WO2016144715A2

WO2016144715A2 - Apparatus and method for conditioning molten glass

Info

Publication number: WO2016144715A2
Application number: PCT/US2016/020798
Authority: WO
Inventors: Gilbert De Angelis; Pierre LARONZE
Original assignee: Corning Incorporated
Priority date: 2015-03-06
Filing date: 2016-03-04
Publication date: 2016-09-15
Also published as: TW201641451A; WO2016144715A3; CN107531535B; CN107531535A; KR20170118891A; JP2018510115A; KR102509016B1; JP6761425B2; TWI685473B

Abstract

Disclosed is an apparatus for bubbling a gas into molten glass. The bubbler may include a sleeve, a nozzle secured to one end of the sleeve and a capillary member slidably positioned within sleeve below the nozzle. The capillary member is coupled to a positioning assembly configured to translate the capillary member within the sleeve.

Description

APPARATUS AND METHOD FOR CONDITIONING MOLTEN GLASS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 62/129,210, filed on March 6, 2015, the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND

Field

[0002] The present disclosure is directed to an apparatus for conditioning a molten glass, and more particularly for injecting a gas into the molten glass (e.g. bubbling).

Technical Background

[0003] The manufacture of glass on a commercial scale is typically carried out within a refractory ceramic melting vessel wherein raw materials (batch) are added to the melting vessel and heated to a temperature at which the batch undergoes chemical reactions to produce the molten glass. Several methods of heating the batch can be used, including gas-fired burners, an electric current, or both.

[0004] Conditioning of the molten glass, for example fining and homogenizing, can be carried out in certain portions of the melting vessel structure or in other vessels located downstream from the melting vessel and connected to the melting vessel by conduits. In certain processes bubbling a gas into the molten glass may be used to agitate and improve homogenization of the molten glass or to manipulate the redox state of the batch constituents, for example fining agents.

[0005] Conventional bubblers often utilize a ceramic tube directly exposed, at least at a face, to the high temperature corrosive environment provided by the molten glass. Accordingly, they have exhibited significant corrosion of the ceramic tube starting at the exposed surface. For hard glasses typically used in the manufacture of optical articles, such as glass for display substrates, a typical temperature range for the molten glass in the melting vessel is from about 1500 °C to about 1550 °C. The temperature of molten glass in the fining vessel can be considerably greater, and may approach 1700 °C. Additionally, the molten glass may freeze, or condensate can block outlets of the passages and stop bubble formation or create a crystalline phase which cannot be dissolved. There is also potential for defects and/or obstruction within the bubbler passages. Moreover, the gas supplied to create the bubbles can potentially leak at the bottom of the bubbler support between the platinum cladding and the support, thereby decreasing gas pressure and reducing process stability. When such detrimental outcomes occur, the bubbler must be replaced.

[0006] Bubblers are a viable and inexpensive solution to improve glass quality and potentially glass fining. However, because of the noted problems in high temperature operation,

modification is needed to address present shortfalls.

SUMMARY

[0007] Bubblers for injecting bubbles of gas into a vessel including molten glass within a volume defined by the vessel have long been used to enhance, for example, glass melting. For example, the bubbling process can augment natural convection currents during a melting process, thereby adding to the homogeneity of the molten glass and the glass article made therefrom. However, molten glass can be highly corrosive, and the combination of high temperature and corrosive environment can severely damage conventional bubblers over a relatively short period of time.

[0008] Accordingly, described herein in one aspect is an apparatus for conditioning molten glass comprising a vessel including an interior volume. A bubbler extends into the volume of the vessel, the bubbler comprising a sleeve including an interior passage extending therethrough, a nozzle secured to a first end of the sleeve, the nozzle including an interior passage extending between an inlet orifice and an outlet orifice, and a capillary member comprising a plurality of capillary passages extending therethrough. The sleeve and the nozzle may comprise platinum. The capillary member is slidably engaged within the interior passage of the sleeve. The nozzle may comprise a recessed portion, wherein the recessed portion is positioned within the interior passage of the sleeve.

[0009] The apparatus may further include a cooling apparatus to cool portions of the apparatus. Additionally, a screw member may be coupled to the cooling apparatus. The screw member may also be coupled to the sleeve. The cooling apparatus, however, does not directly cool that portion of the bubbler (sleeve and nozzle) that extends into the molten glass. [0010] In example embodiments a positioning assembly can be rotatably coupled to the screw member and the capillary member can be coupled to a gas supply pipe which is, in turn, rotatably coupled to the positioning assembly such that rotation of the positioning assembly about the screw member causes the positioning device to translate along the screw member. With the gas supply pipe rotatably coupled to the positioning assembly and the capillary member coupled to the gas supply pipe, movement of the positioning assembly along the screw member causes the capillary member to move within the sleeve, thereby providing the ability to compensate for corrosion of the capillary member.

[0011] To limit the size of the bubbles produced by the bubbler, the nozzle may comprise an outer profile tapering in a direction toward the outlet orifice. The interior passage of the nozzle may also comprise an intermediate chamber with a diameter larger than a diameter of the outlet orifice to serve as a location for gas supplied from the many passages of the capillary member to join.

[0012] The nozzle may be secured to the sleeve by a perimeter weld around a seam between the nozzle and the sleeve to prevent gas pressure within the nozzle from separating the nozzle from the sleeve. In addition, or alternatively, the nozzle may also be secured to the sleeve by a plurality of plug welds located about a periphery of the sleeve. Preferably, both a seam weld and plug welds are used to secure the nozzle to the sleeve.

