GLASS MANUFACTURING MACHINES AND METHODS FOR PRODUCING GLASS STRIPS

Abstract

Glassmaking machines include a forming device that defines the path along which the molten material moves in the direction of travel. The forming device includes a flow path through which the molten material exits the forming device. The glassmaking machine includes a temperature control device located adjacent to the flow path and defining the temperature control line. The temperature control line intersects the flow path and changes the temperature of the molten material passing through the flow path. The method for producing glass strips is described.

Description

METHODS AND APPARATUS FOR MANUFACTURING A GLASS RIBBONCROSS 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 / 594624 filed on October 31, 2023, the content of which is relied upon and incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates generally to apparatus and methods for manufacturing a glass ribbon and, more particularly, to methods for manufacturing a glass ribbon using a thermal control device.BACKGROUND

[0003] It is known to manufacture a glass ribbon with a forming device. Conventional forming devices are known to operate to down draw a quantity of molten material from the forming device as the glass ribbon. A flow density of the molten material from the forming device can impact a thickness of the glass ribbon. As such, controlling the flow density of the molten material can assist in controlling the thickness of the glass ribbon.SUMMARY

[0004] The following presents a simplified summary of the disclosure to provide a basic understanding of some aspects described in the detailed description.

[0005] In aspects, a glass manufacturing apparatus can comprise a forming device defining a travel path along which molten material travels in a travel direction. The forming device can comprise a flow passage through which molten material exits the forming device. The glass manufacturing apparatus can comprise a thermal control device positioned adjacent to the flow passage and defining a thermal control path. The thermal control path intersects the flow passage and is configured to alter a temperature of themolten material passing through the flow passage. The thermal control device is spaced a separating distance from the flow passage that is within a range from about 5 millimeters to about 50 millimeters.

[0006] In aspects, the thermal control device comprises a heating device that is configured to increase the temperature of the molten material passing through the flow passage.

[0007] In aspects, the thermal control device comprises a cooling device that is configured to decrease the temperature of the molten material passing through the flow passage.

[0008] In aspects, the travel path lies within a draw plane that intersects the thermal control device.

[0009] In aspects, the thermal control device comprises a first extension portion that extends toward the flow passage. The first extension portion comprises a first hollow chamber through which gas is configured to flow through the first extension portion and along the thermal control path.

[0010] In aspects, the thermal control device comprises a second extension portion that extends toward the flow passage. The second extension portion comprises a second hollow chamber through which gas is configured to flow through the second extension portion and along a second thermal control path. The first extension portion is spaced apart from the second extension portion.

[0011] In aspects, a gas supply apparatus is in fluid communication with the thermal control device. The gas supply apparatus is configured to deliver a gas to the thermal control device.

[0012] In aspects, the molten material is formed into a glass ribbon such that a ratio of an edge thickness of an outer edge of the glass ribbon to a center thickness of a center of the glass ribbon is from about 1 to 4.

[0013] In aspects, a glass manufacturing apparatus comprises a forming device defining a travel path along which molten material travels in a travel direction. The forming device comprises a flow passage through which molten material exits the forming device. The flow passage extends along a passage axis and comprises a non-constant size along the passage axis. The glass manufacturing apparatus comprises a thermal controldevice positioned adjacent to the flow passage and defining a thermal control path. The thermal control path intersects the flow passage and is configured to alter a temperature of a first glass portion of the molten material passing through a first location of the flow passage. The glass manufacturing apparatus comprises a second thermal control device positioned adjacent to the flow passage and spaced apart from the thermal control device. The second thermal control device defines a second thermal control path. The second thermal control path intersects the flow passage and is configured to alter the temperature of a second glass portion of the molten material passing through a second location of the flow passage. The first location is spaced apart from the second location along the passage axis.

[0014] In aspects, the thermal control device comprises a heating device that is configured to increase the temperature of the molten material passing through the flow passage.

[0015] In aspects, the thermal control device comprises a cooling device that is configured to decrease the temperature of the molten material passing through the flow passage.

[0016] In aspects, a first width of the flow passage at the first location is different than a second width of the flow passage at the second location.

[0017] In aspects, the thermal control device comprises a first extension portion comprising a first hollow chamber through which gas flows through the first extension portion and toward the first location of the flow passage. The gas flowing through the first extension portion comprises a first gas temperature and a first flow rate. The second thermal control device comprises a second extension portion comprising a second hollow chamber through which gas flows through the second extension portion and toward the second location of the flow passage. The gas flowing through the second extension portion comprises a second gas temperature and a second flow rate. One or more of the first gas temperature is different than the second gas temperature or the first flow rate is different than the second flow rate.

[0018] In aspects, methods of manufacturing a glass ribbon comprise directing molten material through a flow passage of a forming device. The flow passage extends along a passage axis. Methods comprise positioning a thermal control device adjacent tothe flow passage. The thermal control device comprises a thermal control path. Methods comprise altering a temperature of the molten material passing through the flow passage by directing the thermal control path to intersect the flow passage.

[0019] In aspects, methods comprise delivering a gas from a gas supply apparatus to the thermal control device.

[0020] In aspects, the gas is directed along the thermal control path from the thermal control device toward the molten material.

[0021] In aspects, altering the temperature of the molten material comprises increasing the temperature of the molten material.

[0022] In aspects, altering the temperature of the molten material comprises decreasing the temperature of the molten material.

[0023] In aspects, methods comprise producing the glass ribbon from the molten material. A thickness ratio of an edge thickness of an edge of the glass ribbon to a center thickness of a center of the glass ribbon is within a range from about 1 to about 4.

[0024] In aspects, altering the temperature of the molten material passing through the flow passage comprises reducing a flow density of the molten material passing through a first end portion of the flow passage and a second end portion of the flow passage.

