A GLASS MANUFACTURING APPARATUS COMPRISING A DELIVERY CONDUIT SYSTEM WITH A LOW IMPEDANCE DRAIN ASSEMBLY

A delivery conduit system for a glass manufacturing apparatus, the conduit system including a drain assembly configured to allow draining molten glass from the delivery conduit system. The drain assembly includes heating means and cooling means that can open a drain flow of molten glass from components of the conduit system and shut off flow to the forming body by selectively modifying the fluid impedance presented to the molten glass by the drain assembly.

FIELD

The present disclosure relates to a glass manufacturing apparatus, and in particular a glass manufacturing apparatus including a drain capable of ceasing flow of molten material to a forming apparatus during the draining.

BACKGROUND

Glass manufacturing processes can be divided into three stages: melting, conditioning and forming. Precursor materials are heated to form a molten material, bubble-forming gases are removed from the molten material, and the molten material is homogenized, for example by stirring. The molten material is then provided to a forming apparatus that forms the molten material into a useful product. Normally, after conditioning and before the forming apparatus, a drain in the glass manufacturing apparatus may be used to drain molten material from the system in the event of a problem with the forming apparatus or forming process, a problem with the molten material itself, or to change the composition of the molten material in the system.

However, drains may not by themselves redirect all of the flow of molten material from the system, and particularly the forming apparatus. As the molten material empties from the system, the molten material may flow to both the forming apparatus and the drain. This can be problematic because the forming system may be damaged by unintended flow of molten material through the forming apparatus during the draining process.

SUMMARY

In a first aspect, a glass manufacturing apparatus is disclosed comprising a delivery conduit system configured to convey a flow of molten glass from a delivery vessel to a forming body, the delivery conduit system comprising: an exit conduit extending from the delivery vessel, an inlet conduit extending from the forming body, a drain assembly coupled between the exit conduit and the inlet conduit, the drain assembly comprising a downward-extending drain tube comprising an inlet end and an outlet end, a first cooling device disposed adjacent the delivery conduit system between the drain tube and the forming body, and a heating device configured to heat the outlet end of the drain tube.

In a second aspect, the heating device of the first aspect may comprise a pair of electrical flanges attached to the drain tube.

In a third aspect, the drain assembly of any one of the first or second aspect may comprise a first curved conduit section configured to direct the flow of molten glass from a first direction to a second direction different from the first direction.

In a fourth aspect, the first curved conduit section of any one of the first through the third aspects may comprise a first curved conduit portion and a second curved conduit portion, each of the first curved conduit portion and the second curved conduit portion configured to direct the flow of molten glass through a change in direction of 90 degrees.

In a fifth aspect, the first curved conduit section of the fourth aspect comprises a first straight conduit portion coupled between the first curved conduit portion and the second curved conduit portion.

In a sixth aspect, the drain tube of the fifth aspect may be coupled to the first straight conduit portion.

In a seventh aspect, the glass manufacturing apparatus of the fifth aspect may further comprise a second curved conduit section coupled to the first curved conduit section.

In an eighth aspect, the glass manufacturing apparatus of the seventh aspect may comprise a second straight conduit portion coupled between the second curved conduit portion and the second curved conduit section.

In a ninth aspect, the cooling device of the eighth aspect may be positioned proximate the second straight conduit portion.

In a tenth aspect, the delivery conduit system of any one of the first through the ninth aspects may comprise platinum.

In an eleventh aspect, an inside diameter of the exit conduit of the third aspect may be less than an inside diameter of the first curved conduit section.

In a twelfth aspect, a first transition tube may be coupled between the exit conduit and the first curved conduit section of the eleventh aspect, and an inside diameter of the first transition tube may vary between the inside diameter of the exit conduit and the inside diameter of the first curved conduit section.

In a thirteenth aspect, an inside diameter of the inlet conduit of the third aspect may be less than an inside diameter of the first curved conduit section.

In a fourteenth aspect, a first transition tube may be coupled between the inlet conduit and the first curved conduit section of the eleventh aspect, and an inside diameter of the first transition tube may vary between the inside diameter of the inlet conduit and the inside diameter of the first curved conduit section.

In a fifteenth aspect, the second curved conduit section of the seventh aspect may be coupled to the inlet conduit and an inside diameter of the inlet conduit may be less than an inside diameter of the second curved conduit section.

In a sixteenth aspect, a second transition tube may be coupled between the inlet conduit and the second curved conduit section of the eleventh aspect, and an inside diameter of the second transition tube may vary between the inside diameter of the inlet conduit and the inside diameter of the second curved conduit section.

In a seventeenth aspect, the glass manufacturing apparatus of any one of the first aspect through the sixteenth aspect may further comprise a second cooling device positioned proximate the exit conduit.

In an eighteenth aspect, a glass manufacturing apparatus is described, comprising a delivery vessel, a forming body, and a delivery conduit system configured to convey a flow of molten glass from the delivery vessel toward the forming body, the delivery conduit system comprising: an exit conduit extending downward from the delivery vessel; an inlet conduit extending from the forming body; a drain assembly coupled between the exit conduit and the inlet conduit, the drain assembly comprising a first curved conduit section and a second curved conduit section disposed downstream of the first curved conduit section relative to a flow direction of the molten glass; a drain tube extending downward from the drain assembly, the drain tube comprising a proximal end attached to the drain assembly and a distal end opposite the proximal end; a first cooling device disposed downstream from the first curved conduit section and configured to cool the at least a portion of the delivery conduit system downstream from the first curved conduit section; and a heating device configured to heat the distal end of the drain tube.

