Heated edge directors for glass flow stability

Abstract

A system for controlling a shape of molten glass is provided comprising a feeder, a burner configured to generate a flame, and edge director(s). The feeder defines an internal volume and a slot proximate to a bottom portion of the feeder. The internal volume is connected to the slot, and the internal volume receives molten glass so that molten glass exits the feeder at the slot. Edge director(s) are positioned relative to the slot. Each edge director comprises a body portion defining a first internal cavity and a contact portion configured to contact molten glass. Edge director(s) are positioned with contact portion(s) at least partially immersed within molten glass and so that contact portion(s) control the shape of molten glass. Heat from generated flames causes molten glass proximate to the edge director(s) to have a first viscosity greater than a second viscosity proximate to a center portion of molten glass.

Description

HEATED EDGE DIRECTORS FOR GLASS FLOW STABILITYCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 63 / 623386 filed on January 22, 2024, the content of which is relied upon and incorporated herein by reference in its entirety.FIELD

[0002] Embodiments relate generally to heated edge directors for maintaining glass flow stability.BACKGROUND

[0003] Slot draw techniques are used for ultra-thin glass forming, such as for mobile phone products. Notably, the formed slot draw sheets are susceptible to edge flow instabilities that lead to process challenges in manufacturing. Production of some ultra-thin glass products use water-cooled cold fingers to aggressively cool the edges of the slot to improve edge flow stability. However, where these water-cooled cold fingers have used, repeatability and consistency in thickness has been an issue.

[0004] Alternate heat extraction approaches such as Mist Spray Cooling (MSC), Radiative Cooling Pads (RCP), internal cooling channels have been used. While these approaches are more consistent than methods using water-cooled cold fingers, these approaches attempt to aggressively cool the slot to improve edge flow stability, and this presents a risk of devitrification in the molten glass. This devitrification often leads to inclusions in the glass, which may cause the resulting glass products to be at risk of breaking and may also lead to irregularities in the glass thickness and other glass properties. Heat extraction typically limits the available glass compositions with compatible liquidus viscosities.BRIEF SUMMARY

[0005] In various embodiments, edge directors are provided that come in contact with molten glass to assist in controlling the shape of the molten glass. The edge directors may be at least partially immersed in the molten glass by a few millimeters (e.g., less than about 1 millimeter, less than about 3 millimeters, less than about 5 millimeters, etc.) to get enough wetting so that the molten glass travels vertically along the edge directors and then departs from the edge directors due to pull forces (e.g., due to downstream rollers, nips, etc.).

[0006] The edge directors are actively heated, and the edge directors may be heated using internal oxyhydrogen burners that generate heat that is transferred to the molten glass. The heat that is transferred to the molten glass may reduce the glass attenuation and improve edge flow stability of the molten glass by allowing the center of the molten glass to increase in viscosity as the edges are supported and reheated.

[0007] Burners or other heat sources may be utilized to heat the edge directors. In some embodiments, the amount of heat that is generated may be adjusted (e.g., by increasing or decreasing the size of a flame), allowing for the viscosity of portions of the molten glass at the edges of the molten glass to be adjusted. In some embodiments, the heat at the edge directors may be controlled to temperatures of up to about 1200 degrees Celsius. By heating the edge directors, the edge directors may help to adjust the viscosity of some portions of the molten glass. Edge directors may enable glass forming at relatively low viscosities compared to current slot draw methods. In some embodiments, the forming viscosity of molten glass may be maintained between about 50 kilopoise to about 500 kilopoise, at a narrower range, or at about 100 kilopoise. However, the forming viscosity may be adjusted as desired by adjusting the temperature at the edge directors or by changing other properties of the edge directors.

[0008] The edge directors may be removable in some embodiments to increase their ease of use. Edge directors may be separable relative to the burner in some embodiments, allowing the edge directors to be removed and replaced. This may allow for increased ease of maintenance, allow for increased efficiency of use as molten glass may be allowed to continue flowing even when the edge director is being replaced, and easy removal of any inclusions that may build up on the edge director. The use of the edge directors may allow for a lower temperature gradient across the width of the molten glass, leading to a reduction in the residual stress retained in any final glass product that is formed.

[0009] Since the thicknesses at the edges of the molten glass are similar to the center sheet thicknesses, the cooling profiles may be more uniform across the width of the molten glass. This may result in lower residual stress, which may help to avoid the sheet breaking when the sheet is cut. As noted, heat extraction at a slot was another potential source of nonuniform cooling profiles leading to residual stress in molten glass on the draw. Accordingly, heat extraction techniques may be avoided when edge directors are used. The absence of heat extraction at the edges of the slot also allows for system compatibility with lower liquidus glass compositions. Where heat extraction is performed, the heat extraction techniques may limit the range of glass compositions that may be used due to forming temperatures being lower thanthe liquidus temperature, which causes devitrification of the glass at the edges over time. This devitrification leads to inclusions in the glass that may damage final glass products that are formed and that may distort the glass shape and other properties.

[0010] Systems and methods utilizing edge directors of various embodiments described herein may provide several other potential advantages. The edge directors may help to improve edge flow stability at edges of molten glass. This stability may be improved in terms of the side to side motion of molten glass (e.g., glass deflection), and the stability may also be improved in terms of glass sheet width variation. By providing improved stability, the quality area of the molten glass may be increased, allowing final glass products to be formed with improved properties. For example, final glass products may be made with a larger width, glass products may be made with a reduced thickness, and / or glass products may have reduced thickness variation. Furthermore, edge directors may assist in reducing glass attenuation so that the width of molten glass may be increased, and this reduction in glass attenuation may lead to an increased quality area width. In some embodiments, the position of the edge directors may be controlled to adjust the properties of the molten glass flow. For example, the position of edge directors relative to the glass root may be adjusted and / or the immersion depth of the edge directors may potentially be adjusted.

[0011] Various example edge directors described herein may be used to assist in forming glass with very small thicknesses of around 2 millimeters or less. The final glass products formed using the edge directors may be used in flexible mobile devices such as smartphones with foldable screens, other electronic devices with foldable screens, and in other applications where thin, foldable glass is required.

[0012] In an example embodiment, a system for controlling a shape of molten glass is provided. The system comprises a feeder defining an internal volume and a slot proximate to a bottom portion of the feeder, the internal volume configured to receive the molten glass so that the molten glass exits the feeder at the slot. The system also comprises a burner configured to generate a flame. Additionally, the system comprises one or more edge directors positioned relative to the slot. Each edge director comprises a body portion defining a first internal cavity and a contact portion configured to contact the molten glass. The edge director(s) are positioned such that the contact portions are at least partially immersed within and thereby controlling the shape of the molten glass. Upon generation of the flame by the burner, heat from the flame is configured to cause the molten glass proximate to the edge director(s) to have a first viscositythat is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass.

[0013] In some embodiments, the heat from the flame may be emitted through the first internal cavity towards the contact portion and into the molten glass contacting the edge director(s). In some embodiments, controlling the shape of the molten glass may increase a quality area of the molten glass. This quality area of the molten glass may have a thickness within a specified range of less than about 0.5 millimeters across a width of at least about 120 millimeters.

[0014] In some embodiments, each edge director may comprise an exhaust portion attached to the body portion. The exhaust portion may define a second internal cavity and an outlet. The second internal cavity, and the outlet are in fluid communication with each other. Additionally, in some embodiments, the body portion may extend at least partially along a first axis, the exhaust portion may extend at least partially along a second axis, and the first axis may be offset at an acute angle relative to the second axis.

[0015] In some embodiments, an edge director of the edge director(s) may be configured to be replaced by increasing a temperature level at the edge director, moving the edge director away from the molten glass, removing any excess molten glass from the edge director, preheating a replacement edge director, and moving the replacement edge director towards the molten glass until the replacement edge director is at least partially immersed in the molten glass.

