JP7602725B2 - Glass depth measuring method, bubble layer depth measuring method, and glass melting furnace - Google Patents

Description

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

The manufacturing method of glass products such as glass fiber and flat glass includes a melting process in which glass raw materials are melted in a glass melting furnace to form molten glass that is the basis of the glass products.

Glass melting furnaces that melt glass raw materials by gas combustion are widely used, but there are also cases where glass raw materials are melted only by electrical heating (see, for example, Patent Document 1).

In addition, in a glass melting furnace, in order to homogenize the molten glass and stabilize the amount of molten glass that flows out, it is necessary to operate the furnace while keeping the depth of the molten glass stored there constant.

For example, Patent Document 2 discloses that in a glass melting furnace 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.

JP 2003-183031 A International Publication No. 2013/021771

However, 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 that melts glass raw materials only by electric heating, there is often no heating means above the liquid surface of the molten glass, and a bubble layer is easily 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 glass raw materials and _SO2 gas generated by decomposition of sulfates added as a fining agent.

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, the bubble layer can get in the way and make it difficult to accurately measure the depth of the molten glass.

On the other hand, the bubble layer serves to insulate the molten glass from contact with the atmosphere inside the furnace and thus 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 impact on the glass quality. For this reason, it is sometimes desirable to accurately measure the depth of the bubble layer.

The objective of the present invention is to accurately measure the depth of the molten glass stored in a glass melting furnace and the depth of the bubble layer formed on the molten glass.

The present invention, which was 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 generation process in which compressed gas is supplied 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 calculation process in which the depth of the molten glass is calculated based on the air pressure of the gas flow path in the state in which the bubbles have been generated.

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 in which bubbles are generated is measured, the depth of the molten glass can be easily and reliably calculated based on the measured air pressure. Even if the top of the molten glass is covered with a bubble layer, it is possible to generate air bubbles inside the molten glass and measure the air pressure in the gas flow path at that time. In other words, even if a bubble layer is formed on the molten glass, the depth of the molten glass can be accurately measured.

In the above configuration, in the glass depth calculation process, it is preferable to find the depth of the molten glass based on the pressure difference between the air pressure in the gas flow path when bubbles are generated and the atmospheric pressure.

The atmospheric pressure inside the furnace is often substantially equal to atmospheric pressure. Therefore, even if the atmospheric pressure inside the furnace is not measured directly, it is possible to indirectly determine (P1 - P2) in equation (1) above by measuring the pressure difference between the atmospheric pressure and the atmospheric pressure in the gas flow path when bubbles are generated. As a result, the depth of the molten glass can be measured accurately.

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

In other words, 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. This may cause 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 flow path member penetrates the bottom wall or side wall of the glass melting furnace below the liquid surface of the molten glass and the gas flow path is open to the molten glass, these problems can be prevented.

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

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

The present invention, which was invented to solve the above problems, is a bubble layer depth measurement method for measuring the depth of a bubble layer formed on molten glass in a glass melting furnace, and is characterized by comprising 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 bubble layer from above the bubble layer, and a bubble layer depth calculation step for calculating the depth of the bubble layer from the difference between the total depth and the depth of the molten glass.

In this way, in the glass depth measurement process, for the reasons already mentioned, the depth of the molten glass can be accurately measured even if a bubble layer is formed on the molten glass. Furthermore, 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 measurement process, 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 process, the difference between the total depth measured in the total depth measurement process (depth of molten glass + depth of bubble layer) and the depth of the molten glass measured in the glass depth measurement process is calculated, and the depth of the bubble layer can be accurately measured.

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

In this way, the total depth can be measured more accurately in the total depth measurement process, and as a result, the foam layer depth can be measured more accurately in the foam layer depth calculation process.

In the above configuration, in the total depth measurement process, 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.

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

The present invention, which was invented to solve the above problems, is a glass melting furnace in which molten glass is stored, and is characterized by comprising a flow path member having a gas flow path that opens into the molten glass in the furnace and guides compressed gas, a gas supply unit that supplies compressed gas to the gas flow path 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.

In this way, the same effects as those of the corresponding configurations already described can be obtained.

The present invention makes it possible to accurately measure the depth of the molten glass stored in a glass melting furnace and the depth of the bubble layer formed on the molten glass.

FIG. 1 is a cross-sectional view of a glass melting furnace according to a first embodiment of the present invention. 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. FIG. 3 is a cross-sectional view of a glass melting furnace according to a second embodiment of the present invention. FIG. 4 is a cross-sectional view of a glass melting furnace according to a third embodiment of the present invention. FIG. 11 is a cross-sectional view of a glass melting furnace according to a fourth embodiment of the present invention. FIG. 11 is a cross-sectional view of a glass melting furnace according to a fifth embodiment of the present invention. 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. FIG. 11 is a cross-sectional view of a glass melting furnace according to a sixth embodiment of the present invention. 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.

