Method for forming glass ribbon from low viscosity conveyed glass melt

Abstract

A method for producing a glass ribbon includes conveying a glass melt to a first pair of rollers, and rolling the glass melt between the first pair of 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 and downstream of the first gap.

Description

[0001] Priority Claims and Cross-References

[0002] This application claims the benefit of priority of U.S. Provisional Application Serial No. 63 / 602,747, filed on November 27, 2023, the content of which is relied upon herein and incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to methods and apparatus for forming a glass ribbon from a glass melt that is transported at a low viscosity. Background Art

[0004] Glass production can include the production of a continuous glass material ribbon or web. Such production methods can include transporting a glass melt that is formed into a glass ribbon for further processing. Requirements for the final glass product can include desired thickness, width, quantity, or other requirements. For example, the final glass product can be used in consumer electronics applications, and such applications may have specific requirements for a particular consumer electronics product. In turn, the requirements for the glass product may limit the properties of various glasses, as certain glass compositions may be required to achieve these glass properties. For example, such limitations on glass properties can include liquidus viscosity and absorption coefficient.

[0005] Existing production methods and apparatus can be configured to produce glass ribbons for specific glass products having a certain range of glass property characteristics. Existing production methods and apparatus may be limited in their ability to produce glass ribbons from glass melts having glass properties outside of a specific range. If existing and / or traditional production methods and apparatus are used to produce glass ribbons outside of the range of glass ribbon properties for which they are designed, it may result in a high proportion or number of poor quality glasses, may result in a low yield of glass ribbons acceptable for end use, and / or may not be able to produce the desired glass ribbon at all. Accordingly, there is a need to improve apparatus and methods for producing glass ribbons that can have a wider range of glass properties, such as being able to produce acceptable glass ribbons from a low viscosity glass melt. Summary of the Invention

[0006] This disclosure provides apparatus and methods for producing a low viscosity glass ribbon.

[0007] In some embodiments of the present disclosure, a method for producing a glass ribbon is provided. The method can include transporting 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 is downstream of the first gap.

[0008] In one aspect, the glass melt can have a viscosity of less than about 500 poise.

[0009] In another aspect, the second gap may be offset from the first gap in the horizontal direction.

[0010] In another aspect, the offset may cause the glass melt to be delivered to the outer surface of one of the first pair of rollers at a location horizontally spaced from the second gap.

[0011] In another aspect, the outer diameter of the first pair of rollers may be different from the outer diameter of the second pair of rollers.

[0012] In another aspect, the glass melt may be delivered from the downcomer to the first pair of rollers in a vertical orientation.

[0013] In another aspect, the glass melt may be delivered from a downcomer without a tail.

[0014] 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 is downstream of the first gap.

[0015] In another aspect, the first gap, the second gap, and the third gap may not be aligned along a common axis.

[0016] In another aspect, the outer diameter of the third pair of rollers may be different from the outer diameters of the first pair of rollers and the second pair of rollers.

[0017] In some embodiments of the present disclosure, an apparatus for producing a glass ribbon from a low-viscosity glass melt is provided. The apparatus may include: a downcomer configured to deliver the low-viscosity glass melt to produce a glass ribbon; and at least one pair of rollers vertically located 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.

[0018] In one aspect, the low-viscosity glass melt may have a viscosity of less than about 500 poise.

[0019] In another aspect, the at least one pair of rollers may include a second pair of rollers including a third roller and a fourth roller spaced apart from each other to form a second gap.

[0020] In another aspect, the second gap may be horizontally offset from the first gap.

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

[0022] In another aspect, the inner diameters of the first roller and the second roller may be different from the inner diameters of the third roller and the fourth roller.

[0023] In another aspect, the downcomer can convey a low-viscosity glass melt vertically without fishtailing to at least a pair of rollers.

[0024] In another aspect, the glass melt can contact the outer surface of the first roller or the second roller at a position horizontally spaced from the first gap.

[0025] In another aspect, the apparatus can include one or more air suckers or air vanes located downstream of the downcomer, and the one or more air suckers or air vanes are configured to cool the glass melt.

[0026] In another aspect, at least a pair of rollers can include a third pair of rollers, and the third pair of rollers includes a fifth roller and a sixth roller spaced apart from each other to form a third gap. The third gap can be horizontally offset from the second gap. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present disclosure can be most thoroughly understood when the following detailed description is read in conjunction with the accompanying drawings. It should be emphasized that, according to convention, the various features of the drawings are not necessarily drawn to scale. Instead, for clarity, the dimensions of the various features are arbitrarily enlarged or reduced. Throughout the specification and the drawings, the same reference numerals denote the same features.

