Methods for glass ribbon formation of glass melts delivered at low viscosities

Abstract

A method for producing a glass ribbon includes delivering glass melt to a first pair of rollers and rolling the glass melt between the first pair rollers in a first gap. The method further includes rolling the glass melt in a second gap between a second pair of rollers, wherein the second gap is offset from the first gap and located downstream from the first gap.

Description

METHODS FOR GLASS RIBBON FORMATION OF GLASS MELTS DELIVERED ATLOW VISCOSITIESPRIORITY CLAIM AND CROSS-REFERENCE

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 63 / 602747 filed on November 27, 2023, the content of which is relied upon and incorporated herein by reference in its entirety.FIELD

[0002] The disclosure relates to methods and apparatuses for glass ribbon formation of glass melts delivered at low viscosities.BACKGROUND

[0003] Glass production may include the production of continuous ribbons or webs of glass material. Such production methods may include the delivery of a glass melt that is formed into the glass ribbon for further processing. The requirements for the final glass product may include a desired thickness, width, quantity, or other requirements. The final glass product may, for example, be used in a consumer electronics application that may have particular requirements for use in the particular consumer electronics product. The requirements of the glass product may, in turn, constrain various glass properties because of a glass composition that may be needed to deliver the glass properties. Such glass property constraints may include liquidus viscosity and absorption coefficient, for example.

[0004] Existing production methods and apparatuses may be configured to produce glass ribbons for particular glass products having a range of glass property characteristics. The existing production methods and apparatuses may be limited from producing glass ribbons from glass melts that have glass properties outside of the particular range. Existing and / or traditional production methods and apparatuses that are used to produce glass ribbons outside of the range of glass ribbon properties for which they were designed may result in high rates or incidents of poor glass quality, may result in low yields of glass ribbon that are acceptable for the end use, and / or may simply not be able to produce the desired glass ribbon. There exists a need, therefore, for improved apparatuses and methods for producing glass ribbons that may have wider ranges of glass properties such as being able to produce acceptable glass ribbons from glass melts having low viscosities.SUMMARY

[0005] The present disclosure provides apparatuses and methods for producing glass ribbons having low viscosities.

[0006] In some embodiments of the present disclosure, a method for producing a glass ribbon is provided. The method may include delivering a glass melt to a first pair of rollers, rolling the glass melt between the first pair of rollers in a first gap, and rolling the glass melt in a second gap between a second pair of rollers, wherein the second gap is offset from the first gap and located downstream from the first gap.

[0007] In one aspect, the glass melt may have a viscosity of less than about 500 poise.

[0008] In another aspect, the second gap may be offset in a horizontal direction from the first gap.

[0009] In another aspect, the offset may cause the glass melt to be delivered to an outer surface of one roller of the first pair of rollers at a position spaced horizontally from the second gap.

[0010] In another aspect, an outer diameter of the first pair of rollers may be different than an outer diameter of the second pair of rollers.

[0011] In another aspect, the glass melt may be delivered to the first pair of rollers from a downcomer in a vertical orientation.

[0012] In another aspect, the glass melt may be delivered from the downcomer without a fishtail.

[0013] In another aspect, the method may include rolling the glass melt in a third gap between a third pair of rollers, wherein the third gap is offset from the second gap and located downstream from the first gap.

[0014] In another aspect, the first gap, the second gap, and the third gap may not be aligned along a common axis.

[0015] In another aspect, an outer diameter of the third pair of rollers may be different from an outer diameter of the first pair of rollers and the second pair of rollers.

[0016] In some embodiments of the present disclosure, an apparatus for producing glass ribbon from low viscosity glass melt is provided. The apparatus may include a downcomer configured for delivering a low viscosity glass melt for production of a glass ribbon and at least one pair of rollers positioned vertically below the downcomer. The at least one pair of rollers may include a first roller and a second roller spaced apart from each other to form a first gap, wherein the first roller and the second roller remove a predetermined amount of thermal energy from the low viscosity glass melt to produce the glass ribbon.

[0017] In one aspect, the low viscosity glass melt may have a viscosity of less than about 500 poise.

[0018] In another aspect, the at least one pair of rollers may include a second pair of rollers comprising a third roller and a fourth roller spaced apart from each other to form a second gap.

[0019] In another aspect, the second gap may be horizontally offset from the first gap.

[0020] In another aspect, an outer diameter of the first roller and the second roller may be different from an outer diameter of the third roller and the fourth roller.

[0021] In another aspect, an inner diameter of the first roller and the second roller may be different from an inner diameter of the third roller and the fourth roller.

[0022] In another aspect, the downcomer may deliver the low viscosity glass melt to the at least one pair of rollers in a vertical direction without a fishtail.

[0023] In another aspect, the glass melt may contact an outer surface of the first roller or the second roller at a position spaced horizontally from the first gap.

