Glass depth measuring method, bubble layer depth measuring method, and glass melting furnace

Abstract

To accurately measure the depth of molten glass stored in a glass melting furnace and the depth of a foam layer formed on the molten glass.SOLUTION: A method for measuring the depth of molten glass Gm stored in a glass melting furnace 1, comprising: a bubble generation step in which a compressed gas CA is supplied to the molten glass Gm through a channel pipe 13 having a gas channel 12 opened into the molten glass Gm in the glass melting furnace 1 to generate bubbles B; and a glass depth measuring step in which the depth H1 of the molten glass Gm is obtained based on the air pressure P1 in the gas flow path 12 in which bubbles B are generated.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a technique for measuring the depth of molten glass stored in a glass melting furnace and the depth of a bubble layer formed on the molten glass. [Background technology]

[0002] 2. Description of the Related Art Methods for producing glass articles such as glass fibers and glass sheets include a melting step in which glass raw materials are melted in a glass melting furnace to form molten glass that is the basis of the glass article.

[0003] In glass melting furnaces, those of the type that melt glass raw materials by gas combustion are widely used, but there are also cases where those of the type that melt glass raw materials only by electrical heating are used (for example, see Patent Document 1).

[0004] In a glass melting furnace, in order to homogenize the molten glass and stabilize the outflow rate of the molten glass, it is necessary to operate the furnace while keeping the depth of the molten glass stored therein constant.

[0005] For example, Patent Document 2 discloses that in a glass melting furnace of the type that melts glass raw materials by gas combustion, the depth of the molten glass (liquid surface level) is determined based on the results of image processing of an image inside the glass melting furnace captured by a camera positioned above the liquid surface of the molten glass. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2003-183031 A [Patent Document 2] International Publication No. 2013 / 021771 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, a bubble layer may be generated on the molten glass stored in a glass melting furnace. In particular, in a glass melting furnace of the type in which glass raw materials are melted only by electric heating, there are often no heating means above the liquid surface of the molten glass, and a bubble layer is likely to be formed on the molten glass. This is because the bubble layer is not heated and disappears by the heating means arranged above the liquid surface of the molten glass. The bubble layer is formed due to sulfur compounds contained in the glass raw materials and SO2 gas generated by decomposition of sulfates added as a fining agent.

[0008] However, in a method using a camera placed above the surface of the molten glass, as in Patent Document 2, if a bubble layer forms on the molten glass, a problem may arise in that the bubble layer gets in the way and makes it difficult to accurately measure the depth of the molten glass.

[0009] On the other hand, the bubble layer serves to insulate the molten glass from contact with the atmosphere in the furnace and to keep the molten glass warm. If the depth (thickness) of this bubble layer fluctuates, the temperature of the molten glass changes, which has a significant effect on the glass quality. For this reason, it is sometimes desirable to accurately measure the depth of the bubble layer.

[0010] An object of the present invention is to accurately measure the depth of molten glass stored in a glass melting furnace and the depth of a bubble layer formed on the molten glass. [Means for solving the problem]

[0011] The present invention, which has been invented to solve the above problems, is a glass depth measurement method for measuring the depth of molten glass stored in a glass melting furnace, and is characterized by comprising a bubble generating step of supplying compressed gas into the molten glass through a flow path member having a gas flow path opening into the molten glass in the glass melting furnace to generate bubbles, and a glass depth calculating step of determining the depth of the molten glass based on the air pressure in the gas flow path in a state in which bubbles have been generated.

[0012] In this way, there is a certain relationship between the air pressure in the gas flow path when bubbles are generated from the gas flow path and the depth of the molten glass. In detail, if the air pressure in the gas flow path when bubbles are generated from the gas flow path is P1, the air pressure in the space above the liquid surface of the molten glass in the glass melting furnace (air pressure in the furnace atmosphere) is P2, the density of the molten glass is ρ, and the gravitational acceleration is g, then the depth H of the molten glass is ρg...(1) is calculated by (P1-P2) / ρg...(1). Therefore, if the air pressure in the gas flow path with bubbles generated is measured, the depth of the molten glass can be easily and reliably calculated based on this. Even if the top of the molten glass is covered with a bubble layer, it is possible to generate bubbles inside the molten glass and measure the air pressure in the gas flow path at that time. In other words, the depth of the molten glass can be accurately measured even if a bubble layer is formed on the molten glass.

[0013] In the above-mentioned configuration, in the glass depth calculation step, it is preferable to obtain the depth of the molten glass based on the pressure difference between the air pressure in the gas flow passage in a state in which bubbles are generated and the atmospheric pressure.