In a nineteenth aspect, an inside diameter of the exit conduit may be less than an inside diameter of the first curved conduit section.

In a twentieth aspect, an inside diameter of the inlet conduit may be less than an inside diameter of the second curved conduit section.

In a twenty-first aspect, the first curved conduit section of any one of the eighteenth aspect through the twentieth aspects may be configured to direct the flow of molten glass from a first direction to a second direction opposite the first direction.

In a twenty-second aspect, the second curved conduit section of the twenty-first aspect may be configured to direct the flow of molten glass from the second direction to a third direction intermediate the first direction and the second direction.

In a twenty-third aspect, the third direction may be orthogonal to the first direction.

In a twenty-fourth aspect, the first curved conduit section of the twenty-first aspect may comprise a first curved conduit portion and a second curved conduit portion, each of the first curved conduit portion and the second curved conduit portion extending through an angle of 90 degrees.

In a twenty-fifth aspect, the first curved conduit section of any one of the eighteenth aspect through the twenty-fourth aspect may comprise a first curved conduit portion, a second curved conduit portion, and a first straight conduit portion disposed between the first curved conduit portion and the second curved conduit portion.

In a twenty-sixth aspect, the proximal end of the drain tube may be attached to and in fluid communication with the straight section.

In a twenty-seventh aspect, the glass manufacturing apparatus of any one of the eighteenth aspect through the twenty-second sixth aspect may further comprise a second cooling device positioned proximate to and configured to cool the exit conduit.

In a twenty-eighth aspect, the glass manufacturing apparatus of any one of the eighteenth aspect through the twenty-seventh aspect may further comprise a second straight conduit portion coupled between the first curved conduit section and the second curved conduit section.

In a twenty-ninth aspect, a method of draining a delivery conduit system is disclosed, comprising: flowing molten glass from a delivery vessel to a forming body through a delivery conduit system comprising an exit conduit connected to the delivery vessel, an inlet conduit connected to the forming body, and a drain assembly connected between the exit conduit and the inlet conduit, the drain assembly comprising a drain tube connected thereto, the drain tube comprising a proximal end attached to the drain assembly and a distal end opposite the proximal end, the drain tube comprising a first plug of material disposed therein that prevents a flow of the molten glass from the distal end; heating the distal end of the drain tube to remove the plug of material and allow the molten glass to flow from the distal end; and cooling the molten glass in a portion of the delivery conduit system downstream from the drain tube to form a second plug of material in the delivery conduit system and reduce the flow of molten glass to the forming body.

In a thirtieth aspect, the method may further comprise cooling the molten glass in at least a portion of the exit conduit with a second cooling device.

Both the foregoing general description and the following detailed description are intended to provide an overview or framework for understanding the nature and character of the embodiments disclosed herein. The accompanying drawings are included to provide 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 explain the principles and operations thereof.

DETAILED DESCRIPTION

Reference will now be made in detail to 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 can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

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.

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 be presented but have been omitted for brevity.

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 non-exclusive list, such that elements in addition to those specifically recited in the list may also be present.

Shown inFIG.1is an exemplary glass manufacturing apparatus10. Glass manufacturing apparatus10comprises a glass melting furnace12including a melting vessel14. In addition to melting vessel14, glass melting furnace12may optionally include one or more additional components such as heating elements (e.g., combustion burners and/or electrodes) configured to heat raw material and convert the raw material into a molten material, which, when cooled, is capable of forming a glass article. For example, melting vessel14may be an electrically-boosted melting vessel, wherein energy is added to the raw material through both combustion burners and by direct heating, wherein an electrical current is passed through the raw material, the electrical current thereby adding energy via Joule heating of the raw material. The molten material will hereinafter be referred to as molten glass. The glass article may, for example, be a silicate glass article and comprise a borosilicate glass, an aluminoborosilicate glass, an alkali-free aluminoborosilicate glass, or a soda-lime glass.

Glass melting furnace12may include other thermal management devices (e.g., thermal insulation components) that reduce heat loss from the melting vessel. Glass melting furnace12may include mechanical, electronic, and/or electromechanical devices that facilitate melting of the raw material into a glass melt. Glass melting furnace12may include support structures (e.g., support chassis, support member, etc.) or other components.

Melting vessel14can be formed from a refractory material, for example a refractory ceramic material comprising alumina or zirconia, although the refractory ceramic material can comprise other refractory materials, such as yttrium (e.g., yttria, yttria-stabilized zirconia, yttrium phosphate), zircon (ZrSiO4) or alumina-zirconia-silica or even chrome oxide, used either alternatively or in any combination. In some examples, melting vessel14may be constructed from refractory ceramic bricks.

As used herein a refractory material is a non-metallic inorganic material that is polycrystalline, polyphasic, inorganic, porous, heterogeneous, and suitable as a component of an apparatus or system exposed to temperatures in excess of 538° C. For example, refractory materials may include but are not limited to oxides of aluminum, silicon, magnesium, calcium, yttrium, and zirconium, alone or in combination. Refractory materials may include a binder material.