[0024] In another aspect, the apparatus may include one or more air pipettes or air blades positioned downstream of the downcomer configured to cool the glass melt.

[0025] In another aspect, the at least one pair of rollers may include a third pair of rollers including a fifth roller and a sixth roller spaced apart from each other to form a third gap. The third gap may be horizontally offset from the second gap.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not necessarily to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Like reference numerals denote like features throughout specification and drawings.

[0027] FIG. l is a side view of an example glass production system in accordance with some embodiments of the present disclosure.

[0028] FIG. 2 is a side view of an example apparatus that may be used to process a glass melt into a glass ribbon in accordance with some embodiments of the presented disclosure.

[0029] FIG. 3 is a side view of another example apparatus that may be used to process a low viscosity glass melt in accordance with some embodiments of the present disclosure.

[0030] FIG. 4 is a graph showing a capability of a glass production process using one or more apparatuses of the present disclosure.

[0031] FIG. 5 is a graph showing a projected process window for forming a glass ribbon from low viscosity glass melt in accordance with some embodiments of the present disclosure.

[0032] FIG. 6 is a graph showing another process window for forming a glass ribbon from low viscosity glass melt in accordance with some embodiments of the present disclosure.

[0033] FIG. 7 is a side view of another example apparatus that may be used to process a low viscosity glass melt in accordance with some embodiments of the present disclosure.

[0034] FIG. 8 is front view of an example roller than may be included on or more apparatuses of the present disclosure.

[0035] FIG. 9 is a flow chart illustrating an example method of producing a glass ribbon from low viscosity glass melt in accordance with some embodiments of the present disclosure.DETAILED DESCRIPTION

[0036] This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.

[0037] For purposes of the description hereinafter, it is to be understood that the embodiments described below may assume alternative variations and embodiments. It is also to be understood that the specific articles, compositions, and / or processes described herein are exemplary and should not be considered as limiting.

[0038] In the present disclosure the singular forms “a,” “an,” and “the” include the plural reference, and reference to a particular numerical value includes at least that particular value, unless the context clearly indicates otherwise. When values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. As used herein, “about X” (where X is a numerical value) preferably refers to ±10% of the recited value, inclusive. For example, the phrase “about 8” preferably refers to a value of 7.2 to 8.8, inclusive. Where present, all ranges are inclusive and combinable. For example, when a range of “1 to 5” is recited, the recited range should be construed as including ranges “1 to 4”, “1 to 3”, “1-2”, “1-2 & 4-5”, “1-3 & 5”, “2-5”, and the like. In addition, when a list of alternatives is positively provided, such listing can be interpreted to mean that any of the alternatives may be excluded, e.g., by a negative limitation in the claims. For example, when a range of “1 to 5” is recited, the recited range may be construed as including situations whereby any of 1, 2, 3, 4, or 5 are negatively excluded; thus, a recitation of “1 to 5” may be construed as “1 and 3-5, but not 2”, or simply “wherein 2 is not included.” It is intended that any component, element, attribute, or step that is positively recited herein may be explicitly excluded in the claims, whether such components, elements, attributes, or steps are listed as alternatives or whether they are recited in isolation.

[0039] The present disclosure provides apparatuses and methods for producing glass ribbon from a glass melt delivered at low viscosities. In some examples, the glass melt may be delivered in vertical orientation and may undergo one or more rolling processes. The apparatuses and methods may include variations to glass production systems that are used with glass melts delivered at higher relative viscosities.

[0040] Unless expressly indicated otherwise, the terms “glass ribbon,” “glass article,” or “glass” used herein are understood to encompass any object made wholly or partly of glass. Glass articles include monolithic substrates, or laminates of glass and glass, glass and non-glass materials, glass and crystalline materials, and glass and glass-ceramics (which include an amorphous phase and a crystalline phase).

[0041] Exemplary glasses can include, but are not limited to, aluminosilicate, alkalialuminosilicate, borosilicate, alkali-borosilicate, aluminoborosilicate, alkali- aluminoborosilicate, and other suitable glasses. Non-limiting examples of glasses that may be processed using the apparatuses and methods of the present disclosure include GORILLA® glasses from Corning Incorporated. The glass article may be optionally strengthened. In some embodiments, the glass article may be strengthened mechanically by utilizing a mismatch of the coefficient of thermal expansion between portions of the article to create acompressive stress region and a central region exhibiting a tensile stress. In some embodiments, the glass article may be strengthened thermally by heating the glass to a temperature above the glass transition point and then rapidly quenching. In some other embodiments, the glass article may be chemically strengthening by ion exchange.