[0016] In some embodiments, the contact portion may define a guide slot or a shape that is concave, convex, flat, ridged, multi -jointed, or curved. In some embodiments, the edge director(s) may be positioned between about 1 millimeter and about 5 millimeters below the slot. In some embodiments, the edge director(s) may comprise a first edge director and a second edge director, the molten glass may define a first edge and a second edge, and the first edge director may be at least partially immersed in the molten glass proximate to the first edge and the second edge director may be at least partially immersed in the molten glass proximate to the second edge.

[0017] Additionally, in some embodiments, the burner may comprise a burner tip where the flame is emitted, and the burner may be water cooled. Furthermore, in some embodiments, each edge director of the edge director(s) may be attached to a water drain. In some embodiments, the system may also comprise a burner assembly including the burner, the water drain, and an outer tubing extending from the water drain proximate to the burner tip. The bodyportion may extend upwardly along an incline angle between the burner and the contact portion, the outer tubing may be configured to receive water at a portion between the burner tip and the water drain, and the water drain may be positioned at a lower elevation than the contact portion. Additionally, in some embodiments, the burner may be configured to generate steam that condenses to form byproduct water, and the byproduct water may flow to at least one of the outlet or the water drain.

[0018] In another example embodiment, a method for controlling a shape of molten glass is provided. The method comprises flowing molten glass downwardly out of a slot of a feeder. The method also comprises positioning one or more edge directors relative to the slot. Each edge director of the edge director(s) comprises a body portion defining a first internal cavity and a contact portion. Additionally, the method comprises generating a flame at a burner so that heat from the flame causes the molten glass proximate to the edge director(s) to have a first viscosity that is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass. The edge director(s) are positioned such that the contact portions are at least partially immersed within the and thereby controlling the shape of molten glass.

[0019] In some embodiments, positioning the edge director(s) relative to the slot may result in the contact portion being at least partially immersed in the molten glass. Additionally, in some embodiments, positioning the edge director(s) relative to the slot may increase a quality area of the molten glass, and the quality area of the molten glass may have a thickness within a specified range of less than about 0.5 millimeters across a width of at least about 120 millimeters.

[0020] In some embodiments, the edge director(s) may include a first edge director, and the method may also include increasing a temperature level at the first edge director, moving the first edge director away from the molten glass, removing any excess molten glass from the first edge director, preheating a replacement edge director, and moving the replacement edge director towards the molten glass until the replacement edge director is at least partially immersed in the molten glass.

[0021] In some embodiments, the contact portion may define a guide slot or a shape that is concave, convex, flat, ridged, multi -jointed, or curved. In some embodiments, contact between the contact portion and the molten glass may decrease the viscosity of the molten glass. In some embodiments, the edge director(s) may be positioned between about 1 millimeter and about 5 millimeters below the slot of the feeder.

[0022] In some embodiments, each edge director of the edge director(s) may comprise an exhaust portion attached to the body portion. The exhaust portion may define a second internal cavity and an outlet, and the first internal cavity, the second internal cavity, and the outlet are in fluid communication with each other. The body portion may extend at least partially along a first axis (which may be a central or longitudinal axis for the body portion), the exhaust portion may extend at least partially along a second axis (which may be a central or longitudinal axis for the exhaust portion), and the first axis may be offset at an acute angle relative to the second axis.

[0023] In another example embodiment, an edge director for controlling a shape of molten glass is provided. The edge director comprises a body portion defining a first internal cavity and a contact portion configured to contact the molten glass. The edge director is positioned such that the contact portion is at least partially immersed within and thereby controlling the shape of the molten glass. The edge director is configured to be positioned relative to a burner such that, upon generation of the flame by the burner, heat from the flame is configured to cause the molten glass proximate to the edge director(s) to have a first viscosity that is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass.

[0024] In another example embodiment, a system for controlling a shape of molten glass is provided. The system comprises a feeder defining an internal volume and a slot proximate to a bottom portion of the feeder, with the internal volume being connected to the slot and with the internal volume being configured to receive the molten glass so that the molten glass exits the feeder at the slot. The system also comprises a burner configured to generate a flame. Additionally, the system comprises one or more edge directors positioned relative to the slot, and each edge director comprises a body portion defining a first internal cavity and a contact portion configured to contact the molten glass. Upon generation of the flame by the burner, heat from the flame is emitted through the first internal cavity towards the contact portion and into the molten glass flowing over the contact portion of the edge director(s). The heat from the flame is configured to cause the molten glass proximate to the edge director(s) to have a first viscosity that is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass. Additionally, the contact portion of the edge director(s) affects the shape of the molten glass so that, across a width of at least about 120 millimeters, a difference between a maximum thickness of the molten glass and a minimum thickness of the molten glass is about 0.5 millimeters or less.

[0025] In another example embodiment, a sheet of glass is provided that is made by a particular process. The process comprises causing molten glass to flow downwardly out of a slot of a feeder. The process also comprises positioning one or more edge directors relative to the slot, with each edge director of the edge director(s) comprising a body portion and a contact portion. The body portion defines a first internal cavity. The contact portion is configured to contact the molten glass to control a shape of the molten glass, and the edge director(s) are positioned such that the contact portion is at least partially immersed within the molten glass and so that the contact portion controls the shape of the molten glass. The process also comprises generating a flame at the burner so that heat from the flame is configured to cause the molten glass proximate to the edge director(s) to have a first viscosity that is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass.

[0026] In another example embodiment, a sheet of glass is provided that is made by a particular process. The process comprises flowing molten glass downwardly out of a slot of a feeder. The process also comprises positioning one or more edge directors relative to the slot. Each edge director of the edge director(s) comprises a body portion and a contact portion. The body portion defines a first internal cavity. Additionally, the contact portion is configured to contact the molten glass, with the edge director(s) being positioned so that the contact portion is at least partially immersed within the molten glass and thereby controlling the shape of. The process also comprises generating a flame at the burner so that heat from the flame causes the molten glass proximate to the edge director(s) to have a first viscosity that is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass. The process also comprises cutting the molten glass to remove a portion of the molten glass at an area proximate to an edge of the molten glass.BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0028] FIG. 1 is a schematic view illustrating an example system comprising edge directors, in accordance with some embodiments discussed herein;

[0029] FIG. 2A is a perspective view illustrating an example edge director assembly, in accordance with some embodiments discussed herein;

[0030] FIG. 2B is an enhanced view illustrating an example edge director in the edge director assembly of FIG. 2A, in accordance with some embodiments discussed herein;

[0031] FIG. 3A is a schematic view illustrating an example edge director and an outer tubing of a burner assembly with the edge director separated from the outer tubing, in accordance with some embodiments discussed herein;

[0032] FIG. 3B is a schematic view illustrating the example edge director of FIG. 3A partially received within the outer tubing of the burner assembly, in accordance with some embodiments discussed herein;

[0033] FIG. 4A is a cross-sectional view illustrating an example edge director received within outer tubing of a burner assembly, in accordance with some embodiments discussed herein;

[0034] FIG. 4B is a front, cross-sectional view illustrating the example edge director and outer tubing of FIG. 4A, in accordance with some embodiments discussed herein;

[0035] FIG. 4C is a schematic view illustrating various contact portions that may be used in edge directors, in accordance with some embodiments discussed herein;

[0036] FIG. 5 is a bottom, perspective view illustrating a glass sheet being formed with an edge director positioned at only one edge of the molten glass, in accordance with some embodiments discussed herein;

[0037] FIG. 6 is a graph illustrating the molten glass thickness as a function of the lateral position on molten glass for two different glass sheets, with the first glass sheet being formed without using any edge directors and with the second glass sheet being formed with edge directors on only one edge of the molten glass, in accordance with some embodiments discussed herein, in accordance with some embodiments discussed herein;

