WO2008110572A1

WO2008110572A1 - Float bath device and method for producing flat glass

Info

Publication number: WO2008110572A1
Application number: PCT/EP2008/052943
Authority: WO
Inventors: Klaus Jochem; Katharina Mertens; Arnulf Fendel; Andreas Roters; Andreas Langsdorf; Michael Vogel; Carsten Schumacher
Original assignee: Schott Ag
Priority date: 2007-03-13
Filing date: 2008-03-12
Publication date: 2008-09-18
Also published as: JP5415291B2; JP2010520848A; KR101477312B1; KR20100015548A; DE102007011899B4; DE102007011899A1

Abstract

The invention relates to a float bath device with a cover having at least one cover element (30, 32). A float bath (16) comprising liquid metal is present in a float bath tub (12) with a bottom wall (13) and side walls (14). The float bath device is used for the production of a glass sheet (28) floating on the float bath (16). The cover element (30, 32) is arranged in at least one partial region of the open float bath surface and has an intermediate space (36) spaced from the float bath level (17). The partial region is located between the glass sheet (28) and the side wall (14). Furthermore, a method for producing flat glass is proposed. The device (10) comprises a suction device with a suction line (40), wherein the suction opening (41) of the suction line (40) ends in the intermediate space (36).

Description

Float bath apparatus and method of making float glass

The invention relates to a float bath apparatus according to the preamble of patent claim 1 and to a method for producing flat glass according to the preamble of patent claim 46.

The production of flat glass by the float process, so-called float glass, has been known since the last century and is essentially based on the fundamental industrial property rights of Pilkington (US Pat. No. 3,083,551, DE 147 19 50).

In the float process, liquid glass, which is produced by means of a trough from the working trough, is allowed to flow onto a bath of molten metal, generally tin. The flow rate of the glass is controlled by a movable slide, with its setting, among other things, the glass thickness is set. As seen in the direction of flow of the glass behind the slide is the pouring lip, from which the molten glass flows continuously to the metal bath, where the glass melt is formed into a dimensionally stable glass ribbon and solidifies. Subsequently, the solidified glass ribbon is removed from the metal bath.

The float glasses produced in this way, which generally have a thickness of less than 1, 5 mm, are used as thin glass substrates, inter alia, for the production of flat screens, z. Plasma Display Panels (PDP), Field Emission Display (FED), Thin Film Transistor (TFT) Liquid Crystal Displays (STN), Super Twisted Nematic (STN) Liquid Crystal Display (STN) Plasma Assisted Liquid Crystal Displays (PALC = Plasma Assisted liquid crystal), electro-luminescence displays (EL) and the like or for the production of thin-film solar cells.

In the flat panel displays, depending on the type of display, either a thin layer of liquid crystal compound is sandwiched between two sheets of glass or dielectric layers are formed on the front and back surfaces of the back and front sheets, respectively, from which cells are formed containing phosphors ,

It is important in this case that the layer thickness of the liquid-crystal layer or the thickness of the dielectric layer is exactly adhered to, so that no disturbing color distortions or similarity deviations occur, in particular for large dimensions of a screen. Since the layer thicknesses, currently about 30 microns, smaller and smaller and the screens are getting bigger, this condition is becoming increasingly important.

Although float glass is excellently suited for display applications due to its fire-polished surface, it is not yet possible to produce display glass according to the float process, the thickness differences of which are below 50 μm in today's large substrate formats with edge lengths of over 1800 mm.

One explanation for the development of thickness variations in float glass is the presence of flows in the float bath. These very complex flows are the result of interacting mechanically and thermally induced flows. In this respect, the temperature control within the Floatbadvorrichtung is of considerable importance. The surface quality of the float glass is affected by surface defects, which are referred to as top bacons, the use of a tin bath by deposits of tin-containing particles, such as. As tin or tin oxide particles are caused on the glass ribbon. Despite the flooding of the interior with forming gas (typical composition 12% H ₂ , 88% N ₂ ), the atmosphere above the float bath contains residual amounts of oxygen which penetrate into the tin bath and form SnO ₂ particles there. With increasing bath temperature, the tin oxide or tin evaporates and enriches the atmosphere, with the result that tin-containing particles can precipitate on the glass ribbon.

To avoid these surface defects, various measures must be taken to prevent a contaminated atmosphere above the glass ribbon. On the one hand, in particular, no oxygen may penetrate from the outside into the interior of the float bath housing and, on the other hand, any oxygen present may not come into contact with the tin bath surface.

In JP 11-278856 the tin oxidation is proposed to prevent, cover the free Floatbadoberfläche by plates O ₂ should be impermeable and withstand temperatures of 1300 ⁰ C or more. As a material carbides, such as silicon carbide, are proposed.

The plates are placed directly on the Zinnbadoberfläche so that there is no atmosphere under the cover. Since such a floating cover must be kept at a distance from the edge of the glass band, there are free surface areas of the float bath at the sides of the glass band, where tin oxidations can still take place. From WO 2005-097692 it is known to suck the atmosphere and thus the tin oxide particles by means of suction tubes, which are arranged in the side wall. The disadvantage of these suction tubes is that the range of action is extremely limited. In general, a significant suction effect is achieved at best within a radius of about 20 cm around the inlet opening of the suction tube. Significant shares of tin oxide or other contaminants in the atmosphere are not covered.

Covering elements are known from US Pat. No. 3,494,755 and DE 40 21 223 C2, which are arranged at a distance from the glass band above the glass band. In general, the width of the glass ribbon is large versus the width of the free tin bath surfaces to the left and right of the glass ribbon. Accordingly, the structural complexity associated with US Pat. No. 3,494,755 and DE 40 21 223 C2 is relatively large.