[0013] At least a portion of the sleeve can comprise a ceramic coating, in particular that portion of the sleeve positioned within the cooling apparatus. The ceramic coating aids in preventing diffusion welding of the sleeve to an inner wall of the cooling apparatus if long-term contact between the two occurs. In addition, at least a portion of the cooling apparatus can comprise a ceramic coating to prevent corrosion (e.g. oxidation) of the cooling apparatus.

[0014] The apparatus may further comprise a sealing gasket positioned within the screw member between the capillary member and the screw member. The sealing gasket rests on a sealing lip positioned within an interior passage of the screw member, and a fitting, for example a screw fitting, compresses the sleeve against the sealing gasket via a flange on the sleeve. The gasket includes a passage through which the sleeve extends, and the gasket further seals around the sleeve, thereby preventing leakage of gases, such as atmospheric gases through the screw member passage, and in a gap between the sleeve and the capillary member, into the molten glass, or vice versa. [0015] The vessel may be a melting vessel, a fining vessel or a cooling vessel. The vessel may also be any one or more of the connecting conduit.

[0016] The output orifice of the nozzle comprises an orifice area, which is the cross sectional area of the orifice in a plane perpendicular to a central axis of the nozzle, and each capillary passage of the plurality of capillary passages comprises an output orifice with an orifice area. The sum of the orifice areas of the plurality of capillary passages can be substantially equal to the orifice area of the output orifice of the nozzle. Thus, the volume flow rate of gas from the nozzle outlet orifice is substantially matched to the volume flow rate of gas from the capillary member.

[0017] In another aspect an apparatus for conditioning molten glass is disclosed comprising a vessel comprising an interior volume and a bubbler extending into the volume. The bubbler comprises a sleeve including an interior passage extending therethrough, a nozzle secured to a first end of the sleeve, and a capillary member comprising a plurality of passages extending through the capillary member substantially parallel with a central longitudinal axis of the capillary member. The sleeve and the nozzle can comprise platinum. The capillary member is slidably engaged within the interior passage of the sleeve. A screw member may be coupled to the sleeve and a positioning assembly may be rotatably engaged with the screw member and configured such that rotation of the positioning assembly about the screw member translates the capillary member within the sleeve.

[0018] The apparatus may further comprise a cooling apparatus coupled to the screw member. A gas supply pipe may be rotatably coupled to the positioning assembly and further coupled to the capillary member.

[0019] The vessel can be a melting vessel, a fining vessel or a cooling vessel. In addition, or alternatively, the vessel may be a connecting conduit.

[0020] In still another aspect a method of conditioning a molten glass is disclosed comprising flowing molten glass into or out of a vessel, the vessel including a bubbler extending into the molten glass and comprising an outlet orifice. The bubbler comprises a sleeve, a nozzle and a capillary member slidably positioned in the sleeve. The method may further comprise pressurizing the nozzle with a gas supplied through the capillary member, a pressure of the gas sufficient to prevent the molten glass from entering the nozzle and contacting the capillary member. [0021] The rate of bubble release from the nozzle may be zero bubbles per minute over a period of at least one hour. The rate of bubble release from the nozzle may be in a range from 1 to 100 bubbles per minute.

[0022] The temperature of the molten glass can be in a range from about 1550 °C to about 1690 °C.

[0023] The method may further comprise after pressurizing the nozzle, de-pressurizing the nozzle such that molten glass enters the nozzle, then re-pressurizing the nozzle, thereby forcing the molten glass from the nozzle.

[0024] It is to be understood that both the foregoing general description and the following detailed description present embodiments of the present disclosure, and are intended to provide an overview or framework for understanding the nature and character of the embodiments as they are described and claimed. The accompanying drawings are included to provide a further understanding of the embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure, and together with the description serve to explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic view of an example glass making apparatus according to the present disclosure;

[0026] FIG. 2 is a simplified cross sectional view of a bubbler in accordance with an

embodiment of the present disclosure;

[0027] FIG. 3 is a cross sectional perspective view of a portion of the bubbler of FIG. 2 showing a nozzle secured to an end of a sleeve, and a capillary member slidably positioned within the sleeve;

[0028] FIG. 4 is a cross sectional view of the nozzle shown in FIG. 4 in a plane parallel with a central longitudinal axis of the nozzle;

[0029] FIG. 5 A is a cross sectional view of the sleeve, nozzle and capillary member of FIG. 4 and including a cooling apparatus;

[0030] FIG. 5B is a close-up view of a portion of the view of FIG. 5 A showing a coating applied to an exterior surface of the sleeve; [0031] FIG. 6 is a perspective view of an example cooling apparatus according to embodiments of the present disclosure, shown without the sleeve or nozzle installed;

[0032] FIG. 7 is a perspective view of a portion of the cooling device of FIG. 6, shown with the sleeve and nozzle installed;

[0033] FIG. 8A is a cross sectional view of a portion (top end) of a screw member coupled to portions of the sleeve and cooling apparatus, and showing sealing gaskets sealing to the capillary member;

[0034] FIG. 8B is a cross sectional view of a portion (bottom end) of the screw member of FIG. 8A showing the capillary member coupled to the gas supply tube;

[0035] FIG. 9 is a perspective view of the sleeve of FIG. 8 A illustrating the flange used to couple the sleeve to the screw member;

[0036] FIG. 1 OA is a perspective view of a portion (top end) of an example positioning assembly coupled to the screw member of FIGS. 8 A and 8B according to embodiments of the present disclosure;

[0037] FIG. 10B is a perspective view of a portion (bottom end) of the positioning assembly of FIG. 10A showing the connection between the gas supply tube and a gas line;

[0038] FIG. 11 is a schematic view of another glass making apparatus according to embodiments of the present disclosure wherein the glass making apparatus includes a downstream glass making apparatus including a molten glass conditioning vessel positioned between a melting vessel and a fining vessel, wherein the molten glass conditioning vessel includes bubblers in accordance with embodiments of the present disclosure; and

[0039] FIG. 12 is a schematic view of yet another glass making apparatus according to embodiments of the present disclosure wherein bubblers disclosed herein may be positioned in a fining vessel downstream of the melting vessel.

