JP7753793B2 - Float glass manufacturing device and float glass manufacturing method - Google Patents

Description

This disclosure relates to a float glass manufacturing apparatus and a float glass manufacturing method.

Float glass manufacturing equipment continuously supplies molten glass onto molten metal in a bath, causing the molten glass to flow over the molten metal and form the molten glass into a band-like glass ribbon. After the glass ribbon is slowly cooled, both ends of the glass ribbon in the width direction are cut off to obtain float glass. Float glass is used for glass substrates for flat panel displays (FPDs), etc.

Patent Document 1 describes that the bathtub comprises a box-shaped metal casing and multiple bricks placed inside the metal casing, that joints are formed between the multiple bricks, that molten metal flows into the joints, and that a cooling nozzle sprays air or the like onto the underside of the metal casing to suppress reaction between the molten metal and the metal casing. Similar content to Patent Document 1 is also disclosed in Patent Documents 2 to 4.

Japanese Patent Application Laid-Open No. 2019-94222 JP 2016-147786 A JP 2015-124123 A International Publication No. 2012/060197

One aspect of the present disclosure provides technology that improves the cooling efficiency of the casing.

A float glass manufacturing apparatus according to one aspect of the present disclosure includes a bath containing molten metal, continuously supplies molten glass onto the molten metal in the bath, and forms the supplied molten glass into a band-shaped glass ribbon while flowing over the molten metal. The bath includes a plurality of bricks in contact with the molten metal and a box-shaped casing that contains the plurality of bricks. The float glass manufacturing apparatus also includes a nozzle that sprays a refrigerant toward the outer surface of the casing, and a heat sink having a plurality of fins. The heat sink is attached to the outer surface of the casing.

According to one aspect of the present disclosure, the cooling efficiency of the casing can be improved by attaching a heat sink to the outer surface of the casing.

FIG. 1 is a cross-sectional view of a float glass manufacturing apparatus according to one embodiment. FIG. 2 is a cross-sectional view showing an example of a bathtub. FIG. 3 is a view showing an example of the arrangement of the bottom casing, the nozzle outlet, and the heat sink. FIG. 4 is a perspective view showing an example of the structure of a heat sink. FIG. 5 is a perspective view showing a modified example of the heat sink structure. FIG. 6 is a view showing an example of a view through the bottom casing and a flow path of the coolant formed between adjacent fins.

Embodiments of the present disclosure will be described below with reference to the drawings. Note that identical or corresponding components in each drawing will be assigned the same reference numerals, and descriptions thereof may be omitted. In each drawing, the X-axis direction, Y-axis direction, and Z-axis direction are perpendicular to one another. The X-axis direction is the flow direction of the glass ribbon GR, and the Y-axis direction is the width direction of the glass ribbon GR. The X-axis direction and Y-axis direction are horizontal directions, and the Z-axis direction is vertical. In the specification, the symbol "to" indicating a numerical range means that the numerical values before and after it are included as the lower and upper limits.

As shown in Figures 1 and 2, the float glass manufacturing apparatus 1 continuously supplies molten glass G onto molten metal M in a bath 10, and forms the supplied molten glass G into a strip-shaped glass ribbon GR while flowing over the molten metal M. The glass ribbon GR is pulled up from the molten metal M in the downstream region of the bath 10, then slowly cooled in an annealing device (not shown), and cut to a predetermined size by a processing device (not shown). The processing device cuts off both widthwise ends of the glass ribbon GR. The glass ribbon GR is processed by the processing device to obtain the product float glass.

Float glass is, for example, alkali-free glass, aluminosilicate glass, borosilicate glass, soda-lime glass, etc. Alkali-free glass means glass that does not substantially contain alkali metal oxides such as Na ₂ O and K ₂ O. Here, "substantially not containing alkali metal oxides" means that the total content of alkali metal oxides is 0.1 mass% or less.