[0038] FIG. 7 is a bottom, perspective view illustrating a glass sheet being formed with edge directors on both edges of the molten glass, in accordance with some embodiments discussed herein;

[0039] FIG. 8 is a graph illustrating the molten glass thickness as a function of the lateral position on molten glass for two different glass sheets, with the first glass sheet being formed without using any edge directors and with the second glass sheet being formed with edge directors on both edges of the molten glass, in accordance with some embodiments discussed herein;

[0040] FIG. 9A is a graph illustrating the optical retardance level at different lateral positions along a width of molten glass under three different operating conditions, in accordance with some embodiments discussed herein;

[0041] FIG. 9B is a graph illustrating the temperature at contact portion of an edge director over time as the hydrogen gas level, oxygen level, and mass flow rates are adjusted, in accordance with some embodiments discussed herein;

[0042] FIG. 10 is a flow chart illustrating an example method for using one or more edge directors, in accordance with some embodiments discussed herein; and

[0043] FIG. 11 is a flow chart illustrating an example method for replacing one or more edge directors, in accordance with some embodiments discussed herein.DETAILED DESCRIPTION

[0044] Example embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments are shown. Like reference numerals generally refer to like elements throughout. For example, reference numbers 108, 508, and 708 each refer to molten glass. Additionally, any connections or attachments may be direct or indirect connections or attachments unless specifically noted otherwise.

[0045] FIG. 1 is a schematic view illustrating an example system 100 comprising edge director assemblies 112 A, 112B, with the system 100 being used to control the shape of molten glass 108. The system 100 also comprises a feeder 104. The feeder 104 defines an internal volume and a slot 106 proximate to a bottom portion of the feeder 104. The internal volume is configured to receive the molten glass 108, and the internal volume is in fluid communication with the slot 106 so that the molten glass 108 exits the feeder at the slot 106. The molten glass 108 moves downwardly due to the force of gravity, with the molten glass 108 extending between a first edge 108 A and a second edge 108B.

[0046] The system 100 also comprises a first edge director assembly 112A and a second edge director assembly 112B. The edge director assemblies 112A, 112B are described in greater detail herein in reference to FIG. 2A-2B and other figures. Each of edge director assemblies 112A, 112B comprise edge directors that are positioned relative to the slot 106. The edge director of edge director assembly 112A may be immersed in the molten glass proximate to the first edge 108A, and the edge director of the edge director assembly 112B may be immersed in the molten glass proximate to the second edge 108B. In some embodiments, the edge directors may extend around about 0 millimeters to about 10 millimeters into the molten glass 108 at the edges 108A, 108B. However, the edge directors may extend a different distance into the molten glass 108 in other embodiments. While some heat generated within the edge directors may travel by conduction through solid portions of the edge directors, some of theheat or portions of the flame may travel through the internal volume of the edge directors and out of outlets along directions indicated by arrows DI, D2. The outlets are oriented so that the directions are angled at least partially away from the molten glass 108. By doing so, the amount of heat that is transferred to the molten glass may be better controlled. Heat from the flame may be configured to cause the molten glass 108 proximate to the edge director assemblies 112A, 112B to have a first viscosity that is greater than a second viscosity of the molten glass 108 proximate to a center portion of the molten glass 108. Thus, heat from the flame may cause a viscosity gradient across a width of the molten glass.

[0047] The edge directors of edge director assemblies 112A, 112B may be positioned a distance A below the slot 106 of the feeder 104. The distance A may be measured from the uppermost point of the edge directors to the very bottom of slot 106. In some embodiments, the distance A may be greater than zero millimeters but less than about 5 millimeters below the slot 106. Additionally, in some embodiments, the distance A may be greater than about 1 millimeter but less than about 5 millimeters below the slot 106. By adjusting the vertical position of the edge director assemblies 112A, 112B, the viscosity of the molten glass may be altered significantly, and this change in viscosity may lead to a significant change in the lateral forces acting on molten glass. Positioning the edge director assemblies 112A, 112B at the distance A of less than about 5 millimeters below the slot 106 may result in a desired level of viscosity and lateral forces for the molten glass. Additionally, by positioning the edge director assemblies 112A, 112B at a distance A of less than about 5 millimeters below the slot 106, the flow properties for molten glass may be more desirable. Additionally, the edge directors of the edge director assemblies 112A, 112B may each be positioned so that the extreme tip of the edge directors is positioned at a distance A’ away from the slot edges when measured horizontally. In some embodiments, this distance A’ may be about 15 millimeters, but the distance A’ may be different in other embodiments.

[0048] As the molten glass 108 moves downwardly, the molten glass 108 may tend to cool, with the molten glass 108 eventually solidifying to form a solidified processing sheet of glass. The molten glass or the processing sheet of glass may extend through a gap between two rollers 110. The rollers 110 may be positioned a distance B below the slot 106. The distance B may be about 1.5 meters in some embodiments. However, the rollers may be positioned at different distances from the slot 106 in other embodiments. In the embodiment illustrated in FIG. 1, two rollers 110 are provided and the rollers 110 extend across the entire width of the molten glass 108. However, in other embodiments, a different number of rollers 110 may be used. Forexample, four rollers may be used, with two rollers positioned proximate to a first edge 108 A of the molten glass 108 and with another two rollers positioned proximate to a second edge 108B of the molten glass 108, where no roller is positioned in central portion of the molten glass. Eventually, the processing sheet of glass may be cut using one or more cutters 107. In the embodiment illustrated in FIG. 1, the cutter(s) 107 are laser cutters that are configured to emit a laser 107A towards the processing sheet of glass. The cutter(s) 107 may also be configured to remove material proximate to a first edge 108 A and a second edge 108B, and this may be beneficial as the glass properties (e.g., thickness) may be different at these edges 108 A, 108B relative to central portions of the molten glass 108. Once cut, the processing sheet of glass may be processed in other ways to help form a final glass product 105.

[0049] An example edge director assembly 212 comprising an edge director 202 and a burner 218 is illustrated in FIG. 2A. The edge director 202 comprises a body portion 216A, an exhaust portion 216B, and a contact portion 216C. In FIG. 2 A, the body portion 216A includes an inner tubing 216, and the inner tubing 216 may be received within the internal volume of the outer tubing 214 such that an effective seal is formed between the inner tubing 216 and the outer tubing 214, with the outer surface of the inner tubing 216 being attached to the inner surface of the outer tubing. The body portion 216A defines an internal cavity extending through the outer tubing 214 and the inner tubing 216. Some or all of the contact portion 216C is configured to contact molten glass and to control the shape of the molten glass. The exhaust portion 216B is attached to the body portion 216A, with the exhaust portion 216B defining a second internal cavity and an outlet 216D.

[0050] As illustrated in the enhanced view of FIG. 2B, the burner 218 may be positioned so that it will generate a flame that will be emitted into the edge director 202. The burner 218 may define a burner tip 218A where a flame is generated. The burner 218 may extend within the outer tubing 214 and partially into the inner tubing 216 so that the burner tip 218A is positioned within the internal volume of the inner tubing 216. The burner 218 may be configured to emit oxygen and hydrogen at the burner tip 218A. Additionally, in some embodiments, a water source may be configured to emit water into the outer tubing 214 to assist in cooling the burner 218. Upon generation of a flame by the burner 218, heat from the flame is emitted through internal cavities within the edge director 202 and out of the outlet 216D. More specifically, some heat from the flame is emitted by convection through a first internal cavity defined at the body portion 216A towards the contact portion 216C and then through a second internal cavity defined at the exhaust portion 216B until the heat is directedout of the outlet 216D. Additionally, some of the heat may also move through the solid portions of the edge director 202 via conduction so that heat is conducted to molten glass flowing over the edge director 202 proximate to the contact portion 216C. In the edge director 202, the body portion 216A defines a first axis Al that generally extends through the center of the body portion 216A, the exhaust portion 216B defines a second axis A2 that generally extends through the center of the exhaust portion 216B, and the axes Al, A2 are angularly offset from each other by an angle 02. The angle 02 may be an acute angle in some embodiments so that, when the edge director 202 is being used, any heat or flames emitted out of the outlet are directed away from the molten glass as illustrated by arrows DI, D2 of FIG. 1.