[0025] Additional features and advantages of the aspects disclosed herein will be set forth in the detailed description that follows, and in part will be clear to those skilled in the art from that description or recognized by practicing the aspects described herein, including the detailed description which follows, the claims, as well as the appended drawings. It is to be understood that both the foregoing general description and the following detailed description present aspects intended to provide an overview or framework for understanding the nature and character of the aspects disclosed herein. The accompanying drawings are included to provide further understanding and are incorporated into and constitute a part of this specification. The drawings illustrate various aspects of the disclosure, and together with the description explain the principles and operations thereof.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] These and other features, aspects and advantages are better understood when the following detailed description is read with reference to the accompanying drawings, in which:

[0027] FIG. 1 schematically illustrates example aspects of a glass manufacturing apparatus in accordance with aspects of the disclosure;

[0028] FIG. 2 illustrates a perspective cross-sectional view of the glass manufacturing apparatus along lines 2-2 of FIG. 1 in accordance with aspects of the disclosure;

[0029] FIG. 3 illustrates a side cross-sectional view of the glass manufacturing apparatus along lines 3-3 of FIG. 2 in accordance with aspects of the disclosure;

[0030] FIG. 4 illustrates a side view of the glass manufacturing apparatus along lines 4-4 of FIG. 3 in accordance with aspects of the disclosure;

[0031] FIG. 5 illustrates a top-down view of a forming device along lines 5-5 of FIG. 4 in accordance with aspects of the disclosure; and

[0032] FIG. 6 illustrates a plot of the flow density of molten material along a length of the forming device in accordance with aspects of the disclosure.DETAILED DESCRIPTION

[0033] Aspects will now be described more fully hereinafter with reference to the accompanying drawings in which example aspects are shown. Whenever possible, the same reference numerals are used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as limited to the aspects set forth herein.

[0034] 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, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art.

[0035] Ranges can be expressed herein as from “about” one value, and / or to “about” another value. When such a range is expressed, aspects include from the one value to the other value. Similarly, when values are expressed as approximations by use of theantecedent “about,” it will be understood that the value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0036] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom, upper, lower, etc. - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0037] Unless otherwise expressly stated, it is in no way intended that any methods set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus, specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred in any respect. This holds for any possible non-express basis for interpretation, including matters of logic relative to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of aspects described in the specification.

[0038] As used herein, the singular forms "a," "an" and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a” component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0039] The word “exemplary,” “example,” or various forms thereof are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” or as an “example” should not be construed as preferred or advantageous over other aspects or designs. Furthermore, examples are provided solely for purposes of clarity and understanding and are not meant to limit or restrict the disclosed subject matter or relevant portions of this disclosure in any manner. It can be appreciated that a myriad of additional or alternate examples of varying scope could have been presented but have been omitted for purposes of brevity.

[0040] As used herein, the terms “comprising” and “including”, and variations thereof, shall be construed as synonymous and open-ended, unless otherwise indicated. A list of elements following the transitional phrases comprising or including is a nonexclusive list, such that elements in addition to those specifically recited in the list may also be present.

[0041] The terms “substantial,” “substantially,” and variations thereof as used herein are intended to represent that a described feature is equal or approximately equal to a value or description. For example, a “substantially planar” surface is intended to denote a surface that is planar or approximately planar. Moreover, “substantially” is intended to denote that two values are equal or approximately equal. The term “substantially” may denote values within about 10% of each other, for example, within about 5% of each other, or within about 2% of each other.

[0042] Modifications may be made to the instant disclosure without departing from the scope or spirit of the claimed subject matter. Unless specified otherwise, “first,” “second,” or the like are not intended to imply a temporal aspect, a spatial aspect, an ordering, etc. Rather, such terms are merely used as identifiers, names, etc. for features, elements, items, etc. For example, a first end and a second end generally correspond to end A and end B or two different ends.

[0043] The present disclosure relates to a glass manufacturing apparatus and methods for manufacturing a glass ribbon. Methods and apparatus for manufacturing a glass ribbon from a glass material will now be described by way of example aspects. As schematically illustrated in FIG. 1, in aspects, an exemplary glass manufacturing apparatus 100 can comprise a glass melting and delivery apparatus 102 and a forming device 101 designed to produce a glass ribbon 103 from a quantity of molten material 121. The glass ribbon 103 can comprise a central portion 152 positioned between opposite edge portions (e.g., edge beads) formed along a first outer edge 153 and a second outer edge 155 of the glass ribbon 103, wherein a thickness of the edge portions can be greater than a thickness of the central portion. In this way, molten material can be formed in the glass ribbon 103, with the glass ribbon 103 comprising a first edge bead formed along the first outer edge 153, and a second edge bead formed along the second outer edge 155. Additionally, in aspects, a separated glass ribbon 104 can be separated from the glass ribbon 103 along aseparation path 151 by a glass separator 149 (e.g., scribe, score wheel, diamond tip, laser, etc.).

[0044] In aspects, the glass melting and delivery apparatus 102 can comprise a melting vessel 105 oriented to receive batch material 107 from a storage bin 109. The batch material 107 can be introduced by a batch delivery device 111 powered by a motor 113. In aspects, an optional controller 115 can be operated to activate the motor 113 to introduce a desired amount of batch material 107 into the melting vessel 105, as indicated by arrow 117. The melting vessel 105 can heat the batch material 107 to provide molten material 121. In aspects, a melt probe 119 can be employed to measure a level of molten material 121 within a standpipe 123 and communicate the measured information to the controller 115 by way of a communication line 125.

[0045] Additionally, in aspects, the glass melting and delivery apparatus 102 can comprise a first conditioning station comprising a fining vessel 127 located downstream from the melting vessel 105 and coupled to the melting vessel 105 by way of a first connecting conduit 129. In aspects, molten material 121 can be gravity fed from the melting vessel 105 to the fining vessel 127 by way of the first connecting conduit 129. For example, in aspects, gravity can drive the molten material 121 through an interior pathway of the first connecting conduit 129 from the melting vessel 105 to the fining vessel 127. Additionally, in aspects, bubbles can be removed from the molten material 121 within the fining vessel 127 by various techniques.

[0046] In aspects, the glass melting and delivery apparatus 102 can further comprise a second conditioning station comprising a mixing chamber 131 that can be located downstream from the fining vessel 127. The mixing chamber 131 can be employed to provide a homogenous composition of molten material 121, thereby reducing or eliminating inhomogeneity that may otherwise exist within the molten material 121 exiting the fining vessel 127. As shown, the fining vessel 127 can be coupled to the mixing chamber 131 by way of a second connecting conduit 135. In aspects, molten material 121 can be gravity fed from the fining vessel 127 to the mixing chamber 131 by way of the second connecting conduit 135. For example, in aspects, gravity can drive the molten material 121 through an interior pathway of the second connecting conduit 135 from the fining vessel 127 to the mixing chamber 131.