Embodiments of the present invention will be described below with reference to the attached drawings. Note that in each embodiment, corresponding components are given the same reference numerals, and duplicated descriptions may be omitted. When only a portion of a configuration is described in each embodiment, the configuration of another previously described embodiment may be applied to the other portions of the configuration. In addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of multiple embodiments may be partially combined together even if not explicitly stated, provided that there is no particular problem with the combination.

First Embodiment
The glass article manufacturing apparatus according to the first embodiment of the present invention is an apparatus for manufacturing glass fibers as glass articles. As shown in FIG. 1, the manufacturing apparatus includes a glass melting furnace 1 on the upstream side. 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). 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.

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

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.

The bottom wall 1a of the glass melting furnace 1 is provided with a number of rod-shaped electrodes (not shown) immersed in the molten glass Gm. 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.

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

Although not shown in the figure, the glass melting furnace 1 is equipped with a feeder at the supply port at the upstream end.

In this embodiment, the feeder continuously supplies glass raw material so that the upstream side of the liquid surface LS of the molten glass Gm is covered with the glass raw material. The downstream side of the liquid surface LS of the molten glass Gm is covered with a bubble layer Gb. In other words, in the glass melting furnace 1, a part of the liquid surface LS of the molten glass Gm is covered with the glass raw material. Note that a pusher, a vibration feeder, a screw feeder, or the like can be used as the feeder.

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

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

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.

The flow path tube 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 tube 13 forms a gas flow path 12 with the inner surface of the tube. The tip of the flow path tube 13 is in contact with the bottom base of the molten glass Gm. As a result, at the tip of the flow path tube 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 as the height position of the opening 12a of the gas flow path 12 being the zero level L0.

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, 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 exceed the pressure corresponding to the depth H1 of the molten glass Gm, the compressed gas CA is ejected from the opening 12a as bubbles B.

In detail, bubbles B are ejected when the air pressure P1 in the gas flow path 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 path 12. In other words, the relationship between these pressures is expressed by the following equations (2) to (4). Here, ρ is the density of the molten glass Gm, and g is the acceleration of gravity.

P1=P2+P3...(2)
P3=ρgH1...(3)
H1=(P1-P2)/ρg...(4)

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).

The pressure measurement 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 slight, and the two can be considered to be substantially equal. Therefore, in this embodiment, the pressure measurement 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.

In detail, the pressure measuring unit 15 is adapted to receive the atmospheric pressure PA outside the glass melting furnace 1. The pressure measuring unit 15 is connected to a pressure guiding pipe 16 that branches off from the middle of the flow path pipe 13 outside the glass melting furnace 1. The pressure guiding pipe 16 forms a pressure guiding flow path 17 with its inner surface. The pressure guiding flow path 17 is connected to the gas flow path 12. As a result, the pressure measuring unit 15 is adapted to receive 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).

H1=(P1-PA)/ρg...(5)

The glass depth measuring device 11 may also be equipped with a calculation unit that automatically calculates the depth H1 of the molten glass Gm according to the above formula (5).

The glass melting furnace 1 is equipped with a bubble layer depth measuring device 21 that measures the depth H2 of the bubble layer Gb.

The bubble layer depth measuring device 21 includes the above-mentioned glass depth measuring device 11, a camera 22, and an image processing unit 23.

Camera 22 is composed of, for example, a CCD camera.

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, etc.

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°.

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 composed of, for example, a personal computer.

As shown in FIG. 2(b), the image processing unit 23 processes the image IM acquired by the camera 22, for example by binarization. From the result of image processing of the image IM, the vertical distance H3 from the surface of the foam layer Gb to the reference 25 can be easily and accurately determined. The distance H3 may be the average value measured at multiple points.

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 (the 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.

H5=H4-H3...(6)

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 using the following formula (7).

H2=H5-H1=H4-H3-H1...(7)

The foam layer depth measuring device 21 may also be equipped with a calculation unit that automatically calculates the depth H2 of the foam layer Gb according to the above formula (7).

The following describes a method for manufacturing a glass article according to the first embodiment of the present invention. This manufacturing method is a method for manufacturing glass fiber as a glass article using the above-mentioned glass article manufacturing apparatus.

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.

In the melting process, as shown in FIG. 1, a glass depth measurement process is further carried out to measure the depth H1 of the molten glass Gm, and a bubble layer depth measurement process is further carried out to measure the depth H2 of the bubble layer Gb.

The glass depth measurement process includes a bubble generation process and a glass depth calculation process.

