Glass ribbon processing method and device therefor

Abstract

A method and apparatus for forming and processing a glass ribbon. The apparatus includes a processing roller and an edge roller that contacts an edge portion of a glass layer disposed on the processing roller. The edge roller cools the edge portion of the glass layer, the cooled edge portion achieving an increased viscosity compared to a central portion of the glass layer. An embodiment can include a second edge roller that contacts and cools an opposing edge portion of the glass layer. The cooled edge portion can resist shrinkage across the width of the glass layer and the glass ribbon formed therefrom.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 63 / 246,979, filed September 22, 2021, the entire disclosure of which is incorporated herein by reference.

[0002] (Technical field) The present disclosure relates to a method for treating a glass ribbon, and more particularly to a method for reducing shrinkage of the glass ribbon across the width of the ribbon. An apparatus for carrying out the method is also disclosed. [Background technology]

[0003] It is known to process a stream of molten glass by flowing the molten glass onto a process roller over at least a portion of the circumference of the process roller while a layer of molten glass on the process roller is cooled by and ejected therefrom. The layer of molten glass can be drawn off the process roller by a drawing roller disposed below the process roller, which applies a downward tension to the molten glass to produce a ribbon of glass of a desired thickness. As the layer of molten glass cools on and below the process roller, the layer of molten glass and the glass ribbon can shrink in the width direction of the glass, reducing the overall width of the glass ribbon and thereby reducing the usable width of the glass ribbon. Summary of the Invention [Means for solving the problem]

[0004] FIG. 1 is a schematic diagram of a glass forming apparatus in which a stream of molten glass 10 is provided from a vessel 12 configured to deliver the molten glass to process rollers 14. The stream of molten glass emerges from the process rollers and is drawn downwardly by a pair of counter-rotating drawing rolls 16. As the molten glass layer in contact with the process rollers cools, contraction forces (e.g., surface tension) may cause peripheral portions 18, 22 on opposite sides of the glass flow path to taper inward, as indicated by arrows 24, increasing the thickness of the peripheral portions 18, 22 and reducing the overall width of the molten glass layer. Such shrinkage may continue until the temperature of the glass ribbon is low enough (the edges of the ribbon are sufficiently hard) that no further shrinkage can occur. The thickened peripheral portions of the glass ribbon are unsalable and must be removed, thereby further reducing the usable width 26 of the glass ribbon and the glass sheet removed therefrom.

[0005] Thus, a method of forming a glass ribbon with minimal width shrinkage is disclosed, the method including: casting a stream of molten glass on an outer peripheral surface of a process roller rotating in a first rotational direction about a first axis of rotation, the stream of molten glass forming a molten glass layer on the outer peripheral surface of the process roller; contacting an edge portion of the molten glass layer on the process roller with a first edge roller rotating in a second rotational direction opposite the first rotational direction about a second axis of rotation, the contact cooling the edge portion and increasing its viscosity, and the molten glass layer being ejected from the process roller as a molten glass ribbon. The first edge roller does not contact a central portion of the molten glass layer. The stream of molten glass can, for example, flow out of a forming body. In some embodiments, the forming body can include a slot through which the stream of molten glass is ejected. In other embodiments, the forming body can include a forming wedge, the forming wedge including a trough on a top surface of the forming body and a pair of angled forming surfaces converging along a bottom edge of the forming wedge. The molten glass overflows the trough and flows down along converging forming surfaces where it meets at the lower end to form a glass stream.

[0006] The method further includes drawing the molten glass ribbon from the process roller in a drawing direction between a pair of drawing rolls, the drawing rolls engaging an edge portion on an opposite side of the glass ribbon below the process roller. In various embodiments, the method can further include contacting the edge portion with a pair of edge rollers disposed between the process roller and the pair of drawing rolls, the pair of edge rollers further cooling the edge portion.

[0007] The surface of the first edge roller may be cooled by a flow of a cooling fluid within the interior of the first edge roller.

[0008] The method may further include cooling the processing roller by contacting an inner surface of the first edge roller with a cooling fluid.

[0009] The diameter of the treatment roller can range from about 5 cm to about 31 cm. The length of the treatment roller can range from about 25 cm to about 400 cm.

[0010] The diameter of the first edge roller can range from about 2.5 cm to about 8 cm. The length of the first edge roller can range from about 1 cm to about 26 cm.

[0011] The processing roller includes an apex defined at an angular position of 0 degrees. The first edge roller can contact an edge portion on the processing roller at an angular position ranging from about 35 degrees to about 90 degrees defined in the direction of rotation of the processing roller relative to the 0 degree position.

[0012] The first edge roller may be movable along a second axis of rotation.

[0013] The molten glass layer can include a first viscosity at a first point on the edge portion and a second viscosity at a center point of the molten glass layer on a horizontal line extending perpendicular to the drawing direction, and a viscosity ratio defined as the ratio of the viscosity of the molten glass layer at the first point to the viscosity of the glass layer at the center point can be in the range of about 1 to about 100, such as in the range of about 1 to about 30, such as in the range of about 1 to about 16, such as in the range of about 5 to about 15.

[0014] Also disclosed is a method of forming a glass ribbon, the method including: casting a stream of molten glass onto an outer peripheral surface of a process roller rotated by a first motor in a first rotational direction about a first axis of rotation, the stream of molten glass forming a molten glass layer on the outer peripheral surface of the process roller; contacting a peripheral portion of the molten glass layer on the process roller with a first edge roller rotated by a second motor in a second rotational direction opposite the first rotational direction about a second axis of rotation, the contact cooling the peripheral portion and increasing its viscosity, the molten glass layer having a first viscosity at a first point on the peripheral portion and a second viscosity at a center point of the molten glass layer on a horizontal line extending perpendicular to the drawing direction, a viscosity ratio defined as the ratio of the viscosity of the molten glass layer at the first point to the viscosity of the glass layer at the center point is in the range of about 1 to about 16, and the molten glass layer being discharged from the process roller as a molten glass ribbon. The method further includes drawing the molten glass ribbon from the process rollers in a drawing direction between a pair of draw-in rollers, the draw-in rolls engaging edge portions on opposite sides of the glass ribbon below the process rollers, the first edge roller not contacting a central portion of the molten glass layer.

[0015] The treatment rollers can span the full width of the molten glass layer in a direction perpendicular to the withdrawal direction.

[0016] The viscosity of the molten glass flow at the treatment roller is about 10 9.9 About 10 from Poise 11.2 It can be in the poise range.

