Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C14/00—Glass compositions containing a non-glass component, e.g. compositions containing fibres, filaments, whiskers, platelets, or the like, dispersed in a glass matrix
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B23/00—Re-forming shaped glass
  • C03B23/02—Re-forming glass sheets
  • C03B23/023—Re-forming glass sheets by bending
  • C03B23/035—Re-forming glass sheets by bending using a gas cushion or by changing gas pressure, e.g. by applying vacuum or blowing for supporting the glass while bending
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B29/00—Reheating glass products for softening or fusing their surfaces; Fire-polishing; Fusing of margins
  • C03B29/04—Reheating glass products for softening or fusing their surfaces; Fire-polishing; Fusing of margins in a continuous way
  • C03B29/06—Reheating glass products for softening or fusing their surfaces; Fire-polishing; Fusing of margins in a continuous way with horizontal displacement of the products
  • C03B29/08—Glass sheets
  • C03B29/12—Glass sheets being in a horizontal position on a fluid support, e.g. a gas or molten metal
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B32/00—Thermal after-treatment of glass products not provided for in groups C03B19/00, C03B25/00 - C03B31/00 or C03B37/00, e.g. crystallisation, eliminating gas inclusions or other impurities; Hot-pressing vitrified, non-porous, shaped glass products
  • C03B32/02—Thermal crystallisation, e.g. for crystallising glass bodies into glass-ceramic articles
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B35/00—Transporting of glass products during their manufacture, e.g. hot glass lenses, prisms
  • C03B35/14—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands
  • C03B35/22—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands on a fluid support bed, e.g. on molten metal
  • C03B35/24—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands on a fluid support bed, e.g. on molten metal on a gas support bed
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B35/00—Transporting of glass products during their manufacture, e.g. hot glass lenses, prisms
  • C03B35/14—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands
  • C03B35/22—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands on a fluid support bed, e.g. on molten metal
  • C03B35/24—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands on a fluid support bed, e.g. on molten metal on a gas support bed
  • C03B35/243—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands on a fluid support bed, e.g. on molten metal on a gas support bed having a non-planar surface, e.g. curved, for bent sheets
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
  • C03C10/0009—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing silica as main constituent
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
  • C03C10/0018—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and monovalent metal oxide as main constituents
  • C03C10/0027—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and monovalent metal oxide as main constituents containing SiO2, Al2O3, Li2O as main constituents
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
  • C03C10/0036—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and a divalent metal oxide as main constituents
  • C03C10/0045—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and a divalent metal oxide as main constituents containing SiO2, Al2O3 and MgO as main constituents
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
  • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/097—Glass compositions containing silica with 40% to 90% silica, by weight containing phosphorus, niobium or tantalum
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24479—Structurally defined web or sheet [e.g., overall dimension, etc.] including variation in thickness
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24628—Nonplanar uniform thickness material
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31—Surface property or characteristic of web, sheet or block
  • Y10T428/315—Surface modified glass [e.g., tempered, strengthened, etc.]

Definitions

• the invention generally relates to the production of glass or glass ceramics and more particularly to the production of glass or glass ceramics by storage on a gas bed during ceramization, as well as glass or glass ceramic articles produced according to the method.
• Glass ceramic plates are widely used, among other things, as cooking surfaces for modern cooktops, as oven windows or fire-resistant glazing. In glass ceramics, the strength and the plays
• the knobs in particular effect protection of the underside of the glass ceramic plate against strength-reducing injuries which are added to the glass ceramic, in particular during the ceramization process.
• glass ceramic hobs were also produced for cooktops, which had smooth surfaces on both sides.
• a plate thickness of 4 mm with a test format of 10 x 10 cm an average strength value of 36 cm drop height was achieved.
• the currently used glass ceramic plates are mainly injured by the ceramizing process on, visually disturbing and reduce the strength noticeably.
• the strength properties are determined by the quality of the surface. In a known
• Keramleiterfrac is placed on a ceramic base plate to be ceramized green glass plate e separating agent can be used between green glass plate and base plate.
• the glass ceramics which have been ceramized on a base generally injuries on the side, which faces the base plate.
• Another method uses hanging ceramization.
• the green glass plate is stored hanging at one end.
• the glass ceramic is noncontact-mounted, so that no injuries to a substrate can occur, but it is difficult to achieve a flatness of the glass ceramic plates which satisfies the requirements.
