JP3846026B2 - Sheet glass manufacturing method and apparatus used for the method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a glass plate by a float process and a manufacturing apparatus therefor.
[0002]
[Prior art]
In the production of plate glass by the float process, molten glass is continuously poured into a bath containing a molten metal (usually tin or tin alloy) bath at a controlled flow rate, and the molten glass is fed into a glass ribbon (glass ribbon). It advances in a state and adjusts to a predetermined | prescribed width | variety and thickness, moving forward, and obtains a desired plate glass.
[0003]
Conventionally, in the production of plate glass by this float process, when the molten metal is oxidized, the generated oxide adheres to the plate glass and contributes to the disadvantage. Therefore, in order to prevent oxidation, the upper part of the molten metal bath in the bathtub is prevented. The space is filled with reducing gas (reducibility is mainly realized by hydrogen). This gas is supplied to the ceiling structure of the bathtub, and from there through the gap between the brick walls (roof bricks) and the gap between the roof brick and the heater provided in the brick wall, the upper space of the molten metal bath Supplied to. The supplied gas is discharged out of the bathtub mainly from an outlet of the bathtub or a discharge port provided for discharging the gas.
[0004]
Even when such a reducing gas is introduced, the metal vapor evaporated from the area not covered with the glass ribbon on the surface of the molten metal bath is oxidized by oxygen mixed in the bath, and the resulting metal oxide adheres to the glass ribbon. And may become contaminated. Therefore, in order to solve this problem, a partition wall is provided for partitioning the upper space of the molten metal bath surface in the bathtub into the upper space of the region covered with the glass ribbon and the upper space not covered with the glass ribbon, and on the side wall of the bathtub. An exhaust air passage is provided, reducing gas is supplied to the upper space of the region covered with the glass ribbon, and is discharged from the gap at the lower end of the partition wall to the upper space of the region not covered with the glass ribbon, and on the side wall. There has been proposed a method and an apparatus for producing sheet glass that are discharged to the outside of a bathtub through a provided air passage (Japanese Patent Laid-Open No. 50-3414).
[0005]
[Problems to be solved by the invention]
However, the technique disclosed in Japanese Patent Application Laid-Open No. 50-3414 has a problem that it is difficult to obtain a sufficient effect of atmosphere control because the position of the edge of the glass fluctuates. That is, conventionally, the top roll is engaged with both edges of the glass ribbon, and the thickness is adjusted while preventing the glass ribbon from shrinking. However, in this method, the position of the edge of the glass ribbon varies. . In the above technique, since the partition wall is fixed to a roof brick or the like, it cannot cope with such fluctuation.
[0006]
In the technique disclosed in Japanese Patent Laid-Open No. 50-3414, since the upper space in the bathtub is filled with reducing gas, the heater installed in the bathtub is required to have reduction resistance. That is, as a result of reaction of the constituent members of the heater with a reducing substance (such as hydrogen) in the atmospheric gas, or a substance that volatilizes from the glass ribbon or the molten metal surface, the heater deteriorates. This deterioration is more remarkable at higher temperatures. In particular, SiC heaters that are normally used are likely to deteriorate due to reaction with a reducing atmosphere or a substance (such as halogen) that volatilizes from the molten metal surface. Therefore, there is a problem that the heaters that can be used are extremely limited. In particular, normally used SiC heaters have a short life and need to be replaced with new ones after a short period of use.
[0007]
[Means for Solving the Problems]
In order to solve this problem, the present invention firstly supplies molten glass to a molten metal bath surface accommodated in a bathtub to form a glass ribbon flow, and advances the glass ribbon flow. In the manufacturing method of the plate glass including the step of forming to a predetermined width and thickness, the flow of the molten metal is controlled so as to form a groove or ridge of the molten metal near the edge in the width direction of the molten glass flow, and the groove Alternatively, the edge of the glass ribbon flow is held in place by compensating for the force of the glass ribbon flow to spread in the width direction or the force of narrowing the glass glass by the wrinkles, and is covered with the glass ribbon flow of the molten metal bath surface. There is provided a method for producing a plate glass, characterized in that the atmosphere in the upper space of the broken area is substantially shielded from the atmosphere in the upper space in the area of the molten metal bath surface that is not covered with the strip glass flow. Thereby, since the position of the edge of glass does not fluctuate, the sufficient effect of atmosphere control can be acquired.