DETAILED DESCRIPTION

[0040] Apparatus and methods will now be described more fully hereinafter with reference to the accompanying drawings in which example embodiments of the disclosure are shown.

Whenever possible, the same reference numerals are used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Unless otherwise indicated, figures of the drawings may not be to scale, or even in scale from one figure to another figure.

[0041] Ranges can be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0042] Directional terms as used herein, for example up, down, right, left, front, back, top, bottom, are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0043] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, it is in no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; the number or type of embodiments described in the specification.

[0044] The terms "substantial," "substantially," and variations thereof as used herein are intended to note that a described feature is equal or approximately equal to a value or

description.

[0045] While various features, elements or steps of particular embodiments may be disclosed using the transitional phrase "comprising," it is to be understood that alternative embodiments, including those that may be described using the transitional phrases "consisting" or "consisting essentially of," are implied. Thus, alternative embodiments to an apparatus that comprises A+B+C can include embodiments where an apparatus consists of A+B+C and embodiments where an apparatus consists essentially of A+B+C.

[0046] As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a" component includes aspects having two or more such components, unless the context clearly indicates otherwise. [0047] Aspects of the disclosure include apparatus for conditioning batch into a molten glass, and more particularly to apparatus for conditioning the molten glass. Furnaces of the disclosure may be provided for a wide range of applications to heat gases, liquids and/or solids. In one example, apparatus of the present disclosure are described with reference to a glass melting system configured to melt batch into molten glass and convey the molten glass to downstream processing equipment.

[0048] Methods of the disclosure may condition the molten glass in a wide variety of ways. For instance, the molten glass may be conditioned by heating the molten glass to a temperature greater than an initial temperature, for example greater than a melting vessel temperature. In further examples, the molten glass may be conditioned by maintaining a temperature of the molten glass or by reducing the rate of heat loss that might otherwise occur by inputting heat energy into the molten glass and thereby controlling the cooling rate of the molten glass.

[0049] Methods of the disclosure may condition the molten glass with a fining vessel, a mixing vessel or other vessels. Optionally, the apparatus may include one or more further components such as thermal management devices, electronic devices, electromechanical devices, support structures or other components to facilitate operation of the glass manufacturing apparatus including conveying vessels (conduits) that transport the molten glass from one location to another location.

[0050] Shown in FIG. 1 is an example glass manufacturing apparatus 10. In some examples, the glass manufacturing apparatus 10 can comprise a glass melting furnace 12 that can include a melting vessel 14. In addition to melting vessel 14, glass melting furnace 12 can optionally include one or more further components such as heating elements (e.g., combustion burners or electrodes) configured to heat the batch and convert the batch into molten glass. In further examples, glass melting furnace 12 may include thermal management devices (e.g., insulation components) configured to reduce heat lost from a vicinity of the melting vessel. In still further examples, glass melting furnace 12 may include electronic devices and/or electromechanical devices configured to facilitate melting of the batch into a glass melt. Still further, glass melting furnace 12 may include support structures (e.g., support chassis, support member, etc.) or other components.

[0051] Glass melting vessel 14 is typically comprised of refractory material, such as a refractory ceramic material. In some examples, glass melting vessel 14 may be constructed from refractory ceramic bricks, for example refractory ceramic bricks comprising alumina or zirconia. Glass melting vessel 14 may further comprise one or more bubblers 16. Bubblers 16 may be positioned in a floor of the melting vessel and extend upward into the molten glass occupying a volume of the melting vessel. In other embodiments, for example for other vessels, the bubblers may be positioned in other orientations. Bubblers 16 can be configured to introduce a gas into the molten glass, such as but not limited to oxygen, nitrogen, helium, argon, carbon dioxide and mixtures thereof. Bubblers 16 may be positioned near an inlet region of the melting vessel, near the outlet region of the melting vessel, or in an intermediate position within the melting vessel.

[0052] In some examples, the glass melting furnace may be incorporated as a component of a glass manufacturing apparatus configured to fabricate a glass ribbon. In some examples the glass melting furnace of the disclosure may be incorporated as a component of a glass manufacturing apparatus comprising a slot draw apparatus, a float bath apparatus, a down-draw apparatus, an up-draw apparatus, a press-rolling apparatus or other glass ribbon manufacturing apparatus. By way of example, FIG. 1 schematically illustrates glass melting furnace 12 as a component of a fusion down-draw apparatus 10 for fusion drawing a glass ribbon for subsequent processing into glass sheets.

[0053] The glass manufacturing apparatus 10, for example the fusion down draw apparatus of FIG. 1, can optionally include an upstream glass manufacturing apparatus 18 that is positioned upstream relative to glass melting vessel 14. In some examples, a portion of, or the entire upstream glass manufacturing apparatus 18, may be incorporated as part of the glass melting furnace 12.

