Manufacturing method for glass articles

Abstract

We provide technology to suppress devitrification of molten glass. [Solution] The manufacturing method involves, before performing the repair, upstream of the location where the pre-repair will be performed, using a viscosity of 1.0 × 10 4 The method involves lowering the temperature of the molten glass from a temperature higher than the temperature corresponding to dPa·s to a temperature lower than that. The manufacturing method also involves changing the molten glass held in the melting furnace from a first glass to a second glass before lowering the temperature of the molten glass. The first glass has a viscosity of 1.0 × 10⁻⁶ 4 dPa·s ~1.0 × 10 7 The maximum crystal growth rate in the temperature range corresponding to dPa·s is 50 μm / hr or more. The second glass has a viscosity of 1.0 × 10 4 dPa·s ~1.0 × 10 7 The maximum crystal growth rate in the temperature range corresponding to dPa·s is 40 μm / hr or less.

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing glass articles. [Background technology]

[0002] The method for manufacturing glass articles described in Patent Document 1 includes a replacement step in which a transfer device is replaced while molten glass is held in the melting furnace. In the replacement step, between the time the transfer device is attached to the melting furnace and the start of the molding step, molten glass is allowed to flow from the melting furnace into the transfer device while the molten glass is discharged from the transfer device to the outside. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-007174 [Overview of the project] [Problems that the invention aims to solve]

[0004] While the melting furnace holds the molten glass, repairs may be carried out on the flow path of the molten glass downstream of the melting furnace. In such cases, before carrying out the repairs, it is advisable to lower the temperature of the molten glass upstream of the repair site, preferably by freezing the molten glass.

[0005] However, lowering the temperature of molten glass can cause it to devitrify. Devitrification of molten glass is a phenomenon in which crystal grains precipitate from the molten glass, and the grain boundaries of the crystals scatter light, making the glass opaque. The melting point of the crystals is high, and the precipitation of crystal grains prevents the glass from remelting.

[0006] One embodiment of the present disclosure provides a technology for suppressing devitrification of molten glass. [Means for solving the problem]

[0007] A method for manufacturing a glass article according to one embodiment of the present disclosure comprises: heating glass raw materials inside a melting furnace to produce molten glass; transferring the molten glass from the melting furnace to a molding apparatus using a transfer device; and molding the molten glass into a predetermined shape in the molding apparatus. The manufacturing method comprises repairing the flow path of the molten glass downstream of the melting furnace while the melting furnace is holding the molten glass. The manufacturing method comprises, before performing the repair, a viscosity of 1.0 × 10⁻¹⁰ 4 The method comprises lowering the temperature of the molten glass from a temperature higher than the temperature corresponding to dPa·s to a temperature lower than that. The manufacturing method comprises changing the molten glass held in the melting furnace from the first glass to the second glass before lowering the temperature of the molten glass. The first glass has a viscosity of 1.0 × 10 4 dPa·s ~1.0 × 10 7 The maximum crystal growth rate in the temperature range corresponding to dPa·s is 50 μm / hr or more. The second glass has a viscosity of 1.0 × 10 4 dPa·s ~1.0 × 10 7 The maximum crystal growth rate in the temperature range corresponding to dPa·s is 40 μm / hr or less. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, the molten glass held in the melting furnace is changed from the first glass to the second glass before the temperature of the molten glass is reduced. This makes it possible to suppress devitrification of the molten glass. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a flowchart showing a method for manufacturing a glass article according to one embodiment. [Figure 2] Figure 2 is a cross-sectional view showing a glass article manufacturing apparatus according to one embodiment. [Figure 3] Figure 3 is a flowchart showing an example of the process for repairing a transfer device. [Figure 4]FIG. 4 is a cross-sectional view showing an example of S202 in FIG. 3. [Figure 5] FIG. 5 is a cross-sectional view showing an example of S203 in FIG. 3. [Figure 6] FIG. 6 is a cross-sectional view showing an example of S204 to S205 in FIG. 3. [Figure 7] FIG. 7 is a cross-sectional view showing an example of a process for repairing a molding apparatus. [Figure 8] FIG. 8 is a diagram showing an example of the relationship between the viscosities and crystal growth rates of glass A and glass B. [Figure 9] FIG. 9 is a cross-sectional view showing an example of a glass manufacturing apparatus. [Figure 10] FIG. 10 is a cross-sectional view taken along the X-X line in FIG. 9. [Figure 11] FIG. 11 is a cross-sectional view taken along the XI-XI line in FIG. 9.

MODE FOR CARRYING OUT THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or similar configurations are denoted by the same reference numerals, and the description thereof may be omitted. In each drawing, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other, the X-axis direction and the Y-axis direction are horizontal directions, and the Z-axis direction is a vertical direction.

[0011] The X-axis direction includes the positive X-axis direction and the negative X-axis direction, which is opposite to the positive X-axis direction. The positive X-axis direction is the flow direction of the molten glass G. The positive X-axis direction is the downstream side, and the negative X-axis direction is the upstream side. The Y-axis direction includes the positive Y-axis direction and the negative Y-axis direction, which is opposite to the positive Y-axis direction. The Z-axis direction includes the positive Z-axis direction and the negative Z-axis direction, which is opposite to the positive Z-axis direction.

[0012] In the specification, "~" indicating a numerical range means including the numerical values described before and after it as the lower limit value and the upper limit value. The numerical range includes the rounded range.

[0013] First, a flowchart illustrating a method for manufacturing a glass article according to one embodiment will be described with reference to Figures 1 and 2. The manufacturing method includes steps S101 to S103 shown in Figure 1. Note that the manufacturing method may also include steps not shown in Figure 1.

