Method for forming a glass article

Abstract

A method for producing a glass product includes flowing molten glass through a first vessel to a downstream second vessel, the molten glass flowing through a conduit connecting the first vessel and the second vessel, the first vessel and the conduit defining a continuous free space above a free surface of the molten glass extending at least a portion of the conduit. The method further includes venting a first atmosphere contained in the free space to a second atmosphere outside the first vessel through a vent pipe connected to the conduit adjacent an upper portion of the conduit and above the free surface, the vent pipe extending downwardly from the conduit along a longitudinal axis at an angle α with respect to the horizontal to a distal end of the vent pipe providing fluid communication between the first atmosphere and the second atmosphere.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 63 / 064,642, filed August 12, 2020, the contents of which are incorporated herein by reference in their entirety.

[0002] (Technical field) FIELD OF THE DISCLOSURE The present disclosure relates to methods of forming glass articles, and more particularly to methods of venting vessels that hold or transport molten glass during article manufacture. [Background technology]

[0003] Fining molten glass in the glassmaking process is useful for removing dissolved gases in the molten glass and helping to obtain a bubble-free glass product. Raising the temperature of the molten glass above the melting point releases oxygen from one or more fining agents in the molten glass. The oxygen combines with melt-related gases, and the resulting mixed-gas bubbles rise to the surface of the molten glass. The bubbles pop and the released gases fill the free space in the fining vessel. These gases must be removed from the fining vessel. However, venting the fining vessel directly through the top of the vessel poses a risk of condensed particles falling from the vent pipe into the molten glass below, either naturally or when the vent pipe is cleaned to remove condensed particles. Summary of the Invention

[0004] According to the present disclosure, a method of manufacturing a glass article is disclosed, the method including flowing molten material through a first vessel to a second vessel downstream from the first vessel, the molten material flowing through a conduit connecting the first vessel to the second vessel, the first vessel and the conduit defining a continuous free volume above a free surface of the molten material, the free volume extending at least a portion of the conduit. The method further includes venting a first atmosphere contained in the free volume to a second atmosphere outside the first vessel through a vent tube having a proximal end, a distal end opposite the proximal end, and a passageway extending between the proximal end and the distal end, the proximal end connected to the conduit adjacent a top of the conduit and above the free surface, the vent tube extending downward and away from the conduit along a longitudinal axis at an angle α with respect to the horizontal to provide fluid communication between the first atmosphere and the second atmosphere.

[0005] The vent tube may be straight with no bends or kinks between the proximal and distal ends, the proximal end being attached to the first container.

[0006] In various embodiments, the angle α ranges from greater than 0° to less than 90°, for example, from about 3° to about 80°, from about 3° to about 40°, from about 3° to about 20°, or from about 3° to about 10°.

[0007] In some embodiments, the method can further include heating the vent pipe during venting. The heating step can include establishing an electric current in a heating element. The heating element can include a wall of the vent pipe or can be one or more individual, discrete heating elements disposed adjacent to the wall of the vent pipe.

[0008] If the vent pipe wall is a heating element, the heating step may include establishing an electric current between a first electrical flange connected to the vent pipe and a second electrical flange connected to at least one of the first vessel or the conduit.

[0009] In various embodiments, the first vessel can be a fining vessel.

[0010] In various embodiments, the second container can be a mixing container.

[0011] The method can further include flowing the molten material into a forming body to form the molten material into a glass ribbon. In some embodiments, the forming can include drawing the molten material downwardly from the forming body.

[0012] In some embodiments, a first portion of the conduit can extend horizontally from the first vessel, and the vent pipe can be connected to the first portion. In some embodiments, a second portion of the conduit extends downward relative to the horizontal. The second portion can be located downstream from the first portion relative to the direction of flow of molten glass through the conduit. The second portion can be attached to the first portion. In some embodiments, the conduit can include a first portion and a second portion, and the first conduit portion and the second conduit portion comprise a first conduit section. The conduit can further include a second section coupled to the first conduit portion (e.g., the second conduit portion) by a glass seal.

[0013] The method may further include flowing a cover gas through a gas delivery pipe connected to the first container into the free volume. The gas may include an inert gas. The gas may include oxygen. The gas may be a mixture of an inert gas and oxygen. The gas may be a humidified gas.

[0014] The method may further include heating the conduit while flowing the molten material through the conduit. In some embodiments, the wall thickness of the conduit varies along the length of the conduit. That is, in a cross-section of the conduit perpendicular to the longitudinal axis of the conduit, the wall thickness of the conduit at a first portion of the cross-section is different from the wall thickness of the conduit at a second portion of the cross-section. In some embodiments, the circumferential thickness of the wall of the conduit may vary along the length of the conduit. In some embodiments, the thickness may vary both circumferentially and as a function of length. In another embodiment, a method is described for manufacturing a glass article, the method including flowing the molten material from a first vessel through a conduit connected to the first vessel, the first vessel and the conduit defining a continuous free volume above a free surface of the molten material, the free volume extending through a portion of the conduit.

[0015] The method may further include venting a first atmosphere contained in the free volume to a second atmosphere outside the first container via a vent tube having a proximal end and a distal end opposite the proximal end, the proximal end connected above the free surface adjacent to an upper portion of the conduit, the vent tube extending downwardly along the longitudinal axis at an angle α relative to the horizontal, providing fluid communication between the first atmosphere and the second atmosphere.

[0016] The method may further include heating the vent pipe while the molten material is flowing, whereby the heating can remove condensation that has accumulated on the interior surface of the vent pipe. The heating step may include establishing an electric current in a heating element, e.g., a wall of the vent pipe, where the vent pipe is the heating element. For example, the heating step may further include connecting a first electrical flange to the vent pipe and forming into a first glass article. In some embodiments, the glass article may be a glass ribbon. The forming step may include drawing the molten material downwardly from the forming body.

[0017] In some embodiments, the first vessel can be a fining vessel.

[0018] In some embodiments, the second container can be a mixing device.

[0019] In some embodiments, at least a first portion of the conduit extends downward relative to the horizontal. For example, in some embodiments, the first portion of the conduit extends horizontally from the first container, and the vent pipe is connected to the first portion of the conduit. In some embodiments, the second portion of the conduit extends downward from the first portion of the conduit.

[0020] In some embodiments, the conduit can include a first section and a second section, the first section coupled to the second section by a glass seal.

[0021] In some embodiments, the method further includes flowing gas through a gas delivery pipe into the free volume. The gas delivery pipe can be connected to the first container. In some embodiments, the cover gas can include an inert gas, such as nitrogen. The cover gas can be a low-oxygen gas containing less than about 1.5% by volume of oxygen O2, for example, in the range of about 0.075% by volume to about 1.5% by volume of oxygen O2. In some embodiments, the cover gas can be a humidified gas. In some embodiments, the cover gas can be a dry gas.

[0022] Additional features and advantages of the embodiments disclosed herein will be set forth in the detailed description which follows, and in part will be apparent to those skilled in the art from the specification, or may be learned by practice of the embodiments described herein, including the following detailed description, claims, and accompanying drawings.

