CN114075031A

CN114075031A - Float glass manufacturing device and float glass manufacturing method

Info

Publication number: CN114075031A
Application number: CN202110923519.7A
Authority: CN
Inventors: 泷口哲史; 川崎直哉; 山本阳平; 山崎健史
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 2020-08-18
Filing date: 2021-08-12
Publication date: 2022-02-22

Abstract

The invention provides a float glass manufacturing device and a float glass manufacturing method, which are techniques for obtaining a glass ribbon with wide width and small thickness deviation. A float glass manufacturing apparatus is provided with a bath, a runner outlet lip, a pair of flow restricting bricks, a plurality of top rollers, a kiln top, a plurality of heaters, and a plurality of controllers. In each of the sections in which the crown is divided into a plurality of rows in the flow direction of the glass ribbon and each of the rows is divided in the width direction of the glass ribbon, a plurality of the heaters collectively controlled by one of the controllers selected for each of the sections are provided in addition to the specific section. The particular said section is the section directly above the downstream end of each said flow restricting brick. A plurality of heaters collectively controlled by one controller selected for each of the sub-segments are provided in each sub-segment into which the specific segment is divided in the flow direction.

Description

Float glass manufacturing device and float glass manufacturing method

Technical Field

The present disclosure relates to a float glass manufacturing apparatus and a float glass manufacturing method.

Background

The float glass manufacturing apparatus continuously supplies molten glass onto molten metal in a bath, flows the molten glass over the molten metal, and forms the molten glass into a glass ribbon in a ribbon shape. After annealing the glass ribbon, both widthwise ends of the glass ribbon are cut off to obtain float glass. Float glass is used for a glass substrate of a Flat Panel Display (FPD) or the like.

Patent document 1 describes a technique for controlling the temperature distribution of a glass ribbon in order to reduce the variation in the thickness of float glass. A plurality of heaters are provided in each section in which the heater region is divided into a plurality of rows in the flow direction of the glass ribbon and each row is divided in the width direction of the glass ribbon, and the heaters are collectively controlled for each section.

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 8-325024

Disclosure of Invention

Summary of the invention

Problems to be solved by the invention

With the increase in size of FPDs, a wide glass ribbon is desired. However, the wider the width of the glass ribbon, the more likely the variation in the thickness of the glass ribbon becomes. The thickness deviation is the difference between the maximum value and the minimum value of the thickness.

One aspect of the present disclosure provides a technique for obtaining a glass ribbon having a wide width and a small variation in sheet thickness.

Means for solving the problems

A float glass manufacturing apparatus according to one aspect of the present disclosure includes: the device comprises a bath, a runner outlet lip plate, a pair of flow-limiting bricks, a plurality of top rollers, a kiln top, a plurality of heaters and a plurality of controllers. The bath contains molten metal. The runner outlet lip continuously supplies molten glass onto the molten metal. The pair of flow restricting bricks expands the width of the flow of the molten glass supplied onto the molten metal from the upstream side toward the downstream side. The plurality of top rollers press the widthwise ends of the ribbon-shaped glass ribbon downstream of the pair of flow-restricting bricks. The roof is disposed above the glass ribbon. A plurality of said heaters are suspended from said kiln top. A plurality of the controllers control a plurality of the heaters. In each section in which the furnace ceiling is divided into a plurality of rows in the flow direction of the glass ribbon and each row is divided in the width direction of the glass ribbon, a plurality of heaters collectively controlled by one controller selected for each section are provided in addition to the specific section. The particular said section is the section directly above the downstream end of each said flow restricting brick. A plurality of heaters collectively controlled by one controller selected for each of the sub-segments are provided in each sub-segment into which the specific segment is divided in the flow direction.

Effects of the invention

According to one aspect of the present disclosure, a glass ribbon having a wide width and small variations in sheet thickness can be obtained.

Drawings

Fig. 1 is a vertical cross-sectional view of a float glass manufacturing apparatus according to an embodiment, taken along line I-I of fig. 2.

Fig. 2 is a horizontal sectional view of a float glass manufacturing apparatus according to an embodiment, which is a horizontal sectional view taken along line II-II of fig. 1.

Fig. 3 is a plan view showing an example of the flow of molten glass on molten metal.

Fig. 4 is a plan view showing an example of a section of the kiln top.

Fig. 5 is a cross-sectional view showing an example of convection of molten metal in a deep bottom region.

Fig. 6 is a plan view showing a float glass manufacturing apparatus according to a modification.

