WO2018232159A2

WO2018232159A2 - Apparatus and method for cooling a glass ribbon

Info

Publication number: WO2018232159A2
Application number: PCT/US2018/037605
Authority: WO
Inventors: Tomohiro ABURADA; Anmol AGRAWAL; Steven Roy Burdette; Robert Delia; Ibraheem Rasool MUHAMMAD; Jae Hyun Yu
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2017-06-14
Filing date: 2018-06-14
Publication date: 2018-12-20
Anticipated expiration: 2019-12-14
Also published as: WO2018232159A3; TW201904891A

Abstract

An apparatus for cooling a glass ribbon drawn along a draw plane through the chambers of a housing assembly, the housing assembly including a compartment separated from the chambers of the housing assembly by a thermal plate, and at least one cooling tube extending along and parallel with the thermal plate, the at least one cooling tube configured to flow a cooling fluid against a surface of the thermal plate opposite the draw plane.

Description

APPARTUS AND METHOD FOR COOLING A GLASS RIBBON

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Application Serial No. 62/519,501 filed on June 14, 2017 the contents of which are relied upon and incorporated herein by reference in their entirety as if fully set forth below.

BACKGROUND

FIELD

[0002] The present disclosure relates generally to methods for forming a glass article, and in particular for cooling a glass ribbon as the glass ribbon is drawn from a forming body.

Technical Background

[0003] The manufacture of glass substrates, for example glass substrates used in the manufacture of lighting panels, liquid crystal displays and other electronic devices, typically involves drawing a glass ribbon from molten glass. The glass ribbon must be cooled both along a length of the ribbon and across a width of the ribbon to obtain desired attributes and at the same time minimize residual stress in the glass ribbon. The glass ribbon may then be cut into individual glass sheets, or panes, which can be used in a variety of products, including the aforementioned displays.

SUMMARY

[0004] In one embodiment, an apparatus for cooling a glass ribbon is disclosed, comprising a forming body configured to form a glass ribbon along a draw plane and a housing assembly positioned below the forming body and through which the glass ribbon is drawn in a draw direction. The apparatus further comprises at least one cooling tube, for example a linear cooling tube, positioned in the housing assembly, the at least one cooling tube comprising a longitudinal axis extending parallel with the draw plane and orthogonal to the draw direction, and at least one orifice configured to direct a flow of cooling gas from the cooling tube. The apparatus still further comprises a thermal plate positioned between the at least one cooling tube and the draw plane, the at least one cooling tube oriented to direct the flow of cooling gas against the thermal plate. l [0005] In embodiments, the housing assembly comprises an upper housing portion and a lower housing portion.

[0006] The thermal plate may, for example, be positioned in the upper housing portion.

[0007] In some embodiments, the at least one cooling tube comprises at least one orifice configured to direct a flow of cooling gas from the cooling tube.

[0008] In some embodiments, the at least one cooling tube can comprise a plurality of cooling tubes, for example at least one closed, or radiative type cooling tube, and at least one open, or injection type cooling tube configured to direct a flow of cooling fluid against the thermal plate.

[0009] In some embodiments, the at least one orifice can comprise a plurality of orifices.

[0010] In some embodiments, the at least one cooling tube comprises a first tube and a second tube positioned interior to and spaced apart from the first tube, a gap between the first tube and the second tube forming a first passage configured to receive a flow of cooling fluid. The second tube comprises an outer wall and an inner wall, a gap between the outer wall and the inner wall forming a second passage isolated from the first passage, the inner wall defining a third passage in fluid communication with the first passage;

[0011] In embodiments, a blocking member may be positioned between and in contact with the first tube and the second tube, the blocking member extending along at least about 50% of a length of the second tube. The at least one orifice extends between the second passage and an exterior of the first tube such that the second passage is in fluid communication with an exterior atmosphere.

[0012] In some embodiments, the at least one orifice comprises a slot extending along at least 50% of a length of the blocking member.

[0013] In some embodiments, the at least one cooling tube comprises a first tube and a second tube positioned interior to and spaced apart from the first tube to form a gap therebetween. The cooling tube may further comprise a pair of blocking members positioned in the gap between and in contact with the first tube and the second tube, the blocking members dividing the gap into a first passage and a second passage in fluid communication with the first passage. The second tube defines a third passage interior to and extending along a length of the second tube and isolated from the first and second passages, the at least one orifice extending between the third passage and an exterior of the first tube. The at least one orifice may, for example, comprise a slot extending along at least 50% of a length of the blocking member. [0014] The upper housing portion may comprise a compartment positioned behind the thermal plate relative to the draw plane, wherein the at least one cooling tube is positioned within the compartment. The compartment may be isolated from an interior atmosphere of the upper housing portion. The apparatus may further comprise an exhaust tube providing fluid communication between the compartment and an atmosphere outside the upper housing portion.

[0015] In some embodiments, the lower housing portion comprises a chamber through which the glass ribbon is drawn, the lower housing portion further comprising at least one cooling tube positioned within the lower housing portion chamber extending in a direction parallel with the draw plane and orthogonal to the draw direction, and in direct view of the glass ribbon.

[0016] The at least one cooling tube positioned within the lower housing portion chamber can comprise at least one orifice configured to direct a flow of cooling gas onto the glass ribbon.

[0017] In some embodiments, the at least one cooling tube positioned within the lower housing portion chamber comprises a first tube and a second tube positioned interior to and spaced apart from the first tube, a first gap between the first tube and the second tube forming a first passage configured to receive a flow of cooling fluid, the second tube comprising an outer wall and an inner wall, a second gap between the outer wall and the inner wall forming a second passage isolated from the first passage, the inner wall defining a third passage in fluid communication with the first passage. The at least one cooling tube positioned within the lower housing portion chamber may further comprise a blocking member positioned between and in contact with the first tube and the second tube, the blocking member extending along at least about 50% of a length of the second tube. The at least one cooling tube positioned within the lower housing portion chamber comprises at least one orifice extending between the second passage and an exterior of the first tube.

[0018] In some embodiments, the at least one orifice of the at least one cooling tube positioned in the lower housing portion chamber comprises a slot extending along at least 50% of a length of the blocking member.