[0023] It is to be understood that both the foregoing general description and the following detailed description present embodiments that are intended to provide an overview or framework for understanding the nature and state of the embodiments disclosed herein. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the present disclosure and, together with the description, serve to explain its principles and operation. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic diagram of an exemplary glass manufacturing apparatus. [Figure 2] FIG. 1 is a schematic diagram of an exemplary connecting conduit extending between a fining vessel and a mixing device. [Figure 3] FIG. 1 is a cross-sectional side view of an exemplary fining vessel illustrating a gas delivery tube configured to provide cover gas to the free space of the fining vessel. [Figure 4] FIG. 2 is a detailed cross-sectional view of a portion of an exemplary gas delivery pipe. [Figure 5] 3 is a diagram illustrating a portion of the example connecting conduit of FIG. 2, illustrating the extending vent tube. [Figure 6] 6 is a rearward view of the connecting conduit of FIG. 5 along line 6-6 of FIG. 5. [Figure 7] FIG. 10 is a cross-sectional side view of another embodiment of a connecting conduit having a domed portion proximate the finer to which the connecting conduit is attached. [Figure 8] 8 is a rearward view of the connecting conduit of FIG. 7 taken along line 8-8 of FIG. 7, showing the vent tube extending from the dome-shaped portion. [Figure 9] FIG. 7 is a schematic diagram of an exemplary electrical flange located at the distal end of the vent tube shown in FIG. 6. [Figure 10] FIG. 1 is a schematic diagram of one embodiment of a container including a vent tube with a thickened end at the point of attachment to the container. [Figure 11] FIG. 4 is a cross-sectional view showing a thick portion of the ventilation pipe. DETAILED DESCRIPTION OF THE INVENTION

[0025]

[0013] Embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which example embodiments are shown. Wherever practicable, the same reference numerals will be used throughout the drawings to refer to the same or like parts. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0026] 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 can be approximated and / or increased or decreased as necessary to reflect tolerances, conversion factors, rounding, measurement errors, etc., as well as other factors known to those of ordinary skill in the art.

[0027] Ranges may be expressed herein as from "about" one value and / or to "about" another value. When such a range is expressed, another embodiment includes from the one value to the other value. Similarly, when values ​​are expressed as approximations, by use of the antecedent "about," it will be understood that the value forms another embodiment. It will further be understood that the endpoints of each range are significant both in relation to the other endpoint, and independently of the other endpoint.

[0028] Directional terms used herein (e.g., up, down, right, left, front, back, top, bottom) are made with reference to the depicted figures and are not intended to denote absolute directions.

[0029] Unless expressly stated otherwise, methods described herein should not be construed as requiring that their steps be performed in a particular order, nor should any apparatus require a particular direction. Thus, where a method claim does not actually recite an order according to its steps, or where any apparatus claim does not actually recite an order or direction for individual components, or where the claims or the specification do not otherwise expressly state that the steps are limited to a particular order, or where no particular order or direction for the apparatus components is recited, no order or direction should be inferred in any respect. This applies to any available unstated basis for interpretation, including logical issues regarding the placement of steps, operational flow, component order, or component orientation, general meaning derived from grammatical structure or punctuation, and the number or type of embodiments described in the specification.

[0030] As used herein, non-plural nouns include plural forms unless the context clearly indicates otherwise. Thus, for example, reference to a non-plural noun (element) includes aspects having two or more such elements unless the context clearly indicates otherwise.

[0031] The terms "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 "example" is not to be construed as preferred or advantageous over other aspects or designs. Furthermore, examples are provided merely for purposes of clarity and understanding and are not meant to limit or restrict in any way the disclosed subject matter or relevant portions of this disclosure.

[0032] As used herein, the terms "comprises" and "includes," and variations thereof, unless otherwise indicated, are intended to be synonymous and open-ended. A list of elements following the transitional phrase "comprises" or "includes" is a non-exclusive list; other elements may be present in addition to the elements specifically set forth in the list.

[0033] As used herein, the terms "substantial," "substantially," and variations thereof are intended to indicate that a described characteristic is equal to or approximately equal to a value or description. For example, a "substantially flat" surface is intended to indicate a surface that is flat or approximately flat. Furthermore, "substantially" is intended to indicate that two values ​​are equal or approximately equal. In some embodiments, "substantially" can indicate values ​​that are within about 10% of each other, e.g., within about 5% of each other, or within about 2% of each other.

[0034] As used herein, the terms "electrically connected," "electrically connecting," and variations thereof mean connected by a conductor that does not include molten material (e.g., molten glass). A first element electrically connected to a second element can include additional elements between the first and second elements, such that the additional elements are also electrically connected to the first and second elements. That is, a first element electrically connected to a second element should not be interpreted as excluding the presence of additional conductive elements in the connection. Typically, such conductors can include, but are not limited to, metal wiring or cables, bus bars, and the like. An electrical connection can further include other components, including, but not limited to, electrical connectors (e.g., plugs, tabs, lugs, bolts, etc.) that facilitate connection between components, electrical control devices such as current and / or voltage controllers, current and / or voltage measurement devices, and the like.

[0035] As used herein, "refractory" refers to a non-metallic material having chemical and physical properties that make it suitable for use as a component of a structure or system exposed to environments exceeding 538°C.

[0036] 1 is an exemplary glass manufacturing apparatus 10. In some embodiments, the glass manufacturing apparatus 10 can include a glass melting furnace 12 that includes a melting vessel 14. In addition to the melting vessel 14, the glass melting furnace 12 can optionally include one or more additional components, such as heating elements (e.g., combustion burners and / or electrodes) configured to heat the raw materials and convert the raw materials into molten glass. For example, the melting vessel 14 can be an electrically boosted melting vessel, where energy is applied to the raw materials through both combustion burners and direct heating, with an electric current being passed through the raw materials, which adds energy via Joule heating of the raw materials.

[0037] In further embodiments, the glassmelting furnace 12 may include other thermal management devices (e.g., isolation components) that reduce heat loss from the melting vessel. In yet other embodiments, the glassmelting furnace 12 may include electronic and / or electromechanical devices that facilitate melting of the raw materials into a glass melt. The glassmelting furnace 12 may include support structures (e.g., support chassis, support members, etc.) or other components.

[0038] The melting vessel 14 can be formed from a refractory material such as a refractory ceramic material (e.g., a refractory ceramic material comprising alumina or zirconia), which can alternatively or in any combination include other refractory materials such as yttrium (e.g., yttria, yttria-stabilized zirconia, yttrium phosphate), zircon (ZrSiO4), or alumina-zirconia-silica, or chromium oxide. In some examples, the melting vessel 14 can be constructed from refractory ceramic bricks.