[0042] In the context of the present disclosure, the terms high viscosity and low viscosity are used to describe the glass melts that are delivered during the process of producing a glass ribbon. A glass melt may be delivered after the glass ingredients are mixed and / or melted. Different glass ingredients may be used to produce glass ribbons that have different properties and end uses. Such different glass compositions may have different glass properties that may affect how the glass is produced. One such property is the viscosity of the glass at or near the liquidus temperature of the glass composition. In some glass production processes, the glass is delivered to the glass ribbon production process at or near the liquidus temperature of the glass composition. For purposes of the present disclosure, the term high viscosity is used to describe a glass that has a liquidus viscosity in the range of about 1300 to about 2000 poise. The term low viscosity is used in the present disclosure to describe a glass that has a liquidus viscosity above delivery viscosity in the range of about 10 poise to about 500 poise. In some examples, the low viscosity indicates a delivery viscosity less than about 500 poise. As can be appreciated, the low viscosity glasses of the present disclosure can have a delivery viscosity of at least half of the delivery viscosity of the high viscosity glasses of the present disclosure.

[0043] Referring now to FIG. 1, an example glass production process 100 is shown. The process 100 may include one or more stations that perform actions on the delivered glass melt to form a glass ribbon 122. As can be appreciated, prior to arriving at the process 100, the glass composition is created by mixing and melting glass ingredients according to a predetermined glass recipe. The melted glass composition is then delivered to the process 100 via a downcomer 102. The downcomer 102, in the example shown, includes a fishtail 116. The fishtail 116 has a wider width than the upstream downcomer 102 that may function to distribute the glass melt 120 on a set of rollers 104.

[0044] In an exemplary production process, the rollers 104, 106 may be located in one or more roller stations that serve to shape and cool the glass ribbon 122 to a temperature at or around the softening point. The glass ribbon 122 may then be turned (in this example, about 90 degrees) to a horizontal orientation at a viscous turn 106. The glass ribbon 122 may then be moved through a first cooling station 108 and a horizontal flattening station with flattening rollers 110. The glass ribbon may then proceed through a second cooling station112 to a score and separation station 114. The separated glass sheets may then be moved through a final cooling station 116 before being packaged and delivered to customer.

[0045] As shown, the initial portions of the process 100 may be oriented vertically as shown. The initial rolling distance 130 may be varied to cause a desired amount of cooling and shaping to be performed to produce the continuous glass ribbon 122 that is free of defects and that has the desired glass properties for the end use of the glass. As will be further described below, the number of rollers 104, 106, the position of the rollers 104, 106, and the geometry of the rollers 104, 106 may be varied and configured depending on the properties of the glass melt 120 that exits the downcomer 116. Other aspects may also be varied as needed to produce a high-quality, high-yield glass ribbon. Such other aspects may include a flow rate of the glass melt 122, and / or a relative distance between the rollers 104, 106.

[0046] While the process 100 shows a process in which the glass ribbon 122 is changed from a vertical orientation to a horizontal orientation in the process, it should be appreciated that the methods and apparatuses of the present disclosure may be used in other process or in combination with other apparatuses that may vary from the process 100 shown in FIG. 1.

[0047] Referring now to FIG. 2, an example apparatus 200 for the production of a glass ribbon 222 is shown. The apparatus 200 illustrates aspects of an apparatus that may be used to produce the glass ribbon 222 and it should be appreciated that other stations or further aspects may be also included in the apparatus 200. For example, the stations and elements described with respect to FIG. 1 may be included with the apparatus 200 to product glass sheets from the glass ribbon 222. In this example, the apparatus 200 may include downcomer 202, fishtail 204, first roller 206, second roller 208, third roller 210, and a fourth roller 212. The apparatus 200 may be arranged for the vertical delivery of a glass melt 220 from the downcomer 202 and the fishtail 204. The glass melt 220 may be a high viscosity glass melt. The glass melt 220 may have a viscosity in a range of about 1300 to about 2000 poise. In other examples, the glass melt 220 may have a higher viscosity.

[0048] The fishtail 204 may be needed in this example to distribute the high viscosity glass melt 220 across a width of the rollers 206, 208 (i.e., in a direction into the page of FIG. 2). As can be seen, the glass melt 220 may pool or accumulate as it is delivered to the first set of rollers. The glass melt 220 may be shaped and cooled as it contacts the first roller 206 and the second roller 208. The first roller 206 and the second roller 208 are separated from one another by a first gap 234. The glass melt 220 is shaped and cooled into the glass ribbon222 as it passes between the first roller 206 and the second roller 208 through the first gap 234.

[0049] In the example shown, the apparatus 200 includes a second pair of rollers that include the third roller 210 and the fourth roller 212. The third roller 210 and the fourth roller 212 may be separated from one another by a second gap 232. The glass melt 220 may be further flattened and cooled as it passes between the third roller 210 and the fourth roller 212 through the second gap 232. The second gap 232 may be smaller than the first gap 234. As further shown, the apparatus 200 illustrates a configuration in which the downcomer 202, the first gap 234, the second gap 232, and the glass ribbon 222 are aligned along axis 230. These elements may be aligned along a plane (i.e., into the page of FIG. 2) along axis 230.