• GB 1383202 proposes to use combustion gas as levitation gas for the gas cushion.
• combustion gas as levitation gas for the gas cushion.
• particles are contained which preferably settle on the glass ceramic and thereby lead to a reduction in strength.
• easily scaling metals and combustion products in the furnace chamber cause the glass plate is contaminated on its surface.
• DE 10045479 a method for contactless storage and transport of flat glass is described in which the storage is also carried out on a gas cushion.
• the pad has for this purpose a segmental structure in which the gas is supplied through openings in the segments and can escape through the spaces between the segments again.
• US 5,078,775 describes a gas cushion pad with a membrane whose upper side has slit-shaped gas supply and gas outlet openings.
• the Gas outlet ports communicate with gas outlet chambers in the membrane.
• the gas supply openings are connected via collecting ducts to the underside of the membrane. At the bottom of the membrane compressed gas is supplied, which flows through the collecting ducts and the gas supply openings to the top and there generates a gas cushion, on which then a glass plate can be stored.
• the gas comes only comparatively short with the walls of the sump in contact, so that no complete heat exchange take place and the gas can therefore flow with a temperature in the gas cushion, which may differ from the temperature of the membrane and in particular the temperature of the overlying glass.
• the invention has for its object to provide glass or glass-ceramic materials, which in particular have a smooth fire-polished and / or knobbed surface, wherein the materials have a relation to known glass-ceramics significantly increased strength at the same time less visually disturbing damage to the surface.
• the method according to the invention comprises the production of a starting glass body, storing the starting glass body on a gas cushion between a levitation pad and the starting glass body; and at least partially ceramizing the starting glass body on the levitation pad.
• the levitation pad has at least one contiguous surface area with at least one gas supply area to which levitation gas of the gas cushion is fed out of the levitation pad and at least one gas discharge area on which gas of the
• Gas cushion is at least partially discharged into the Levitationsunterlage inside.
• the gas supplied to the gas cushion is preferably also passed through one or more chambers arranged in the levitation support before it leaves the latter exit.
• the gas supplied to the gas cushion is preferably also passed through one or more chambers arranged in the levitation support before it leaves the latter exit.
• the at least one gas supply chamber and at least one gas discharge chamber closed channels which extend in the direction along the support surface in the interior of the membrane.
• a closed channel is accordingly a channel to understand, which is bounded by a wall in the manner of a tube.
• a closed channel does not mean a completely closed cavity, since at least one inlet opening for the gas supply chamber and an outlet opening for the gas discharge chamber are provided for the supply and removal from the chambers or the channels of this embodiment.
• the gas supply chamber, a gas inlet opening and the gas discharge chamber having a gas outlet which are arranged so that the Gasflußides within the gas supply chamber and Gasabbowrithmmer transverse to the normal of the support surface, in particular also along the support surface.
• the levitation gas flows in the gas supply chamber and the gas discharge chamber in the membrane transversely to the normal of the support surface, in particular in the direction along the support surface, then a long flow path of the gas in the chambers and, concomitantly, an effective heat transfer can also occur in a thin membrane as levitation support the chamber walls are reached.
• the levitation gas is fed into the gas supply chambers through at least one gas-permeable connection to the underside of the membrane or the levitation pad. Then one under the gas discharge and
• Gas supply chambers arranged pre-chamber, preferably provided with a ceramic wall, which is connected for the supply of gas into the gas supply chamber via at least one gas-permeable connection with the Gaszufuhwait.
• the pre-chamber itself is part of the membrane or levitation pad, or a one-piece membrane with at least one prechamber, gas removal and gas supply chambers is used.
• the gas supply chamber is at least partially closed at the bottom, wherein the levitation gas is introduced into the gas supply chamber through a downwardly directed gas permeable compound in the membrane in the gas supply chamber.
• the gas is also supplied from below, for example, in the gas cushion pad known from US Pat. No. 5,078,775, this membrane does not have any closed or downwardly at least partially closed chambers or channels for the gas supply. Rather, the channels are completely open downwards.
• the gas supply chamber ' with a gas-permeable
• connection in particular in the form of channels with a smaller cross-section than the gas supply chamber ensures that the gas dwells longer in the gas supply chamber before it exits via the further gas-permeable compound from the support surface.
• an improved heat exchange with the membrane and thus a particularly good temperature homogeneity in the gas cushion is achieved in this embodiment of the invention.
