WO2021162890A1

WO2021162890A1 - Apparatus and method for improving electrical current flow in glass melt conduit

Info

Publication number: WO2021162890A1
Application number: PCT/US2021/016163
Authority: WO
Inventors: Brian Douglas Burns
Original assignee: Corning Incorporated
Priority date: 2020-02-13
Filing date: 2021-02-02
Publication date: 2021-08-19
Also published as: TW202136161A

Abstract

An apparatus and method for processing molten glass includes an electrically heated conduit configured to circumferentially surround the molten glass and an electrical conductor proximate the electrically heated conduit. The method includes flowing an electric current through an electrical conductor proximate the electrically heated conduit such that the flow of electric current through the electrical conductor affects a density of electric current flowing through at least a portion of the electrically heated conduit.

Description

APPARATUS AND METHOD FOR IMPROVING ELECTRICAL CURRENT FLOW IN

GLASS MELT CONDUIT

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial no. 62/976,092 filed on February 13, 2020, the content of which is incorporated herein by reference in its entirety.

Field

[0002] The present disclosure relates generally to improving electrical current flow in conduits, such as metal conduits used in glass melt systems.

Background

[0003] In the production of glass articles, such as glass sheets for display applications, including televisions and hand-held devices, such as telephones and tablets, molten material is typically transported through one or more conduits, such as conduits comprised of a precious metal, such as platinum. Such conduits can be directly heated, for example, by an electrically powered flange comprising a metallic material that circumferentially surrounds the conduit.

[0004] In such systems, electrical current density can be unevenly distributed within the conduit material, resulting in relatively hotter conduit regions, sometimes referred to as “hot spots.” Over time, conduit material in the vicinity of such “hot spots” can degrade, resulting in the need to repair or replace the conduit material as well as processing down time. Accordingly, it would be desirable to reduce the need to repair or replace conduit material that can result from uneven current density in conduit materials used in glass melting systems.

SUMMARY

[0005] Embodiments disclosed herein include an apparatus for processing molten glass. The apparatus includes an electrically heated conduit configured to circumferentially surround the molten glass. The apparatus also includes an electrical conductor proximate the electrically heated conduit. The electrical conductor is configured to flow an electric current therethrough, such that the flow of electric current affects a density of electric current flowing through a portion of the electrically heated conduit.

[0006] Embodiments disclosed herein also include a method for processing molten glass. The method includes circumferentially surrounding the molten glass with an electrically heated conduit. The method also includes flowing an electric current through an electrical conductor proximate the electrically heated conduit such that the flow of electric current affects a density of electric current flowing through a portion of the electrically heated conduit.

[0007] Additional features and advantages of the embodiments disclosed herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the disclosed embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0008] It is to be understood that both the foregoing general description and the following detailed description present embodiments intended to provide an overview or framework for understanding the nature and character of the claimed embodiments. The accompanying drawings are included to provide further understanding and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure, and together with the description serve to explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. l is a schematic view of an example fusion down draw glass making apparatus and process;

[0010] FIG. 2 is a schematic perspective view of a conduit circumferentially surrounded by annular heating elements;

[0011] FIG. 3 A is a schematic perspective view illustrating current density in an electrical conductor;

[0012] FIGS. 3B and 3C are schematic perspective views illustrating current density in proximate conductors;

[0013] FIGS. 4A and 4B are schematic perspective views of current density in a conduit as affected by proximate electrical conductors; [0014] FIG. 5 is a schematic side view of an electrically heated conduit and an electrical conductor proximate the electrically heated conduit;

[0015] FIG. 6 is schematic side view of an electrically heated conduit and electrical conductors proximate the electrically heated conduit;

[0016] FIG. 7 is schematic side view of an electrically heated conduit and electrical conductors proximate the electrically heated conduit;

[0017] FIG. 8 is a schematic side view of an electrically heated conduit and an electrical conductor proximate the electrically heated conduit;

[0018] FIG. 9 is schematic side view of an electrically heated conduit and electrical conductors proximate the electrically heated conduit;

[0019] FIG. 10 is schematic side view of an electrically heated conduit and electrical conductors proximate the electrically heated conduit;

[0020] FIG. 11 is a schematic perspective view of an electrical conductor comprising an inner channel having a cooling fluid flowing therethrough; and [0021] FIG. 12 is a schematic view of an electrically heated conduit, an electrical conductor proximate the electrically heated conduit, and a feedback control mechanism that controls flow of electric current through the electrical conductor in response to at least one condition measured by condition measuring devices.

