Apparatus and method for manufacturing glass article, and method for measuring liquid level

Abstract

This glass article manufacturing device is provided with: a melting furnace (1) serving as a storage tank; and a measurement device (21) that measures the height (H1) of the liquid level (LS) of the molten glass (Gm) stored in the melting furnace (1). A measurement device (21) is provided with: a nozzle (22) immersed in molten glass (Gm) from a liquid surface (LS); a pipe (23) that is introduced from the outside of the melting furnace (1) into the melting furnace (1) at a position higher than the liquid level (LS) and supplies the gas (A) to the nozzle (22); and a pressure gauge (25) that measures the pressure inside the pipe (23) or the nozzle (22) in a state in which bubbles (B) are generated in the molten glass (Gm) from the tip of the nozzle (22) by means of the gas (A).

Description

Technical Field

[0001] The present invention relates to a technology for measuring the liquid level of molten glass stored in a storage tank. Background Art

[0002] In the manufacturing method of glass articles such as glass fiber and glass plate, a storage tank storing molten glass is used. In such a storage tank, in order to homogenize the molten glass or stabilize the flow rate of the molten glass, it is necessary to suppress the large fluctuation of the liquid level of the molten glass stored in the storage tank. Therefore, it is important to measure the liquid level of the molten glass.

[0003] As a liquid level measuring device for measuring the liquid level of molten glass, for example, Patent Document 1 discloses a liquid level measuring device that generates bubbles by supplying gas to molten glass through a flow path component and calculates the liquid level of the molten glass based on the pressure (back pressure) in the flow path component in a state where bubbles are generated.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-151948 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In the liquid level measuring device described in Patent Document 1, the flow path component is prone to loss caused by heat and erosion caused by molten glass, and sometimes needs to be replaced. However, the flow path component is introduced into the molten glass through the bottom wall or side wall of the storage tank (melting furnace) at a position lower than the liquid level of the molten glass. That is, the introduction part (hole) of the flow path component in the wall of the storage tank is located at a position lower than the liquid level of the molten glass and faces the molten glass. Therefore, when the flow path component is replaced, the molten glass in the storage tank may leak from the introduction part of the flow path component. As a result, the liquid level measuring device described in Patent Document 1 has the problem that it is extremely difficult to maintain.

[0009] In addition, when the liquid level measuring device described in Patent Document 1 is applied to an existing storage tank, it is necessary to newly form an introduction portion of the flow path member on the wall of the storage tank at a position lower than the liquid level of the molten glass. However, since the existing storage tank already stores molten glass, there is a possibility that the molten glass will leak out when the introduction portion of the flow path member is formed. Therefore, the liquid level measuring device described in Patent Document 1 has a problem that it is extremely difficult to apply to an existing storage tank.

[0010] An object of the present invention is to provide a liquid level measuring device and a measuring method which are easy to maintain and can be easily applied to an existing storage tank.

[0011] Solutions to Solve Problems

[0012] (1) The present invention made in order to solve the above-mentioned problems is a manufacturing device for glass products, comprising: a storage tank that stores molten glass; and a liquid level measuring device that measures the height of the liquid level of the molten glass stored in the storage tank, wherein the liquid level measuring device comprises: a nozzle that is immersed in the molten glass from the liquid surface; a pipe that introduces gas from the outside of the storage tank into the storage tank at a position higher than the liquid surface and supplies gas to the nozzle; and a pressure gauge that measures the pressure in the pipe or the nozzle.

[0013] In this way, the nozzle is immersed in the molten glass from the liquid level of the molten glass, and the pipe is introduced from the outside of the storage tank into the storage tank at a position higher than the liquid level of the molten glass. That is, the introduction part of the pipe in the wall of the storage tank is located at a position higher than the liquid level of the molten glass, so that the molten glass does not substantially leak from the introduction part of the pipe. Therefore, the maintenance of the liquid level measuring device and the application to the existing storage tank become easy.

[0014] (2) In the configuration of (1) above, it is preferred that the pipe is introduced from outside the storage tank into the storage tank through a hole provided in a side wall of the storage tank.

[0015] In this way, since the pipe can be shortened compared to the case where the pipe passes through the ceiling wall of the storage tank, the equipment cost can be reduced.