• the temperature of the levitation pad with a temperature gradient in the direction along the support surface of less than 10 0 C preferably be kept below 5 ° C.
• Levitation cushion passes through the gas discharge chambers in the antechamber and is discharged there.
• the pressure drop in the chambers is at most 0.5 mbar. If the levitation gas experiences a pressure drop of at most 0.5 mbar as it flows through the gas supply chamber and / or the gas discharge chambers, a particularly homogeneous pressure distribution can also be achieved in the gas cushion. '
• the production of the starting glass body can be carried out by a conventional melting and shaping process, before the starting glass body is then ceramized according to the invention, for example in a levitation furnace.
• the at least partial ceramization may in particular also comprise the nucleating.
• the storage of the glass or glass ceramic on a levitation cushion is important on the one hand when the glass or the glass ceramic becomes very soft and / or when the glass or glass ceramic plate expands or contracts greatly.
• the glass plate moves relative to the base plate, with the result that scratches on the more sensitive glass plate arise.
• Auserdem it is advantageous if the glass has no contact with the substrate at the viscosities mentioned. If it comes to the contact of the starting glass body with a base, it may cause the glass to adhere to the base.
• Method can also be a particularly homogeneous Temeraturver whatsoever both along the
• the pad is otherwise a heat reservoir, which only delays the temperature changes occurring during the ceramization and can inhomogeneous anpas sen.
• the temperature homogeneity for later quality and strength 'of the rendered ceramic glass is very important this so that here the levitating protective storage is of particular advantage.
• the at least partial ceramization need not include complete ceramization.
• the material of the starting glass can only be partly ceramized in order to obtain desired physical properties of the finished article.
• the glass plate may change in its geometric dimensions. For example, this effect often occurs due to the phase transformation during ceramization. This can lead to both shrinkage and expansion of the glass plate. These changes often occur both in the area of nucleation and in different phases of crystal growth. In the conventional ceramizing process occurs in these phases, a strong relative movement of the glass plate relative to the base plate, which can lead to scratches in the product. Accordingly, an advantageous development of the method according to the invention provides for levitating the glass plate or the starting glass body on the gas cushion as it shrinks or expands.
• the levitation gas is at least partially circulated. In this way, a cycle of the levitation gas is achieved.
• the glass or the glass ceramic is stored in a hot state, for example for the ceramization on the gas cushion.
• the circulated gas is thus already heated in the gas supply chambers, so that the Levitationsunterlage cooled only slightly by the supplied Levitationsgas. This saves energy, on the other hand, the homogeneity of the Temperature distribution hardly or not at all disturbed.
• it is advantageous for the lowest possible temperature differences if the levitation gas of the environment of the starting glass body, for example, the furnace chamber of a ceramic furnace, in which the levitation pad is arranged, is removed.
• a glass or glass ceramic article produced according to the invention is also distinguished by a more level surface.
• the material may flow in the direction of gravity, ie along the surface of the starting glass body, resulting in a clearly inhomogeneous thickness of the finished ceramized article.
• the restoring forces in warpage in a accordance with the invention on a flat surface lying ceramized starting glass bodies are significantly higher than in a hanging 'mounted initial glass body.
• the surface of the starting glass body adjusts to the surface of the base, so that undesired warping is compensated. However, this effect does not occur in a free-hanging body, so that warping can be maintained.
• 'According to one embodiment of the invention is a full-surface ceramisation of the starting glass body carried out so that a whole surface ceramized glass or glass-ceramic article is obtained. This is possible through the levitating storage, since no or only a minimal support or guidance is necessary for holding or guiding the starting glass body. In contrast, for example, in the hanging ceramization in No ceramization can be carried out in the area of the holder because the material is too soft or there are severe injuries.
• the production of the starting or pre-glass body may advantageously also comprise the separation of portions of an initial glass ribbon.
• the separated sections can then be subsequently ceramified separately. In this way, a subsequent cutting of the ceramized material, by which strength-reducing injuries may occur in the glass ceramic avoided.
• a glass or glass-ceramic article which can be produced by the method according to the invention an article is understood to mean a material which may comprise glass and / or in particular glass-ceramic and / or partially-ceramicized glass.
• the glass-ceramic articles which can be produced according to the invention have an increased strength without chemical pretension, so that according to one embodiment of the invention a chemical pretension is dispensed with, or in which a glass-ceramic article according to the invention is not chemically prestressed.