[0028] Figure 1 is a side view of an exemplary glass production system according to some embodiments of the present disclosure.

[0029] Figure 2 is a side view of an exemplary apparatus that can be used to process a glass melt into a glass ribbon according to some embodiments of the present disclosure.

[0030] Figure 3 is a side view of another exemplary apparatus that can be used to process a low-viscosity glass melt according to some embodiments of the present disclosure.

[0031] Figure 4 is a graph showing the capabilities of a glass production process using one or more apparatuses of the present disclosure.

[0032] Figure 5 is a graph showing a planned process window for forming a glass ribbon from a low-viscosity glass melt according to some embodiments of the present disclosure.

[0033] Figure 6 is a graph showing another process window for forming a glass ribbon from a low-viscosity glass melt according to some embodiments of the present disclosure.

[0034] Figure 7 is a side view of another exemplary apparatus that can be used to process a low-viscosity glass melt according to some embodiments of the present disclosure.

[0035] Figure 8 Front view of an exemplary roll that may be included in one or more devices of the present disclosure.

[0036] Figure 9 Flowchart showing an exemplary method for producing a glass ribbon from a low-viscosity glass melt according to some embodiments of the present disclosure. Detailed Description

[0037] The description of the exemplary embodiments is intended to be read in conjunction with the accompanying drawings, which are considered to be a part of the entire written description. In this description, relative terms such as "lower", "upper", "horizontal", "vertical", "above", "below", "upward", "downward", "top", and "bottom" and their derivatives (e.g., "horizontally", "downwardly", "upwardly", etc.) should be construed to refer to the orientation shown in the drawings as subsequently described or discussed. These relative terms are for convenience of description and do not require the device to be constructed or operated in a particular orientation. Terms regarding attachment, coupling, etc., such as "connected" and "interconnected", refer to the relationship of structures being fastened or attached to each other directly or indirectly through intervening structures, and to either a movable or rigid attachment or relationship, unless otherwise explicitly described.

[0038] For purposes of the following description, it should be understood that the embodiments described below may have alternative variations and embodiments. It should also be understood that the specific articles, compositions, and / or processes described herein are merely exemplary and should not be considered restrictive.

[0039] Unless the context clearly indicates otherwise, as used in this disclosure, the singular forms "a", "an", and "the" include plural references, and references to a particular numerical value include at least that particular value. When a value is expressed as an approximation by use of the antecedent "about", it is to be understood that the particular value forms another embodiment. As used herein, "about X" (where X is a numerical value) preferably refers to a value within ±10% (including the end values) of the recited value. For example, the phrase "about 8" preferably refers to a value from 7.2 to 8.8, including the end values. Where present, all ranges are inclusive and combinable. For example, when reciting a range of "1 to 5", the recited range should be understood to include ranges such as "1 to 4", "1 to 3", "1 - 2", "1 - 2 and 4 - 5", "1 - 3 and 5", "2 - 5", etc. Further, when presenting a list of alternatives in the affirmative, such listing can be construed to mean that any alternatives can be excluded, for example, by negative limitations in the claims. For example, when reciting a range of "1 to 5", the recited range can be understood to include the case where any one of 1, 2, 3, 4, or 5 is excluded thereby negatively; thus, a recitation of "1 to 5" can be understood to be "1 and 3 - 5, but not 2", or simply "wherein 2 is not included". It is intended that any component, element, property, or step positively recited herein can be explicitly excluded in the claims, whether such components, elements, properties, or steps are listed as alternatives or recited individually.

[0040] The present disclosure provides an apparatus and method for producing a glass ribbon from a glass melt conveyed at a low viscosity. In some examples, the glass melt can be conveyed in a vertical orientation and can undergo one or more rolling processes. The apparatus and method can include a variation of a glass production system for a glass melt conveyed at a relatively higher viscosity.

[0041] Unless otherwise clearly indicated, as used herein, the terms "glass ribbon", "glass article", or "glass" shall be understood to encompass any object made wholly or in part of glass. Glass articles include single - sheet substrates, laminates of glass - to - glass, glass - to - non - glass materials, glass - to - crystal materials, and glass - to - glass - ceramic (including amorphous and crystalline phases).