[0039] In some embodiments, the glass melting furnace 12 can be incorporated as a component of a glass manufacturing apparatus configured to produce glass articles, such as glass ribbons, while in further embodiments, the glass manufacturing apparatus can be configured to form other glass articles, such as, but not limited to, glass rods, glass tubes, glass envelopes (e.g., glass envelopes for lighting devices, e.g., light bulbs), and glass lenses, although many other glass articles are contemplated. In some examples, the melting furnace can include glass manufacturing apparatus, including slot draw apparatus, float bath apparatus, downdraw apparatus (e.g., fusion downdraw apparatus), updraw apparatus, press apparatus, rolling mill apparatus, tube draw apparatus, or any other glass manufacturing apparatus that would benefit from the present disclosure. By way of example, FIG. 1 schematically illustrates the glass melting furnace 12 as a component of a fusion downdraw glass manufacturing apparatus 10 for fusion drawing a glass ribbon or winding a glass ribbon onto a spool for subsequent processing into individual glass sheets. As used herein, fusion draw involves flowing molten glass onto both sides of a forming body, with the resulting two streams of molten material joining or "melting" at the bottom of the forming body.

[0040] Glassmelting furnace 12 may optionally include upstream glass-making equipment 16 located upstream of melting vessel 14. In some examples, some or all of upstream glass-making equipment 16 may be incorporated as part of glassmelting furnace 12.

[0041] As shown in the embodiment illustrated in FIG. 1 , the upstream glass manufacturing apparatus 16 can include a raw material storage bin 18, a raw material delivery device 20, and a motor 22 connected to the raw material delivery device 20. The raw material storage bin 18 can be configured to store an amount of raw material 24 that can be delivered to the melting vessel 14 of the glass melting furnace 12 through one or more feed ports, as indicated by arrow 26. The raw material 24 typically includes one or more glass-forming metal oxides and one or more modifiers. In some examples, the raw material delivery device 20 can be powered by the motor 22 to deliver a predetermined amount of raw material 24 from the raw material storage bin 18 to the melting vessel 14. In a further example, the motor 22 can power the raw material delivery device 20 to introduce the raw material 24 at a controlled rate based on a level of molten material (hereinafter, "molten glass") sensed downstream from the melting vessel 14 relative to the flow direction of the molten glass. As used herein, the term molten glass refers to any molten material ("melt") that can become a glass or glass-ceramic (e.g., ceramic phase particles embedded in a glass phase matrix) upon cooling. The raw materials 24 in the melting vessel 14 can then be heated to form molten glass 28. Typically, in the initial melting step, the raw materials are added to the melting vessel as granular material, such as various "sands." The raw materials 24 can also include scrap glass (i.e., cullet) from previous melting and / or forming operations. A combustion burner is typically used to initiate the melting process. In an electrically boosted melting process, once the electrical resistance of the raw materials has been sufficiently reduced, an electrical boost can be initiated by creating an electrical potential between electrodes placed in contact with the raw materials, thereby establishing a current through the raw materials, which typically enters or becomes molten.

[0042] Glass manufacturing apparatus 10 may also optionally include downstream glass manufacturing apparatus 30 located downstream of glass melting furnace 12 relative to the flow direction of molten glass 28. In some examples, a portion of downstream glass manufacturing apparatus 30 may be incorporated as part of glass melting furnace 12. However, in some examples, a first connecting conduit 32, described below, or other portions of downstream glass manufacturing apparatus 30 may be incorporated as part of glass melting furnace 12.

[0043] The downstream glass manufacturing apparatus 30 may include a first conditioning chamber, such as a fining vessel 34, located downstream of the melting vessel 14 and coupled to the melting vessel 14 by the above-referenced first connecting conduit 32. In some examples, the molten glass 28 may be gravity fed from the melting vessel 14 to the fining vessel 34 by the first connecting conduit 32. For example, gravity may drive the molten glass 28 from the melting vessel 14 to the fining vessel 34 through the internal passage of the first connecting conduit 32. The first connecting conduit 32 thus provides a flow path for the molten glass 28 from the melting vessel 14 to the fining vessel 34. However, it should be understood that other conditioning chambers may be located downstream of the melting vessel 14, for example, between the melting vessel 14 and the fining vessel 34. In some embodiments, a conditioning chamber may be utilized between the melting vessel and the fining vessel. For example, the molten glass from the primary melting vessel may be further heated or cooled in a secondary melting (conditioning) vessel to a temperature lower than the temperature of the molten glass in the primary melting vessel (melting vessel 14) before entering the fining vessel 34.

[0044] As previously described, gas bubbles can be removed from the molten glass 28 by various techniques. For example, the raw material 24 can include polyvalent compounds (i.e., fining agents), such as tin oxide, that undergo a chemical reduction reaction to release oxygen when heated. Other suitable fining agents include, but are not limited to, oxides of arsenic, antimony, iron, and cerium; however, because the elements arsenic and antimony are biologically toxic, the use of arsenic and antimony oxides may be discouraged in some applications for environmental reasons. The fining vessel 34 is heated, for example, to a temperature higher than the melting vessel temperature or the molten glass therein, thereby heating the fining agents. Oxygen produced by the temperature-induced chemical reduction of one or more fining agents contained in the molten glass enters pre-existing gas bubbles in the molten glass, increasing their size. The enlarged gas bubbles, with increased buoyancy, rise to the free surface of the molten glass in the fining vessel and are released from the fining vessel, as described in more detail below.

[0045] The downstream glass-making apparatus 30 may further include a mixing device 36, e.g., a separate conditioning chamber such as a stirred vessel, for mixing the molten glass flowing downstream from the fining vessel 34. The mixing device 36 may be used to provide a homogeneous molten glass composition, thereby reducing chemical or thermal inhomogeneities that may be present in the molten glass exiting the fining vessel. As shown, the fining vessel 34 may be coupled to the mixing device 36 by a second connecting conduit 38. In some embodiments, the molten glass 28 may be gravity-fed from the fining vessel 34 to the mixing device 36 by the second connecting conduit 38. For example, gravity may drive the molten glass 28 from the fining vessel 34 to the mixing device 36 through an internal passage of the second connecting conduit 38. Typically, the molten glass in the mixing device 36 includes a free surface, with a free space extending between the free surface and the top surface of the mixing device. As used herein, the term "free surface" refers to the interface between the molten glass and the gaseous atmosphere above the molten glass, i.e., the surface of the molten glass. Although mixing device 36 is shown downstream of fining vessel 34 relative to the flow direction of molten glass 28, mixing device 36 may be located upstream of fining vessel 34 in other embodiments. In some embodiments, downstream glass making equipment 30 may include multiple mixing devices, such as a mixing device upstream from fining vessel 34 and a mixing device downstream from fining vessel 34. These mixing devices may be of the same design or may be of different designs. In some embodiments, one or more of the vessels and / or conduits comprising downstream glass making equipment 30 may include static mixing vanes positioned to promote mixing and subsequent homogenization of the molten glass.

[0046] Heating of the finer 34, mixing device 36, and other metal components of the glass manufacturing apparatus, including, but not limited to, the first connecting conduit 32 and the second connecting conduit 38, can occur by direct heating. That is, electric flange assemblies 40 can be attached to the various metal components, and the electric flange assemblies 40 are in electrical communication with one or more power sources configured to supply electrical current to the electric flange assemblies 40. The electrical current passes through the walls of the metal components (e.g., vessels, conduits) between the flange assemblies 40, thereby heating the walls of the metal components by Joule heating, which subsequently heats the molten material 28 flowing therethrough. A more detailed discussion of the flange assemblies is provided further below.