[0017] Both the foregoing general description and the following detailed description illustrate embodiments that are intended to provide an overview or framework for understanding the nature and character of the embodiments disclosed herein. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the present disclosure and, together with the description, explain the principles and operation thereof. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is an elevational view of an exemplary molten glass processing apparatus. [Diagram 2] FIG. 1 is a schematic diagram of an exemplary glass manufacturing apparatus according to an embodiment of the present disclosure. [Diagram 3] 3 is an elevation view of an exemplary molten glass forming and processing apparatus according to an embodiment of the present disclosure, where processing rollers are fed with a flow of molten glass from a slotted former usable with the glass manufacturing apparatus of FIG. [Figure 4] FIG. 3 is an elevation view of an exemplary molten glass forming and processing apparatus according to an embodiment of the present disclosure, where processing rollers are fed with a stream of molten glass from a former with a converging forming surface usable with the glass manufacturing apparatus of FIG. [Diagram 5] FIG. 1 is a front view of an exemplary molten glass processing apparatus. [Figure 6] 1 is a cross-sectional view of an exemplary edge roller. [Figure 7] 1 is a schematic diagram of an exemplary process roller illustrating the position of an edge roller configured to contact an edge portion of a molten glass layer disposed on the process roller. [Figure 8] 2 is a schematic diagram of a portion of an edge section showing an edge roller movable along its axis of rotation; [Figure 9] 1 is a graph illustrating modeling results showing ribbon width in millimeters as a function of viscosity from edge to center for five different glass ribbon center viscosities. [Figure 10] 1 is a chart showing glass ribbon width as a function of viscosity from the edge to the center of the glass ribbon. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings to refer to the same or like elements. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0020] As used herein, the term "about" means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not, and need not be, exact, but may be approximate and / or larger or smaller, as desired, to reflect tolerances, conversion factors, rounding, measurement errors, and the like, as well as other factors known to those of ordinary skill in the art.

[0021] Ranges can be expressed herein as from "about" one particular value, and / or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value to the other particular value. Similarly, when values ​​are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will further be understood that the endpoints of each of the ranges are significant in relation to the other endpoint, and independently of the other endpoint.

[0022] Directional terms used herein, e.g., upper, lower, right, left, front, rear, above, below, are given only with reference to the illustrated figures and are not intended to imply absolute directions.

[0023] Unless otherwise indicated, the methods described herein are not intended to be construed as requiring that its steps be performed in a particular order, or that it require a particular orientation of any apparatus. Thus, where a method claim does not actually recite an order in which its steps should be followed, or where any apparatus claim does not actually recite an order or orientation for individual components, or where the steps are not specifically recited in the claim or specification otherwise to be limited to a particular order, or where no particular order or orientation for the components of the apparatus is recited, no order or orientation is intended to be inferred in any respect. This applies to all possible non-expressive bases for interpretation, including logical considerations regarding the arrangement of steps, operational flow, order of components, or orientation of components, general meaning derived from grammatical construction or punctuation, and the number or type of embodiments described in the specification.

[0024] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to an "a" component includes aspects having two or more such components unless the context clearly dictates otherwise.

[0025] As used herein, the words "exemplary," "example," or various forms thereof, are used to mean serving as an example, instance, or illustration. Any aspect or design described herein as "exemplary" or "example" is not to be construed as preferred or advantageous over other aspects or designs. Moreover, the examples are provided only for purposes of clarity and understanding and are not intended to limit or restrict in any way the disclosed subject matter or relevant portions of this disclosure. It should be understood that numerous additional or alternative examples of varying scope may be presented, but have been omitted for purposes of brevity.

[0026] As used herein, the terms "comprising" and "including," and variations thereof, unless otherwise indicated, are intended to be synonymous and open ended. A list of elements following the transitional phrase "comprising" or "including" is a non-exclusive list, such that there may be elements in addition to the elements specifically stated in the list.

[0027] As used herein, the terms "substantial," "substantially," and variations thereof are intended to note that a described feature is equal or nearly equal to a value or description. For example, a "substantially planar" surface is intended to indicate a surface that is planar or nearly planar. Furthermore, "substantially" is intended to indicate that two values ​​are equal or nearly equal. In some embodiments, "substantially" can refer to values ​​that are within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0028] Hereinafter, as used herein, a distinction is made between a stream of molten glass (e.g., a stream or glass stream), a layer of molten glass (e.g., a glass layer), and a glass ribbon (e.g., a ribbon of glass). As used herein, a stream of molten glass refers to a stream of molten glass from a forming body before contacting a downstream processing roller. The forming body can be the discharge end of a conduit or pipe, e.g., a narrow discharge slot in a refractory or metal body, or a fused forming body in which the molten glass overflows a trough in the forming body and descends as a stream from the lower end of the forming body. For the purposes of discussion, the molten glass will be referred to as a molten glass layer while in contact with the processing roller, but as a glass ribbon after it has left the surface of the processing roller. Thus, for the purposes of explanation, a distinction is made between three stages of molten glass: after discharge from the forming body (glass stream, glass stream, molten glass stream, etc.), during contact with the processing roller (glass layer), and after it has left the processing roller (glass ribbon).

[0029] As used herein, unless otherwise indicated, the terms "molten glass," "glass," and glass stream, glass layer, and glass ribbon refer to a non-elastic, viscous material that can be cooled to form an amorphous, elastic, glassy material, e.g., an inorganic glass material, such as a silicate glass.

[0030] The method disclosed herein for producing a sheet of glass having two opposing major faces, at least one of which exhibits high surface quality, using a roller surface to treat the glass is particularly well suited for such production of glasses having low liquidus viscosities, such as, but not limited to, glasses having a liquidus viscosity of less than about 20,000 Pa·s. As used herein, the term "liquidus viscosity" refers to the viscosity of molten glass at its liquidus temperature, which refers to the temperature at which crystals first appear as the molten glass cools from its melting temperature or at which the last crystals melt as the temperature increases from room temperature. Unless otherwise indicated, the liquidus viscosity values ​​disclosed herein are determined in the following manner, unless otherwise indicated. First, the liquidus temperature of the glass is measured in accordance with ASTM C829-81 (2015), entitled "Standard Practice for Measurement of Liquidus Temperature of Glass by the Gradient Furnace Method". The viscosity of the glass at the liquidus temperature is then measured in accordance with ASTM C965-96 (2012), entitled "Standard Practice for Measuring Viscosity of Glass Above the Softening Point."

[0031] The methods disclosed herein may include the steps of: delivering a flow of molten glass onto a processing device (e.g., processing rollers) as molten glass; processing the molten glass layer with a processing device suitable for temporarily supporting the weight of the molten glass layer and entraining it in its falling movement while increasing its viscosity and maintaining at least a central portion of one of its two major surfaces out of contact with a surface of the processing device; controlling the speed of travel of the glass ribbon discharged from the processing device, as well as the width and / or thickness of the glass ribbon, using a suitable device or mechanism acting on the glass ribbon; and cooling the glass ribbon.