DETAILED DESCRIPTION

[0022] Reference will now be made in detail to the present preferred embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be 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 embodiments set forth herein.

[0023] Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, for example by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. 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. [0024] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0025] Unless otherwise expressly stated, it is in no way intended that any method 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 with respect 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 embodiments described in the specification.

[0026] As used herein, the singular forms "a," "an" and "the" include plural referents 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.

[0027] Shown in FIG. 1 is an exemplary glass manufacturing apparatus 10. In some examples, the glass manufacturing apparatus 10 can comprise a glass melting furnace 12 that can include a melting vessel 14. In addition to melting vessel 14, glass melting furnace 12 can optionally include one or more additional components such as heating elements (e.g., combustion burners or electrodes) that heat raw materials and convert the raw materials into molten glass. In further examples, glass melting furnace 12 may include thermal management devices (e.g., insulation components) that reduce heat lost from a vicinity of the melting vessel. In still further examples, glass melting furnace 12 may include electronic devices and/or electromechanical devices that facilitate melting of the raw materials into a glass melt. Still further, glass melting furnace 12 may include support structures (e.g., support chassis, support member, etc.) or other components.

[0028] Glass melting vessel 14 is typically comprised of refractory material, such as a refractory ceramic material, for example a refractory ceramic material comprising alumina or zirconia. In some examples glass melting vessel 14 may be constructed from refractory ceramic bricks. Specific embodiments of glass melting vessel 14 will be described in more detail below.

[0029] In some examples, the glass melting furnace may be incorporated as a component of a glass manufacturing apparatus to fabricate a glass substrate, for example a glass ribbon of a continuous length. In some examples, the glass melting furnace of the disclosure may be incorporated as a component of a glass manufacturing apparatus comprising a slot draw apparatus, a float bath apparatus, a down-draw apparatus such as a fusion process, an up- draw apparatus, a press-rolling apparatus, a tube drawing apparatus or any other glass manufacturing apparatus that would benefit from the aspects disclosed herein. By way of example, FIG. 1 schematically illustrates glass melting furnace 12 as a component of a fusion down-draw glass manufacturing apparatus 10 for fusion drawing a glass ribbon for subsequent processing into individual glass sheets.

[0030] The glass manufacturing apparatus 10 (e.g., fusion down-draw apparatus 10) can optionally include an upstream glass manufacturing apparatus 16 that is positioned upstream relative to glass melting vessel 14. In some examples, a portion of, or the entire upstream glass manufacturing apparatus 16, may be incorporated as part of the glass melting furnace 12

[0031] As shown in the illustrated example, the upstream glass manufacturing apparatus 16 can include a storage bin 18, a raw material delivery device 20 and a motor 22 connected to the raw material delivery device. Storage bin 18 may be configured to store a quantity of raw materials 24 that can be fed into melting vessel 14 of glass melting furnace 12, as indicated by arrow 26. Raw materials 24 typically comprise one or more glass forming metal oxides and one or more modifying agents. In some examples, raw material delivery device 20 can be powered by motor 22 such that raw material delivery device 20 delivers a predetermined amount of raw materials 24 from the storage bin 18 to melting vessel 14. In further examples, motor 22 can power raw material delivery device 20 to introduce raw materials 24 at a controlled rate based on a level of molten glass sensed downstream from melting vessel 14. Raw materials 24 within melting vessel 14 can thereafter be heated to form molten glass 28.

[0032] Glass manufacturing apparatus 10 can also optionally include a downstream glass manufacturing apparatus 30 positioned downstream relative to glass melting furnace 12. In some examples, a portion of downstream glass manufacturing apparatus 30 may be incorporated as part of glass melting furnace 12. In some instances, first connecting conduit 32 discussed below, or other portions of the downstream glass manufacturing apparatus 30, may be incorporated as part of glass melting furnace 12. Elements of the downstream glass manufacturing apparatus, including first connecting conduit 32, may be formed from a precious metal. Suitable precious metals include platinum group metals selected from the group of metals consisting of platinum, iridium, rhodium, osmium, ruthenium and palladium, or alloys thereof. For example, downstream components of the glass manufacturing apparatus may be formed from a platinum-rhodium alloy including from about 70 to about 90% by weight platinum and about 10% to about 30% by weight rhodium. However, other suitable metals can include molybdenum, palladium, rhenium, tantalum, titanium, tungsten and alloys thereof.