[0014] Step S101 involves heating the glass raw material inside the melting furnace 10 to produce molten glass G. The glass raw material is prepared by mixing several types of materials. The glass raw material may contain a clarifying agent. The glass raw material may contain glass cullet in order to recycle the glass. The glass raw material may be a powdered raw material or a granulated raw material obtained by granulating the powdered raw material.

[0015] The glass raw materials are determined according to the glass composition. Examples of glass include alkali-free glass, aluminosilicate glass, borosilicate glass, or soda-lime glass. Alkali-free glass means glass that does not substantially contain alkali metal oxides such as Na2O and K2O. Here, substantially free of alkali metal oxides means that the total amount of alkali metal oxides contained is 0.1% by mass or less.

[0016] The heating device 11 heats the glass raw material inside the melting furnace 10 to produce molten glass G. The heating device 11 has, for example, multiple electrodes (only one is shown in Figure 2). The multiple electrodes apply a voltage to the molten glass G and pass an electric current through the molten glass G, thereby generating Joule heat in the molten glass G. In this case, the molten glass G generates heat.

[0017] The heating device 11 may have a burner (not shown). The burner forms a flame above the molten glass G. The radiant heat from the flame heats the molten glass G and the glass raw material floating on the surface of the molten glass G. The glass raw material is introduced from above onto the surface of the molten glass G and gradually melts into the molten glass G.

[0018] The heating device 11 may have an electric heater (not shown). The electric heater includes a resistive heating element. By applying a voltage across the resistive heating element and passing a current through it, Joule heat can be generated in the resistive heating element. The resistive heating element generates heat, not the molten glass G. The electric heater may include a protective cover to prevent contact between the resistive heating element and the molten glass G.

[0019] Step S102 involves transferring the molten glass G from the melting furnace 10 to the molding apparatus 30 using a transfer device 20. The transfer device 20 is not particularly limited, but may include a plurality of movable units 21A to 21C. The plurality of movable units 21A to 21C are independently movable upstream and downstream.

[0020] As shown in Figure 6, a gap is formed between the melting furnace 10 and the upstream movable unit 21A during the heating process. Also, a gap is formed between adjacent movable units 21A to 21C during the heating process. Since molten glass G is not transferred during the heating process, even if the gap is large, molten glass G will not leak out. The gap prevents interference between devices and prevents damage to the devices.

[0021] As shown in Figure 2, after the heating process is complete and before the manufacture of the glass articles begins, the gap between the melting furnace 10 and the upstream movable unit 21A is narrowed to the extent that the molten glass G does not leak out. Similarly, the gaps between adjacent movable units 21A to 21C are narrowed. These gaps may be eliminated as a result of the narrowing. Alternatively, some gaps may remain to the extent that the molten glass G does not leak out.

[0022] Each movable unit 21A to 21C may have, in this order from upstream to downstream, a first horizontal pipe 22A to 22C, a vertical pipe 23A to 23C, and a second horizontal pipe 24A to 24C. The central vertical pipes 23A to 23C may be fitted with stirring blades for an agitator (described later), or an ascending or descending pipe for a clarification device.

[0023] A stirring device (not shown) may be provided in the middle of the transfer device 20. The stirring device uses stirring blades to agitate the molten glass G and homogenize it. Additionally, a clarification device (not shown) may be provided in the middle of the transfer device 20. The clarification device removes air bubbles contained in the molten glass G.

[0024] The first horizontal tubes 22A-22C, the vertical tubes 23A-23C, and the second horizontal tubes 24A-24C may be formed from a metal such as platinum (Pt). Besides platinum, rhodium (Rh), tungsten (W), iridium (Ir), or molybdenum (Mo) can also be used. The metals may include alloys.

[0025] The first horizontal tubes 22A-22C, vertical tubes 23A-23C, and second horizontal tubes 24A-24C, when made of metal, can be used as resistance heating elements and can be heated by electric current. The first horizontal tubes 22A-22C, vertical tubes 23A-23C, and second horizontal tubes 24A-24C can be used as heating devices. This can suppress the temperature drop of the molten glass G during transport.

[0026] Each movable unit 21A to 21C may have an insulating material 25A to 25C. The insulating material 25A to 25C covers the first horizontal pipes 22A to 22C, the vertical pipes 23A to 23C, and the second horizontal pipes 24A to 24C, suppressing heat loss. The insulating material 25A to 25C is made of brick or the like. Each movable unit 21A to 21C may have casters or irregularly shaped materials.

[0027] Step S103 involves forming the molten glass G into a predetermined shape using the molding apparatus 30. Examples of molding methods for obtaining plate-shaped glass include the float method, the fusion method, or the roll-out method. Examples of molding methods for obtaining tubular-shaped glass include the bellows method or the Danner method.

[0028] Next, referring to FIGS. 3 to 6, an example of the process of repairing the transfer device 20 will be described. The repair method has steps S201 to S206 shown in FIG. 3. Note that the repair method does not necessarily have all of steps S201 to S206 shown in FIG. 3. Also, the repair method may have steps not shown in FIG. 3.

[0029] Step S201 involves changing the molten glass G held by the melting furnace 10 from the first glass to the second glass. The first glass has a maximum crystal growth rate V1max of 50 μm / hr or more in the temperature range corresponding to a viscosity of 1.0×10 4 dPa·s to 1.0×10 7 dPa·s.

[0030] The temperature range corresponding to a viscosity of 1.0×10 4 dPa·s to 1.0×10 7 dPa·s is hereinafter simply referred to as the "devitrification temperature range". When the molten glass G passes through the devitrification temperature range, if the maximum value of the crystal growth rate is 50 μm / hr or more, devitrification of the molten glass G is likely to occur. Therefore, in this embodiment, the molten glass G is changed before the temperature of the molten glass G decreases (step S202).