[0047] Additionally, in aspects, the glass melting and delivery apparatus 102 can comprise a third conditioning station comprising a delivery chamber 133 that can be located downstream from the mixing chamber 131. In aspects, the delivery chamber 133 can condition the molten material 121 to be fed into an inlet conduit 141. For example, the delivery chamber 133 can function as an accumulator and / or flow controller to adjust and provide a consistent flow of molten material 121 to the inlet conduit 141. As shown, the mixing chamber 131 can be coupled to the delivery chamber 133 by way of a third connecting conduit 137. In aspects, molten material 121 can be gravity fed from the mixing chamber 131 to the delivery chamber 133 by way of the third connecting conduit 137. For example, in aspects, gravity can drive the molten material 121 through an interior pathway of the third connecting conduit 137 from the mixing chamber 131 to the delivery chamber 133. As further illustrated, in aspects, a delivery pipe 139 can be positioned to deliver molten material 121 to forming device 101, for example the inlet conduit 141 of the forming device 101. The forming device 101 can comprise a trough (e.g., trough 201 illustrated in FIG. 2) extending along a trough axis 140 between an inlet end 142 and an opposing end 143 of the forming device 101 opposite the inlet end 142. The inlet end 142 is the end of the trough 201 in proximity to the inlet conduit 141 through which the molten material 121 is received. The opposing end 143 is the end farthest from the inlet conduit 141

[0048] By way of illustration, the forming device 101 shown and disclosed below can be provided to fusion draw molten material 121 off a bottom edge, defined as a root 145, of a forming wedge 209 to produce the glass ribbon 103. For example, in aspects, the molten material 121 can be delivered from the inlet conduit 141 to the forming device 101. The molten material 121 can then be formed into the glass ribbon 103 based, in part, on the structure of the forming device 101. For example, as shown, the molten material 121 can be drawn off the bottom edge (e.g., root 145) of the forming device 101 along a draw path extending in a travel direction 154 of the glass manufacturing apparatus 100. In aspects, edge directors 163, 164 can direct the molten material 121 off the forming device 101 and define, in part, a width 108 of the glass ribbon 103. In aspects, the width 108 of the glass ribbon 103 extends between the first outer edge 153 of the glass ribbon 103 and the second outer edge 155 of the glass ribbon 103.

[0049] In aspects, the width 108 of the glass ribbon 103, which extends between the first outer edge 153 of the glass ribbon 103 and the second outer edge 155 of the glass ribbon 103, can be greater than or equal to about 20 millimeters (mm), for example, greater than or equal to about 50 mm, for example, greater than or equal to about 100 mm, for example, greater than or equal to about 500 mm, for example, greater than or equal to about 1000 mm, for example, greater than or equal to about 2000 mm, for example, greater than or equal to about 3000 mm, for example, greater than or equal to about 4000 mm, although other widths less than or greater than the widths mentioned above can be provided in aspects. For example, in aspects, the width 108 can be within a range from about 20 mm to about 4000 mm, for example, within a range from about 50 mm to about 4000 mm, for example, within a range from about 100 mm to about 4000 mm, for example, within a range from about 500 mm to about 4000 mm, for example, within a range from about 1000 mm to about 4000 mm, for example, within a range from about 2000 mm to about 4000 mm, for example, within a range from about 3000 mm to about 4000 mm, for example, within a range from about 20 mm to about 3000 mm, for example, within a range from about 50 mm to about 3000 mm, for example, within a range from about 100 mm to about 3000 mm, for example, within a range from about 500 mm to about 3000 mm, for example, within a range from about 1000 mm to about 3000 mm, for example, within a range from about 2000 mm to about 3000 mm, for example, within a range from about 2000 mm to about 2500 mm, and all ranges and subranges therebetween.

[0050] FIG. 2 shows a cross-sectional perspective view of the forming device 101 along line 2-2 of FIG. 1. In aspects, the forming device 101 can comprise a trough 201 oriented to receive the molten material 121 from the inlet conduit 141. For illustrative purposes, cross-hatching of the molten material 121 is removed from FIG. 2 for clarity. The forming device 101 comprises a pair of weirs 203, 204 defining a flow passage 224 (e.g., opening, slot, etc.) in the trough 201. The forming device 101 comprises a bottom surface 225, which may comprise several shapes (e.g., rounded, substantially planar, etc.), and may extend at least partially between the inlet end 142 and the opposing end 143 (e.g., illustrated in FIG. 1). The bottom surface 225 can at least partially define the trough 201, for example, with the bottom surface 225 extending along a bottom of the trough 201 and the pair of weirs 203, 204 extending along opposing sides of the trough 201. The formingdevice 101 can further comprise the forming wedge 209 comprising a pair of downwardly inclined converging surface portions 207, 208 extending between opposed ends of the forming wedge 209. The pair of downwardly inclined converging surface portions 207, 208 of the forming wedge 209 can converge along the travel direction 154 to intersect along the root 145 (e.g., a bottom edge of the forming wedge 209 where the converging surface portions 207, 208 meet) of the forming device 101. A draw plane 213 of the glass manufacturing apparatus 100 can extend through the root 145 along the travel direction 154. In aspects, the glass ribbon 103 can be drawn in the travel direction 154 along the draw plane 213. As shown, the draw plane 213 can bisect the forming wedge 209 through the root 145 although, in aspects, the draw plane 213 can extend at other orientations relative to the root 145. In aspects, the glass ribbon 103 can move along a travel path 221 that may he within (e.g., may be co-planar with) the draw plane 213 in the travel direction 154

[0051] Additionally, the molten material 121 can flow in a flow direction 156 into and along the trough 201 of the forming device 101. The molten material 121 can then overflow from the trough 201 by passing through the flow passage 224 and flowing over corresponding weirs 203, 204, and downwardly over the outer surfaces 205, 206 of the corresponding weirs 203, 204. In this way, methods can comprise directing molten material through the flow passage 224 of the forming device 101. Respective streams of molten material 121 can then flow along the downwardly inclined converging surface portions 207, 208 of the forming wedge 209 and be drawn off the root 145 of the forming device 101, where the flows converge and fuse into the glass ribbon 103. The glass ribbon 103 can then be drawn along the travel direction 154. In aspects, the glass ribbon 103 comprises one or more states of material based on a vertical location of the glass ribbon 103, i.e., distance from the root 145. For example, at a first location, the glass ribbon 103 can comprise the viscous molten material 121, and at a second location, the glass ribbon 103 can comprise an amorphous solid in a glassy state (e.g., a glass ribbon).