[0050] It has been observed that apparatuses such as apparatus 200 may not be suitable to produce glass ribbons for glass melts that have low viscosities when the glass melt is delivered to the rollers. When an apparatus that is configured to produce a glass ribbon from a high viscosity glass melt is used with a low viscosity glass melt, the glass melt and / or glass ribbon breaks, prematurely separates, is not sufficiently distributed along the rollers, or suffers from other defects and quality issues. Thus, a glass production apparatus configured for high viscosity glass melt cannot be used in the same configuration for low viscosity glass melts with an expectation of successfully producing a high quality glass ribbon at desirable yield levels. The apparatuses and methods of the present disclosure may include one or more alterations, variations, or changes to apparatuses and methods used for high viscosity glass melts, to make the apparatuses and methods suitable for production of glass ribbons from low viscosity glass melts. Such improvements may allow glass ribbons to be produced from low viscosity glass melts with sufficient quality, yields, and cost.

[0051] Referring now to FIG. 3, another example apparatus 300 is shown. The apparatus 300, in this example, may be used to produce a glass ribbon 322 from a low viscosity glass melt 320. The low viscosity glass melt 320 may have the ranges of viscosity described above and may have viscosities less than about 400 poise. In some examples, the low viscosity glass melts may have a viscosity of less than about 100 poise. Existing apparatuses and methods are unable to produce glass ribbons from such low viscosity glass melts at desirable quality and yield levels.

[0052] The apparatus 300 may be different from or have variations from the apparatus 200 previously described. For example, the apparatus 300 may not include a fishtail. The apparatus 300 may include the downcomer 302 and the fishtail may not be needed since the low viscosity glass melt 320 may distribute itself along the first roller 306 and the secondroller 308. The apparatus 300 may include multiple pairs of rollers as may be needed to extract a suitable amount of thermal energy from the glass melt 320 to cool the glass melt 320. In this example, the apparatus 300 may include three pairs of rollers. In other examples, a single pair, two pair, or other amounts of rollers may be used. The apparatus 300 may include a first pair of rollers that includes the first roller 306 and the second roller 308. The first roller 306 and the second roller 308 may be separated from one another by a first gap 342. The apparatus 300 may also include a second pair of rollers that includes a third roller 310 and a fourth roller 312. The third roller 310 and the fourth roller 312 may be separated from one another by a second gap 344. The apparatus 300 may also include a third pair of rollers that includes a fifth roller 314 and a sixth roller 316. The fifth roller 314 and the sixth roller 316 may be separated from one another by a third gap 346.

[0053] Various sizes, dimensions, relative locations, relative positions, mass flow rate, and other features of the apparatus 300 may be varied in order to produce a glass ribbon at desired quality levels and / or desired yields. The various aspects of the apparatus 300 that may be varied according to the properties of the glass composition and / or the glass melt 320 include: (1) an overall height h (or other distance for non-vertical systems) of the rolling process; (2) a mass flow rate m of the glass melt delivered to the rolling process; (3) a thermal and mass distributions of the glass melt delivered to the rolling process; (4) a number of rolling stages (i.e., number of roller pairs); (5) a horizontal alignment / offset Ax of the rolling stages; (6) a heat loss q between rolling stages; and (7) an inner radius n and outer radius r0of each of the rollers. In some examples, one of these aspects may be used to achieve a desired quality and yield level for the glass ribbon 322. In other examples, one or more may be used in combination to achieve a desired quality and yield level for a glass ribbon 322.

[0054] The first aspect, the overall height h, of the rolling process may be the distance from the downcomer 302 to the exit or downstream position from the last of the roller stages in the process. This overall height h may need to be greater than in other configurations to allow room for multiple rolling stages and / or to allow thermal losses between rolling stages.

[0055] The second aspect, the mass flow rate m, may generally translate to the amount and speed of glass melt that is delivered to the rolling process. The glass melt 320 may pool or accumulate at each of the rolling stages in the apparatus and the mass flow rate m may control and / or adjust the distribution of the glass melt across the rollers and may allow the yield to be adjusted to produce a desired quantity of glass ribbon in a particular period oftime. The mass flow rate m may also be used to vary the amount of thermal energy lost at various rolling stages and between each of the rolling stages.

[0056] The third aspect, the thermal and mass distributions of the glass melt, may perform similar to the mass flow rate m, in that the thermal and mass distributions, may be adjusted or varied to allow a desired amount of glass melt shaping and cooling to occur at each of the stages. The thermal and mass distributions may also influence a size, configuration, and / or position of each of the rollers in the various rolling stages.