FIG. 7 is a cross-sectional view showing an example of the cooling pipe and the heat insulating material.

Fig. 8 is a sectional view taken along line VIII-VIII of fig. 7.

Description of the reference symbols

10 bath

14 flow channel outlet lip plate

24. 25 flow-limiting brick

27 kiln top

30 top roller

50 heating apparatus

M molten metal

G molten glass

GR glass belt

Detailed Description

Hereinafter, a float glass manufacturing apparatus and a float glass manufacturing method according to an embodiment of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same reference numerals, and the description thereof may be omitted. In each drawing, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other, the X-axis direction and the Y-axis direction are horizontal directions, and the Z-axis direction is a vertical direction. The X-axis direction is a flow direction of the glass ribbon GR, and the Y-axis direction is a width direction of the glass ribbon GR. In the specification, "to" indicating a numerical range means to include numerical values described before and after the range as a lower limit value and an upper limit value.

As shown in fig. 1, the float glass manufacturing apparatus 1 continuously supplies molten glass G onto molten metal M in a vessel 10, and forms a glass ribbon GR in a ribbon shape by flowing the molten glass G over the molten metal M. The glass ribbon GR is pulled up from the molten metal M in the downstream region of the vessel 10, annealed by an annealing apparatus, not shown, and cut into a predetermined size by a processing apparatus, not shown. The processing device cuts off both ends in the width direction of the glass ribbon GR. The glass ribbon GR is processed by a processing apparatus to obtain float glass as a product.

Kind of glass as float glassExamples thereof include alkali-free glass, aluminosilicate glass, borosilicate glass, and soda-lime glass. The alkali-free glass means that Na is not substantially contained₂O、K₂And alkali metal oxide glasses such as O. Here, the substantial absence of the alkali metal oxide means that the total content of the alkali metal oxides is 0.1 mass% or less.

The float glass is not particularly limited in its application, and is, for example, a Flat Panel Display (FPD) such as a Liquid Crystal Display (LCD) and an organic EL display, and is, for example, a glass substrate for FPD. When the float glass is used as a glass substrate for an FPD, the float glass is alkali-free glass.

The float glass preferably contains 54 to 66% of SiO in terms of mass% based on oxides ₂10 to 23 percent of Al₂O₃6 to 12 percent of B₂O₃And 8 to 26 percent of MgO + CaO + SrO + BaO.

The float glass is preferably displayed in mass% based on oxides so as to have a high strain point, and contains 54% to 68% of SiO ₂10 to 25 percent of Al₂O₃0.1 to 5.5 percent of B₂O₃And 8 to 26 percent of MgO + CaO + SrO + BaO.

The thickness of the float glass is selected according to the application of the float glass. When the float glass is used as a glass substrate for an FPD, the thickness of the float glass is preferably 0.7mm or less, more preferably 0.5mm or less, still more preferably 0.4mm or less, 0.3mm or less, 0.2mm or less, or 0.1mm or less.

The thickness of the float glass is measured over the entire width direction of the glass ribbon GR after the widthwise ends of the glass ribbon GR have been cut out. The thickness variation of the float glass is calculated based on the result of the thickness measurement of the float glass.

As shown in fig. 1, a float glass manufacturing apparatus 1 includes a bath 10. The bath 10 contains molten metal M. As the molten metal M, for example, molten tin is used. In addition to the molten tin, a molten tin alloy or the like may be used, and the molten metal M may be a metal having a density higher than that of the molten glass G.

The bath 10 has: a box-shaped bottom case 11 opened upward; side bricks 12 protecting the side walls of the bottom case 11 from the molten metal M; and a bottom brick 13 provided inside the bottom wall of the bottom case 11.

The float glass manufacturing apparatus 1 includes a runner outlet lip 14. The spout outlet lip 14 supplies the molten glass G onto the molten metal M in the bath 10. As shown in fig. 2, the side stays 16 and 17 hold the spout lip 14 in the width direction, and prevent the molten glass G flowing on the spout lip 14 from overflowing in the width direction.

As shown in fig. 1, the float glass manufacturing apparatus 1 includes a shutter 18. The gate 18 is movable up and down with respect to the spout lip 14, and adjusts the flow rate of the molten glass G flowing on the spout lip 14. The narrower the distance between the gate 18 and the spout lip 14, the smaller the flow rate of the molten glass G flowing on the spout lip 14.