[0052] The glass ribbon 103 comprises a first major surface 215 and a second major surface 216 facing opposite directions and defining a thickness 212 (e.g., average thickness) of the glass ribbon 103 therebetween. In aspects, the thickness 212 of the glass ribbon 103 can be less than or equal to about 2 millimeters (mm), less than or equal toabout 1 millimeter, less than or equal to about 0.5 millimeters, for example, less than or equal to about 300 micrometers (pm), less than or equal to about 200 micrometers, or less than or equal to about 100 micrometers, although other thicknesses may be provided in further aspects. For example, in aspects, the thickness 212 of the glass ribbon 103 can be within a range from about 20 micrometers to about 200 micrometers, within a range from about 50 micrometers to about 750 micrometers, within a range from about 100 micrometers to about 700 micrometers, within a range from about 200 micrometers to about 600 micrometers, within a range from about 300 micrometers to about 500 micrometers, within a range from about 50 micrometers to about 500 micrometers, within a range from about 50 micrometers to about 700 micrometers, within a range from about 50 micrometers to about 600 micrometers, within a range from about 50 micrometers to about 500 micrometers, within a range from about 50 micrometers to about 400 micrometers, within a range from about 50 micrometers to about 300 micrometers, within a range from about 50 micrometers to about 200 micrometers, within a range from about 50 micrometers to about 100 micrometers, within a range from about 25 micrometers to about 125 micrometers, comprising all ranges and subranges of thicknesses therebetween. In addition, the glass ribbon 103 can comprise a variety of compositions, for example, one or more of soda-lime glass, borosilicate glass, alumino-borosilicate glass, alkali-containing glass, alkali-free glass, aluminosilicate, borosilicate, boroaluminosilicate, silicate, glassceramic, or other materials comprising glass. In aspects, the glass ribbon 103 can comprise one or more of lithium fluoride (LiF), magnesium fluoride (MgF2), calcium fluoride (CaF2), barium fluoride (BaF2), sapphire (AI2O3), zinc selenide (ZnSe), germanium (Ge) or other materials.

[0053] In aspects, the glass separator 149 (see FIG. 1) can separate the glass ribbon 104 from the glass ribbon 103 along the separation path 151 to provide a plurality of separated glass ribbons 104 (i.e., a plurality of sheets of glass). In aspects, a longer portion of the glass ribbon 104 may be coiled onto a storage roll. The separated glass ribbon can then be processed into a desired application, e.g., a display application. For example, the separated glass ribbon can be used in a wide range of display and non-display applications comprising, but not limited to, liquid crystal displays (LCDs), electrophoretic displays (EPD), organic light emitting diode displays (OLEDs), plasma display panels (PDPs),microLED displays, miniLED displays, organic light emitting diode lighting, light emitting diode lighting, augmented reality (AR), virtual reality (VR), touch sensors, photovoltaics, foldable phones, or other applications.

[0054] FIG. 3 illustrates a side view of the glass manufacturing apparatus 100 along lines 3-3 of FIG. 2. The forming device 101 can define the travel path 221 along which molten material 121 (e.g., formed into the glass ribbon 103) travels in the travel direction 154. In aspects, methods of manufacturing the glass ribbon 103 can comprise directing the glass ribbon 103 along the travel path 221 in the travel direction 154, for example, with the glass ribbon 103 moving in the direction of gravity. In aspects, the glass manufacturing apparatus 100 can comprise a thermal control device 301 positioned adjacent to the flow passage 224 and configured to alter a temperature of the molten material 121 passing through the flow passage 224. For example, by being adjacent to the flow passage 224, the thermal control device 301 can be in close enough proximity such that the thermal control device 301 can prompt a change in the temperature of the molten material 121 that travels through the flow passage 224, while being spaced a sufficient distance apart from the forming device 101 such that the thermal control device 301 does not contact the molten material 121 and / or the forming device 101. In aspects, the thermal control device 301 can cause a temperature change of the molten material 121 that is less than about 100° Celsius, for example, within a range from about 10° C to about 80° C, or within a range from about 20° C to about 60° C. In aspects, the draw plane 213 can intersect the thermal control device 301, with the thermal control device 301 positioned above the forming device 101 relative to a direction of gravity. The thermal control device 301 can be spaced a separating distance 307 from the flow passage 224 along the draw plane 213, with the separating distance 307 within a range from about 5 millimeters to about 50 millimeters, or about 5 millimeters to about 20 millimeters, or about 10 millimeters to about 20 millimeters. Accordingly, methods can comprise positioning the thermal control device 301 adjacent to the flow passage 224.

[0055] The thermal control device 301 can define a thermal control path 311 that can extend from the thermal control device 301 toward the flow passage 224. In aspects, the thermal control path 311 can form a linear path that extends toward the flow passage 224. A projection 313 of the thermal control path 311 can intersect the flow passage 224such that the thermal control path 311 can alter the temperature of the molten material 121 passing through the flow passage 224. The projection 313 can extend along the thermal control path 311 and may continue beyond an end of the thermal control path 311. In aspects, the thermal control device 301 can comprise a heating device, such that the projection 313 can intersect the flow passage 224 and increase a temperature of the molten material 121 passing through the flow passage 224. That is, when the thermal control device 301 comprises a heating device, the thermal control device 301 can direct heated air or gas along the thermal control path 311, which can heat the molten material 121 passing through the flow passage 224. Alternatively, when the thermal control device 301 comprises a cooling device, the thermal control device 301 can direct cooled air or gas along the thermal control path 311, which can heatthe molten material 121 passing through the flow passage 224. When the thermal control device 301 comprises a laser, the laser beam can extend along the thermal control path 311 such that the projection 313 of the thermal control path 311 (e.g., the laser beam) can intersect the flow passage 224 and alter the temperature of the molten material 121. In this way, increasing the temperature of the molten material 121 can decrease the viscosity of the molten material 121 and increase the mass flow rate of the molten material 121. Conversely, the thermal control device 301 can comprise a cooling device, such that the thermal control path 311 can intersect the flow passage 224 and decrease a temperature of the molten material 121 passing through the flow passage 224. In this way, decreasing the temperature of the molten material 121 can increase the viscosity of the molten material 121 and decrease the mass flow rate of the molten material 121.