Float glass can be used for, but is not limited to, purposes such as cover glass for displays (such as liquid crystal displays or organic EL displays). When float glass is used as cover glass, it is chemically strengthened glass. Unlike alkali-free glass, chemically strengthened glass contains alkali metal oxides.

The thickness of float glass is selected depending on its intended use. If the float glass is intended for use as a display cover glass, the thickness is, for example, 0.1 mm to 2.0 mm. If the float glass is intended for use as a display glass substrate, the thickness is, for example, 0.1 mm to 0.7 mm. If the float glass is intended for use as an automobile windshield, the thickness is, for example, 0.2 mm to 3.0 mm.

The float glass manufacturing apparatus 1 includes a bath 10. The bath 10 contains molten metal M. The molten metal M may be, for example, molten tin. In addition to molten tin, molten tin alloys may also be used, and the molten metal M may be any metal with a higher density than the molten glass G. The bath 10 includes a plurality of bricks 12, 13 that come into contact with the molten metal M, and a box-shaped casing 11 that contains the plurality of bricks 12, 13.

The casing 11 is made, for example, by welding metal plates together. The casing 11 contains a magnetic material such as iron. The casing 11 includes a bottom casing 111 and a side casing 112. The bottom casing 111 is arranged horizontally, and the side casing 112 is arranged vertically. The side casing 112 protrudes upward from the periphery of the bottom casing 111.

Multiple bricks 12, 13 are placed on the bottom casing 111. The bricks 12 are arranged in a frame shape along the side casing 112. These bricks 12 are also called side bricks 12. The remaining bricks 13 are also called bottom bricks 13. The side bricks 12 protrude higher than the bottom bricks 13 and protrude above the liquid surface of the molten metal M. The bottom bricks 13 are located below the liquid surface of the molten metal M.

The float glass manufacturing apparatus 1 includes a spout lip 14 and a tweel 15. The spout lip 14 supplies molten glass G onto the molten metal M in the bath 10. The tweel 15 adjusts the flow rate of the molten glass G flowing over the spout lip 14. A protective film 16 may be formed on the tweel 15 to prevent contact between the tweel 15 and the molten glass G. The protective film 16 is formed of, for example, platinum or a platinum alloy.

The float glass manufacturing apparatus 1 has a ceiling 17 above the bath 10. The space between the bath 10 and the ceiling 17 is filled with reducing gas and maintained at a pressure higher than atmospheric pressure to prevent oxidation of the molten metal M. The reducing gas is, for example, a mixture of nitrogen gas and hydrogen gas, containing 85% to 98.5% by volume of nitrogen gas and 1.5% to 15% by volume of hydrogen gas. The reducing gas is supplied through the joints between the bricks in the ceiling 17 and through holes in the ceiling 17.

The float glass manufacturing apparatus 1 is equipped with top rolls 18. The top rolls 18 rotate while pressing the widthwise ends of the glass ribbon GR, and feed out the glass ribbon GR. A pair of top rolls 18 are provided on both sides of the glass ribbon GR in the widthwise direction, and suppress shrinkage of the glass ribbon GR in the widthwise direction. The thickness of the glass ribbon GR can be made thinner than the equilibrium thickness. Although not shown, multiple pairs of top rolls 18 are provided at intervals in the flow direction of the glass ribbon GR.

The float glass manufacturing apparatus 1 is equipped with a heater 19. The heater 19 is suspended from the ceiling 17 and heats the glass ribbon GR passing below. The heater 19 is an electric heater that is heated by passing electricity through it. The heater 19 is, for example, a SiC heater. Multiple heaters 19 are arranged in a matrix in the flow direction and width direction of the glass ribbon GR. By controlling the output of the multiple heaters 19, the temperature distribution of the glass ribbon GR can be controlled, and the thickness distribution of the glass ribbon GR can also be controlled.