[0014] In many cases, the atmospheric pressure in the furnace is substantially equal to the atmospheric pressure. Therefore, even if the atmospheric pressure in the furnace is not directly measured, the difference between the atmospheric pressure and the atmospheric pressure in the gas flow path in which bubbles are generated can be measured to indirectly determine (P1-P2) in the above formula (1). As a result, the depth of the molten glass can be accurately measured.

[0015] In the above configuration, it is preferable that the gas flow path opens to the molten glass with the flow path member penetrating the bottom wall or the side wall of the glass melting furnace below the liquid level of the molten glass.

[0016] That is, the flow path member may be inserted into the molten glass from the liquid surface of the molten glass, but in this case, the contact area between the flow path member and the molten glass becomes large. Therefore, there is a risk of problems such as the flow path member adversely affecting the flow of molten glass in the glass melting furnace, or foreign matter (e.g., reactants) resulting from thermal deterioration of the flow path member being mixed into the molten glass. In contrast, as described above, if the gas flow path is open to the molten glass while the flow path member penetrates the bottom wall or side wall of the glass melting furnace below the liquid surface of the molten glass, the occurrence of these problems can be suppressed.

[0017] In the above configuration, the flow path member may be a flow path member for supplying gas in a stirring device that generates bubbles for stirring the molten glass.

[0018] In other words, the glass melting furnace may be equipped with a stirring device that generates bubbles to stir the molten glass. Therefore, if a flow path member for supplying gas of an existing stirring device is used as the flow path member, an increase in equipment costs can be suppressed.

[0019] The present invention, which was devised to solve the above problems, is a foam layer depth measurement method for measuring the depth of a foam layer formed on molten glass in a glass melting furnace, and is characterized in that it comprises a glass depth measurement step for measuring the depth of the molten glass by the above glass depth measurement method, a total depth measurement step for measuring the total depth of the molten glass and the foam layer from above the foam layer, and a foam layer depth calculation step for calculating the depth of the foam layer from the difference between the total depth and the depth of the molten glass.

[0020] In this way, in the glass depth measuring step, for the reasons already described, the depth of the molten glass can be accurately measured even when a bubble layer is formed on the molten glass. Also, from above the bubble layer, the surface level of the bubble layer, which corresponds to the total depth of the molten glass and the bubble layer, can be easily observed. Therefore, in the total depth measuring step, the total depth of the molten glass and the bubble layer is measured from above the bubble layer. Then, in the bubble layer depth calculation step, the difference between the total depth measured in the total depth measuring step (depth of the molten glass + depth of the bubble layer) and the depth of the molten glass measured in the glass depth measuring step is calculated, whereby the depth of the bubble layer can be accurately measured.

[0021] In the above configuration, in the total depth measuring step, it is preferable to determine the total depth based on the positional relationship between a reference provided on a wall surface inside the melting furnace and the surface of the foam layer.

[0022] In this way, the total depth can be measured more accurately in the total depth measuring step, and as a result, the foam layer depth can be measured more accurately in the foam layer depth calculating step.

[0023] In the above configuration, in the total depth measuring step, it is preferable to determine the total depth based on the results of image processing of an image of the inside of the glass melting furnace captured by a camera positioned above the liquid surface of the molten glass.

[0024] In this manner, the total depth can be measured safely and accurately without coming into contact with the molten glass or the bubble layer.

[0025] The present invention, which has been invented to solve the above problems, is a glass melting furnace in which molten glass is stored inside the furnace, and is characterized by comprising a flow path member having a gas flow path that opens into the molten glass inside the furnace and guides compressed gas, a gas supply unit that supplies compressed gas to the gas flow path in order to generate bubbles in the molten glass, and a pressure measurement unit that measures the air pressure in the gas flow path while bubbles are generated.

[0026] In this way, it is possible to obtain the same effects as those of the corresponding configuration already described. Effect of the Invention

[0027] According to the present invention, the depth of molten glass stored in a glass melting furnace and the depth of a bubble layer formed on the molten glass can be accurately measured. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a cross-sectional view of a glass melting furnace according to a first embodiment of the present invention. [Diagram 2] FIG. 2A is a diagram showing an example of an image captured by a camera in a glass melting furnace, and FIG. 2B is a diagram showing an example of an image processing result of the image captured by the camera in the glass melting furnace. [Diagram 3] FIG. 3 is a cross-sectional view of a glass melting furnace according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view of a glass melting furnace according to a third embodiment of the present invention. [Diagram 5] FIG. 11 is a cross-sectional view of a glass melting furnace according to a fourth embodiment of the present invention. [Figure 6] FIG. 11 is a cross-sectional view of a glass melting furnace according to a fifth embodiment of the present invention. [Figure 7] FIG. 13 is a cross-sectional view of a glass melting furnace according to a modified example of the fifth embodiment of the present invention. [Figure 8] FIG. 11 is a cross-sectional view of a glass melting furnace according to a sixth embodiment of the present invention. [Figure 9] FIG. 13 is a cross-sectional view of a glass melting furnace according to a modified example of the sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In each embodiment, the same reference numerals are used to designate corresponding components, and duplicated descriptions may be omitted. When only a portion of a configuration is described in each embodiment, the configuration of another embodiment described above may be applied to the other portion of the configuration. In addition to the combination of configurations explicitly stated in the description of each embodiment, configurations of multiple embodiments may be partially combined together even if not explicitly stated, as long as there is no particular problem with the combination.