[0056] FIG. 4 illustrates a side view of the forming device 101 and the thermal control device 301 as viewed along lines 4-4 of FIG. 3. In aspects, the glass manufacturing apparatus 100 is not limited to comprising a single thermal control device (e.g., the thermal control device 301), but, rather, can comprise a plurality of thermal control devices. For example, the glass manufacturing apparatus 100 can comprise the thermal control device 301, a second thermal control device 401, a third thermal control device 403, etc. In aspects, the thermal control devices 301, 401, 403 can be substantially identical in structure, function, and location (e.g., above the forming device 101), with the thermal control devices 301, 401, 403 configured to alter the temperature of the molten material121 passing through the flow passage 224. The thermal control devices 301, 401, 403 can be spaced apart along a thermal axis 405 that is parallel to the trough axis 140 and lies within the draw plane 213 (e.g., illustrated in FIGS. 2-3). For example, in aspects, the thermal control device 301 can be positioned adjacent to one end of the flow passage 224. The second thermal control device 401 can be positioned adjacent to a center of the flow passage 224 and spaced apart from the thermal control device 301. The third thermal control device 403 can be positioned adjacent to an opposing end of the flow passage 224 and spaced apart from the thermal control devices 301, 401.

[0057] In aspects, and as illustrated in FIG. 4, the thermal control devices 301, 401, 403 can comprise one or more gas nozzles and may direct gas toward the forming device 101. For example, the glass manufacturing apparatus 100 can comprise a gas supply apparatus 407 (e.g., a pump, a cannister, a cartridge, a boiler, a compressor, a pressure vessel, etc.) in fluid communication with the thermal control devices 301, 401, 403. By being in fluid communication, the gas supply apparatus 407 can be attached to the thermal control devices 301, 401, 403 via one or more conduits (e.g., tubes, hoses, pipes) through which gas can be supplied from the gas supply apparatus 407 to the thermal control devices 301, 401, 403. While a single gas supply apparatus 407 is illustrated in fluid communication with the thermal control devices 301, 401, 403, such a design is not intended to be limiting. Rather, in aspects, a plurality of gas supply apparatuses can be provided, with one or more gas supply apparatuses in fluid communication with one or more thermal control devices. Accordingly, in this way, methods can comprise delivering gas from the gas supply apparatus 407 to the thermal control devices 301, 401, 403. The gas can comprise, for example, one or more of air, nitrogen, helium, argon, carbon dioxide, etc.

[0058] In aspects, flow characteristics of the gas supplied to, and delivered from, one thermal control device may differ from flow characteristics of the gas supplied to, and delivered from, a different thermal control device. The flow characteristics can comprise, for example, a temperature of the gas supplied to, and delivered from, the thermal control device(s), a flow rate of the gas supplied to, and delivered from, the thermal control device(s), etc. In this way, one thermal control device can direct gas comprising a first flow characteristic toward the flow passage 224, wherein the first flow characteristic cancomprise a first gas temperature and a first gas flow rate. A second, different thermal control device can direct gas comprising a second flow characteristic toward a different location of the flow passage 224, wherein the second flow characteristic can comprise a second gas temperature and a second gas flow rate. In aspects, the first gas temperature may be the same as or different than the second gas temperature, and the first gas flow rate may be the same as or different than the second gas flow rate. As an example, the thermal control device 301 can direct gas toward the flow passage 224, with the gas comprising the first flow characteristic (e.g., first gas temperature and first gas flow rate), and the second thermal control device 401 can direct gas toward the flow passage 224, with the gas comprising the second flow characteristic (e.g., second gas temperature and second gas flow rate). In aspects, the first gas temperature and the second gas temperature may be the same or different, and the first gas flow rate and the second gas flow rate may be the same or different.

[0059] The thermal control device 301 can comprise a first extension portion 413 that extends toward the flow passage 224. The first extension portion 413 can comprise a first hollow chamber 415 through which gas can flow through the first extension portion 413. The first extension portion 413 may terminate at an end 417, with the first hollow chamber 415 passing through the end 417. In this way, the gas can exit at the end 417 of the first extension portion 413 and may travel along the thermal control path 311 toward the flow passage 224, with the gas impinging upon the molten material 121 at the projection 313. The thermal control paths are illustrated as comprising substantially conical shapes in FIG. 4 due to the gas exiting the extension portions and spreading apart before impinging upon the molten material 121. Methods can comprise directing the gas along the thermal control path 311 from the thermal control device 301 toward the molten material 121. In aspects, the projection 313 of the thermal control path 311 can intersect the flow passage 224 such that the thermal control path 311 can alter a temperature of a first glass portion 423 of the molten material 121 passing through a first location 425 of the flow passage 224. For example, when the thermal control device 301 functions as a heating device, the gas exiting the end 417 of the first extension portion 413 may be at an elevated temperature to increase the temperature of the first glass portion 423 that passes through the first location 425 of the flow passage 224. Alternatively, when the thermal control device 301functions as a cooling device, the gas exiting the end 417 of the first extension portion 413 may be at a reduced temperature to decrease the temperature of the first glass portion 423 that passes through the first location 425 of the flow passage 224. Accordingly, methods can comprise altering the temperature of the molten material 121 passing through the flow passage 224 by directing the thermal control path 311 to intersect the flow passage 224. Altering the temperature of the molten material 121 can comprise increasing or decreasing the temperature of the molten material 121.