[0051] The edge director assembly 212 of FIG. 2 A comprises a burner assembly 211, with the burner assembly 211 comprising a burner 218, an outer tubing 214, and a water drain 222. The edge director 202 may be removably attached to the burner assembly 211 by inserting the inner tubing 216 of the edge director 202 into the outer tubing 214 of the burner assembly 211. The body portion 216A of the edge director 202 is inclined at an angle 01. Steam or water may be generated as a byproduct of combustion when the burner 218 is an oxyhydrogen burner. When steam is generated, it may eventually condense to water. Some of this steam or water may be urged out through the edge director 202 and out of the outlet 216D. Other portions of this steam or water may be urged in the opposite direction, moving back towards the water drain 222. The water drain 222 may be positioned at a lower elevation than the contact portion 216C due to the incline angle 01. In some embodiments, the internal volume of the outer tubing 214 may include water therein to assist in cooling the burner 218. When this is the case, the water used to cool the burner 218 may generally remain at locations between the burner tip 218A and the water drain 222 due to the incline of the edge director 202. While a burner 218 is utilized in the embodiment illustrated in FIGS. 2A-2B, other heat sources may be used as well. For example, an electrical heater or some other heat source may be used in place of the burner 218 and other burners described herein in some embodiments.

[0052] The edge director assembly 212 may be mounted to a mounting bracket 226 in some embodiments, with the position of the edge director assembly 212 being adjustable. For example the joint 223 may be adjusted relative to the arm 228 to shift the edge director 202 along the axis Bl, the edge director 202 may be rotated about the X-axis as indicated by the arrows B2 by rotating the arm 228 relative to the ball joint 224, the edge director 202 may be moved up and down along the axis B3 (which may be parallel to the Y-axis) using the ball joint 224, the edge director 202 may be moved along axis B4 (which may be parallel to the X-axis)by moving the ball joint 224 relative to the mounting bracket 226, or the edge director 202 may rotated about the Y-axis as indicated by arrows B5 by rotating the ball joint 224 relative to the mounting bracket 226. However, the edge director assembly 212 may also be moved in other ways. Additionally, the set up for the edge director assembly 212 may be different in other embodiments. Actuators may be used in some embodiments to move the edge director assembly 212 automatically, and this may be beneficial to reduce the exposure of human operators to the hot molten glass and to increase safety of the edge director assembly 212. By allowing for adjustments in positioning of components for the edge director assembly 212, the X, Y, and Z positions of the edge director assembly may be adjusted, the distance of the edge director from the slot may be adjusted, the position of the edge director relative to a center thickness plane of the molten glass may be adjusted, the immersion depth may be adjusted, the entry angle for the edge director into the molten glass attenuation zone may be adjusted, etc..

[0053] FIG. 3A-3B are schematic views illustrating an example edge director 302 and outer tubing 314 of a burner assembly. In FIG. 3 A, the edge director 302 is separated from the outer tubing 314, and the edge director 302 is partially received within the outer tubing 314 in FIG. 3B. The outer tubing 314 may generally define a circular cross-sectional shape and an interior volume that also has a circular shape, with the outer tubing 314 defining an outer diameter of about 14 millimeters and an inner diameter of about 10 millimeters. Additionally, the outer tubing 314 defines an outer surface 315 A and an inner surface 315B. The outer tubing 314 defines a length C. In some embodiments, the length C may be about 300 millimeters, but the length C may possess other values in other embodiments.

[0054] The edge director 302 includes the inner tubing 316. The inner tubing 316 may generally define a circular cross-sectional shape and an interior volume that also has a circular shape, with the inner tubing 316 defining an outer diameter of about 10 millimeters and an inner diameter of about 6 millimeters. The inner tubing 316 defines an outer surface 317A and an inner surface 317B. The outer surface 317A of the inner tubing 316 may be attached to the inner surface 315B of the outer tubing 314, and, in some embodiments, an effective seal may be formed between the surfaces 315B, 317A. The outer tubing 314 may overlap with the inner tubing 316 by an overlap length E. This overlap length E may be about 25 millimeters in some embodiments, but the overlap length E may possess other values in other embodiments. The outer tubing 314 may be positioned relative to the inner tubing 316 such that the outer tubing 314 is positioned at a distance D from the extreme tip of the contact portion 316C when measured along the lengthwise direction of the body portion 316A (e.g., horizontally in FIG.3). The distance D may be about 50 millimeters in some embodiments, but the distance D may possess other values in other embodiments. Additionally, as illustrated in FIG. 3 A, the inner tubing 316 may define a length G of about 75 millimeters in some embodiments (e.g., the distance D plus the overlap length E), but this length G may be different in other embodiments.

[0055] The edge director 302 includes an exhaust portion 316B attached to the inner tubing 316 at the body portion 316A of the edge director 302 so that the internal volume of the body portion 316A is in fluid communication with the internal volume of the exhaust portion 316B and the outlet 316D positioned at the end of the exhaust portion 316B. Unlike some other embodiments described herein, the exhaust portion 316B is positioned some distance F away from the contact portion 316C of the edge director 302. The distance F may be measured along the lengthwise direction of the body portion 316A (e.g., horizontally in FIG. 3) from the center of the exhaust portion 316B to the extreme tip of the contact portion 316C. In some embodiments, distance F may be about 25 millimeters. However, the distance F may possess other values in other embodiments. Additionally, the distance F may be zero in some embodiments as exemplified by other embodiments illustrated in the drawings and described herein. The distance F may be selected to adjust the distance from the flame to the exhaust portion 316B and to adjust the distance from the exhaust portion 316B to any molten glass. While the exhaust portion 316B is illustrated as having a smaller diameter as the body portion 316A, the size of the exhaust portion 316B may be greater than or equal to the size of the body portion 316A in some embodiments.

[0056] Similar to the edge director 202 of FIGS. 2A-2B, the body portion 316A of the edge director 302 extends at least partially along a first axis, a portion of the exhaust portion 316B extends at least partially along a second axis, and the first axis is offset at an acute angle relative to the second axis.

[0057] As illustrated in FIGS. 3A-3B, the edge director may be easily replaced without disrupting the overall forming platform in some embodiments. For example, the edge director may be replaced without changing out or otherwise adjusting the slot assembly, the heating chamber, or the burner assembly. Replacement may also be achieved while molten glass is still flowing, allowing avoidance of disruptions upstream to the process such as glass melting and fining.

[0058] Another example edge director 402 is illustrated in the cross-sectional view of FIG. 4A. The edge director 402 comprises a body portion 416A including an inner tubing 416. Furthermore, a burner assembly may include an outer tubing 414. The outer tubing 414 isconfigured to receive the inner tubing 416 of the edge director 402 within an interior volume of the outer tubing 414. The outer tubing 414 has an outer surface 415A and an inner surface 415B, and the inner tubing 416 also has an outer surface 417A and an inner surface 417B. The outer surface 417A of the inner tubing 416 may generally be in contact with the inner surface 415B of the outer tubing 414, and the surfaces 417A, 415B may be attached together to form a seal. Adhesives may be used to attach the surfaces 417A, 415B together, but adhesives may be omitted in other embodiments and the surfaces 417A, 415B may be attached together in other ways. A contact portion 416C is shown in FIG. 4A with generally a semi -spherical shape, but contact portions having other shapes may be used as well as illustrated in FIG. 4C.