[0047] In some embodiments, the second connecting conduit 38 can include two or more sections. For example, as shown in FIG. 2, the second connecting conduit 38 can include a first conduit section 38a including a proximal end 42, a distal end 44 opposite the proximal end 42, and a passageway 46 extending between the proximal and distal ends 42, 44. The proximal end 42 is connected to the fining vessel 34. The second connecting conduit 38 can further include a second conduit section 38b including a proximal end 48, a distal end 50, and a passageway 52 extending between the proximal and distal ends 48, 50. The proximal end 48 can be connected to the mixing device 36 (e.g., a mixing vessel). The first conduit section 38a can be rigidly joined to the outlet of the fining vessel 34 at the proximal end 42 of the first conduit section 38a by welding. Similarly, the second conduit section 38b can be rigidly joined to the inlet of the mixing device 36 at a proximal end 48 of the second conduit section 38b by welding. Additionally, the distal end 44 of the first conduit section 38a can be coupled to a distal end 50 of the second conduit section 38b. For example, in various embodiments, the first conduit section 38a can include a first electrical flange assembly 40a attached to the distal end 44, and the second conduit section 38b can include a second electrical flange assembly 40b attached to the distal end 50, with the first conduit section 38a and the second conduit section 38b positioned such that a gap 54 is formed between the first and second electrical flange assemblies 40a and 40b. The gap 54 can be, for example, in a range of about 1 mm to about 1 cm. As the molten glass 28 is conveyed through the first and second conduit sections 38a, 38b, it can penetrate the gap 54. When the molten glass in the gap is exposed to a colder environment outside the gap, the molten glass therein cools, increasing its viscosity and sealing the gap to prevent further leakage of the molten glass. This seal is referred to as a "glass seal." The glass seal can accommodate slight misalignment or movement of the joined components, such as during temperature changes, and can electrically insulate the first conduit section 38a from the second conduit section 38b, allowing for independent, direct heating.

[0048] The first and second electrical flange assemblies 40a, 40b are configured to allow electrical current to pass into and out of the respective first or second conduit sections 38a, 38b. For example, in some embodiments, the fining vessel 34 can include a third electrical flange assembly 40c positioned at or adjacent the junction between the proximal end 42 of the first conduit section 38a and the fining vessel 34. The first and third electrical flange assemblies 40a, 40c can thus be electrically connected to a power source 56a, which can supply electrical current to the first conduit section 38a through the first and third electrical flange assemblies 40a, 40c. The electrical current supplied thereby can heat the first conduit section 38a through direct heating as a function of the electrical resistance of the wall of the first connecting conduit section. While the first power source 56a is shown directly connected to the electrical flange assemblies 40a, 40c, in further embodiments, the first power source 56a can be in indirect electrical connection. For example, the first power source 56a may comprise a transformer, one side of the transformer winding (e.g., a primary winding) may be electrically connected to the electrical service of the facility housing the glass manufacturing equipment, and the other side of the transformer winding (e.g., a secondary winding) may be electrically connected to the first and third electrical flange assemblies 40a, 40c through a winding tap. Each of the electrical flange assemblies 40a-40c includes a body portion 58 that surrounds and attaches to a respective conduit or vessel portion to which it is attached, and one or more electrode portions 60 that extend from the body portion and provide attachment points for a power cable or bus bar that supplies electrical current to the flange assembly. Although not shown, in various embodiments, the electrical flange assemblies may include one or more rings (e.g., concentric rings) of different materials, thicknesses, and / or radial widths to control the distribution of electrical current around the flange assembly and into the respective conduit or vessel.

[0049] Although the fining vessel 34 is typically oriented so that its length is horizontal or substantially horizontal (e.g., within 1° of horizontal), as seen in FIG. 2, the first conduit section 38a can include a horizontally or substantially horizontally oriented first conduit section 38a1 and a second conduit section 38a2 that is inclined downward (e.g., relative to the horizontal) from the first conduit section 38a1 at an angle β along the longitudinal axis 62 of the first conduit section 38a1. As described herein, axes that extend downward relative to the horizontal and the local direction of molten glass flow (e.g., direction 63) are considered to extend at a negative angle, and axes that extend upward relative to the horizontal and the local direction of molten glass flow (e.g., direction 63) are considered to extend at a positive angle. Thus, the longitudinal axis 62 can form a negative angle β with respect to the horizontal axis 64. The downward slope of conduit portion 38a2 positions second conduit section 38b, which is connected to first conduit portion 38a via glass seal 66, completely below the plane defined by the free surface 68 of molten glass 28 within the fining vessel 34. That is, during operation, molten glass 28 conveyed through the fining vessel 34 is maintained at a level such that the free surface 68 of the molten glass within the fining vessel 34 defines a "free space" 70 within the fining vessel defined between the free surface 68 of the molten glass 28 and the fining vessel 34. Free space 70 contains a first atmosphere 72 that is free of molten glass and provides space for the accumulation of volatile gases and other materials that may be released from the molten glass. For example, certain constituents of molten glass (e.g., boron) can easily evaporate from the free surface of the molten glass. Additionally, various gases generated during the melting process can be released from the free surface. As described later herein, this first atmosphere can be vented to a second atmosphere 74 external to the fining vessel (e.g., the ambient atmosphere surrounding the glass manufacturing apparatus 10). Additionally, free space 70 is continuous within at least a portion of first conduit section 38a (e.g., adjacent to fining vessel 34) and also includes first atmosphere 72. The level (vertical position) of free surface 68 of the molten material is referred to as the "glass line," a term that can be used interchangeably herein with molten glass level.The glass line can be considered to be the level at which the molten glass wets the interior surface of the inner wall of the conduit.

[0050] Locating second conduit section 38b below the glass line, particularly below the smallest expected glass line, can minimize entrapment in the molten glass of gases contained in first atmosphere 72. Second conduit section 38b is positioned sufficiently below the glass line so that normal excursions above and below the glass line do not result in free space within second conduit section 38b.

[0051] As further shown in FIG. 2, additional flange assemblies can be provided. For example, a fourth electrical flange assembly 40d can be attached to the second conduit section 38b downstream from the second electrical flange assembly 40b, with the second and fourth electrical flange assemblies 40b, 40d, electrically connected to a second power source 56b. Current provided by the second power source 56b passes through the wall of the second conduit section 38b via the second and fourth electrical flange assemblies 40b, 40d. Similarly, a fifth electrical flange assembly 40e can be attached to the mixer 36 and electrically connected to a third power source 56c, with the electrical flange assemblies 40d and 40e providing current through the second conduit section 38b and a portion of the mixer 36 via the third power source 56c. Other electrical flange assemblies 40 can be provided at the mixer 36 and the finer 34. In some embodiments, multiple flange assemblies 40 and multiple power sources 56 may be provided in the finer 34 and other components of the downstream glass manufacturing equipment 30 to define multiple, individually controlled heating zones. Each heating zone may provide current of the same or different current amplitude and phase necessary to achieve a predetermined temperature within the individual temperature zone. For example, in some embodiments, it may be desirable to cool the molten glass flowing through the second connecting conduit 38 before entering the mixing device 36. Accordingly, the current in the first conduit section 38a may be controlled to have a smaller amplitude than the amplitude of the current in the second conduit section 38b, such that the temperature of the second conduit section 38b is lower than the temperature of the first conduit section 38a, thereby cooling the molten glass as it flows through the first and second conduit sections 38a and 38b.