• the format defined test plate in sample (100 mm x 100 mm squares) cut or produced in this defined format and 'tested by the falling ball test.
• the ball drop test is performed such that a
• a procedure with a respectively defined increased height of fall is carried out until fracture of the sample occurs.
• the drop height at which breakage occurs is recorded as a measure of the strength of this sample.
• the strength of the entire plate to be tested or a batch of manufactured articles arises . the mean of the individual strengths of the samples cut from it.
• an article which can be produced according to the invention has, as a result of the production process, in particular a significantly increased breaking strength compared to known glass-ceramic materials, which manifests itself in a correspondingly increased mean drop height in the test described above.
• This increased strength is already evident not additionally tempered glass-ceramic articles, in particular without chemical prestress.
• the glass or glass-ceramic articles according to the invention are characterized by an average drop fall height, which amounts to at least 15 cm per millimeter thickness of the glass or glass-ceramic article with a format of 10 ⁇ 10 cm. Also 18 cm average breakage height per millimeter thickness of the glass or glass-ceramic article is easily reached or exceeded.
• the increased strength of the glass-ceramic articles which can be produced according to the invention is based on first findings, inter alia, on a glassy film forming on the surface of the article.
• a glass or glass-ceramic article producible in accordance with the invention can in particular comprise a material which is resistant to breakage in the form of a 3 mm thick, double-sided plate of the format 10 ⁇ 10 cm with a drop height of more than 45 cm. In general, even diarrhea heights of at least 60 cm are achieved.
• a glass or glass ceramic article according to the invention so that its material in the form of a 3 mm thick, double-sided flat plate with a drop height of at least 80 centimeters on average is resistant to breakage.
• this has a material which in the form of a 5 mm thick, both sides flat plate with a drop height of at least 140 centimeters on average is resistant to breakage. This exceeds the strength of known glass-ceramic articles without chemical Preload measured by the fall height by more than a factor of 2.
• the values given above refer to material of a certain shape and thickness. This is generally not to be understood that the glass or glass ceramic article itself has a format of 10x10 centimeters, but that a cut from the glass or glass-ceramic article specimen having the respective thicknesses specified has the average breakage heights.
• a glass or glass ceramic article according to the invention may accordingly also have a variety of other shapes and also other thicknesses.
• the information on the strength serve in particular the
• Characterization of the material of the article but not its shape and thickness. If an article according to the invention has a non-plate-like shape or a different thickness, in order to determine its mechanical properties with a drop test, one or more plates of defined thickness for carrying out the drop tests can be produced and ceramified according to the invention from the same starting glass. For example, strength values for various plate thicknesses can be obtained in a simple manner by interpolation of the values given above.
• a pre-glass body is produced in the form of a flat glass plate on both sides, for example with a thickness of 3 or 5 millimeters, and then at least partially ceramifying levitating, so that a corresponding, both sides smooth glass or glass ceramic article is obtained.
• Such articles are suitable, for example, as glass ceramic hotplates, chimney view panes, as fire protection or fire protection panes.
• Ceramizing process is created a fire polished surface of the article.
• the fire-polished surface has substantially less or no surface damage to a subsequently mechanically polished surface, which also results in increased strength of the article according to the invention compared to such subsequently polished plates.
• glass or glass ceramic articles which can be produced according to the invention can also be used as safety glazing.
• Such a safety glazing can be in particular an armored glass, even a bulletproof bulletproof glass.
• pimpled plates, as they have been produced many times to achieve a sufficiently high resistance to breakage can be prepared by the method according to the invention and ceramifying levitierend.
• a corresponding pre- or starting glass body is produced in the form of a glass sheet, in particular knurled on one side.
• a slightly higher gas flow at a constant fly height if there are knobs on the side facing the membrane.
• the dimpled structure Can, for example, in a melting and shaping process over a dimpled roll during hot forming in one side of a Vorglasbandes, as in particular the glass ribbon underside are embossed.
• the nub structure may have a regular pattern of domes that are round or oval, or other shapes.
• Such a glass or glass ceramic article which can be produced according to the invention and which corresponds in its external form to a conventionally produced knobbed plate also has an at least 20% higher resistance to breakage compared with such a conventionally produced dimpled plate.
• a glass or glass ceramic article according to the invention comprises a material of at least one of the systems SiO 2 -Al 2 O 3 -Li 2 O, SiO 2 -Al 2 O 3 -MgO, SiO 2 -Al 2 O 3 -BaO.