[0059] An exhaust portion 416B is also included in the edge director 402. The exhaust portion 416B is attached to the body portion 416A at the inner tubing 416. The body portion 416A may define an internal cavity inside of the surfaces 415B, 417B, and another internal cavity may also be defined in the exhaust portion 416B that is in fluid communication with the internal cavity of the body portion 416A so that heat, fluid, a flame, other material, etc. may flow to the outlet 416D at the end of the exhaust portion 416B. The exhaust portion 416B extends at an angle 03 relative to a lengthwise direction of the inner tubing 416. This angle 03 may possess a wide variety of values. In some embodiments, the angle 03 may be a value between about 0 degrees and about 90 degrees. Additionally, the exhaust portion 416B may extend towards the right side of the edge director 402 in FIG. 4A (e.g., the angle 03 could range from a value between 0 degrees and about -90 degrees).

[0060] A burner 418 is also illustrated in FIG. 4A within the edge director 402. The burner 418 may extend lengthwise through the center of the body portion 416A. In some embodiments, the burner 418 may generally define a cylindrical shape or a prism shape, but the burner 418 may have other shapes. The burner 418 may extend to a burner tip 418A, and the burner 418 may be configured to emit a flame at the burner tip 418A. The burner 418 may extend partially into the internal volume defined by the inner tubing 416, but a space 421 may be left between the burner 418 and the inner surface 417B of the inner tubing 416. This space 421 may enable the flow of some material such as steam or water that may be generated as a byproduct of combustion so that the steam or water may flow back to a water drain 222 (see FIG. 2A). This space 421 travels circumferentially around the burner 418 in FIG. 4A, but the space 421 may possess different shapes in other embodiments.

[0061] The edge director 402 of FIG. 4A is illustrated in further detail in the front, crosssectional view ofFIG. 4B. As may be seen in FIG. 4B, the outer tubing 414 and the inner tubing416 both generally possess circular shapes with common center points. The exhaust portion 416B attaches to the body portion 416A, and the end of the exhaust portion 416B generally extends at an angle 04 relative to a horizontal. This angle 04 may possess various values. In some embodiments, the angle 04 may be a value between about 0 degrees and about 90 degrees. Additionally, the exhaust portion 416B may extend towards the right side of the edge director 402 in FIG. 4B (e.g., the angle 04 could range from a value between 90 degrees and about 180 degrees).

[0062] In some embodiments, the edge director 402 may generally comprise a material such as silica, fused silica, platinum (e.g., a platinum alloy), nickel (e.g., a nickel alloy), quartz, Inconel, or another similar material. The material of the edge director 402 may be configured to assist in wetting the molten glass when the material is in contact with the molten glass.

[0063] The contact portion that is utilized on an edge director 402 may be shaped as desired to interact with molten glass. The contact portion may be in contact with the molten glass at a small distance below a slot of a feeder to reduce pull force tension from attenuating the molten glass before the center of the molten glass reaches higher viscosities that reduce lateral attenuation. FIG. 4C is a schematic view of various contact portions that may be used. For example, a slotted contact portion 425A may be provided. The slotted contact portion 425A includes portions 427 A’, 427 A” that extend further than end surface 427 A. The surface 427 A defines a flat shape with a taper angle similar to the flat contact portion 425F. In some embodiments, the end surfaces of portions 427A’, 427A” may also define a flat shape with a taper angle similar to the taper angle of the surface 427A. However, in other embodiments, the surface 427A may define a convex curvature, concave curvature, or some other shape, and portions 427 A’, 427 A” may still project out further from surface 427 A. Where the slotted contact portion 425A is used, molten glass may tend to remain in a slot formed between the portions 427 A’, 427 A”.

[0064] Another contact portion that may be used is the concave contact portion 425B. With this concave contact portion 425B, the end surface 427B has a three-dimensional concave curvature. The end surface 427B has a concave shape along the curved line A3 and the curved line A4, with the curved lines A3, A4 being perpendicular to each other at an intersection point. The end surface 427B is generally inclined at an angle.

[0065] A semi-spherical contact portion 425C may also be used. For the semi-spherical contact portion 425C, the end surface 427C has a semi-spherical shape, with the end surface 427C defining a three-dimensional convex curvature.

[0066] As another example, a convex contact portion 425D may be used. For the convex contact portion 425D, a side view is illustrated. The convex contact portion 425D comprises an end surface 427D that defines a two-dimensional convex curvature.

[0067] A concave contact portion 425E may also be used. For the concave contact portion 425E, a side view is illustrated. The concave contact portion 425E comprises an end surface 427E that defines a two-dimensional concave curvature.

[0068] Also, a flat contact portion 425F may be used. For the flat contact portion 425F, a side view is illustrated. The flat contact portion 425F comprises an end surface 427F that is flat and that defines a taper angle 05 relative to the top and bottom surfaces of the flat contact portion 425F. The taper angle 05 may possess a wide variety of values. For example the taper angle 05 may be a value above 0 degrees but less than about 10 degrees, above 0 degrees but less than about 8 degrees, above 0 degrees but less than about 6 degrees, above 0 degrees but less than about 4 degrees, etc.

[0069] Another contact portion 425G is also illustrated that may be used. As indicated by the arrows inside of the contact portion 425G, heat from a burner or from another heat source may travel by convection through the internal volume of the contact portion 425G. Upon reaching the end surface 427G, some of this heat may travel by conduction through the end surface 427G so that the heat is transferred to molten glass flowing over the end surface 427G. Additionally, some of the heat may travel by convection through the internal volume out of the exhaust portion 416B’ through the outlet 416D’. The contact portion 425G is unique in that it has multiple comer bends 419A, 419B, and the end surface 427G may have an increased surface area with the molten glass. In some embodiments, the end surface 427G may be flat, curved, concentrically curved, concave, convex, slotted, or may have some other shape. The end surface 427G may define a taper angle similar to the taper angle 05.

[0070] Another contact portion 425H is illustrated in FIG. 4C, with the contact portion 425H terminating with two flat end surfaces 427H, 427EF on opposing sides of a vertically oriented ridge 431. The end surfaces 427H, 427EF extend directly up and down, but the end surfaces 427H, 427EF may be inclined at an angle in some embodiments. Furthermore, while the ridge 431 extends directly up and down in FIG. 4C, the ridge 431 may be inclined at an angle in other embodiments.

[0071] The contact portions 425A-425H are each merely examples of potential contact portions that may be used, and other contact portions may also be used.

[0072] FIG. 5 is a bottom, perspective view illustrating a glass sheet being formed with an edge director 502 positioned at only one edge of the molten glass 508. Similar to other edge directors described herein, edge director 502 comprises a body portion 516A having an inner tubing 516 that may be received within an outer tubing 514 of a burner assembly. The edge director 502 has a corner bend proximate to the contact portion 516C and the exhaust portion 516B is attached to the body portion 516A proximate to the contact portion 516C. The exhaust portion 516B ultimately ends with an outlet 516D. Contact between the contact portion 516C and the molten glass 508 may decrease the viscosity of molten glass 508 proximate to the first edge 508A. However, the heating of the molten glass 508 may be controlled so that the viscosity of the molten glass 508 is not reduced too much. In some embodiments, the viscosity of the molten glass 508 may be maintained at levels between about 50 kilopoise to about 500 kilopoise, 60 kilopoise and about 400 kilopoise, between about 70 kilopoise and about 300 kilopoise, between about 80 kilopoise and about 250 kilopoise, between about 90 kilopoise and about 200 kilopoise, or at about 100 kilopoise. The forming viscosity may be adjusted as desired by adjusting the temperature at the edge directors or by changing other properties of the edge directors. By controlling the viscosity, the wetting properties for molten glass 508 at the edge director 502 may be controlled as desired.