Glass melting furnace12may be incorporated as a component of a glass manufacturing apparatus configured to fabricate a glass article, for example a glass ribbon, although the glass manufacturing apparatus can be configured to form other glass articles without limitation, such as glass rods, glass tubes, glass envelopes (for example, glass envelopes for lighting devices, e.g., light bulbs), and glass lenses. In some examples, glass melting furnace12may be included in a glass manufacturing apparatus comprising a slot draw apparatus, a float bath apparatus, a down-draw apparatus (e.g., a fusion down-draw apparatus), an up-draw apparatus, a pressing apparatus, a rolling apparatus, a tube drawing apparatus or any other glass manufacturing apparatus that would benefit from the present disclosure. By way of example,FIG.1schematically illustrates glass melting furnace12as a component of a slot draw glass manufacturing apparatus10. A slot draw process operates by supply molten glass to a forming body comprising a slot in a bottom of the forming body. Molten glass flows from the slot and may be drawn downward therefrom via gravity and counterrotating pulling rolls positioned beneath the slot. The glass ribbon thus formed may subsequently be processed into individual glass sheets or rolled as a glass ribbon onto a spool.

Glass manufacturing apparatus10may optionally include an upstream glass manufacturing apparatus16positioned upstream of melting vessel14. In some examples, a portion of, or the entire upstream glass manufacturing apparatus16, can be incorporated as part of the glass melting furnace12.

As shown inFIG.1, upstream glass manufacturing apparatus16can include a raw material storage bin18, a raw material delivery device20, and a motor22connected to raw material delivery device20. Raw material storage bin18can be configured to store raw material24that can be fed into melting vessel14of glass melting furnace12through one or more feed ports, as indicated by arrow26. Raw material24typically comprises one or more glass forming metal oxides and one or more modifying agents. In some examples, raw material delivery device20may be powered by motor22to deliver a predetermined amount of raw material24from raw material storage bin18to melting vessel14. In further examples, motor22may power raw material delivery device20to introduce raw material24at a controlled rate based on a level of molten glass sensed downstream from melting vessel14relative to a flow direction of the molten glass. Raw material24within melting vessel14can thereafter be heated to form molten glass28. Typically, the raw material is added to the melting vessel as particulate, for example as various “sands.” Raw material24may also include scrap glass (i.e., cullet) from previous melting and/or forming operations. Combustion burners may be used to begin the melting process. In an electrically boosted melting process, once the electrical resistance of the raw material is sufficiently reduced by the combustion burners, electric boost can begin by developing an electrical potential between electrodes positioned in contact with the raw material, thereby establishing an electrical current through the raw material, the raw material typically entering, or in, a molten state.

Glass manufacturing apparatus10may also include a downstream glass manufacturing apparatus30positioned downstream of glass melting furnace12relative to a flow direction of molten glass28. In some examples, a portion of downstream glass manufacturing apparatus30may be incorporated as part of glass melting furnace12. For instance, first connecting conduit32discussed below, or other portions of the downstream glass manufacturing apparatus30, may be incorporated as part of the glass melting furnace12.

Downstream glass manufacturing apparatus30may include a first conditioning chamber, such as fining vessel34, located downstream from melting vessel14and coupled to melting vessel14by way of the above-referenced first connecting conduit32. Molten glass28may be gravity fed from melting vessel14to fining vessel34by way of first connecting conduit32. Accordingly, first connecting conduit32provides a flow path for molten glass28from melting vessel14to fining vessel34. However, other conditioning chambers may be positioned downstream of melting vessel14, for example between melting vessel14and fining vessel34. In some embodiments, a conditioning chamber may be employed between the melting vessel and the fining chamber. For example, molten glass from a primary melting vessel can be further heated in a secondary melting (conditioning) vessel or cooled in the secondary melting vessel to a temperature lower than the temperature of the molten glass in the primary melting vessel before entering the fining chamber.

Bubbles may be removed from molten glass28by various techniques. For example, raw material24may 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 can include without limitation arsenic, antimony, iron, and/or cerium, although the use of arsenic and antimony, owing to their toxicity, may be discouraged for environmental reasons in some applications. Fining vessel34is heated, for example to a temperature greater than the melting vessel interior temperature, thereby heating the fining agent to a reaction temperature sufficient to induce chemical reduction of the one or more fining agents. Oxygen produced by chemical reduction of the one or more fining agents included in the molten glass diffuses into gas bubbles produced during the melting process. The enlarged gas bubbles with increased buoyancy rise to a free surface of the molten glass within the fining vessel and are thereafter vented from the fining vessel, for example through a vent tube in fluid communication with the atmosphere above the free surface.