[0031] The change of the molten glass G is performed by changing the glass raw material. By changing the glass raw material, the molten glass G can be gradually changed. In order to shorten the time required for changing the molten glass G, a part of the molten glass G accumulated inside the melting furnace 10 may be discharged before changing the glass raw material. The change of the molten glass G is performed by a general method. The change of the molten glass G is performed while the melting furnace 10 holds the molten glass G at a temperature higher than the temperature corresponding to a viscosity of 1.0×10 4 dPa·s.

[0032] The second glass has a maximum crystal growth rate V2max of 40 μm / hr or less in the devitrification temperature range. When the molten glass G passes through the devitrification temperature range, if the maximum value of the crystal growth rate is 40 μm / hr or less, devitrification of the molten glass G hardly occurs. Also, even if devitrification occurs, the crystal grain size is small.

[0033] The V2max of the second glass should be 40 μm / hr or less, but is preferably 35 μm / hr or less, and more preferably 30 μm / hr or less. From the viewpoint of devitrification, a smaller V2max of the second glass is preferable, but from the viewpoint of feasibility, it may be 10 μm / hr or more.

[0034] On the other hand, the V1max of the first glass should be 50 μm / hr or higher, but is preferably 55 μm / hr or higher, and more preferably 60 μm / hr or higher. From the viewpoint of obtaining the effect of compositional modification, a higher V1max of the first glass is preferable, but from the viewpoint of feasibility, it may be 100 μm / hr or lower.

[0035] The combination of the first and second glasses is not particularly limited, but for example, the combination of glass A and glass B shown in Table 1 is possible. Glass A is an example of the first glass, and glass B is an example of the second glass. The compositions of glass A and glass B are shown in Table 1.

[0036] [Table 1]

[0037] Figure 8 shows an example of the relationship between viscosity and crystal growth rate for glass A and glass B, as shown in Table 1. In Figure 8, η is viscosity (unit: dPa·s). The maximum crystal growth rate for glass A in the devitrification temperature range was 50 μm / hr or higher. On the other hand, the maximum crystal growth rate for glass B in the devitrification temperature range was 40 μm / hr or lower.

[0038] In this specification, the crystal growth rate is measured by the following procedure (1) to (6): (1) Prepare glass of the desired composition. (2) Heat the prepared glass at a first temperature T1 for 17 hours to precipitate the primary crystal. (3) Cool the glass heated at the first temperature to room temperature and measure the average grain size of the primary crystal. (4) Heat the glass at a second temperature T2 for 1 hour to grow the crystal. (5) Cool the glass heated at the second temperature T2 to room temperature and measure the average grain size of the crystal. (6) The difference between the average grain size of the crystal measured in (5) and the average grain size of the primary crystal measured in (3) is adopted as the crystal growth rate at the second temperature T2 (unit: μm / hr). The first temperature T1 is set by the following method. The average grain size is the average value of the maximum Ferret diameter of each crystal when the cross-section of the glass is observed with an optical microscope.

[0039] The method for setting the first temperature T1 is as follows: First, the viscosity is 1.0 × 10 4 The heating temperature is lowered in 10°C increments, starting from a temperature corresponding to dPa·s. After heating the glass for 17 hours at each temperature, the glass is cooled, and it is investigated whether crystals have precipitated on the surface of the glass. The highest heating temperature at which crystals precipitate on the surface of the glass is set as the first temperature T1. At temperatures higher than the first temperature T1, no crystals precipitate on the surface of the glass. The second temperature T2 is set at a viscosity of 1.0 × 10⁻⁶. 4 dPa·s ~1.0 × 10 7 The temperature range corresponding to dPa·s is set in 20°C increments.

[0040] Step S202 is performed before carrying out the repair (step S203), by setting the viscosity to 1.0 × 10 upstream of the repair site. 4 The method involves lowering the temperature of the molten glass G from a temperature higher than the temperature corresponding to dPa·s to a temperature lower than that corresponding to dPa·s. The temperature of the molten glass G corresponds to a viscosity of 1.0 × 10⁻⁶. 7 The temperature may be reduced to a temperature lower than the temperature corresponding to dPa·s. Since the molten glass G has been changed from the first glass to the second glass in step S201, devitrification can be suppressed.

[0041] The decrease in the temperature of the molten glass G (step S202) reduces the amount of heat flowing into the repair area (step S203) along with the molten glass G, making the repair easier to carry out. The decrease in the temperature of the molten glass G occurs when the melting furnace 10 has a viscosity of 1.0 × 10⁻⁶. 4 The procedure is carried out while maintaining molten glass G at a temperature higher than the temperature corresponding to dPa·s.

[0042] The temperature decrease of the molten glass G (step S202) preferably includes the freezing of the molten glass G. In Figure 4, GA is frozen glass. Frozen glass GA is molten glass G that has been frozen. Frozen glass GA prevents the flow of molten glass G into the repair site and can reduce the amount of heat flowing in with the molten glass G to zero.

[0043] The freezing of the molten glass G is not particularly limited, but it is preferably performed, for example, at the outlet 10a of the melting furnace 10. This makes it easier to repair the transfer device 20 or the molding device 30. When repairing the molding device 30, the freezing of the molten glass G may be performed at the outlet of the transfer device 20, as shown in Figure 7.

[0044] Freezing of the molten glass G is performed, for example, by closing the inlet of the molding apparatus 30 and limiting the heating of the molten glass G in the transfer apparatus 20. Limiting heating includes stopping the heating. As shown in Figure 4, the molten glass G can be frozen in the transfer apparatus 20 and then frozen at the outlet 10a of the melting furnace 10.