[0030] First embodiment The manufacturing apparatus for a glass article according to the first embodiment of the present invention is an apparatus for manufacturing glass fibers as a glass article. As shown in FIG. 1, the manufacturing apparatus includes a glass melting furnace 1 on the upstream side. Note that FIG. 1 is a cross-sectional view in a width direction perpendicular to the conveying direction (direction from the upstream side to the downstream side) of the molten glass Gm. Furthermore, although not shown, the manufacturing apparatus includes a forehearth connected to the glass melting furnace 1, a bushing provided at the bottom of the forehearth, and a plurality of nozzles provided on the bushing. The molten glass Gm stored in the forehearth is drawn downward from the plurality of nozzles and formed into glass fibers (monofilaments). Note that, after a bundling agent is applied to the surface of the glass fiber, 100 to 10,000 glass fibers may be bundled to form one strand. The strand may be wound to form a cake, or may be cut to a predetermined length to form chopped strands.

[0031] As shown in Fig. 1, the glass melting furnace 1 is a space for carrying out a melting step of melting glass raw material (which may include cullet) to continuously form molten glass Gm, and is provided with an outlet (not shown) for discharging the molten glass Gm at the downstream end. The glass melting furnace 1 defines a melting space within the furnace by walls made of firebricks (e.g., electrocast zirconia bricks, electrocast alumina bricks, electrocast alumina-zirconia bricks, electrocast AZS (Al-Zr-Si) bricks, dense fired bricks, etc.).

[0032] In this embodiment, the molten glass Gm is made of E glass (glass with an alkali content of 2% or less). The molten glass Gm is not limited to E glass, and may be, for example, D glass (low dielectric constant glass), AR glass (alkali resistant glass), C glass (acid resistant glass), M glass (high elasticity glass), S glass (high strength, high elasticity glass), T glass (high strength, high elasticity glass), H glass (high dielectric constant glass), NE glass (low dielectric constant glass), etc.

[0033] A plurality of rod-shaped electrodes (not shown) immersed in the molten glass Gm are provided on the bottom wall 1a of the glass melting furnace 1. These electrodes heat the molten glass Gm electrically. The heating method in the glass melting furnace 1 is not limited to the all-electric melting method, and may be, for example, a method of heating only by combustion of gas fuel (burner) from above the liquid surface LS of the molten glass Gm, or a method of heating by combining electrical heating and combustion of gas fuel.

[0034] The electrodes are not limited to rod-shaped, but may be plate-shaped or block-shaped, or may be a combination of these. The electrodes are not limited to being disposed on the bottom wall 1a, but may be disposed on the side wall 1b, or may be disposed on both the bottom wall 1a and the side wall 1b. Before and / or after the start of continuous melting, in order to indirectly heat the glass raw material and the molten glass Gm through the atmosphere in the glass melting furnace 1, a heating means such as a heater or a burner may be separately provided above the liquid level LS of the molten glass Gm.

[0035] Although not shown, the glass melting furnace 1 is provided with a charger at the supply port at the upstream end.

[0036] In this embodiment, the input device continuously supplies the glass frit so that the upstream side of the liquid surface LS of the molten glass Gm is covered with the glass frit. The downstream side of the liquid surface LS of the molten glass Gm is covered with a bubble layer Gb. That is, in the glass melting furnace 1, a part of the liquid surface LS of the molten glass Gm is covered with the glass frit. In addition, as the input device, a pusher, a vibration feeder, a screw feeder, etc. can be used.

[0037] The glass melting furnace 1 includes a flue 2 as an exhaust passage for discharging gas inside the furnace to the outside. A fan 3 for sending the gas to the outside is provided inside the flue 2. The flue 2 and / or the fan 3 may be omitted.

[0038] The glass melting furnace 1 is equipped with a glass depth measuring device 11 that measures the depth H1 of the molten glass Gm.