[0057] The fourth aspect, a number of rolling stages, may be used to influence or determine an amount and location of glass melt shaping and of thermal energy loss during the rolling stages. In some examples, one roller station may be used. In other examples, two rolling stages may be used. In still other examples, three or more rolling stages may be used.

[0058] The fifth aspect, the horizontal alignment / offset Ax of the rolling stages, may be used to influence thermal energy and distribution of the glass melt in the rolling process. As shown above in apparatus 200, the rolling stages may be aligned. As shown in apparatus 300, the rolling stages may be offset from one another. As shown, the second pair of rollers that includes the third roller 310 and the fourth roller 312 is offset from the first pair of rollers 306, 308. The glass melt 320 may exit the first gap 342 and be deposited on a portion of the fourth roller 312 and not in alignment with the second gap 344. The glass melt 320 may travel further along a circumference of the fourth roller 312 than it otherwise would if the gaps were aligned. In this configuration, more thermal energy can be removed from the glass melt 320. As further shown, the third gap 346 is offset from the second gap 344. Thus, the glass melt 320 is delivered to the surface of the fifth roller 314 away from the third gap 322. More thermal energy may be removed from the glass melt 320 than if the gaps were aligned. The distance of the offset between sequential pairs of rollers may be varied to remove a desired amount of thermal energy. The offset may also be used to allow a wider rolling process window to be achieved in which the range of feasible combination of speeds and gaps between sequential pairs of rollers is extended. This allows modulation of the thermal extraction in each rolling stage and can help prevent the onset of process instability where lapping or folding of the glass ribbon occurs between rolling stages.

[0059] The sixth aspect, the heat loss q between rolling stages, may also be used to control an amount and rate of cooling that may occur to the glass melt in the rolling process. The heat loss q may be adjusted or controlled by varying a distance between subsequent rolling stages. The heat loss q may be adjusted or controlled by modifying the environment between rolling stages such as by moving air via fans, air pipettes, air blades, or aircontrollers. In other examples, the ambient temperature may be adjusted or controlled between rolling stages.

[0060] The seventh aspect, inner radius n and outer radius r0of each of the rollers, may be used to configure each of the rolling stages to extract a desired amount of thermal energy from the glass melt 320. Each of the rollers in a pair may be configured to have the same size. In other examples, each of the rollers may have different size or different roller pairs may have different sizes. The configuration of the rollers such as surface texture, geometry of the rollers, end tapers, asymmetrical shaping along widths or other modifications to the rollers may also be used to obtain a desired quality and cooling of the glass melt 320 as well as a stable interaction between the glass and the roll surface.

[0061] Referring back to FIG. 3, the apparatus 300, in this example, includes the three pairs of rollers. As shown, the second pair of rollers may be offset from the first pair of rollers. The glass melt 320 may be aligned along an axis (or plane) 330 when it is delivered from the downcomer 302 to the first roller 306 and the second roller 308. The gap 342 between the first roller 306 and the second roller 308 may be aligned with the axis 330.

[0062] The second gap 344 may be horizontally offset from the first gap 342 by a distance Axi. The distance Axi may be measured as a horizontal distance between the axis 330 and a second axis (or plane) 332. The second axis 332 may be aligned with the second gap 344. The third gap 346 may be offset from the second gap 344 by a distance Ax2. The second distance may be aligned with the third gap 346 and may be measured as a horizontal distance between the second axis 322 and a third axis (or plane) 334. The first distance Axi and the second distance Ax2 may be the same or may be different from one another.

[0063] The apparatus 300 illustrates one example configuration that may be used for a particular glass composition or glass melt. Modifications to one or more of the aspects described above may be made to achieve a desired quality and yield level for a particular glass composition or glass melt.

[0064] In some examples, a method of modifying an existing glass production apparatus is contemplated. In such methods, an existing glass production may be modified by changing one or more of the aspects described above in the rolling stations of the glass production apparatus. The method may include determining a total heat extraction requirement that is needed to achieve glass quality and yield levels for a particular glass composition or glass melt. Such determination may be made by experimental or laboratory testing or may be determined using glass production models that may be built using historical data or simulation data.

[0065] The method may also include modifying a rolling process of the glass production apparatus to achieve the total heat extraction requirement. The modification may include modifying or adding one of the aspects described above such as modifying or adding: (1) an overall height h (or other distance for non-vertical systems) of the rolling process; (2) a mass flow rate m of the glass melt delivered to the rolling process; (3) a thermal and mass distribution of the glass melt delivered to the rolling process; (4) a number of rolling stages (i.e., number of roller pairs); (5) a horizontal alignment / offset Ax of the rolling stages; (6) a heat loss q between rolling stages; and (7) an inner radius n and outer radius r0of each of the rollers.