[0016] (3) In the configuration of (1) or (2) above, it is preferred that the nozzle is held at a predetermined height by a pipe.

[0017] In this way, there is no need to separately provide a nozzle holding member, so the equipment structure can be simplified and the equipment cost can be reduced.

[0018] (4) In any one of the structures of (1) to (3) above, the pipe preferably includes a cooling structure.

[0019] In this way, loss due to heat in the pipe can be suppressed.

[0020] (5) In any one of the structures of (1) to (4) above, the nozzle preferably includes a tube portion made of platinum or a platinum alloy through which the gas flows.

[0021] In this way, loss due to heat and erosion due to molten glass can be suppressed.

[0022] (6) In the configuration of (5) above, the nozzle preferably includes a refractory layer made of a refractory material covering the pipe portion, and a protective layer made of platinum or a platinum alloy covering the refractory layer.

[0023] Thus, the protective layer can be used to suppress the erosion of the nozzle caused by the molten glass. In addition, the fire-resistant layer can be used to improve the strength of the nozzle, so it is possible to suppress the nozzle deformation due to the force received from the glass raw material, molten glass, etc. during immersion in the molten glass.

[0024] (7) In the structure of (6) above, preferably, the front end portion of the pipe portion is not covered by the fire-resistant layer but is exposed.

[0025] In this way, the outer diameter of the nozzle tip can be reduced, so bubbles are difficult to stagnate around the nozzle tip. Therefore, when bubbles are generated from the nozzle tip, a back pressure equivalent to the pressure applied to the molten glass at the nozzle tip is accurately applied in the nozzle or the pipe, and the measurement accuracy of the liquid level is improved.

[0026] (8) The present invention made in order to solve the above-mentioned problems is a liquid level measuring method for measuring the liquid level of molten glass stored in a storage tank. The liquid level measuring method is characterized in that a nozzle is immersed in the molten glass from the liquid surface and a pipe is provided from outside the storage tank to pass through the upper space of the molten glass in the storage tank and supply gas to the nozzle, and the liquid level is calculated based on the pressure in the pipe or the nozzle.

[0027] In this way, the same effects as those of the corresponding structures already described can be achieved.

[0028] (9) The present invention made in order to solve the above-mentioned problems is a method for manufacturing a glass article, including a liquid level measuring step for measuring the height of the liquid level of molten glass stored in a storage tank, and the manufacturing method of the glass article is characterized in that in the liquid level measuring step, the height of the liquid level is measured using a method having the structure of the above-mentioned (8).

[0029] In this way, the same effects as those of the corresponding structures already described can be achieved.

[0030] Effects of the Invention

[0031] According to the present invention, it is possible to provide a liquid level measuring device and a measuring method which are easy to maintain and can be easily applied to an existing storage tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a side view showing a manufacturing apparatus for a glass article according to a first embodiment of the present invention.

[0033] Figure 2 is a cross-sectional view of a melting furnace.

[0034] Figure 3 yes Figure 2 I-I section view.

[0035] Figure 4 This is a cross-sectional view showing an enlarged view of the nozzle and the surrounding area of ​​the liquid level measuring device.

[0036] Figure 5 yes Figure 4 II-II sectional view.

[0037] Figure 6 This is a cross-sectional view showing an enlarged view of the nozzle and the surrounding area of ​​the liquid level measuring device according to the second embodiment of the present invention.

[0038] Figure 7 It is a cross-sectional view of a melting furnace according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0039] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the same reference numerals are used for the corresponding components in each embodiment, so that repeated descriptions are sometimes omitted. In the case where only a part of the structure is described in each embodiment, the structure of other embodiments previously described can be applied to the other parts of the structure. In addition, not only the combination of structures explicitly stated in the description of each embodiment, but also the structures of multiple embodiments can be partially combined with each other even if not explicitly stated, as long as there is no particular obstacle in the combination.

[0040] (First embodiment)

[0041] like Figure 1 As shown, the manufacturing apparatus of the glass article of the first embodiment includes a melting furnace 1 , a clarification tank 2 , a homogenization tank (stirring tank) 3 , a kettle 4 , a formed body 5 , and transfer pipes 6 to 9 connecting the above components 1 to 5 .