[0033] Downstream glass manufacturing apparatus 30 can include a first conditioning (i.e., processing) vessel, such as fining vessel 34, located downstream from melting vessel 14 and coupled to melting vessel 14 by way of the above-referenced first connecting conduit 32. In some examples, molten glass 28 may be gravity fed from melting vessel 14 to fining vessel 34 by way of first connecting conduit 32. For instance, gravity may cause molten glass 28 to pass through an interior pathway of first connecting conduit 32 from melting vessel 14 to fining vessel 34. It should be understood, however, that other conditioning vessels may be positioned downstream of melting vessel 14, for example between melting vessel 14 and fining vessel 34. In some embodiments, a conditioning vessel may be employed between the melting vessel and the fining vessel wherein molten glass from a primary melting vessel is further heated to continue the melting process or cooled to a temperature lower than the temperature of the molten glass in the melting vessel before entering the fining vessel.

[0034] Bubbles may be removed from molten glass 28 within fining vessel 34 by various techniques. For example, raw materials 24 may include multivalent compounds (i.e. fining agents) such as tin oxide that, when heated, undergo a chemical reduction reaction and release oxygen. Other suitable fining agents include without limitation arsenic, antimony, iron and cerium. Fining vessel 34 is heated to a temperature greater than the melting vessel temperature, thereby heating the molten glass and the fining agent. Oxygen bubbles produced by the temperature-induced chemical reduction of the fining agent(s) rise through the molten glass within the fining vessel, wherein gases in the molten glass produced in the melting furnace can diffuse or coalesce into the oxygen bubbles produced by the fining agent. The enlarged gas bubbles can then rise to a free surface of the molten glass in the fining vessel and thereafter be vented out of the fining vessel. The oxygen bubbles can further induce mechanical mixing of the molten glass in the fining vessel. [0035] Downstream glass manufacturing apparatus 30 can further include another conditioning vessel such as a mixing vessel 36 for mixing the molten glass. Mixing vessel 36 may be located downstream from the fining vessel 34. Mixing vessel 36 can be used to provide a homogenous glass melt composition, thereby reducing cords of chemical or thermal inhomogeneity that may otherwise exist within the fined molten glass exiting the fining vessel. As shown, fining vessel 34 may be coupled to mixing vessel 36 by way of a second connecting conduit 38. In some examples, molten glass 28 may be gravity fed from the fining vessel 34 to mixing vessel 36 by way of second connecting conduit 38. For instance, gravity may cause molten glass 28 to pass through an interior pathway of second connecting conduit 38 from fining vessel 34 to mixing vessel 36. It should be noted that while mixing vessel 36 is shown downstream of fining vessel 34, mixing vessel 36 may be positioned upstream from fining vessel 34. In some embodiments, downstream glass manufacturing apparatus 30 may include multiple mixing vessels, for example a mixing vessel upstream from fining vessel 34 and a mixing vessel downstream from fining vessel 34. These multiple mixing vessels may be of the same design, or they may be of different designs.

[0036] Downstream glass manufacturing apparatus 30 can further include another conditioning vessel such as delivery vessel 40 that may be located downstream from mixing vessel 36. Delivery vessel 40 may condition molten glass 28 to be fed into a downstream forming device. For instance, delivery vessel 40 can act as an accumulator and/or flow controller to adjust and/or provide a consistent flow of molten glass 28 to forming body 42 by way of exit conduit 44. As shown, mixing vessel 36 may be coupled to delivery vessel 40 by way of third connecting conduit 46. In some examples, molten glass 28 may be gravity fed from mixing vessel 36 to delivery vessel 40 by way of third connecting conduit 46. For instance, gravity may drive molten glass 28 through an interior pathway of third connecting conduit 46 from mixing vessel 36 to delivery vessel 40.