[0008]
In the present invention, the composition of the gas in the upper space of the molten metal bath surface covered with the strip glass flow is an inert composition, and the molten metal bath surface of the region not covered with the strip glass flow The gas composition in the upper space is preferably a reducing composition. Thereby, lifetime improvement of a heater can be achieved.
[0009]
In addition, the present invention, secondly, as an apparatus for carrying out the invention, molten glass is supplied onto a molten metal bath accommodated in a substantially sealed bathtub, and the molten glass is used as a strip-shaped glass flow. An apparatus for producing sheet glass that is advanced and formed into a predetermined width and thickness, and in the molten metal bath, the molten metal can be blown out or sucked in a substantially vertical direction substantially along the edge of the strip glass flow. Blowing / suction means are provided, and the upper space of the region covered with the band glass flow on the molten metal bath and the area not covered substantially along the edge almost above the edge of the band glass flow An apparatus for producing plate glass is provided, which is provided with a partition that partitions the upper space.
Further, the present invention is a composition in which the composition of the gas in the upper space of the molten metal bath surface covered with the strip glass flow is inactive, and the molten metal bath surface is not covered with the strip glass flow. An apparatus for producing plate glass in which the composition of the gas in the upper space is a reducing composition is provided.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the atmosphere in the upper space of the molten metal bath surface covered with the strip glass flow is substantially blocked from the atmosphere in the upper space of the molten metal bath surface not covered with the strip glass flow. ing. In order to realize this, the manufacturing apparatus of the present invention is provided with a partition for partitioning each space. The “partition” used in the present invention may be a partition plate made of a solid material such as a brick, or may be an air curtain formed by letting an inert gas flow out in a curtain shape, for example. . In addition, it is preferable that a predetermined gas supply path and a discharge path are independently provided in each partitioned space. In the embodiments to be described later, gas is supplied from the ceiling structure of the bathtub and is configured to be discharged from the discharge pipe and the outlet of the bathtub provided for each space. There is no limit.
[0011]
In a preferred embodiment of the present invention, a partition wall (upper portion of the upper surface of the molten metal bath surface is referred to as a ribbon region) (above the ribbon region) and an upper portion of the region not covered with the glass ribbon (referred to as a ribbon side). A gas with an inert composition that is not reactive with the heater or glass is supplied to the upper space of the ribbon area, and the metal that causes defects of the glass ribbon is supplied to the upper space of the ribbon side. A gas having a reducing composition that is more reactive with oxygen than the molten metal is supplied separately to reduce the oxide or prevent the molten metal from being oxidized.
[0012]
At the same time, the flow of the molten metal is controlled so as to form a groove or ridge of the molten metal near the edge in the width direction of the molten glass flow. The edge of the glass ribbon flow is held in place by compensating for the force to spread or narrow in the width direction. Specifically, the method and apparatus described in European Patent Publication No. 0792842 can be employed.
[0013]
FIG. 1 is a horizontal sectional view of an apparatus for producing sheet glass by the float method, and shows an example in which both edges of a strip glass flow are held at predetermined positions by the method of the present invention. Hereinafter, in accordance with this example, a description will be given of an edge holding method when the strip glass flow is about to narrow in the width direction and vice versa.