According to GB 1 217 047 suction openings are arranged above the edge of the glass band. In this arrangement, in the region immediately above the free metal surface, a flow in the forming gas, which is directed towards the glass ribbon out. As a result, the forming gas with the highest concentrations of vaporized, metal-containing gases is sucked towards the glass ribbon. Thus, in this known embodiment, the risk of surface defects on the glass ribbon is comparatively high.

The object of the invention is to provide a float bath apparatus with which the number and / or size of the surface defects on the glass ribbon, which is produced by the float process, can be reduced. It is also an object of the invention to provide a corresponding method for producing flat glass. This object is achieved with a floating bath apparatus in which the cover member is disposed at least in a portion of the free float bath surface located between the glass ribbon and the side wall with a space spaced from the float bath mirror and wherein means for aspirating one inside the apparatus located atmosphere is provided with at least one suction line, wherein the suction opening of the suction line opens into the intermediate space.

Under a cover preferably all elements are understood that delimit the free Floatbadoberfläche in the vertical direction from the overlying space.

The spaced array of cover members forming a gap between the cover member and the float bath mirror provides the opportunity to adjust an atmosphere flow, as described in detail in the context of the method for producing flat glass.

Another advantage is that the contaminated in particular with metal oxide atmosphere space is limited to the gap and thus kept small.

In addition, the flow velocities under the cover elements can be set much higher than is possible, for example, in the arrangement of curtains within the interior of the Floatbadgehäuses. Due to the comparatively higher flow velocities in the direction of the suction openings, an undesirable spread of the contaminated atmosphere into the region above the glass ribbon can be better avoided than through the use of curtains. Another advantage is that the cover does not interfere with the clear view of the glass ribbon and especially the edge of the glass ribbon during manufacture.

Another advantage of the cover of the invention is that the contaminated atmosphere is prevented from rising from the free float bath surface and from entering the space above the glass ribbon. In comparison with US Pat. Nos. 3,494,755 and DE 40 21 223 C2, the associated construction costs are significantly lower.

By means of the suction device, the atmosphere consisting essentially of forming gas is sucked out of the interior of the float bath housing into the intermediate space. Due to the generated flow in the space particles are sucked in the entire area between the glass ribbon and the side wall. Depending on how far extends the cover to the edge or even over the edge of the glass ribbon, a horizontal flow is generated at least over portions of the glass ribbon and in this way, the harmful gases, droplets and particles are sucked, the are in the atmosphere above the glass ribbon.

A further advantage is that, due to the improved suction effect and flow guidance, a total of less forming gas is required in order to prevent metal oxide formation or to remove the harmful gases, droplets and particles.

Preferably, the suction opening has a horizontal distance A ₇ to the glass band edge in the direction of the nearest side wall of at least 100 mm. In particular, the distance A _{7 is} at least 120 mm and more preferably at least 150 mm. Preferably, the suction opening is in the side wall and / or in the cover.

Preferably, the cover consists of Quarzal. Quarzal has the advantage that it can be installed during operation, ie in a hot atmosphere, because it has a good thermal shock resistance. Further advantages are due to the mechanical stability and the property that it does not thermally isolate and thus does not cause temperature differences within the Floatbadgehäuses.

Other suitable materials for the cover are ceramics, such. As mullite, silimanite, SiC, Si ₃ N ₄ , AITi, C, Al ₂ O ₃ or coated with SiC graphite. An advantage over the cover proposed in US Pat. No. 3,494,755 is that in the case of the cover proposed here, no restrictions with regard to wettability with the condensates of the vaporized metals or metal oxides have to be taken into account when selecting the material.

According to a first embodiment, the cover element has at least one support which rests on the bottom wall of the float bath tub. The length of the support is chosen so that the desired gap between the Floatbadspiegel and the bottom of the cover is respected.

According to a second embodiment, the cover element has at least one floating body with which the cover element floats on the float bath at a distance. The size of the float and its buoyancy are adjusted so that the desired distance of the cover from the Floatbadoberfläche is met. Both the support and the float are preferably made of mullite. Further preferred materials are SiC coated graphite, quartz, chamotte, Al ₂ O ₃ or ceramics, which are also used for the cover.

In particular, provided with the float cover member is preferably fixed by means of a holding device. Due to unavoidable currents in the float bath, it could otherwise lead to displacements of the cover.

Preferably, the cover extends to the side wall. This avoids return flows of the atmosphere gas, in particular flows towards the float bath cover and the glass ribbon.

Preferably, the cover is sealingly against the side wall. This embodiment effectively prevents oxygen permeating through the sidewall from creeping down the inside of the sidewall from coming into contact with the metal bath, thus producing metal oxide particles.

According to a further embodiment, the cover member between side wall boxes and the side wall of the Floatbadwanne be held. The cover elements may for example be clamped between the side wall boxes and the side wall.

Another embodiment provides that the cover is suspended from the ceiling of Floatbadgehäuses.

Preferably, the distance Ai between the edge of the glass ribbon and the edge of the cover is 0 <Ai <500 mm. Particularly preferred is a distance A ₁ with 150 mm <Ai <300 mm, in particular 200 mm <Ai <300 mm.

Preferred embodiments of the cover are cover plates and covers. The distance A ₂ between the underside of the cover plate and the Floatbadspiegel is preferably 25 mm to 100 mm, more preferably 50 mm to 100 mm. By way of the distance between the cover plate and the float bath mirror, the flow rate in this intermediate space can be set for a given suction power of the suction device, which is described in connection with the float bath device.

According to a further embodiment, it is possible to arrange the cover elements at a distance A ₅ to the side wall. However, the distance A ₅ should not be selected to be greater than the distance Ai in order to prevent vaporized metal from spreading from the free float bath surface in the region between the side wall and the cover element into the region above the cover element and finally into the region above Glass bands to avoid. Also in this embodiment, the suction opening of the suction opens into the space between the Floatbadoberfläche and the cover.