[0037] Downstream glass manufacturing apparatus 30 can further include forming apparatus 48 comprising the above-referenced forming body 42 and inlet conduit 50. Exit conduit 44 can be positioned to deliver molten glass 28 from delivery vessel 40 to inlet conduit 50 of forming apparatus 48. For example, exit conduit 44 may be nested within and spaced apart from an inner surface of inlet conduit 50, thereby providing a free surface of molten glass positioned between the outer surface of exit conduit 44 and the inner surface of inlet conduit 50. Forming body 42 in a fusion down draw glass making apparatus can comprise a trough 52 positioned in an upper surface of the forming body and converging forming surfaces 54 that converge in a draw direction along a bottom edge 56 of the forming body. Molten glass delivered to the forming body trough via delivery vessel 40, exit conduit 44 and inlet conduit 50 overflows side walls of the trough and descends along the converging forming surfaces 54 as separate flows of molten glass. The separate flows of molten glass join below and along bottom edge 56 to produce a single ribbon of glass 58 that is drawn in a draw or flow direction 60 from bottom edge 56 by applying tension to the glass ribbon, such as by gravity, edge rolls 72 and pulling rolls 82, to control the dimensions of the glass ribbon as the glass cools and a viscosity of the glass increases. Accordingly, glass ribbon 58 goes through a visco-elastic transition and acquires mechanical properties that give the glass ribbon 58 stable dimensional characteristics. Glass ribbon 58 may, in some embodiments, be separated into individual glass sheets 62 by a glass separation apparatus 100 in an elastic region of the glass ribbon. A robot 64 may then transfer the individual glass sheets 62 to a conveyor system using gripping tool 65, whereupon the individual glass sheets may be further processed. [0038] FIG. 2 shows a perspective view of a conduit, which, in FIG. 2, is shown as fining vessel 34, although embodiments disclosed herein can apply to any of the conduits illustrated in FIG. 1 (e.g., first connecting conduit 32, second connecting conduit 38, third connecting conduit 46) as well as any electrically conductive conduit used in a glass melting system. A portion of conduit or fining vessel 34 is circumferentially surrounded by annular heating elements 134, which are in electrical communication with a power source (shown as 302 in FIG. 11) via electrical connectors 136 in order to provide power to annular heating elements 134, which, in turn, electrically heat conduit or fining vessel 34. In certain exemplary embodiments, annular heating elements 134 may comprise the same or similar materials as conduit or fining vessel 34. For example, when conduit or fining vessel 34 comprises platinum or an alloy thereof, annular heating elements 134 may also comprise platinum or an alloy thereof. Annular heating elements 134 may also comprise other materials, for example, at least one of nickel, copper, and alloys comprising at least one of nickel, copper, rhodium, palladium, and platinum.

[0039] In operation, electrically heated conduit or fining vessel 34 circumferentially surrounds molten glass. Resistive heating of annular heating elements 134 causes electric current to flow through conduit or fining vessel 34, resulting in electrical heating of conduit or fining vessel 34 as well as heating of molten glass that is circumferentially surrounded by conduit or fining vessel 34. Uneven distribution of electric current in conduit or fining vessel 34 can result in areas of relatively high electric current density (e.g., shown as areas “A” in FIG. 2) as well as areas of relatively low electric current density (e.g., shown as areas “B” in FIG. 2) flowing through conduit or fining vessel 34. Areas of relatively high current density can cause relatively hotter conduit regions, sometimes referred to as “hot spots.” Over time, conduit material in the vicinity of such “hot spots” can degrade, resulting in the need to repair or replace such material.

[0040] Distribution of current with an electrical conductor can be affected by several types of phenomena. For example, in systems employing alternating current (AC), electric current density can be impacted by internal electric and magnetic fields that force current away from the center of the conductor and towards an outer surface, as shown, for example, in FIG. 3 A, where arrows show current (“I”) being directed toward outer surface of conductor 100, the shaded area representing a region of relatively high electric current density. This phenomena is sometimes referred to as “skin effect” (d):

wherein, m represents the magnetic permeability of the conductor, p represents the electrical resistivity of the conductor, and /represents the AC frequency.

[0041] In systems employing AC, electric current density can also be impacted by a change in electrical resistance due to external magnetic fields and induced eddy currents generated by proximate electrical conductors, sometimes referred to as “proximity effect.” For example, when two proximate electrical conductors carry current in the same direction, current is directed toward opposite sides of the conductors, as shown, for example, in FIG.

3B, where arrows show current (“I”) being directed toward opposite sides of proximate conductors 100 and 102, the shaded areas representing regions of relatively high current density. Conversely, when two proximate electrical conductors carry current in opposite directions, current is directed toward proximate sides of proximate conductors, as shown, for example, in FIG. 3C, where arrows show current (“I”) being directed toward proximate sides of conductors 100 and 102, the shaded areas representing regions of relatively high current density.