The gate 18 is made of refractory. The shutter 18 can be provided with a protective film 19 for preventing the shutter 18 from coming into contact with the molten glass G. The protective film 19 is formed of, for example, platinum or a platinum alloy.

As shown in FIG. 3, float glass manufacturing apparatus 1 has a wetback brick 22 and a pair of

restrictor bricks

24, 25. The wetback brick 22 is disposed below the runner outlet lip 14 in contact with the upstream end of the molten glass G. A pair of flow

restrictor tiles

24, 25 extend obliquely downstream from the wetback tile 22 and diverge downstream. The pair of

flow restricting bricks

24 and 25 gradually widen the width of the flow of the molten glass G from the upstream side toward the downstream side.

The molten glass G forms a main flow F1 and a sub flow F2 after being fed onto the molten metal M. The main flow F1 flows in the positive X-axis direction. On the other hand, the substream F2 flows back in the negative X-axis direction toward the wetback bricks 22. When reaching the wetback brick 22, the branch flow F2 flows along the wetback brick 22 while being divided left and right, then flows along the pair of left and right

flow restricting bricks

24 and 25, and merges at both width-direction end portions of the main flow F1.

Therefore, heterogeneous components generated by contact between the outlet lip 14, the back wetting brick 22, and the

flow restricting bricks

24 and 25 and the molten glass G are accumulated at both ends of the glass ribbon GR in the width direction. Both ends in the width direction of the glass ribbon GR are cut off after annealing, and do not become a part of the product, so that high-quality float glass can be obtained.

As shown in fig. 1, the float glass manufacturing apparatus 1 includes an upper space S of the bath 10. The ceiling 27 forms the upper surface of the space S above the bath 10. The partition wall 28 partitions the upper space S of the bath 10 into an upstream-side flow path outlet space S1 and a downstream-side main space S2. The partition wall 28 is also referred to as a front lintel.

The main space S2 is much larger than the flow channel outlet space S1. In order to prevent oxidation of the molten metal M, the main space S2 is filled with a reducing gas. The reducing gas is, for example, a mixed gas of nitrogen and hydrogen, and contains 85 to 98.5 vol% of nitrogen and 1.5 to 15 vol% of hydrogen. The reducing gas is supplied from the joints between bricks of the kiln top 27 and the holes of the kiln top 27.

As shown in fig. 3, the float glass manufacturing apparatus 1 includes a top roller 30. The top roller 30 rotates while pressing the widthwise end portion of the glass ribbon GR, and feeds out the glass ribbon GR in the X-axis direction. The glass ribbon GR gradually cools and hardens while moving in the X-axis direction.

The pair of top rollers 30 is provided on both sides of the glass ribbon GR in the width direction, and suppresses shrinkage of the glass ribbon GR in the width direction. The sheet thickness of the glass ribbon GR can be made thinner than the equilibrium thickness. Although not shown, a plurality of the pair of top rollers 30 are provided with an interval in the flow direction of the glass ribbon GR.

The top roller 30 has a rotating member 31 and a rotating shaft 32. The rotary member 31 is, for example, disk-shaped, and presses the width direction end of the glass ribbon GR with its outer periphery to feed the glass ribbon GR in the flow direction of the glass ribbon GR. The rotary shaft 32 is driven to rotate by a driving device not shown, and rotates the rotary member 31.

As shown in fig. 1, the float glass manufacturing apparatus 1 includes a heater 50. The heater 50 is suspended from the ceiling 27 and heats the glass ribbon GR passing therebelow. The heater 50 is an electric heater, and is heated by being energized. The heater 50 is, for example, a SiC heater. A plurality of heaters 50 are arranged in a matrix along the flow direction and the width direction of the glass ribbon GR.

By controlling the outputs of the plurality of heaters 50, the temperature distribution of the glass ribbon GR can be controlled, and the sheet thickness distribution of the glass ribbon GR can be controlled. The output of the heater 50 means the amount of heat per unit time (unit: kW). The outputs of the heaters 50 are controlled for each of the sections a1, A3, a5, B1 to B4 except for the specific sections a2 and a4 (see fig. 4).

Next, a method of partitioning the kiln top 27 will be described with reference to fig. 4. The roof 27 is divided into a plurality of rows A, B in the flow direction of the glass ribbon GR. Each row A, B is divided into a plurality of segments a1 to a5 and B1 to B4 in the width direction of the glass ribbon GR. Each row A, B is preferably divided into left and right symmetrical sections around the center line CL in the width direction of the glass ribbon GR. The temperature distribution of the glass ribbon GR can be controlled symmetrically about the widthwise center line CL of the glass ribbon GR.