In all embodiments of the cover it should be noted that the associated suction opening has a horizontal distance A ₇ to the edge of the glass ribbon, which is preferably at least 100 mm. The horizontal distance A ₇ denotes the distance of the suction opening from the glass band edge in the direction of the nearest side wall. The cover can be roof-like or semi-pyramidal and is used in particular as a cover where the suction pipes of the suction open into the interior of the Floatbadgehäuses. The space under the covers is much larger than under the cover plates.

Preferably, the distance between two adjacent covering elements arranged along one side wall is 0 <A ₆ ≦ 500 mm.

At least two adjacent cover elements arranged along the side wall can adjoin one another directly.

The cover elements in a load bath section preferably cover at least 50% of the free surface of the load bath.

The cover elements are preferably arranged in the hotter region of the load bath at least in a load bath section.

The cover elements are preferably arranged in the hot region of the charging bath at least over a length of 50% of the length of the loading bath.

The distance between two adjacent cover elements, ie covering elements, which are arranged along the same side wall, should be as small as possible. Preferably, the cover should be connected to each other gas-tight. In a spaced embodiment, however, the distance A ₆ between the adjacent cover elements should not be greater than the distance Ai between the glass band edge and the cover. Preferably, at least 50% of the free metal surface is covered by the cover elements in a float bath section. The cover elements preferably cover over 75%, in particular also the entire free metal surface in a float bath section.

The "covered" area is preferably to be understood as that area which results from a vertical projection of the surface of the covering element onto the free metal surface.

In this arrangement, the Abdeckelemente and suction, the Formiergasatmosphäre is sucked over the entire surface of the metal bath, so that no dead spaces can arise in which accumulate the harmful particles and may possibly rise up within the Floatbadgehäuses. From there, the particles generally return down the center of the housing and settle on the glass ribbon. An installation of cover preferably in the front, hot area of the float bath, preferably along both side walls, as well as a large-scale extraction at least in the hot area, but possibly also along almost the entire length of the side wall, in particular on both side walls, prevents this adverse effect and leads to a significant decrease of the so-called top-bacon.

Preferably, at least one suction duct is arranged in a side wall boxes, which is insertable into the side wall. The arrangement of the suction tubes or in the side wall boxes allows a quick replacement of the suction tubes, for example, if smaller or larger tube cross-sections or a larger or smaller number of suction tubes is needed. Such an adjustment may become necessary if, under certain circumstances should change the temperature conditions within the Floatbadgehäuses.

Preferably, the suction opening is a slit opening extending in the horizontal direction.

The advantage of the slot opening is that the Formiergasatmosphäre is sucked over a large-scale, contiguous area above the float bath. Harmful gases, droplets and particles in the Formiergasatmosphäre are detected more effectively and completely than with round suction tubes, which are distributed over greater distances along the side walls of the Floatbadgehäuses.

Such a slot-shaped suction opening can be arranged at a smaller distance above the Floatbadspiegel, so that opens the possibility to directly suck the atmosphere from the space between the Floatbadoberfläche and the underside of a cover without covers must be provided, as for example in round suction tubes with a relatively large cross-section is necessary.

Another advantage is that by means of a slot nozzle opening over the entire length of the slot opening uniform flow is generated, so that local backflow from the gap between the cover and the Floatbadoberfläche in the remaining area of the Floatbadatmosphäre and thus potentially in the area above the Glass bands are avoided.

Preferably, in at least one float bath section above the free float bath surfaces located on both sides of the glass ribbon each arranged at least one cover. It is preferably at least one float bath section in the region of the float bath in which the highest temperatures occur. Preferably, at least one slot opening is located in each of the two associated opposite side walls. This ensures that, starting from the center of the glass band immediately above the glass band, flows on both sides are used in each case to the intermediate space below the nearest cover element and the free float bath surface. In particular, in the areas immediately above the glass band edges and the adjacent free metal surface, the flows are directed away from the glass band and in the space below the cover into it. As a result, a transport of the vaporized, metal-containing gases and harmful particles from the Formiergasbereich with high concentrations of vaporized, metal-containing gases in the area above the glass ribbon task largely prevented.

Preferably, the cover elements and / or the associated slot openings are arranged at least in the first two Floatbadabschnitten. In the Floatbadabschnitten where the hot forming takes place - these are in particular the Floatbadabschnitte 1 and 2, optionally also Floatbadabschnitt 3 - the temperature of the float bath is highest, so there is the enrichment of the atmosphere with harmful particles is greatest. By means of the extraction via slot openings, in particular in these float bath sections, the effectiveness of the decontamination of the atmosphere can be significantly increased.

Preferably, at least two slot openings are arranged in the horizontal direction next to one another. The distance between two slit openings should be minimized as far as possible and should be less than 10 cm so as not to allow any dead spaces in which harmful particles can not be detected by the extraction system.

Preferably, the slot openings extend a total of at least 50% of the length of a Floatbadabschnittes. Preferably, the slot openings extend over at least 70%, more preferably over at least 80% of the length of the float bath section.

Preferably, the slot openings extend a total of at least 30% of the length of the entire float bath. Preferably, the slot openings extend over at least 50%, in particular over 80% of the length of the entire float bath.

Preferably, the horizontal length of the slot opening is 30 cm to 150 cm.

The cross-sectional area of the slot opening is advantageously 20 to 40 cm ² . This means that in the claimed lengths of the slot openings, the vertical width of the slot opening may be in the range of 2 to 10 mm. By maintaining these values, a uniform flow over the entire length of the slot opening is maintained within the slot opening.

The slot opening should be arranged as close as possible to the metal bath surface in order to be able to extract as much of the particles as possible.

Preferably, the lower edge of the slot opening is located between 4 cm and 8 cm above the mirror of the float bath. Preferably, the suction line in the side wall on a slope from the inside out. This has the advantage that in the suction condensed particles drain to the outside and thus can not contaminate the metal bath.