[0066] In various examples of the method above, the method may include determining the unitary heat extraction in a single rolling stage configuration and comparing it to the required unitary heat extraction. If less than required, the method may include determining the accumulated unitary heat extraction from the first and second stages in a dual-stage rolling configuration and comparing it to the required unitary heat extraction. If less than required, the method may include determining the accumulated unitary heat extraction from the first, second and third stages in a triple-stage rolling configuration and comparing it to the required unitary heat extraction. These steps may be continued by successive calculation until the computed unitary rolling heat extraction meets or exceeds the required unitary heat extraction. These steps may be used to determine the rolling configuration (number of stages, and geometry of stages) for the glass composition or application.

[0067] A unitary heat extraction rate requirement may also be determined. The unitary heat extraction rate may be determined by dividing the total heat extraction by the formed ribbon width. It may be determined that a rolling process is adequately sized if the heat extraction rate matches (is about equal to) the total heat extraction requirement. The unitary heat extraction rates in a rolling process may be dependent on the glass temperature, the roll temperature, the glass-to-roll contact heat transfer coefficient, and the glass-to-roll contact length. The contact heat transfer coefficient is a parameter that encompasses the effectiveness of the glass-to-roll contact as a function of contact pressure, roll roughness, and glass viscosity.

[0068] These steps may be used in combination with various inputs such as glass flow rate, minimum glass delivery temperature (based on liquidus limitations), and target exit temperature to determine a desired configuration of rolling process in a glass production apparatus.

[0069] The above method has been used and improved glass production apparatuses have been tested to demonstrate the viability of the improved glass production apparatuses for low viscosity glass melts. As shown in FIG. 4, the diagram 402 illustrates a capability of implementing the apparatuses and methods of the present disclosure. The capability of the production of glass ribbon from a low viscosity glass melt has been achieved using an apparatus similar to the apparatuses described in the present disclosure. In one example, the capability of using a common glass production apparatus (with one or more of the modifications described above) has been demonstrated to produce satisfactory glass ribbons from high viscosity glass melts and low viscosity glass melts. The high viscosity boundary line 402 illustrates a relationship between the thickness of the glass ribbon and the flow rate to produce glass ribbons (of various compositions) from a high viscosity glass melt. The boundary line 402 generally illustrates where a single-stage rolling station (IS) may be used versus a dual-stage rolling station (2S) for the high viscosity glass melts. As can be seen, the boundary line moves downward to boundary line 404 for low viscosity glass melts.Generally, for a similar thickness, the low viscosity (LV) glass melts require a dual stage rolling station (2S) at lower flow rates than the high viscosity glass melts.

[0070] The initial testing illustrated in the graph 402 has demonstrated that low viscosity (LV) glass melts in the range of about 260 to about 500 poise range have been used to produce satisfactory glass ribbons at flow rates in the range of about 950 Ibs / hr to about 1300 Ibs / hr. Such satisfactory glass ribbons have been produced that have ribbon thicknesses in a range of about 0.7mm to about 4.0 mm and for ribbon widths in a range of about 249 mm to about 305 mm using single-stage rolling stations (IS) and dual-stage (2S) rolling stations.

[0071] Further testing of the methods and apparatuses of the present disclosure were performed to result in further robustness achievements and to allow further improvements on the ranges of low viscosity glass melts described above. As shown in FIG. 5, the methods and apparatuses of the present disclosure were used to achieve improved process windows to allow high viscosity and low viscosity glass melts to be used to produce satisfactory glass ribbons from a similar production systems using modification to the aspects of the rolling process described above. FIG. 5 includes graph 500 illustrating a process window for one example embodiment for a 3.0 mm glass ribbon. The graph 500 illustrates testing performed that plots delivery viscosity versus flow rate. In this graph, the boundaries 506, 508, 510 illustrate the boundaries of production processes in which single-stage, dual-stage, and triplestage rolling process are used, respectively. The high viscosity boundary 502 and the low- viscosity boundary 504 illustrate a similar relationship as previously discussed above.

[0072] As shown in FIG. 5, the testing performed using the methods and apparatuses of the present disclosure show that the addition of rolling stages may improve the flow rate for low viscosity glass melts. For example, to produce a 3.0 mm glass ribbon, the flow rate for a low viscosity glass melt having a delivery viscosity of below 400 poise may be increased by about 200 Ibs / hr when a triple-stage rolling process is used as compared to a dual-stage rolling process.

[0073] Referring now to FIG. 6, another graph 600 is shown. The graph 600 illustrates a rolling forming process window for an example 3.0 mm glass ribbon delivered as a low viscosity glass melt with a deliver viscosity at or below about 400 poise. The graph 600 plots test results for the same low viscosity glass melt delivered to single-stage, dualstage, and triple-stage rolling processes. As demonstrated, the addition of rolling stages allow low viscosity glass melts to be produced at increased mass flow rates to allow improved yields over existing processes.