[0042] The melting furnace 1 is a space for performing a melting step for obtaining molten glass Gm. The molten glass Gm functions as a storage tank for storing the molten glass Gm.

[0043] The clarification tank 2 is a space for performing a clarification step of clarifying (defoaming) the molten glass Gm supplied from the melting furnace 1 by the action of a clarifier or the like.

[0044] The homogenization tank 3 is a space for performing a homogenization step of stirring and homogenizing the clarified molten glass Gm by the stirrer 3a. The homogenization tank 3 may be formed by connecting a plurality of homogenization chambers.

[0045] The kettle 4 is a space for performing a state adjustment step of adjusting the molten glass Gm to a state (for example, viscosity) suitable for molding. In addition, the kettle 4 may be omitted.

[0046] The forming body 5 constitutes a forming device and is used for performing a forming step of forming the molten glass Gm into a desired shape. In the present embodiment, the forming body 5 forms the molten glass Gm into a ribbon-shaped glass ribbon by an overflow down-draw method.

[0047] The cross-sectional shape of the forming body 5 (the cross-sectional shape perpendicular to the paper surface) is roughly wedge-shaped, and an overflow trough (not shown) is formed on the upper part of the forming body 5. The molten glass Gm is supplied to the overflow trough by the transfer pipe 9. The molten glass Gm supplied to the overflow trough overflows from the overflow trough and flows down along the side wall surfaces on both sides of the forming body 5 (the side surfaces located on the front and back sides of the paper surface). The molten glass Gm flowing down the side wall surface is fused at the lower top of the side wall surface and formed into a ribbon-shaped glass ribbon Gr. By subjecting the formed glass ribbon Gr to annealing, cutting and other treatments, a glass sheet as a glass product or a glass roll formed by winding a glass ribbon is manufactured.

[0048] The thickness of the glass ribbon Gr (the thickness of the central portion (thin portion) in the width direction excluding the ear portions (thick portions) at both ends in the width direction) is, for example, preferably 0.01 to 2 mm, and more preferably 0.1 to 1 mm.

[0049] Glass plates or glass rolls are used as substrates and protective covers for displays (such as liquid crystal displays and organic EL displays), organic EL lighting, and solar cells.

[0050] The forming device is not limited to a forming device that performs the overflow down-draw method. For example, the forming device may be a forming device that performs other down-draw methods such as the slot down-draw method or the float method.

[0051] The transfer pipes 6 to 9 are composed of cylindrical pipes formed of, for example, platinum or a platinum alloy, and transfer the molten glass Gm in the lateral direction (approximately horizontal direction). The transfer pipes 6 to 9 are electrically heated as needed. It should be noted that platinum includes reinforced platinum, and platinum alloys include reinforced platinum alloys (hereinafter, the same).

[0052] like Figure 2 as well as Figure 3 As shown, the melting furnace 1 includes a bottom wall 1a, side walls 1b, and a ceiling wall 1c, and the components 1a to 1c define a space for storing the molten glass Gm. The side wall 1b includes a front wall 1b1, a rear wall 1b2, a left wall 1b3, and a right wall 1b4.

[0053] In the melting furnace 1, glass raw material Ga is continuously melted to form molten glass Gm. Glass raw material Ga may contain cullet in addition to natural raw materials and chemically generated raw materials. Molten glass Gm is preferably alkali-free glass or aluminosilicate glass for chemical strengthening.

[0054] The front wall 1b1 of the melting furnace 1 is provided with an inlet 10 for feeding glass raw material Ga. The inlet 10 is provided with a screw feeder 11 as a raw material supply mechanism. The raw material supply mechanism may also be other known mechanisms such as a pusher and a vibration feeder. The number and arrangement position of the raw material supply mechanism can be appropriately changed according to the size of the melting furnace 1, etc.

[0055] The outflow port 12 for flowing out the molten glass Gm is provided in the rear wall 1b2 of the melting furnace 1. The transfer pipe 6 is connected to the outflow port 12, and the molten glass Gm is sequentially supplied to the downstream side.