[0019] In some embodiments, the at least one cooling tube positioned in the lower housing portion chamber comprises a first tube and a second tube positioned interior to and spaced apart from the first tube to form a gap therebetween. The at least one cooling tube positioned within the lower housing portion chamber may further comprise a pair of blocking members positioned in the gap between and in contact with the first tube and the second tube, the blocking members dividing the gap into a first passage and a second passage in fluid communication with the first passage. The second tube defines a third passage interior to and extending along a length of the second tube and isolated from the first and second passages, the at least one cooling tube positioned within the lower housing portion chamber further comprising at least one orifice extending between the third passage and an exterior of the first tube.

[0020] The at least one orifice of the at least one cooling tube positioned in the lower housing portion chamber may in some embodiments comprise a slot extending along at least 50% of a length of the blocking member.

[0021] The apparatus may further comprise cooling doors positioned above the housing assembly, the cooling doors comprising a plurality of cooling tubes positioned therein, each cooling tube of the plurality of cooling tubes comprising a longitudinal axis extending orthogonal to the draw plane and orthogonal to the draw direction.

[0022] In another embodiment, a method of cooling a glass ribbon is described, comprising drawing a glass ribbon from a forming body along a draw plane in a draw direction, the glass ribbon passing through a housing assembly positioned below the forming body. The method further includes at least one cooling tube positioned in the housing assembly, the at least one cooling tube comprising a longitudinal axis parallel to the draw plane and orthogonal to the draw direction, the at least one cooling tube comprising a proximal end and a distal end and at least one orifice intermediate between the proximal end and the distal end. A thermal plate extends parallel to the draw plane and orthogonal to the draw direction and is positioned between the at least one cooling tube and the draw plane. The method further comprises cooling the glass ribbon by exhausting a cooling gas from the at least one orifice onto the thermal plate as the glass ribbon traverses through the housing assembly.

[0023] In some embodiments, the housing assembly comprises an upper housing portion and a lower housing portion, the thermal plate positioned in the upper housing portion.

[0024] The method may further comprise cooling the cooling gas with a cooling fluid flowing in the cooling tube. For example, the cooling fluid may be flowed through a first passage in the cooling tube, and the cooling gas is flowed through a second passage in the cooling tube interior to the first passage.

[0025] In some embodiments, the upper housing portion defines a compartment, wherein the at least one cooling tube is positioned within the compartment. [0026] The method may further comprise extracting the cooling gas from the compartment through an exhaust tube extending from the compartment to outside the upper housing portion.

[0027] In some embodiments, the lower housing portion defines a chamber through which the glass ribbon is drawn, the lower housing portion comprising at least one cooling tube extending into the chamber with a direct view to the glass ribbon, the at least one lower housing portion cooling tube comprising at least one orifice and a longitudinal axis parallel to the draw plane and orthogonal to the draw direction, the method further comprising cooling the glass ribbon by exhausting cooling gas from the at least one orifice of the lower housing portion cooling tube onto the glass ribbon as the glass ribbon traverses the chamber.

[0028] Additional features and advantages of the embodiments disclosed herein will be set forth in the detailed description that follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0029] It is to be understood that both the foregoing general description and the following detailed description present embodiments intended to provide an overview or framework for understanding the nature and character of the embodiments disclosed herein. The accompanying drawings are included to provide further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure, and together with the description serve to explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a schematic view of an exemplary glass making apparatus according to embodiments of the present disclosure;

[0031] FIG. 2 is a cross sectional side view of an exemplary forming apparatus according to FIG. 1 ;

[0032] FIG. 3 is a close up cross sectional side view of a portion of the forming apparatus of FIG. 2;

[0033] FIG. 4A is a longitudinal cross sectional view of an exemplary non-injection type cooling tube;

[0034] FIG. 4B is an axial cross sectional view of the cooling tube of FIG. 4A; [0035] FIG. 5 A is a longitudinal cross sectional view of an exemplary injection-type cooling tube;

[0036] FIG. 5B is a longitudinal cross sectional view of another embodiment of the exemplary injection-type cooling tube of FIG. 5 A

[0037] FIG. 5C is an axial cross sectional view of the exemplary injection-type cooling tubes of FIGS. 5A and 5B;

[0038] FIG. 6A is a longitudinal cross sectional view of another exemplary injection-type cooling tube;

[0039] FIG. 6B is a longitudinal cross sectional view of another embodiment of the exemplary injection-type cooling tube of FIG. 6 A;

[0040] FIG. 6C is a axial cross sectional view of the exemplary injection-type cooling tubes of FIGS. 6A and 6B;

[0041] FIG. 7A is a longitudinal cross sectional view of another exemplary injection-type cooling tube;

[0042] FIG. 7B is an axial cross sectional view of the exemplary injection-type cooling tube of FIG. 7 A;

[0043] FIG. 7C is an axial cross sectional view of the exemplary injection-type cooling tubes of FIGS. 7A and 7B;

[0044] FIG. 8 A is a longitudinal cross sectional view of still another exemplary injection- type cooling tube;

[0045] FIG. 8B is a longitudinal cross sectional view of another embodiment of the exemplary injection-type cooling tube of FIG. 8 A;

[0046] FIG. 8C is an axial cross sectional view of the exemplary injection-type cooling tubes of FIGS. 8A and 8B;

[0047] FIG. 9A is a longitudinal cross sectional view of yet another exemplary injection-type cooling tube;

[0048] FIG. 9B is a longitudinal cross sectional view of another embodiment of the exemplary injection-type cooling tube of FIG. 9 A;

[0049] FIG. 9C is an axial cross sectional view of the exemplary injection-type cooling tubes of FIGS. 9A and 9B; and

[0050] FIG. 10 is a plot of centerline ribbon temperature as a function of distance below the bottom edge (root) of the forming body, comparing various cooling tube arrangements;

[0051] FIG. 11 is a plot comparing temperature rise for a cooling tube configured to exhaust a cooling fluid from an opening in the tube for a tube where the exhausted cooling fluid is adjacent an outer wall of the cooling tube, and a cooling tube where the exhausted cooling fluid is conveyed with a cooling jacket surrounding the cooling fluid.

DETAILED DESCRIPTION

[0052] Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0053] 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.

[0054] 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.