Joints 21 are formed between adjacent bottom bricks 13. Joints 22 are also formed between adjacent bottom bricks 13 and side bricks 12. Joints 23 are also formed between adjacent side bricks 12 (see Figure 3). Molten metal M flows into these joints 21, 22, and 23. The molten metal M passes through the joints 21, 22, and 23 and may reach the casing 11.

The float glass manufacturing apparatus 1 is therefore equipped with a nozzle 30. The nozzle 30 cools the casing 11 by spraying a refrigerant toward the outer surface of the casing 11, thereby suppressing a reaction between the casing 11 and the molten metal M. The refrigerant, for example, cools the temperature of the casing 11 to a temperature lower than the melting point of the molten metal M, solidifying the molten metal M that has reached the casing 11. The refrigerant is, for example, air. The refrigerant may also be water or a mixture of air and water.

The nozzle 30 has, for example, an injection port 31 below the bottom casing 111 that injects the coolant directly upward toward the underside 111a of the bottom casing 111. The injection port 31 injects the coolant toward, for example, the joints 21 between adjacent bottom bricks 13, or the joints 22 between adjacent bottom bricks 13 and side bricks 12. The coolant can efficiently cool the joints 21, 22, which are the path through which the molten metal M passes, reducing the amount of coolant used.

At least one injection port 31 may inject the coolant toward the joint 21 or 22. Note that after passing through the joints 21 and 22, the molten metal M spreads along the bottom casing 111. Therefore, the injection port 31 may inject the coolant not toward the joints 21 and 22, but toward the molten metal M that has passed through the joints 21 and 22 and spreads out laterally from the joints 21 and 22.

Although not shown, the nozzle 30 may have an injection port on the side of the side casing 112 that injects the coolant directly toward the outward side surface 112a of the side casing 112. The injection port injects the coolant toward the joints 23 between adjacent side bricks 12, for example. The coolant can efficiently cool the joints 23, which are the path for the molten metal M, thereby reducing the amount of coolant used.

At least one injection port may inject the coolant toward the joint 23. After passing through the joint 23, the molten metal M spreads along the side casing 112. Therefore, the injection port may inject the coolant not toward the joint 23, but toward the molten metal M that has passed through the joint 23 and spread out laterally from the joint 23.

The float glass manufacturing apparatus 1 is equipped with a heat sink 40. The heat sink 40 is attached to the outer surface of the casing 11. For example, the heat sink 40 is attached to the lower surface 111a of the bottom casing 111. Although not shown, the heat sink 40 may also be attached to the outward-facing side surface 112a of the side casing 112.

The heat sink 40 is attached to the outer surface of the casing 11 to release heat from the casing 11 and improve the cooling efficiency of the casing 11. To further improve the cooling efficiency, the nozzle 30 may eject a coolant toward the heat sink 40. The coolant absorbs heat from the casing 11 via the heat sink 40 and cools the casing 11.

As shown in Figure 4, the heat sink 40 has multiple fins 41. The fins 41 increase the surface area that dissipates heat, improving heat dissipation efficiency. The fins 41 may be rod-shaped or plate-shaped. The plate shape may be either flat or corrugated.

The heat sink 40 may have a base plate 42 that supports multiple fins 41. Heat from the casing 11 is transferred from the casing 11 to the multiple fins 41 via the base plate 42 and is dissipated from the multiple fins 41. The fins 41 protrude from the base plate 42 in a direction perpendicular to the outer surface of the casing 11, for example, in a direction perpendicular to the underside of the bottom casing 111 (Z-axis direction).

The length L of the fins 41 in the direction perpendicular to the outer surface of the casing 11 is, for example, 75 mm or more. If the length L of the fins 41 is 75 mm or more, heat dissipation efficiency is good. From the perspective of heat dissipation efficiency, the length L is preferably 100 mm or more, and more preferably 150 mm or more. However, from the perspective of miniaturizing the heat sink 40, the length L is preferably 75 mm to 100 mm.