In each of the sections a1 to a5 and B1 to B4, a plurality of heaters 50 collectively controlled by one controller 60 selected for each of the sections a1, A3, a5, and B1 to B4 are provided in addition to the specific sections a2 and a 4. The case of collective control includes a case of controlling to the same output. By collectively controlling the plurality of heaters 50 by one controller 60, the number of controllers 60 can be reduced. The controller 60 is, for example, a microcomputer.

A boundary line D1 of two rows A, B adjacent in the flow direction of the glass ribbon GR is also referred to as a first dividing line D1. Further, a boundary line D2 between two sections adjacent in the width direction of the glass ribbon GR is also referred to as a second dividing line D2. Preferably, the second dividing line D2 is shifted in the width direction of the glass ribbon GR in the rows a and B across the first dividing line D1.

For example, a boundary line D2 between the section a1 and the section a2 and a boundary line D2 between the section B1 and the section B2 are offset in the width direction of the glass ribbon GR with the first dividing line D1 interposed therebetween. Therefore, in the upstream row a, the portion of the glass ribbon GR passing below the boundary D2 between the section a1 and the section a2 passes below the section B1 in the downstream row B.

In column A upstream, if the output of the heater 50 per unit area in section A1 and section A2 (unit: kW/m)²) Instead, the glass ribbon will be positioned near the boundary D2 between section A1 and section A2A sharp temperature difference occurs in the width direction of the GR. This temperature difference also occurs at a portion of the glass ribbon GR passing below the boundary D2 between the section a1 and the section a 2. This portion is located downstream of the row B passing below the section B1, and the temperature difference is reduced. As a result, the variation in the thickness of the glass ribbon GR can be reduced.

In the bath 10, a region from the downstream ends of the pair of

flow restricting bricks

24 and 25 to the pair of top rollers 30 at the most upstream is also referred to as a hot region X1. Further, a region downstream of the pair of top rollers 30 on the most upstream side is also referred to as a forming region X2. The viscosity of the glass ribbon GR in the hot zone X1 is, for example, 10^3.8dPa·s～10^5.0dPa · s. The viscosity of the glass ribbon GR in the forming region X2 is, for example, 10^5.0dPa·s～10^7.5dPa·s。

In the forming region X2, the shrinkage of the glass ribbon GR in the width direction is suppressed, and the sheet thickness distribution of the glass ribbon GR in the width direction is adjusted. Therefore, in the hot zone X1 upstream of the forming zone X2, it is important to make the temperature distribution and the sheet thickness distribution in the width direction of the glass ribbon GR as uniform as possible. Note that, if the temperature distribution is made uniform, the plate thickness distribution also becomes uniform.

Thus, the particular sections a2, a4 are also divided into a plurality of sub-sections in the flow direction of the glass ribbon GR. The particular sections a2, a4 are sections directly above the downstream end of each flow

restrictor brick

24, 25. A pair of specific sections a2, a4 are disposed with a space W1 therebetween in the width direction of the glass ribbon GR. Preferably, a section a3 controlled by one controller 60 is disposed therebetween.

For example, a particular section A2 is divided into a plurality of sub-sections A2-1, A2-2 in the flow direction of the glass ribbon GR. A plurality of heaters 50 collectively controlled by one controller 60 selected for each of the sub-sections A2-1 and A2-2 are provided in each of the sub-sections A2-1 and A2-2. Each sub-section A2-1, A2-2 is preferably disposed directly above the hot zone X1. The downstream sub-section A2-2 protrudes outward in the width direction of the glass ribbon GR from the upstream sub-section A2-1.

Likewise, the particular section A4 is divided into a plurality of sub-sections A4-1, A4-2 in the direction of flow of the glass ribbon GR. A plurality of heaters 50 collectively controlled by one controller 60 selected for each of the sub-sections A4-1 and A4-2 are provided in the sub-sections A4-1 and A4-2. Each sub-section A4-1, A4-2 is preferably disposed directly above the hot zone X1. The downstream sub-section A4-2 protrudes outward in the width direction of the glass ribbon GR from the upstream sub-section A4-1.