[0056] A plurality of rod-shaped electrodes 13 are provided on the bottom wall 1a of the melting furnace 1. The electrode 13 is not limited to a rod-shaped one, but may be a plate-shaped one, a block-shaped one, or a combination of these. The electrode 13 is not limited to the bottom wall 1a, but may be provided on the left wall 1b3 and the right wall 1b4. The electrode 13 is formed of molybdenum (Mo), for example. The electrode 13 electrically heats the molten glass Gm while being immersed in the molten glass Gm. The electrode 13 is accommodated in a through hole provided in the bottom wall 1a while being held in a cylindrical electrode holder 14 having a cooling mechanism (not shown). It should be noted that the heating method in the melting furnace 1 is not limited to a full electric melting method using only electric heating, and may be, for example, a method of heating only by combustion of a gas fuel (burner) from above the liquid level LS of the molten glass Gm, a method of heating by using both electric heating and combustion of a gas fuel, and the like.

[0057] like Figure 3 As shown, the melting furnace 1 includes a liquid level measuring device 21 for measuring a height H1 of a liquid level LS of the molten glass Gm. The height H1 of the liquid level LS of the molten glass Gm is defined by the height position of the tip of the nozzle 22 as a reference (zero level).

[0058] The liquid level measuring device 21 includes a nozzle 22 , a pipe 23 , a gas supply unit 24 , and a pressure gauge 25 .

[0059] The nozzle 22 generates bubbles B in the molten glass Gm from its front end. The nozzle 22 is immersed in the molten glass Gm from the liquid level LS. The nozzle 22 is in a substantially vertical posture and includes: a first portion 22a, which is located below the liquid level LS and immersed in the molten glass Gm; and a second portion 22b, which is located above the liquid level LS and not immersed in the molten glass Gm. The first portion 22a includes the front end of the nozzle 22, and the second portion 22b includes the base end of the nozzle 22. It should be noted that the nozzle 22 may also be in an inclined posture.

[0060] The pipe 23 supplies the gas A for generating the bubbles B to the nozzle 22. The gas A is supplied to the pipe 23 from the gas supply unit (e.g., a compressor) 24. The pipe 23 is introduced from the outside of the melting furnace 1 into the melting furnace 1 in a substantially horizontal posture through the horizontal hole X1 provided on the side wall 1b (the left wall 1b3 in the example shown) of the melting furnace 1 at a position higher than the liquid level LS. The pipe 23 introduced into the melting furnace 1 is bent downward in a manner from a substantially horizontal posture to a substantially vertical posture in the space above the liquid level LS, and is connected to the base end of the nozzle 22 located above the liquid level LS. That is, the pipe 23 does not contact the molten glass Gm.

[0061] Specifically, the pipe 23 includes: a first straight portion 23a extending in a substantially horizontal direction; a second straight portion 23b extending in a substantially vertical direction; and a third straight portion 23c provided between the first straight portion 23a and the second straight portion 23b and descending from the first straight portion 23a to reach the second straight portion 23b. The first straight portion 23a is arranged so as to span the inside and outside of the melting furnace 1 via the horizontal hole X1 of the side wall 1b, and the second straight portion 23b and the third straight portion 23c are arranged in the melting furnace 1. It should be noted that the shape of the pipe 23 is not particularly limited. For example, the pipe 23 may omit the third straight portion 23c and connect the first straight portion 23a and the second straight portion 23b at a substantially right angle, or may include a curved portion instead of the third straight portion 23c.

[0062] The transverse hole X1 through which the pipe 23 passes may be newly provided at a position higher than the liquid level LS of the side wall 1b, but if, for example, transverse holes such as observation windows for observing the furnace are provided in advance at a position higher than the liquid level LS of the side wall 1b, these already provided transverse holes may be utilized. It should be noted that, when there is a gap between the pipe 23 and the transverse hole X1 when the pipe 23 is inserted into the transverse hole X1, felt, refractory, etc. may be arranged in the gap to fill the gap.

[0063] The nozzle 22 and the pipe 23 are connected to each other and integrated, and the nozzle 22 is held at a predetermined height by the pipe 23. That is, no member for holding the nozzle 22 is provided in the melting furnace 1 except the pipe 23. The pipe 23 and the nozzle 22 can be inserted and pulled out relative to the melting furnace 1 through the horizontal hole X1. It should be noted that in the present embodiment, the pipe 23 is held by a holding member 26 outside the melting furnace 1.