[0045] As shown in Figure 4, the molten glass G may be frozen at the outlet 10a of the melting furnace 10, and the molten glass G may be discharged from the inside of the melting furnace 10 to the outside upstream of the outlet 10a. By discharging the molten glass G, new glass raw materials can be introduced into the melting furnace 10, and a flow of molten glass G can be formed inside the melting furnace 10. This suppresses the stagnation of molten glass G and reduces the effects of volatilization of volatile components (e.g., changes in glass composition).

[0046] It is also possible to avoid discharging the molten glass G. In that case, the input of new glass raw materials will be suspended.

[0047] The molten glass G may be frozen at the outlet 10a of the melting furnace 10, and the amount of heat from the heating device 11 may be adjusted. The heating device 11 maintains the molten glass G in a molten state inside the melting furnace 10, except at the outlet 10a of the melting furnace 10. This state is maintained when the temperature of the molten glass G is equal to a viscosity of 1.0 × 10⁻⁶. 4 This is a state where the temperature is higher than that corresponding to dPa·s.

[0048] It is preferable for the heating device 11 to maintain the molten glass G in a molten state near the electrodes that constitute the heating device 11. If the molten glass G freezes near the electrodes, the frozen glass GA has a higher electrical resistance than the molten glass G, making it difficult for the electrodes to remelt the frozen glass GA near the electrodes.

[0049] Step S203, as shown in Figure 5, involves repairing the flow path of the molten glass G downstream of the melting furnace 10 while the melting furnace 10 is holding the molten glass G. The repair includes replacement. Note that the repair may be a maintenance rather than replacement. In this embodiment, the object to be repaired is the transfer device 20, but it may be the molding device 30, the stirring device, or the clarification device.

[0050] If the melting furnace 10 is holding molten glass G, then, for example, if the heating device 11 includes electrodes, the electrodes will not be exposed to the atmosphere. Therefore, the electrodes will not oxidize and wear down. Repair is performed when the melting furnace 10 has a viscosity of 1.0 × 10 4 The process is carried out while maintaining molten glass G at a temperature higher than the temperature corresponding to dPa·s. The outlet 10a of the melting furnace 10 may be blocked with frozen glass GA.

[0051] During repair (step S203), a cooling device 12 may be installed at the outlet 10a of the melting furnace 10. The cooling device 12 prevents the frozen glass GA from remelting and prevents molten glass G from leaking out of the outlet 10a. The cooling device 12 includes, for example, a nozzle that blows a gas such as air towards the outlet 10a, or a cooler through which a refrigerant flows. The refrigerant may be, for example, water or oil.

[0052] Step S204 involves packing the replaced transfer device 20 with glass cullet GB, as shown in Figure 6. The glass cullet GB may be packed into the upstream part of the transfer device 20, but not into all parts. For example, the glass cullet GB may be packed into the upstream movable unit 21A. The glass cullet GB is not particularly limited, but it is preferably a second glass.

[0053] Step S205 involves lowering the temperature of the molten glass G in a location where the temperature of the molten glass G has been previously reduced (for example, the outlet 10a of the melting furnace 10 and the transfer device 20) to a viscosity of 1.0 × 10 4 This involves raising the temperature to a level higher than the temperature corresponding to dPa·s. Since the molten glass G is the second glass and not the first glass, the crystal content is low when the temperature of the molten glass G decreases (step S202).

[0054] Generally, crystals are less likely to melt than glass. Therefore, if the crystal content is high, the time required for crystal disappearance increases, and the time required for restarting operations increases. According to this embodiment, since the crystal content generated when the temperature of the molten glass G decreases (step S202) is low, the time required for restarting operations can be shortened.

[0055] Since molten glass G is the second glass and not the first glass, it not only has a low crystal content but also a high rate of crystal disappearance. The rate of crystal disappearance is evaluated by heating pre-devitrified glass grains (size: approximately 3 mm square) at a temperature corresponding to the desired viscosity for 4 hours, and then rapidly cooling them to see if the devitrification disappears. The evaluation results of the crystal disappearance rate for glass A and glass B are shown in Table 2.

[0056] [Table 2]

[0057] In Table 2, "○" indicates that devitrification has disappeared, and "×" indicates that devitrification has not disappeared. From Table 2, it can be seen that glass B shows devitrification disappearance at a lower temperature compared to glass A, and that the rate of crystal disappearance is faster.

[0058] During the temperature rise of the molten glass G (step S205), a heating device 13 may be provided at the outlet 10a of the melting furnace 10. Unlike the heating device 11, the heating device 13 may be provided outside the melting furnace 10. The heating device 13 may include, for example, a burner that blows a flame toward the outlet 10a, an electric heater, or an induction heating device. The induction heating device heats the molten glass G by forming eddy currents in the molten glass G. The cooling device 12 used in the repair (step S203) is removed before step S205. The heating device 13 may also be provided inside the melting furnace 10, and may include, for example, multiple electrodes that apply voltage to the molten glass G.

[0059] During the temperature rise of the molten glass G (step S205), an insulating material may be provided at the outlet 10a of the melting furnace 10. This allows the temperature of the molten glass G to pass through the devitrification temperature range in a short time at the outlet 10a of the melting furnace 10.

[0060] The temperature rise of the molten glass G (step S205) includes, for example, heating the frozen glass GA blocking the outlet 10a of the melting furnace 10 with the heating device 13, and heating the glass cullet GB pre-packed in the transfer device 20 with the heating device provided in the transfer device 20. Examples of heating devices provided in the transfer device 20 include the first horizontal pipe 22A and the vertical pipe 23A.