[0042] Exemplary glasses can include, but are not limited to, aluminosilicates, alkali aluminosilicates, borosilicates, alkali borosilicates, aluminoborosilicates, alkali aluminoborosilicates, and other suitable glasses. Non - limiting examples of glasses that can be processed using the apparatus and methods of the present disclosure include those of Corning Incorporated Glass. The glass article can be selectively strengthened. In some embodiments, the glass article can be mechanically strengthened by taking advantage of the mismatch in the coefficient of thermal expansion between different parts of the glass article to create a region of compressive stress and a central region exhibiting tensile stress. In some embodiments, the glass article can be thermally strengthened by heating the glass to a temperature above the glass transition point and then rapidly quenching it. In some other embodiments, the glass article can be chemically strengthened by ion exchange.

[0043] In the context of the present disclosure, the terms "high viscosity" and "low viscosity" are used to describe the glass melt being conveyed during the process of producing a glass ribbon. The glass melt can be conveyed after the glass components are mixed and / or melted. Different glass components can be used to produce glass ribbons with different properties and end uses. Different glass compositions can have different glass properties, and different glass properties can affect the way the glass is produced. One such property is the viscosity of the glass at or near the liquidus temperature of the glass composition. In certain glass production processes, the glass is conveyed to the glass ribbon production process at or near the liquidus temperature of the glass composition. For the purposes of the present disclosure, the term "high viscosity" is used to describe a glass having 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 having a liquidus viscosity with a delivery viscosity in the range above about 10 poise to about 500 poise. In some examples, a low viscosity indicates a delivery viscosity of less than about 500 poise. It will be understood that the delivery viscosity of the low viscosity glass of the present disclosure can be at least half of the delivery viscosity of the high viscosity glass of the present disclosure.

[0044] Now referring to Figure 1 , an example glass production process 100 is shown. Process 100 can include one or more stations that perform actions on the conveyed glass melt to form a glass ribbon 122. It will be understood that prior to reaching process 100, a glass composition is produced by mixing and melting glass components according to a predetermined glass recipe. The molten glass composition is then conveyed to process 100 through a downcomer 102. In the example shown, the downcomer 102 includes a fish tail 116. The width of the fish tail 116 is wider than the width of the upstream downcomer 102 and can serve to distribute the glass melt 120 onto a set of rollers 104.

[0045] In an exemplary production process, rollers 104, 106 can be located in one or more roller stations for shaping and cooling a glass ribbon 122 to a temperature at or near the softening point. The glass ribbon 122 can then be turned (by approximately 90 degrees in this example) to a horizontal orientation at the viscous turn 106. The glass ribbon 122 can then move through a first cooling station 108 and a horizontal flattening station with a flattening roller 110. The glass ribbon can then continue through a second cooling station 112 to a scribing and separation station 114. The separated glass plates can then move through a final cooling station 116 and then be packaged and delivered to a customer.

[0046] As shown, an initial portion of process 100 can be in a vertical orientation as shown. The initial rolling distance 130 can be varied such that a desired amount of cooling and shaping is performed to produce a continuous glass ribbon 122 that is defect-free and has the glass properties required for the end use of the glass. As will be further described below, the number, position, and geometry of rollers 104, 106 can be varied and configured according to the properties of the glass melt 120 exiting the downcomer 116. Other aspects can also be changed as needed to produce a high-quality, high-yield glass ribbon. These other aspects can include the flow rate of the glass melt 122 and / or the relative distance between rollers 104, 106.

[0047] Although process 100 shows a process in which the glass ribbon 122 changes from a vertical orientation to a horizontal orientation, it should be understood that the methods and apparatuses of the present disclosure can be used in other processes or in combination with other apparatuses that may differ from Figure 1 the process 100 shown.

[0048] Now referring Figure 2 , an example apparatus 200 for producing a glass ribbon 222 is shown. Apparatus 200 shows aspects of an apparatus that can be used to produce a glass ribbon 222, and it should be understood that other stations or other aspects can also be included in apparatus 200. For example, the stations and elements described with respect to Figure 1 can be included in apparatus 200 to produce glass plates from the glass ribbon 222. In this example, apparatus 200 can include a downcomer 202, a fish tail 204, a first roller 206, a second roller 208, a third roller 210, and a fourth roller 212. Apparatus 200 can be arranged to vertically convey a glass melt 220 from the downcomer 202 and the fish tail 204. The glass melt 220 can be a high-viscosity glass melt. The glass melt 220 can have a viscosity in the range of about 1300 to about 2000 poise. In other examples, the glass melt 220 can have a higher viscosity.