[0039] The glass depth measuring device 11 includes a flow path pipe 13 having a gas flow path 12 that opens into the molten glass Gm in the glass melting furnace 1 and guides the compressed gas CA, a gas supply unit 14 that supplies the compressed gas CA to the gas flow path 12 in order to generate bubbles B in the molten glass Gm, and a pressure measuring unit 15 that measures the air pressure in the gas flow path 12 while bubbles B are generated.

[0040] The flow path pipe 13 as a flow path member is disposed across the inside and outside of the glass melting furnace 1 by penetrating the bottom wall portion 1a of the glass melting furnace 1. The flow path pipe 13 forms a gas flow path 12 by the inner surface of the pipe. The tip of the flow path pipe 13 is in contact with the bottom base of the molten glass Gm. As a result, at the tip of the flow path pipe 13, the opening 12a of the gas flow path 12 facing upward is always open to the bottom base of the molten glass Gm. Note that the height position of the opening 12a of the gas flow path 12 is not particularly limited as long as it is disposed below the lower limit level of the liquid level LS of the molten glass Gm in the glass melting furnace 1 (the minimum depth of the molten glass Gm during operation). However, the depth H1 of the molten glass Gm is defined with the height position of the opening 12a of the gas flow path 12 being the zero level L0.

[0041] The gas supply unit 14 is connected to the base end of the flow path pipe 13 outside the glass melting furnace 1. The gas supply unit 14 is composed of, for example, a compressor. The gas supply unit 14 generates compressed gas (for example, compressed air) CA as a gas. The compressed gas CA generated by the gas supply unit 14 is supplied to the gas flow path 12 of the flow path pipe 13. When the supply pressure of the compressed gas CA from the gas supply unit 14 causes the air pressure P1 of the entire gas flow path 12 to become equal to or higher than a pressure corresponding to the depth H1 of the molten glass Gm, the compressed gas CA is ejected from the opening 12a as bubbles B.

[0042] In detail, the bubbles B erupt when the air pressure P1 in the gas flow passage 12 becomes substantially equal to the sum (P2+P3) of the air pressure P2 above the molten glass Gm in the glass melting furnace 1 and the air pressure P3 of the molten glass Gm at the height position of the opening 12a of the gas flow passage 12. In other words, the relationships of the following equations (2) to (4) hold between these pressures. Here, ρ is the density of the molten glass Gm, and g is the acceleration of gravity.

[0043] P1 = P2 + P3 … (2) P3 = ρgH1 … (3) H1 = (P1 - P2) / ρg … (4)

[0044] Therefore, by measuring the pressure difference (P1-P2) between the air pressure P1 in the gas flow path 12 and the air pressure P2 above the molten glass Gm in the glass melting furnace 1, the depth H1 of the molten glass Gm can be calculated from the above formula (4).

[0045] The pressure measuring unit 15 is configured with a differential pressure gauge (e.g., a gauge pressure gauge). Here, the air pressure P2 above the molten glass Gm in the glass melting furnace 1 is adjusted to be higher or lower than the atmospheric pressure PA. However, the difference between the air pressure P2 above the molten glass Gm and the atmospheric pressure PA is small, and the two can be considered to be substantially equal. Therefore, in this embodiment, the pressure measuring unit 15 is configured to measure the differential pressure (P1-PA) between the air pressure P1 in the gas flow path 12 and the atmospheric pressure PA, instead of measuring the differential pressure (P1-P2) between the air pressure P1 in the gas flow path 12 and the air pressure P2 above the molten glass Gm.

[0046] In detail, the atmospheric pressure PA outside the glass melting furnace 1 is introduced to the pressure measuring unit 15. Outside the glass melting furnace 1, the pressure measuring unit 15 is connected to a pressure guiding pipe 16 branched from the middle of the flow path pipe 13. The pressure guiding pipe 16 forms a pressure guiding flow path 17 by its inner surface. The pressure guiding flow path 17 is connected to the gas flow path 12. Thus, the pressure measuring unit 15 is adapted to introduce the atmospheric pressure P1 of the gas flow path 12 through the pressure guiding flow path 17. Therefore, the pressure measuring unit 15 measures the differential pressure (P1-PA) between the atmospheric pressure P1 of the gas flow path 12 and the atmospheric pressure PA. Since the differential pressure (P1-PA) is substantially equal to the differential pressure (P1-P2) between the atmospheric pressure P1 of the gas flow path 12 and the atmospheric pressure P2 above the molten glass Gm in the glass melting furnace 1, the depth H1 of the molten glass Gm can be calculated by the following formula (5).