Downstream glass manufacturing apparatus30may further include another conditioning chamber, such as mixing apparatus36, for example a stirring vessel, for mixing the molten glass that flows downstream from fining vessel34. Mixing apparatus36can be used to provide a homogenous glass melt composition, thereby reducing chemical and/or thermal inhomogeneities that may otherwise exist within the molten glass exiting the fining vessel. As shown, fining vessel34may be coupled to mixing apparatus36by way of a second connecting conduit38. Accordingly, molten glass28can be gravity fed from the fining vessel34to mixing apparatus36through second connecting conduit38. Typically, the molten glass within mixing apparatus36includes a free surface, with a free (e.g., gaseous) volume extending between the free surface and a top of the mixing apparatus. While mixing apparatus36is shown downstream of fining vessel34relative to a flow direction of molten glass28, mixing apparatus36may be positioned upstream from fining vessel34in other embodiments. In some embodiments, downstream glass manufacturing apparatus30may include multiple mixing apparatus, for example a mixing apparatus upstream from fining vessel34and a mixing apparatus downstream from fining vessel34. When used, multiple mixing apparatus may be of the same design, or they may be of a different design from one another. One or more of the vessels and/or conduits may include static mixing vanes positioned therein to further promote mixing and subsequent homogenization of the molten material.

Downstream glass manufacturing apparatus30may further include another conditioning chamber such as delivery vessel40located downstream from mixing apparatus36. Delivery vessel40can act as an accumulator and/or flow controller to provide a consistent flow of molten glass28to forming body42by way of exit conduit44. The molten glass within delivery vessel40can, in some embodiments, include a free surface, wherein a free volume extends upward from the free surface to a top of the delivery vessel. As shown, mixing apparatus36can be coupled to delivery vessel40by way of third connecting conduit46, wherein molten glass28can be gravity fed from mixing apparatus36to delivery vessel40through third connecting conduit46.

Downstream glass manufacturing apparatus30may further include forming apparatus48configured to form a glass article, for example glass ribbons. Accordingly, forming apparatus48may comprise a forming body42, for example a forming vessel, wherein exit conduit44is positioned to deliver molten glass28from delivery vessel40to inlet conduit50of the forming vessel. The forming vessel may comprises a slot at the bottom of the forming vessel, wherein molten glass delivered to an open volume of forming vessel42flows through the slot to produce a ribbon60of molten glass that is drawn in draw direction56from the bottom edge by applying a downward tension to the glass ribbon, such as by gravity and/or and opposing, counter-rotating pulling rolls. Alternatively, forming body42may comprise, for example, a fusion down-draw glass manufacturing apparatus molten glass delivered to a trough in forming body42via delivery vessel40, exit conduit44and inlet conduit50. The molten glass overflows the walls of the trough and descends along the converging forming surfaces as separate flows of molten glass. The separate flows of molten glass join below and along a bottom edge of the forming body to produce the ribbon60of molten glass that is drawn in draw direction56from the bottom edge by, again, applying a downward tension to the glass ribbon, such as by gravity and/or counter-rotating and opposing pulling rolls. In either case, glass ribbon60goes through a viscosity transition, from a viscous state, to viscoelastic state, to an elastic state and acquires mechanical properties that give glass ribbon60stable dimensional characteristics. Glass ribbon60may be separated into shorter lengths, such as into glass sheets62, by a glass separating apparatus64. Alternatively, the glass ribbon may be spooled.

Components of downstream glass manufacturing apparatus30, including any one or more of connecting conduits32,38,46, fining vessel34, mixing apparatus36, delivery vessel40, exit conduit44, or inlet conduit50may be formed from a high-temperature metal. Suitable metals include platinum group metals selected from the group 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.

FIG.2is a cross-sectional view of a portion of downstream glass manufacturing apparatus30, i.e., delivery conduit system90, comprising exit conduit44, inlet conduit50, and drain assembly100, delivery conduit system90configured to deliver molten glass from delivery vessel40to forming body42. Exit conduit44extends from delivery vessel40and provides a discharge path for molten glass from delivery vessel40. Inlet conduit50is coupled to forming body42and provides a path for molten glass28to enter forming body42. Drain assembly100couples distal end102of exit conduit44to distal end104of inlet conduit50and provides a first flow path106for molten glass28traversing from exit conduit44to inlet conduit50and forming body42, and a second flow path108different than first flow path106that enables draining molten glass from any one or more of delivery vessel40, exit conduit44, inlet conduit50, drain assembly100, or forming body42.

Drain assembly100comprises a curved conduit section110configured to direct the flow of molten glass28from a first, downward flow direction112to a second flow direction114different from first flow direction112. For example, second flow direction114may be orthogonal to first flow direction112. Drain assembly100may further comprise a first transition tube115that couples distal end102of exit conduit44to a first end116of curved conduit section110. Drain assembly100may still further comprise a second transition tube118that couples second end120of curved conduit section110to distal end104of inlet conduit50. For example, an inner diameter (ID)130of the first end116of curved conduit section110may be greater than the ID132of distal end102of exit conduit44. Similarly, second end120of curved conduit section110may have a greater ID than the ID of distal end104of inlet conduit50. Accordingly, the IDs of first and second transition tubes115,118may vary along the length of the respective transition tubes to facilitate coupling of attached conduits, e.g., exit conduit44and inlet conduit50, to curved conduit section110when the attached conduits having inner diameters that are different than the inner diameter of curved conduit section110to which they are coupled. The inner diameter of curved conduit section110may be uniform from first end116to second end120. The ID of curved conduit section110may be larger than either one or both the ID of exit conduit44and inlet conduit50.