[0055] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus, specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0056] As used herein, the singular forms "a," "an" and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to "a" component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0057] As used herein, "molten glass" shall be construed to mean a molten material which, upon cooling, can enter a glassy state. The term molten glass is used synonymously with the term "melt". The molten glass may form, for example, a majority silicate glass, although the present disclosure is not so limited.

[0058] As used herein, the term "fluid" shall denote any gas, mixture of gasses, liquid, gas and liquid mixtures, vapor, or combinations thereof.

[0059] As used herein, the term "refractory", or "refractory material" is used to denote non- metallic materials having chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above 538°C, for example equal to or greater than about 700°C, such as equal to or greater than about 800°C.

[0060] The manufacture of glass sheets by a down draw process, for example a fusion down draw process, requires careful control of process temperature. The impact of temperature is most acute during the forming process, wherein a thin glass ribbon, in many cases less than a millimeter (mm) or less in thickness and in some instances in excess of 3 meters wide, is drawn from a forming body through free space supported principally by its edges. It should be readily apparent that even small temperature variations can result in residual stress that can warp the glass ribbon, and the glass sheet cut therefrom. It is also important to note that the ribbon typically leaves the forming body at a temperature in excess of 1000°C, but must be cooled to a temperature less than only several hundred degrees in a very short distance, since the ribbon is typically drawn in a vertical downward direction and as a practical matter available vertical distance is often limited. The cooling of a glass ribbon drawn from a forming body in a down draw process is further complicated by the need to minimize air currents within the draw area, including convection currents directly attributable to the cooling means, as air currents across the ribbon can cause thickness variations in the surface of the ribbon.

[0061] To maintain a consistent environment around the glass ribbon, both the forming body and the free space region through which the glass ribbon is drawn as it transitions from a viscous liquid to an elastic solid is contained within structures that separate the glass ribbon from the surrounding environment. More particularly, the free space volume through which the glass ribbon is drawn is surrounded on four sides by a housing positioned below the forming body: a collection of connected walls and refractory insulation that form a shroud or tunnel.

[0062] As noted above, it is particularly beneficial during the draw process to maintain a well-controlled temperature regime within the housing as the viscous ribbon transitions to an elastic solid. Moreover, it is desirable to cool the ribbon as quickly as possible after the molten glass leaves the forming body to maximize the vertical space available to anneal the glass ribbon. Accordingly, heat extraction requirements within the upper-most region of the housing can be severe: Not only must a significant amount of residual heat be removed from the ribbon, but since the ribbon is passing through a zone with low viscosity high in the housing (s to the forming body), care must be taken to not introduce air currents that might have an impact on the quality of the glass. For example, direct view cooling devices (e.g., cooling devices with a direct line-of-sight to the glass ribbon) can produce convection currents that can form a rippling of the glass ribbon surface.

[0063] Shown in FIG. 1 is an exemplary glass manufacturing apparatus 10. In some embodiments, the glass manufacturing apparatus 10 can comprise a glass melting furnace 12 that can include a melting vessel 14. In addition to melting vessel 14, glass melting furnace 12 can optionally include one or more additional components such as heating elements (e.g., combustion burners and/or electrodes) configured to heat raw material and convert the raw material into molten glass. For example, melting furnace 14 may be an electrically-boosted melting vessel, wherein energy is added to the raw material through both combustion burners and by direct heating, wherein an electric current is passed through the raw material, and thereby adding energy via Joule heating of the raw material. As used herein, an electrically- boosted melting vessel is a melting vessel that obtains heat energy from both Joule heating and above-surface combustion heating, and the amount of energy imparted to the raw material and/or melt via Joule heating is equal to or greater than about 20%. As used herein, an electrically-boosted melting vessel does not include submerged combustion processes. In some embodiments, the heat energy added to the molten material by Joule heating (X) compared to the total heat energy added to the molten material via both above-surface combustion burners (Y) and Joule heating can be in a range from about 20% to about 80%. For example, the ratio X:Y of heat energy added to the molten material via Joule heating compared to above-surface combustion burners may be 20%:80%, 30%:70%, 40%:60%, 50%:50%, 60%:40%, 70%:30% or even 80%:20%, although in further embodiments other ratios may be used. [0064] In further embodiments, glass melting fumace 12 may include thermal management devices (e.g., insulation components) that reduce heat loss from the melting vessel. In still further embodiments, glass melting fumace 12 may include electronic devices and/or electromechanical devices that facilitate melting of the raw material into a glass melt. Still further, glass melting furnace 12 may include support structures (e.g., support chassis, support member, etc.) or other components.

[0065] Glass melting vessel 14 is typically formed from a refractory material, such as a refractory ceramic material, for example a refractory ceramic material comprising alumina or zirconia, although the refractory ceramic material may comprise other refractory materials, such as yttrium (e.g., yttria, yttria stabilized zirconia, yttrium phosphate), zircon (ZrSi04) or alumina-zirconia-silica or even chrome oxide, used either alternatively or in any combination. In some examples, glass melting vessel 14 may be constructed from refractory ceramic bricks.

[0066] In some embodiments, melting furnace 12 may be incorporated as a component of a glass manufacturing apparatus configured to fabricate a glass article, for example a glass ribbon of an indeterminate length, although in further embodiments, the glass manufacturing apparatus may be configured to form other glass articles without limitation, such as glass rods, glass tubes, glass envelopes (for example, glass envelopes for lighting devices, e.g., light bulbs) and glass lenses, although many other glass articles are contemplated. In some examples, the melting fumace may be incorporated as a component of a glass manufacturing apparatus comprising a slot draw apparatus, a float bath apparatus, a down draw apparatus (e.g., a fusion down draw apparatus), an up draw apparatus, a pressing apparatus, a rolling apparatus, a tube drawing apparatus or any other glass manufacturing apparatus that would benefit from the present disclosure. By way of example, FIG. 1 schematically illustrates glass melting furnace 12 as a component of a fusion down draw glass manufacturing apparatus 10 for fusion drawing a glass ribbon for subsequent processing into individual glass sheets or rolling the glass ribbon onto a spool.