[0060] In aspects, the second thermal control device 401 can be substantially similar to the thermal control device 301. For example, the second thermal control device 401 can comprise a second extension portion 427 that extends toward the flow passage 224. The second extension portion 427 can comprise a second hollow chamber 429 through which gas can flow through the second extension portion 427. The gas can exit at an end 431 of the second extension portion 427 and may travel along a second thermal control path 433 toward the flow passage 224. The second thermal control device 401 can define the second thermal control path 433. In aspects, a second projection 435 of the second thermal control path 433 can intersect the flow passage 224 and can alter a temperature of a second glass portion 439 of the molten material 121 passing through a second location 441 of the flow passage 224. For example, when the second thermal control device 401 functions as a heating device, the gas exiting the end 431 of the second extension portion 427 may be at an elevated temperature to increase the temperature of the second glass portion 439 that passes through the second location 441 of the flow passage 224. Alternatively, when the second thermal control device 401 functions as a cooling device, the gas exiting the end 431 of the second extension portion 427 may be at a reduced temperature to decrease the temperature of the second glass portion 439 that passes through the second location 441 of the flow passage 224.

[0061] Accordingly, the temperature of the first glass portion 423 can be altered relative to the second glass portion 439. That is, the temperature change of the first glass portion 423 due to the thermal control device 301 may be independent of the temperature change of the second glass portion 439 due to the second thermal control device 401. For example, the gas flowing through the first extension portion 413 and toward the first location 425 can comprise a first gas temperature and a first flow rate. The gas flowingthrough the second extension portion 427 and toward the second location 441 can comprise a second gas temperature and a second flow rate. In aspects, one or more of the first gas temperature may be different than the second gas temperature, or the first flow rate may be different than the second flow rate. In this way, due to the differing gas temperatures and / or flow rate, the thermal control devices can cause a different temperature change of the molten material 121 at differing locations along the flow passage 224.

[0062] In aspects, the first location 425 and the second location 441 of the flow passage 224 may be spaced apart along a passage axis 445 along which the flow passage 224 extends, with the passage axis 445 substantially parallel to one or more of the trough axis 140 or the thermal axis 405. In this way, the first location 425 and the second location 441 can represent differing axial locations of the flow passage 224 along the passage axis 445. Due to the positioning of the thermal control devices 301, 401, 403 spaced apart along the thermal axis 405, the thermal control devices 301, 401, 403 can control the temperature of the molten material 121 passing through the flow passage 224, by heating or cooling portions of the molten material 121 that exit the flow passage 224 at differing axial locations along the passage axis 445. Accordingly, by heating or cooling the molten material 121 that exits the flow passage 224, the viscosity and mass flow rate of the molten material 121 can be altered at differing locations 425, 441 along the passage axis 445.

[0063] FIG. 5 illustrates a top-down view of the flow passage 224 of the forming device 101 as viewed along lines 5-5 of FIG. 4, wherein a plurality of projections from the thermal control devices 301, 401, 403 intersect the flow passage 224. For example, the flow passage 224 extends along the passage axis 445 between a first end portion 501 and a second end portion 503, and, in aspects, may comprise a non-constant size along the passage axis 445. FIG. 5 illustrates one possible aspect, in which the flow passage 224 can decrease, such as intermittently or continuously decreasing from an intermediate portion 505 of the flow passage 224 to the first end portion 501 and the second end portion 503. For example, the flow passage 224 can comprise a first width 507 at the first end portion 501, a second width 509 at the intermediate portion 505, and a third width 511 at the second end portion 503. The widths 507, 509, 511 can be measured along axes that are substantially perpendicular to the passage axis 445. In the illustrated example of FIG. 5, the first width 507 and the third width 511 may be different than the second width 509, forexample, with the first width 507 and the third width 511 each less than the second width 509. In aspects, the flow passage 224 is not limited to the illustrated non-constant size of FIG. 5. Rather, the flow passage 224 can comprise additional other shapes, for example, a tapered shape that is intermittently or continuously increasing from one end portion (e.g., the first end portion 501) to an opposing end portion (e.g., the second end portion 503). Alternatively, the flow passage 224 can comprise a plurality of separate flow passages that may be aligned along the passage axis 445. Accordingly, depending on a desired thickness of the glass ribbon 103, the flow passage 224 can comprise several different shapes, at least some of which may comprise the non-constant size along the passage axis 445. In aspects, the widths 507, 509, 511 of the flow passage 224 can be within a range from about 1 millimeter to about 10 millimeters.

[0064] As illustrated in FIG. 5, a plurality of projections 313, 435 from the thermal control devices 301, 401, 403 can intersect the flow passage 224. The plurality of projections 313, 435 are illustrated schematically as circles with dashed lines in FIG. 5. The plurality of projections 313, 435 can represent gas from the thermal control devices 301, 401, 403 impinging upon the molten material 121 that passes through the flow passage 224. As such, the plurality of projections 313, 435 can represent the portion of the thermal control paths that intersect the molten material 121. In this way, the thermal control devices 301, 401, 403 can be arranged such that the plurality of projections 313, 435 are spaced apart along the length of the flow passage 224 along the passage axis 445. The plurality of projections 313, 435 (e.g., the thermal control paths) can cause local viscosity changes, and, thus, changes in flow density, in the molten material 121 along the passage axis 445. For example, due to the shape of the flow passage 224 illustrated in FIG. 5, molten material 121 passing through the end portions 501, 503 of the flow passage 224 may have a different flow density (e.g., with higher pressure) than the molten material 121 passing through the intermediate portion 505 of the flow passage 224. This may be due, for example, to the widths 507, 511 at the end portions 501, 503 being less than the second width 509 at the intermediate portion 505. To address the differing flow densities along the passage axis 445, the thermal control devices 301, 401, 403 can direct gas toward the molten material 121 passing through the flow passage 224. The plurality of projections 313, 435 e.g., thethermal control paths) can therefore heat or cool different portions of the molten material 121, which can change the flow density.