[0052] Returning to FIG. 1 , the downstream glass manufacturing apparatus 30 may further include another conditioning chamber, such as a feed vessel 80 located downstream from the mixing device 36. The feed vessel 80 may condition the molten glass 28 being supplied to the downstream forming device. For example, the feed vessel 80 may function as an accumulator and / or a flow controller to condition and provide a consistent flow of molten glass 28 to a forming body 82 via an outlet conduit 84. The molten glass in the feed vessel 80 may, in some embodiments, include a free surface, with a free space extending upward from the free surface to the top of the feed vessel. As shown, the mixing device 36 may be coupled to the feed vessel 80 by a third connecting conduit 86. In some examples, the molten glass 28 may be gravity-fed from the mixing device 36 to the feed vessel 80 via the third connecting conduit 86. For example, gravity may drive the molten glass 28 from the mixing device 36 to the feed vessel 80 through an internal passage of the third connecting conduit 86.

[0053] The downstream glass manufacturing apparatus 30 may further include a forming apparatus 88 including the above-referenced forming body 82, which includes an inlet conduit 90. The outlet conduit 84 may be positioned to deliver molten glass 28 from the feed vessel 80 to the inlet conduit 90 of the forming apparatus 88. The forming body 82 in a fusion downdraw glass manufacturing apparatus may include a trough 92 disposed on the upper surface of the forming body and converging forming surfaces 94 (only one shown) that converge in the draw direction along a lower edge (root) 96 of the forming body, the converging forming surfaces defining the root. Molten glass delivered to the forming body trough 92 via the feed vessel 80, the outlet conduit 84, and the inlet conduit 90 overflows the walls of the forming body trough 92 and descends along the converging forming surfaces 94 as separate streams of molten glass. The separate streams of molten glass join below and along the root 96 to produce a single ribbon of molten glass 98 that is pulled from the root 96 along the draw surface in a draw direction 100 by applying downward tension to the ribbon, such as by gravity and / or a pulling roll assembly (not shown), to control the ribbon's dimensions as the molten glass cools and the viscosity of the molten glass increases. Thus, the ribbon 98 undergoes a viscoelastic transition to an elastic state, acquiring mechanical properties that give the ribbon 98 stable dimensional properties. The resulting glass ribbon 98 can, in some embodiments, be separated into individual glass sheets 102 by a glass separating device (not shown), while in further embodiments, the glass ribbon can be wound onto a spool and stored for further processing.

[0054] Components of the downstream glass-making equipment 30, including any of the connecting conduits 32, 38, 86, the fining vessel 34, the mixing device 36, the feed vessel 80, the outlet conduit 84, or the inlet conduit 90, can be formed from precious metals. Suitable precious metals include platinum group metals selected from the group consisting of platinum, iridium, rhodium, osmium, ruthenium, and palladium, or alloys thereof. For example, the downstream components of the glass-making equipment can be formed from a platinum-rhodium alloy containing about 70% to about 90% platinum and about 10% to about 30% rhodium by weight. However, other suitable metals for forming the downstream components of the glass-making equipment include molybdenum, rhenium, tantalum, titanium, tungsten, and alloys thereof.

[0055] Although the elements of the glass manufacturing apparatus 10 are shown and described as fusion downdraw glass manufacturing elements, the principles of the present disclosure can be applied to a wide variety of glass manufacturing processes. For example, melting vessels according to embodiments of the present disclosure can be used in a variety of glass manufacturing processes, such as fusion processes, slot draw processes, rolling processes, pressing processes, float processes, tube draw processes, etc.

[0056] As mentioned above, gas bubbles are removed from the molten material in the fining vessel 34. These bubbles include, but are not limited to, bubbles formed from trapped gases within granular piles of raw materials and / or cullet introduced into the melting system as these materials are melted; bubbles arising from chemical dissolution or reaction of raw materials throughout the melting process; and bubbles arising from reactions with other materials in the process, such as refractory or metallic components. Gas bubbles can include gases such as oxygen, nitrogen, water vapor, argon, sulfur dioxide, and carbon dioxide. Additionally, in various embodiments, gases can be intentionally introduced into the fining vessel (e.g., into the free space 70) via gas supply line 104 (see FIG. 3) to aid in the fining process. Such intentionally introduced gases can include nitrogen, helium, or other inert gases or combinations thereof. Water can be introduced in the form of steam or can be combined with an inert gas (e.g., a humidified gas). Furthermore, the high temperatures present in parts of the fining vessel (in some instances, near or exceeding 1700°C) can cause evaporation of one or more constituents of the molten glass (e.g., boron, sodium, and / or tin).

[0057] According to embodiments described herein, cover gas 106 may be injected into the free space 70 above the free surface 68 via the finer gas supply line 104. In some embodiments, the cover gas 106 may be a humidified cover gas. The humidified cover gas 106 includes water vapor and oxygen (O) and may further include a non-flammable carrier gas. As used herein, a non-flammable carrier gas is hydrocarbon-free and / or is not formed as a by-product of combustion during the glassmaking process and may include an inert gas such as, for example, nitrogen, although in further embodiments, the carrier gas may be another inert gas such as, for example, a noble gas such as helium, neon, argon, krypton, xenon, or any combination of the preceding inert gases. For example, in embodiments, neither the carrier gas nor, generally, any component of the humidifying gas is derived from a submerged-combustion burner in a glassmaking process (e.g., melting vessel) that relies on the combustion of a fuel (e.g., natural gas) as a source of humidity (e.g., water vapor).

[0058] The average oxygen (O) content of the humidified cover gas 106 should be equal to or greater than the oxygen content within the bubbles to prevent outward diffusion of oxygen from the bubbles. That is, the oxygen partial pressure in the atmosphere outside the bubbles should be at least equal to the oxygen partial pressure within the bubbles. Outward diffusion of oxygen from the bubbles into the surrounding atmosphere can cause the bubbles to shrink, which can then thicken the bubble walls. Thick bubble walls can prolong bubble implosion long enough to allow the bubbles to be re-entrained within the molten glass stream. Thus, in some embodiments, the oxygen partial pressure within the humidifying gas can be greater than the oxygen partial pressure within the bubbles to ensure bubble expansion.

[0059] The average oxygen content of the oxygen in the humidified cover gas 106 can be, for example, in the range of about 10% to about 90% by volume, e.g., about 15% to about 90% by volume, about 20% to about 90% by volume, about 30% to about 90% by volume, about 40% to about 90% by volume, about 50% to about 90% by volume, about 60% to about 90% by volume, about 70% to about 90% by volume, about 80% to about 90% by volume, about 10% to about 70% by volume, about 10% to about 60% by volume, about 10% to about 50% by volume, about 10% to about 40% by volume, about 10% to about 30% by volume, or about 10% to about 20% by volume (including all ranges and subranges therebetween). In some embodiments, the humidified cover gas 106 can include air.