Although not shown, the float glass manufacturing apparatus 1 may include a heat-dissipating paint applied to the heat sink 40. The heat-dissipating paint is applied to the heat-dissipating surface of the heat sink 40, for example, the fins 41. The heat-dissipating paint may also be applied to the base plate 42. The heat-dissipating paint improves heat dissipation efficiency, for example, by utilizing thermal radiation. The emissivity of the heat-dissipating paint is, for example, 0.90 to 0.95. The emissivity is measured in accordance with Japanese Industrial Standard JIS A1423:2017. The heat-dissipating paint may contain, for example, carbon black.

The means for fixing the heat sink 40 to the casing 11 is not particularly limited, but it is preferable to fix the heat sink 40 to the casing 11 by welding or by forming the heat sink 40 and the casing 11 as a single unit, which allows the heat sink 40 to be firmly fixed to the casing 11. Alternatively, if the heat sink 40 and the casing 11 contain magnetic materials, a magnet 51 may be attached to the heat sink 40 to attract the casing 11.

The float glass manufacturing apparatus 1 may include a thermally conductive layer 52 between the heat sink 40 and the casing 11. The thermally conductive layer 52 has fluidity and fills the gap between the heat sink 40 and the casing 11, improving thermal conductivity.

As described above, the heat sink 40 has a plurality of fins 41 and a base plate 42 that supports the plurality of fins 41. The base plate 42 has an opposing surface 42a that faces the outer surface of the casing 11 and an opposite surface 42b that faces the opposite direction from the opposing surface 42a. The thermally conductive layer 52 is applied to the opposing surface 42a (e.g., the upper surface) of the base plate 42. The fins 41 are provided on the opposite surface 42b (e.g., the lower surface) of the base plate 42.

Next, referring to Figure 3, an example of the arrangement of the joints 21, 22, the nozzle outlet 31 of the nozzle 30, and the heat sink 40 will be described through the bottom casing 111. The heat sink 40 is arranged linearly along the joint 21 or 22. When viewed from a direction perpendicular to the underside of the bottom casing 111 (specifically, from below), the heat sink 40 overlaps the joint 21 or 22. The heat sink 40 can efficiently cool the joint 21 or 22, which is the path through which the molten metal M passes, reducing the amount of refrigerant used.

The underside of the bottom brick 13 is rectangular and surrounded on all four sides by four joints selected from a plurality of joints 21, 22 (for example, four joints 21, three joints 21 and one joint 22, or two joints 21 and two joints 22). Therefore, the multiple heat sinks 40 may be arranged in a square lattice pattern. This allows for concentrated cooling of the path of the molten metal M. Cooling of areas outside the path of the molten metal M can be suppressed, reducing the amount of refrigerant used.

When viewed from below, the heat sink 40 may overlap the intersection of four or three joints selected from the multiple joints 21, 22. When viewed from below, the injection port 31 of the nozzle 30 may also overlap the intersection of four or three joints selected from the multiple joints 21, 22.

When viewed from below, the nozzle outlet 31 of the nozzle 30 overlaps with the joint 21 or 22 and also overlaps with the heat sink 40. This allows for more concentrated cooling of the path of the molten metal M. This further suppresses cooling of areas outside the path of the molten metal M, further reducing the amount of refrigerant used.

Although not shown, the heat sink 40 may be attached to the outward-facing side surface 112a of the side casing 112, or may be arranged linearly along the joint 23. In this case, when viewed from a direction perpendicular to the side surface 112a (for example, the Y-axis direction or the X-axis direction), the heat sink 40 overlaps the joint 23. The heat sink 40 can efficiently cool the joint 23, which is the path through which the molten metal M passes, reducing the amount of refrigerant used.

Next, referring again to Figure 4, an example of the structure of the heat sink 40 will be described. The heat sink 40 has, for example, a linear base plate 42 and a plurality of fins 41 arranged in a row at intervals along the longitudinal direction of the base plate 42. The base plate 42 is arranged along joint 21, joint 22, or joint 23.