[0065] By changing the flow density of the molten material 121, a thickness of the glass ribbon 103 can be controlled. In aspects, the glass ribbon 103 can be formed such that an edge thickness of an outer edge 153, 155 (e.g., illustrated in FIGS. 1-2) of the glass ribbon 103 is different than the center thickness 212 (e.g., illustrated in FIG. 2) of a center of the glass ribbon 103. In aspects, a thickness ratio of the edge thickness to the center thickness 212 may be within a range from about 1 to about 10, or within a range from about 1 to about 5, or within a range from about 1 to about 4. For example, in aspects, the center thickness 212 of the center of the glass ribbon 103 may be within a range from about 50 micrometers to about 80 micrometers, or about 65 micrometers, and the edge thickness of the outer edge 153, 155 of the glass ribbon 103 may be within a range from about 150 micrometers to about 200 micrometers, or about 180 micrometers. Accordingly, in such an example, the thickness ratio of the edge thickness to the center thickness 212 may be about 3. As such, methods can comprise producing the glass ribbon 103 from the molten material 121, wherein a thickness ratio of an edge thickness of one edge 153, 155 of the glass ribbon 103 to the center thickness 212 of the center of the glass ribbon 103 may be within a range from about 1 to about 4.

[0066] While FIGS. 3-5 illustrate the thermal control devices 301, 401, 403 as comprising conduits through which gas can flow and be delivered to the forming device 101, the thermal control devices 301, 401, 403 are not so limited. Rather, in aspects, other possible heating methods can be provided in addition to, or in the alternative to, the illustrated thermal control devices 301, 401, 403. For example, in aspects, the thermal control devices can comprise a laser that can direct a laser beam toward the forming device 101 to heat the molten material 121. In this way, the laser beam can function similarly to the gas, and can alter the temperature of the molten material 121, which can change the flow density of the molten material 121 and, thus, the thickness of the glass ribbon 103. In other aspects, the thermal control devices can comprise one or more heaters (e.g., electric heaters, etc.) that can heat the air surrounding the forming device 101. For example, the heaters can comprise convection heaters or the like that can use convection currents to heatthe air adjacent to the forming device 101, and, thus, alter a temperature of the molten material 121.

[0067] FIG. 6 illustrates a plot 601 of a flow density of the molten material 121 relative to a distance from the inlet end 142 (e.g., illustrated in FIG. 1) of the forming device 101. The distance from the inlet end 142 is represented by the x-axis 603, and a flow density of the molten material 121 is represented by the y-axis 605. With reference to the x-axis 603, the left-most point (e.g., “0”) represents the inlet end 142, and the rightmost point (e.g., “1”) represents the opposing end 143. Line 611 represents a flow density of the molten material 121 at positions along the flow passage 224. Further, line 611 represents the flow densities without the application of the thermal control devices 301, 401, 403 (e.g., with the thermal control devices 301, 401, 403, etc. not operating). Line 613 represents a flow density of the molten material 121 at positions along the flow passage 224 with the application of the thermal control devices 301, 401, 403 (e.g., with the thermal control devices 301, 401, 403, etc. in operation).

[0068] Line 615 represents a difference in flow densities of the molten material 121 at positions along the flow passage 224 between line 611 and line 613. That is, line 615 represents the difference in flow densities with the thermal control devices (e.g., 301, 401, 403, etc.) in operation (e.g., line 613) as opposed to not operating (e.g., line 611). As indicated by line 615, the operation of the thermal control devices (e.g., 301, 401, 403, etc.) can alter the flow density of the molten material 121 passing through the flow passage 224, which is beneficial for several reasons. For example, it may be beneficial to manufacture a glass ribbon 103 with a reduced edge thickness (e.g., bead thickness, etc.) at the outer edges 153, 155. The reduced edge thickness can allow for the glass ribbon 103 to be spooled without the need for removal of the edge beads. The edge thickness (e.g., bead thickness, etc.) may be impacted, at least in part, by the widths 507, 511 of the end portions 501, 503 of the flow passage 224. Further, reducing a flow density of the molten material 121 passing through the end portions 501, 503 can reduce the edge thickness (e.g., bead thickness, etc.) of the glass ribbon 103. For example, for a glass ribbon 103 comprising the center thickness 212 of about 65 micrometers, it may be beneficial for the edge thickness at the outer edges 153, 155 to be about 180 micrometers, with a bead-to-center thickness ratio of about 3.0 (e.g., 180 / 65). To further reduce the flow density of the moltenmaterial 121 passing through the end portions 501, 503, the thermal control devices (e.g., 301, 401, 403, etc.) can be operated to alter a temperature of the molten material 121 passing through the end portions 501, 503. As indicated by line 615 of the plot 601, the operation of the thermal control devices (e.g., 301, 401, 403, etc.) can reduce the flow densities via a change in temperature of the molten material 121. In aspects, a difference in a center flow density of the molten material 121 at a center (e.g., at “0.5”) of the flow passage 224 and an end flow density of the molten material 121 at an end (e.g., at “0”) of the flow passage 224 may be less than about 2, or less than about 1, or about 0.7. Accordingly, methods can comprise reducing a flow density of the molten material 121 passing through the first end portion 501 of the flow passage 224 and the second end portion 503 of the flow passage 224.

[0069] It has been determined that as the end-to-center flow density ratio decreases, the bead-to- center thickness ratio may likewise be decreased, which can allow for the edge thickness (e.g., bead thickness, etc.) of the glass ribbon 103 to be decreased. For example, experimental modeling using the thermal control devices (e.g., 301, 401, 403, etc.) has predicted a bead-to-center thickness ratio based on an end-to-center flow ratio of the molten material 121. The end-to-center flow ratio is the ratio of the flow density of the molten material 121 at an end portion 501, 503 to the flow density at the intermediate portion 505. Experimental modeling using the thermal control devices (e.g., 301, 401, 403, etc.) has predicted that, for an end-to-center flow ratio of about 1.0, the bead-to-center thickness ratio is about 7.2. Experimental modeling using the thermal control devices (e.g., 301, 401, 403, etc.) has predicted that, for an end-to-center flow ratio of about 0.5, the bead-to-center thickness ratio is about 5.7. Experimental modeling using the thermal control devices (e.g., 301, 401, 403, etc.) has predicted that, for an end-to-center flow ratio of about 0.3, the bead-to-center thickness ratio is about 4.9. Experimental modeling using the thermal control devices (e.g., 301, 401, 403, etc.) has predicted that, for an end-to-center flow ratio of about 0.1, the bead-to-center thickness ratio is about 4.2. Accordingly, the thermal control devices (e.g., 301, 401, 403, etc.) can alter the flow density of the molten material 121, which can likewise alter the end-to-center flow ratio of the molten material 121. By altering the end-to-center flow ratio, the bead-to-center thickness ratio can becorrespondingly changed, which can, in aspects, reduce the edge thickness of the glass ribbon 103.