[0054] As shown in the illustrated example, the upstream glass manufacturing apparatus 18 can include a storage bin 20, a batch delivery device 22 and a motor 24 connected to the batch delivery device. Storage bin 20 may be configured to store a quantity of batch 26 that can be fed into melting vessel 14 of glass melting furnace 12, as indicated by arrow 28. In some examples, batch delivery device 22 can be powered by motor 24 configured to deliver a predetermined amount of batch 26 from the storage bin 20 to melting vessel 14. In further examples, motor 24 can power batch delivery device 22 to introduce batch 26 at a controlled rate based on a sensed level of molten glass downstream from melting vessel 14. Batch 26 within melting vessel 14 can thereafter be heated to form molten glass 30. [0055] Glass manufacturing apparatus 10 can also optionally include a downstream glass manufacturing apparatus 32 that is positioned downstream relative to the glass melting furnace 12. In some examples, a portion of the downstream glass manufacturing apparatus 32 may be incorporated as part of glass melting furnace 12. For instance, first connecting conduit 34 discussed below, or other portions of the downstream glass manufacturing apparatus 32, may be incorporated as part of the glass melting furnace 12. Elements of the downstream glass manufacturing apparatus, including first connecting conduit 34, may be formed from a precious metal. 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, downstream components of the glass manufacturing apparatus may be formed from a platinum-rhodium alloy including 70 to 90% by weight platinum and 10 to 30% by weight rhodium.

[0056] The downstream glass manufacturing apparatus 32 can include a first conditioning vessel such as fining vessel 36, located downstream from melting vessel 14 and coupled to melting vessel 14 by way of the above-referenced first connecting conduit 34. In some examples, molten glass 30 may be gravity fed from melting vessel 14 to fining vessel 36 by way of first connecting conduit 34. For instance, gravity may cause molten glass 30 to pass through an interior pathway of first connecting conduit 34 from melting vessel 14 to fining vessel 36.

[0057] Within fining vessel 36, bubbles may be removed from molten glass 30 by various techniques. For example, batch 26 may include one or more multivalent compounds (i.e. fining agents) such as tin oxide that, when heated, undergo a chemical reduction reaction and release oxygen. Other suitable fining agents include without limitation arsenic, antimony, iron and cerium. Fining vessel 36 may be heated to a temperature greater than the melting vessel 14 temperature, thereby further heating the fining agent. Oxygen bubbles produced by the temperature-induced chemical reduction of the fining agent(s) rise through the molten glass within the fining vessel, wherein gases in the molten glass produced in the melting furnace can coalesce into the oxygen bubbles produced by the fining agent. The enlarged gas bubbles can then rise to a free surface of the molten glass in the fining vessel and thereafter be vented out through a suitable vent pipe.

[0058] The downstream glass manufacturing apparatus 32 can further include a second conditioning vessel such as a mixing vessel 38 that can be located downstream from the fining vessel 36. Mixing vessel 38 can be used to provide a homogenous glass melt composition, thereby reducing or eliminating cords of inhomogeneity that may otherwise exist within the molten glass. As shown, fining vessel 36 may be coupled to molten glass mixing vessel 38 by way of a second connecting conduit 40. In some examples, molten glass 30 may be gravity fed from the fining vessel 36 to mixing vessel 38 by way of second connecting conduit 40. For instance, gravity may cause molten glass 30 to pass through an interior pathway of second connecting conduit 40 from fining vessel 36 to mixing vessel 38. In some examples,

downstream glass manufacturing apparatus 32 can comprise multiple mixing vessels. For example, in some embodiments a mixing vessel may be included upstream from fining vessel 36 and a second mixing vessel positioned downstream from fining vessel 36. In some embodiments mixing may be performed by mixing devices, such as static mixing vanes. Static mixing vanes may be positioned within conduits of the downstream glass manufacturing apparatus or within other vessels of the downstream glass manufacturing apparatus.

[0059] Downstream glass manufacturing apparatus 32 can further include another conditioning vessel such as delivery vessel 42 that may be located downstream from mixing vessel 38.

Delivery vessel 42 may condition molten glass 30 to be fed into a downstream forming device. For instance, delivery vessel 42 can act as an accumulator and/or flow controller to adjust and provide a consistent flow of molten glass 30 to forming body 44 by way of delivery conduit 46. As shown, mixing vessel 38 may be coupled to delivery vessel 42 by way of third connecting conduit 48. In some examples, molten glass 30 may be gravity fed from mixing vessel 38 to delivery vessel 42 by way of third connecting conduit 48. For instance, gravity may act to drive molten glass 30 to pass through an interior pathway of third connecting conduit 48 from mixing vessel 38 to delivery vessel 42.

[0060] Downstream glass manufacturing apparatus 32 can further include forming apparatus 50 comprising the above-referenced forming body 44 including inlet conduit 52. Delivery conduit 46 can be positioned to deliver molten glass 30 from delivery vessel 42 to inlet conduit 52 of forming apparatus 50. In a fusion forming process forming body 44 can comprise a trough 54 formed in an upper surface of the forming body and converging forming surfaces 56 that converge along a bottom edge (root) 58 of the forming body. Molten glass delivered to the forming body trough via delivery vessel 42, delivery conduit 46 and inlet conduit 52 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 the root to produce a single ribbon of glass 60 that is drawn from root 58 by applying tension to the glass ribbon, such as by gravity and pulling rolls (not shown), to control the dimensions of the glass ribbon as the glass cools and viscosity increases such that the glass ribbon 60 goes through a visco-elastic transition and has mechanical properties that give the glass ribbon 60 stable dimensional characteristics. The glass ribbon may subsequently be separated into individual glass sheets by a glass separation apparatus (not shown)

[0061] Unlike other components of the downstream glass manufacturing apparatus, forming body 44 is typically formed from a refractory ceramic material such as alumina (aluminum oxide) or zirconia (zirconium oxide), although other refractory materials may be used. In some examples forming body 44 is a monolithic block of ceramic material that has been isostatically pressed and sintered, then machined into the appropriate shape. In other examples the forming body may be formed by joining two or more blocks of refractory material, e.g. refractory ceramic material. Forming body 44 may include one or more precious metal components configured to direct the flow of molten glass over and from the forming body.