Drain assembly100further comprises a drain tube140extending between a proximal (inlet) end142and a distal (outlet) end144thereof, proximal end142positioned at and connected to curved conduit section110such that inner passage146of drain tube140is in fluid communication with inner passage148of curved conduit section110. For example, proximal end142may be connected to the lowest point of curved conduit section110, thereby facilitating efficient draining of connected conduits. Drain tube140extends in a downward direction from curved conduit section110, for example in a vertical direction, although sloped directions such as in a range from greater than 0 degrees to 45 degrees relative to vertical, e.g, in a range from greater than 0 degrees from vertical to about 5 degrees from vertical, in a range from greater than 0 degrees from vertical to about 10 degrees from vertical, in a range from greater than 0 degrees from vertical to about 15 degrees from vertical, in a range from greater than 0 degrees from vertical to about 20 degrees from vertical, in a range from greater than 0 degrees from vertical to about 25 degrees from vertical, in a range from greater than 0 degrees from vertical to about 30 degrees from vertical, in a range from greater than 0 degrees from vertical to about 35 degrees from vertical, in a range from greater than 0 degrees from vertical to about 40 degrees from vertical, including all ranges and subranges therebetween, are also contemplated. While illustrated as a straight tube, drain tube140may include one or more curved portions or a combination of straight and curved portions. Drain tube140should be made a short as possible to avoid unnecessary impedance to fluid flow when the drain tube is operational and molten glass is draining therefrom.

Drain assembly100still further comprises a first cooling device150apositioned downstream of curved conduit section110. For example, first cooling device150amay be positioned adjacent inlet conduit50. First cooling device150amay comprise, for example, a helical tube that encircles inlet conduit50downstream of curved conduit section110relative to the direction of molten glass flow. First cooling device150amay be configured to allow a coolant to flow through the cooling device, thereby cooling the adjacent portion of inlet conduit50. For example, the helical tube may comprise a hollow interior that provides a flow path for coolant to flow through. Suitable coolants may be one or more nonoxidizing gases, e.g., nitrogen, any one or more of the group VIIIA gases (e.g., helium, neon, argon, krypton, xenon), or combinations thereof. However, first cooling device150amay utilize other forms of cooling capable of cooling a portion of inlet conduit50about a periphery of the inlet conduit, either alternatively or in addition to a coolingtube configured to convey a coolant therethrough. For example, first cooling device150amay comprise a cooling jacket rather than a cooling tube, or a thermoelectrical cooling device.

As shown inFIG.2, one or more heating elements160may be positioned proximate exit conduit44, drain assembly100, and/or inlet conduit50. Heating elements160may be resistive heating elements that generate heat by Joule heating and heat the associated metal component by radiative and/or conductive heating. Heating elements160may comprise helical coils wound around the respective conduit, although other physical forms of heating elements may be employed, such as multiple discrete heating elements arranged around a periphery of the respective conduit. In some instances, distal end144of drain tube140may be heated by a similar heating element160. However, as illustrated inFIG.2, in some instances distal end144may be heated by a flame provided by a burner162, e.g., a fuel-air burner.

An optional second cooling device150bmay be positioned proximate exit conduit44. For example, second cooling device150bmay be a cooling coil configured to receive a flow of cooling fluid through an interior passage thereof. Second cooling device150bmay be used to reduce and or stop flow from exit conduit44to forming body42, until such time that heating of distal end144can be completed for example.

Drain assembly100, including drain tube140, may be formed from a precious metal, for example a precious metal compatible with the precious metal forming exit conduit44and/or inlet conduit50. Suitable precious metals include platinum group metals selected from the group consisting of platinum, iridium, rhodium, osmium, ruthenium and palladium, or alloys thereof. For example, drain assembly100may 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.

Alternatively, or in addition to heating elements160, electrical flanges170may be attached to portions of the downstream glass manufacturing apparatus30for heating purposes. For example,FIG.1shows electrical flanges170attached to exit conduit44, fining vessel34, and inlet conduit50, although electrical flanges170may be attached to other metal components of downstream glass manufacturing apparatus30. Electrical flanges170are electrically connected to one or more electrical power supplies (not shown) such that an electrical current can be established in sections of the metal components to which the electrical flanges are attached, for example between adjacent consecutive electrical flanges.

Accordingly,FIG.3depicts a delivery conduit system92similar to delivery conduit system90, except that electrical flanges170may be substituted for one or more heating elements160. More specifically, electrical flanges170aand170bare shown attached to exit conduit44, electrical flanges170cand170dattached to inlet conduit50, and electrical flanges170e,170f,170g, and170hattached to drain tube140. The number and positions of electrical flanges170may be provided as necessary. For example, while two electrical flanges are shown attached to exit conduit44, fewer than two electrical flanges (e.g., one electrical flange), or more than two electrical flanges (e.g., three electrical flanges, four electrical flanges, or five or more electrical flanges) may be attached to exit conduit44. An electrical current is established in a wall of the metal component between adjacent and consecutive electrical flanges by the one or more electrical power supplies. Thus, for example, a first electrical current can be established between electrical flange170aand electrical flange170b. A second electrical current can be established between electrical flange170band electrical flange170c. A third electrical current can be established between electrical flanges170cand170d. A fourth electrical current can be established between electrical flanges170band170e. A fifth electrical current can be established between electrical flanges170eand170f. A sixth electrical current can be established between electrical flanges170fand170g. The various electrical currents heat each respective portion of the metal components between adjacent and consecutive electrical flanges (e.g., exit conduit44, inlet conduit50, forming body42, and drain assembly100) by Joule heating. The physical arrangement of electrical flanges, and the flow of electrical currents therebetween may be configured according to specific system needs. Thus, the preceding physical arrangement and electrical currents are exemplary and provided as a nonlimiting illustration of a possible configuration. Electrical flanges170may comprise a precious metal, for example a precious metal compatible with the precious metal forming exit conduit44and/or inlet conduit50. Suitable precious metals include platinum group metals selected from the group consisting of platinum, iridium, rhodium, osmium, ruthenium and palladium, or alloys thereof. For example, electrical flanges170may comprise a platinum-rhodium alloy including from about 70% to about 90% by weight platinum and about 10% to about 30% by weight rhodium. Portions of electrical flanges170may comprise nickel. For example, outer portions of the flanges not exposed to high temperature may comprise nickel or a nickel alloy.