Preferably, the suction line has a slot nozzle. Slot nozzles essentially have a triangular shape in plan view. Towards the outside, the cross section tapers and merges into the cross section of the connected suction line. In the side view, the cross-section expands starting from the slot opening at the transition to the cross-section of the connected suction line. The slot nozzle may be a separate component or may be integrally formed on the suction tube forming the suction line.

A slot-shaped nozzle can be arranged at a small distance above the Floatbadspiegel, so that opens the possibility to suck the gas atmosphere immediately above the float.

Preferably, in the slot nozzle for the taper an opening angle a of 14 ° to 40 °, preferably 18 ° to 35 °, more preferably 20 ° to 30 ° and for the expansion of an opening angle ß of 2 ° to 10 °, preferably 3 ° to 8 °, particularly preferably 5 ° to 7 °, to ensure a uniform over the length of the slot flow within the slot nozzle, while keeping the pressure losses as low as possible and to avoid dead spaces with the risk of deposition of condensates. The angle a is in this case the angle between the tapered side walls of the slot nozzle in plan view and the angle ß of the angle between the side walls of the slot nozzle in the side view. Preferably, the slot nozzle is arranged in a side wall boxes.

The side wall box preferably has two shaped blocks, in particular of refractory material, which delimit at least the slot nozzle. The slit nozzle is formed in this case in the mold bricks, wherein preferably the dividing line between the two shaped bricks passes through the slit nozzle.

Preferably, a plurality of suction lines are arranged distributed along the two side walls. The suction power through the suction lines is preferably individually adjustable via the corresponding suction means. This embodiment offers the advantage that the different temperature conditions inside the float bath housing can be easily taken into account. Thus, in the hotter areas, a larger volume of gas per unit time can be extracted than is necessary in the colder sections.

The arrangement of a suction or multiple suction lines in the sidewall box allows quick replacement of the suction lines, for example, if smaller or larger cross sections or a larger or smaller number of suction lines in the respective side wall area are needed. Such an adaptation may become necessary if, under certain circumstances, the temperature conditions within the float bath housing and thus the concentration of the particles should change.

The suction device preferably has an injector pump. The injector pump generates a negative pressure at the outlet of the suction line. Injector pumps have two inputs and one output and consist in principle of two nested tubes, which are referred to as inner tube and outer tube. The inner tube ends in the outer tube and has an outlet nozzle. The suction fluid exits under the full line pressure from the outlet nozzle in the outer tube and thereby tears the fluid to be sucked, ie the Formiergasatmosphäre from the second input. This happens due to the generated negative pressure. For example, a water jet pump works according to this principle.

Since the suction power of the injector pump can be easily adjusted with high accuracy via the pressure of the suction fluid, the desired adaptation to the different concentrations of the particles in the interior of the floating bath housing is possible. The accuracy is ± 5 m ³ (i.N) / h. The term m ³ (i.N) is understood to mean a standard cubic meter, which is specified in DIN 1343. A standard cubic meter is the quantity corresponding to one cubic meter of gas at a pressure of 1, 01325 bar, a humidity of 0% (dry gas) and a temperature of ⁰ ° C.

Preferably, the injector pump is operated with compressed air as a suction fluid. Accordingly, the injector pump is preferably connected to at least one compressed air generator.

Furthermore, the compressed air generator may be connected to a control device for controlling the pressure of the compressed air or the compressed air generator has such a control device.

It is also possible that a control device for controlling the pressure of the compressed air is arranged between the injector pump and the compressed air generator. Such a control device can for example, be a compressed air valve. Preferably, such a compressed air valve is arranged in front of each injector pump so that each injector pump can be adjusted individually.

One or more suction lines can be connected to an injector pump. The group-wise arrangement of suction lines lends itself to when the suction power of each Floatbadabschnittes should be set individually. If a plurality of suction lines are provided within a Floatbadabschnittes to be sucked through the individually set gas quantities per unit time, preferably each suction is connected to a separate injector.

The control device is preferably connected to at least one temperature sensor, which is arranged in the interior of the float bath. The corresponding temperature changes can thus be implemented directly via the control device in the relevant suction, which is necessary to ensure optimal extraction of the particles.

Preferably covers are arranged in the region of the openings of the suction tubes, which is particularly advantageous if the diameter of the opening of the suction tubes is greater than the distance of the cover plates of the Floatbadoberfläche.

Flat glass made in a float bath apparatus of the invention shows a significantly lower number of surface defects. The number of surface defects per m ² could be reduced on average from 50 - 100 top bacon / m ² to 0 - 20 top bacon / m ² . In addition, it has been found that the distribution of the size of the surface defects shifts to small diameters. The method for producing flat glass, in particular TFT glass, in such a float bath apparatus is characterized in that at least part of the free float bath surface located between the edge of the glass ribbon and the adjacent side wall is covered by a cover to form a gap and that a flow of the atmosphere is generated in the gap.

This flow is as low as possible in terms of potential, local backflow from the gap back into the rest of the Floatbadatmosphäre.

The flow is preferably directed away from the glass ribbon so that the vaporized gases of the metals or metal oxides, and the droplets or particles formed from these gases by condensation, solidification, sublimation or possibly also by chemical reactions with further impurities are sucked from the glass ribbon surface.

The atmosphere is sucked out of the gap to the outside, so that they can not flow back into the interior.

Preferably, the mean velocity of the flow at the leading edge into the gap between the cover member and the free float bath surface is set at 0.1 m / s to 10 m / s.

Preferably, the atmosphere is sucked slit-shaped in the horizontal direction.

Preferably, the atmosphere is sucked off via at least one slot opening. It is preferable to perform the extraction at several points along the Floatbadvorrichtung, wherein in at least two Floatbadabschnitten (Bays) of the Floatbadwanne the Formiergasatmosphäre is sucked.