[0060] In some embodiments, the presence of water vapor as a surfactant can counteract the effect of a lower oxygen partial pressure outside the cell walls than inside the cell walls. Therefore, it should be understood that the goal is to prevent bubble shrinkage, thereby thickening the cell walls and extending the bubble's persistence (delaying bubble bursting). Thus, the amount of oxygen and water vapor can be adjusted to prevent bubble shrinkage, which in some embodiments can result in a lower oxygen partial pressure outside the bubble than the oxygen partial pressure inside the bubble.

[0061] The dew point of the humidified cover gas 106 can be in the range of about 41° C. to about 92° C., such as in the range of about 60° C. to about 92° C. The remainder of the humidified cover gas can be an inert carrier gas.

[0062] The flow rate of the humidified cover gas 106 can be in a range from greater than 0 to about 80 standard liters per minute (slpm), e.g., in a range from about 10 slpm to about 80 slpm, from about 20 slpm to about 80 slpm, from about 40 slpm to about 80 slpm, such as from about 30 slpm to about 80 slpm, from about 50 slpm to about 80 slpm, from about 60 slpm to about 80 slpm, from about 70 slpm to about 80 slpm, from about 10 slpm to about 70 slpm, from about 10 slpm to about 60 slpm, from about 10 slpm to about 50 slpm, from about 10 slpm to about 40 slpm, from about 10 slpm to about 30 slpm, or from about 10 slpm to about 20 slpm.

[0063] In some embodiments, the fining vessel gas supply line 104 can be heated to thereby heat the humidified cover gas supplied to the fining vessel 34. For example, the fining vessel gas supply line 104, and thereby the humidified cover gas 106, can be heated by one or more heating elements 107, such as external electrical resistance heating elements 108, while in further embodiments, the fining vessel gas supply line 104 can be heated directly by establishing an electrical current directly within the fining vessel gas supply line in a manner similar to how the fining vessel 34 is heated. For example, the fining vessel gas supply line 104 can include one or more electrical flange assemblies 40 in electrical communication with a power source, as described for the fining vessel 34.

[0064] According to other embodiments described herein, a dry cover gas 106 can be injected into the free space 70 above the free surface 68 via the finer gas supply line 104. The dry cover gas 106, in various embodiments, comprises a relative humidity of about 1% or less, e.g., about 0.5% or less, about 0.1% or less, or about 0.05%, such as zero percent (0%), and can further comprise an inert gas (e.g., nitrogen), although in further embodiments the inert gas can be a noble gas such as helium, neon, argon, krypton, xenon, or any combination of the foregoing inert gases.

[0065] The average oxygen (O2) content of the dry cover gas 106 supplied to the fining vessel 34 should be less than the oxygen content within the bubbles to ensure outward diffusion of oxygen from the bubbles. That is, the partial pressure of oxygen in the cover gas outside the bubbles should be less than the partial pressure of oxygen within the bubbles. For example, in various embodiments, the dry cover gas 106 supplied to the fining vessel 34 can include an O2 content of 0.2% by volume or less, e.g., in the range of about 0.05% to about 0.2% by volume, such as in the range of about 0.075% to about 1.5% by volume. There should be sufficient oxygen in the cover gas to prevent reduction of the platinum-containing walls of the fining vessel due to high nitrogen concentrations in the cover gas. However, the concentration of oxygen should be low enough to prevent deleterious oxidation of the platinum-containing walls at high temperatures. Thus, in various embodiments, the dry cover gas 106 can be a mixture of nitrogen gas (greater than 50% by volume) containing oxygen in the range of about 0.05% to about 0.2% by volume and a relative humidity of about 0.5% or less. In other embodiments, the dry cover gas 106 can be a nitrogen gas containing oxygen in the range of about 0.075% to about 0.15% by volume and a relative humidity of about 0.1% or less. In still other embodiments, the dry cover gas 106 can be a nitrogen gas containing oxygen in the range of about 0.075% to about 0.15% by volume and a relative humidity of about 0.05% or less. In some embodiments, the dry cover gas 106 can include N2 at a concentration of 78% by volume or greater, e.g., about 85% by volume or greater, about 90% by volume or greater, about 95% by volume or greater, about 98% by volume or greater, or about 99.8% by volume or greater.

[0066] The low-oxygen, low-humidity atmosphere provided to the free space 70 via the dry cover gas 106 can result in a net flow of gas and / or vapor from within the bubbles on the surface of the molten glass 28 in the fining vessel 34 across the bubble film into the free space 70, where, as previously mentioned, released gas and / or vapor (e.g., water vapor) can exit the free space 70 through the vent. The release of gas and / or vapor diffusing from the bubble across the bubble film can result in bubble shrinkage. The shrinkage can cause the bubble to become too small to be re-entrained in the molten glass flow, allowing more time for the bubble to burst. In some embodiments, such shrinkage can result in complete collapse of the bubble.

[0067] The flow rate of the cover gas 106 can range from about 1 turnover per minute or more to about 1 turnover per hour or less, including all ranges and subranges therebetween. As used herein, "turnover" refers to the flow rate equivalent to free space per unit time. As an example, for a 1 liter volume, 1 turnover per minute refers to a gas flow rate equivalent to 1 liter meter per minute. Gas delivered at a rate of 2 turnovers per minute to a 4 liter volume refers to a flow rate of 8 liters per minute. The selected flow rate will depend on the size of the free space to which the cover gas is delivered. The flow rate of the cover gas can include, for example, a range of about 0.02 turnovers per minute to about 1 turnover per minute, a range of about 0.05 turnovers per minute to about 1 turnover per minute, a range of about 0.1 turnovers per minute to about 1 turnover per minute, a range of about 0.5 turnovers per minute to about 1 turnover per minute, or a range of about 0.8 turnovers per minute to about 1 turnover per minute, and all ranges and subranges therebetween.

[0068] In some embodiments, as an aid in identifying the source of blisters in finished glass articles resulting from a glass manufacturing process, a non-reactive gas, e.g., a noble gas such as argon, krypton, neon, or xenon, or another non-reactive gas, can be added at a predetermined concentration to the cover gas 106, e.g., the cover gas injected into the free space in a finer or other vessel (e.g., mixing device 36). That is, gas bubbles in the molten glass can be tagged with a detectable amount of the non-reactive gas as a means of determining the location for bubble formation. For example, a specific first non-reactive gas (hereinafter, the "tag" gas) can be added to the cover gas 106 supplied to the fining vessel 34, e.g., a gas mixing chamber in fluid communication with the respective vessel gas supply line (e.g., fining vessel gas supply line 104). Suitable tag gases can include, but are not limited to, argon, krypton, neon, helium, and xenon.