As previously described in respect of delivery conduit system90, delivery conduit system92may include first and second cooling devices150aand150b. For example, first and second cooling devices150a,150bmay comprise a cooling coil configured to receive a flow of cooling fluid through an interior passage thereof.

The various electrical currents described above (e.g., first through sixth) need not have the same magnitude. Accordingly, different portions of the metal components (e.g., exit conduit44, inlet conduit50, forming body42, and drain assembly100) may be heated to different temperatures by controlling the individual electrical currents between pairs of electrical flanges as the need arises. Electrical flanges170fand170gmay be closely spaced, thereby allowing a short length of drain tube140near distal end144of the drain tube140to be selectively heated.

FIG.4depicts another delivery conduit system94similar to delivery conduit system90but comprising a drain assembly200including a first curved conduit section202, and a second curved conduit section204disposed downstream of first curved conduit section202relative to the flow of molten glass. First curved conduit section202may be a U-shaped conduit section defining an interior passage206for the flow of molten glass28along a first flow path208. Thus, the downward first flow direction112of molten glass28from exit conduit44may be redirected by first curved conduit section202to an upward second flow direction114(at the exit of first curved conduit section202) of molten glass in flow direction210. For example, first curved conduit section202may extend through a 180-degree curvature such that flow direction210is opposite first flow direction112, although other curvatures are contemplated and may be provided as needed. Second curved conduit section204is coupled to first curved conduit section202. The flow of molten glass exiting first curved conduit section202is further directed by second curved conduit section204to a lateral flow of molten glass along second flow direction114. Second flow direction114may be orthogonal to first flow direction112in inlet conduit50and/or flow direction210. For example, either one or both of first curved conduit section202or second curved conduit section204may include a 90-degree elbow conduit. Second curved conduit section204is coupled to distal end104of inlet conduit50, wherein the flow of molten glass is provided to forming body42from inlet conduit50.

Drain assembly200further comprises a drain tube214extending downward between a proximal end216and a distal end218, proximal end216connected to first curved conduit section202such that interior passage220of drain tube214is in fluid communication with interior passage206of first curved conduit section202. While drain tube214is depicted as a vertically extending tube, sloped directions such as in a range from greater than 0 degrees from vertical to 45 degrees from vertical, e.g., in a range from greater than 0 degrees from vertical to about 5 degrees from vertical, in a range from greater than 0 degrees from vertical to about 10 degrees from vertical, in a range from greater than 0 degrees from vertical to about 15 degrees from vertical, in a range from greater than 0 degrees from vertical to about 20 degrees from vertical, in a range from greater than 0 degrees from vertical to about 25 degrees from vertical, in a range from greater than 0 degrees from vertical to about 30 degrees from vertical, in a range from greater than 0 degrees from vertical to about 35 degrees from vertical, in a range from greater than 0 degrees from vertical to about 40 degrees from vertical, including all ranges and subranges therebetween, are also contemplated. While illustrated as a straight tube, drain tube214need not be straight, but may include one or more curved portions. Drain tube214defines a second flow path224along which molten glass may be drained from any one or more of delivery vessel40, exit conduit44, drain assembly200, forming body42, and/or inlet conduit50.

Drain assembly200may further comprise a first transition tube230that couples distal end102of exit conduit44to a first end232of first curved conduit section202. Drain assembly200may still further comprise a second transition tube234that couples second end236of first curved conduit section202to distal end104of inlet conduit50. For example, as shown inFIG.4, an inner diameter (ID)240of the first end232of first curved conduit section202may be greater than the ID132of distal end102of exit conduit44. Similarly, second end236of second curved conduit section204may have a greater ID than the ID of distal end104of inlet conduit50. Accordingly, the IDs of first and second transition tubes230and234may vary along the length of the respective transition tubes to facilitate coupling of attached conduits, e.g., exit conduit44and inlet conduit50, to the respective first curved conduit section202or second curved conduit section204when the attached conduits have inner diameters that are different than the inner diameters of first curved conduit section202or second curved conduit section204. The inner diameter of first curved conduit section202may be uniform along the length of the first curved conduit section. Similarly, the inner diameter of second curved conduit section204may be uniform along the length of the second curved conduit section. The ID of first curved conduit section202and/or second curved conduit section204may be larger than either one or both the ID of exit conduit44and the ID of inlet conduit50.