[0073] The molten glass 508 extends downwardly from the slot 506. The molten glass 508 extends downwardly between a first edge 508A and a second edge 508B. The edge director 502 is positioned so that it is partially immersed within the molten glass 508 proximate to the first edge 508A, and, in FIG. 5, no edge director 502 is positioned proximate to the second edge 508B. The edge director 502 may be positioned some distance below the slot 506 in some embodiments. The edge director 502 is positioned at first area 528A that is proximate to the slot 506. As the molten glass 508 flows down to the second area 528B, the width of the molten glass 508 (e.g., from left to right) tends to decrease. However, lateral position of the first edge 508A tends to change much less than the lateral position of the second edge 508B, and this tends to show that the edge director 502 assisted in increasing the width of the molten glass 508. This is further evident in view of the results illustrated in FIGS. 7-8 and described herein.

[0074] The edge directors described herein may control a shape of molten glass so that a quality area of the molten glass is increased, with the quality area of the molten glass having a thickness within a specified range. FIG. 6 is a graph 630 illustrating the molten glass thickness as a function of the lateral position on molten glass for two different glass sheets, with the firstglass sheet being formed without using any edge directors and with the second glass sheet being formed with edge directors on only one edge of the molten glass.

[0075] In the graph 630, a first plotline 632 illustrates the thickness profile where no edge directors were used. The first plotline 632 extends between an end region 632A and an end region 632B. The end regions 632A, 632B both possess thicknesses of about 2.5 millimeters. However, in central portions of the first plotline 632, the thickness is about 1.5 millimeters. Where final glass products must have a thickness that remains within + / - 0.1 millimeters of a target thickness, only about 70 millimeters of the glass may fall within this target thickness range.

[0076] Additionally, a second plotline 634 illustrates the thickness profile where an edge director was used on only one edge as illustrated in FIG. 5. The second plotline 634 extends between an end region 634A and an end region 634B, with end region 634A corresponding to the edge of the molten glass where an edge director was used and with end region 634B corresponding to the edge of the molten glass where no edge director was used. Like the end regions 632A, 632B for the first plotline, the end region 634B for the second plotline is around 2.5 millimeters in thickness. However, the end region 634A for the second plotline 634 is around 1.25 millimeters, which is much more similar to the thicknesses at other central portions of the second plotline 634. In central portions of the second plotline 634, the thickness ranges between about 1.1 millimeters and about 1.5 millimeters. Where final glass products must have a thickness that remains within + / - 0.1 millimeters of a target thickness, about 85 millimeters of the glass may fall within this target thickness range. Thus, even using only one edge director tended to improve thickness uniformity.

[0077] Notably, the second plotline 634 has other differences relative to the first plotline 632. For example, the second plotline 634 is spread across a larger width, and this is due to the addition of the edge director. Furthermore, most portions of the second plotline 634 possess a smaller thickness relative to the first plotline 632.

[0078] FIG. 7 is a bottom, perspective view illustrating a glass sheet being formed with a first edge director 702 positioned at a first edge 708A of the molten glass 708 and with a second edge director 702’ positioned at a second edge 708B of the molten glass 708. The edge directors 702, 702’ may be positioned some distance below the slot 706 in some embodiments. Similar to other edge directors described herein, first edge director 702 comprises a body portion 716A having an inner tubing 716 configured to be received in an outer tubing 714 of a burner assembly. The first edge director 702 has a comer bend proximate to the contact portion 716Cand the exhaust portion 716B is attached to the body portion 716A proximate to the contact portion 716C. The exhaust portion 716B ultimately ends with an outlet 716D. Similar to other edge directors described herein, second edge director 702’ comprises a body portion 716A’ having inner tubing 716’ configured to be received in an outer tubing 714’ of a second burner assembly. The second edge director 702’ has a corner bend proximate to the contact portion 716C’ and the exhaust portion 716B’ is attached to the body portion 716A’ proximate to the contact portion 716C’. The exhaust portion 716B’ ultimately ends with an outlet 716D’.

[0079] Contact between the contact portions 716C, 716C’ and the molten glass 708 may decrease the viscosity of the molten glass 708. However, the heating of the molten glass 708 may be controlled so that the viscosity of the molten glass 708 is not reduced too much. In some embodiments, the viscosity of the molten glass 708 may be maintained at levels between about 50 kilopoise to about 500 kilopoise, 60 kilopoise and about 400 kilopoise, between about 70 kilopoise and about 300 kilopoise, between about 80 kilopoise and about 250 kilopoise, between about 90 kilopoise and about 200 kilopoise, or at about 100 kilopoise. The forming viscosity may be adjusted as desired by adjusting the temperature at the edge directors or by changing other properties of the edge directors. By controlling the viscosity, the wetting properties for molten glass 708 at the edge director 702 may be controlled as desired.

[0080] The molten glass 708 extends downwardly from the slot 706. The molten glass 708 extends downwardly between a first edge 708A and a second edge 708B. The first edge director 702 is positioned so that it is partially immersed within the molten glass 708 proximate to the first edge 708A, and first edge director 702 is positioned so that it is partially immersed within the molten glass 708 proximate to the second edge 708B. The immersion depth of the edge directors 702, 702’ may possess different values. For example, the immersion depth may be between about 0 millimeters and about 10 millimeters, between about 0 millimeters and about 8 millimeters, between about 0 millimeters and about 6 millimeters, between about 0 millimeters and about 4 millimeters, etc. The edge directors 702, 702’ are both positioned at a first area 728A that is proximate to the slot 706. As the molten glass 708 flows down to the second area 728B, the width of the molten glass 708 (e.g., from left to right) tends to decrease. However, the width of the molten glass 708 is significantly greater than when the molten glass is formed with no edge directors or with only one edge director.

[0081] As illustrated in FIG. 7, some deviation in the width of the glass may exist from the first edge 708A to the second edge 708B depending on the distance from the slot 706. For example, at the first area 728A (which is proximate to the slot 706), the width of the glass fromthe first edge 708A to the second edge 708B may be greater than the width of the glass from the first edge 708A to the second edge 708B at the second area 728B (which is positioned a greater distance away from the slot 706 relative to the first area 728A).

[0082] While the edge directors 502, 702, 702’ generally extend in a lengthwise direction that is parallel to a central plane formed by the molten glass 508, 708, edge directors may be positioned and / or oriented differently in other embodiments. Additionally, while edge directors 502, 702, 702’ are each in contact with the molten glass merely at the edges of the molten glass, other edge directors may be utilized that are in contact with other portions of the molten glass such as sides and / or the central portions of the molten glass.

[0083] The edge directors described herein may control a shape of molten glass so that a quality area of the molten glass is increased, with the quality area of the molten glass having a thickness within a specified range. FIG. 8 is a graph 836 illustrating the glass thickness as a function of the lateral position on glass for two different glass sheets, with the first glass sheet being formed without using any edge directors and with the second glass sheet being formed with edge directors on both edges of the molten glass.

[0084] In the graph 830, a first plotline 838 illustrates the thickness profile where no edge directors were used. The first plotline 838 extends between an end region 838 A and an end region 838B. The end regions 838 A, 838B both possess thicknesses of about 2.5 millimeters. However, in central portions of the first plotline 838, the thickness is about 1.5 millimeters. Where final glass products must have a thickness that remains within + / - 0.1 millimeters of a target thickness, only about 75 millimeters of the glass may fall within this target thickness range.