[0062] Shown in FIG. 2 is a simplified schematic drawing of an example bubbler 16 according to embodiments described herein, bubbler 16 comprising a capillary member 100, sleeve 102 and nozzle 104. Capillary member 100, sleeve 102 and nozzle 104 may together define a central longitudinal flow axis 105, which may define a common central axis of the apparatus and selected components. Bubbler 16 may further comprise a cooling apparatus 106, a screw member 108, a positioning assembly 110 and a support assembly 111 configured to support bubbler 16 and secure the bubbler to a suitable structure, for example steel girding or other building structure. Other components of the example bubbler are presented in more detail in the following description.

[0063] FIGS. 3 and 4 are i) a cross sectional perspective view of an end portion of bubbler 16 and ii) a longitudinal cross sectional view of nozzle 104, respectively, illustrating capillary member 100, sleeve 102 and nozzle 104. In particular, the sleeve and/or nozzle depicted in FIGS. 3 and 4 are configured to be inserted into molten glass 30. Capillary member 100 may be formed, for example, from any refractory ceramic suitable for use in high temperature corrosive environments. In some examples, capillary member 100 may be formed of aluminum oxide (e.g. aloxide, aloxite or alundum) or stabilized zirconia (e.g. example yttria, calcium or magnesium- stabilized zirconia). Capillary member 100 may, for example, be selected to be compatible with the glass composition in manufacture, such that any dissolution or corrosion of the capillary member that might occur does not noticeably impact the overall glass composition. Capillary member 100 further comprises a plurality of capillary passages 112 extending from one end of capillary memberlOO (i.e., first end 114) to the opposite end of the capillary member (second end 176, see FIG. 8B), capillary passages 112 being generally parallel with central axis 105. Each capillary passage 112 is configured to restrict an ingress of molten glass into the capillary passage should molten glass reach the capillary member, and each capillary passage may have a diameter in a range from about 0.02 mm to about 0.635 mm. As used herein, the term

"diameter" refers to the maximum dimension in an axis of the passage perpendicular to central axis 105 and is not strictly limited to a circular cross sectional shaped passage. For example, capillary passages 112 may be circular, rectangular or comprise another geometric shape. Each capillary passage 112 comprises an orifice 115 at first end 114, each capillary orifice 115 comprises an area calculated from the dimensions of the capillary orifice. For example, if the capillary orifice is a circular orifice, the area of the capillary orifice is the area of a circle, πχ², where r is the radius of the circle.

[0064] Capillary member 100 is slidably positioned within sleeve 102 such that capillary member 100 can be translated within sleeve 102 along central axis 105 as necessary. Sleeve 102 may be formed from any metal capable of withstanding the high temperatures and corrosive environment associated with glass melting or molten glass conditioning. For example, suitable metals include the platinum group metals osmium, palladium, ruthenium, iridium, rhodium, platinum or alloys thereof. In examples, sleeve 102 may be formed from a platinum-rhodium alloy containing platinum in a range from about 70% to about 90% and rhodium in a range from about 10% to about 30%.

[0065] Like sleeve 102, nozzle 104 may be formed from any metal capable of withstanding the high temperatures and corrosive environment associated with glass melting or molten glass conditioning. For example, suitable metals include the platinum group metals osmium, palladium, ruthenium, iridium, rhodium, platinum or alloys thereof. In examples, nozzle 104 may be formed from a platinum-rhodium alloy containing platinum in a range from about 70% to about 90%) and rhodium in a range from about 10% to about 30%. [0066] Nozzle 104 includes a passage 116 extending from a first orifice 120, defined by a first end 122, to a second orifice 124 defined by a second end 126. In some embodiments a diameter of second orifice 124 is larger than a diameter of first orifice 120. An area of first orifice 120 in a plane perpendicular to central axis 105 may be substantially equal to the cumulative area of the total number of capillary passage orifices 115 to prevent a flow restriction of gas exiting the bubbler through first orifice 120. That is, for a given volume of gas exiting capillary member 100, the size of first orifice 120 may be selected to present a similar or the same flow condition to the gas as the capillary member. As used herein an orifice area is the total area of the orifice in a plane perpendicular to central axis 105. For example, if the capillary orifices have a uniform circular cross section, and the total number of capillary passages 112 is 20, the cumulative area of the orifices is 20πχ² (assuming each passage has an identical radius), and therefore the area of first orifice 120 is selected to be substantially equal to 20πχ². By substantially what is meant is that the area of first orifice 120 is within 10% of the cumulative area of the capillary passages, for example within 5% or within 1%.