[0032] The molten glass stream can be produced without any contact after it leaves the forming body and can be rapidly captured before mechanical instability of the glass stream and a significant increase in its viscosity occurs. Such instability can take the form of changes in the width of the molten glass stream, lateral "walking" of the stream, separation of the stream into separate distinct portions, etc. The stream can be controlled and cooled to obtain a glass ribbon that, at least in its central portion, does not have one of its major faces in contact with any surface.

[0033] The flow of the molten glass may be controlled by a viscosity measured in accordance with ASTM C829-81(2015), i.e., in the range of about 5 Pa·s to about 5,000 Pa·s (about 50 poise to about 50,000 poise), e.g., about 5, 7, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 109, It can be delivered to the treatment roller at a viscosity of 15, 20, 40, 50, 80, 100, 200, 400, 700, 1,000, 1,500, 2,000, 2,500, 3,000, 3,500, 4,000, 4,500, or 5,000 Pa·s, for example in the range of about 10 Pa·s to about 1,000 P·s (100 poise to 10,000 poise), for example 10, 15, 20, 40, 50, 80, 100, 200, 400, 700, or 1,000 Pa·s.

[0034] The molten glass stream can have both major surfaces that do not contact any surface between the outlet from the delivery device and the processing device. When delivered in this manner, the molten glass stream falls under gravity. The height to which the molten glass stream falls is limited because it must be captured before it becomes unstable. The allowable drop height of the glass stream between the outlet of the delivery device and the processing device depends on the glass composition of interest and its dimensions. In general, the drop height does not exceed 150 millimeters (mm). For example, the drop height can be less than 60 mm. Given a particular glass composition and dimensions, one skilled in the art can optimize the drop height to, for example, deliver the molten glass. In an exemplary embodiment, the maximum drop height can be about 10 mm for a molten glass having a viscosity of about 100 Pa·s, and the thickness of the delivered stream is about 3 mm.

[0035] According to embodiments disclosed herein, the method can include processing the delivered stream of molten glass. Before the molten glass begins to become unstable, the stream of molten glass can be taken up by the processing equipment under conditions that do not themselves cause destabilization, which ensures that a central portion of one of the major faces of the glass does not come into contact with any surface. This major face can remain free or substantially free of contact with other materials. If any contact does occur, the contact can be limited to an edge portion of the stream. The glass can be processed to be more viscous at the end of processing than when the molten glass was delivered upstream, resulting in a stabilized stream.

[0036] The treatment of the delivered molten glass stream includes receiving the delivered stream as a molten glass layer on the surface of a treatment roller, which rotates in a suitable direction and at a suitable speed to present a suitable surface temperature and to accompany the movement of the molten glass layer without relative movement of the molten glass layer with respect to the surface of the treatment roller. The minimum allowable rotational speed of the treatment roller can be determined at least in part by the density of the glass stream and the distance between the exit point of the delivered molten glass stream from the forming body and the top dead center (TDC) of the treatment roller. For example, the minimum allowable rotational speed of the treatment roller can be a rotational speed at the treatment roller surface that results in a linear withdrawal speed of the glass ribbon drawn therefrom of about 0.4 centimeters per minute (cm / min). The upper withdrawal speed limit can be 250 cm / min or more, or until the flow of molten glass between the root and the treatment roller becomes unstable.

[0037] The surface temperature of the treatment roller can range from about 200° C. to about 800° C. and can vary depending on the thermal environment of the treatment roller and the temperature of the molten glass layer. The treatment roller can be associated with a device or mechanism for controlling the surface temperature of the treatment roller and therefore the temperature of the molten glass layer contacting it. The treatment roller can be appropriately positioned and driven to ensure contact with the molten glass layer and sufficient cooling of the molten glass layer to obtain a desired viscosity increase, and contact between the molten glass layer and the treatment roller can be maintained without relative movement between the molten glass layer and the treatment roller over a significant percentage of the circumference of the treatment roller.

[0038] The treated glass layer can be maintained such that at least a central portion of one major surface of the layer is free from contact with other surfaces, such as edge rollers and / or pull-off rollers.

[0039] When the glass stream contacts a roller, such as a processing roller, adhesive forces may develop between the glass and the roller. The nature and magnitude of such adhesive forces may vary depending on the composition of the particular glass and roller in conjunction with factors such as the surface texture of the roller material, the contact pressure of the glass layer on the roller surface, the contact time, and the temperature of the molten glass and the roller. Adhesion may result from van der Waals type interactions at the interface between the glass and the roller. If the adhesive forces are too high, the contacted glass cannot be separated or cannot be separated without damaging either the glass and / or the roller. If the adhesive forces are too low, the glass will slip against the roller surface, resulting in inconsistent glass thickness and / or damage to the glass.

[0040] The adhesive force between the roller and the molten glass layer can be utilized to compensate for the natural downward gravity on the molten glass layer during production. The adhesive force between the molten glass layer and the roller can include one or more individual forces acting together. For example, in addition to adhesion of the molten glass layer to the roller surface, orthogonal and / or tangential forces can act on the molten glass layer in the attachment direction. The adhesive force per unit area can be determined by one skilled in the art and then utilized to determine the maximum orthogonal and / or tangential force that the glass layer can undergo without causing separation of the molten glass layer from the roller. For example, the determination of the tangential force can be performed when the static friction coefficient between the glass layer and the roller surface is known.

[0041] A relationship exists between the viscosity of the molten glass layer contacting the roller and the adhesion that may exist between the molten glass layer and the roller after contact. Therefore, it may be desirable to control the adhesion between the molten glass layer and the roller by controlling the interfacial temperature between the molten glass layer and the roller.

[0042] The viscosity of the molten glass layer contacting a roller, such as a processing roller, may vary depending on the glass composition and the process employed in a particular roller design. Although not intended to be limiting, the viscosity of the molten glass layer contacting a roller is generally about 10 8 From Pa·s to about 10 10 Pa s range, e.g., about 1×10 8 , 5×10 8 , 1×10 9 , 5×10 9 , or 1 × 10 10 It can be made into Pa s. About 10 8 A glass layer having a viscosity of less than about 10 Pa·s may exhibit irreversible sticking between the molten glass layer and the roller. 9 Glass layers with viscosities of around 10 Pa·s may exhibit moderate adhesion. 10 A molten glass layer having a viscosity greater than Pa·s may exhibit no or substantially no adhesion between the molten glass layer and the roller.