[0067] Glass manufacturing apparatus 10 (e.g., fusion down draw apparatus 10) can optionally include an upstream glass manufacturing apparatus 16 positioned upstream relative to glass melting vessel 14. In some examples, a portion of, or the entire upstream glass manufacturing apparatus 16, may be incorporated as part of the glass melting furnace 12.

[0068] 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. Storage bin 18 may be configured to store a quantity of raw material 24 that can be fed into melting vessel 14 of glass melting furnace 12 through one or more feed ports, as indicated by arrow 26. Raw material 24 typically comprises one or more glass forming metal oxides and one or more modifying agents. In some examples, raw material delivery device 20 can be powered by motor 22 such that raw material delivery device 20 delivers a predetermined amount of raw material 24 from the storage bin 18 to melting vessel 14. In further examples, motor 22 can power raw material delivery device 20 to introduce raw material 24 at a controlled rate based on a level of molten glass sensed downstream from melting vessel 14 relative to a flow direction of the molten glass. Raw material 24 within melting vessel 14 can thereafter be heated to form molten glass 28. Typically, in an initial melting step, raw material is added to the melting vessel as particulate, for example as comprising various "sands". Raw material may also include scrap glass (i.e. cullet) from previous melting and/or forming operations. Combustion burners are typically used to begin the melting process. In an electrically boosted melting process, once the electrical resistance of the raw material is sufficiently reduced (e.g., when the raw materials begin liquefying), electric boost is begun by developing an electric potential between electrodes positioned in contact with the raw materials, thereby establishing an electric current through the raw material, the raw material typically entering, or in, a molten state at this time.

[0069] Glass manufacturing apparatus 10 can also optionally include a downstream glass manufacturing apparatus 30 positioned downstream of glass melting fumace 12 relative to a flow direction of the 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 instances, first connecting conduit 32 discussed below, or other portions of the downstream glass manufacturing apparatus 30, may be incorporated as part of the glass melting fumace 12. Elements of the downstream glass manufacturing apparatus, including first connecting conduit 32, may be formed from a precious metal. Suitable precious metals include platinum group metals selected from the group of metals consisting of platinum, iridium, rhodium, osmium, ruthenium and palladium, or alloys thereof. For example, downstream components of the glass manufacturing apparatus may be formed from a platinum-rhodium alloy including from about 70% to about 90% by weight platinum and about 10% to about 30% by weight rhodium. However, other suitable metals can include molybdenum, rhenium, tantalum, titanium, tungsten and alloys thereof.

[0070] Downstream glass manufacturing apparatus 30 can include a first conditioning (i.e. processing) vessel, such as fining vessel 34, located downstream from melting vessel 14 and coupled to melting vessel 14 by way of the above-referenced first connecting conduit 32. In some examples, molten glass 28 may be gravity fed from melting vessel 14 to fining vessel 34 by way of first connecting conduit 32. For instance, gravity may drive molten glass 28 through an interior pathway of first connecting conduit 32 from melting vessel 14 to fining vessel 34. It should be understood, however, that other conditioning vessels may be positioned downstream of melting vessel 14, for example between melting vessel 14 and fining vessel 34. In some embodiments, a conditioning vessel may be employed between the melting vessel and the fining vessel wherein molten glass from a primary melting vessel is further heated in a secondary vessel to continue the melting process, or cooled to a temperature lower than the temperature of the molten glass in the primary melting vessel before entering the fining vessel.

[0071] As described previously, bubbles may be removed from molten glass 28 by various techniques. For example, raw material 24 may include multivalent compounds (i.e. fining agents) such as tin oxide that, when heated, undergo a chemical reduction reaction and release oxygen. Other suitable fining agents include without limitation arsenic, antimony, iron and cerium, although as noted previously, the use of arsenic and antimony may be discouraged for environmental reasons in some applications. Fining vessel 34 is heated to a temperature greater than the melting vessel temperature, thereby heating the fining agent. Oxygen bubbles produced by the temperature-induced chemical reduction of one or more fining agents included in the melt rise through the molten glass within the fining vessel, wherein gases in the molten glass produced in the melting furnace can coalesce or diffuse into the oxygen bubbles produced by the fining agent. The enlarged gas bubbles with increased buoyancy can then rise to a free surface of the molten glass within the fining vessel and thereafter be vented out of the fining vessel. The oxygen bubbles can further induce mechanical mixing of the molten glass in the fining vessel as they rise through the molten glass.

[0072] The downstream glass manufacturing apparatus 30 can further include another conditioning vessel, such as a mixing apparatus 36, for example a stirring vessel, for mixing the molten glass that flows downstream from fining vessel 34. Mixing apparatus 36 can be used to provide a homogenous glass melt composition, thereby reducing chemical or thermal inhomogeneities that may otherwise exist within the fined molten glass exiting the fining vessel. As shown, fining vessel 34 may be coupled to mixing apparatus 36 by way of a second connecting conduit 38. In some embodiments, molten glass 28 may be gravity fed from the fining vessel 34 to mixing apparatus 36 by way of second connecting conduit 38. For instance, gravity may drive molten glass 28 through an interior pathway of second connecting conduit 38 from fining vessel 34 to mixing apparatus 36. Typically, the molten glass within the mixing apparatus includes a free surface, with a free volume extending between the free surface and a top of the mixing apparatus. It should be noted that while mixing apparatus 36 is shown downstream of fining vessel 34 relative to a flow direction of the molten glass, mixing apparatus 36 may be positioned upstream from fining vessel 34 in other embodiments. In some embodiments, downstream glass manufacturing apparatus 30 may include multiple mixing apparatus, for example a mixing apparatus upstream from fining vessel 34 and a mixing apparatus downstream from fining vessel 34. These multiple mixing apparatus may be of the same design, or they may be of a different design from one another. In some embodiments, one or more of the vessels and/or conduits may include static mixing vanes positioned therein to promote mixing and subsequent homogenization of the molten material.