[0067] Nozzle 104 may further include a tapered outer surface 128 that tapers in a direction toward first orifice 120 to limit bubble size during bubble generation. As best seen in FIG. 4, nozzle 104 may comprise a tapered cross sectional outer surface profile in a plane parallel with central longitudinal axis 105 of the nozzle. For example, outer surface 128 may include a conical profile. In other examples, such as the example of FIG. 4, the outer surface profile may comprise an arcuate outer surface profile, for example in the shape of an ogee. Described differently, a radius Rl between central axis 105 and outer surface 128 may decrease over at least a portion of the nozzle in a direction from second end 126 to first end 122. Passage 116 may comprise a first passage 130 and a second passage 132 in fluid communication with first passage 130, wherein first passage 130 may further terminate at first orifice 120 and second passage 132 may terminate at second orifice 124. In example embodiments, second passage 132 may include a diameter larger than a diameter of first passage 130. In some embodiments, first passage 130 may have a substantially constant cross sectional size (e.g. diameter). In some embodiments, passage 116 may include a taper, for example within second passage 132 in a direction from second orifice 124 to first passage 130 to match the size of second orifice 124 to the size of first passage 130. For example, second passage 132 may comprise a conical profile. First passage 130 may be cylindrical. [0068] At least a portion of an outside surface of nozzle 104 is recessed by an amount δ such that an outside diameter of recessed surface 134 can be positioned within an inside diameter of a first end 136 of sleeve 102. For example, a lower portion of nozzle 104 may be recessed. Shoulder 138 of nozzle 104 may thereafter be welded to first end 136 of sleeve 102 along seam 140 where shoulder 138 meets first end 136. In example embodiments, sleeve 102 may further comprise plug welds 142 about a perimeter of the sleeve, for example at 180 degree or 90 degree intervals, wherein sleeve 102 is drilled through to recessed surface 134, and additional welds made by filling the drilled out hole with a welding metal. For example, the plug welds can be made using a metal compatible with the sleeve and nozzle materials. In examples, plug welds 142 may be formed from a platinum-rhodium alloy containing platinum in a range from about 70% to about 90% and rhodium in a range from about 10% to about 30%.

[0069] As described supra, capillary member 100 is slidably positioned within an interior, longitudinally extending passage of sleeve 102, and may be arranged such that first end 114 of capillary member 100 abuts second end 126 of nozzle 104. Second passage 132 is sized such that each passage of the plurality of capillary passages 112 opens into second passage 132.

Accordingly, second passage 132 may form an intermediate chamber for receiving a flow of gas from capillary member 100 prior to the flow of gas entering first passage 130 and thereafter exiting nozzle 104 through first orifice 120.

[0070] As shown in FIGS. 2, 5A, B and 6 - 7, bubbler 16 may further comprise a cooling apparatus 106. Cooling apparatus 106 may be a fluid cooling apparatus wherein a cooling fluid, for example water, is flowed through passages within the cooling apparatus. Cooling apparatus 106 may comprise an inlet 144 and an outlet 146 through which a cooling fluid is supplied and retrieved, respectively, to and from cooling apparatus 106, as illustrated by arrows 148. Cooling apparatus 106 may include lugs 150 positioned on and extending from an outside wall of the cooling apparatus to control the insertion depth of the bubbler into the vessel. Cooling apparatus 106 may further comprise an inner wall 152 defining a central passage through which sleeve 102 and capillary member 100 extend. Cooling apparatus 106 is shown in perspective view in FIG. 6 without sleeve 102 and nozzle 104, and in FIG. 7 a perspective view of an upper portion of cooling apparatus 106 is shown with sleeve 102 and nozzle 104 in place. Sleeve 102 may be secured to cooling apparatus 106 at an upper end of cooling apparatus 106, for example by weld 154 between sleeve 102 and cooling apparatus 106, such that a portion of sleeve 102 extends from a top of cooling apparatus 106.

[0071] Cooling apparatus 106 may be formed from a high temperature steel, such as a suitable stainless steel, and an upper portion 156 of cooling apparatus 106, generally above lugs 150, may be coated with a refractory coating 158, for example a plasma-sprayed zirconia coating, to protect that portion of the cooling apparatus closest to the vessel (e.g. melting vessel 14) from oxidation. In addition, that portion of sleeve 102 positioned within cooling apparatus 106, and extending through the central passage thereof, such as the length 157 shown in FIG. 5 A, may also be coated with a ceramic coating 159 (see FIG. 5B), such as plasma-sprayed zirconia, to prevent diffusion welding of the sleeve to inner wall 152 should the inner wall and the sleeve come into contact for a sufficiently prolonged period of time.

[0072] It should be readily apparent from the foregoing figures that at least a portion of sleeve 102 extends above cooling apparatus 106, and is not directly cooled by the cooling apparatus. That is, that portion of bubbler 16 that extends into the molten glass, and in particular an upper portion of sleeve 102, is not surrounded by the cooling apparatus. Thus, nozzle 104, a (upper) portion of sleeve 102, and a portion of capillary member 100 are not cooled by cooling apparatus 106.

[0073] Referring now to FIGS. 8 A, 8B and FIG. 9, where FIG. 8B is a continuation of FIG. 8 A in a downward direction, sleeve 102 may comprise a flange 160 extending from a second (bottom) end 162 of sleeve 102. Fitting 164 can be used to secure sleeve 102 via flange 160 within a passage 166 of screw member 108, wherein flange 160 is forced against one or more sealing gaskets 172 positioned within and extending into passage 166. Passage 166 extends entirely through screw member 108, i.e. from first end 174 to second end 176 (see FIG. 8B). For example, fitting 164 may be a threaded fitting that is screwed into first end 174 of passage 166. Accordingly, passage 166 may include threads within a first portion of passage 166 that mate with threaded fitting 164. Compression of the one or more sealing gaskets 172 by fitting 164 forces the one or more sealing gaskets 172 against capillary member 100 and a sealing lip 173, thereby sealing screw member 108 against a flow of gas between the screw member and the capillary member. After assembly, inner wall 152 of cooling apparatus 106 may be secured to fitting 164 by weld 178. Thus, screw member 108 can be securely coupled to cooling apparatus 106. [0074] As best shown by FIG. 8B depicting a bottom end of screw member 108, second end 179 of capillary member 100 is coupled to first end 180 of gas supply tube 182 via coupler 184. Coupler 184 may be a gas-tight coupler. Gas supply tube 182 may be, for example, a stainless steel pipe comprising a central passage 186. Coupler 184 includes a passage 188 that enables gas flow between gas supply tube 182 and capillary member 100. A shown in FIGS. 8B and 10A, bearing block 190 is engaged with screw member 108 via threads 192 and matching threads within a passage of bearing block 190 through which screw member 108 extends. Bearing block 190 forms a portion of positioning assembly 110. To prevent binding and galling, and to promote smooth thread engagement, bearing block 190 may be formed from a corrosion resistant metal that is softer than screw member 108. For example, bearing block 190 may be formed from silicon bronze, and threads 192 may be trapezoidal threads, such as Acme threads.