[0049] In this example, a fish tail 204 may be required to distribute the high viscosity glass melt 220 across the width of the rollers 206, 208 (i.e., in the direction of entry Figure 2 into the page). It can be seen that the glass melt 220 may converge or accumulate when being conveyed to the first set of rollers. When the glass melt 220 contacts the first roller 206 and the second roller 208, it can be shaped and cooled. The first roller 206 and the second roller 208 are separated from each other by a first gap 234. When the glass melt 220 passes through the first gap 234 between the first roller 206 and the second roller 208, the glass melt 220 is shaped and cooled into a glass ribbon 222.

[0050] In the example shown, the apparatus 200 includes a second pair of rollers, which includes a third roller 210 and a fourth roller 212. The third roller 210 and the fourth roller 212 may be separated from each other by a second gap 232. When the glass melt 220 passes through the second gap 232 between the third roller 210 and the fourth roller 212, the glass melt 220 can be further flattened and cooled. The second gap 232 may be smaller than the first gap 234. As further shown, the apparatus 200 shows a configuration in which the downcomer 202, the first gap 234, the second gap 232, and the glass ribbon 222 are aligned along an axis 230. These elements may be aligned along a plane along the axis 230 (i.e., into Figure 2 the page).

[0051] It has been observed that an apparatus such as the apparatus 200 may not be suitable for producing a glass ribbon from a glass melt that has a low viscosity when the glass melt is being conveyed to the rollers. When an apparatus 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 the glass ribbon may break, prematurely separate, not be adequately distributed along the rollers, or there may be other defects and quality issues. Thus, a glass production apparatus configured for a high viscosity glass melt cannot be used in the same configuration for a low viscosity glass melt and expect to successfully produce a high quality glass ribbon at the desired production rate level. The apparatus and method of the present disclosure may include one or more changes, variations, or alterations to the apparatus and method for a high viscosity glass melt such that the apparatus and method are suitable for producing a glass ribbon from a low viscosity glass melt. These improvements may allow a glass ribbon to be produced from a low viscosity glass melt with sufficient quality, production rate, and cost.

[0052] Now referring to Figure 3, another exemplary apparatus 300 is shown. In this example, the apparatus 300 can be used to produce a glass ribbon 322 from a low-viscosity glass melt 320. The low-viscosity glass melt 320 can have the viscosity range described above and can have a viscosity of less than about 400 poise. In some examples, the low-viscosity glass melt can have a viscosity of less than about 100 poise. Existing apparatuses and methods cannot produce a glass ribbon from such a low-viscosity glass melt at the desired quality and production levels.

[0053] The apparatus 300 can be different from or vary from the previously described apparatus 200. For example, the apparatus 300 may not include a fish tail. The apparatus 300 can include a downcomer 302 and may not require a fish tail because the low-viscosity glass melt 320 can distribute itself along the first roll 306 and the second roll 308. The apparatus 300 can include multiple pairs of rolls as needed to extract an appropriate amount of thermal energy from the glass melt 320 to cool the glass melt 320. In this example, the apparatus 300 can include three pairs of rolls. In other examples, one pair, two pairs, or other numbers of rolls can be used. The apparatus 300 can include a first pair of rolls that includes a first roll 306 and a second roll 308. The first roll 306 and the second roll 308 can be separated from each other by a first gap 342. The apparatus 300 can also include a second pair of rolls that includes a third roll 310 and a fourth roll 312. The third roll 310 and the fourth roll 312 can be separated from each other by a second gap 344. The apparatus 300 can also include a third pair of rolls that includes a fifth roll 314 and a sixth roll 316. The fifth roll 314 and the sixth roll 316 can be separated from each other by a third gap 346.

[0054] Various sizes, dimensions, relative locations, relative positions, mass flow rates, and other characteristics of the apparatus 300 can be varied to produce the glass ribbon at the desired quality level and / or desired production rate. The various aspects of the apparatus 300 that can vary depending on the glass composition and / or the properties of the glass melt 320 include: (1) the total height h of the rolling process (or other distance for a non-vertical system); (2) the mass flow rate m of the glass melt delivered to the rolling process; (3) the heat and mass distribution of the glass melt delivered to the rolling process; (4) the number of rolling stages (i.e., the number of roll pairs); (5) the horizontal alignment / offset Δx of the rolling stages; (6) the heat loss q between the rolling stages; and (7) the inner radius r and outer radius r of each roll. i and outer radius r o . In some examples, one of these aspects can be used to achieve the desired quality and production levels of the glass ribbon 322. In other examples, one or more aspects can be used in combination to achieve the desired quality and production levels of the glass ribbon 322.