[0014]
(1) When the band-shaped glass stream is about to narrow in the width direction FIG. 2 is a cross-sectional view taken along the line AA ′ in FIG. 1, that is, the band-shaped glass flowing over the molten metal bath 2 filled in the molten metal bath 1. 6 is a partial cross-sectional view of the flow 3 in the width direction. FIG. In FIG. 2, when a molten metal flow 5a is generated in the molten metal bath 2 in a direction substantially perpendicular to the bath surface 4 and toward the bottom of the bathtub, a negative pressure is applied to the lower surface of the edge portion 3a of the strip glass flow. Pressure is generated. By this negative pressure, the molten metal bath surface level 4 of the edge portion 3a becomes a bath surface level 4a that is slightly lower than the bath surface level 4b of the central portion. Since the molten glass flows into the lower portion, the thickness of the edge portion 3a becomes thicker than that of the central portion 3b. This thickness deviation becomes an attractive force (arrow 7), and compensates for the force (arrow 6) that the band-like glass flow tends to narrow in the width direction based on the surface tension. As a result, the edge of the glass ribbon stream is held in this position.
[0015]
In this way, the control of lowering the molten metal bath surface level near the edge of the band-shaped glass flow to be lower than that in the central part is, for example, when producing glass thinner than the equilibrium thickness or when the amount of drawn molten glass is large. This is necessary when the attractive force in the width direction of the glass flow is dominant.
[0016]
(2) When the glass ribbon flow is going to spread in the width direction FIG. 3 is a cross-sectional view along the line AA ′ in FIG. 1 as in FIG. 2, but the flow direction of the molten metal is opposite to that in FIG. It is. That is, in FIG. 3, when a molten metal flow 5b is generated in the molten metal bath 2 that is substantially perpendicular to the bath surface 4, a positive pressure is generated on the lower surface of the edge portion 3a. By this positive pressure, the molten metal bath surface level 4 of the edge portion 3a becomes a bath surface level 4a that is slightly higher than the bath surface level 4b of the central portion. Since the molten glass flows out from the higher position, the thickness of the edge portion 3a becomes thinner than that of the central portion 3b. This thickness deviation becomes pressure (arrow 8) and compensates for the force (arrow 9) that the strip glass flow tends to spread in the width direction. As a result, the edge of the glass ribbon stream is held in this position.
[0017]
In this way, the control to make the molten metal bath surface level near the edge of the strip glass flow higher than that of the central portion is, for example, when producing glass thicker than the equilibrium thickness or when the strip glass draw-out amount is small. Necessary when the pressure in the width direction of the glass flow is dominant.
[0018]
The molten metal flow 5a or 5b is formed, for example, by providing a ridge (conduit) extending vertically downward from the edge 3a and flowing the molten metal upward or downward with an appropriate driving means. By adjusting the direction and flow rate of the molten metal flowing through the flow path, the level and the level of the bath surface level in the vicinity of the edge can be controlled, and consequently the force 6 that causes the molten glass flow to narrow in the width direction. Alternatively, an attractive force 7 or a pressure 8 can be produced that is sized to compensate for the force 9 to be spread.
[0019]
More specifically, the flow path is formed by a ridge 10 as shown in FIGS. 2 and 3, for example. The material of the cage may be any material that has low reactivity or no reactivity with the molten metal, and examples thereof include alumina, viscosity, bricks such as sillimanite, and carbon. When a magnetic field is applied to the cage 10 using a linear motor, which will be described later, as the driving means, the material of the cage is preferably a non-magnetic material and a non-conductive material, so carbon or brick is suitable.
[0020]
Examples of the driving means for adjusting the direction and flow rate of the molten metal flowing through the rod 10 include an electric pump and a linear motor. Among these, the molten metal can be directly driven in a non-contact manner and the flow rate can be easily controlled. Therefore, a linear motor is preferable. Here, the linear motor generates a magnetic field that moves in a certain direction by forming a coil on a comb-shaped primary iron core, applying a three-phase AC voltage to the coil, and sequentially magnetizing the coil. For example, it has been put to practical use as a linear induction motor and an electromagnetic pump. For example, when an AC magnetic field of 50 Hz and 75 × 10 ⁻⁴ T is applied to the ridge using a linear motor, the level difference of the molten metal can be provided by about 4 mm. In the present invention, the level difference of the molten metal is usually in the range of 1 to 10 mm, and preferably 1 to 8 mm from the viewpoint of saving energy required for driving the molten metal such as tin.