[0064] The horizontal hole X1 through which the pipe 23 passes is located above the liquid level LS of the molten glass Gm. Therefore, the molten glass Gm does not substantially leak out from the horizontal hole X1. Therefore, the maintenance of the liquid level measuring device 21 and its application to the existing melting furnace 1 become easy.

[0065] The pressure gauge 25 measures the pressure (back pressure) in the pipe 23 or the nozzle 22 when the bubbles B are generated in the molten glass Gm by the gas A from the front end of the nozzle 22. It should be noted that the pipe 23 and the nozzle 22 constitute a gas supply path, so the pressure in the pipe 23 is substantially the same as the pressure in the nozzle 22. Therefore, any pressure between the pressure in the pipe 23 and the pressure in the nozzle 22 can be measured. In the present embodiment, the pressure gauge 25 measures the pressure in the pipe 23 outside the melting furnace 1.

[0066] In the liquid level measuring device 21, the height H1 of the liquid level LS of the molten glass Gm is obtained as follows.

[0067] In the liquid level measuring device 21, when measuring the height H1 of the liquid level LS of the molten glass Gm, bubbles B are generated in the molten glass Gm from the front end of the nozzle 22. The timing of generating bubbles B is when the pressure P1 in the pipe 23 and the nozzle 22 is substantially equal to the sum of the pressure P2 of the liquid level LS of the molten glass Gm and the pressure P3 of the molten glass Gm at the height position of the front end of the nozzle 22 (P2+P3). That is, the relationship of equations (1) to (3) holds between these pressures. Here, ρ is the density of the molten glass Gm, and g is the gravitational acceleration.

[0068] P1=P2+P3 (1)

[0069] P3=ρgH1(2)

[0070] H1=(P1-P2) / ρg (3)

[0071] Therefore, by measuring the differential pressure (P1-P2) between the pressure P1 in the pipe 23 and the pressure P2 of the liquid surface LS of the molten glass Gm, the height H1 of the liquid surface LS of the molten glass Gm can be calculated from the formula (3).

[0072] In the present embodiment, the pressure gauge 25 is composed of a differential pressure gauge (e.g., a gauge pressure gauge). Here, the pressure P2 of the liquid surface LS of the molten glass Gm in the furnace of the melting furnace 1 is sometimes adjusted to be higher than the atmospheric pressure PA or lower than the atmospheric pressure PA. However, even in this case, the difference between the pressure P2 of the liquid surface LS of the molten glass Gm and the atmospheric pressure PA is small, and the two can be regarded as substantially equal. Therefore, in the present embodiment, the pressure gauge 25 is configured to measure the differential pressure (P1-PA) between the pressure P1 in the pipe 23 and the atmospheric pressure PA instead of measuring the differential pressure (P1-P2) between the pressure P1 in the pipe 23 and the pressure P2 of the liquid surface LS of the molten glass Gm. And, if the differential pressure (P1-PA) is measured, the height H1 of the liquid surface LS of the molten glass Gm can be calculated according to formula (4).

[0073] H1=(P1-PA) / ρg (4)

[0074] It should be noted that the pressure gauge 25 may also be configured to measure the differential pressure (P1-P2). The pressure gauge 25 may also be an absolute pressure gauge that can individually measure each pressure required for calculating the height H1. The liquid level measuring device 21 may also include a calculation unit that automatically calculates the height H1 of the liquid level LS of the molten glass Gm according to formula (3) or (4). In addition, the height difference H2 between the height position of the bottom wall 1a and the front end of the nozzle 22 can be measured in advance or set to a predetermined value, so the height (H1+H2) of the liquid level LS of the molten glass Gm with the bottom wall 1a as the reference (zero level) can also be calculated.

[0075] like Figure 4 as well as Figure 5 As shown, the nozzle 22 includes a pipe portion 27 , a fire-resistant layer 28 , and a protective layer 29 .

[0076] The tube 27 is a tubular body made of platinum or a platinum alloy in which the gas A flows. By making the tube 27 of platinum or a platinum alloy, it is possible to suppress the tube 27 from being lost due to heat or being corroded by the molten glass Gm.