[0061] Step S206 involves transferring the molten glass G held by the melting furnace 10 from the second glass to a viscosity of 1.0 × 10 4 dPa·s ~1.0 × 10 7The process involves changing to a third glass in which the maximum crystal growth rate in the temperature range corresponding to dPa·s is greater than that of the second glass. The third glass may have the same composition as the first glass or a different composition. The change in molten glass G is carried out by changing the glass raw material. By changing the glass raw material, the molten glass G can be changed gradually. The change in molten glass G is carried out by a general method. After step S206, the glass article is manufactured.

[0062] In this embodiment, step S103 includes freezing of the molten glass G, but it does not necessarily include freezing of the molten glass G. 4 This is because devitrification can occur when the temperature decreases from a temperature higher than the temperature corresponding to dPa·s to a lower temperature.

[0063] Alternatively, step S103 may also involve reducing the flow rate of the molten glass G to lower the temperature of the molten glass G. If the flow rate of the molten glass G is reduced, the amount of heat transported along with the molten glass G from the upstream to the downstream side decreases, and the temperature of the molten glass G decreases.

[0064] For example, as shown in Figure 7, closing the inlet of the molding apparatus 30 reduces the flow rate of molten glass G. In this case, molten glass G may be discharged from the melting furnace 10 or the transfer device 20 so that the flow of molten glass G does not stop completely. The discharge direction of the molten glass G may be horizontal or downward.

[0065] Next, an example of a glass manufacturing apparatus will be described with reference to Figures 9 to 11. The glass manufacturing apparatus includes a melting furnace 10 for melting glass raw materials. The outlet 10a of the melting furnace 10 is provided with a throat 14. The throat 14 has a bottom wall 141, a pair of side walls 142 and 143 installed on the bottom wall 141, and a ceiling wall 144 installed on the pair of side walls 142 and 143. The bottom wall 141, the pair of side walls 142 and 143, and the ceiling wall 144 are each in contact with the molten glass G.

[0066] The glass manufacturing apparatus preferably includes a jack 15 that holds down the ceiling wall 144 and at least one of the pair of side walls 142 and 143. The jack 15 has a movable part 151 that moves in both directions: in the direction of pushing the ceiling wall 144 and at least one of the pair of side walls 142 and 143, and in the direction opposite to the pushing direction. By adjusting the position of the movable part 151, the force pushing the ceiling wall 144 and the other can be adjusted. The jack 15 may further have a fixed part 152 that is fixed to a fixed frame 16. The movable part 151 moves relative to the fixed part 152. The jack 15 is, for example, a screw jack. A screw jack includes a screw as the movable part 151 and a nut as the fixed part 152. The jack 15 may also be a rack jack or a hydraulic jack, etc.

[0067] It is preferable that there be multiple jacks 15. It is preferable that each jack 15 is provided separately for each object to be held down. For example, it is preferable that the jack 15 that holds down the ceiling wall 144, the jack 15 that holds down the left side wall 142, and the jack 15 that holds down the right side wall 143 are provided separately.

[0068] For example, it is preferable that the jack 15 pushes back against the pressure of the molten glass G, against the ceiling wall 144 and at least one of the pair of side walls 142, 143. One jack 15 pushes the ceiling wall 144 downwards. Another jack 15 pushes the left side wall 142 to the right. Yet another jack 15 pushes the right side wall 143 to the left.

[0069] Furthermore, it is preferable that the jacks 15 push back against the flow of molten glass G, pushing back the ceiling wall 144 and at least one of the pair of side walls 142 and 143 from the downstream side to the upstream side. It is preferable that the jacks 15 be provided separately for each object to be pressed and for each direction of pushing back. For example, it is preferable that the jack 15 that pushes the ceiling wall 144 downward and the jack 15 that pushes the ceiling wall 144 from the downstream side to the upstream side be provided separately.

[0070] The glass manufacturing apparatus preferably includes a spring 17 between the ceiling wall 144, at least one of the pair of side walls 142 and 143, and the jack 15. The spring 17 can absorb dimensional changes in the throat 14 due to temperature changes. As a result, for example, it is possible to prevent the pushing force of the jack 15 from becoming too strong, thereby preventing damage to the throat 14. It is also possible to prevent the pushing force of the jack 15 from becoming too weak, thereby preventing leakage of molten glass G.

[0071] Furthermore, the pushing force of the jack 15 can be adjusted by adjusting the position of the movable part of the jack 15. However, by using the jack 15 in combination with the spring 17, the frequency of adjusting the position of the movable part of the jack 15 can be reduced.

[0072] The glass manufacturing apparatus preferably includes an insulating material 18 between the ceiling wall 144, at least one of the pair of side walls 142 and 143, and the jack 15. The insulating material 18 is used when an electric current is passed through the molten glass G to generate heat. The insulating material 18 prevents electric current from flowing through the jack 15. The insulating material 18 preferably has a higher electrical resistance than the throat 14.

[0073] When the jack 15 and spring 17 are used together, it is preferable to place the insulating material 18 between the spring 17 and the throat 14. This prevents current from flowing through the spring 17. However, the arrangement of the spring 17 and insulating material 18 may be reversed, and the insulating material 18 may be placed between the spring 17 and the jack 15. In any case, the insulating material 18 prevents current from flowing through the jack 15.

[0074] Next, a method for manufacturing the glass article shown in Figure 3 using the glass manufacturing apparatus shown in Figures 9 to 11 will be described. The differences will be explained below. The manufacturing method preferably includes adjusting the position of the movable part 151 of the jack 15 in step S202 (temperature decrease of molten glass) or S205 (temperature increase of molten glass) shown in Figure 3. The manufacturing method more preferably includes adjusting the position of the movable part 151 of the jack 15 in both steps S202 and S205 shown in Figure 3.