[0021]
In the present invention, it is preferable to apply a static magnetic field in the vicinity of the edge portion 3a of the belt-shaped glass flow. By stopping the flow of the molten metal in the vicinity of the edge holding portion as much as possible, the shape of the molten metal bath surface is stabilized, and more stable edge holding can be performed. The magnitude of this magnetic field is usually 0.15 T or less, preferably 0.05 T or more.
[0022]
In carrying out the manufacturing method of the present invention, the molten metal level in the vicinity of the edge of the strip glass flow is also measured in the high temperature region (region X in FIG. 1) before the forming region (region Y in FIG. 1). By differentiating the molten metal level in the center of the flow with the method described above, i.e., increasing or decreasing, to compensate for the force of the band-like molten glass stream to spread or narrow in the width direction The edge can be held and widened at a predetermined position.
[0023]
【Example】
Below, the manufacturing method of the glass plate of this invention is demonstrated concretely.
[0024]
The plate glass was manufactured using the plate glass manufacturing apparatus shown in FIGS. 2 and 3, the material of the ridge 10 is carbon. The opening 11 of the tub 10 is located at a position 10 mm from the bath surface level when the molten glass is not flowing into the tank, almost directly below the edge portion 3a of the strip glass flow. In general, a position of 5 to 25 mm is preferred. Moreover, the width | variety of the opening of the collar 10 is 25 mm. In general, a range of 5 to 50 mm is preferable. The opening 11 is arranged at a position where the molten metal flows in and out smoothly and along the edge of the molten glass flow. The vertical portion 10a of the bowl 10 extends downward, bends toward the edge of the bathtub perpendicular to the traveling direction of the strip glass flow at the bottom of the bathtub, and the horizontal portion 10b extends to open.
[0025]
Below the bottom surface of the bathtub of the bowl 10, the linear motor 12 is arranged at a position where a driving force acts on the molten metal in the horizontal portion 10b of the bowl 10. The linear motor 12 can bias the molten metal so that the molten metal inside the bowl 10 flows from directly below the edge portion toward the bath edge or in the opposite direction.
[0026]
In the case of manufacturing a glass plate thinner than the equilibrium thickness, a molten metal flow 5a is generated such that the molten metal is sucked from the opening 11 in the vertical portion. The molten metal bath surface level 4a of the edge portion 3a is slightly lower than the central bath surface level 4b, and the plate thickness of the edge portion 3a is thicker than that of the center portion. This thickness deviation causes an attractive force in the width direction of the strip glass flow, and the edge of the strip glass flow is maintained.
[0027]
Thereafter, the glass ribbon stream is cooled to a temperature at which the plate thickness does not change, and is sent to a slow cooling region downstream.
[0028]
In the case of manufacturing a glass plate thicker than the equilibrium thickness, the linear motor 12 generates a molten metal flow 5b such that the molten metal flows out from the opening 11 in the vertical portion of the cage 10. The molten metal bath surface level 4a of the edge portion 3a is slightly higher than the bath surface level 4b of the central portion, and the plate thickness of the edge portion 3a is thinner than the central portion. This thickness deviation creates pressure in the width direction of the glass ribbon flow, and the edges of the glass ribbon flow are retained.
[0029]
At the same time, the atmosphere above the molten metal bath was controlled as shown in FIGS. 4 is a longitudinal sectional view of the apparatus in the longitudinal direction, FIG. 5 is a horizontal sectional view taken along line II-II ′ in FIG. 4, and FIG. 6 is a transverse sectional view taken along line III-III ′ in FIG. It is. 7 is a horizontal sectional view taken along line IV-IV ′ in FIG.