In the hot zone X1, the width of the glass ribbon GR widens from the upstream side toward the downstream side. Both ends of the glass ribbon GR in the width direction, that is, portions of the glass ribbon GR at a low temperature pass directly below the upstream sub-sections A2-1 and A4-1. On the other hand, the widthwise central portion of the glass ribbon GR, that is, the portion of the glass ribbon GR having a high temperature does not pass directly under the upstream sub-sections A2-1 and A4-1 but passes directly under the section A3. Then, a part of the glass ribbon GR having a high temperature passes right under the sub-sections A2-2, A4-2 on the downstream side.

According to the present embodiment, in the upstream side sub-sections a2-1, a4-1 and the downstream side sub-sections a2-2, a4-2, the output of the heater 50 per unit area can be independently controlled. Therefore, in the hot zone X1 upstream of the forming zone X2, the temperature distribution and the sheet thickness distribution in the width direction of the glass ribbon GR can be made uniform. As a result, the glass ribbon GR can be obtained with a wide width and small variations in sheet thickness.

When the glass ribbon GR is heated, the output of the heater 50 per unit area of the sub-sections A2-2, A4-2 on the downstream side is controlled to be smaller than the output of the heater 50 per unit area of the sub-sections A2-1, A4-1 on the upstream side. This is because the low-temperature portion of the glass ribbon GR passes directly below the upstream sub-sections a2-1 and a4-1, whereas the high-temperature portion of the glass ribbon GR passes directly below the downstream sub-sections a2-2 and a 4-2.

When the glass ribbon GR is heated, the output of the heater 50 per unit area of the sub-sections A2-1 and A4-1 on the upstream side is preferably controlled to 3kW/m²Above 42kW/m²Hereinafter, it is more preferable to control the concentration to 10kW/m²Above 38kW/m²The following. On the other hand, the output of the heater 50 per unit area of the sub-sections A2-2, A4-2 on the downstream side is preferably controlled to be 0kW @m²Above 5kW/m²Hereinafter, it is more preferable to control the concentration to 0kW/m²Above 4.5kW/m²The following.

When the glass ribbon GR is heated, the output of the heater 50 per unit area of the sub-sections A2-2 and A4-2 on the downstream side may be 0kW/m². The downstream sub-sections A2-2 and A4-2 may be used only for heating the bath 10 at the time of heating in the preceding stage of starting the float glass production, and may not be used for heating the glass ribbon GR.

The upstream sub-sections a2-1 and a4-1 are disposed immediately above the downstream ends of the

restrictor bricks

24 and 25, and heat the downstream ends thereof. Therefore, stagnation of the flow of the molten glass G in the vicinity of the downstream end can be suppressed, and devitrification can be suppressed. Devitrification is a phenomenon in which crystals are precipitated from the molten glass G to lower the transparency. Devitrification occurs in a place where the flow of the molten glass G stagnates.

A pair of specific segments a2, a4 are disposed so as to sandwich segment A3. Only the widthwise central portion of the glass ribbon GR, that is, the portion of the glass ribbon GR where the temperature is high, passes directly below the section a 3. Therefore, unlike the sections a2 and a4, the section A3 is not divided into a plurality of sub-sections in the flow direction of the glass ribbon GR, and is collectively controlled by one controller 60.

When the glass ribbon GR is heated, the output of the heater 50 per unit area of the section A3 is controlled to be smaller than the output of the heaters 50 per unit area of the two sub-sections A2-1 and A4-1 on the upstream side, and is preferably controlled to be 0kW/m²Above and 1kW/m²Hereinafter, it is more preferable to control the concentration to 0kW/m²Above and 0.5kW/m²The following. In the present embodiment, 1 block A3 is disposed between the block a2 and the block a4, but a plurality of blocks may be disposed.

The spacing W1 between the pair of specific sections a2, a4 is preferably 60% or more of the width W2 of the downstream ends of the pair of flow-restricting

bricks

24, 25. If the interval W1 is 60% or more of the width W2, the output of the heater 50 per unit area of the segment A3 is controlled to be small, so that the temperature of the widthwise central portion of the glass ribbon GR (the portion of the glass ribbon GR where the temperature is high) is likely to be lowered, and the temperature distribution and the sheet thickness distribution in the widthwise direction of the glass ribbon GR can be efficiently uniformized in the hot zone X1. W1 is more preferably 65% or more of W2. Further, W1 is preferably 75% or less, more preferably 70% or less of W2.

As shown in fig. 1, the bath 10 includes, in order from upstream to downstream, a deep bottom region X3 in which the depth of the molten metal M is constant, and a shallow bottom region X4 in which the depth is shallower than the deep bottom region X3 and is constant.