Preferably, the atmosphere, preferably at both sidewalls of the Floatbadgehäuses, sucked off over at least 50%, in particular at least 70%, more preferably over at least 80% of the Floatbadlänge.

It is also advantageous that the amount of gas extracted in each Floatbadabschnitt per unit time is set in dependence of the temperature of the Floatbadabschnittes.

The method is particularly suitable for the production of borosilicate glasses, alkali-free glasses, aluminosilicate glasses, Alumolithiumsilikatgläsem and precursor glasses for glass-ceramic.

Particularly suitable is the method for producing borosilicate glass, z. For fire protection applications, having a composition of (all the below expressed in% by weight based on oxide):

SiO ₂ 70-85, B ₂ O ₃ 7-13, Na ₂ O + K ₂ O + Li ₂ O 3-8, MgO + CaO + SrO 0-3, Al ₂ O ₃ 2-7,

for the preparation of alkali-free alumino (boro) silicate glass with a composition of

SiO ₂ 50-70, B ₂ O ₃ <15, Al ₂ O ₃ 10-25, MgO 0-10, CaO 0-12, SrO 0-12, BaO O-15, with MgO + CaO + SiO + BaO 8 -26, ZnO 0-10, ZrO ₂ 0-5, TiO ₂ 0-5, SnO ₂ 0-2, z. B. for the production of display glass, in particular with a composition of

SiO ₂ > 55-65, B ₂ O ₃ 5-11, Al ₂ O ₃ > 14-25, MgO 0-8, CaO 0-8, SrO 0-8, BaO ≤ 10 with MgO + CaO + SrO + BaO 8-21, ZnO 0-5, ZrO ₂ 0-2, TiO ₂ 0-3, SnO ₂ 0-2,

in particular SiO ₂ > 58-65, B ₂ O ₃ > 6-10.5, Al ₂ O ₃ > 14-25, MgO 0 - <3, CaO 0-9, BaO> 3-8 with MgO + CaO + BaO 8-18, ZnO O - <2, As ₂ O ₃ -free, Sb ₂ O ₃ -free,

preferably Zn-oxide, Ce-oxide, Zr-oxide, Ti-oxide free.

It is also particularly suitable for the production of various green glasses for glass-ceramic, such. B. with

SiO ₂ 55-69, Al ₂ O ₃ 19-25, Li ₂ O 3 - 5, Na ₂ OO - 1, 5, K ₂ O 0-1, 5, INa ₂ O + K ₂ O 0.2-2 , MgO 0.1-2.2, CaO 0-15, SrO 0-1.5, BaO O - 2.5, Σ MgO + CaO + SrO + BaO below 6, ZnO 0-1.5, TiO ₂ 1 - 5, ZrO ₂ 1 - 2.5, SnO ₂ O to less than 1, Σ TiO ₂ + SrO ₂ + SnO ₂ 2,5 - 5, P ₂ O ₅ 0-3

or a glass-ceramic precursor glass having a composition of

SiO ₂ 55-75, Al ₂ O ₃ 15-30, Li ₂ O 2.5-6, Σ Na ₂ O + K ₂ O less than 6, Σ MgO + CaO + SrO + BaO less than 6, B ₂ O ₃ O to less than 4, ΣTiO ₂ + ZrO ₂ less than 2

or a glass-ceramic precursor glass having a composition of

SiO ₂ 60 - 72, Al ₂ O ₃ 18-28, Li ₂ O 3 - 6, Σ Na ₂ O + K ₂ O 0.2 - 2, Σ MgO + CaO + SrO + BaO less than 6, ZnO O - 1 , 5, B ₂ O ₃ O to less than 4, SnO 0.1 - 1, 5, ΣTiO ₂ + ZrO ₂ less than 2, P ₂ O ₅ O - 3, F 0-2. Exemplary embodiments of the invention are explained in more detail below with reference to the figures.

Show it:

Fig. 1 is a plan view of a float bath with glass ribbon and

Cover;

2a shows a section through the float bath tub shown in Figure 1 along the line A-A, wherein additionally the float bath roof is shown ..;

FIG. 2b shows a section through the float bath tub shown in FIG. 1 along the line B-B, wherein additionally the float bath roof is shown; FIG.

Fig. 3 is an enlarged view of a cover in section;

4 is an enlarged view of a cover in section according to another embodiment.

5 is a perspective view of part of a cover according to the invention;

Fig. 6 is a section along the line C-C shown in Fig. 5

Cover;

Fig. 7 is a plan view of a float bath with glass ribbon

suction; Fig. 8 is a side view of a section on a

Side wall of a Floatbadgehäuses;

Fig. 9 is a section along the line D-D in Figure 8;

Fig. 9a is a section corresponding to Figure 9 according to another

embodiment;

Fig. 10 is a section corresponding to Figure 9 according to another

embodiment;

11 is a perspective view of a

Sidewall box;

Fig. 12 is a horizontal section through that shown in Fig. 11

slot; and

13 is a partial vertical section through the edge of a

Floatbadvorrichtung with an injector pump.

Fig. 14 is a plan view of a section of the float bath

Figure 1 according to another embodiment

Fig. 15 is an enlarged view of a cover in section according to another embodiment

FIG. 1 shows the top view of a float bath tub 12 which is subdivided into sections which are provided with so-called bay numbers 1 to 8. The float bath tub 12 is filled with a float bath 16 of liquid metal, in particular tin. On the float bath 16 floats a glass ribbon 28, which is pulled off in the direction of the arrow. The area between the edge 29 of the glass ribbon 28 and the Side walls 14 of the float bath tub 12 is covered by a cover. This cover consists of cover elements in the form of cover plates 30. In addition, suction lines 40 of a suction device are shown in the side walls 14.