[0069] Blisters (gas bubbles) found in the finished glass article can be analyzed, for example, by mass spectrometry, to determine whether a first tag gas is present in the blisters at a concentration consistent with the concentration of the first tag gas added to the cover gas supplied to the fining vessel 34, thereby identifying the source of the blisters as the fining vessel. However, a tag gas concentration found in the blisters that does not match the concentration of the tag gas supplied to the fining vessel 34 can indicate that the source of the blisters is not the fining vessel. Similarly, a second tag gas, different from the first tag gas, can be added to a different vessel, such as the cover gas supplied to the mixing device 36. Analysis of the blisters in the glass article can then be used to determine the number (if any) of blisters containing the first tag gas and / or the number (if any) of blisters containing the second tag gas, thereby providing better identification and quantification of the source of the blisters. For example, if a second tag gas is found but not the first tag gas, the source of the blisters can be presumed to originate from the vessel into which the second tag gas was injected. The presence of both the first tag gas and the second tag gas in the bubble can indicate that the bubble survived transport between the vessels and is present at the surface of the molten glass in both vessels.

[0070] The tag gas or gases are typically not the majority gases that comprise the cover gas. For example, if the majority gas (>50%) that comprises the cover gas 106 is N, the cover gas can comprise less than 50% of the tag gas, and the tag gas is different from the majority gas.

[0071] 3 and 4 show the lower portion of an exemplary finer gas supply pipe 104, which penetrates the wall 120 of the finer 34 above the free surface 68 of the molten glass 28 in FIG. 3 and is shown in cross section in FIG. 4. The finer gas supply pipe 104 can extend through a reinforcing sleeve 122, where the finer gas supply pipe 104 penetrates the finer wall 120. Additionally, one or more reinforcing plates 124 are depicted in FIG. 4 as surrounding the reinforcing sleeve 122 and being located above and / or below the finer wall 120 and attached thereto. The reinforcing plates 124, reinforcing sleeve 122, and finer wall 120 can be attached to one another, such as by welding. For example, the reinforcing plates 124 can be welded to the finer wall 120 and the reinforcing sleeve 122. Additionally, in embodiments, the reinforcing sleeve 122 can be welded to the finer gas supply pipe 104. Because the reinforcing plate 124 and reinforcing sleeve 122 are all made from thin sheets of platinum alloy that can easily deform as the metal expands during initial heat-up of the system, they provide additional thickness to the finer wall and fining vessel gas feed line 104 where the gas feed line penetrates the finer. The additional thickness can provide greater strength to the gas feed line where it penetrates the finer wall and, in instances where the gas feed line is directly heated, can reduce heating at the penetration area by reducing the current flow through the joint (reducing electrical resistance).

[0072] The finer gas supply line 104 can include a closed bottom 126 and an exhaust port 128 located in the sidewall of the finer gas supply line 104 near the bottom of the finer gas supply line 104 and oriented such that the cover gas 106 is exhausted from the finer gas supply line 104 in a direction substantially parallel to the flow direction 130 of the molten glass in the finer 34 (e.g., oriented downstream). The substantially parallel flow of the cover gas 106 and molten glass 28 minimizes or eliminates direct impingement of the cover gas exiting the gas supply line on the molten glass surface and subsequent cooling of the molten glass surface. Such cooling can cause viscosity non-uniformities in the molten glass that can manifest as defects in the finished product. The side-port finer gas supply line 104 also reduces the chance of condensates, such as volatile glass constituents like boron, building up at the exhaust port and eventually dropping into the molten glass below.

[0073] As a result of the above process, a first atmosphere 72, contained within free space 70 and extending along the length of fining vessel 34 and at least a portion of first conduit section 38a, may include any one or more of the preceding gases and vapors, and this atmosphere must be vented from the fining vessel. Typically, venting of the fining vessel 34 has been accomplished through a vent tube extending from the top of the fining vessel. However, such an arrangement can have undesirable consequences. For example, volatile materials evaporating from the molten glass can condense on the interior surface of the vent tube. If a sufficient amount of condensate accumulates, the condensate can break off and fall into the molten glass below, thereby contaminating the molten glass. Additionally, a straight vent tube extending from the top of the fining vessel can be difficult to clean without dislodging condensate, which can also fall through the vent tube and contaminate the molten glass below. Past efforts to mitigate contamination have included creating bends in the vent pipe so that, while the vent pipe initially rises vertically from the fining vessel, it bends sharply to prevent dislodged condensate from falling into the fining vessel. However, such sharp bends make it difficult to clean beyond the bend (e.g., between the bend and the fining vessel) from outside the fining vessel, as cleaning tools cannot reach beyond the bend from the vent pipe exit.

[0074] To overcome these challenges, embodiments of an improved venting device are described. Accordingly, in some embodiments, the diameter of the first conduit section 38a can be increased compared to conventional connecting conduits. Referring to FIGS. 5 and 6 , the larger diameter conduit can provide increased free space 70, allowing the vent pipe 200 to be positioned near the top 202 of the first conduit section 38a but sufficiently above the free surface of the molten glass 28 to prevent the molten glass 28 from entering the vent pipe 200. For example, the inlet of the vent pipe 200 can be positioned at least 2.5 cm above the glass line. Referring to the cross-sectional view of FIG. 6 taken along line 6-6 of FIG. 5, in various embodiments, the connection between the vent pipe 200 and the first conduit section 38a can be positioned at an angle ranging from about 5° to about 60° relative to the vertical, e.g., from about 10° to about 45°, where the 0° position refers to the connection at the vertical top of the first conduit section 38a (i.e., the 12 o'clock position).

[0075] In some embodiments, the top of first conduit section 38a can be higher than the top of fining vessel 34 relative to bottom 204 of fining vessel 34. Vent tube 200 can be a straight vent tube extending downwardly from proximal end 206 along central longitudinal axis 208 at a negative angle α relative to the horizontal and terminating at distal end 210, the vent tube defining passageway 212 therethrough (see FIG. 11 ). As shown, no portion of vent tube 200 extends upwardly from proximal end 206 either vertically or at a positive angle above the horizontal. Angle α can be in a range of greater than 0° to less than 90°, such as in the range of about 3° to about 80°, about 3° to about 40°, about 3° to about 20°, or about 3° to about 10°. In this manner, vent tube 200 provides fluid communication between free space 70 adjacent the top of first conduit section 38a and also provides a sufficient distance between free surface 68 of molten glass 28 and the bottom of proximal end 206 of vent tube 200 to accommodate upward excursion of the glass line without blocking the vent tube. First atmosphere 72 remains in fluid communication with second external atmosphere 74 via vent tube 200 during operation of the glass making apparatus. At the same time, vent tube 200 allows access throughout the entire length of the vent tube from outside second conduit 38 (e.g., first conduit section 38a), which facilitates cleaning without the risk of particulate matter falling into molten glass 28.