The deep bottom region X3 is disposed upstream of the forming region X2. In the deep bottom region X3, the depth of the molten metal M is deep, and the amount of the molten metal M is large. Therefore, the molten metal M can absorb the heat brought into the vessel 10 by the molten glass G and the glass ribbon GR as much as possible, and the temperature of the glass ribbon GR can be rapidly cooled to a temperature suitable for forming.

As shown in fig. 5, convection of the molten metal M can be formed in the deep bottom region X3. The molten glass G and the glass ribbon GR have high temperatures at the center of the vessel 10 in the width direction, and a large amount of heat is absorbed by the molten metal M. As a result, the molten metal M is heated and becomes light, and thus an upward flow of the molten metal M is formed. On the other hand, at both ends of the bath 10 in the width direction, the molten metal M is cooled and becomes heavy, and thus a downward flow of the molten metal M is formed. In the deep bottom region X3, the glass ribbon GR spreads from the center in the width direction toward both ends in the width direction, and therefore, a downward flow and an upward flow of the molten metal M as shown in fig. 5 are formed.

By the convection of the molten metal M, the temperature distribution in the width direction of the molten metal M can be made uniform, and further, the temperature distribution in the width direction of the glass ribbon GR can be made uniform. The deeper the depth of the molten metal M, the more easily the upward and downward flows are formed, and the stronger the flow.

On the other hand, in the shallow region X4, the depth of the molten metal M is shallow, and the amount of the molten metal M is small. Therefore, the amount of the molten metal M used can be reduced. As shown in fig. 1, the shallow region X4 is formed entirely from the upstream end to the downstream end of the forming region X2, and extends to the upstream side of the forming region X2. The upstream end of the shallow region X4 is disposed in the hot region X1.

The X-axis direction length L1 of the portion of the thermal region X1 overlapping the deep bottom region X3 is preferably 35% or more of the X-axis direction length L0 of the thermal region X1. Conventionally, L1 is about 20% of L0. According to the present embodiment, since L1 is 35% or more of L0, convection of molten metal M shown in fig. 5 can be formed in a relatively wide range of hot zone X1. More preferably, L1 is 30% or more of L0.

As shown in FIG. 1, the boundary line D3 of the two sub-sections A2-1 and A2-2 is preferably disposed directly above the deep bottom region X3. Similarly, the boundary line between the two sub-sections A4-1 and A4-2 is preferably located directly above the deep bottom region X3. The convection of the molten metal M shown in FIG. 5 can be formed not only directly below the upstream side sub-sections A2-1, A4-1 but also directly below the downstream side sub-sections A2-2, A4-2.

As shown in fig. 3, in a plan view, the side wall of the bottom case 11 extends from the vicinity of the downstream end of each of the

restrictor bricks

24 and 25 to the outside in the width direction of the glass ribbon GR, and then extends to the downstream in the flow direction of the glass ribbon GR, forming a right-angled corner CR. The side bricks 12 are preferably arranged in a triangular shape on the inner side of each corner CR.

In a plan view, the side wall of bottom case 11 forms an inclined corner instead of right-angled corner CR, and a distance from the width direction end of glass ribbon GR to the side wall of bottom case 11 can be secured as compared with a case where side bricks 12 are provided in an inclined straight line inside the corner. Therefore, the heat at the widthwise end of the glass ribbon GR can be prevented from flowing out to the outside in the widthwise direction, and a temperature drop at the widthwise end of the glass ribbon GR can be prevented.

Next, a float glass manufacturing apparatus 1 according to a modification will be described with reference to fig. 6. As shown in fig. 6, float glass manufacturing apparatus 1 may also include cooling pipe 70. The cooling pipe 70 cools the widthwise central portion of the glass ribbon GR from above in the hot zone X1. As described above, the hot zone X1 refers to the zone from the downstream ends of the pair of

flow restricting bricks

24, 25 to the pair of top rollers 30 at the most upstream. The width of the widthwise central portion of the glass ribbon GR is, for example, 40% of the entire width of the glass ribbon GR.

In the hot zone X1, the widthwise central portion of the glass ribbon GR is higher in temperature and thicker in sheet thickness than the widthwise end portions of the glass ribbon GR. When the widthwise central portion of the glass ribbon GR is cooled by the cooling pipe 70, the temperature difference can be reduced, and the thickness variation can be reduced. The cooling pipe 70 may cool the widthwise central portion of the glass ribbon GR, but may also cool other portions. The cooling pipe 70 may cool the glass ribbon GR so that a temperature difference in the width direction of the glass ribbon GR is reduced.