[0030]
A molten metal bath 2 is accommodated in the bathtub 1, and a molten glass 23 is supplied to the molten metal bath 2 from a lip 36 while being controlled by a twill 35, and is moved forward from the left side in FIG. And is taken out from the outlet 32 on the right. The ceiling structure (roof) 26 of the bathtub 1 is separated by a brick wall (roof brick) constituting the ceiling wall 27 so as to be ventilated from a space developed on the upper part of the molten metal bath 2. As can be seen from FIG. 5 and FIG. 6, the upper space of the molten metal is the upper part of the region covered with the band-shaped glass flow 3 by the partition walls 25 a and 25 b provided perpendicularly above the edge of the band-shaped glass flow 3. It is partitioned into a space A and an uncovered upper space B. The upper ends of the partition walls 25a and 25b reach the ceiling wall 27 and are airtight, but the lower ends do not reach the edge portion of the strip-shaped glass flow 3, and a gap is provided. The size of the gap is preferably about 1 to 300 mm, and is preferably as small as possible without causing troubles in apparatus operation or monitoring. Since this partition wall needs to withstand the high temperature in the bathtub, a refractory material such as silicon carbide, heat-resistant brick, or carbon is desirable. Moreover, the thickness of a partition should just be 1 mm or more, Preferably it is 5-100 mm.
[0031]
The ceiling structure 26 mainly includes a ceiling wall 27 and a casing 28 provided so that a space is formed between the ceiling wall 27 and the space is longitudinally formed by partition walls 29a and 29b corresponding to the partition walls 25a and 25b, respectively. A space a corresponding to the space A and a space b corresponding to the space B are formed. A gas supply pipe 30 is provided in the casing 28, an inert gas is supplied to the space a, and a reducing gas is supplied to the space b. These gases pass through the ceiling wall 27 via the gap between the heater 31 and the ceiling wall 27 and the gap between the ceiling walls 27 and flow into the space A or B on the molten metal bath 2. Since the partition walls 25a and 25b only leave a minute gap between the lower ends of the partition walls 25a and 25b, the gas in the space A and the gas in the space B are substantially not mixed with each other. It is discharged to the outside of the bathtub through the outlet 32 at the rear and the discharge path (discharge pipe 33) provided for each space (A or B). In this way, the upper space of the ribbon region in the bathtub is maintained in an inert atmosphere, and the upper space on the ribbon side is maintained in a reducing atmosphere.
[0032]
As can be seen from FIGS. 4 and 7, in the apparatus of this embodiment, the space in the ceiling structure is also partitioned by a plurality of (three in this embodiment) partition walls 34 in the width direction. These partition walls in the width direction are provided only in the ceiling structure and do not exist in the space on the molten metal bath. The partition in the width direction provided in such a ceiling structure is not essential for the present invention, but is desirable. An iron-based material or the like is used as a material for the partition wall provided in the ceiling structure. For example, a 100% nitrogen gas is supplied to a room corresponding to the upper part of the ribbon region in the bathtub, and a 10% hydrogen gas and 90% nitrogen gas is supplied to the room corresponding to the upper part of the ribbon side in the bathtub. By such a partition in the width direction, the composition and flow rate of the inert gas supplied to the upper space of the ribbon region and the reducing gas supplied to the upper space of the ribbon side are appropriately adjusted according to the progress stage of the strip glass flow. can do. That is, the space a for supplying the inert gas in the ceiling structure is partitioned into rooms a1, a2, a3 and a4 as shown in FIG. 4, and the composition, flow rate, etc. of the inert gas are adjusted for each room. . For example, a gas composed of 100% nitrogen is supplied at different flow rates for each room. Similarly, the space b for supplying the reducing gas is partitioned from the rooms b1, b2, b3 and b4 as shown in FIG. 4, and the composition and flow rate of the reducing gas are adjusted for each room. The reducing gas is usually composed of 4 to 10% hydrogen and 96 to 90% nitrogen. Typically, a gas containing 10% hydrogen and 90% nitrogen is supplied.