[0043] The interface temperature, and therefore adhesion, between the molten glass layer and the roller can be controlled during the manufacturing process. Certain glass manufacturing systems, particularly rollers such as processing rollers, can utilize any suitable method for controlling the surface temperature of the roller, and therefore the interface temperature, and the viscosity of the resulting glass layer, including any one or more of the methods described herein, in various embodiments. The roller can include at least one flow passage through which a cooling fluid, such as air and / or water, can flow. Optionally, the roller can utilize other devices and / or mechanisms to control the surface temperature in addition to or in place of the cooling passage. For example, the roller can be hollow, so that air and / or water can be flowed, sprayed, or applied to the inner walls of the roller. At least one array of external cooling nozzles can be used to control or partially control the surface temperature of the roller. Thermal control of the roller surface temperature can occur by radiation, convection, and / or heat conduction for at least a portion of the roller that is not in contact with the molten glass layer.

[0044] Thus, the treatment step is performed such that the molten glass layer in contact with the treatment roller is heated to about 10° C. on the surface of the treatment roller to obtain a reversible adhesive force between the treatment roller and the molten glass layer. 8.9 From Pa·s to about 10 10.2 It may include adjusting and controlling the temperature of the roller, e.g., the treatment roller, before and / or during contact with the molten glass layer so that it has a viscosity in the range of Pa·s. The adhesion should be reversible over a period extending from the position where the molten glass stream first contacts the treatment roller to the moment when the glass layer leaves the contact of the treatment roller as a glass ribbon. The treatment or treatment step may optionally further include maintaining and / or reheating the contacted glass sufficiently to achieve a subsequent redraw (thinning) of the glass. The viscosity of the molten glass layer on the surface of the treatment roller may first be determined by determining the curve of viscosity as a function of temperature for the particular glass composition used. The temperature of the molten glass layer on the treatment roller may then be measured, e.g., using an optical pyrometer, and the viscosity of the molten glass may be calculated based on the previously determined viscosity vs. temperature curve.

[0045] In order to efficiently stabilize glasses with low liquidus viscosity, the drawing force acting between the roller and the molten glass layer in contact with the roller can be modified using various techniques. In a first embodiment, the surface area of ​​the interface between the roller and the molten glass layer in contact with the roller can be modified to allow for cooling adjustment. Thus, the surface of the roller can be roughened to have an average roughness (Ra) in the range of 0 to about 25 micrometers determined using a profilometer, the average roughness being the arithmetic mean value of the filtered roughness profile determined from the deviation about the centerline within the evaluation length. In a second embodiment, the glass can be fed to different positions on the roller and / or from different directions. In a third embodiment, the drawing force can be applied in different directions. For example, a draw-in roller and / or an edge roller can be used to prevent lateral contraction (thinning) of the glass ribbon as the molten glass layer leaves the processing roller. Each of these embodiments can be used separately or in any combination.

[0046] 2 illustrates an exemplary glass manufacturing apparatus 100. The glass manufacturing apparatus 100 comprises a glass melting furnace 102 that includes a melting vessel 104. In addition to the melting vessel 104, the glass melting furnace 102 can optionally include one or more additional components, such as heating elements (e.g., combustion burners and / or electrodes) configured to heat the raw materials and transform the raw materials into molten glass.

[0047] The glass melting furnace 102 may include other thermal management devices (e.g., insulation elements) that reduce heat loss from the melting vessel. The glass melting furnace 102 may include electronic and / or electromechanical devices that facilitate melting of the raw materials into a glass melt. The glass melting furnace 102 may include a support structure (e.g., a support chassis, support members, etc.) or other components.

[0048] The melting vessel 104 can be formed from a refractory ceramic material, such as a refractory ceramic material composed of alumina or zirconia, although the refractory ceramic material can be composed of other refractory materials, such as yttrium (e.g., yttria, yttria stabilized zirconia, yttrium phosphate), zircon (ZrSiO4) or alumina-zirconia-silica, or chromium oxide, either alternatively or in any combination. In some implementations, the melting vessel 104 can be constructed from refractory ceramic bricks.

[0049] The glass melting furnace 102 can be incorporated as a component of a glass manufacturing apparatus configured to produce glass articles, such as glass ribbons. However, the glass manufacturing apparatus can be configured to form other glass articles, such as glass rods, glass tubes, glass envelopes (e.g., glass envelopes for lighting devices, such as light bulbs), and glass lenses, although many other glass articles are contemplated. The melting furnace can be included in a glass manufacturing apparatus that includes a slot draw apparatus, a float bath apparatus, a downdraw apparatus (e.g., a fusion downdraw apparatus), an updraw apparatus, a press apparatus, a tube drawing apparatus, or any other glass manufacturing apparatus that would benefit from the present disclosure.

[0050] Glass manufacturing system 100 may optionally include upstream glass manufacturing equipment 106 disposed upstream of melting vessel 104. In some embodiments, some or all of the upstream glass manufacturing equipment 106 may be incorporated as part of glassmelting furnace 102.

[0051] As shown in FIG. 2 , the upstream glass manufacturing apparatus 106 can include a raw material storage bin 108, a raw material delivery device 110, and a motor 112 coupled to the raw material delivery device 110. The raw material storage bin 108 can be configured to store a predetermined amount of raw material 116 that can be fed to the melting vessel 104 of the glass melting furnace 102 through one or more feed ports, as indicated by arrow 118. Generally, the raw material 116 can include one or more glass-forming metal oxides and one or more modifiers. In some embodiments, the raw material delivery device 110 can be driven by the motor 112 to feed the predetermined amount of raw material 116 from the raw material storage bin 108 to the melting vessel 104. In further embodiments, the motor 112 can drive the raw material delivery device 110 to introduce the raw material 116 at a controlled rate based on a level of molten glass sensed downstream of the melting vessel 104 relative to a flow direction of the molten glass. The raw material 24 in the melting vessel 104 is then heated to form molten glass 120. Typically, in an initial melting step, raw material 116 is added to the melting vessel 104 as, for example, various "sand"-like particles. Raw material 116 may also include waste glass (i.e., cullet) from previous melting and / or forming operations. Typically, a combustion burner is used to initiate the melting process. In an electrically boosted melting process, once the electrical resistance of the raw material is sufficiently reduced, electrical boosting is initiated by generating an electrical potential between electrodes placed in contact with the raw material, thereby establishing an electrical current through the raw material, and typically the raw material becomes or is in a molten state. As used herein, the resulting molten material shall be referred to as molten glass 120.