The cooling pipe 70 is disposed horizontally in the width direction of the glass ribbon GR, for example. The cooling pipes 70 are inserted one from each of a pair of side walls orthogonal to the Y-axis direction and provided on the side bricks 12. The cooling pipe 70 may be continuously extended from one side wall to the other side wall. The cooling pipe 70 may be suspended from the ceiling 27 in the same manner as the heater 50.

As shown in fig. 8, the cooling pipe 70 has a flow path 71 through which the refrigerant flows. The refrigerant is a liquid such as water. The refrigerant may be a gas such as air. The flow path 71 may include a forward path 72 and a return path 73, respectively. The coolant flows from the outside to the inside in the width direction of the glass ribbon GR in the outward passage 72, and then flows from the inside to the outside in the width direction of the glass ribbon GR in the circuit 73. The cooling efficiency can be improved by arranging the outward path 72 and the return path 73 separately to regulate the flow of the refrigerant. The cooling pipe 70 is a square pipe in fig. 8, but may be a circular pipe.

The cooling pipe 70 selectively cools the widthwise central portion of the glass ribbon GR with respect to the widthwise end portions of the glass ribbon GR. However, the widthwise end portions of the glass ribbon GR are also cooled by the cooling pipe 70. Therefore, the controller 60 may increase the output of the heaters 50 provided in the sections a1 and a5 in order to heat the widthwise end portion of the glass ribbon GR from the widthwise outer side. Further, the controller 60 may increase the output of the heater 50 provided in the sections a2 and a 4.

As shown in fig. 7 to 8, the float glass manufacturing apparatus 1 may further include a heat insulating material 75 covering the cooling pipe 70. The thermal conductivity of the thermal insulation material 75 is, for example, 0.05W/(m)²·K)～1W/(m²K), preferably 0.3W/(m)²·K)～0.7W/(m²K). The material of the heat insulating material 75 is determined so that foreign matter does not fall on the upper surface of the glass ribbon GR.

The thinner the thickness T of the heat insulating material 75 is, the more easily the refrigerant absorbs heat, and the more easily the glass ribbon GR is cooled. Therefore, as shown in fig. 7, the thickness T of the heat insulating material 75 may be reduced as it goes from the outer side to the inner side in the width direction of the glass ribbon GR. This enables the widthwise central portion of the glass ribbon GR to be selectively cooled with respect to the widthwise end portions of the glass ribbon GR.

In fig. 7, the entire Y-axis direction of the cooling pipe 70 is covered with the heat insulating material 75, but the entire Y-axis direction of the cooling pipe 70 may not be covered with the heat insulating material 75. For example, the thickness T of the heat insulating material 75 may be 0 at the distal end portion of the cooling pipe 70. The thickness T of the heat insulating material 75 may be reduced as the glass ribbon GR is oriented inward from the outer side in the width direction. The thickness T of the heat insulating material 75 changes in stages in fig. 7, but may also change continuously.

[ examples ] A method for producing a compound

In the following experiment, the glass ribbon GR was formed under the same conditions except that the output of the heaters per unit area of the sub-sections A2-1, A2-2, A4-1, A4-2 and the section A3 shown in FIG. 4 were controlled to the values shown in Table 1, and after annealing, both widthwise ends of the glass ribbon GR were cut off, thereby obtaining a float glass. W1 was 71% of W2. Furthermore, L1 was 35% of L0.

The float glass was divided into 6 test pieces by 6 divisions in the width direction of the glass ribbon GR. The thickness of each test piece in the width direction was measured, and the thickness variation was calculated. The total of the thickness deviations of the 6 test pieces was the total of the thickness deviations of the 6 sites. The smaller the total value of the thickness deviations of the 6 portions is, the smaller the thickness distribution in the width direction of the glass ribbon GR is. Table 1 shows the results of the tests. In table 1, the total of the thickness deviations at 6 sites is the average value of the float glass produced during 1 month.

[ TABLE 1 ]

In table 1, example 1 is an example, and example 2 is a comparative example. As is clear from Table 1, if the outputs of the heaters per unit area are independently controlled in the upstream sub-stages A2-1 and A4-1 and the downstream sub-stages A2-2 and A4-2, the total of the plate thickness deviations of 6 portions can be reduced. That is, it was found that a glass ribbon having a wide width and small variations in sheet thickness could be obtained.