[0075] In step S202 (temperature of molten glass decreases) or S205 (temperature of molten glass increases), the temperature of the throat 14 changes significantly, and the dimensions of the throat 14 change significantly. Even with large changes in the dimensions of the throat 14, the pushing force of the jack 15 can be appropriately adjusted by adjusting the position of the movable part 151 of the jack 15. Therefore, damage to the throat 14 and leakage of molten glass G can be suppressed.

[0076] In step S202 (decrease in the temperature of the molten glass), the temperature of the throat 14 gradually decreases. At this time, the dimensions of the throat 14 basically decrease. Therefore, the movable part 151 of the jack 15 is basically moved in the pushing direction so that the pushing force of the jack 15 does not become too weak. However, a phase transformation may occur during the gradual decrease in the temperature of the throat 14, causing the dimensions of the throat 14 to increase. In this case, the movable part 151 of the jack 15 may be moved in the opposite direction to the pushing direction so that the pushing force of the jack 15 does not become too strong.

[0077] On the other hand, in step S205 (temperature rise of molten glass), the temperature of the throat 14 gradually increases. At this time, the dimensions of the throat 14 basically increase. Therefore, the movable part 151 of the jack 15 is basically moved in the opposite direction to the pushing direction so that the pushing force of the jack 15 does not become too strong. However, a phase transformation may occur as the temperature of the throat 14 gradually increases, causing the dimensions of the throat 14 to decrease. In this case, the movable part 151 of the jack 15 may be moved in the pushing direction so that the pushing force of the jack 15 does not become too weak.

[0078] Furthermore, the manufacturing method preferably includes attaching the insulation material 19 to the ceiling wall 144 and at least one of the pair of side walls 142 and 143 after step S201 (changing the molten glass) as shown in Figure 3 and before step S202 (decreasing the temperature of the molten glass). It is more preferable that the insulation material 19 be attached to all of the ceiling wall 144 and the pair of side walls 142 and 143. The insulation material 19 may also be attached to the bottom wall 141.

[0079] The insulation material 19 suppresses the rapid temperature change of the throat 14 in step S202 (temperature decrease of molten glass). This suppresses the rapid dimensional change of the throat 14, and allows the position adjustment of the movable part 151 of the jack 15 to be performed before any problems occur. Preferably, the absolute value of the rate of temperature decrease of the molten glass G at the downstream end of the throat 14 is less than 30°C / hr.

[0080] It is preferable that the heat insulating material 19 is positioned to avoid the jack 15, spring 17, and insulating material 18. In step S205 (temperature rise of molten glass), when the heating device 13 heats the throat 14, it is preferable that the heat insulating material 19 is positioned on the opposite side of the throat 14 with respect to the heating device 13. In other words, it is preferable that the heat insulating material 19 is positioned to cover the heating device 13 from the outside.

[0081] Furthermore, the manufacturing method preferably includes attaching the insulation material 19 to the ceiling wall 144 and at least one of the pair of side walls 142 and 143 before step S205 (temperature rise of the molten glass) shown in Figure 3. It is more preferable to attach the insulation material 19 to all of the ceiling wall 144 and the pair of side walls 142 and 143. The insulation material 19 may also be attached to the bottom wall 141.

[0082] The insulation material 19 suppresses the rapid temperature change of the throat 14 in step S205 (temperature rise of molten glass). This suppresses the rapid dimensional change of the throat 14, allowing the position adjustment of the movable part 151 of the jack 15 to be performed before any problems occur. The insulation material 19 may be applied after step S202 (temperature decrease of molten glass), but as described above, it is preferable to apply it before step S202.

[0083] It is preferable to remove the insulation material 19 from the throat 14 after step S205 (temperature rise of molten glass). By cooling the throat 14 with outside air, erosion of the throat 14 can be suppressed. It is preferable that the jack 15, spring 17 and insulating material 18 are always provided.