[0047] H1 = (P1 - PA) / ρg … (5)

[0048] The glass depth measuring device 11 may include a calculation unit that automatically calculates the depth H1 of the molten glass Gm according to the above formula (5).

[0049] The glass melting furnace 1 is equipped with a bubble layer depth measuring device 21 for measuring the depth H2 of the bubble layer Gb.

[0050] The bubble layer depth measuring device 21 includes the above-mentioned glass depth measuring device 11, a camera 22, and an image processing unit .

[0051] The camera 22 is, for example, a CCD camera.

[0052] The camera 22 is disposed above the liquid level LS of the molten glass Gm outside the glass melting furnace 1. The camera 22 captures an image of the inside of the furnace through a sight window 24 provided in one side wall 1b of the glass melting furnace 1, and captures an image of the inside of the furnace. In this embodiment, as shown in FIG. 2(a), the camera 22 captures an image IM including at least a part of the side wall 1b of the other side of the glass melting furnace 1 facing the sight window 24, a reference 25 provided in the side wall 1b, and a bubble layer Gb formed on the molten glass Gm. The reference 25 is located above the upper limit level of the molten glass Gm in the glass melting furnace 1 (the maximum depth of the molten glass Gm during operation). The reference 25 is preferably a line (e.g., a horizontal line) parallel to the liquid level LS of the molten glass Gm in the glass melting furnace 1. The reference 25 is, for example, composed of a joint of the refractory bricks constituting the glass melting furnace 1, a scale provided on the side wall 1b, and the like.

[0053] The optical axis center A1 of the camera 22 is inclined downward from a position above the liquid surface LS of the molten glass Gm toward the liquid surface LS. The inclination angle θ of the optical axis center A1 with respect to the horizontal line A2 is preferably, for example, 5 to 10°.

[0054] The image processing unit 23 is disposed outside the glass melting furnace 1 and is connected to the camera 22. The image processing unit 23 is constituted by, for example, a personal computer.

[0055] 2(b), image processor 23 processes image IM captured by camera 22, for example, by binarization. From the result of processing image IM, distance H3 in the vertical direction from the surface of foam layer Gb to reference 25 can be easily and accurately calculated. Distance H3 may be an average value measured at multiple points.

[0056] Then, by using the vertical distance H3 from the surface of the bubble layer Gb to the reference 25 and the vertical distance H4 from the zero level L0 (height position of the opening 12a of the gas flow path 12) to the reference 25, the total depth H5 of the molten glass Gm and the bubble layer Gb can be calculated by the following formula (6). Note that the distance H4 is a known value (constant value) measured in advance.

[0057] H5=H4-H3…(6)

[0058] Furthermore, by using this total depth H5 and the depth H1 of the molten glass Gm, the depth H2 of the bubble layer Gb can be calculated by the following formula (7).

[0059] H2=H5-H1=H4-H3-H1…(7)

[0060] The foam layer depth measuring device 21 may include a calculation unit that automatically calculates the depth H2 of the foam layer Gb according to the above formula (7).

[0061] Hereinafter, a method for producing a glass article according to a first embodiment of the present invention will be described. This method is a method for producing glass fibers as a glass article by using the above-mentioned glass article production apparatus.

[0062] This manufacturing method includes a melting process (see FIG. 1) in which glass raw materials are melted in a glass melting furnace 1 to continuously form molten glass Gm, and a forming process in which the molten glass Gm stored in a forehearth connected to the glass melting furnace 1 is drawn out from a nozzle to form glass fibers.

[0063] Of these, the melting step further includes a glass depth measuring step of measuring a depth H1 of the molten glass Gm and a bubble layer depth measuring step of measuring a depth H2 of the bubble layer Gb, as shown in FIG.

[0064] The glass depth measuring step includes a bubble generating step and a glass depth calculating step.

[0065] In the bubble generating process, compressed gas CA is supplied by gas supply unit 14 into molten glass Gm through gas flow path 12 of flow path tube 13 to generate bubbles B in the molten glass Gm. In this manner, the relationship of formula (5) above is established between the pressure difference (P1-PA) between air pressure P1 in gas flow path 12 and atmospheric pressure PA in the state in which bubbles B have been generated, and the depth H1 of the molten glass Gm.

[0066] In the glass depth calculation step, the depth H1 of the molten glass Gm is obtained based on the differential pressure (P1-PA) between the atmospheric pressure PA and the air pressure P1 in the gas flow path 12 in a state in which the bubble B is generated. That is, the pressure measurement unit 15 measures the differential pressure (P1-PA) between the atmospheric pressure P1 in the gas flow path 12 in a state in which the bubble B is generated and the atmospheric pressure PA, and the depth H1 of the molten glass Gm is calculated from the formula (5).