[0077] The refractory layer 28 is a layer made of refractory material covering the tube 27. By providing the refractory layer 28 in this way, the strength of the nozzle 22 can be improved, so that the nozzle 22 (strictly speaking, the tube 27) can be suppressed from being deformed by the force (for example, upward force) received from the glass raw material Ga, the molten glass Gm, etc. during immersion in the molten glass Gm. As the refractory material constituting the refractory layer 28, for example, bricks, amorphous refractory materials, etc. can be used. As bricks, for example, zirconia electrocast bricks, alumina electrocast bricks, alumina-zirconia electrocast bricks, AZS (Al-Zr-Si) electrocast bricks, and high-purity alumina (for example, alumina tubes) can be used. As amorphous refractory materials, for example, refractory cements such as alumina cement can be used.

[0078] The protective layer 29 is a layer made of platinum or a platinum alloy for covering the fire-resistant layer 28. By providing the protective layer 29 in this way, it is possible to suppress the erosion of the fire-resistant layer 28 by the molten glass Gm.

[0079] The front end of the tube 27 is not covered by the fire-resistant layer 28 and the protective layer 29 and is exposed. That is, the front end of the tube 27 protrudes downward than the front ends of the fire-resistant layer 28 and the protective layer 29. The protrusion amount L1 of the front end of the exposed tube 27 is preferably 10 to 200 mm, and more preferably 50 to 100 mm. The outer diameter of the exposed tube 27 is preferably 10 to 50 mm, and more preferably 10 to 30 mm. It should be noted that the front ends of the fire-resistant layer 28 and the protective layer 29 are provided with plane portions 28a and 29a that are substantially orthogonal to the longitudinal direction of the tube 27. If the front end of the tube 27 is exposed in this way, the outer diameter of the front end of the nozzle 22 can be reduced, so it is difficult for the bubbles B to stagnate around the front end of the nozzle 22. Therefore, when the bubbles B are generated from the front end of the nozzle 22, the back pressure is accurately applied to the nozzle 22 or the pipe 23, and the measurement accuracy of the height H1 of the liquid level LS is improved.

[0080] Although not shown in the figure, the pipe 23 includes an inner pipe through which the gas A for generating bubbles B in the molten glass Gm flows, and a cooling structure arranged to cover the inner pipe. The inner pipe and the cooling structure can be made of, for example, stainless steel or heat-resistant steel.

[0081] The base end of the inner tube is connected to the gas supply unit 24, and the front end of the inner tube is connected to the base end of the tube 27 of the nozzle 22. Therefore, the gas A supplied from the gas supply unit 24 flows through the inner tube of the pipe 23, flows through the inside S1 of the tube 27 of the nozzle 22, and is discharged into the molten glass Gm.

[0082] The cooling structure has a flow path through which the refrigerant supplied and discharged to the outside flows, so that loss of the pipe 23 (inner pipe) due to heat can be prevented.

[0083] Hereinafter, a method for manufacturing a glass article using the manufacturing apparatus having the above-described structure will be described.

[0084] The method includes a melting step, a molten glass supplying step, a forming step, an annealing step, and a cutting step.

[0085] In the melting process, the glass raw material Ga supplied to the melting furnace 1 is heated to generate molten glass Gm. The liquid surface LS of the molten glass Gm may also be covered by a covering layer Gx. The covering layer Gx includes the glass raw material Ga and / or the bubble layer Gb. The bubble layer Gb is formed as carbon oxygen gas (CO, CO2), O2 gas, SO2 gas, etc. are generated by the glass raw material Ga. By covering the liquid surface LS of the molten glass Gm with the covering layer Gx, the heat dissipation of the molten glass Gm can be suppressed. As a result, the temperature of the molten glass Gm can be reliably maintained, thereby achieving energy saving. It should be noted that the bubble layer Gb may not be provided.

[0086] The melting process also includes a liquid level measuring step of measuring the height of the liquid level LS of the molten glass Gm stored in the melting furnace 1. In the liquid level measuring step, the height of the liquid level LS is measured using a liquid level measuring device 21. Specifically, gas A is supplied to the nozzle 22 through the pipe 23, and bubbles B are generated in the molten glass Gm from the front end of the nozzle 22. In addition, the pressure difference (P1-PA) between the pressure P1 in the nozzle 22 (tube 27) or the pipe 23 and the atmospheric pressure PA when the bubbles B are generated is measured using a pressure gauge 25. Based on the measured pressure difference (P1-PA), the height H1 of the liquid level LS is calculated according to formula (4).