[0085] Additionally, a second plotline 840 illustrates the thickness profile where an edge director was used at both edges of molten glass as illustrated in FIG. 7. The second plotline 840 extends between an end region 840 A and an end region 840B. Unlike the end regions 838 A, 838B for the first plotline 838, the end regions 840 A, 840B for the second plotline 840 are both around 1.5 millimeters in thickness. In central portions of the second plotline, the thickness ranges between about 1.3 millimeters in thickness and about 1.5 millimeters in thickness. Where final glass products must have a thickness that remains within + / - 0.1 millimeters of a target thickness, effectively all 142 millimeters of the glass represented by the second plotline 840 fall within this thickness range. Thus, the second plotline 840 demonstrates that the edge directors are capable of significantly improving thickness uniformity within glass. However, in other embodiments, the thickness may be deviate by less than 0.25 millimetersfrom a target thickness across a width of at least 120 millimeters, the thickness may be deviate by less than 0.1 millimeters from a target thickness across a width of at least 120 millimeters or the thickness may deviate in other amounts. In some embodiments, the use of edge directors at both edges of the molten glass may cause the thicknesses proximate to the edges to be less than the thicknesses at central portions of the molten glass. Additionally, in some embodiments, the use of edge directors may cause the edges of the processing sheets of glass to terminate at very small radiuses.

[0086] Notably, the second plotline 840 has other differences relative to the first plotline 838 and even plotline 634 of FIG. 6 (where only one edge director is used). For example, the second plotline 840 is spread across a larger width, and this is due to the use of two edge directors. The width may be increased by around 40 millimeters where two edge directors are used rather than zero edge directors, and the width may also be increased by around 17 millimeters where two edge directors are used rather than only one edge director. Furthermore, most portions of the second plotline 840 possess a smaller thickness relative to the first plotline 838.

[0087] The use of edge directors may also help to reduce stress in glass products that are formed. Optical retardance is generally impacted by the amount of stress in glass products and the thickness of glass products, so a reduction in the amount of stress in glass products may lead to a reduction in optical retardance as well. FIG. 9A is a graph 942 illustrating the optical retardance in nanometers as a function of the glass width in millimeters under three different operating conditions. The plotline 944 illustrates control data where molten glass was permitted to freely exit a slot without any edge directors or heat extraction techniques, the plotline 946 used heat extraction techniques, and the plotline 948 used edge directors as proposed in various embodiments described herein. The data illustrated in graph 942 show that the plotline 946 was high in central portions of glass relative to plotlines 944, 948, and this reveals that the use of heat extraction increased the stress in glass compared to other systems using edge directors and other control systems. Other than the lateral positions between 0 millimeters and 5 millimeters in the graph 942, plotline 948 generally maintained optical retardance levels at less than 30 millimeters. From lateral positions between about 20 millimeters to about 142 millimeters, the optical retardance levels may be less than about 15 millimeters. By contrast, plotlines 944, 946 both exceeded these values at center positions of the plotlines, showing that the central portions of glass products formed using two edge directors tended to have less stress and a higher quality.

[0088] Burners may provide an effective solution for rapidly changing the temperature at a contact portion of an edge director. FIG. 9B is a graph 950 illustrating the temperature at contact portion of an edge director over time as the hydrogen gas level, oxygen level, and / or mass flow rates are adjusted. The temperature remains around 0 degrees initially, and then the temperature rapidly increases to around 700 degrees Celsius around a time of 50 seconds. This and the other sharp increases in temperature show that the burner approach is effective in rapidly increasing the temperature of the contact portions of edge directors. Additionally, as shown around the time of 275 seconds in the graph 950, the temperature begins a sharp decline from 750 degrees Celsius to about 33 degrees Celsius. The rate of temperature reduction is very large initially, and the rate of temperature reduction gets smaller over time so that the temperature reduces more slowly once the temperature decreases. This and other sharp decreases in temperature show that the burner approach is effective at rapidly decreasing the temperature of the contact portions of edge directors when necessary. Thus, the burner approach may effectively allow a user to make quick adjustments to the temperature at the contact portions of edge directors. However, other heat sources such as electrical heat sources may be used as well.

[0089] FIG. 10 is a flow chart illustrating an example method 1000 for using one or more edge directors to control a shape of molten glass. At operation 1002, molten glass is caused to flow out of a feeder. The feeder may define an internal volume and a slot proximate to a bottom portion of the feeder. The internal volume may be connected to the slot, and the internal volume may be configured to receive the molten glass so that the molten glass exits the feeder at the slot. The molten glass may flow downwardly out of the slot of the feeder due to the force of gravity.

[0090] At operation 1004, edge director(s) are positioned relative to the slot of the feeder. The edge director(s) may be similar to other edge director(s) in embodiments described herein. Positioning the edge director(s) relative to the slot may result in the contact portion being at least partially immersed in the molten glass. The edge director(s) may be positioned between about 1 millimeter and about 5 millimeters below a slot of a feeder.

[0091] At operation 1006, a flame is generated at a burner. By doing so, heat from the flame may cause the molten glass proximate to the edge director(s) to have a first viscosity that is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass. Additionally, by generating a flame, heat from the flame may be emitted through the first internal cavity of an edge director towards the contact portion of the edge director and throughthe second internal cavity of the edge director until the heat extends out of the outlet. When the contact portion of the edge director is in contact with the molten glass, the heat generated at the edge director may be transferred to the molten glass flowing over the contact portion to decrease the viscosity of the molten glass.

[0092] At operation 1008, the molten glass or solid glass that has cooled may be cut to remove one or more portions of molten glass at areas proximate to the edges of the molten glass. Molten glass or cooled glass may be cut to remove a sheet from the remainder of the molten glass.

[0093] The method 1000 may result in the quality area of the molten glass having an increased size. This may enable the final glass product that is formed after cutting the molten glass at operation 1008 to be larger. In some embodiments, the quality area of the glass may have a thickness within a specified range of less than about 0.5 millimeters or less than about 0.2 millimeters across a width of at least about 120 millimeters.

[0094] FIG. 11 is a flow chart illustrating an example method 1100 for replacing one or more edge directors. At operation 1102, a temperature level is increased at the edge director(s). This may be accomplished by increasing the power level at a burner or at some other heat source. Additionally or alternatively, the temperature level may be adjusted by altering the amount of hydrogen or oxygen emitted at a burner tip (e.g., by increasing or decreasing the amount of hydrogen that is emitted relative to the amount of oxygen that is emitted) or by changing the flow rate at the burner. At operation 1104, the edge director(s) are moved away from the molten glass. At operation 1106, excess molten glass is removed from the edge director(s). At operation 1108, one or more replacement edge directors are preheated. In some embodiments, the replacement edge director(s) may be the edge director(s) that have any excess molten glass removed in operation 1106. At operation 1110, replacement edge director(s) are moved towards the molten glass until the replacement edge director(s) are partially immersed in the molten glass. At operation 1112, the replacement edge director(s) may be at least partially retracted to an operational position. By retracting the replacement edge director(s) some distance, the sheet width for molten glass may be maximized and molten glass may still wet to the replacement edge director(s).

[0095] Methods 1000 and 1100 are both merely set forth as examples, and the methods 1000, 1100 may be modified in various ways. The methods 1000, 1100 may be modified by adding additional operations and / or by omitting certain operations. The methods 1000, 1100 may also be modified by changing the order of operations or by performing certain operationssimultaneously. In some embodiments, the methods 1000, 1100 may be combined together to form a single method.CONCLUSION

[0096] Many modifications and other embodiments set forth herein will come to mind to one skilled in the art to which these embodiments pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the embodiments are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the invention. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and / or functions, it should be appreciated that different combinations of elements and / or functions may be provided by alternative embodiments without departing from the scope of the invention. In this regard, for example, different combinations of elements and / or functions than those explicitly described above are also contemplated within the scope of the invention. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

THAT WHICH IS CLAIMED:

1. A system for controlling a shape of molten glass, the system comprising: a feeder defining an internal volume and a slot proximate to a bottom portion of the feeder, the internal volume configured to receive the molten glass so that the molten glass exits the feeder at the slot; a burner configured to generate a flame; one or more edge directors positioned relative to the slot, wherein each edge director of the one or more edge directors comprises: a body portion defining a first internal cavity; and a contact portion configured to contact the molten glass, wherein the one or more edge directors are positioned such that the contact portions are at least partially immersed within and thereby affect the shape of the molten glass, and wherein, upon generation of the flame by the burner, heat from the flame is configured to cause the molten glass proximate to the one or more edge directors to have a first viscosity that is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass.