[0052] The glass manufacturing system 100 may optionally include downstream glass manufacturing equipment 122 disposed downstream of the glass melting furnace 102 relative to the flow direction of the molten glass 120. In some embodiments, a portion of the downstream glass manufacturing equipment 122 may be incorporated as part of the glass melting furnace 102. However, in some instances, a first connecting conduit 124, described below, or other portions of the downstream glass manufacturing equipment 122 may be incorporated as part of the glass melting furnace 102.

[0053] The downstream glass production apparatus 122 may include a first conditioning (i.e., processing) chamber, such as a fining vessel 126, located downstream of the melting vessel 104 and connected thereto by the first connecting conduit 124 described above. In some embodiments, the molten glass 120 may be gravity fed from the melting vessel 104 to the fining vessel 126 via the first connecting conduit 124. However, it should be understood that other conditioning chambers may be located downstream of the melting vessel 104, for example, between the melting vessel 104 and the fining vessel 126. Conditioning chambers may be used between the melting vessel and the fining chamber. For example, the molten glass from the primary melting vessel may be further heated in a secondary melting (conditioning) vessel or may be cooled in the secondary melting vessel to a temperature lower than the temperature of the molten glass in the primary melting vessel before entering the fining vessel.

[0054] As discussed above, gases can be removed from the molten glass 120 by a variety of techniques. For example, the raw material 116 can include polyvalent compounds (i.e., fining agents), such as tin oxide, that undergo a chemical reduction reaction when heated to release oxygen. Other suitable fining agents can include, but are not limited to, arsenic, antimony, iron, and / or cerium, although the use of arsenic and antimony may be discouraged for environmental reasons in some applications due to their toxicity. The fining vessel 126 is heated, for example, to a temperature higher than the melting vessel internal temperature, thereby heating the fining agents. Oxygen produced by the temperature-induced chemical reduction of one or more fining agents contained in the molten glass diffuses into the gas bubbles generated during the melting process. The large buoyant, expanded gas bubbles then rise to the free surface of the molten glass in the fining vessel and are expelled from the fining vessel.

[0055] The downstream glass production apparatus 122 may further include a mixing device 130, e.g., another conditioning chamber such as a stirred vessel, for mixing the molten glass flowing downstream from the fining vessel 126. The mixing device 130 may be used to provide a homogenous glass melt composition, thereby reducing chemical or thermal inhomogeneities that may otherwise be present in the molten glass exiting the fining vessel. As shown, the fining vessel 126 may be connected to the mixing device 130 by a second connecting conduit 132. In some embodiments, the molten glass 120 may be gravity fed from the fining vessel 126 to the mixing device 130 by the second connecting conduit 132. Typically, the molten glass in the mixing device 130 includes a free surface, with a free (e.g., gas) volume extending between the free surface and the top of the mixing device. Although the mixing device 130 is shown downstream of the fining vessel 126 with respect to the flow direction of the molten glass, the mixing device 130 may also be located upstream of the fining vessel 126. In some embodiments, the downstream glass manufacturing equipment 122 can include multiple mixing devices, for example, a mixing device upstream from the fining vessel 126 and a mixing device downstream from the fining vessel 126. When used, the multiple mixing devices can be of the same design or can be of different designs from one another. In some embodiments, one or more of the vessels and / or conduits can include static mixing vanes disposed therein to promote mixing and subsequent homogenization of the molten materials.

[0056] The downstream glass manufacturing apparatus 122 may further include another conditioning chamber, such as a delivery vessel 134 located downstream of the mixing apparatus 130. The delivery vessel 134 may condition the molten glass 120 that is fed to the downstream forming apparatus. For example, the delivery vessel 134 may function as an accumulator and / or flow controller to condition a consistent flow of the molten glass 120 and / or feed the downstream forming processing apparatus 142 via a delivery conduit 140. In some embodiments, the molten glass in the delivery vessel 134 may include a free surface, with a free volume extending upward from the free surface to the top of the delivery vessel. As shown, the mixing apparatus 130 may be connected to the delivery vessel 134 by a third connecting conduit 136.

[0057] As will be described, the downstream glass manufacturing apparatus 122 may further include a forming and processing apparatus 142, where the molten glass 120 is formed into a stream of molten glass and delivered to a processing roller. As shown in FIG. 3, the delivery conduit 140 may be positioned to deliver the molten glass 120 from the delivery vessel 134 to a forming body 143 forming part of the forming and processing apparatus 142. In some embodiments as shown in FIG. 3, the forming body 143 may be a slot draw apparatus, where the forming body comprises a vessel including a slot along its bottom surface, and where the molten glass flows out of the vessel. Thus, the forming body 143 delivers a stream of molten glass 144 from the slot to the processing roller 146, where the stream of molten glass 144 is deposited on the circumferential (outer) surface 148 of the processing roller as a glass layer 150. The processing roller 146 may be a metal roller formed from a corrosion resistant metal, such as a stainless steel roller, although the processing roller 146 may be formed from other suitable metals. In various embodiments, the treatment roller 146 may be hollow and may be supplied with a cooling fluid, such as air or water. For example, the treatment roller 146 may include one or more internal passages configured to carry the cooling fluid through the treatment roller, and / or the cooling fluid may be sprayed against the interior surface of the treatment roller. The stream of molten glass 144 may strike the treatment roller 146 at the 12 o'clock position (0 degrees, i.e., top dead center (TDC)) and form a glass layer 150 on the treatment roller before being discharged from the treatment roller at the 3 o'clock position (90 degrees) as a glass ribbon 152. However, the glass ribbon may be discharged from the treatment roller 146 at different angular positions, for example, ranging from about 0 degrees to about 100 degrees, depending on the adhesion of the molten glass to the treatment roller and / or the rotational speed of the treatment roller. Additionally, the stream of molten glass 144 may strike the treatment roller at positions other than the 12 o'clock position. For example, either the stream 144 or the treatment roller 146, or both, can be moved so that the stream impinges on the treatment roller in a range of positions from about 10 o'clock to about 2 o'clock (e.g., about -30 degrees to about 60 degrees relative to TDC).