Delivery conduit system94comprises first cooling device150apositioned downstream of first curved conduit section202relative to the direction of flow of molten glass. As described for previous embodiments, first cooling device150amay comprise a helical tube positioned between first curved conduit portion202and second curved conduit section204, first cooling device150aconfigured to allow a coolant to flow through the helical tube, thereby cooling the molten glass conveyed therethrough. For example, the helical tube may comprise a hollow interior that provides a flow path for coolant. Suitable coolants may be one or more nonoxidizing gases (e.g., nitrogen, noble gases, or combinations thereof) or a liquid (water). However, first cooling device150amay take other forms capable of cooling a portion of delivery conduit system94. For example, first cooling device150amay comprise a cooling jacket or a thermoelectrical cooling device.

As shown inFIG.4and similar to the embodiment ofFIG.2, one or more heating elements160may be positioned proximate exit conduit44, drain assembly200, inlet conduit50, and/or drain tube214. As previously described, heating elements160may be resistive heating elements that generate heat by Joule heating and heat the adjacent metal component by radiative and/or conductive heating. In some instances, distal end218of drain tube214may be heated by a similar heating element160. In some instances, distal end218may be heated by a flame provided by burner162, e.g., a fuel-air burner.

As previously described in respect of delivery conduit system90, delivery conduit system94may optionally include second cooling device150bpositioned proximate exit conduit44, second cooling device150bconfigured to reduce or eliminate flow from exit conduit44. For example, when second cooling device150bis activated, such as by commencing a flow of coolant therethrough, the viscosity of molten glass in exit conduit44adjacent second cooling device150bcan be increased, thereby forming a plug of glass in the exit conduit.

Referring toFIG.5, drain assembly200may include one or more straight conduit portions. For example, first curved conduit section202may comprise a first curved conduit portion250and a second curved conduit portion252, wherein a first straight conduit portion254may be coupled between first curved conduit portion250and second curved conduit portion252. Similarly, a second straight conduit portion256may be coupled between second curved conduit portion252and second curved conduit section204. The arrangement of curved and straight lengths of conduit shown inFIG.5allow for more versatile configuration of the drain assembly than if only curved lengths are used. For example, as illustrated inFIG.5, the length258of first straight conduit portion254can be increased or decreased as necessary to accommodate a predetermined horizontal separation between delivery vessel40(e.g., exit conduit44) and forming body42(e.g., inlet conduit50). Similarly, the length260of second straight conduit portion256may be increased or decreased as necessary to accommodate a predetermined vertical separation between delivery vessel40and forming body42(e.g., inlet conduit50). Moreover, the angular orientation between the various curved and straight portions of the drain assembly conduits (indicated by curved arrows262and their respective axes inFIG.5), as well as their lengths, may be arranged as needed, thereby providing multiple degrees of freedom of movement and allowing the drain assembly to facilitate a large number of mechanical arrangements of delivery vessel40and forming body42relative to each other. In particular, second straight conduit portion256may be utilized as a convenient location at which to position first cooling device150a. For example, first cooling device150amay be positioned proximate second straight conduit portion256. Such an arrangement is shown inFIG.4, for example, wherein first cooling device150ais depicted as a helical tube wound about straight conduit portion256coupled between first curved conduit section202and second curved conduit section204. However, first cooling device150amay be positioned proximate other portions of delivery conduit system92, or at inlet conduit50. In the embodiment ofFIG.5, drain tube214is shown connected to and descending from first straight conduit portion254disposed between first curved conduit portion250and second curved conduit portion252.

Electrical flanges170may be attached to portions of the downstream glass manufacturing apparatus and configured to establish an electrical current in the portions of the downstream glass manufacturing apparatus. The various electrical flanges shown inFIG.3are equally suitable for the embodiment depicted inFIG.4, including the distribution of electrical currents capable of heating sections of the metal components between adjacent electrical flanges to the same or different temperatures.

Accordingly,FIG.6depicts another delivery conduit system96comprising drain assembly200similar to delivery conduit system94except that delivery conduit system96comprises electrical flanges170substituted for one or more heating elements150. For example,FIG.6illustrates electrical flanges170attached to exit conduit44, fining vessel34, and inlet conduit50, although electrical flanges170may be attached to other metal components of downstream glass manufacturing apparatus30. Electrical flanges170are electrically connected to one or more electrical power supplies (not shown) such that an electrical current can be established in sections of the metal components to which the electrical flanges are attached. More specifically,FIG.6depicts electrical flanges170aand170battached to exit conduit44, electrical flanges170cand170dattached to inlet conduit50, and electrical flanges170e,170f,170g, and170hattached to drain tube314. The number and positions of electrical flanges170may be provided as necessary. For example, while two electrical flanges are shown attached to exit conduit44, fewer than two electrical flanges (e.g., one electrical flange), or more than two electrical flanges (e.g., three electrical flanges, four electrical flanges, or five or more electrical flanges) may be attached to exit conduit44. An electrical current is established in a wall of the metal component between adjacent electrical flanges by the one or more electrical power supplies. Thus, for example, a first electrical current can be established between electrical flange170aand electrical flange170b. A second electrical current can be established between electrical flange170band electrical flange170c. A third electrical current can be established between electrical flanges170cand170d. A fourth electrical current can be established between electrical flanges170band170e. A fifth electrical current can be established between electrical flanges170eand170f. A sixth electrical current can be established between electrical flanges170fand170g. The various electrical currents heat each respective portion of the metal components between adjacent electrical flanges (e.g., exit conduit44, inlet conduit50, forming body42, and drain assembly200) by Joule heating.