[0042] Accordingly, current density in a target electrical conductor can be manipulated by one or more proximate electrical conductors that can be independently operated to carry current in the same or different direction as the current flowing through the target electrical conductor. For example, in systems employing AC, current density in a target electrical conductor can be manipulated by one or more proximate electrical conductors that can be independently operated to carry current in phase or 180 degrees out of phase with the current flowing through the target electrical conductor. [0043] For example, FIG. 4A shows a schematic perspective view of a target electrical conductor 110 and proximate electrical conductors 112 and 114, wherein electrical current (“I”) is flowing in the same direction (or in phase) in the target electrical conductor 110 and the proximate electrical conductors 112 and 114. Such configuration can draw current density toward the opposite side of the target electrical conductor 110 as the proximate electrical conductors 112 and 114, as represented by the shaded area.

[0044] By comparison, FIG. 4B shows a schematic perspective view of a target electrical conductor 110 and proximate electrical conductors 112 and 114, wherein electrical current (“I”) is flowing in the opposite direction (or 180 degrees out of phase) in the target electrical conductor 110 as compared to the proximate electrical conductors 112 and 114. Such configuration can draw current density toward the same side of the target electrical conductor 110 as the proximate electrical conductors 112 and 114, as represented by the shaded area. [0045] FIGS. 5-10 illustrate schematic side views of various configurations of an electrically heated conduit and at least one electrical conductor proximate the electrically heated conduit. Specifically, FIG. 5 illustrates a schematic side view of an electrically heated conduit (fining vessel 34) and an electrical conductor 200 proximate the fining vessel 34, wherein a portion of the electrical conductor 200 extends along an axial distance between annular heating elements 134 and is on the same side of fining vessel 34 as electrical connectors 136.

[0046] FIG. 6 illustrates a schematic side view of an electrically heated conduit (fining vessel 34) and two electrical conductors 202 and 204 proximate the fining vessel 34, wherein a portion of each electrical conductor 202 and 204 extends along an axial distance between annular heating elements 134 and is on the same side of fining vessel 34 as electrical connectors 136.

[0047] FIG. 7 illustrates a schematic side view of an electrically heated conduit (fining vessel 34) and three electrical conductors 202, 204, and 206 proximate the fining vessel 34, wherein a portion of each electrical conductor 202, 204, and 206 extends along an axial distance between annular heating elements 134 and is on the same side of fining vessel 34 as electrical connectors 136.

[0048] FIG. 8 illustrates a schematic side view of an electrically heated conduit (fining vessel 34) and an electrical conductor 200 proximate the fining vessel 34, wherein a portion of the electrical conductor 200 extends along an axial distance between annular heating elements 134 and is on the opposite side of fining vessel 34 as electrical connectors 136. [0049] FIG. 9 illustrates a schematic side view of an electrically heated conduit (fining vessel 34) and two electrical conductors 202 and 204 proximate the fining vessel 34, wherein a portion of each electrical conductor 202 and 204 extends along an axial distance between annular heating elements 134 and is on the opposite side of fining vessel 34 as electrical connectors 136.

[0050] FIG. 7 illustrates a schematic side view of an electrically heated conduit (fining vessel 34) and three electrical conductors 202, 204, and 206 proximate the fining vessel 34, wherein a portion of each electrical conductor 202, 204, and 206 extends along an axial distance between annular heating elements 134 and is on the opposite side of fining vessel 34 as electrical connectors 136.

[0051] In operation, the direction of flow of electrical current in the proximate electrical conductors of the exemplary embodiments illustrated in FIGS. 5-10 can be a function of areas of relatively high or low electric current density flowing through the electrically heated conduit in the absence of any current flowing through the proximate electrical conductor or conductors.

[0052] For example, embodiments disclosed herein include those in which the electrical conductor is positioned proximate an area of relatively low electric current density flowing through the electrically heated conduit (i.e., in absence of any current flowing through the proximate electrical conductor) and is configured to flow electric current in an opposite direction (or 180 degrees out of phase) as electric current flowing through the electrically heated conduit. This has the effect of redistributing the current density toward the area of relatively low electric current density flowing through the electrically heated conduit such that the electric current density flowing through the electrically heated conduit is more evenly distributed.