[0073] Downstream glass manufacturing apparatus 30 can further include another conditioning vessel such as delivery vessel 40 that may be located downstream from mixing apparatus 36. Delivery vessel 40 may condition molten glass 28 to be fed into a downstream forming device. For instance, delivery vessel 40 can act as an accumulator and/or flow controller to adjust and provide a consistent flow of molten glass 28 to forming body 42 by way of exit conduit 44. The molten glass within delivery vessel 40 can, in some embodiments, include a free surface, wherein a free volume extends upward from the free surface to a top of the delivery vessel. As shown, mixing apparatus 36 may be coupled to delivery vessel 40 by way of third connecting conduit 46. In some examples, molten glass 28 may be gravity fed from mixing apparatus 36 to delivery vessel 40 by way of third connecting conduit 46. For instance, gravity may drive molten glass 28 through an interior pathway of third connecting conduit 46 from mixing apparatus 36 to delivery vessel 40.

[0074] Downstream glass manufacturing apparatus 30 can further include forming apparatus 48 comprising the above-referenced forming body 42, including inlet conduit 50. Exit conduit 44 can be positioned to deliver molten glass 28 from delivery vessel 40 to inlet conduit 50 of forming apparatus 48. Forming body 42 in a fusion down draw glass making apparatus can comprise a trough 52 positioned in an upper surface of the forming body and converging forming surfaces 54 (only one surface shown) that converge in a draw direction along a bottom edge (root) 56 of the forming body. Molten glass delivered to the forming body trough via delivery vessel 40, exit conduit 44 and inlet conduit 50 overflows the walls of the trough and descends along the converging forming surfaces 54 as separate flows of molten glass. It should be noted that the molten glass within the forming body trough comprises a free surface, and a free volume extends from the free surface of the molten glass to the top of an enclosure within which the forming body is positioned. The flow of molten glass down at least a portion of the converging forming surfaces is intercepted and directed by a dam and edge directors, as described more fully herein below. The separate flows of molten glass join below and along the root to produce a single ribbon of molten glass 58 that is drawn in a draw direction 60 from root 56 by applying a downward tension to the glass ribbon, such as by gravity, edge rolls and pulling rolls (not shown), to control the dimensions of the glass ribbon as the molten glass cools and a viscosity of the material increases. Accordingly, glass ribbon 58 goes through a visco-elastic transition and acquires mechanical properties that give glass ribbon 58 stable dimensional characteristics. Glass ribbon 58 may in some embodiments be separated into individual glass sheets 62 by a glass separation apparatus (not shown) in an elastic region of the glass ribbon, while in further embodiments, the glass ribbon may be wound onto spools and stored for further processing.

[0075] FIGS. 2 and 3 are cross sectional views of at least a portion of forming apparatus 48 as seen looking edgewise at glass ribbon 58. In addition to forming body 42, forming apparatus 48 comprises enclosure assembly 100 and housing assembly 102. Enclosure assembly 100 can comprise an outer enclosure 104 and an inner enclosure 106 positioned within outer enclosure 104 and spaced apart therefrom. Heating elements 108 may be positioned within the volume 110 separating inner enclosure 106 from outer enclosure 104. Inner enclosure 106 defines a first, upper chamber 112 in which forming body 42 is positioned.

[0076] Forming apparatus 48 may further include cooling doors 114, such as a pair of cooling doors, positioned adjacent forming body root 56 and above housing assembly 102, e.g., between enclosure assembly 100 and housing assembly 102. Cooling doors 114 are arranged on opposite sides of draw plane 1 16 extending through root 56. The glass ribbon 58 may be drawn from root 56 in draw direction 60 along draw plane 116. As depicted, draw plane 116 may bisect forming body 42. Draw plane 116 may be, for example, a vertical plane. However, it should be understood that draw plane 116 may extend at other orientations and need not bisect the forming body.

[0077] Cooling doors 1 14 can be movable in a direction orthogonal to draw plane 1 16, as indicated by arrows 118. Each cooling door 1 14 comprises a plurality of cooling tubes 120 positioned therein, cooling tubes 120 each comprising a longitudinal axis extending substantially orthogonal to draw plane 116. Each cooling tube 120 further includes an open end 122 positioned adjacent thermal plate 124, thermal plate 124 facing draw plane 116 and extending widthwise in a direction parallel with draw plane 1 16. Cooling tubes 120 are supplied with cooling gas 125, such as air, that is exhausted from open ends 122 of cooling tubes 120 and impinges against a back surface of thermal plates 124 opposite draw plane 1 16. Thermal plates 124 are formed from a high temperature resistant, high thermal conductivity material, for example a refractory material such as silicon carbide (SiC). Various forms of SiC, for example, can exhibit a thermal conductivity equal to or greater than 360 W-rn^-K^"1 at 300K. The supply of gas to the cooling tubes can be individually controlled such that a temperature distribution across each thermal plate 124 in a widthwise (lateral) direction can be varied as needed to control a viscosity of the molten glass. For example, a flow rate of cooling gas 125 through a first cooling tube at a first position may be at a first rate and a second flow rate of cooling gas through a second cooling tube may be at a second rate different from the first rate. Thus, the impingement of cooling gas 125 at two different flow rates at two different locations on thermal plate 125 produces different temperatures of the thermal plate in a widthwise direction. Accordingly, a viscosity of the molten glass ribbon adjacent the two different positions corresponding to the first and second cooling tubes can be made different, and a thickness of the molten glass ribbon can therefore be controlled via the cooling doors. In some embodiments, cooling tubes 120 may include heating elements configured to change a temperature of the cooling gas impinging on thermal plate 124 to provide enhanced control of ribbon viscosity.

[0078] Housing assembly 102 comprises an upper housing portion 126 defining an upper housing portion chamber 128, and a lower housing portion 130 defining a lower housing portion chamber 132. One or more partition members 134 may be used, when desired, to increase or decrease the direct "view" of the molten glass in proximity to root 56 to the cooler regions of the draw apparatus, for example within the lower housing portion 130. For example, in some embodiments, partition members 134 may comprise flappers extending into the upper or lower housing portion chamber and capable of rotating about a hinged end 135 to thereby increase or decrease the view between root 56 and structure within lower housing portion 130. That is, the line of sight between root 56 and structural elements of the lower housing portion 130 can be varied. In accordance with the embodiment of FIGS. 2 and 3, partition members 134 are positioned in the upper housing portion, although in further embodiments, the partition members may be positioned in other locations, such as within the lower housing portion or between the upper and lower housing portions. Housing assembly 102 is configured such that glass ribbon 58 descends through both upper and lower chambers 128, 132 as the glass ribbon is drawn from root 56.