[0067] In this way, when determining the depth H1 of the molten glass Gm, even if the surface of the molten glass Gm is covered with a bubble layer Gb, bubbles B can be generated inside the molten glass Gm, and the air pressure P1 in the gas flow path 12 at that time can be measured. Therefore, the depth of the molten glass Gm can be accurately measured without being hindered by the bubble layer Gb on the molten glass Gm.

[0068] The bubble layer depth measuring step includes the above-mentioned glass depth measuring step, a total depth measuring step, and a bubble layer depth calculating step.

[0069] In the glass depth measuring step, for the reasons already described, even when a bubble layer Gb is formed on the molten glass Gm, the depth of the molten glass Gm can be accurately measured.

[0070] In the total depth measurement step, the total depth H5 of the molten glass Gm and the foam layer Gb is measured based on the result of image processing of the image IM in the glass melting furnace 1 captured by the camera 22 arranged above the liquid surface LS of the molten glass Gm. In other words, from above the foam layer Gb, the surface level of the foam layer Gb corresponding to the total depth H5 of the molten glass Gm and the foam layer Gb can be easily observed by the camera 22. Therefore, in the total depth measurement step, the result of image processing of the image IM in the glass melting furnace 1 captured by the camera 22 arranged above the foam layer Gb is used to determine the vertical distance H3 from the foam layer Gb surface to the reference 25, and then the total depth H5 of the molten glass Gm and the foam layer Gb is calculated by the above formula (6).

[0071] In the bubble layer depth calculation step, as shown in the above formula (7), the difference between the total depth H5 measured in the total depth measurement step and the depth H1 of the molten glass Gm measured in the glass depth measurement step is obtained, and the depth H2 of the bubble layer Gb is calculated. In this way, the depth H2 of the bubble layer Gb can be accurately measured without directly contacting the molten glass Gm or the bubble layer Gb.

[0072] Second Embodiment 3 shows a second embodiment of the present invention. In this embodiment, in the glass depth measurement step, the pressure difference (P1-P2) between the air pressure P1 in the gas flow path 12 and the air pressure P2 above the molten glass Gm is measured, and the depth H1 of the molten glass Gm is calculated from the formula (4).

[0073] In detail, the pressure measuring unit 15 is a differential pressure gauge that measures the differential pressure (P1-P2) between the air pressure P1 in the gas flow path 12 and the air pressure P2 above the molten glass Gm.

[0074] A first pressure guiding tube 16 and a second pressure guiding tube 18 are connected to the pressure measuring unit 15 outside the glass melting furnace 1. The first pressure guiding tube 16 is the same as the pressure guiding tube 16 described in the first embodiment, and the first pressure guiding flow passage 17 is formed by the inner surface of the tube. The second pressure guiding tube 18 is disposed across the inside and outside of the glass melting furnace 1 by penetrating the upper wall portion 1c (in the illustrated example, the flue 2 of the upper wall portion 1c) of the glass melting furnace 1. The second pressure guiding tube 18 forms a second pressure guiding flow passage 19 by the inner surface of the tube. In the glass melting furnace 1, the second pressure guiding tube 18 is located above the upper limit level of the molten glass Gm so that the second pressure guiding flow passage 19 is always open above the molten glass Gm. As a result, the air pressure P2 is guided to the second pressure guiding flow passage 19 from above the molten glass Gm in the furnace of the glass melting furnace 1.

[0075] Therefore, the pressure measuring unit 15 is guided to the pressure measuring unit 15 by the air pressure P1 in the gas flow passage 12 through the first pressure conducting passage 17, and is guided to the pressure measuring unit 15 by the air pressure P2 above the molten glass Gm in the glass melting furnace 1 through the second pressure conducting passage 19. Thus, the pressure measuring unit 15 measures the differential pressure (P1-P2) between the air pressure P1 in the gas flow passage 12 and the air pressure P2 above the molten glass Gm. Then, the depth H1 of the molten glass Gm is calculated from the above formula (4).

[0076] Third embodiment 4 shows a third embodiment of the present invention. In this embodiment, a stirrer 31 provided in a glass melting furnace 1 is used as a glass depth measuring device 11 in a bubble generating step included in a glass depth measuring step.

[0077] The stirring device 31, like the glass depth measurement device 11 of the first embodiment, includes a flow path pipe 13, a gas supply unit 14, and a pressure measurement unit 15. Note that a typical stirring device does not include the pressure measurement unit 15 that measures the pressure difference (P1-PA) between the air pressure P1 in the gas flow path 12 and the atmospheric pressure PA, or the pressure difference (P1-P2) between the air pressure P1 in the gas flow path 12 and the air pressure P2 above the molten glass Gm. In other words, in this embodiment, in order to measure the depth H1 of the molten glass Gm, the pressure measurement unit 15 is separately provided in the existing stirring device 31.