[0058] The glass ribbon 152 can be separated into individual glass sheets by a downstream glass separating device (not shown). However, the glass ribbon can optionally be wound onto a spool and stored for further processing. The glass ribbon 152 can be pulled downwardly from the processing roller 146 by a plurality of counter-rotating pull-off roller assemblies 154 disposed below the processing roller 146, the pull-off roller assemblies 154 (e.g., a pair of counter-rotating pull-off rollers) contacting the glass ribbon 152 along the edge portions 156a, 156b of the glass ribbon without contacting a central portion 158 of the glass ribbon (the central portion 158 extends between the edge portions 156a, 156b) (see FIG. 5). A thickness 160 of the glass ribbon 152 along a longitudinal centerline 162 of the glass ribbon can be defined between a first major surface 164 and a second major surface 166 of the glass ribbon 152, the thickness 160 being about 4 millimeters (mm) or less, about 3 mm or less, about 2 mm or less, 1 mm or less, about 0.7 mm or less, about 0.5 mm or less, about 0.1 mm or less, about 500 micrometers (μm) or less, such as about 300 μm or less, about 200 μm or less, or about 100 μm or less, although other thicknesses are contemplated. Additionally, the glass ribbon 152 can be formed from a variety of glass compositions, including, but not limited to, soda-lime glass, borosilicate glass, aluminoborosilicate glass, alkali-containing glasses such as alkali aluminoborosilicate glass, or alkali-free glasses.

[0059] FIG. 4 illustrates another forming and processing apparatus 142 in which a delivery conduit 140 (not shown in FIG. 4) directs molten glass 120 to another forming body 143. With the forming body of FIG. 4, the forming body includes a trough 168 located on an upper surface of the forming body, which further includes converging forming surfaces 170a and 170b that converge along a bottom edge 172 of the forming body 143. The molten glass 120 overflows the walls of the trough and flows down and over the converging forming surfaces. The separate streams of molten glass meet along bottom edge 172 to form a stream of molten glass 144 that is deposited on processing roller 146 as glass layer 150. The embodiment of FIG. 4 then operates similarly to the embodiment of FIG. 3.

[0060] Components of the downstream glass manufacturing equipment 122, including any one or more of the connecting conduits 124, 132, 138, the fining vessel 126, the mixing device 130, the delivery vessel 134, the delivery conduit 140, or the forming body 143, can be formed from a precious metal. Suitable precious metals include platinum group metals selected from the group consisting of platinum, iridium, rhodium, osmium, ruthenium, and palladium, or alloys thereof. For example, the downstream components of the glass manufacturing equipment can be formed from a platinum-rhodium alloy including about 70% to about 90% platinum and about 10% to about 30% rhodium by weight. However, other suitable metals for forming the downstream components of the glass manufacturing equipment can include molybdenum, rhenium, tantalum, titanium, tungsten, or alloys thereof. In the embodiment of FIG. 4, the forming body 143 can be constructed of a refractory material, such as a ceramic refractory material.

[0061] The edge rollers 174 contact the glass layer 150 at the lateral edge portions of the glass layer and can be used to cool the glass at the lateral edge portions and help mitigate attenuation of the glass layer and / or ribbon as it is drawn from the process rollers. Thus, these functions can be performed while the glass layer is on the process rollers 146, or these functions can be performed on the glass ribbon if an edge roller is included below the process rollers (e.g., downstream edge rollers). For example, a pair of downstream edge rollers 174 can be used, where the edge rollers capture (e.g., pinch) the glass layer 150 in a gap 176 between the edge roller and the process roller. The edge rollers are typically metal, e.g., a corrosion resistant metal such as stainless steel, although other suitable metals can be used.

[0062] 5 is a front view of the processing roller 146 rotatable about a first axis of rotation 178, a first edge roller 174a rotatable about a second axis of rotation 180a, and a second edge roller 174b rotatable about a third axis of rotation 180b, where the first and second edge rollers 174a, 174b are spaced apart to contact opposing edge portions 156a, 156b, respectively, and the second axis of rotation 180a may be coaxial with the third axis of rotation 180b. The first edge roller 174a and the second edge roller 174b are spaced apart from the processing roller 146 such that there is a gap 176 between the first and second edge rollers and the processing roller, the gap 176 being sized to receive the first and second edge portions 156a, 156b, respectively. The first and second edge rollers 174a, 174b contact the glass layer 150 which is in contact with the treatment roller 146, and the edge rollers press the edge portion against the treatment roller, cooling the edge portion and increasing its viscosity, thereby reducing lateral shrinkage of the glass layer 150. The first and second edge rollers 174a, 174b can be coupled to respective motors 182a, 182b configured to rotate the respective edge rollers in a direction opposite to the direction of rotation of the treatment roller 146. As shown, the first and second edge rollers 174a, 174b can be smaller than the treatment roller 146. For example, the diameter 184 of the first and second edge rollers 174a, 174b can be in the range of about 2.5 cm to about 8 cm, such as in the range of about 3 cm to about 7 cm, about 3.5 cm to about 6.5 cm, or about 4 cm to about 6 cm, including all ranges and subranges therebetween. For comparison, the diameter 186 of the processing roller 146 can be in the range of about 5 cm to about 31 cm, about 5 cm to about 26 cm, about 5 cm to about 21 cm, about 5 cm to about 15 cm, about 5 cm to about 10 cm, about 31 cm to about 10 cm, about 31 cm to about 15 cm, about 31 cm to about 20 cm, or about 31 cm to about 25 cm, including all ranges and subranges therebetween. However, the diameter 184 of the first and second edge rollers 174a, 174b can be equal to or greater than the diameter 186 of the processing roller 146.

[0063] The first and second edge rollers 174a, 174b can have a length 188 in the range of about 1 cm to about 26 cm, e.g., about 1 cm to about 20 cm, about 1 cm to about 15 cm, about 1 cm to about 10 cm, about 1 cm to about 5 cm, about 10 cm to about 26 cm, about 15 cm to about 26 cm, about 20 cm to about 26 cm, including all ranges and subranges therebetween. The first and second edge rollers 174a, 174b are constructed and arranged to contact the edge portions 156a, 156b, respectively, of the glass layer 150 but not to contact the exposed (outwardly facing) central portion 158 of at least one surface (e.g., second major surface 166) of the glass layer 150 present on the treatment roller 146. For comparison, the entire width of the first major surface 164 of the glass layer 150 is in contact with a portion of the treatment roller 146. The treatment roller 146 may have a length in the range of about 25 cm to about 400 cm, for example, in the range of about 50 cm to about 400 cm, in the range of about 75 cm to about 400 cm, in the range of about 100 cm to about 400 cm, in the range of about 125 cm to about 400 cm, in the range of about 150 cm to about 400 cm, in the range of about 175 cm to about 400 cm, in the range of about 200 cm to about 400 cm, in the range of about 225 cm to about 400 cm, in the range of about 250 cm to about 400 cm, in the range of about 275 cm to about 400 cm, in the range of about 300 cm to about 400 cm, in the range of about 350 cm to about 400 cm, in the range of about 400 cm to about 400 cm, in the range of about 400 cm to about 400 cm, in the range of about 5 ... The length 188 can range from about 25 cm to about 400 cm, from about 300 cm to about 400 cm, from about 25 cm to about 350 cm, from about 25 cm to about 300 cm, from about 25 cm to about 250 cm, from about 25 cm to about 200 cm, from about 25 cm to about 150 cm, from about 25 cm to about 100 cm, or from about 25 cm to about 75 cm, including all ranges and subranges therebetween.