[0070] Another benefit of the present application is that the thermal control devices (e.g., 301, 401, 403, etc.) allow for tunability of the thickness of the glass ribbon 103 after the formation of the forming device 101. For example, after the formation of the forming device 101 and the flow passage 224, it may be difficult to subsequently alter the dimensions (e.g., widths 507, 509, 511, shape, etc.) of the flow passage 224. However, by providing the thermal control devices (e.g., 301, 401, 403, etc.) which can alter the temperature of the molten material 121, the flow density of the molten material 121 can be changed, which can change the thickness of the glass ribbon 103. In this way, a flow passage with pre-existing dimensions can produce a glass ribbon of varying thickness profiles due to the use of the thermal control devices (e.g., 301, 401, 403, etc.). Further, the thickness profile of the glass ribbon 103 can be adjusted after the glass manufacturing process has started by changing the flow characteristics of the thermal control devices (e.g. , 301, 401, 403, etc )

[0071] It should be understood that while various aspects have been described in detail relative to certain illustrative and specific examples thereof, the present disclosure should not be considered limited to such, as numerous modifications and combinations of the disclosed features are possible without departing from the scope of the following claims.

Claims

What is claimed is:

1. A glass manufacturing apparatus comprising: a forming device defining a travel path along which molten material travels in a travel direction, the forming device comprising a flow passage through which molten material exits the forming device; and a thermal control device positioned adjacent to the flow passage and defining a thermal control path, the thermal control path intersecting the flow passage and configured to alter a temperature of the molten material passing through the flow passage, the thermal control device spaced a separating distance from the flow passage that is within a range from about 5 millimeters to about 50 millimeters.

2. The glass manufacturing apparatus of claim 1, wherein the thermal control device comprises a heating device that is configured to increase the temperature of the molten material passing through the flow passage.

3. The glass manufacturing apparatus of claim 1, wherein the thermal control device comprises a cooling device that is configured to decrease the temperature of the molten material passing through the flow passage.

4. The glass manufacturing apparatus of any one of claims 1-3, wherein the travel path lies within a draw plane that intersects the thermal control device.

5. The glass manufacturing apparatus of any one of claims 1-4, wherein the thermal control device comprises a first extension portion that extends toward the flow passage, the first extension portion comprising a first hollow chamber through which gas is configured to flow through the first extension portion and along the thermal control path.

6. The glass manufacturing apparatus of any one of claims 1-5, wherein the thermal control device comprises a second extension portion that extends toward the flow passage, the second extension portion comprising a second hollow chamber throughwhich gas is configured to flow through the second extension portion and along a second thermal control path, the first extension portion spaced apart from the second extension portion.

7. The glass manufacturing apparatus of any one of claims 5-6, further comprising a gas supply apparatus in fluid communication with the thermal control device, the gas supply apparatus configured to deliver a gas to the thermal control device.

8. The glass manufacturing apparatus of any one of claims 1-7, wherein the molten material is formed into a glass ribbon such that a ratio of an edge thickness of an outer edge of the glass ribbon to a center thickness of a center of the glass ribbon is from about 1 to 4.

9. A glass manufacturing apparatus comprising: a forming device defining a travel path along which molten material travels in a travel direction, the forming device comprising a flow passage through which molten material exits the forming device, the flow passage extending along a passage axis and comprising a non-constant size along the passage axis; a thermal control device positioned adjacent to the flow passage and defining a thermal control path, the thermal control path intersecting the flow passage and configured to alter a temperature of a first glass portion of the molten material passing through a first location of the flow passage; and a second thermal control device positioned adjacent to the flow passage and spaced apart from the thermal control device, the second thermal control device defining a second thermal control path, the second thermal control path intersecting the flow passage and configured to alter the temperature of a second glass portion of the molten material passing through a second location of the flow passage, the first location spaced apart from the second location along the passage axis.

10. The glass manufacturing apparatus of claim 9, wherein the thermal control device comprises a heating device that is configured to increase the temperature of the molten material passing through the flow passage.

11. The glass manufacturing apparatus of claim 9, wherein the thermal control device comprises a cooling device that is configured to decrease the temperature of the molten material passing through the flow passage.

12. The glass manufacturing apparatus of claim 10, wherein a first width of the flow passage at the first location is different than a second width of the flow passage at the second location.

13. The glass manufacturing apparatus of any one of claims 9-12, wherein: the thermal control device comprises a first extension portion comprising a first hollow chamber through which gas flows through the first extension portion and toward the first location of the flow passage, the gas flowing through the first extension portion comprising a first gas temperature and a first flow rate; and the second thermal control device comprises a second extension portion comprising a second hollow chamber through which gas flows through the second extension portion and toward the second location of the flow passage, the gas flowing through the second extension portion comprising a second gas temperature and a second flow rate, wherein one or more of the first gas temperature is different than the second gas temperature or the first flow rate is different than the second flow rate.

14. A method of manufacturing a glass ribbon comprising: directing molten material through a flow passage of a forming device, the flow passage extending along a passage axis; positioning a thermal control device adjacent to the flow passage, the thermal control device comprising a thermal control path; and altering a temperature of the molten material passing through the flow passage by directing the thermal control path to intersect the flow passage.

15. The method of claim 14, further comprising delivering a gas from a gas supply apparatus to the thermal control device.

16. The method of claim 15, wherein the gas is directed along the thermal control path from the thermal control device toward the molten material.

17. The method of any one of claims 14-16, wherein altering the temperature of the molten material comprises increasing the temperature of the molten material.

18. The method of any one of claims 14-16, wherein altering the temperature of the molten material comprises decreasing the temperature of the molten material.

19. The method of any one of claims 14-17, further comprising producing the glass ribbon from the molten material, wherein a thickness ratio of an edge thickness of an edge of the glass ribbon to a center thickness of a center of the glass ribbon is within a range from about 1 to about 4.

20. The method of claim 19, wherein altering the temperature of the molten material passing through the flow passage comprises reducing a flow density of the molten material passing through a first end portion of the flow passage and a second end portion of the flow passage.

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