[0033]
【The invention's effect】
According to the present invention, since the gas in the upper space of the ribbon region is stably melted with the gas in the upper space on the ribbon side, the volatilized material from the molten metal surface and the above oxide fall on the glass ribbon flow. And can be reliably prevented from adhering.
[0034]
In addition, the composition of the gas in the upper space of the molten metal bath surface covered with the band glass flow is made inert, and the gas in the upper space of the molten metal bath surface not covered with the band glass flow If the composition is made reducible, the ribbon region upper space is made an inert gas atmosphere, and therefore a heater that could not be used in a conventional reductive atmosphere can be used. In addition, a versatile SiC heater can be used without worrying about acceleration of deterioration.
[0035]
In this case, since the upper space of the ribbon region is an inert gas, consumption of reducing gas resources such as hydrogen can be suppressed, which is advantageous in terms of cost.
[0036]
Furthermore, since the space for reducing gas atmosphere is only the upper part of the ribbon side, for example, when using the same amount of reducing gas as the conventional method, the reducing gas concentration in the upper space of the ribbon side is greatly increased. As a result, the use efficiency of the reducing gas is improved, such as the effect of preventing the oxidation of the molten metal and the effect of reduction (purification).
[Brief description of the drawings]
FIG. 1 is a horizontal sectional view of a sheet glass manufacturing apparatus according to the present invention.
FIG. 2 is a cross-sectional view taken along the line AA ′ in the apparatus of FIG.
FIG. 3 is a cross-sectional view taken along the line AA ′ in the apparatus of FIG. 1;
FIG. 4 is a longitudinal sectional view in the longitudinal direction of an example of a glass sheet manufacturing apparatus according to the present invention.
5 is a horizontal sectional view of the manufacturing apparatus taken along line II-II ′ in FIG. 4;
6 is a transverse sectional view taken along line III-III ′ in FIG. 5 of the manufacturing apparatus.
7 is a horizontal sectional view taken along line IV-IV ′ in FIG. 4 of the manufacturing apparatus.
[Explanation of symbols]
2: Molten metal bath 3: Strip-shaped glass flow 3a: Glass edge holding part 10: Saddle

Claims (4)

  A method for producing plate glass comprising a step of continuously supplying molten glass to a bath surface of molten metal contained in a bathtub to form a strip-shaped glass flow, and advancing the strip-shaped glass flow to form a predetermined width and thickness. The molten metal flow is controlled so as to form a molten metal groove or ridge in the vicinity of the widthwise edge of the molten glass flow, and a force that causes the glass strip to spread in the width direction by the groove or ridge or The edge of the glass ribbon flow is held in place by compensating for the narrowing force, and the atmosphere in the upper space of the molten metal bath surface covered by the glass ribbon flow is A method for producing a plate glass, characterized in that it is substantially shielded from the atmosphere in the upper space of the region not covered with the strip glass flow.   The method according to claim 1, wherein the composition of the gas in the upper space of the molten metal bath surface covered with the strip glass flow is an inert composition, and the molten metal bath surface is covered with the strip glass flow. A manufacturing method in which the composition of the gas in the upper space of the unexposed region is a reducing composition. An apparatus for producing plate glass, which supplies molten glass onto a molten metal bath accommodated in a substantially sealed bath, advances the molten glass as a strip-shaped glass flow, and forms the glass into a predetermined width and thickness, in the molten metal bath, generally along the edges of the ribbon flow, substantially above the edge portion of the molten metal balloon or suction lead straight direction capable blowout-suction means is provided and also ribbon stream And a partition for separating the upper space of the region covered with the strip glass flow of the molten metal bath surface and the upper space of the uncovered region substantially along the edge. 4. The apparatus for producing sheet glass according to claim 3, wherein the composition of the gas in the upper space of the molten metal bath surface covered with the strip glass flow is an inert composition, and the strip glass flow of the molten metal bath surface. An apparatus for producing plate glass in which the composition of the gas in the upper space of the region not covered with is a reducing composition.

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