[0075] FIG. 10B is a perspective view of positioning assembly 110 and is a continuation of FIG. 1 OA in a downward direction, wherein bearing block 190 is engaged with and rotatable about screw member 108. In addition, positioning assembly 110 may include casing 196 coupled to bearing block 190. FIG. 10B illustrates the end (bottom) of casing 196. Casing 196 includes a bearing assembly 198 coupled to casing 196, and a collar 200 coupled to bearing assembly 198. Gas supply pipe 182 extends through bearing assembly 198 and collar 200, and collar 200 may be coupled to gas supply pipe 182 with a suitable fastener, such as screw 202. Thus, gas supply pipe 182 is rotatably coupled to positioning assembly 110. Gas supply pipe 182 is further coupled to gas line 204 via suitable couplers and fittings, wherein gas line 204 is in fluid communication with gas source 206.

[0076] From the foregoing description and the accompanying drawings it is readily observable that gas line 204 is in direct fluid communication with nozzle 104 via gas supply pipe 182, coupler 184, and capillary member 100. It should also be apparent that with cooling apparatus 106 engaged with glass melting furnace 12, and gas supply pipe 182 rotatably coupled to casing 196 via bearing assembly 198 and collar 200 (and thus with positioning assembly 110 rotatable about gas supply pipe 182), rotation of positioning assembly 110, including bearing block 190 and casing 196, about screw member 108 will cause positioning assembly 110 to translate on screw member 108. As positioning assembly 110 translates on screw member 108, capillary member 100 also moves within sleeve 102, rising or lowering depending on the direction of rotation of the positioning assembly. [0077] Positioning assembly 110 may be rotated manually, such as by hand, or positioning assembly 110 may be engaged with a drive device (not shown) to rotate the positioning assembly. For example, the drive device may comprise a worm drive, wherein one of bearing block 190 or another portion of positioning assembly 110 is fitted with a worm gear and the worm gear is engaged with a worm screw coupled to a motor. The drive device may be activated manually, or a control system (not shown) may be employed to activate the drive device at a predetermined time.

[0078] Operationally, gas is delivered to bubbler 16 under pressure from gas source 206 and a gas pressure within nozzle passage 116 is maintained slightly greater than the pressure exerted by the molten glass above the bubbler. The required pressure will depend on such variables as the density of molten glass 30 and the depth of the molten glass above the bubbler first (output) orifice 120. Gas pressure may be controlled, for example, by valve 208, for example a needle valve, and flow meter 210 (see FIG. 1) at a pressure suitable to release from 0 to 100 bubbles per minute from bubbler 16 into molten glass 30. Advantageously, bubbler 16 is capable of surviving significant periods of time wherein the gas pressure may be decreased below a suitable pressure required for bubbling, either by intentional deactivation of the bubbler (e.g. turning off the gas supply), or unintentionally, such as a line failure. For example, in an idle condition with no bubbling desired, a pressure within first passage 116 can be maintained at a pressure equal to the pressure exerted by the depth of molten glass above bubbler 16. Under such an equilibrium condition, the bubble rate would be zero bubbles per minute. Molten glass will not ingress through passage 116 and will not contact capillary member 100. On the other hand, in the instance where the gas supply to bubbler 16 is decreased below a pressure necessary to prevent the ingress of molten glass into passage 116, and wherein passage 116 can fill with molten glass that may contact capillary member 100. However, because the upper portion of bubbler 16, e.g. nozzle 104, is not cooled, the molten glass within the nozzle (i.e. passage 116) remains fluid. If gas pressure within the system, and in particular within capillary member 100, is restored to a level greater than the pressure exerted by the molten glass above the bubbler, the molten glass will be forced from passage 116 (or capillary passages 112) and bubbling may either recommence, or the bubbler placed back into an idle condition with nozzle 104 pressurized but with a bubble rate of essentially zero. If molten glass has been in contact with capillary member 100 for a time sufficient to result in a degradation of capillary member 100, capillary member may be raised within sleeve 102 via positioning assembly 110. Thus, bubbler 16 provides an ability to terminate bubbling intentionally or unintentionally for indefinite periods of time, and then to restart bubbling when desired without the need to remove and rebuild the bubbler.

[0079] Conventional bubblers that rely on cooling to protect the bubbler components exposed to the molten glass can suffer from the inability to clear passages filled with the glass. Should molten glass enter passages of the bubbler, the glass can be cooled to a low viscosity, impeding the ability to force the glass from the passages. Turning off the cooling to allow the glass to decrease in viscosity risks damage to the bubbler structure intended to be protected by the cooling. Accordingly, typical practice is to replace the bubbler.