[0064] The first and second edge rollers 174a, 174b can have a variety of outer, circumferential surface finishes. For example, in some embodiments, the first and second edge rollers 174a, 174b can have a smooth outer surface, while in further embodiments, the outer, circumferential surface of the first and second edge rollers 174a, 174b can be roughened, and in some embodiments, the outer surface can be knurled.

[0065] The first and second edge rollers 174a, 174b may be cooled. For example, the first and second edge rollers 174a, 174b may be hollow or may include one or more passages through which a cooling fluid may flow. By way of example and not limitation, FIG. 6 illustrates a cross-sectional view of an exemplary edge roller 174 including an edge roller body 300 including an internal cavity 302. A shaft 304 with an internal passage 306 connects the edge roller body to a motor (not shown). A coolant supply line 308 extends through the passage 306 defined in the shaft 304 to the cavity 302. The coolant supply line is supplied with coolant 310 from a coolant supply source (not shown) and exits the coolant supply line in the cavity 302 where the coolant contacts the inner surface of the edge roller body, thereby cooling the edge roller body. The edge roller 174 may have a smooth outer contact surface 312 (the surface that contacts the molten glass or ribbon) or may have a knurled or other patterned outer surface.

[0066] The cooling of the first and second edge rollers 174a, 174b can be controlled, for example, by controlling the flow rate and temperature of a cooling fluid. Suitable cooling fluids can include water or air. The cooled first and second edge rollers 174a, 174b result in cooling the edge portions 156a, 156b and increasing the viscosity of the edge portions. The harder edge portions (as a result of the increased viscosity) resist the contraction of the molten glass layer. The molten glass layer is then ejected from the outer circumferential surface of the processing roller as a glass ribbon, and the increased viscosity of the edge portions 156a, 156b caused by contact with the first and second edge rollers 174a, 174b further reduces the contraction of the glass ribbon 152 descending from the processing roller 146. The increased viscosity of the glass ribbon 152 at the point of ejection from the processing roller 146 is approximately 10 3 From Pa·s to about 10 6 Pa·s(10 4 Poise to 10 7 poise), e.g., about 10 3 Pa·s, 10 4 Pa·s, 10 5 Pa s, or 10 6 It can be expressed as Pa·s.

[0067] The first and second edge rollers 174a, 174b can be moved vertically and / or horizontally toward or away from the treatment roller 146, and as shown in FIG. 7, the first and second edge rollers 174a, 174b can be positioned along an arc 190. The arc 190 can be concentric with the outer periphery of the treatment roller 146. The first and second edge rollers can be positioned along the arc 190 over an angular range from greater than 0 degrees to about 90 degrees (relative to TDC). Thus, the first and second edge rollers 174a, 174b can contact the glass layer 150 at any angular position along the arc 190. Movement along a horizontal position toward or away from the treatment roller 146 can also be used to increase or decrease the gap 176 between the edge rollers and the treatment roller 146. Additionally, the first and second edge rollers 174a, 174b can be moved horizontally in directions along rotational axes 180a, 180b, respectively, as shown in FIG. 8 (showing movement of the first edge roller 174a along the second rotational axis 180a).

[0068] Additional edge rollers 192 may be applied to the glass ribbon 152 downstream of the treatment rollers 146. Such additional downstream edge rollers may act on edge portions 156a, 156b such that the outwardly facing second major surface 166 of the central portion 158 of the glass ribbon 152 is not contacted. Such additional downstream edge rollers may act on opposite edge portions of the glass ribbon in counter-rotating pairs. Accordingly, FIG. 5 also shows a set of additional downstream edge rollers 192 disposed downstream of the treatment rollers 146: a first pair of counter-rotating downstream edge rollers 192a disposed along the first edge portion 156a, and a second pair of counter-rotating downstream edge rollers 192b disposed along the second edge portion 156b. The opposite edge rollers of each pair of downstream edge rollers 192a, 192b are disposed adjacent the opposite first and second major surfaces 164, 166 of the glass ribbon 152 along their respective edge portions. The downstream edge rollers 192 pair 192a, 192b are configured to contact the first and second edge portions 156a, 156b of the glass ribbon 152 without contacting the central portion 158. The downstream edge roller pairs 192a, 192b can move vertically toward or away from the processing roller 146. The downstream edge roller pairs 192a, 192b can also move horizontally along their respective rotational axes. The downstream edge rollers 192 can be driven edge rollers. For example, at least one edge roller of each downstream edge roller pair can be coupled to a motor 194. In other embodiments, each edge roller of each downstream edge roller pair can be coupled to a drive motor 194. However, in still other embodiments, none of the edge rollers of each downstream edge roller pair can be driven. The edge rollers 192 can be of the same structure as the edge rollers 174.

[0069] The pull roller assemblies 154 can be used to pull the glass ribbon 152 from the process rollers 146. For example, the pull roller assemblies 154 can include a pair of pull roller assemblies 154a, 154b, each pull roller assembly including a first pair 154a of opposing counter-rotating pull rollers 196a and a second pair 154b of opposing counter-rotating pull rollers 196b. The pull roller pairs 196a, 196b apply downward tension to the glass ribbon 152 to control the speed of travel of the glass ribbon 152 and to control the width and thickness of the glass ribbon. The pull roller pairs 196a, 196b can be of any suitable design, but each pull roller can be constructed of a compressed refractory material, for example, a plurality of fibrous ceramic disks arranged opposite each other, compressed, and mounted on a shaft. One or both pull rollers of each pull roller pair can be coupled to and driven by, for example, a motor 198.

[0070] The glass ribbon 152 may continue to cool as it descends below the drawing rollers. Any conventional methods and techniques for cooling the formed glass ribbon may be used, provided that the glass ribbon and / or at least one side of the glass ribbon remains intact.