• the material may also have at least one of the oxides TiO 2 , ZrO 2 , P 2 O 5 in a conventional concentration in order to influence the mechanical and optical properties and the viscosity of the starting glass.
• the production of a starting glass body may advantageously comprise the refining of the starting glass.
• a substantially bubble-free starting glass is obtained, which significantly contributes to the strength of the article according to the invention.
• the starting glass and refining agents such as As 2 O 3 , Sb 2 O 3 , CeO 2 or SnO 2 may be added, which are accordingly also found in the material of the finished article.
• At least one color oxide may be added to the material of the starting glass.
• the material of the finished article or glass has the following components: Li 2 O 2.5 - 5.5%
• its material has one of the following compositions:
• a dark coloration as is often desired for hobs, can be advantageously achieved by a composition of the material of the article or the starting glass, the composition of which comprises 0.02 to 0.6 weight percent V 2 O 5 . Accordingly, for a transparent glass-ceramic, it is advantageously possible to select a composition which is substantially free of V 2 Os.
• composition of the starting glass or the ceramically finished material may also advantageously comprise at least one compound selected from a group comprising Cr, Mn, Fe, Co, Cu, Ni, Se, and Cl compounds. Such compounds are particularly useful for promoting coloration and adjustment of certain color locations.
• the ceramizing of the starting glass body comprises the particularly clean electrical heating of the starting glass body, preferably in a levitation furnace.
• the levitation gas can also be cleaned, for example by means of a cleaning filter, and kept as clean as possible in order to prevent the precipitation of foreign substances and to avoid a consequent reduction in the strength.
• the levitation pad may comprise at least one membrane with a contiguous surface area and at least one gas supply and at least one gas discharge chamber. These chambers are preferably each arranged below the gas supply and gas discharge area. In this way, gas is supplied via a gas supply chamber to the gas supply region and forms a gas cushion between the contiguous surface region and the starting glass body. On the other hand, excess gas may pass through the gas discharge area into a gas discharge chamber located thereunder.
• the gas supply and gas removal can by adjusting a suitable pressure gradient between the gas discharge chamber and the gas discharge area, or between the
• Gas supply chamber and the gas supply area is set.
• a pressure gradient between gas supply and gas discharge chambers can be set in a simple manner.
• a suitably shaped membrane with chambers can be produced in particular by extrusion.
• the gas is supplied and discharged via supply and discharge channels of a perforated surface of the levitation pad.
• the surface of the levitation pad can advantageously also comprise a porous material, through which gas is supplied or removed for the gas cushion.
• the levitation gas through the membrane in transports the gas cushion that forms between the membrane and the glass plate.
• the extruded membrane is perforated, so that forms a homogeneous as possible pressure profile.
• This homogeneous pressure profile is advantageous in order to achieve a high flatness of the glass or glass ceramic articles produced according to the invention.
• the desired temperature profile for the ceramization with the lowest possible temperature deviation between the top and bottom of the glass can be advantageously produced by taking place in the gas supply chambers of the extruded membrane temperature homogenization of the levitation gas.
• the starting glass body can be stored partially or completely on the gas film during the ceramization process.
• a specific temporal temperature profile is used for the ceramization of the starting glass body during the ceramization process.
• the starting glass body is first heated to a temperature Tl.
• This temperature is for example in a range of 650 to 800 0 C.
• the body can be kept up to 4 hours depending on the furnace unit and shape of the starting glass body.
• the body is then further heated to a temperature T2 in a range of 850 to 950 0 C.
• T2 in a range of 850 to 950 0 C.
• the body can then be held for up to about 50 minutes.
• the body is again tempered to room temperature.
• the levitation pad may have a curved surface.
• the starting glass body can then be arched in a heated state by gravity lowering above the levitation pad. It is advantageous when levitation gas is supplied during the buckling process, so that the buckling can be done without contact.
• the article has a warping along one direction, or a uniaxial warping.
• Such an article may for example have a uniform curvature, so that it has the shape of a cylinder jacket segment. Similarly, the radius of curvature along the surface, but also change.
• the production of such a shaped article can, as described above, take place by gravity lowering over a uniaxially arched membrane in this case.