FIG. 2 a shows a section through the float bath tub 12 of a float bath apparatus 10 along the line A-A shown in FIG. 1, wherein additionally a section through the float bath roof 18 with top wall 19 and side walls 20 can be seen. In the top wall 19 Formiergaszuführungen 22 are provided, is introduced by the forming gas into the interior of the Floatbadvorrichtung 10.

In addition to the representation of FIG. 1, top rollers 26 are shown, which are required for pulling the glass band 28 apart in the direction perpendicular to the direction of movement of the glass band 28. It can be seen that the cover plates 30 are located below the top roller axes. It can also be seen that the edge of the cover element 30 is arranged at a distance from the edge 29 of the glass ribbon 28.

The cover plates 30 are arranged at a distance from the float bath mirror 17, so that a gap 36 is formed between the float bath mirror 17 and the underside of the cover plates 30.

FIG. 2 b shows a section along the line BB of the float bath tub 12 shown in FIG. 1, the section running through the suction tubes which are arranged in the side wall boxes 24 and form the suction lines 40. Since the suction tubes are arranged at a greater distance from the Floatbadoberfläche than the gap 36 allows special cover elements are provided in the form of covers 32, which allow the connection of the suction tubes to the gap 36. In Fig. 3 is an enlarged view of a cover plate 30 can be seen. In addition, the distance Ai between the edge 34 of the cover plate 30 and the edge 29 of the glass ribbon 28 is shown. The distance between the Floatbadspiegel 17 and the underside of the cover 30 is marked with A ₂ . Due to the distance Ai, it is possible, the edge 29 of the glass ribbon 28 during production z. B. by means of a camera, which may be of importance for the manufacturing process.

But it is also possible the cover plate 30 to extend to the edge 29 of the glass ribbon 28 or beyond, when a particular flow, which is indicated by the arrows, to be adjusted in the space or in the space 36. In the embodiment shown in Fig. 3, the cover plate 30 has supports 38 which rest on the bottom wall 13 of the float bath tub 12. The lengths of the supports 38 are chosen so that the desired distance A _{2 is} maintained.

4, a further embodiment is shown, in which the cover plate 30 is provided with a floating body 39, so that the cover plate floats at a predetermined distance A ₂ on the tin bath 16. For fixing a holding device 31 is provided, which presses from above on the cover plate 30 and which is fixed to the side wall 14.

5, a perspective view of a section of the cover is shown. In addition to the cover plates 30, which are held between the side wall 14 and the side wall boxes 24, covers 32 are shown, which are formed partially pyramidal and consist essentially of two erected triangular plates. This will make it possible in the Side wall boxes 24 arranged suction lines 40 to be arranged at a greater distance from the Floatbadspiegel 17 and still allow a connection between the gap 36 under the cover plate 30 so that an extraction of the atmosphere from the gap 36 is possible.

FIG. 6 shows a section along the line C-C through the arrangement shown in FIG. It can be seen that the gap 36 under the cover plate 30 continues into the gap 36 'below the cover 32, allowing flow from the gap 36 into the gap 36' and from there through the inlet 41 into the suction tube 40 becomes.

FIG. 7 once again shows a plan view of a float bath trough 12 in order to explain the suction device 50. In the side walls of the Floatbadvorrichtung 10 suction lines 40 of the suction device 50 are arranged in the form of suction tubes, with only a portion of the suction lines 40 are drawn in for clarity. In Bay number 2, a suction line 40 is shown in the right side wall, representative of further suction lines, which is connected to an injector pump 60, which is supplied by a compressed air generator 80 via a compressed air line 69. To control the compressed air, a control valve 84 is provided in front of the injector pump 60 as a control device. The control of the valve 84 may be manual or electrical.

Bay number 3 also has a suction line 40 and bay number 4 shows two suction lines 40. The two suction lines 40 from Bay 4 are connected to a common Injektorpumpe 60. Both injector pumps 60 for Bay 3 and Bay 4 are connected via a common compressed air line 69 to the compressed air generator 80, which is electrically connected to a control device 82 is. This control device 82 is connected via an electrical connecting line 72 with temperature sensors 70, which are arranged on the inside of the side walls 14 of the Floatbadgehäuses 11. The embodiments shown in FIG. 1 merely represent examples of applications of suction lines 40 and injector pumps 60 as well as of control valves 84 and control devices 82.

FIG. 8 shows a detail of a side wall 20 of the float bath housing 11. It is a side view of the inner surface of the side wall 20, which in the area shown consists of side wall boxes 24 which are arranged on the side wall 14 of the float bath tub. Each side wall boxes 24 has a slot-shaped suction opening 41. The slot-shaped suction openings 41 are arranged close to each other with a distance of less than 10 cm and close above the mirror 17 of the metal bath 16 at a distance of about 5 cm. The suction openings 41 are located in the lower region of the side wall boxes. The dense arrangement of the slot-shaped suction openings 41 has the advantage that the Formiergasatmosphäre can be sucked off almost over the entire region of the side wall without dead spaces arise in which the harmful particles can accumulate.

FIG. 9 shows a section along the line D-D through the side wall 20 shown in FIG. The slot-shaped suction opening 41 belongs to the suction line 40, which tapers horizontally with respect to the cross section to the cross section of the outer suction tube 53.

FIG. 9 a shows a further embodiment in which the suction line 40 widens vertically with respect to the cross section β to the cross section of the outer suction tube 53. In the figure 10, a further embodiment is shown, in which the suction line 40 within the side wall box 24 has a slope to the outside. Sucked particles can condense within the sidewall box 24 and thus within the suction line 40 to droplets. Due to the gradient, these condensed particles can not get back into the Floatbadgehäuse 11 and thus into the metal bath 16, but these condensed droplets flow out into the outer suction pipe 53 from.