The magnets 51 are attached, for example, to both longitudinal ends of the base plate 42. A pair of magnets 51 are provided, sandwiching the base plate 42 in the width direction. The pair of magnets 51 are attached to both longitudinal ends of the base plate 42.

Next, with reference to Figure 5, a modified example of the structure of the heat sink 40 will be described. The heat sink 40 has, for example, a linear base plate 42 and a plurality of fins 41 arranged at intervals across the width of the base plate 42. The base plate 42 is arranged along joint 21, joint 22, or joint 23.

As shown in FIG. 6, the multiple fins 41 are parallel plates that form refrigerant flow paths 43 along the joints 21. The flow paths 43 allow the refrigerant to flow along the joints 21, allowing the refrigerant to efficiently cool the joints 21. Although not shown, the multiple fins 41 may also form refrigerant flow paths 43 along the joints 22 or 23.

As shown in FIG. 6 , when viewed from a direction (e.g., the Z-axis direction) perpendicular to the outer surface of the casing 11 (e.g., the underside of the bottom casing 111), the nozzle outlet 31 of the nozzle 30 overlaps with the heat sink 40. The nozzle outlet 31 of the nozzle 30 injects the refrigerant directly upward. The direction in which the refrigerant is injected from the nozzle 31 is perpendicular to the direction in which the refrigerant flows in the flow path 43.

Although not shown, the nozzle 30's outlet 31 may be installed next to the heat sink 40, or the refrigerant may be sprayed directly to the side. In this case, the direction in which the refrigerant is sprayed from the outlet 31 is the same as the direction in which the refrigerant flows through the flow path 43, which prevents turbulence in the refrigerant flow and improves the cooling efficiency of the casing 11 by the refrigerant.

The float glass manufacturing apparatus and float glass manufacturing method according to the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. Naturally, these also fall within the technical scope of the present disclosure.

10 Bathtub M Molten metal G Molten glass GR Glass ribbon

Claims (10)

A float glass manufacturing apparatus comprising: a bath for containing molten metal; continuously supplying molten glass onto the molten metal in the bath; and forming the supplied molten glass into a band-shaped glass ribbon while causing the molten glass to flow on the molten metal,
The bath includes a plurality of bricks in contact with the molten metal and a box-shaped casing that accommodates the plurality of bricks,
a nozzle that sprays a refrigerant toward the outer surface of the casing; and a heat sink having a plurality of fins,
the heat sink is attached to the outer surface of the casing ;
The float glass manufacturing apparatus , wherein the heat sinks are arranged linearly along the joints between adjacent bricks . The float glass manufacturing apparatus according to claim 1, wherein the nozzle has an injection port for injecting the refrigerant toward the joints between adjacent bricks. 2. The float glass manufacturing apparatus according to claim 1 , wherein the plurality of heat sinks are arranged in a square lattice pattern. 4. The float glass manufacturing apparatus according to claim 1 , wherein the plurality of fins are plates parallel to each other and form flow paths for the refrigerant along joints between adjacent bricks. 5. The float glass manufacturing apparatus according to claim 1 , wherein the length of the fin in the direction perpendicular to the outer surface of the casing is 75 mm or more. The float glass manufacturing apparatus according to any one of claims 1 to 5 , further comprising a magnet for fixing the heat sink to the casing. The float glass manufacturing apparatus according to any one of claims 1 to 6 , further comprising a thermally conductive layer between the heat sink and the casing. The float glass manufacturing apparatus according to any one of claims 1 to 7 , further comprising a heat dissipation paint applied to the heat sink. The float glass manufacturing apparatus according to any one of claims 1 to 8 , wherein the refrigerant is air, water, or a mixture of air and water. A float glass manufacturing method using the float glass manufacturing apparatus according to any one of claims 1 to 9 ,
forming the molten glass into the glass ribbon while flowing the molten glass over the molten metal;
and cooling the outer surface of the casing using the nozzle and the heat sink.