[0084] The following additional information is disclosed regarding the above embodiments, etc. [Note 1] A method for manufacturing a glass article, comprising: heating glass raw materials inside a melting furnace to produce molten glass; transferring the molten glass from the melting furnace to a molding apparatus using a transfer device; and molding the molten glass into a predetermined shape in the molding apparatus, The process involves repairing the flow path of the molten glass downstream of the melting furnace while the melting furnace is holding the molten glass. Before performing the aforementioned repair, upstream of the location where the repair will be performed, the viscosity was 1.0 × 10 4 The method involves lowering the temperature of the molten glass from a temperature higher than the temperature corresponding to dPa·s to a temperature lower than that, The process involves changing the molten glass held in the melting furnace from the first glass to the second glass before lowering the temperature of the molten glass. The first glass has a viscosity of 1.0 × 10⁻⁶. 4 dPa·s ~1.0 × 10 7 The maximum crystal growth rate in the temperature range corresponding to dPa·s is 50 μm / hr or more. The second glass has a viscosity of 1.0 × 10⁻⁶. 4 dPa·s ~1.0 × 10 7 A method for manufacturing glass articles, wherein the maximum crystal growth rate in the temperature range corresponding to dPa·s is 40 μm / hr or less. [Note 2] A method for manufacturing a glass article according to Appendix 1, wherein lowering the temperature of the molten glass includes freezing the molten glass. [Note 3] The method for manufacturing a glass article as described in Appendix 2, wherein the freezing of the molten glass is performed at the outlet of the melting furnace. [Note 4] The outlet of the melting furnace is provided with a throat, the throat having a bottom wall, a pair of side walls installed on the bottom wall, and a ceiling wall installed on the pair of side walls, the bottom wall, the pair of side walls, and the ceiling wall are each in contact with the molten glass. The manufacturing method for glass articles according to Appendix 3, comprising pressing down on the ceiling wall and at least one of the pair of side walls with a jack. [Note 5] The jack has a movable part that moves in both directions: in a direction that pushes the ceiling wall and at least one of the pair of side walls, and in the direction opposite to the pushing direction. The manufacturing method for glass articles according to Appendix 4, comprising adjusting the position of the movable part of the jack when lowering the temperature of the molten glass. [Note 6] A method for manufacturing a glass article according to Appendix 4 or 5, wherein a spring is provided between the ceiling wall, at least one of the pair of side walls, and the jack. [Note 7] A method for manufacturing a glass article according to any one of appendices 4 to 6, comprising applying insulating material to the ceiling wall and at least one of the pair of side walls after changing the molten glass held in the melting furnace from the first glass to the second glass, and before lowering the temperature of the molten glass. [Note 8] A method for manufacturing a glass article according to any one of the appendices 4 to 7, wherein the absolute value of the rate of decrease in the temperature of the molten glass at the downstream end of the throat is less than 30°C / hr. [Note 9] A method for manufacturing a glass article according to any one of the appendices 1 to 8, comprising reducing the flow rate of the molten glass upstream of the location where the repair is performed to lower the temperature of the molten glass. [Note 10] After the aforementioned repair, the temperature of the molten glass was reduced in the area where the temperature of the molten glass was reduced to a viscosity of 1.0 × 10⁻⁶. 4 Raising the temperature to a level higher than the temperature corresponding to dPa·s, After raising the temperature of the molten glass, the molten glass held in the melting furnace is separated from the second glass by a viscosity of 1.0 × 10 4 dPa·s ~1.0 × 10 7 The third glass is changed to one in which the maximum crystal growth rate in the temperature range corresponding to dPa·s is greater than that of the second glass, A method for manufacturing a glass article as described in any one of the appendices 1 to 9, comprising: [Note 11] The aforementioned repair includes replacing the transfer device, After replacing the transfer device, the glass frozen at the outlet of the melting furnace is heated with a heating device. After the frozen glass is melted again at the outlet of the melting furnace, the molten glass held by the melting furnace is obtained from the second glass with a viscosity of 1.0 × 10 4 dPa·s ~1.0 × 10 7 The third glass is changed to one in which the maximum crystal growth rate in the temperature range corresponding to dPa·s is greater than that of the second glass, A method for manufacturing a glass article as described in any one of the appendices 3 to 8, comprising: [Note 12] The aforementioned repair includes replacing the transfer device, After replacing the transfer device, the glass frozen at the outlet of the melting furnace is heated with a heating device, and the glass cullet that was previously packed into the transfer device is heated with a heating device provided in the transfer device. After the frozen glass is melted again at the outlet of the melting furnace, the molten glass held by the melting furnace is obtained from the second glass with a viscosity of 1.0 × 10 4 dPa·s ~1.0 × 10 7 The third glass is changed to one in which the maximum crystal growth rate in the temperature range corresponding to dPa·s is greater than that of the second glass, A method for manufacturing a glass article as described in any one of the appendices 3 to 8, comprising: [Note 13] The outlet of the melting furnace is provided with a throat, the throat having a bottom wall, a pair of side walls installed on the bottom wall, and a ceiling wall installed on the pair of side walls, the bottom wall, the pair of side walls, and the ceiling wall are each in contact with the molten glass. The manufacturing method for glass articles according to Appendix 11 or 12, comprising pressing the ceiling wall and at least one of the pair of side walls with a jack. [Note 14] The jack has a movable part that moves in a direction that pushes the ceiling wall and at least one of the pair of side walls, and in a direction opposite to the pushing direction. The method for manufacturing a glass article as described in Appendix 13, comprising adjusting the position of the movable part of the jack when remelting the glass that has been frozen at the outlet of the melting furnace. [Note 15] A method for manufacturing a glass article according to appendix 13 or 14, wherein a spring is provided between the ceiling wall, at least one of the pair of side walls, and the jack. [Note 16] A method for manufacturing a glass article according to any one of appendices 13 to 15, comprising applying insulating material to the ceiling wall and at least one of the pair of side walls before remelting the glass frozen at the outlet of the melting furnace. [Note 17] The change of the molten glass from the first glass to the second glass, the decrease in the temperature of the molten glass, and the repair are as follows: The melting furnace has a viscosity of 1.0 × 10 4 A method for manufacturing a glass article according to any one of the appendices 1 to 16, wherein the molten glass is held at a temperature higher than the temperature corresponding to dPa·s. [Note 18] A glass manufacturing apparatus equipped with a melting furnace for melting glass raw materials, The outlet of the melting furnace is provided with a throat, the throat having a bottom wall, a pair of side walls installed on the bottom wall, and a ceiling wall installed on the pair of side walls, the bottom wall, the pair of side walls, and the ceiling wall are each in contact with the molten glass. The glass manufacturing apparatus comprises a jack that holds down at least one of the ceiling wall, the pair of side walls, and the bottom wall.