FIG. 11 shows a perspective view of a side wall box 24 which, in the embodiment shown here, is formed from two refractory shaped bricks 123 and 124. In these stones 123, 124 a slot nozzle 42 is formed. The dividing line 125 between the two shaped bricks 123, 124 extends through the slot nozzle 42, which brings with it corresponding manufacturing advantages. A horizontal section through the slot nozzle 42 is shown in FIG. It can be seen that the opening angle a of the slot nozzle 42 is defined by the two boundary walls of the slot nozzle 42. This angle is in the representation shown here at a = 20 °.

FIG. 13 shows a partial vertical section through a float bath tub 12 with bottom wall 13 and side wall 14. On the side wall 14 of the Floatbadwanne 12, a side wall box 24 is shown with suction 40.

The suction line 40 opens above the float bath 16 in the interior of the Floatbadgehäuses 11. Outwardly, the suction line 40 opens into the Injektorpumpe 60, which consists of an outer tube 62 and an inner tube 64, at the upper end of a nozzle 66 is arranged. The inner tube 64 is connected to a compressed air generator 80 connected, which in turn is electrically terminated to a control device 82. Via the electrical connection line 72, the control device 82 is connected to the arranged on the inside of the side wall 20 temperature sensor 70. The compressed air generated in the compressed air generator 80 flows into the inner tube 64 and then from the nozzle 66 into the interior of the outer tube 62 a. It is therefore in the outer tube 62 in the mouth region of the suction line 40 generates a negative pressure, due to which the Formiergasatmosphäre is sucked from the interior of the Floatbadgehäuses 11. Compressed air and gas atmosphere from the interior of Floatbadgehäuses 11 are discharged upwards together through the discharge pipe 68.

FIG. 14 shows a plan view of a section of the float bath according to FIG. 1 in a further embodiment. Here, the adjacent cover elements 30 are arranged at a distance A ₆ to each other.

FIG. 15 shows a section through a cover element 30. The cover element 30 is arranged at a distance A ₂ from the float bath mirror 17. In addition, the cover 30 is mounted at a distance A ₅ to the sidewall box 24. The suction opening 41, which opens into the intermediate space between the cover 30 and the Floatbadspiegel 17, has the distance A ₇ to the glass band edge

LIST OF REFERENCE NUMBERS

Bay number

Floatbadvorrichtung

Floatbadgehäuse

Floatbadwanne

bottom wall

Side wall

float bath

Floatbadspiegel

Floatbaddach

ceiling wall

Side wall

Formiergaszuführung

Side wall boxes

Toproller

glass tape

Glass ribbon edge

cover

holder

cover

Edge of the cover plate 36.36 'gap

38 support

39 floats

40 suction line

41 suction opening

42 slot nozzle

50 suction device

53 outer suction tube

60 injector pump

62 outer tube

64 inner tube

66 nozzle

68 drain pipe

69 compressed air line

70 temperature sensor

72 electrical connection line

80 compressed air generator

82 control device

84 control valve

123 shaped stone

124 shaped stone

125 dividing line

Ai distance edge glass ribbon / edge cover plate

A ₂ distance Floatbadspiegel / bottom

A ₅ Distance covering element / side wall Ae distance cover element / cover element A ₇ distance edge glass band / suction opening

Claims

claims

1. Float bath device (10)

with a float bath tub (12) and with a float bath roof (18) and side walls (14, 20), wherein in the Floatbadwanne (12) is a float bath (16) made of liquid metal, for producing a floating on the float bath (16) Glass ribbon (28),

with a cover of the float bath (16) with at least one cover element (30, 32),

characterized,

in that the cover element (30, 32) is arranged at least in a partial region of the free float bath surface which is located between the edge (29) of the glass ribbon (28) and the side wall (14) with a gap (36) spaced from the float bath mirror (17) is and

in that a device for extracting an atmosphere inside the device (10) is provided with at least one suction line (40), wherein the suction opening (41) of the suction line (40) opens into the intermediate space (36).

2. Apparatus according to claim 1, characterized in that the suction opening (41) has a horizontal distance A ₇ to the glass band edge (29) in the direction of the nearest side wall (14) of at least 100 mm.

3. A device according to claim 3, characterized in that the suction line (40) in the side wall (14) and / or in the cover member (30, 32) is arranged.

4. Device according to one of claims 1 to 3, characterized in that the cover (30, 32) consists of Quarzal.

5. Device according to one of claims 1 to 4, characterized in that the cover (30, 32) has at least one support (38) which rests on the bottom wall.

6. Apparatus according to claim 5, characterized in that the support (38) consists of mullite.

7. Device according to one of claims 1 to 4, characterized in that the cover (30, 32) at least one floating body (39), with which the cover (30, 32) spaced on the Floatbad (16) floats.

8. Apparatus according to claim 7, characterized in that the floating body (39) consists of mullite.

9. Device according to one of claims 1 to 8, characterized in that the cover element (30, 32) by means of a holding device (31) is fixed.

10. Device according to one of claims 1 to 9, characterized in that the cover member (30, 32) extends to the side wall (14).

11. The device according to claim 10, characterized in that the Abdeckθlement (30, 32) sealingly against the side wall (14).

12. Device according to one of claims 1 to 4, characterized in that the cover (30, 32) between the side wall boxes (24) and the side wall (14) of the float bath tub (12) is held.

13. Device according to one of claims 1 to 4, characterized in that the cover (30, 32) on a ceiling wall (19) of the Floatbadgehäuses (11) is suspended.

14. The device according to one of claims 1 to 13, characterized in that the distance Ai between the edge (29) of the glass ribbon (28) and the edge (34) of the cover (30, 32) 0 <Ai <500 mm.

15. Device according to one of claims 1 to 14, characterized in that the cover member is a cover plate (30).

16. Device according to one of claims 1 to 15, characterized in that the distance A ₂ between the underside of the cover plate (30) and the Floatbadspiegel (17) is 25 to 100 mm.

17. Device according to one of claims 1 to 16, characterized in that the distance A ₅ between the side wall (14) and the cover (30,32) is 0 <A ₅ <500 mm.