[0079] Upper housing portion 126 of housing assembly 102 further comprises a compartment 136 positioned behind a thermal plate 138 configured as a portion of a wall of upper housing portion 126, for example two compartments and two thermal plates positioned on opposite sides of draw plane 116. Each thermal plate 138 is formed from a high temperature resistant, high thermal conductivity material, for example a refractory material such as SiC, and extends in a width wise direction parallel with draw plane 1 16 and adjacent molten glass ribbon 58. Thermal plate 138, for example, may extend across an entire width of glass ribbon 58. Thermal plate 138 comprises a first side 139 facing draw plane 1 16 and an opposing second side 140 (back side 140) facing away from draw plane 1 16. Upper housing portion 126 may further include heating devices 141, such as heating coils or windings, positioned within compartment 136. Upper housing portion 126 may also include refractory insulating material 142 positioned, for example, between heating devices 140 and outer wall section 144 of upper housing portion 126. Outer wall section 144 may, for example, be a metallic wall section that provides shape and strength to the upper housing portion.

[0080] Construction of lower housing portion 130 is similar to the construction of upper housing portion 128. For example, lower housing portion 130 can include heating devices 141 and refractory insulating material 142 positioned between heating devices 141 and outer wall section 146. That is, upper housing portion 126 may be separate and spaced apart from lower housing portion 130. The gap between upper housing portion 126 and lower housing portion 130 may be filled with a refractory insulating material.

[0081] While cooling doors 114 are intended to control a thickness of the glass ribbon across a width thereof, thermal plate 138 is configured for general cooling of the glass ribbon, both in a widthwise direction and along draw direction 60. For example, cooling tubes 120 positioned within cooling doors 1 14 are arrayed adjacent thermal plate 124 with a

longitudinal axis of each cooling tube orthogonal to thermal plate 124. Because the outlet end of each cooling tube 120 is relatively small, the effect of the coolant issuing from each cooling tube is localized, and typically separately controllable as to coolant gas flow.

Separation of individual cooling tubes in the widthwise direction can be, for example, as little as 2.5 cm, or even smaller. Thus, localized viscosity control can be asserted on the ribbon with relatively fine spatial resolution. As described herein below, thermal plate 138 is cooled less selectively. [0082] As best seen in FIG. 3, which is a close up view of a portion of lower housing assembly 102, at least one cooling tube 148 is positioned within compartment 136 adjacent back wall 140 of thermal plate 138. That is, thermal plate 138 is positioned between the at least one cooling tube 148 and draw plane 116. Compartment 136 is isolated from upper housing portion chamber 128. For example, the various refractory panels that form the compartment can be pieced together with lap joints to provide structural support and avoid gaseous interchange between the compartment and the upper housing portion chamber. In some embodiments, cement may be used at the joints. Air tightness is not required, however. The at least one cooling tube 148 extends widthwise into compartment 136. That is, the at least one cooling tube 148 comprises a longitudinal axis that extends in a widthwise direction orthogonal to draw direction 60 and parallel with draw plane 116 and thermal plate 138. The at least one cooling tube can, for example, extend through port or other opening in a wall of the upper housing portion. In some embodiments, the cooling tube 148 may be a closed cooling tube in which a cooling fluid is passed, but which cooling fluid is not exhausted from the cooling tube within compartment 136 or otherwise directed at or impinging on thermal plate 138. In other embodiments, the at least one cooling tube 148 comprises at least one orifice arranged along a length of the cooling tube such that a cooling gas is expelled from the at least one orifice and impinges on a surface of thermal plate 138 within compartment 136. As shown in FIG. 3, in some embodiments, the cooling tube may be arranged such that the cooling fluid is exhausted toward thermal plate 138 at a non-perpendicular angle relative to draw plane 116. In other embodiments, the cooling fluid can be exhausted toward thermal plate 138 at a perpendicular angle relative to draw plane 116. For example, as shown in FIG. 3, an upper-most cooling tube positioned behind thermal plate 138 may be oriented to exhaust cooling fluid in a downward direction toward thermal plate 138, a lower-most cooling tube may be oriented to direct cooling fluid in an upward direction toward thermal plate 138, and a central cooling tube may be oriented to direct cooling fluid in a direction perpendicular to thermal plate 138. Directing the cooling fluid at an angle away from the joints connecting the thermal plate 138 to the surrounding portions of upper housing portion 126 can reduce the possibility of the cooling fluid leaking into upper housing portion chamber 128. In still other embodiments, a mix of cooling tube designs may be used, both closed cooling tubes (hereinafter radiative type cooling tubes) and cooling tubes designed to exhaust a cooling fluid against thermal plate 138 (hereinafter injection type cooling tubes). For example, the upper-most and lower-most cooling tubes could be radiative type cooling tubes, while the central cooling tube (or tubes) are injection type cooling tubes. [0083] Referring now to FIGS. 4A and 4B, a longitudinal cross sectional view and an axial cross sectional view of an exemplary cooling tube 148, respectively, are shown. More particularly, a radiative type cooling tube 148a is depicted, cooling tube 148a comprising first, outer tube 200 extending longitudinally along central longitudinal axis 202 between proximal end 204 and distal end 206. As noted above, cooling tube 148a is termed a radiative type cooling tube because no gas is expelled from the cooling tube except through fittings (not shown) designed to supply or remove the cooling fluid to the cooling tube. That is, cooling tube 148a does not comprise orifices designed to exhaust cooling fluid from the cooling tube against thermal plate 138, and cooling is primarily a function of radiative exchange between the thermal plate and the cooling tube 148a. While convective cooling may occur with cooling tube 148a, it is not the principal mechanism for cooling.

[0084] Cooling tube 148a further comprises second, inner tube 208 interior to and spaced apart from first tube 200, second tube 208 extending longitudinally along central longitudinal axis 202 between proximal end 210 and distal end 212. Distal end 206 of first tube 200 is a closed end, while distal end 212 of second tube 208 is an open end. In some embodiments, first tube 200 can be a cylindrical tube comprising a circular cross sectional shape in a plane perpendicular to longitudinal axis 202. In some embodiments, second tube 208 may be a cylindrical tube, with a circular cross sectional shape in the plane perpendicular to longitudinal axis 202. Second tube 208 may, for example, be concentric with first tube 200. However, in other embodiments, either one or both of first and second tubes 200, 208 can exhibit other cross sectional shapes, including without limitation elliptical shapes, rectangular shapes, triangular shapes, or any other suitable cross sectional shape.