[0055] The first aspect of the rolling process, namely the total height h, can be the distance from the downcomer 302 to the outlet or downstream position of the last roll stage in the process. This total height h may need to be greater than the total height in other configurations to provide space for multiple rolling stages and / or to allow heat loss between the rolling stages.

[0056] The second aspect, namely the mass flow rate m, can generally be translated into the amount and speed of the glass melt conveyed to the rolling process. The glass melt 320 can accumulate or build up at each rolling stage in the apparatus, and the mass flow rate m can control and / or adjust the distribution of the glass melt on the rolls and can allow the adjustment of the production rate to produce the desired number of glass ribbons within a specific time period. The mass flow rate m can also be used to vary the amount of heat energy lost in each individual rolling stage as well as between each rolling stage.

[0057] The third aspect, namely the thermal and mass distribution of the glass melt, can behave similarly to the mass flow rate m in that the thermal and mass distribution can be adjusted or varied to allow the desired amount of glass melt forming and cooling to occur at each stage. The thermal and mass distribution may also affect the size, configuration, and / or position of each roll in each individual rolling stage.

[0058] The fourth aspect, namely the number of rolling stages, can be used to influence or determine the amount and location of glass melt forming during the rolling stages as well as the amount and location of heat energy loss. In some examples, one roll stand can be used. In other examples, two rolling stages can be used. In still other examples, three or more rolling stages can be used.

[0059] Fifthly, the horizontal alignment / offset Δx at the rolling stage can be used to affect the thermal energy and distribution of the glass melt in the rolling process. As shown above in apparatus 200, the rolling stages can be aligned. As shown in apparatus 300, the rolling stages can be offset from each other. As shown in the figure, the second pair of rollers including the third roller 310 and the fourth roller 312 is offset from the first pair of rollers 306, 308. The glass melt 320 can leave the first gap 342 and deposit on a part of the fourth roller 312 and is not aligned with the second gap 344. The glass melt 320 can travel further along the circumference of the fourth roller 312 than it 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 conveyed to the surface of the fifth roller 314 away from the third gap 322. More thermal energy can be removed from the glass melt 320 compared to the case where the gaps are aligned. The offset distance between consecutive roller pairs can be changed to remove the desired amount of thermal energy. The offset can also be used to allow for a wider rolling process window, where the range of feasible combinations of speed and gap between consecutive roller pairs is extended. This allows for the regulation of heat extraction at each rolling stage and can help prevent process instability when glass ribbon lapping or folding occurs between rolling stages.

[0060] Sixthly, the heat loss q between the rolling stages can also be used to control the amount and rate of cooling that may occur to the glass melt in the rolling process. The heat loss q can be adjusted or controlled by changing the distance between consecutive rolling stages. The heat loss q can be adjusted or controlled by modifying the environment between the rolling stages (such as by moving air through a fan, air suction pipe, air vane, or air controller). In other examples, the ambient temperature can be adjusted or controlled between the rolling stages.

[0061] Seventhly, the inner radius r i and outer radius r o of each roller can be used to configure each rolling stage to extract the desired amount of thermal energy from the glass melt 320. Each roller in a pair of rollers can be configured to have the same size. In other examples, each roller can have a different size or different roller pairs can have different sizes. Configurations of the rollers (such as surface texture, roller geometry, end taper, asymmetric profiling along the width, or other modifications to the rollers) can also be used to obtain the desired quality and cooling of the glass melt 320 and a stable interaction between the glass and the roller surface.

[0062] Referring again to Figure 3, in this example, the apparatus 300 includes three pairs of rollers. As shown, the second pair of rollers may be offset from the first pair of rollers. When the glass melt 320 is delivered from the downcomer 302 to the first roller 306 and the second roller 308, the glass melt 320 may be aligned along an axis (or plane) 330. The gap 342 between the first roller 306 and the second roller 308 may be aligned with the axis 330.

[0063] The second gap 344 may be horizontally offset from the first gap 342 by a distance Δx 1 . The distance Δx 1 may be measured as the 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 Δx 2 . The second distance may be aligned with the third gap 346 and may be measured as the horizontal distance between the second axis 322 and a third axis (or plane) 334. The first distance Δx 1 and the second distance Δx 2 may be the same as or different from each other.

[0064] The apparatus 300 shows an example configuration that may be used for a particular glass composition or glass melt. One or more of the above aspects may be modified to achieve the desired quality and production levels for a particular glass composition or glass melt.