[0087] In the molten glass supply process, the molten glass Gm of the melting furnace 1 is sequentially transferred to the clarification tank 2, the homogenization tank 3, the kettle 4, and then the forming body 5 through each transfer pipe 6 to 9. In the clarification tank 2, the molten glass Gm is clarified (defoamed) by the action of a clarifier or the like (clarification process). In the homogenization tank 3, the molten glass Gm is stirred and homogenized (homogenization process). In the kettle 4, the state (e.g., viscosity, flow rate) of the molten glass Gm is adjusted (state adjustment process).

[0088] In the forming step, the molten glass Gm is supplied to the forming body 5 through the molten glass supplying step. The forming body 5 allows the molten glass Gm to overflow from the overflow channel and flow down along the side wall surface. The forming body 5 allows the flowing molten glass Gm to fuse at the lower top, thereby forming the glass ribbon Gr.

[0089] Thereafter, the glass ribbon Gr is cooled in an annealing furnace in an annealing process and cut by a cutting device in a cutting process. Thus, a glass sheet of a predetermined size is cut from the glass ribbon Gr. Alternatively, the glass ribbon Gr may be wound into a roll after removing both end portions (ear portions) in the width direction of the glass ribbon Gr in the cutting process to obtain a glass roll (winding process).

[0090] (Second embodiment)

[0091] like Figure 6 As shown, in the second embodiment, a modified example of the nozzle 22 of the liquid level measuring device 21 is illustrated.

[0092] As shown in the figure, in the present embodiment, the nozzle 22 includes a pipe 27, a fire-resistant layer 28, and a protective layer 29 as in the first embodiment, and the front end of the pipe 27 is not covered by the fire-resistant layer 28 and the protective layer 29 but is exposed. That is, the front end of the pipe 27 protrudes downward than the front ends of the fire-resistant layer 28 and the protective layer 29.

[0093] On the other hand, as a point different from the first embodiment, the front end of the refractory layer 28 and the protective layer 29 has a tapered portion 28b, 29b that gradually expands from the front end to the top. If the tapered portions 28b, 29b are set in this way, the bubbles B that rise under the action of buoyancy are smoothly guided upward along the tapered portions 28b, 29b. Therefore, it is more difficult for the bubbles B to stagnate around the front end of the nozzle 22, and the measurement accuracy of the height H1 of the liquid level LS is further improved. In addition, when dipping into the molten glass Gm, the force received from the glass raw material Ga, the molten glass Gm, etc. can be reduced, and the nozzle 22 can be smoothly dipped into the molten glass.

[0094] The inclination angle θ of the tapered portions 28 b and 29 b with respect to the vertical direction is preferably 10 to 60 degrees, and more preferably 30 to 45 degrees.

[0095] (Third Embodiment)

[0096] like Figure 7 As shown, in the third embodiment, a modified example of the pipe 23 of the liquid level measuring device 21 is illustrated.

[0097] In the present embodiment, the pipe 23 is introduced from the outside of the melting furnace 1 into the melting furnace 1 in a substantially vertical posture through the vertical hole X2 provided on the top wall 1c of the melting furnace 1 at a position higher than the liquid level LS. The pipe 23 introduced into the melting furnace 1 is connected to the base end of the nozzle 22 located above the liquid level LS in a substantially vertical posture in the space above the liquid level LS. The front end side of the nozzle 22 is immersed in the molten glass Gm from the liquid level LS.

[0098] Here, when the pipe 23 is introduced from the outside of the melting furnace 1 into the melting furnace 1 through the longitudinal hole X2 of the top wall 1c, the length of the pipe 23 tends to be longer than when the pipe 23 is introduced from the outside of the melting furnace 1 into the melting furnace 1 through the transverse hole X1 of the side wall 1b. Therefore, from the viewpoint of reducing equipment cost, it is preferable to have a structure in which the pipe 23 is introduced from the outside of the melting furnace 1 into the melting furnace 1 through the transverse hole X1 of the side wall 1b as described in the first embodiment.