[0085] The above describes a method for manufacturing glass articles related to this disclosure, but this disclosure is not limited to the embodiments described above. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These also naturally fall within the technical scope of this disclosure. [Explanation of Symbols]

[0086] 10. Melting furnace 20 Transfer device 30 Molding equipment G molten glass GA Frozen Glass

Claims

1. A method for manufacturing a glass article, comprising: heating glass raw materials inside a melting furnace to produce molten glass; transferring the molten glass from the melting furnace to a molding apparatus using a transfer device; and molding the molten glass into a predetermined shape in the molding apparatus, The process involves repairing the flow path of the molten glass downstream of the melting furnace while the melting furnace is holding the molten glass. Before performing the aforementioned repair, upstream of the location where the repair will be performed, the viscosity was 1.0 × 10 ４ The method involves lowering the temperature of the molten glass from a temperature higher than the temperature corresponding to dPa·s to a temperature lower than that, The process involves changing the molten glass held in the melting furnace from the first glass to the second glass before lowering the temperature of the molten glass. The first glass has a viscosity of 1.0 × 10 ４ dPa・s~1.0×10 ７ The maximum crystal growth rate in the temperature range corresponding to dPa·s is 50 μm / hr or more. The second glass has a viscosity of 1.0 × 10 ４ dPa・s~1.0×10 ７ A method for manufacturing glass articles, wherein the maximum crystal growth rate in the temperature range corresponding to dPa·s is 40 μm / hr or less.

2. A method for manufacturing a glass article according to claim 1, wherein lowering the temperature of the molten glass includes freezing the molten glass.

3. The method for manufacturing a glass article according to claim 2, wherein the freezing of the molten glass is performed at the outlet of the melting furnace.

4. The outlet of the melting furnace is provided with a throat, the throat having a bottom wall, a pair of side walls installed on the bottom wall, and a ceiling wall installed on the pair of side walls, the bottom wall, the pair of side walls, and the ceiling wall are each in contact with the molten glass. The method for manufacturing a glass article according to claim 3, comprising pressing down on the ceiling wall and at least one of the pair of side walls with a jack.

5. The jack has a movable part that moves in both directions: in a direction that pushes the ceiling wall and at least one of the pair of side walls, and in the direction opposite to the pushing direction. The method for manufacturing a glass article according to claim 4, wherein the manufacturing method comprises adjusting the position of the movable part of the jack when lowering the temperature of the molten glass.

6. A method for manufacturing a glass article according to claim 4, wherein a spring is provided between the ceiling wall, at least one of the pair of side walls, and the jack.

7. A method for manufacturing a glass article according to claim 4, comprising applying an insulating material to at least one of the ceiling wall and the pair of side walls after changing the molten glass held in the melting furnace from the first glass to the second glass, and before lowering the temperature of the molten glass.

8. The method for manufacturing a glass article according to claim 4, wherein the absolute value of the rate of decrease in the temperature of the molten glass at the downstream end of the throat is less than 30°C / hr.

9. A method for manufacturing a glass article according to claim 1, comprising reducing the flow rate of the molten glass upstream of the location where the repair is to be performed, thereby lowering the temperature of the molten glass.

10. After the aforementioned repair, in the location where the temperature of the molten glass was reduced, the temperature of the molten glass was set to a viscosity of 1.0 × 10⁻⁶. ４ Raising the temperature to a level higher than the temperature corresponding to dPa·s, After raising the temperature of the molten glass, the molten glass held in the melting furnace is removed from the second glass with a viscosity of 1.0 × 10 ４ dPa・s~1.0×10 ７ The third glass is changed to one in which the maximum crystal growth rate in the temperature range corresponding to dPa·s is greater than that of the second glass, A method for manufacturing a glass article according to claim 1, comprising:

11. The aforementioned repair includes replacing the transfer device, After replacing the transfer device, the glass frozen at the outlet of the melting furnace is heated with a heating device. After remelting the glass frozen at the outlet of the melting furnace, the molten glass held by the melting furnace is changed from the second glass to a third glass in which the maximum value of the crystal growth rate in the temperature range corresponding to a viscosity of 1.0×10 ４ dPa·s to 1.0×10 ７ dPa·s is greater than that of the second glass, A method for manufacturing a glass article according to claim 3, comprising:

12. The aforementioned repair includes replacing the transfer device, After replacing the transfer device, the glass frozen at the outlet of the melting furnace is heated with a heating device, and the glass cullet that was previously packed into the transfer device is heated with a heating device provided in the transfer device. After the frozen glass is melted again at the outlet of the melting furnace, the molten glass held by the melting furnace is taken from the second glass with a viscosity of 1.0 × 10 ４ dPa・s~1.0×10 ７ The third glass is changed to one in which the maximum crystal growth rate in the temperature range corresponding to dPa·s is greater than that of the second glass, A method for manufacturing a glass article according to claim 3, comprising:

13. The outlet of the melting furnace is provided with a throat, the throat having a bottom wall, a pair of side walls installed on the bottom wall, and a ceiling wall installed on the pair of side walls, the bottom wall, the pair of side walls, and the ceiling wall are each in contact with the molten glass. The method for manufacturing a glass article according to claim 11 or 12, wherein the manufacturing method comprises pressing down on the ceiling wall and at least one of the pair of side walls with a jack.

14. The jack has a movable part that moves in a direction that pushes the ceiling wall and at least one of the pair of side walls, and in a direction opposite to the pushing direction. The method for manufacturing a glass article according to claim 13, further comprising adjusting the position of the movable part of the jack when remelting the glass that has been frozen at the outlet of the melting furnace.

15. A method for manufacturing a glass article according to claim 13, wherein a spring is provided between the ceiling wall, at least one of the pair of side walls, and the jack.

16. A method for manufacturing a glass article according to claim 13, comprising attaching an insulating material to at least one of the ceiling wall and the pair of side walls before remelting the glass frozen at the outlet of the melting furnace.

17. The change of the molten glass from the first glass to the second glass, the decrease in the temperature of the molten glass, and the repair are as follows: The melting furnace has a viscosity of 1.0 × 10 ４ A method for manufacturing a glass article according to any one of claims 1 to 12, wherein the molten glass is held at a temperature higher than the temperature corresponding to dPa·s.

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