[0080] Shown in FIG. 1 1 is another example of a glass manufacturing apparatus 10 wherein the glass making apparatus includes a downstream glass manufacturing apparatus 32 and may further include a molten glass conditioning vessel 212 positioned between melting vessel 14 and fining vessel 36 and in fluid communication with melting vessel 14 via conduit 214, wherein the molten glass conditioning vessel includes one or more bubblers 16 in accordance with embodiments of the present disclosure. Conditioning vessel 212 may constitute, for example, a cooling vessel wherein the molten glass from melting vessel 14 cools to a temperature less than the melting temperature, allowing one or more fining agents within the molten glass to change their redox state. Thus, the fining agent may "recharge" with oxygen provided by the one or more bubblers 16 prior to entering fining vessel 36. Conditioning vessel 212 may be a supplemental melting vessel, such as a melting vessel with multiple temperature zones.

Alternatively, or optionally, fining vessel 36 may comprise one or more bubblers 16.

[0081] FIG. 12 shows a schematic view of a portion of another glass making apparatus 300 comprising melting vessel 302 including a melting section 304 and a fining section 306 separated by a wall 308 having one or more passages therethrough. Bubblers 16 may be included in the melting section 304. Alternatively, or optionally, fining section 306 may include one or more bubblers 16.

[0082] 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 invention. Thus, it is intended that the present disclosure cover the modifications and variations of such embodiments provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. An apparatus for conditioning molten glass comprising:

a vessel comprising an interior volume,

a bubbler extending into the volume comprising:

a sleeve including an interior passage extending therethrough;

a nozzle secured to a first end of the sleeve, the nozzle including an interior passage extending between an inlet orifice and an outlet orifice; and

a capillary member comprising a plurality of capillary passages extending therethrough, the capillary member slidably engaged within the interior passage of the sleeve.

2. The apparatus according to claim 1, further comprising a cooling apparatus.

3. The apparatus according to claim 2, further comprising a screw member coupled to the cooling apparatus.

4. The apparatus according to claim 1, further comprising a screw member coupled to the sleeve.

5. The apparatus according to claim 4, further comprising a positioning assembly rotatably coupled to the screw member.

6. The apparatus according to claim 5, wherein the capillary member is coupled to a gas supply pipe.

7. The apparatus according to claim 6, wherein the gas supply pipe is rotatably coupled to the positioning assembly.

8. The apparatus according to claim 1, wherein the nozzle comprises an outer profile tapering in a direction toward the outlet orifice.

9. The apparatus according to claim 3, wherein the interior passage of the nozzle comprises an intermediate chamber with a diameter larger than a diameter of the outlet orifice.

10. The apparatus according to claim 1, wherein the nozzle is secured to the sleeve by a perimeter weld around a seam between the nozzle and the sleeve.

11. The apparatus according to claim 10, wherein the nozzle is secured to the sleeve by a plurality of plug welds.

12. The apparatus according to claim 1, wherein at least a portion of the sleeve comprises a ceramic coating.

13. The apparatus according to claim 2, wherein at least a portion of the cooling apparatus comprises a ceramic coating.

14. The apparatus according to claim 3, wherein a sealing gasket is positioned between the capillary member and the screw member.

15. The apparatus according to claim 1, wherein the nozzle comprises a recessed portion positioned within the interior passage of the sleeve.

16. The apparatus according to claim 1, wherein the vessel is a melting vessel, a fining vessel or a cooling vessel.

17. The apparatus according to claim 1, wherein the sleeve and the nozzle comprise platinum.

18. The apparatus according to claim 1, wherein the outlet orifice of the nozzle comprises an orifice area and each capillary passage of the plurality of capillary passages comprises an output orifice with an orifice area, and wherein a sum of the orifice areas of the plurality of capillary passages is substantially equal to the orifice area of the output orifice of the nozzle.

19. An apparatus for conditioning molten glass comprising:

a vessel comprising an interior volume,

a bubbler extending into the volume comprising:

a sleeve including an interior passage extending therethrough;

a nozzle secured to a first end of the sleeve;

a capillary member comprising a plurality of passages extending therethrough, the capillary member slidably engaged within the interior passage of the sleeve;

a screw member coupled to the sleeve; and

a positioning assembly rotatably engaged with the screw member and configured such that rotation of the positioning assembly about the screw member translates the capillary member within the sleeve.

20. The apparatus according to claim 19, further comprising a cooling apparatus coupled to the screw member.

21. The apparatus according to claim 20, further comprising a gas supply pipe coupled to the positioning assembly and further coupled to the capillary member.

22. The apparatus according to claim 19, wherein the vessel is a melting vessel, a fining vessel or a cooling vessel.

23. The apparatus according to claim 19, wherein the sleeve and the nozzle comprise platinum.

24. A method of conditioning a molten glass comprising:

flowing molten glass into or out of a vessel, the vessel including a bubbler extending into the molten glass and comprising an outlet orifice, the bubbler comprising a sleeve, a nozzle and a capillary member slidably positioned in the sleeve; and

pressurizing the nozzle with a gas supplied through the capillary member, a pressure of the gas sufficient to prevent the molten glass from entering the nozzle and contacting the capillary member.

25. The method according to claim 24, wherein a rate of bubble release from the nozzle is zero bubbles per minute over a period of at least one hour.

26. The method according to claim 24, wherein a rate of bubble release from the nozzle is in a range from 1 to 100 bubbles per minute.

27. The method according to claim 24, wherein a temperature of the molten glass is in a range from about 1550 °C to about 1690 °C.

28. The method according to claim 24, wherein after pressurizing the nozzle, de-pressurizing the nozzle such that molten glass enters the nozzle, then re-pressurizing the nozzle, thereby forcing the molten glass from the nozzle.