[0074] While not shown, other testing has successfully demonstrated the capability of implementing the methods and apparatuses of the present disclosure to produce glass ribbons from low viscosity glass melts in the ranges described above.

[0075] Referring now to FIG. 7, another example apparatus 700 is shown. The apparatus 700 may be used to produce a glass ribbon 722 from a low viscosity glass melt 720. The glass melt 720 may be delivered from a downcomer 702. The downcomer 702 may be aligned with the gap 740 that is located between the first roller 704 and the second roller 706. The glass may then travel to the second rolling station. As shown, the gap 742 at the second rolling station may be offset from the first gap 740 by a horizontal distance x.

[0076] In this example, the outer diameter of the first roller 704 and the second roller 706 may be larger than the outer diameter of the third roller 708 and the fourth roller 710. In one example, the first roller 704 and the second roller 706 are in a range of about 20% to about 40% larger in outer diameter than the third roller 708 and the fourth roller 710. In other examples, the first pair of rollers and the second pair of rollers may be of other relative sizing. The larger rollers in the first stage of rolling allow increased relative heat extraction due to the increase in surface area and the increase in the glass-to-roll contact pressure. The offset between the first pair of rollers and the second pair of rollers allows a higher top-to- bottom roll speed ratio and a narrower gap at the first stage of rollers. These allow for increased thermal extraction.

[0077] It has also been observed that lapping or folding of the glass ribbon may occur between rolling stages. To improve the robustness of the process, the rolling stages may beoffset as shown in FIG. 7 and described above. The offset of the rolling stages not only improves the extraction of thermal energy from the glass melt 720 but also mitigates the likelihood that the glass melt folds or laps when it is delivered to a subsequent rolling station.

[0078] Turning now to FIG. 8, an example roller 800 is shown. The roller 800 may be used in one or more of the apparatuses described above. The roller 800 may be used in the rolling stations after the low viscosity glass melt is delivered to the glass rolling process. In the figures above, the rollers were shown from an end view. In FIG. 8, a width of the roller or a front view of the roller 800 is shown. The glass melt may be delivered to the roller 800 in a direction shown by the arrow in FIG. 8. the glass melt may contact the outer surface 802 of the roller 800. To control or adjust the thermal energy that is extracted from the glass melt, the outer diameter Do and / or the inner diameter Di of the roller 800 may be varied. The outer diameter Do and / or the inner diameter Di of the roller can be varied as well as to allow a stable interaction between the glass and the roll surface. As shown in FIG. 8, the inner diameter may be different across the width of the roller 800 as shown by tapered inner diameter 808. Instead of having a constant inner diameter Di shown by inner diameter 810, the inner diameter may be tapered. In one example, the inner diameter Di may be smaller toward the ends and greater toward the middle. In still other examples, a surface texture of the outer surface 802 may be modified or customized to achieve a desired thermal exchange and / or to reduce a likelihood of quality issues or defects.

[0079] In some embodiments, a method 900 of producing a glass ribbon is provided. The method 900 may be performed using one or more of the apparatuses and systems described in this disclosure such as apparatuses 300, 700. The method 900 may also be performed by other systems or apparatuses and / or variations of the apparatuses described herein. For the sake of illustration, the method 900 is described with reference to the apparatus 300 but it should be appreciated that the method 900 is not limited to this apparatus.

[0080] The method 900 begins at step 902. At step 902, glass melt is delivered to a first pair of rollers. In the apparatus 300, the downcomer 302 may deliver the glass melt to the first pair of rollers that include the first roller 306 and the second roller 308. The glass melt may be a low viscosity glass melt that has the viscosity in the ranges described above. In one example, the viscosity of the glass melt may be less than about 500 poise.

[0081] The method 900 may continue to step 904. At step 904, the glass melt may be rolled in the first gap 342 between the first roller 306 and the second roller 308. The geometry and function of the rollers may be selected so that the rollers remove apredetermined amount of thermal energy from the glass melt at the first pair of rollers as the glass melt is shaped and cooled by the first roller 306 and the second roller 308.

[0082] The method 900 may continue to step 906. At step 906, the glass melt may be rolled in a second gap 344 between a third roller 310 and a fourth roller 312. The third roller 310 and the fourth roller 312 may be separated to define the second gap 344. In some embodiments, the second gap 344 is horizontally offset from the first gap 342. In this configuration, the glass melt may be delivered to an outer surface of the fourth roller 312 at a position spaced apart or away from the second gap 344. As the glass melt resides on the outer surface and moves toward the second gap 344, the glass melt is cooled. The geometry and function of the third roller 310 and the fourth roller 312 may be selected so that the rollers remove a predetermined amount of thermal energy from the glass melt as it moves downstream in the process.