[0065] In some examples, methods of modifying an existing glass production apparatus are considered. In such methods, an existing glass production may be modified by changing one or more of the above aspects in the rolling station of the glass production apparatus. The method may include determining the total heat extraction requirement needed to achieve the glass quality and production levels for a particular glass composition or glass melt. Such determination may be made experimentally or through laboratory testing, or may be determined using a glass production model that may be established using historical data or simulation data.

[0066] The method may further include modifying the rolling process of the glass production apparatus to achieve the total heat extraction requirement. The modification may include modifying or adding one of the above aspects, such as modifying or adding: (1) the total height h of the rolling process (or other distances for a non-vertical system); (2) the mass flow rate m of the glass melt delivered to the rolling process; (3) the heat and mass distribution of the glass melt delivered to the rolling process; (4) the number of rolling stages (i.e., the number of roller pairs); (5) the horizontal alignment / offset Δx of the rolling stages; (6) the heat loss q between the rolling stages; and (7) the inner radius r and the outer radius r of each roller i and the outer radius r o .

[0067] In various examples of the above method, the method may include determining the unit heat extraction in a single rolling stage configuration and comparing the unit heat extraction with the required unit heat extraction. If it is below the requirement, the method may include determining the cumulative unit heat extraction of the first and second stages in a two-stage rolling configuration and comparing the cumulative unit heat extraction with the required unit heat extraction. If it is below the requirement, the method may include determining the cumulative unit heat extraction of the first, second, and third stages in a three-stage rolling configuration and comparing the cumulative unit heat extraction with the required unit heat extraction. These steps may continue through successive calculations until the calculated unit rolling heat extraction meets or exceeds the required unit heat extraction. These steps may be used to determine the rolling configuration (number of stages and geometry of the stages) for a glass composition or application.

[0068] The unit heat extraction rate requirement may also be determined. The unit heat extraction rate may be determined by dividing the total heat extraction by the width of the ribbon formed. If the heat extraction rate matches (is approximately equal to) the total heat extraction requirement, it may be determined that the scale of the rolling process is large enough. The unit heat extraction rate in the rolling process may depend on the glass temperature, the roll temperature, the contact heat transfer coefficient between the glass and the roll, and the contact length between the glass and the roll. The contact heat transfer coefficient is a parameter that encompasses the effectiveness of the contact between the glass and the roll and varies with the contact pressure, roll roughness, and glass viscosity.

[0069] These steps may be used in combination with various inputs such as the glass flow rate, the minimum glass delivery temperature (based on liquidus limitations), and the target exit temperature to determine the required configuration of the rolling process in a glass production apparatus.

[0070] The above method has been used and an improved glass production apparatus has been tested to demonstrate the feasibility of the improved glass production apparatus for low-viscosity glass melts. As Figure 4As shown, graph 402 shows the ability of the apparatus and method of the present disclosure. Using an apparatus similar to the apparatus described in the present disclosure, the ability to produce a glass ribbon from a low-viscosity glass melt has been achieved. In one example, it has been demonstrated that using a common glass production apparatus (modified by one or more of the above) can produce a satisfactory glass ribbon from both high-viscosity and low-viscosity glass melts. The high-viscosity boundary line 402 shows the relationship between the glass ribbon thickness and the flow rate for producing glass ribbons (of various compositions) from a high-viscosity glass melt. The boundary line 402 generally shows that for a high-viscosity glass melt, a single-stage rolling station (1S) can be used as opposed to a two-stage rolling station (2S). It can be seen that for a low-viscosity glass melt, the boundary line moves down to boundary line 404. Generally, for similar thicknesses, a low-viscosity (LV) glass melt requires a two-stage rolling station (2S) with a lower flow rate than a high-viscosity glass melt.

[0071] The initial tests shown in graph 402 have demonstrated that satisfactory glass ribbons can be produced using a low-viscosity (LV) glass melt in the range of about 260 to about 500 poise at flow rates in the range of about 950 pounds per hour to about 1300 pounds per hour. Such satisfactory glass ribbons are produced using a single-stage rolling station (1S) and a two-stage (2S) rolling station, and the glass ribbons have a ribbon thickness in the range of about 0.7 mm to about 4.0 mm and a ribbon width in the range of about 249 mm to about 305 mm.

