likely to occur at the tip of the orifice, it is important to use an auxiliary power source such as burner heating or lamp heating.

Further, although the control point is arranged approximately in the center of the zone to be energized, the temperature may be adjusted by moving it to a point near the electrode portion of that zone, but a particularly good effect is not obtained. .

[0059]

As described above, according to the glass flow rate control method of the present invention, the following effects can be obtained.

(1) It is sufficient to control the temperature of the conduit portion of a specific zone in response to the flow rate fluctuation caused by the change of the liquid level of the glass of the refiner and the change of the manufacturing environment, and the viscosity of the glass flowing out is affected. It can be stabilized at 1% or less, and even 0.5% or less for a long time.

(2) For fluctuations in the viscosity of the glass during continuous molding for a long time, the temperature of the conduit portion in the final zone of the outlet end of the conduit may be controlled so that the flow rate is stable and stable. Can be leaked to.

(3) The temperature of the conduit portions in different zones of the conduit can be independently controlled to adjust the flow rate and viscosity of the glass. From the examples, the flow rate is several to several hundred cc / min, about 20 times, and the viscosity is 10 ^1. Since it can be adjusted within the range of -10 ⁷ dPa · s, it can be used for various molding methods and molding devices by using the same conduit, and the degree of freedom of the product is great.

(4) The temperature of the conduit portion can be changed with good responsiveness, the time loss when switching products can be reduced, and the productivity is good.

(5) Since the temperature distribution of the entire conduit including uncontrolled electrode parts can be adjusted, devitrification and bubbles are not generated and the gob or the glass flow is stabilized inside the conduit without deteriorating the quality of the glass. Can be supplied.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an apparatus for flowing out glass from a one-pot type crucible in Example 1 using a conduit.

FIG. 2 is a diagram of change curves of flow rate and viscosity with respect to conduit temperature showing the results of Example 1-2.

FIG. 3 is a diagram of change curves of flow rate and viscosity with respect to conduit temperature showing the results of Example 1-3.

FIG. 4 shows F with respect to outflow time showing the results of Examples 1-4.
It is a figure of the temperature change of C and GC zone, and the change curve of the flow volume and viscosity with respect to it.

FIG. 5 is a diagram showing temperature changes in the FC and GC zones with respect to the outflow time and the change curves of the flow rate and the viscosity with respect to them, showing the results of Comparative Example 1.

FIG. 6 is a schematic cross-sectional view of an apparatus after the refiner of the continuous glass melting apparatus in Example 2.

7 (a) is a layout diagram of thermocouples for measuring the temperature distribution of a 2M-long conduit in Example 2, and FIG. 7 (b) is a diagram showing the conduction phase and the resulting temperature distribution of the conduit. .

FIG. 8 is a diagram showing a shape of an electrode portion according to the second embodiment.

FIG. 9 is a diagram showing the shape of an orifice portion in the second embodiment.

FIG. 10 is a diagram showing change curves of flow rate and viscosity with respect to conduit temperature, showing the results of Example 2-2.

FIG. 11 is a diagram of change curves of flow rate and viscosity with respect to conduit temperature showing the results of Example 2-3.

FIG. 12 is a diagram showing a flow rate and viscosity region that can flow out using a conduit system showing the results of Example 2-4.

[Explanation of symbols]

 1-7 Electrodes for direct energization 12 Refiner or crucible 16 Furnace 31,32 Conduit 38 Stirring blade 44,50 Thermocouple 46 Indirect heating furnace 48 Heat source G Glass level

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mizukazu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (10)

[Claims] 1. A glass flow rate control method for adjusting the flow rate of molten glass flowing out of a melting furnace from a melting furnace to the outside of the furnace by a temperature control area for controlling the flow rate of the conduit. A method for controlling the flow rate of glass, which further comprises controlling the viscosity of the molten glass by changing the temperature of a further downstream area. 2. The area of the conduit for temperature control for viscosity control is the area containing the glass outflow end of the conduit.
A flow rate control method for the glass described. 3. An area for temperature control for controlling flow rate and an area for temperature control for controlling viscosity are not in contact with each other.
Alternatively, the method of controlling the glass flow rate according to the item 2. 4. A single-phase or three-phase alternating current is applied to a conduit to heat at least a temperature adjusting region for flow rate control and a temperature adjusting region for viscosity control, and each electrode in an adjacent region is heated. The flow rate control method for glass according to any one of claims 1 to 3, wherein the temperature is adjusted by adjusting a combination of electrical phases. 5. An area for temperature control for controlling the flow rate is located within a range of 0 to 1,500 mm from the end of the melting furnace, and an area for temperature control for controlling clay is 0 to the outlet of the conduit.
The glass flow rate control method according to any one of claims 1 to 4, wherein the glass flow rate control method is provided in an area separated by 500 mm. 6. A glass outflow device for adjusting the flow rate of molten glass flowing out of a melting furnace through a conduit to the outside of the furnace, comprising a temperature adjusting means for controlling the flow rate of the conduit. A glass outflow device further comprising a region provided with a means for controlling the viscosity of molten glass by a temperature change, further downstream than the region. 7. The area of the conduit for temperature control for viscosity control is the area containing the glass outflow end of the conduit.
Glass outflow device as described. 8. An area for adjusting temperature for controlling flow rate and an area for adjusting temperature for controlling viscosity are not in contact with each other.
Or the glass outflow device according to 6. 9. A single-phase or three-phase alternating current is applied to a conduit to heat at least a temperature adjusting area for flow rate control and a temperature adjusting area for viscosity control, and each electrode in an adjacent area is heated. The glass outflow device according to claim 5, wherein the temperature is adjusted by adjusting a combination of electric phases. 10. An area for temperature control for controlling the flow rate is in an area 0 to 1,500 mm away from the end of the melting furnace.
There is no temperature control area for clay control from the outlet of the conduit.
The glass outflow device according to any one of claims 6 to 9, which is located in an area separated by about 500 mm.