• Fig. 1 is a cross-sectional view through a
• Fig. 2 is a plan view of an embodiment of a
• FIG. 3 shows a development of the embodiment shown in FIGS. 1 and 2, Fig. 4A and 4B based on schematic views of a
• FIGS. 4C and 4D are schematic views of another embodiment of an apparatus for carrying out the method according to the invention . Method steps for producing a curved article, and
• Fig. 5 shows the dependence of the average drop fall height of the thickness of glass-ceramic articles.
• Fig. 1 is a cross-sectional view of a Levitationsunterlage in the form of a designated as a whole by 1 membrane.
• the membrane is preferably made by extruding a suitable material, such as a temperature-resistant ceramic.
• the membrane 1 has a number of chambers 51, 52, 53, 71, 72, 73, which are arranged below the placed on one side of the membrane ⁇ continuous surface region 3 in the membrane.
• the chambers 51, 52, 53 as gas supply chambers and the chambers 71, 72, 73 as gas discharge chambers for the levitation gas of the gas cushion, which is between a to be ceramized
• Fig. 1 shows for clarity one above the surface area 3 in levitation on a gas cushion or gas film 13 located starting glass body 11 in the form of a double-sided flat plate.
• the surface area 3 is perforated and has as
• the supply and removal of the levitation gas takes place via the gas supply channels 91, 92, 93 and gas discharge channels 101, 102, 103 which are in communication with the surface region 3 and the chambers 51, 52, 53 and 71, 72, 73.
• the gas flow direction is shown in FIG. 1 represented by arrows.
• Between the chambers 51, 52, 53 and 71, 72, 73 to a pressure difference is generated, wherein in the gas supply chambers 51, 52, 53, a higher pressure than in the gas discharge chambers 71, 72, 73 is set.
• the levitation gas can be cleaned before entering the gas supply chambers, so that this example is substantially free of airborne particles that can be deposited on the surface in the softened state of the starting glass body.
• the levitation gas can advantageously be circulated with a corresponding device.
• the gas to the vicinity of the initial glass body 11, such as a • furnace chamber in which the membrane is arranged is removed and the membrane 1 is supplied again, so .to a good temperature balance between the gas cushions and the surroundings of the Levi tierend stored starting glass body to reach 11 ,
• the starting glass body 11 is stored on the gas cushion 13 above the membrane 1 in particular when it shrinks or expands and / or has low viscosities at which the starting glass body could otherwise adhere to the base. Shrink and
• the levitating storage is generally favorable for the quality of the article according to the invention, as due to the storage on the
• Gas cushion a particularly homogeneous temperature distribution along the surface and minimum temperature differences between the top and bottom of the glass body can be achieved.
• FIG. 2 shows a plan view of the contiguous surface of an embodiment of a levitation pad 1 in the form of a membrane.
• Levitation pad 1 has gas supply areas 151, 152, 153, to which levitation gas for the gas cushion is supplied, and gas discharge areas 171, 172, 173, at which gas of the gas bag is at least partially discharged.
• the areas 151, 152, 153, 171, 172, 173 are marked in FIG. 2 by dashed lines.
• the gas is supplied via gas supply channels 95 arranged in the gas supply regions 151, 152, 153 and the gas discharge via gas discharge channels 105 arranged in the gas discharge regions For the sake of clarity, only some of the channels 95 and 105 are designated in FIG. 2. As shown in Fig. 1, the channels 95 and 105 are connected to below the surface region 3 arranged chambers.
• the chambers 51-53, 71-73 are formed as closed channels, which extend in the direction along the support surface in the interior of the membrane 3 below the gas supply and gas discharge areas.
• the channels are also opposite the bottom surface of the membrane 1, which faces the support surface for the starting glass 11, at least partially closed so that a thermal barrier to the bottom of the membrane 1 is present.
• Fig. 3 a development of the invention is shown, in which the gas is introduced into the gas supply chambers via a arranged under the membrane 1 antechamber 6. Also in this embodiment of the invention, the gas supply chambers 51, 52, 53 are limited towards the bottom at least partially by a wall of the membrane 1.
• Gas supply chambers 51, 52, 53 each have downwardly directed gas-permeable compounds in the form of channels 96 to the bottom or bottom surface 4 for the supply of gas from the prechamber 6.
• the pre-chamber 6 is formed by a connected to the bottom surface 4 pre-chamber housing 5.
• the pre-chamber housing 5 is preferably, as well as the membrane 1 made of ceramic material to avoid contamination of the levitation gas.
• the glass or the glass ceramic 11 through the levitation cushion at a height of at least 750 microns, preferably held at most 2 millimeters above the support surface.