[0072] Further tests were performed on the method and apparatus of the present disclosure to obtain further robustness achievements and to allow further improvement of the above-mentioned range of low-viscosity glass melts. As Figure 5 shown, the method and apparatus of the present disclosure are used to achieve an improved process window to allow the production of satisfactory glass ribbons from similar production systems using high-viscosity and low-viscosity glass melts by modifying aspects of the above rolling process. Figure 5 Including graph 500, which shows a process window for an exemplary embodiment of a 3.0 mm glass ribbon. Graph 500 shows the tests performed plotting the delivery viscosity versus the flow rate. In this graph, the boundaries 506, 508, 510 show the boundaries of the production processes using single-stage, two-stage, and three-stage rolling processes, respectively. The high-viscosity boundary 502 and the low-viscosity boundary 504 show similar relationships as discussed above.

[0073] As Figure 5 shown, tests performed using the method and apparatus of the present disclosure have shown that increasing the number of rolling stages can improve the flow rate of a low-viscosity glass melt. For example, to produce a 3.0 mm glass ribbon, compared to a two-stage rolling process, when using a three-stage rolling process, the flow rate of a low-viscosity glass melt with a delivery viscosity below 400 poise can be increased by about 200 pounds per hour.

[0074] Now referring to Figure 6 , another graph 600 is shown. Graph 600 shows the roll forming process window for a 3.0 mm glass ribbon conveyed in the form of a low viscosity glass melt, where the conveyance viscosity is equal to or less than about 400 poise. Graph 600 plots the test results for the same low viscosity glass melt conveyed to single-stage, two-stage, and three-stage rolling processes. As shown, increasing the number of rolling stages allows the production of low viscosity glass melt at an increased mass flow rate, thus allowing improved throughput compared to existing processes.

[0075] Although not shown, other tests have successfully demonstrated the ability to implement the methods and apparatuses of the present disclosure to produce glass ribbons from low viscosity glass melts within the above ranges.

[0076] Now referring to Figure 7 , another example apparatus 700 is shown. Apparatus 700 can be used to produce a glass ribbon 722 from a low viscosity glass melt 720. The glass melt 720 can be conveyed from a downcomer 702. The downcomer 702 can be aligned with a gap 740 located between a first roll 704 and a second roll 706. The glass can then travel to a second rolling station. As shown, the gap 742 at the second rolling station can be offset a horizontal distance x from the first gap 740.

[0077] In this example, the outer diameters of the first roll 704 and the second roll 706 can be greater than the outer diameters of the third roll 708 and the fourth roll 710. In one example, the outer diameters of the first roll 704 and the second roll 706 are in the range of about 20% to about 40% greater than the outer diameters of the third roll 708 and the fourth roll 710. In other examples, the first pair of rolls and the second pair of rolls can have other relative size designs. The larger rolls in the first rolling stage allow increased relative heat extraction due to the increased surface area and the increased contact pressure of the glass with the rolls. The offset between the first pair of rolls and the second pair of rolls allows for a greater upper and lower roll speed ratio and a narrower gap at the first stage rolls. These allow for increased heat extraction.

[0078] It has also been observed that lapping or folding of the glass ribbon may occur between the rolling stages. To improve the robustness of the process, the rolling stages can be offset as Figure 7 shown and described above. The offset of the rolling stages not only improves the extraction of thermal energy from the glass melt 720, but also reduces the likelihood of folding or lapping of the glass melt as it is conveyed to subsequent rolling stations.

[0079] Now turning to Figure 8 , an example roll 800 is shown. Roll 800 can be used in one or more of the apparatuses described above. After the low viscosity glass melt is conveyed to the glass rolling process, roll 800 can be used in the rolling station. In the figure above, the roll is shown in an end view. InFigure 8 shows a front view of the width of the roller or roller 800. The glass melt can be conveyed to the roller 800 in the direction indicated by the arrow in Figure 8 . The glass melt can contact the outer surface 802 of the roller 800. In order to control or adjust the heat energy extracted from the glass melt, the outer diameter Do and / or the inner diameter Di of the roller 800 can be changed. The outer diameter Do and / or the inner diameter Di of the roller can also be varied to allow for a stable interaction between the glass and the roller surface. As Figure 8 shown, the inner diameter can vary across the entire width of the roller 800, as shown by the gradually decreasing inner diameter 808. It is not necessary to have a constant inner diameter Di as shown by the inner diameter 810, and the inner diameter can be tapered. In one example, the inner diameter Di can decrease towards the ends and increase towards the middle. In other additional examples, the surface texture of the outer surface 802 can be modified or customized to achieve the desired heat exchange and / or reduce the likelihood of quality issues or defects.