The various electrical currents (e.g., first through sixth) need not have the same magnitude. Accordingly, different portions of the metal components (e.g., exit conduit44, inlet conduit50, forming body42, and drain assembly200) may be heated to different temperatures by controlling the individual electrical currents between pairs of electrical flanges as the need arises. Electrical flanges170fand170gare closely spaced, thereby allowing a short length of drain tube314near distal end318of the drain tube to be selectively heated.

In addition to curved conduit sections described in respect of delivery conduit system92, delivery conduit system96may include straight conduit portions as illustrated inFIG.5.

In addition to the foregoing aspect, any one of the embodiments described herein may be surrounded by one or more layers of refractory insulating material selected to control heat loss from the delivery conduit system. For example,FIG.7illustrates the delivery conduit system depicted inFIG.6encased within layers of a refractory insulating material300. The refractory insulating material may be selected from mullite, an insulating fire brick, Duraboard manufactured by the Johns Manville company (e.g., Duraboard3000), or other refractory thermal insulating materials having a range of thermal conductivities. The thermal conductivities of the refractory insulating materials may be selected as needed to control portions of the delivery conduit system to predetermined temperatures depending on the desired viscosity of the molten glass therein. Additionally, the refractory insulating material surrounding the delivery conduit system, and in particular the drain assembly, should be configured to allow free movement (e.g., expansion) of the delivery conduit system as the system is heated. The refractory insulating material300should allow the delivery conduit system to expand radially, horizontally, and vertically as the delivery conduit system moves during thermal expansion. Accordingly, the refractory insulating material can be separated from all or some of the delivery conduit system, for example the drain assembly, by a gap302. To that end, anchors extending from the delivery conduit system that might bind and support the delivery conduit system within the refractory insulating material may be omitted.

During normal operation, delivery vessel40delivers molten glass28to forming body42via the delivery conduit system. Forming body42may comprise, for example, a slot draw apparatus comprising a vessel that receives the molten glass from the delivery conduit system. The molten glass exits the vessel via a slot arranged on an underside of the vessel, the molten glass forming a glass ribbon that is drawn downward by pulling rolls and gravity. The delivery conduit system and the slot present a predetermined fluid impedance to the flow of molten glass. In particular, the slot may represent the largest single source of fluid impedance during normal operation and may dictate the magnitude of molten glass flow achievable for a predetermined molten glass viscosity.

In may become necessary during a glass forming operation to halt the forming process. For example, it may become necessary to repair or replace certain glass manufacturing equipment, such as glass manufacturing equipment downstream of the forming body or the forming body itself. In such circumstances, the drain tube can be opened. Under normal operating conditions, the drain tube is closed by reducing heating of the drain tube and allowing the drain tube to reach a temperature below the softening temperature of the molten glass. This can be done by reducing the power provided to external resistance heaters adjacent the drain tube, reducing the electrical current through electrical flanges (and the drain tube) positioned at or near the distal end of the drain tube, or not applying a flame to the distal end from a burner, depending on the arrangement of the heating device or devices. Any one of these actions can result in freezing of the material in the drain tube such that a viscosity of the material in the drain tube is sufficiently lowered that it forms a plug that plugs the drain tube such that molten glass does not flow from the distal (i.e., outlet) end of the drain tube.

In the event molten glass is to be drained from the delivery conduit system, the drain tube can be opened by increasing the electrical power to the heating elements (e.g., resistance heaters), thereby increasing heat output from the heating elements, increasing the magnitude of electrical current to the electrical flanges at the distal end of the drain tube, or applying a flame from a burner, depending on the configuration of the heating device or devices, thereby allowing the previously-formed plug to melt and molten glass to flow through and from the drain tube. Thus, the drain tube provides a preferential flow path for the molten glass when the drain tube is opened by decreasing the total impedance of the drain flow path. This can be accomplished, for example, by ensuring the ID of the drain assembly, including the drain tube, is greater than the ID of the connected conduits, e.g., exit conduit of the delivery vessel and/or inlet conduit of the forming body.

This continued flow of molten glass to the forming body may interfere with downstream repairs and/or may result in damage to the forming body wherein the molten glass dams up via insufficient flow and must be hammered out prior to restarting the forming process. In any event, it may be necessary to cease entirely molten glass flow to the forming body. Accordingly, first cooling device150acan be activated, for example by starting a flow of coolant through the cooling device (e.g., cooling tube), thereby freezing molten glass within a portion of the delivery conduit system downstream of the drain tube and forming a glass plug therein. The resultant glass plug prevents further flow to the forming body.

In some instances it may be necessary to reduce or eliminate flow to forming body42faster than can be accommodated by the heating of drain tube140to open the drain tube (increase the viscosity of the glass plug blocking the drain tube so flow of molten glass can be commenced through the drain tube). In instances where optional second cooling device150bis installed, second cooling device150bcan be activated, thereby reducing, or eliminating the flow of molten glass from exit conduit44. When drain tube140is opened, second cooling device150bmay be deactivated if needed, for example to drain delivery vessel40.

It will be apparent to those skilled in the art that various modifications and variations can be made to embodiments 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.