[0076] 7, in other embodiments, it may not be necessary to expand the entire first conduit section 38a. Instead, a portion of the first conduit section 38a may be expanded upward to form a large dome-shaped portion 214 above the free surface 68 of the molten glass 28 within the first conduit section 38a. The dome-shaped portion 214 may, in some embodiments, extend above the finer 34. That is, the top of the dome-shaped portion 214 may extend vertically upward a greater distance d1 from the bottom of the finer 34 than a distance d2 from the top of the finer 34. As discussed above, the vent tube 200 may be a straight vent tube connected to the dome-shaped portion 214 at the proximal end 206 and extending downward along the central longitudinal axis 208 from the proximal end 206 at a negative angle α relative to the horizontal, with the vent tube 200 terminating at the distal end 210. As previously mentioned, no portion of the vent tube 200 extends upward from the proximal end 206 at any positive angle, either vertically or above horizontal. The angle α can range from greater than 0° to less than 90°, such as from about 3° to about 80°, from about 3° to about 40°, from about 3° to about 20°, or from about 3° to about 10°.

[0077] The large, upwardly extending dome-shaped portion 214 allows a sufficient distance between the free surface 68 of the molten glass 28 and the bottom of the proximal end 206 of the vent pipe 200 to accommodate upward excursions of the glass line during operation of the glass-making equipment. In other words, the free space 70 of the finer 34 extends into the first conduit section 38a, and the inlet of the vent pipe 200 is positioned above the first conduit section 38a (e.g., dome portion 214) so ​​that the proximal end 206 of the vent pipe 200 is positioned above the maximum expected height of the glass line to prevent upward excursions of the molten glass from blocking the vent pipe during operation of the glass-making equipment. For example, the inlet of the vent pipe 200 can be located at least 2.5 cm above the glass line.

[0078] Although fining vessel 34 is shown to have a circular cross-section in a plane perpendicular to the fining vessel's central longitudinal axis 216, in further embodiments, fining vessel 34 can include a non-circular cross-sectional shape, such as an oval cross-sectional shape. Similarly, vent pipe 200 can have a non-circular cross-sectional shape.

[0079] In some embodiments, the vent pipe 200 shown in FIG. 8, viewed from the rear along line 8-8 in FIG. 7, can include an electrical flange 220. The electrical flange 220 is configured to extend completely around the vent pipe 200 at or near the distal end 210 and can include an extension portion 222, e.g., an electrode portion, that serves as a connection point for an electrical cable, bus bar, or other electrical conductor. The electrical flange 220 can include a single homogeneous element and can include, for example, a platinum-containing material such as a platinum-rhodium alloy. In any of the preceding embodiments, the vent pipe 200 can include the electrical flange 220 at the distal end 210, and a power source can provide electrical current between the electrical flange 220 and either or both of the first electrical flange assembly 40a and / or the third electrical flange assembly 40c. In some embodiments, the power source can include an additional secondary winding of the first power source 56a or a tap from a single secondary winding. Thus, the vent tube 200 can be heated directly by electrical current in the vent tube wall. That is, the vent tube can function as a heating element. As shown in Figures 10 and 11, in various embodiments, the wall of the vent tube 200 at and / or near the proximal end 206, where the vent tube 200 is attached to the first conduit section 38a, can be thicker than the wall at the distal end 118, or thicker than the wall of the vent tube intermediate the proximal end 206 and the distal end 210. For example, the proximal end 206 can include multiple layers.

[0080] FIG. 11 illustrates one embodiment of the proximal end 206, which includes a first inner layer 224 and a second outer layer 226. The inner layer 224 can be the vent tube itself, extending from the proximal end 206 to the distal end 210, and the second layer 226 can be a cladding layer disposed over the vent tube at the proximal end 206. In such a manufacturing approach, the second layer 226 can be attached to the vent tube 200 by welding. The thickened proximal end strengthens the attachment area of ​​the vent tube 200 where it attaches to the fining vessel 34 and helps control electrical current passing through the attachment point, thereby avoiding hot spots that could degrade the connection. Thus, in some embodiments, the thickened portion of the proximal end 206 can vary in thickness circumferentially as needed to evenly distribute electrical current around the circumference of the vent tube at the proximal end 206. Similarly, the area of ​​the first conduit section 38a at the attachment of the vent pipe 200 may also be thickened relative to the area displaced away from the vent pipe to strengthen the connection point and aid in current distribution. The wall of the connecting conduit 38 at the attachment of the vent pipe 200 may be thickened, such as by welding, a reinforcing plate 228. In some embodiments, the distal end 210 of the vent pipe 200, where the electrical flange 220 is joined to the vent pipe, may be thickened in a similar manner to the proximal end 206, by attaching a sleeve around the vent pipe at the distal end 210.

[0081] In further embodiments, the vent pipe 200 can be heated by radiant and / or conductive heat from a separate heating element, such as a heating coil, positioned proximate to the vent pipe. For example, in some embodiments, the heating element can be coiled around the vent pipe but spaced apart from the vent pipe. In some embodiments, multiple heating elements can be positioned at various locations around the circumference of the vent pipe 200. To maintain the temperature of the vent pipe, the vent pipe 200 can be surrounded by, e.g., wrapped in, a thermal insulating material (not shown), such as, for example, a ceramic insulating material.

[0082] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present disclosure without departing from the spirit and scope of the disclosure, and therefore, the present disclosure is intended to cover all such modifications and variations provided they come within the scope of the appended claims and their equivalents.

Claims

1. 1. A method of manufacturing a glass article, comprising: flowing molten material through a first vessel to a second vessel downstream from the first vessel, the molten material flowing through a conduit connecting the first vessel to the second vessel, the first vessel and the conduit defining a continuous free space above a free surface of the molten material, the free space extending at least a portion of the conduit; venting a first atmosphere contained in the free space to a second atmosphere outside the first container through a vent tube having a proximal end, a distal end opposite the proximal end, and a passageway extending between the proximal end and the distal end, the proximal end being connected to the conduit adjacent an upper portion of the conduit and above the free surface, the vent tube extending downward and away from the conduit along a longitudinal axis at an angle α with respect to the horizontal to provide fluid communication between the first atmosphere and the second atmosphere; a first portion of the conduit extending horizontally from the first container, the vent pipe connected to the first portion of the conduit; At least a second portion of the conduit extends downwardly relative to a first portion of the conduit. A method characterized by:

2. the vent tube is straight between the proximal end and the distal end; The method of claim 1.

3. The angle α is in the range of greater than 0° to less than 90°. The method according to claim 1 or claim 2.

4. The angle α is in the range of 3° to 10°. The method of claim 3.

5. further comprising the step of heating the vent pipe during the venting. The method according to any one of claims 1 to 4.

6. the heating step includes establishing an electric current within a wall of the vent pipe; The method of claim 5.

7. The first vessel is a clarification vessel and the second vessel is a mixing vessel.

7. The method according to any one of claims 1 to 6.

8. and flowing a cover gas through a gas delivery pipe connected to the first container into the free space. The method according to any one of claims 1 to 7.

9. further comprising the step of heating the conduit while the molten material flows through the conduit. The method according to any one of claims 1 to 8.

10. the wall thickness of the conduit varies along the length of the conduit; The method according to any one of claims 1 to 9.

11. In a cross section of the conduit perpendicular to a longitudinal axis of the conduit, a wall thickness of the conduit at a first portion of the cross section is different from a wall thickness of the conduit at a second portion of the cross section. The method according to any one of claims 1 to 9.

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