2. The system of claim 1, wherein the heat from the flame is emitted through the first internal cavity towards the contact portion and into the molten glass contacting the one or more edge directors.

3. The system of claim 1 or claim 2, wherein each edge director of the one or more edge directors comprises an exhaust portion attached to the body portion, the exhaust portion defining a second internal cavity and an outlet, and wherein the first internal cavity, the second internal cavity, and the outlet are in fluid communication with each other.

4. The system of claim 3, wherein the body portion extends at least partially along a first axis, the exhaust portion extends at least partially along a second axis, and the first axis is offset at an acute angle relative to the second axis.

5. The system of any of claims 1-4, wherein controlling the shape of the molten glass increases a quality area of the molten glass, the quality area of the molten glass having athickness within a specified range of less than about 0.5 millimeters across a width of at least about 120 millimeters.

6. The system of any of claims 1-5, wherein an edge director of the one or more edge directors is configured to be replaced by increasing a temperature level at the edge director, moving the edge director away from the molten glass, removing any excess molten glass from the edge director, preheating a replacement edge director, and moving the replacement edge director towards the molten glass until the replacement edge director is at least partially immersed in the molten glass.

7. The system of any of claims 1-6, wherein the contact portion defines a guide slot or a shape that is concave, convex, flat, ridged, multi -jointed, or curved.

8. The system of any of claims 1-7, wherein the one or more edge directors are positioned between about 1 millimeter and about 5 millimeters below the slot.

9. The system of any of claims 1-8, wherein the one or more edge directors comprises a first edge director and a second edge director, wherein the molten glass defines a first edge and a second edge, wherein the first edge director is at least partially immersed in the molten glass proximate to the first edge and the second edge director is at least partially immersed in the molten glass proximate to the second edge.

10. The system of any of claims 1-9, wherein the burner comprises a burner tip where the flame is emitted, and wherein the burner is water cooled.

11. The system of claim 10, wherein each edge director of the one or more edge directors is attached to a water drain.

12. The system of claim 11, further comprising: a burner assembly including the burner, the water drain, and an outer tubing extending from the water drain proximate to the burner tip, wherein the body portion extends upwardly along an incline angle between the burner and the contact portion, wherein the outer tubing is configured to receive water at a portionbetween the burner tip and the water drain, and wherein the water drain is positioned at a lower elevation than the contact portion.

13. The system of claim 12, wherein the burner is configured to generate steam that condenses to form byproduct water, and wherein the byproduct water flows to at least one of the outlet or the water drain.

14. A method for controlling a shape of molten glass, the method comprising: flowing molten glass downwardly out of a slot of a feeder; positioning one or more edge directors relative to the slot, wherein each edge director of the one or more edge directors comprises: a body portion defining a first internal cavity; and a contact portion; and generating a flame at a burner so that heat from the flame causes the molten glass proximate to the one or more edge directors to have a first viscosity that is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass, wherein the one or more edge directors are positioned such that the contact portions are at least partially immersed within and thereby affect the shape of the molten glass.

15. The method of claim 14, wherein positioning the one or more edge directors relative to the slot results in the contact portion being at least partially immersed in the molten glass.

16. The method of claim 15, wherein positioning the one or more edge directors relative to the slot increases a quality area of the molten glass, the quality area of the molten glass having a thickness within a specified range of less than about 0.5 millimeters across a width of at least about 120 millimeters.

17. The method of any of claims 14-16, wherein the one or more edge directors comprises a first edge director, and wherein the method further comprises: increasing a temperature level at the first edge director; moving the first edge director away from the molten glass; removing any excess molten glass from the first edge director; preheating a replacement edge director; andmoving the replacement edge director towards the molten glass until the replacement edge director is at least partially immersed in the molten glass.

18. The method of any of claims 14-17, wherein the contact portion defines a guide slot or a shape that is concave, convex, flat, ridged, multi -jointed, or curved.

19. The method of any of claims 14-18, wherein contact between the contact portion and the molten glass decreases the viscosity of the molten glass.

20. The method of any of claims 14-19, wherein the one or more edge directors are positioned between about 1 millimeter and about 5 millimeters below the slot of the feeder.

21. The method of any of claims 14-20, wherein each edge director of the one or more edge directors comprises an exhaust portion attached to the body portion, the exhaust portion defining a second internal cavity and an outlet, and wherein the first internal cavity, the second internal cavity, and the outlet are in fluid communication with each other, and wherein the body portion extends at least partially along a first axis, the exhaust portion extends at least partially along a second axis, and the first axis is offset at an acute angle relative to the second axis.

22. An edge director for controlling a shape of molten glass, the edge director comprising: a body portion defining a first internal cavity; and a contact portion configured to contact the molten glass, wherein the edge director is positioned such that the contact portion is at least partially immersed within and thereby affects the shape of the molten glass, and wherein the edge director is configured to be positioned relative to a burner such that, upon generation of the flame by the burner, heat from the flame is configured to cause the molten glass proximate to the one or more edge directors to have a first viscosity that is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass.

23. A system for controlling a shape of molten glass, the system comprising: a feeder defining an internal volume and a slot proximate to a bottom portion of the feeder, with the internal volume being connected to the slot and with the internal volumebeing configured to receive the molten glass so that the molten glass exits the feeder at the slot; a burner configured to generate a flame; one or more edge directors positioned relative to the slot, wherein each edge director of the one or more edge directors comprises: a body portion defining a first internal cavity; and a contact portion configured to contact the molten glass, wherein, upon generation of the flame by the burner, heat from the flame is emitted through the first internal cavity towards the contact portion and into the molten glass flowing over the contact portion of the one or more edge directors, wherein the heat from the flame is configured to cause the molten glass proximate to the one or more edge directors to have a first viscosity that is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass, and wherein the contact portion of the one or more edge directors affects the shape of the molten glass so that, across a width of at least about 120 millimeters, a difference between a maximum thickness of the molten glass and a minimum thickness of the molten glass is about 0.5 millimeters or less.

24. A sheet of glass made by a process of flowing molten glass downwardly out of a slot of a feeder; positioning one or more edge directors relative to the slot, wherein each edge director of the one or more edge directors comprises: a body portion defining a first internal cavity; and a contact portion configured to contact the molten glass, wherein the one or more edge directors are positioned such that the contact portion is at least partially immersed within and affects a shape of the molten glass; and generating a flame at the burner so that heat from the flame causes the molten glass proximate to the one or more edge directors to have a first viscosity that is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass.

25. A sheet of glass made by a process of: flowing molten glass downwardly out of a slot of a feeder; positioning one or more edge directors relative to the slot, wherein each edge director of the one or more edge directors comprises:a body portion defining a first internal cavity; and a contact portion configured to contact the molten glass, wherein the one or more edge directors are positioned such that the contact portion is at least partially immersed within and affects a shape of the molten glass; and generating a flame at the burner so that heat from the flame causes the molten glass proximate to the one or more edge directors to have a first viscosity that is greater than a second viscosity of the molten glass proximate to a center portion of the molten glass; and cutting the molten glass to remove a portion of the molten glass at an area proximate to an edge of the molten glass.

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