[0078] The agitator 31 supplies compressed gas CA from the gas supply unit 14 to the gas flow path 12 of the flow path pipe 13, and ejects the compressed gas CA from the opening 12a of the gas flow path 12 as bubbles B. The bubbles B rise to the liquid surface LS of the molten glass Gm, forming an upward flow F1 in the molten glass Gm, and the molten glass Gm is agitated. This makes the quality of the molten glass Gm uniform. The gas flow path 12 of the agitator 31 is formed, for example, in the center of the front-rear direction (the conveying direction of the molten glass Gm) of the glass melting furnace 1 and in the center of the width direction (the direction perpendicular to the conveying direction).

[0079] In this state where bubbles B that stir the molten glass Gm are generated, pressure measurement unit 15 measures the pressure difference (P1-PA) between air pressure P1 in gas flow path 12 and atmospheric pressure PA. Then, depth H1 of molten glass Gm is calculated from formula (4) above. Note that pressure measurement unit 15 may be configured to measure the pressure difference (P1-P2) between air pressure P1 in gas flow path 12 and air pressure P2 above molten glass Gm, similar to pressure measurement unit 15 described in the second embodiment.

[0080] (Fourth embodiment) FIG. 5 shows a fourth embodiment of the present invention. In this embodiment, the flow path pipe 13 is disposed across the inside and outside of the glass melting furnace 1 by penetrating the side wall 1b instead of the bottom wall 1a of the glass melting furnace 1. As a result, when the height position of the opening 12a of the gas flow path 12 changes from the height position of the opening 12a of the gas flow path 12 when the flow path pipe 13 is provided to penetrate the bottom wall 1a, the zero level L0, which is the reference of the depth H1 of the molten glass Gm, is also changed. Note that FIG. 5 illustrates a state in which the zero level L0 is changed from the bottom wall 1a. Even in this case, since the height difference between the bottom wall 1a and the height position of the opening 12a of the gas flow path 12 can be measured in advance, the depth of the molten glass Gm based on the bottom wall 1a can be obtained from the depth H1 of the molten glass Gm.

[0081] When the flow passage pipe 13 penetrates the side wall portion 1b as in the fourth embodiment, the maintainability is improved compared to when the flow passage pipe 13 penetrates the bottom wall portion 1a. This effect is particularly noticeable when electrodes are disposed on the bottom wall portion 1a.

[0082] Fifth embodiment 6 and 7 show a fifth embodiment of the present invention. In this embodiment, from the viewpoint of reducing the influence of convection of the molten glass Gm along the bottom wall 1a or the side wall 1b, the tip of the flow path pipe 13 has a protruding portion 13a protruding from the bottom wall 1a (see FIG. 6) or the side wall 1b (see FIG. 7).

[0083] Sixth embodiment 8 and 9 show a sixth embodiment of the present invention. In this embodiment, the protruding portion 13a of the flow tube 13 protruding from the bottom wall portion 1a or the side wall portion 1b has a bent portion 13b. For example, as shown in FIG. 8, when the flow tube 13 penetrates the bottom wall portion 1a, the tip of the protruding portion 13a may extend horizontally by the bent portion 13b. In this way, the glass frit is less likely to enter the flow tube 13 when the melting furnace 1 is started up, and the effect of suppressing the blockage of the flow tube 13 by the glass frit can be expected. Also, for example, as shown in FIG. 9, when the flow tube 13 penetrates the side wall portion 1b, the tip of the protruding portion 13a may extend upward or downward (upward in the illustrated example) by the bent portion 13b. If the tip of the protruding portion 13a extends downward, the glass frit is less likely to enter the flow tube 13 when the melting furnace 1 is started up, and the effect of suppressing the blockage of the flow tube 13 by the glass frit can be expected.

[0084] The present invention is not limited to the configuration of the above embodiment, nor is it limited to the above-mentioned effects and advantages. Various modifications of the present invention are possible without departing from the spirit and scope of the present invention.

[0085] In the above embodiment, the method of measuring the depth H1 of the molten glass Gm in a state where the bubble layer Gb is formed on the molten glass Gm is illustrated, but the glass depth measuring method according to the present invention can also be applied to a case where there is no bubble layer Gb. That is, the glass depth measuring method according to the present invention can also be applied to a case where the liquid surface LS of the molten glass Gm is exposed in the glass melting furnace 1, or a case where the entire liquid surface LS of the molten glass Gm is covered with glass raw material, for example.