[0071] FIG. 9 shows modeled ribbon width in millimeters as a function of edge-to-center viscosity for five different glass ribbon center viscosities (viscosity at the centerline of the glass ribbon at the point of release from the processing rollers). Center viscosities are 60 kpoise (6 kPa·s), 80 kpoise (8 kPa·s), 100 kpoise (10 kPa·s), 160 kpoise (16 kPa·s), and 200 kpoise (20 kPa·s). The data shows that as the edge-to-center viscosity ratio increases, the glass ribbon width increases. In the scenario considered in FIG. 9, a glass ribbon width of approximately 200 mm can be obtained by increasing the edge-to-center viscosity ratio by approximately 15 times (15x). A 15x change in viscosity ratio can be achieved by substantially cooling the ribbon edges using a contact heat transfer mechanism as disclosed herein.

[0072] FIG. 10 is another diagram using modeled data, showing the effect on glass ribbon width as a function of temperature drop and edge roller length at the discharge point. The simulation assumes a treatment roller length of 205 cm. From FIG. 10, it can be seen that the first and second edge rollers can improve the glass ribbon width from about 1.83 meters to about 1.93 meters (5-6% increase). It is also observed that the temperature drop is the main factor in the glass ribbon width increase. The edge roller length has a moderate effect on the glass ribbon width, but can have a large effect on the pull force. The dashed line in FIG. 10 represents the upper pull force limit, which is defined by the pulling machine system and the glass viscosity. Ribbon drawing with a large force beyond the upper pull force limit (shown by the arrow in FIG. 10) may not be feasible for a given puller. For example, in this example, the ribbon width increase is maximum for a given upper pull force limit when the edge roller length is about 50 mm. In addition, the edge roller length affects the cooling effect of the edge roller. The shorter the edge roller length, the less heat is extracted from the molten glass.

[0073] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure is intended to cover such modifications and variations provided they come within the scope of the appended claims and their equivalents. [Explanation of symbols]

[0074] 138 Connecting conduit 140 Delivery conduit 143 Molded body 144 Molten Glass Flow 146 Processing roller 148 Surface 150 Glass Layers 152 Glass Ribbon 154 Pull-out roller assembly 176 Gap 160 Thickness 164 First major surface 166 Second Main Surface 174 Downstream edge roller 192 Additional downstream edge roller

Claims

1. 1. A method of forming a glass ribbon, comprising: flowing a stream of molten glass onto an outer peripheral surface of a process roller rotating in a first rotational direction about a first rotational axis, the stream of molten glass forming a molten glass layer on the outer peripheral surface of the process roller; contacting a peripheral portion of the molten glass layer on the process roller with a first edge roller, the contact cooling the peripheral portion and increasing the viscosity of the peripheral portion, causing the molten glass layer to be ejected from the process roller as a molten glass ribbon, and the first edge roller not contacting a central portion of the molten glass layer; drawing the molten glass ribbon from the process roller in a drawing direction between a pair of drawing rolls disposed below the process roller, the pair of drawing rolls engaging the marginal portions on opposite sides of the molten glass ribbon; A method comprising:

2. The method of claim 1 further comprising contacting the marginal portion with a pair of downstream marginal rollers disposed between the treatment roller and the pair of pulling rolls.

3. The method of claim 1 , further comprising cooling the first edge roller by contacting an inner surface of the first edge roller with a cooling fluid.

4. The method of claim 1 further comprising cooling the processing roller by contacting an inner surface of the first edge roller with a cooling fluid.

5. 10. The method of claim 1, wherein the process roller has a top defined at a 0 degree angular position, and the first edge roller contacts the molten glass layer on the process roller at an angular position ranging from about 35 degrees to about 90 degrees defined in the direction of rotation of the process roller relative to the 0 degree angular position.

6. 6. The method of claim 1, wherein the molten glass layer comprises a first viscosity at a first point on the peripheral portion and a second viscosity at a center point of the molten glass layer on a horizontal line extending perpendicular to a drawing direction, and a viscosity ratio defined as the ratio of the viscosity of the molten glass layer at the first point to the viscosity of the molten glass layer at the center point is in a range of from about 1 to about 16.

7. 1. A method of forming a glass ribbon, comprising: causing a stream of molten glass to flow onto an outer peripheral surface of a process roller rotated in a first rotational direction about a first rotational axis by a first motor, the stream of molten glass forming a molten glass layer on the outer peripheral surface of the process roller; contacting a peripheral portion of the molten glass layer on the process roller with a first edge roller rotated by a second motor about a second rotational axis in a second rotational direction opposite to the first rotational direction, wherein the contact cools the peripheral portion and increases the viscosity of the peripheral portion, the molten glass layer having a first viscosity at a first point on the peripheral portion and a second viscosity at a center point of the molten glass layer on a horizontal line extending perpendicular to the drawing direction, wherein a viscosity ratio defined as the ratio of the viscosity of the molten glass layer at the first point to the viscosity of the molten glass layer at the center point is in a range of from about 1 to about 16, and the molten glass layer is discharged from the process roller as a molten glass ribbon; drawing the molten glass ribbon from the process roller in a drawing direction between a pair of drawing rolls, the drawing rolls engaging the molten glass ribbon below the process roller on opposite sides of the molten glass ribbon; A method comprising:

8. 1. An apparatus for treating molten glass, comprising: a delivery device configured to deliver a stream of molten glass; a processing roller disposed below the delivery device and positioned to receive the stream of molten glass as a molten glass layer on a surface of the processing roller and to eject the molten glass layer as a glass ribbon; a first set of edge rollers disposed adjacent to the process roller, the first set of edge rollers including: a first edge roll positioned to contact the molten glass layer at a first lateral edge portion of the molten glass layer but not at a central portion of the molten glass layer and press the first lateral edge portion against the surface of the process roller; and a second edge roll positioned to contact the molten glass layer at a second lateral edge portion of the molten glass layer but not at the central portion of the molten glass layer, opposite the first lateral edge portion, and press the second lateral edge portion against the surface of the process roller; An apparatus comprising:

9. 10. The apparatus of claim 8, further comprising a set of pulling rolls disposed below the treatment roller, the set of pulling rolls comprising a first pair of pulling rolls positioned to capture the glass ribbon at a first peripheral portion of the glass ribbon and a second pair of pulling rolls positioned to capture the glass ribbon at a second peripheral portion of the glass ribbon, wherein a first pulling roll of the first pair of pulling rolls is coupled to a first motor configured to rotate the first pulling roll, and a second pulling roll of the second pair of pulling rolls is coupled to a second motor configured to rotate the second pulling roll.

10. 10. The apparatus of claim 8 or 9, further comprising a set of downstream edge rollers positioned between the treatment rollers and the set of pulling rolls, the set of downstream edge rollers comprising a first pair of downstream edge rollers positioned to capture the glass ribbon therebetween at a first edge portion of the glass ribbon, and a second pair of downstream edge rolls positioned to capture the glass ribbon therebetween at a second edge portion of the glass ribbon.

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