[0053] Similarly, embodiments disclosed herein include those in which the electrical conductor is positioned proximate an area of relatively high electric current density flowing through the electrically heated conduit (i.e., in absence of any current flowing through the proximate electrical conductor) and is configured to flow electric current in the same direction (or in phase) as electric current flowing through the electrically heated conduit.

This also has the effect of redistributing the current density toward the area of relatively low electric current density flowing through the electrically heated conduit such that the electric current density flowing through the electrically heated conduit is more evenly distributed. [0054] For example, in the embodiments illustrated in FIGS. 5-10, if one or more areas of relatively high electric current density flowing through the electrically heated conduit (fining vessel 34) are on the same side of fining vessel 34 as electrical connectors 136 (as shown, for example, as areas “A” in FIG. 2) and/or one or more areas of relatively low electric current density flowing through the electrically heated conduit (fining vessel 34) are on the opposite side of fining vessel 34 as electrical connectors 136 (as shown, for example, as areas “B” in FIG. 2), then electrical conductors 200, 202, 204, and/or 206 that are also on the same side of fining vessel 34 as electrical connectors 136 (as illustrated in FIGS. 5-7) can flow electric current in the same direction (or in phase) as electric current flowing through the fining vessel 34.

[0055] Similarly, if one or more areas of relatively high electric current density flowing through the electrically heated conduit (fining vessel 34) are on the same side of fining vessel 34 as electrical connectors 136 (as shown, for example, as areas “A” in FIG. 2) and/or one or more areas of relatively low electric current density flowing through the electrically heated conduit (fining vessel 34) are on the opposite side of fining vessel 34 as electrical connectors 136 (as shown, for example, as areas “B” in FIG. 2), then electrical conductors 200, 202, 204, and/or 206 that are on the opposite side of fining vessel 34 as electrical connectors 136 (as illustrated in FIGS. 8-10) can flow electric current in the opposite direction (or 180 degrees out of phase) as electric current flowing through the fining vessel 34.

[0056] In embodiments where two or more electrical conductors are proximate the electrically heated conduit, such as shown, for example, in FIGS. 6-7 and 9-10, flow of electric current through at least one electrical conductor can be different than the flow of electric current through at least one other electrical conductor. For example, in the embodiments illustrated in FIGS. 6-7 and 9-10, the flow of electric current through at least one of electrical conductors 202, 204, and/or 206 can be different than the flow of electric current through at least one other of electrical conductors 202, 204, and/or 206. This can, for example, be in response to relative differences in current density along axial length of electrically heated conduit (e.g., fining vessel 34).

[0057] Embodiments disclosed herein include those in which at least one electrical conductor, such as at least one of electrical conductors 200, 202, 204, and /or 206, is configured to flow a cooling fluid therethrough. FIG. 11 illustrates a schematic perspective view of an electrical conductor 100 comprising an inner channel 120 having a cooling fluid 122 flowing therethrough. In certain exemplary embodiments, the cooling fluid comprises water, air, or nitrogen. [0058] In certain exemplary embodiments, at least one of electrical conductors 100, 200, 202, 204, and/or 206 may comprise a metal or metal alloy selected from nickel, copper, palladium, or platinum or an alloy thereof.

[0059] FIG. 12 illustrates a schematic view of an electrically heated conduit (fining vessel 34), an electrical conductor 200 proximate the fining vessel 34, and a feedback control mechanism 300 that controls flow of electric current through the electrical conductor 200 in response to at least one condition measured by condition measuring devices 210. Feedback control mechanism 300 can include a controller 302, wherein at least one condition measured by condition measuring devices 210 is fed into controller 302. The condition measuring devices 210 can, for example, comprise temperature, voltage, current, and/or frequency measuring devices that feed a measured temperature, voltage, current, and/or frequency across a portion of fining vessel 34 to controller 302. In response to the at least one measured condition, the controller 302 can control power sources 304 to control or vary the flow of electric current through the electrical conductor 200 and/or annular heating elements 134 via electrical connectors 136. In exemplary embodiments, the controller 302 can also control the flow and/or temperature of cooling fluid 122 flowing through inner channel 120 of electrical conductor 100 in response to at least one measured condition.