• FIGS. 4A and 4B, as well as 4C and 4D, show the method steps for producing a curved glass or glass-ceramic article on the basis of schematic views of two embodiments of a device for carrying out the method according to the invention.
• a plate-shaped starting glass body 11 is shaped in a conventional manner by hot forming.
• This is then placed in a levitation furnace 19 with a levitation pad placed therein in the form of a membrane 1, so that the starting glass body 11, as shown in Fig. 4A, is located above the surface region 3.
• the membrane 1 is constructed similarly; as shown in Figs. 1 to 3.
• the embodiment of the membrane 1 shown in FIGS. 4A to 4D has a curved surface region 3. This is exemplified in Figs. 4A and 4B as convex
• FIGS. 4C and 4D show an embodiment with a concavely curved surface area.
• a gas cushion between the pad and the starting glass body 11 is generated by gas supply via the Gaszu Food Schemee the surface region 3. This can be advantageous also held or guided laterally to a drifting away of the body to avoid.
• Such a holder or guide requires only minimal holding forces during levitating storage.
• the Berühungsucc can be kept very small with the holding or guiding device, so that a full-surface ceramization of the starting glass body is achieved.
• the starting glass body is heated by means of an arranged in the levitation furnace electric heater 21 so far that it softens.
• the starting glass body As a result of gravity acting on the starting glass body, it also bulges, with the regions of the starting glass body further away from the levitation pad 1 being lowered until a substantially homogeneous pressure distribution has been established through the gas cushion. This state is shown in FIG. 4B or FIG. 4D.
• the ceramizing on the pad 1 may be accompanied by the buckling process or be carried out subsequently.
• the glass In particular, during the nucleation process, the glass generally becomes very soft and can easily be domed during this phase by gravitational sinking.
• the membrane has a uniaxial, or along a direction curved surface, so that correspondingly uniaxially curved glass-ceramic articles are obtained.
• the achieved strength values at a breaking strength of more than 140 centimeters fall height on average.
• the glass ceramic material composition of this article corresponded to the glass type 2. This value for a 5mm thick glass plate exceeds the values of 60 cm drop height, which are otherwise usually measured on non-tempered glass ceramic plates of this thickness, by more than double.
• Glass-ceramic articles with a composition of the glass-ceramic corresponding to the glass type 1 were determined to have an average drop-fall height of over 80 cm.
• An average drop fall height of at least 55 centimeters or 18 cm per millimeter thickness of the glass-ceramic article is easily achieved with plate-shaped glass-ceramic material produced according to the invention or even, as the above example shows, far exceeded.
• the achievable at the average breaking strength fall height is about twice as high as the otherwise achievable with known glass-ceramic articles fall height of about 40 cm.
• the measured values are listed in more detail in the table below.
• FIG. 5 shows the dependence of the mean breakage drop height on the thickness of glass-ceramic articles on the basis of measured values. In each case values are conventionally produced
• the measured values of the conventionally produced plates and of FIG. 5 also show the linear correlation of the plate thickness with the mean breakage drop height.
• the tested conventionally produced glass-ceramic plates have, according to this linear relationship, an average break-up height of about 12.5 cm per millimeter plate thickness, corresponding to the line labeled "A".
• show the in Fig. 5 of the tested glass-ceramic plates according to the invention have a mean drop height of about 28.5 cm per millimeter plate thickness.
• the straight line labeled "B" is calculated according to this relationship.
• the plates for the drop test were ceramified in a test setup.
• the temperature homogeneity and the homogeneity of the pressure profile can be further improved, so that even average breakage heights of 30 cm per millimeter plate thickness or even above are possible.
• the significantly increased strength inventively produced plates is on the
• Embodiments have been demonstrated with the plate thicknesses of 3 mm and 5 mm. It is obvious to the person skilled in the art that plates produced according to the invention with a different plate thickness, for example between 3 mm and 5 mm, also have a corresponding increased strength.
• the increased strength of plates produced according to the invention with thicknesses between 3 mm and 5 mm can be interpolated using relevant literature. (See, e.g., J.L. Glathart, F.W., Preston: The Behavior of Glass Under Impact, in: Glass Technology, 1968). Accordingly, for slab thicknesses between 3 and 5 mm increased strength resulting from the

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• 2004
  • 2004-12-11 DE DE102004059728A patent/DE102004059728A1/de not_active Ceased
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