[0080] In some embodiments, a method 900 for producing a glass ribbon is provided. The method 900 can be performed using one or more of the devices and systems described in the present disclosure (such as devices 300, 700). The method 900 can also be performed by other systems or devices and / or variants of the devices described herein. For illustrative purposes, the method 900 is described with reference to the device 300, but it should be understood that the method 900 is not limited to this device.

[0081] The method 900 begins at step 902. In step 902, the glass melt is conveyed to a first pair of rollers. In the device 300, the downcomer 302 can convey the glass melt to the first pair of rollers, including the first roller 306 and the second roller 308. The glass melt can be a low-viscosity glass melt having a viscosity within the above-described range. In one example, the viscosity of the glass melt can be less than about 500 poise.

[0082] The method 900 can continue to step 904. In step 904, the glass melt can be rolled in a first gap 342 between the first roller 306 and the second roller 308. The geometry and function of the rollers can be selected such that when the glass melt is formed and cooled by the first roller 306 and the second roller 308, the rollers remove a predetermined amount of heat energy from the glass melt at the first pair of rollers.

[0083] Method 900 can proceed to step 906. In step 906, the glass melt can 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 can be separated to define the second gap 344. In some embodiments, the second gap 344 is horizontally offset from the first gap 342. In such a configuration, the glass melt can be delivered to the outer surface of the fourth roller 312 at a location spaced apart from or remote from the second gap 344. As the glass melt stays on the outer surface and moves towards the second gap 344, the glass melt is cooled. The geometries and functions of the third roller 310 and the fourth roller 312 can be selected such that the rollers remove a predetermined amount of thermal energy from the glass melt as the glass melt moves downstream in the process.

[0084] Method 900 can proceed to step 908. In step 908, the glass melt can 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 can be separated to define the third gap 346. In some embodiments, the third gap 346 can 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 can be offset from each other, and no gap is vertically aligned.

[0085] After step 908, method 900 can end. Although not shown, method 900 can continue and can include additional functions to continue forming the glass ribbon and separating the glass sheets from the glass ribbon, as referenced Figure 1 as described.

[0086] It will be understood that, in some embodiments, the steps of method 900 are optional. In some examples, method 900 can include a single rolling stage. In other examples, method 900 can include two rolling stages. In still other examples, the method can include a third rolling stage or other numbers of rolling stages.

[0087] The methods and systems described herein may be embodied, at least in part, in the form of a computer-implemented process and an apparatus for practicing these processes. The disclosed methods may also be embodied, at least in part, in the form of a tangible, non-transitory machine-readable storage medium encoded with computer program code. The medium may include, for example, RAM, ROM, CD-ROM, DVD-ROM, BD-ROM, hard disk drive, flash memory, or any other non-transitory machine-readable storage medium, or any combination of these media, wherein when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the methods. The methods may also be embodied, at least in part, in the form of a computer in which the computer 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. Alternatively, the methods may be embodied, at least in part, in a digital signal processor formed by an application specific integrated circuit for performing the methods.

[0088] Although the subject matter has been described in accordance with exemplary embodiments, the subject matter is not limited thereto. Instead, the appended claims should be construed broadly to include other variations and embodiments that may be made by those skilled in the art.

Claims

1. A method for producing a glass ribbon, the method comprising: conveying the molten glass to a first pair of rollers; rolling the glass melt between the first pair of rollers in a first gap; as well as The glass melt is rolled in a second gap between a second pair of rollers, wherein the second gap is offset from and downstream of the first gap.

2. The method of claim 1, wherein the glass melt has a viscosity of less than about 500 poise. The method of claim 1 , wherein the second gap is offset from the first gap in a horizontal direction.

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

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

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

7. The method of claim 6, wherein the molten glass 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 downstream of 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 the outer diameter of the third pair of rollers is different from the outer diameters of the first pair of rollers and the second pair of rollers.

11. A device, comprising: a downcomer configured to deliver a low viscosity glass melt to produce a glass ribbon; as well as At least one pair of rollers is vertically positioned 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 including 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 the outer diameters of the first roller and the second roller are different from the outer diameters of the third roller and the fourth roller.

16. The apparatus of claim 13, wherein the inner diameters of the first roller and the second roller are different from the inner diameters 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 fishtailing. 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 horizontally spaced apart from the first gap.

19. The apparatus of claim 11, further comprising one or more air scoops or air vanes downstream of the downcomer, the one or more air scoops or air vanes 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 including fifth and sixth rollers spaced apart from each other to form a third gap, the third gap being horizontally offset from the second gap.

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