18. Device according to one of claims 1 to 17, characterized in that the cover is a cover (32).

19. The device according to one of claims 1 to 18, characterized in that the distance between at least two along a side wall (14) arranged adjacent covering elements (30, 32) 0 <A ₆ <500 mm.

20. Device according to one of claims 1 to 19, characterized in that at least two along a side wall (14) arranged adjacent cover elements (30, 32) directly adjacent to each other.

21. Device according to one of claims 1 to 20, characterized in that the cover elements (30, 32) in a Floatbadabschnitt (1 to 8) cover at least 50% of the free Fadtbadoberfläche.

22. Device according to one of claims 1 to 21, characterized in that the cover elements (30, 32) in the hotter area of the float bath (16) at least in a Floatbadabschnitt (1 to 8) are arranged.

23. Device according to one of claims 1 to 22, characterized in that the cover elements (30, 32) in the hotter area of the float bath (16) at least over a length of 50% of the length of the float bath (16) are arranged.

24. Device according to one of claims 1 to 23, characterized in that the at least one suction line (40) in a side wall boxes (24) is arranged, which in the side wall (14) can be inserted.

25. Device according to one of claims 1 to 24, characterized in that the suction opening (41) extending in a horizontal direction slot opening (41).

26. Device according to one of claims 1 to 25, characterized in that in at least one Floatbadabschnitt (1 to 8) in the two opposite side walls (14, 20) in each case at least one slot opening (41) is arranged.

27. The device according to claim 26, characterized in that the cover elements (30, 32) and / or the slot openings (41) at least in the first two Floatbadabschnitten (1, 2) are arranged.

28. Device according to one of claims 25 to 27, characterized in that at least two slot openings (41) are arranged side by side in the horizontal direction.

29. Device according to one of claims 25 to 28, characterized in that the slot openings (41) a total of at least 50% of the length of a Floatbadabschnittes (1-8) extend.

30. Device according to one of claims 25 to 29, characterized in that the slot openings (41) extend over a total of at least 30% of the length of the float bath (16).

31. Device according to one of claims 25 to 30, characterized in that the horizontal length of the slot opening (41) is 30 cm to 150 cm.

32. Device according to one of claims 25 to 31, characterized in that the cross-sectional area of the slot opening (41) is 20 to 40 cm ² .

33. Device according to one of claims 25 to 32, characterized in that the lower edge of the slot opening (34) between 4 cm and 8 cm above the mirror (17) of the float bath (16) is arranged.

34. Device according to one of claims 1 to 33, characterized in that the suction line (40) in the side wall (20) has a gradient from the inside to the outside.

35. Device according to one of claims 25 to 34, characterized in that the suction line (40) has a slot opening (34) having slot nozzle (42).

36. Apparatus according to claim 35, characterized in that the slot nozzle (42) between the tapered side walls of the slot nozzle in plan view an angle a of 14 ° to 40 ° and between the side walls of the slot nozzle in side view an angle ß of 2 ° to 10th °.

37. Device according to one of claims 35 or 36, characterized in that the slot nozzle (42) in a side wall boxes (24) is arranged.

38. Apparatus according to claim 37, characterized in that the side wall box (24) has two molded blocks (123, 124) which delimit at least the slot nozzle (42).

39. Device according to one of claims 1 to 38, characterized in that the suction device (50) has at least one injector pump (60) which generates a negative pressure at the outlet of the suction line (40).

40. Apparatus according to claim 39, characterized in that the Injektorpumpe (60) is connected to at least one compressed air generator (80).

41. Apparatus according to claim 40, characterized in that the compressed air generator (80) has at least one control device (82) for controlling the pressure of the compressed air or to at least one such control device (82) is connected.

42. Device according to one of claims 39 to 41, characterized in that between the injector pump (60) and compressed air generator (80) at least one control device (82) is arranged for controlling the pressure of the compressed air.

43. Apparatus according to claim 42, characterized in that the control device (82) is a control valve (84).

44. Device according to one of claims 42 or 43, characterized in that the control device (82) to at least one temperature sensor (70) is connected, which is arranged in the interior of the Floatbadgehäuses (11).

45. Device according to one of claims 1 to 44, characterized in that in the region of the suction opening (41) of the suction tubes (40) covering hoods (32) are arranged.

46. Method for producing flat glass, in particular TFT glass, in which liquid glass is continuously poured onto a liquid metal-containing float bath in a float bath apparatus having sidewalls in a forming gas atmosphere and formed into a glass ribbon there,

characterized,

that at least part of the free float bath surface, which is located between the edge of the glass ribbon and the adjacent side wall, is covered by a cover to form a gap, and

that a flow of the atmosphere is generated in the intermediate space.

47. The method according to claim 46, characterized in that the flow is directed away from the glass ribbon.

48. The method according to claim 46 or 47, characterized in that the atmosphere is sucked out of the intermediate space to the outside.

49. The method according to any one of claims 46 to 48, characterized in that the mean velocity of the flow at the leading edge in the space between the cover and the three Floatbadoberfläche is set to 0.1 m / s to 10 m / s.

50. The method according to any one of claims 46 to 49, characterized in that the atmosphere is sucked slit-shaped in the horizontal direction.

51. The method according to any one of claims 46 to 50, characterized in that the atmosphere is extracted at several points along the side wall.

52. The method according to any one of claims 46 to 51, characterized in that the atmosphere in at least two Floatbadabschnitten (Bays) of the Floatbadgehäuses is sucked like a slit.

53. The method according to any one of claims 46 to 52, characterized in that the atmosphere is sucked off over at least 50% of the Floatbadlänge.

54. The method according to any one of claims 46 to 53, characterized in that the extracted gas amount per unit time in each Fadtbadabschnitt is adjusted depending on the temperature of the Floatbadabschnittes.