[0085] A gap between first tube 200 and second tube 208 formed by the spaced apart relationship forms a first passage 214 extending between first and second tubes 200 and 208. In addition, second tube 208 defines a second, central passage 216 interior to and extending along the length of second tube 208 between proximal end 210 and distal end 212, second passage 216 in fluid communication with first passage 214 via open distal end 212. A cooling fluid 218, for example water, is supplied to second passage 216 at proximal end 210 from a cooling fluid source (not shown) and flows along second passage 216 in a direction from proximal end 210 to open distal end 212. At open distal end 212, cooling fluid 218 enters first passage 214, flowing along first passage 214 in a direction toward proximal end 204 opposite the direction the cooling fluid took when traversing through second passage 216. Cooling fluid 218 leaving first passage 214 can be collected and recycled back through first and second tubes 200, 208, such as after filtering (and chilling if desired), or cooling fluid 218 can be discarded as waste and treated appropriately. Cooling fluid 218 may be a liquid cooling fluid, a gaseous cooling fluid, or cooling fluid may comprise both liquid and gas.

[0086] As described above, thermal plate 138 can be cooled radiatively from back surface 140 of thermal plate 138 using one or more cooling tubes 148a. That is, in some

embodiments, cooling tubes may be positioned behind thermal plate 138 that rely principally on thermal radiation between thermal plate 136 and the cooling tubes. However, simply installing additional radiative cooling devices within upper chamber 128, for example to compensate for increased heat load, cannot, after a point, meaningfully increase heat extraction from the glass ribbon because the thermal plate acts as a radiation shield and limits radiative cooling. Moreover, as the thermal plate temperature is decreased, the change in average radiative heat flux between the glass and the thermal plate per unit temperature change, decreases. Thus, a small change in average heat flux requires a large decrease in thermal plate temperature.

[0087] Referring now to FIGS. 5A, 5B and 5C, two longitudinal cross sectional views and an axial cross sectional view of another exemplary cooling tube 148, respectively, are shown. More particularly, an injection type cooling tube 148b is shown comprising a tube 300 extending longitudinally along longitudinal axis 302 between proximal end 304 and distal end 306. Tube 300 may, in some embodiments, comprise a circular cross section in a plane orthogonal to longitudinal axis 302, although in further embodiments, tube 300 may have other shapes, for example a rectangular shape, an elliptical shape, a triangular shape, or any other suitable cross sectional shape. Tube 300 defines a central passage 308 extending longitudinally along a length of tube 300, and into which a cooling fluid 310 is delivered. In accordance with the embodiment of FIGS. 5A, 5B and 5C, tube 300 comprises only a single longitudinal passage, i.e., passage 308.

[0088] Tube 300 further includes at least one orifice 310 extending through a wall of tube 300 to an environment outside of the tube. In some embodiments, tube 300 may comprise a plurality of orifices 310, such as depicted in FIG. 5 A. As illustrated in FIG. 5 A, the plurality of orifices 310 can be arranged along a length of tube 300, for example in general alignment with longitudinal axis 302. In other embodiments, such as the embodiment of FIG. 5B, the at least one orifice 310 may be a single high aspect ratio slot extending along at least a portion of the length of tube 300, for example at least 25% of the length of the tube 300 between the proximal and distal ends 304, 306, such as equal to or greater than 50% of the length, for example equal to or greater than 75% of the length of tube 300. In some embodiments, a single slot extending equal to or greater than about 25% of the length of the tube may be aligned parallel with longitudinal axis 302. In still further embodiments, tube 300 may comprise a plurality of shorter slots, i.e., wherein each slot of the plurality of slots is equal to or less than about 40% of the length of tube 300, for example equal to or less than about 25%, equal to or less than about 15%, or equal to or less than about 5% of the length of tube 400. The plurality of orifices, regardless of shape, may be linearly aligned, e.g., parallel with longitudinal axis 302, although in further embodiments, the plurality of orifices may be arranged in other patterns.

[0089] As illustrated in FIGS. 5A and 5B, a cooling gas 312 (e.g., air) delivered to passage 308 from proximal end 304 is blocked at closed distal end 306 and thereby forced through the at least one orifice 310. When positioned within compartment 136, cooling tube 148b can be oriented such that the cooling fluid exiting the at least one orifice 212 is directed at and impinges against back side 140 of thermal plate 138.

[0090] FIGS. 6A, 6B and 6C depict two longitudinal cross sectional views and an axial view, respectively, of another exemplary injection-type cooling tube 148. More specifically, FIGS.6A - 6C show a cooling tube 148c comprising an outer, first tube 400 extending along longitudinal axis 402 between proximal end 404 and a closed distal end 406. Cooling tube 148c further comprises a second tube 408 disposed interior to and spaced apart from first tube 400, second tube 408 extending along longitudinal axis 402 between proximal end 410 and a closed distal end 412. Additionally, cooling tube 148a comprises a third tube 414 disposed interior to and spaced apart from second tube 408, third tube 414 extending along longitudinal axis 402 between proximal end 416 and an open distal end 418. First, second and third tubes 400, 408 and 414 may be formed from any material capable of withstanding temperatures in excess of 400°C, for example in excess of 600°C, such as in excess of 800°C. For example, in some embodiments, first, second and third tubes 400, 408 and 414 may be formed of stainless steel. Other suitable materials can include nickel alloys, titanium alloys, molybdenum alloys, tungsten alloys and cobalt alloys, for example Hastelloy® brand metals produced by Haynes International.