[0083] The method 900 may continue to step 908. At step 908, the glass melt may be rolled in a third gap 346 between a fifth roller 314 and a sixth roller 316. The fifth roller and the sixth roller 316 may be separated to define the third gap 346. In some embodiments the third gap 346 may be horizontally offset from the second gap 344. In still other embodiments, the first gap 342, the second gap 344, and the third gap 346 may be offset from one another and none of the gaps may be vertically aligned.

[0084] After step 908, the method 900 may end. While not shown, the method 900 may continue and may include other functions to continue to form the glass ribbon and to separate glass sheets from the glass ribbon as described with reference to FIG. 1.

[0085] As can be appreciated, the steps of method 900 in some embodiments are optional. In some examples, the method 900 may include a single stage of rolling. In other examples, the method 900 may include two stages of rolling. In still other examples, the method may include a third stage of rolling or other quantities of rolling stages.

[0086] The methods and system described herein may be at least partially embodied in the form of computer-implemented processes and apparatus for practicing those processes. The disclosed methods may also be at least partially embodied in the form of tangible, nontransient machine readable storage media encoded with computer program code. The media may include, for example, RAMs, ROMs, CD-ROMs, DVD-ROMs, BD-ROMs, hard disk drives, flash memories, or any other non-transient machine-readable storage medium, or any combination of these mediums, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the method. The methods may also be at least partially embodied in the form of a computer into whichcomputer program code is loaded and / or executed, such that, the computer becomes an apparatus for practicing the methods. When implemented on a general-purpose processor, the computer program code segments configure the processor to create specific logic circuits. The methods may alternatively be at least partially embodied in a digital signal processor formed of application specific integrated circuits for performing the methods.

[0087] Although the subject matter has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments, which may be made by those skilled in the art.

Claims

CLAIMSWhat is claimed is:

1. A method for producing a glass ribbon comprising: delivering a glass melt to a first pair of rollers; rolling the glass melt between the first pair of rollers in a first gap; and rolling the glass melt in a second gap between a second pair of rollers, wherein the second gap is offset from the first gap and located downstream from the first gap.

2. The method of claim 1, wherein the glass melt has a viscosity of less than about 500 poise.

3. The method of claim 1, wherein the second gap is offset in a horizontal direction from the first gap.

4. The method of claim 1, wherein the offset causes the glass melt to be delivered to an outer surface of one roller of the first pair of rollers at a position spaced horizontally from the second gap.

5. The method of claim 1, wherein an outer diameter of the first pair of rollers is different than an outer diameter of the second pair of rollers.

6. The method of claim 1, wherein the glass melt is delivered to the first pair of rollers from a downcomer in a vertical orientation.

7. The method of claim 6, wherein the glass melt is delivered from the downcomer without a fishtail.

8. The method of claim 1, further comprising rolling the glass melt in a third gap between a third pair of rollers, wherein the third gap is offset from the second gap and located downstream from the first gap.

9. The method of claim 8, wherein the first gap, the second gap, and the third gap are not aligned along a common axis.

10. The method of claim 8, wherein an outer diameter of the third pair of rollers are different from an outer diameter of the first pair of rollers and the second pair of rollers.

11. An apparatus comprising: a downcomer configured for delivering a low viscosity glass melt for production of a glass ribbon; and at least one pair of rollers positioned vertically below the downcomer, the at least one pair of rollers comprising a first roller and a second roller spaced apart from each other to form a first gap, wherein the first roller and the second roller remove a predetermined amount of thermal energy from the low viscosity glass melt to produce the glass ribbon.

12. The apparatus of claim 11, wherein the low viscosity glass melt has a viscosity of less than about 500 poise.

13. The apparatus of claim 11, wherein the at least one pair of rollers further comprises a second pair of rollers comprising a third roller and a fourth roller spaced apart from each other to form a second gap.

14. The apparatus of claim 13, wherein the second gap is horizontally offset from the first gap-15. The apparatus of claim 13, wherein an outer diameter of the first roller and the second roller is different from an outer diameter of the third roller and the fourth roller.

16. The apparatus of claim 13, wherein an inner diameter of the first roller and the second roller is different from an inner diameter of the third roller and the fourth roller.

17. The apparatus of claim 11, wherein the downcomer delivers the low viscosity glass melt to the at least one pair of rollers in a vertical direction without a fishtail.

18. The apparatus of claim 11, wherein the glass melt contacts an outer surface of the first roller or the second roller at a position spaced horizontally from the first gap.

19. The apparatus of claim 11, further comprising one or more air pipettes or air blades positioned downstream of the downcomer configured to cool the glass melt.

20. The apparatus of claim 13, wherein the at least one pair of rollers further comprises a third pair of rollers comprising a fifth roller and a sixth roller spaced apart from each other to form a third gap, the third gap horizontally offset from the second gap.

Images