Although the float glass manufacturing apparatus and the float glass manufacturing method of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and the like. Various changes, modifications, substitutions, additions, deletions, and combinations may be made within the scope of the claims. These are, of course, within the technical scope of the present disclosure.

Claims

1. A float glass manufacturing apparatus comprising a bath for containing molten metal, a runner outlet lip for continuously supplying molten glass to the molten metal, a pair of flow restricting bricks for expanding the width of the flow of the molten glass supplied to the molten metal from the upstream side toward the downstream side, a plurality of top rollers for pressing the widthwise ends of a ribbon-like glass ribbon downstream of the pair of flow restricting bricks, a furnace roof provided above the glass ribbon, a plurality of heaters suspended from the furnace roof, and a plurality of controllers for controlling the plurality of heaters, wherein the plurality of heaters are arranged in a manner such that the heaters are arranged in a direction perpendicular to the direction of the flow of the molten glass supplied to the molten metal,

in each section in which the furnace ceiling is divided into a plurality of rows in the flow direction of the glass ribbon and each row is divided in the width direction of the glass ribbon, a plurality of heaters collectively controlled by one controller selected for each section are provided in addition to the specific section,

the particular said section is the section immediately above the downstream end of each said flow restricting brick,

a plurality of heaters collectively controlled by one controller selected for each of the sub-segments are provided in each sub-segment into which the specific segment is divided in the flow direction.

2. The float glass manufacturing apparatus of claim 1, wherein,

a pair of the specific segments are arranged with a space in the width direction,

the sections collectively controlled by one controller are arranged between a pair of the specific sections.

3. The float glass manufacturing apparatus of claim 2, wherein,

the spacing between a pair of the specific sections is more than 60% of the width of the downstream ends of a pair of the flow-limiting bricks.

4. The float glass manufacturing apparatus according to any one of claims 1 to 3, wherein,

the bath has a hot zone from the downstream ends of the pair of flow restricting bricks to the pair of top rollers at the most upstream, and a forming zone downstream of the pair of top rollers at the most upstream,

each of the sub-sections is disposed directly above the hot zone.

5. The float glass manufacturing apparatus of claim 4, wherein,

the bath has a deep bottom region in which the depth of the molten metal is constant and a shallow bottom region in which the depth is shallower than the deep bottom region and is constant in this order from upstream to downstream,

a length in the flow direction of a portion of the thermal region that overlaps the deep bottom region is 35% or more of a length in the flow direction of the thermal region.

6. The float glass manufacturing apparatus of claim 5, wherein,

the boundary line of two sub-sections adjacent in the flow direction is arranged directly above the deep bottom region.

7. The float glass manufacturing apparatus according to any one of claims 1 to 6, wherein,

the bath includes a box-shaped bottom shell opened upward, a plurality of bottom bricks protecting a bottom wall of the bottom shell against the molten metal, and a plurality of side bricks provided inside side walls of the bottom shell,

the side wall of the bottom case forms right-angled corners extending from the vicinity of the downstream end of each of the flow restricting bricks to the outside in the width direction and then extending downstream in the flow direction in a plan view, and the side bricks are arranged in a triangular shape inside the corners.

8. The float glass manufacturing apparatus according to any one of claims 1 to 7, wherein,

a cooling pipe for cooling the widthwise central portion of the glass ribbon from above is provided in a hot region from the downstream ends of the pair of flow-restricting bricks to the pair of top rollers at the most upstream.

9. The float glass manufacturing apparatus of claim 8, wherein,

comprises a heat insulating material covering the cooling pipe,

the cooling tubes are arranged horizontally along the width direction of the glass ribbon,

the thickness of the heat insulating material is reduced as the glass ribbon moves from the widthwise outer side to the widthwise inner side.

10. A float glass production method using the float glass production apparatus according to any one of claims 1 to 9, comprising the steps of:

continuously supplying the molten glass flowing on the runner outlet lip onto the molten metal in the bath;

flowing the molten glass over the molten metal and forming the glass ribbon into a ribbon plate; and

heating, with the heater, the glass ribbon passing under the heater.

11. The float glass manufacturing method according to claim 10,

the output of the heater per unit area of the sub-section on the upstream side when heating the glass ribbon is 3kW/m²Above, and the output of the heater per unit area of the sub-section on the downstream side is 1kW/m²The following.

12. The float glass manufacturing method according to claim 11,

the output of the heater per unit area of the section arranged between a pair of the specific sections is 1kW/m when the glass ribbon is heated²The following.