[0086] In the above embodiment, an absolute pressure gauge may be used as the pressure measurement unit 15. In this case, the atmospheric pressure measured in advance is subtracted from the measurement value of the pressure measurement unit 15. This gives (P1-PA) in equation (5).

[0087] In the above embodiment, when determining the vertical distance H3 from the surface of the foam layer Gb to the reference 25, the image IM captured by the camera 22 may include two or more references 25 whose vertical separation distance is known, and the distance H3 may be corrected based on the difference between the measured value from the image IM of the separation distance between each reference 25 and the known value (constant value). Alternatively, the distance H3 may be corrected based on the inclination angle θ of the optical axis center A1 of the camera 22. In this way, the optical axis center A1 of the camera 22 may be adjusted to the inclination angle θ of the optical axis center A1 of the camera 22. This can correct errors caused by image distortion due to the tilt of 1.

[0088] In the above embodiment, the total depth H5 of the molten glass Gm and the bubble layer Gb is measured based on the reference 25 provided in the glass melting furnace 1, but the method of measuring the total depth H5 is not limited to this. For example, the total depth H5 may be measured based on the position (e.g., height position) and angle (e.g., inclination angle θ of the optical axis center A1) of the camera 22 provided outside the glass melting furnace 1. However, there is a risk that the measured value of the total depth H5 will change significantly if the position or angle of the camera 22 changes slightly. Therefore, from the viewpoint of improving the measurement accuracy, it is preferable to measure the total depth H5 using the reference 25 provided in the glass melting furnace 1.

[0089] In the above embodiment, an example was given of measuring the total depth H5 of the molten glass Gm and the bubble layer Gb using camera 22, but the total depth H5 may also be measured by an operator directly reading a scale or the like without using camera 22.

[0090] In the above embodiment, the case where glass fiber is produced as the glass article is exemplified, but a plate glass or a glass roll may be produced as the glass article. In this case, the molten glass Gm may be, for example, alkali-free glass, soda glass, soda lime glass, borosilicate glass, aluminosilicate glass, alkali-containing glass, or the like. [Explanation of symbols]

[0091] 1 Glass melting furnace 11 Glass depth measuring device 12 Gas flow path 13 Flow pipe 14 Gas supply section 15 Pressure measurement section 21 Foam layer depth measuring device 22 Camera 23 Image processing section 25 Criteria B. Air bubbles CA Compressed Gas Gb foam layer Gm Molten Glass

Claims

1. A method for measuring the depth of a bubble layer formed on molten glass in a glass melting furnace, comprising: a bubble generating step of supplying compressed gas into the molten glass through a flow path member having a gas flow path opening into the molten glass in the glass melting furnace to generate bubbles; a glass depth calculation step of determining a depth of the molten glass based on the air pressure in the gas flow path in a state in which the bubbles are generated; A total depth measuring step of measuring a total depth of the molten glass and the bubble layer from above the bubble layer; A bubble layer depth calculation step of calculating the bubble layer depth from the difference between the total depth and the depth of the molten glass, In the total depth measuring step, the total depth is calculated based on a result of image processing of an image of the inside of the glass melting furnace captured by a camera arranged above the liquid surface of the molten glass, A method for measuring a foam layer depth, characterized in that the image includes at least a portion of the foam layer.

2. The bubble layer depth measuring method according to claim 1 , wherein in the glass depth calculating step, the depth of the molten glass is calculated based on a pressure difference between the air pressure in the gas flow path in a state in which the bubbles are generated and atmospheric pressure.

3. The bubble layer depth measuring method according to claim 1 or 2, wherein the gas flow path is open to the molten glass while the flow path member penetrates the bottom wall or side wall of the glass melting furnace below the liquid level of the molten glass.

4. The bubble layer depth measuring method according to any one of claims 1 to 3, wherein the flow path member is a flow path member for gas supply in a stirring device that generates bubbles to stir the molten glass.

5. The foam layer depth measuring method according to any one of claims 1 to 4, wherein in the total depth measuring step, the total depth is obtained based on the positional relationship between the reference provided on the wall surface of the glass melting furnace and the surface of the foam layer.

6. A glass melting furnace in which molten glass is stored, a flow path member having a gas flow path opening into the molten glass in the furnace and guiding a compressed gas; a gas supply unit that supplies the compressed gas to the gas flow path to generate bubbles in the molten glass; a pressure measuring unit that measures the air pressure in the gas flow path while the air bubbles are generated; A glass melting furnace comprising: a camera disposed above the liquid surface of the molten glass and configured to capture an image including at least a portion of a bubble layer formed on the molten glass.

Images