[0060] The feedback control mechanism 300 illustrated in FIG. 12 can be applied to any of the exemplary embodiments disclosed herein, including the embodiments illustrated in FIGS. 5-10. For example, in embodiments where two or more electrical conductors are proximate the electrically heated conduit, such as shown, for example, in FIGS. 6-7 and 9-10, flow of electric current through at least one electrical conductor can be controlled to be different than the flow of electric current through at least one other electrical conductor by the feedback control mechanism 300. For example, in the embodiments illustrated in FIGS. 6-7 and 9-10, the flow of electric current through at least one of electrical conductors 202, 204, and/or 206 can be controlled to be different than the flow of electric current through at least one other of electrical conductors 202, 204, and/or 206. This can, for example, be in response to relative differences in measured temperature or voltage across a portion of fining vessel 34 as, for example, measured by condition measuring devices 210.

[0061] While the above embodiments have been described with reference to a fusion down draw process, it is to be understood that such embodiments are also applicable to other glass forming processes, such as float processes, slot draw processes, up-draw processes, tube drawing processes, and press-rolling processes. [0062] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiment of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. An apparatus for processing molten glass comprising: an electrically heated conduit configured to circumferentially surround the molten glass; and an electrical conductor proximate the electrically heated conduit; the electrical conductor configured to flow an electric current therethrough, such that the flow of electric current affects a density of electric current flowing through a portion of the electrically heated conduit.

2. The apparatus of claim 1, wherein the apparatus comprises an annular heating element circumferentially surrounding a portion of the electrically heated conduit.

3. The apparatus of claim 1, wherein the electrical conductor is positioned proximate an area of relatively low electric current density flowing through the electrically heated conduit and is configured to flow electric current in an opposite direction as electric current flowing through the electrically heated conduit.

4. The apparatus of claim 1, wherein the electrical conductor is positioned proximate an area of relatively high electric current density flowing through the electrically heated conduit and is configured to flow electric current in a same direction as electric current flowing through the electrically heated conduit.

5. The apparatus of claim 1, wherein the electrical conductor is configured to flow a cooling fluid therethrough.

6. The apparatus of claim 5, wherein the cooling fluid comprises water, air, or nitrogen.

7. The apparatus of claim 1, wherein the electrically heated conduit comprises platinum or an alloy thereof.

8. The apparatus of claim 1, wherein the electrical conductor comprises a metal or metal alloy selected from nickel, copper, palladium, or platinum or an alloy thereof.

9. The apparatus of claim 1, wherein the apparatus comprises at least one condition measuring device.

10. The apparatus of claim 9, wherein the condition measuring device comprises a temperature measuring device, a voltage measuring device, a current measuring device, and/or a frequency measuring device.

11. The apparatus of claim 9, wherein the apparatus comprises a feedback control mechanism that controls flow of electric current through the electrical conductor in response to at least one condition measured by the condition measuring device.

12. A method for processing molten glass comprising: circumferentially surrounding the molten glass with an electrically heated conduit; and flowing an electric current through an electrical conductor proximate the electrically heated conduit such that the flow of electric current affects a density of electric current flowing through a portion of the electrically heated conduit.

13. The method of claim 12, wherein the method comprises circumferentially surrounding a portion of the electrically heated conduit with an annular heating element.

14. The method of claim 12, wherein the electrical conductor is positioned proximate an area of relatively low electric current density flowing through the electrically heated conduit and the method comprises flowing electric current in an opposite direction as electric current flowing through the electrically heated conduit.

15. The method of claim 12, wherein the electrical conductor is positioned proximate an area of relatively high electric current density flowing through the electrically heated conduit and the method comprises flowing electric current in a same direction as electric current flowing through the electrically heated conduit.

16. The method of claim 15, wherein flow of electric current through at least one electrical conductor is different than the flow of electric current through at least one other electrical conductor.

17. The method of claim 12, wherein the method comprises flowing a cooling fluid through the electrical conductor.

18. The method of claim 17, wherein the cooling fluid comprises water, air, or nitrogen.

19. The method of claim 12, wherein the electrically heated conduit comprises platinum or an alloy thereof.

20. The method of claim 12, wherein the electrical conductor comprises a metal or metal alloy selected from nickel, copper, palladium, or platinum or an alloy thereof.

21. The method of claim 12, wherein the method comprises measuring at least one condition of the electrically heated conduit with a condition measuring device.

22. The method of claim 21, wherein the condition measuring device comprises a temperature measuring device, a voltage measuring device, a current measuring device, and/or a frequency measuring device.

3. The method of claim 21, wherein the method comprises controlling a flow of electric current through the electrical conductor in response to at least one condition measured by the condition measuring device.