In the bubble generation process, the gas supply unit 14 supplies compressed gas CA into the molten glass Gm through the gas flow path 12 of the flow path tube 13, generating bubbles B in the molten glass Gm. In this way, the relationship of the above formula (5) is established between the pressure difference (P1-PA) between the air pressure P1 in the gas flow path 12 and the atmospheric pressure PA in the state in which bubbles B are generated, and the depth H1 of the molten glass Gm.

In the glass depth calculation process, the depth H1 of the molten glass Gm is calculated based on the pressure difference (P1-PA) between the atmospheric pressure PA and the air pressure P1 in the gas flow path 12 when the bubble B is generated. That is, the pressure measurement unit 15 measures the pressure difference (P1-PA) between the atmospheric pressure P1 in the gas flow path 12 when the bubble B is generated and the atmospheric pressure PA, and calculates the depth H1 of the molten glass Gm from formula (5).

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 top of the molten glass Gm.

The bubble layer depth measurement process includes the above-mentioned glass depth measurement process, a total depth measurement process, and a bubble layer depth calculation process.

For the reasons already mentioned, in the glass depth measurement process, the depth of the molten glass Gm can be accurately measured even if a bubble layer Gb has formed on the molten glass Gm.

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

In the bubble layer depth calculation process, as shown in the above formula (7), the difference between the total depth H5 measured in the total depth measurement process and the depth H1 of the molten glass Gm measured in the glass depth measurement process is calculated, 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 direct contact with the molten glass Gm or the bubble layer Gb.

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).

In detail, the pressure measuring unit 15 is a differential pressure gauge that measures 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.

The pressure measuring unit 15 is connected to a first pressure guiding tube 16 and a second pressure guiding tube 18 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 path 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 path 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 path 19 is always open above the molten glass Gm. As a result, the air pressure P2 is guided to the second pressure guiding flow path 19 from above the molten glass Gm in the furnace of the glass melting furnace 1.

Therefore, the pressure measurement unit 15 is guided to the air pressure P1 in the gas flow path 12 through the first pressure guide path 17, and is guided to the air pressure P2 above the molten glass Gm in the glass melting furnace 1 through the second pressure guide path 19. In this way, the pressure measurement unit 15 measures 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. Then, the depth H1 of the molten glass Gm is calculated from the above formula (4).

Third Embodiment
4 shows a third embodiment of the present invention. In this embodiment, a stirring device 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.

The stirring device 31, like the glass depth measuring device 11 of the first embodiment, includes a flow path pipe 13, a gas supply unit 14, and a pressure measuring unit 15. Note that a typical stirring device does not include a pressure measuring 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, a pressure measuring unit 15 is separately provided in the existing stirring device 31 to measure the depth H1 of the molten glass Gm.

The stirring device 31 supplies compressed gas CA from the gas supply unit 14 to the gas flow path 12 of the flow path tube 13, and ejects the compressed gas CA from the opening 12a of the gas flow path 12 as bubbles B. When the bubbles B rise to the liquid surface LS of the molten glass Gm, an upward flow F1 is formed in the molten glass Gm, and the molten glass Gm is stirred. This makes the quality of the molten glass Gm uniform. The gas flow path 12 of the stirring device 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).

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

(Fourth embodiment)
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.

If the flow passage pipe 13 penetrates the side wall portion 1b as in the fourth embodiment, maintenance is improved compared to when it penetrates the bottom wall portion 1a. This effect is particularly noticeable when the electrode is placed on the bottom wall portion 1a.

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 portion 1 a or the side wall portion 1 b, the tip of the flow path pipe 13 has a protruding portion 13 a protruding from the bottom wall portion 1 a (see FIG. 6 ) or the side wall portion 1 b (see FIG. 7 ).

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.

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

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

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).

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 distances are 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 corrected based on the inclination angle θ of the optical axis center A1 of the camera 22.
This allows for correction of errors due to image distortion associated with the inclination of 1.

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 installed inside 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 installed outside the glass melting furnace 1. However, even a slight change in the position or angle of the camera 22 may cause the measured value of the total depth H5 to change significantly. Therefore, from the viewpoint of improving the measurement accuracy, it is preferable to measure the total depth H5 using the reference 25 installed inside the glass melting furnace 1.

In the above embodiment, the camera 22 is used to measure the total depth H5 of the molten glass Gm and the bubble layer Gb, but the total depth H5 may be measured by an operator directly reading a scale or the like without using the camera 22.

In the above embodiment, the case of producing glass fiber as the glass article is exemplified, but a glass plate 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, etc.

Reference Signs List 1 Glass melting furnace 11 Glass depth measuring device 12 Gas flow path 13 Flow path pipe 14 Gas supply unit 15 Pressure measuring unit 21 Bubble layer depth measuring device 22 Camera 23 Image processing unit 25 Reference B Bubble CA Compressed gas Gb Bubble layer Gm Molten glass

Claims (6)

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 . 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. 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. 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. 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. 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 .

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