[0099] It should be noted that the present invention is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects. The present invention can be modified in various ways without departing from the gist of the present invention.

[0100] In the above-mentioned embodiment, a glass plate and a glass roll are exemplified as the glass article, but the glass article can be, for example, a glass ball, a glass tube, a glass block, a glass fiber, etc., and may be in any shape other than these.

[0101] In the above-mentioned embodiment, the case of measuring the height of the liquid level of the molten glass stored in the melting furnace is described, but the present invention can also be applied to the case of measuring the height of the liquid level of the molten glass stored in a storage tank other than the melting furnace, such as a feeder connected to the melting furnace or a clarification tank having a furnace wall made of refractory material. It should be noted that in the case of a glass fiber manufacturing device, the feeder has a sleeve including a plurality of nozzles for forming glass fibers from the molten glass at the bottom.

[0102] Description of Reference Numerals

[0103] 1 Melting furnace

[0104] 1a Bottom wall

[0105] 1b Sidewall

[0106] 1c Top wall

[0107] 2 Clarification tank

[0108] 3 Homogenization tank

[0109] 4 cauldron

[0110] 5 formed body

[0111] 6~9 Transfer pipe

[0112] 10 Input port

[0113] 11 screw feeder

[0114] 12 Outlet

[0115] 13 Electrodes

[0116] 14 Electrode holder

[0117] 21. Measurement device

[0118] 22 Mouth

[0119] 23 Piping

[0120] 24 Gas supply unit

[0121] 25. Pressure gauge

[0122] 26. Retaining member

[0123] 27 Pipe

[0124] 28 Refractory Layer

[0125] 29 Protective layer

[0126] A Gas

[0127] B Bubble

[0128] C Refrigerant

[0129] Ga glass raw materials

[0130] Gb Bubble layer

[0131] Gm Molten glass

[0132] Gr Glass Ribbon

[0133] Gx Overlay

[0134] LS Molten glass level

[0135] X1 Horizontal hole (side wall)

[0136] X2 Vertical hole (top wall).

Claims

1. A manufacturing device for glass articles, comprising: a storage tank storing molten glass; and a liquid level measuring device measuring the height of the liquid level of the molten glass stored in the storage tank, wherein: The liquid level measuring device comprises: a nozzle immersed in the molten glass from the liquid surface; a piping that introduces gas from outside the storage tank into the storage tank at a position higher than the liquid surface and supplies gas to the nozzle; and a pressure gauge that measures the pressure in the piping or the nozzle.

2. The manufacturing device for glass articles according to claim 1, wherein: The pipe is introduced from the outside of the storage tank into the storage tank through a hole provided in a side wall of the storage tank.

3. The manufacturing device for glass articles according to claim 1 or 2, wherein: The nozzle is held at a predetermined height by the pipe.

4. The manufacturing device for glass articles according to claim 1 or 2, wherein: The pipe includes a cooling structure.

5. The manufacturing device for glass articles according to claim 1 or 2, wherein: The nozzle includes a tube portion made of platinum or a platinum alloy through which the gas flows.

6. The manufacturing device for glass articles according to claim 5, wherein: The nozzle includes a refractory layer made of a refractory material covering the pipe portion and a protective layer made of platinum or a platinum alloy covering the refractory layer.

7. The manufacturing device for glass articles according to claim 6, wherein: The front end portion of the pipe portion is not covered by the fire-resistant layer and is exposed.

8. A method for measuring a liquid level, comprising measuring the liquid level of molten glass stored in a storage tank, The liquid level measuring method is characterized in that: A nozzle immersed in the molten glass from the liquid surface and a pipe for introducing gas from outside the storage tank into the storage tank and supplying gas to the nozzle are provided at a position higher than the liquid surface. The height of the liquid surface is obtained based on the pressure in the pipe or the nozzle.

9. A method for manufacturing a glass article, comprising a liquid level measuring step of measuring the liquid level of molten glass stored in a storage tank, The method for manufacturing the glass article is characterized in that: In the liquid level measuring step, the height of the liquid level is measured using the liquid level measuring method according to claim 8 .

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