[0091] The gap between first tube 400 and second tube 408 forms a first passage 420, while the gap between second tube 408 and third tube 414 forms a second passage 422. Additionally, third tube 414 defines a third, central passage 424 interior to third tube 314. Third passage 424 is in fluid communication with second passage 422 via open distal end 418. However, first passage 420 is isolated from second and third passages 422 and 424. [0092] In operation, a first cooling fluid 426 is supplied to third passage 424 at proximal end 416. First cooling fluid 426 may be a liquid cooling fluid, a gaseous cooling fluid, or a combination of liquid and gas. First cooling fluid 426 flows within third passage 424 from proximal end 416 along longitudinal axis 402 toward open distal end 418. At open distal end 418, first cooling fluid 426 flows therefrom and enters second passage 422, flowing from distal end 418 in a direction toward proximal end 410 of second tube 408, opposite the direction of first cooling fluid 426 within third passage 424. In some embodiments, cooling fluid 426 flowing from proximal end 410 may be collected and cycled in a closed loop system back to third passage 424. However, in other embodiments, first cooling fluid 426 may be discarded as waste and treated appropriately.

[0093] In addition to first cooling fluid 426, a second cooling fluid 428, for example a cooling gas (e.g., air) is supplied to first passage 420. Second cooling fluid 428 flows from proximal end 404 in a direction toward closed distal end 406 of first tube 400, and, with no other outlet, second cooling fluid 428 is exhausted through at least one orifice 430 extending through a wall of first tube 400 to an environment outside of the tube. In some embodiments, tube 400 may comprise a plurality of orifices 430, such as depicted in FIG. 6A. As illustrated in FIG. 6A, the plurality of orifices 430 can be arranged along a length of tube 400, for example in general alignment with longitudinal axis 402. In other embodiments, such as the embodiment of FIG. 6B, the at least one orifice 430 may be a single high aspect ratio slot extending along at least a portion of the length of tube 400, for example at least 25% of the length of first tube 400 between the proximal and distal ends 404, 406, such as equal to or greater than 50% of the length, for example equal to or greater than 75% of the length of tube 400. In some embodiments, a single slot extending equal to or greater than about 25% of the length of first tube 400 may be aligned parallel with longitudinal axis 402. In still further embodiments, first tube 400 may comprise a plurality of shorter slots, i.e., wherein each slot of the plurality of slots is less than about 40% of the length of first tube 400, for example equal to or less than about 25%, equal to or less than about 15%, or equal to or less than about 5% of the length of tube 300. The plurality of orifices, regardless of shape, may be linearly aligned, e.g., parallel with longitudinal axis 402, although in further embodiments, the plurality of orifices may be arranged in other patterns. It should be apparent from the foregoing description and with the aid of FIGS. 6A and 6B that the role of cooling fluid 426 is to cool the incoming cooling gas 428 that is exhausted from cooling tube 148c through the at least one orifice 430. However, because cooling gas 428 travels through first passage 420 along the wall of first tube 400, the cooling gas is heated as it traverses along first passage 420. Consequently, the cooling gas exhausted from cooling tube 148c near distal end 406 is at a higher temperature than the cooling gas exhausted from cooling tube 148c near proximal end 404. Thus, cooling tube 148c does not provide consistent cooling along its length.

[0094] FIGS. 7 A, 7B and 7C illustrate a longitudinal cross sectional view and an axial cross sectional view, respectively, of still another exemplary injection-type cooling tube 148. More specifically, FIGS. 7A - 7C show a cooling tube 148d comprising first, outer tube 500 extending along longitudinal axis 502 between proximal end 504 and distal end 506. In some embodiments, first tube 500 may be a cylindrical tube, although in other embodiments first tube 500 can have other cross sectional shapes in a plane orthogonal to longitudinal axis 502, such as a rectangular cross sectional shape, an elliptical cross sectional shape, a triangular cross sectional shape, or any other suitable cross sectional shape.

[0095] In accordance with the embodiment of FIGS. 7A - 7C, first tube 500 is a double walled tube comprising an outer wall 518 and an inner wall 520 interior to and spaced apart from outer wall 518, thereby forming a first passage 522 between the inner wall and the outer wall. Outer wall 518 and inner wall 520 are joined at distal end 506 around the perimeters of the outer and inner walls such that first passage 522 is closed off (sealed) at distal end 506.

[0096] Cooling tube 148d further comprises a second, inner tube 530 extending between proximal end 532 and distal end 534 and positioned interior to and spaced apart from first tube 500 (i.e., interior to inner wall 520). In some embodiments, second tube 530 may have a cross sectional shape in a plane orthogonal to longitudinal axis 502 that is circular and concentric with first tube 500. However, in further embodiments, second tube 530 may comprise other cross sectional shapes, for example an elliptical cross sectional shape, a rectangular cross sectional shape, a triangular cross sectional shape, or any other suitable cross sectional shape. Second tube 530 is spaced apart from first tube 500 (spaced apart from inner wall 520), thereby forming a second passage 536 extending between first and second tubes 500, 530 (between inner wall 520 and second tube 530).

[0097] Second tube 530 further defines a central third passage 540 extending along and interior to second tube 530. Second passage 536 and third passage 540 are in fluid communication with each other via open distal end 534.

[0098] In operation, a first cooling fluid 542 is supplied to third passage 540 at proximal end 532 of second tube 530, first cooling fluid 542 flowing down the length of third passage 540 in a direction away from proximal end 532 and toward distal end 534. First cooling fluid 542 exits third passage 540 through an opening defined by second tube 530 at distal end 534 and enters second passage 536. First cooling fluid 542 entering second passage 536 from third passage 540 is then directed through second passage 536 in a direction away from distal end 506. First cooling fluid 542 exiting first passage 536 can be recovered, for example in a closed loop system, whereupon first cooling fluid 542 may be filtered and/or chilled and/or otherwise processed, and then returned to central passage 540, or first cooling fluid 542 may be discharged as waste and treated accordingly. In some embodiments, first cooling fluid 542 can be a liquid, such as water. However, in further embodiments, first cooling fluid 542 can be another cooling medium, such as a cooling gas, e.g., air.

[0099] With first cooling fluid 542 supplied to third passage 540, a second cooling fluid 544 may be supplied to first passage 522 between outer and inner walls 518, 520. Second cooling fluid 544 flows through first passage 522 in a direction toward distal end 506, but is blocked at closed distal end 506. Accordingly, second cooling fluid 544 is forced through at least one orifice 546 extending from first passage 522 to an environment external to first tube 500. Second cooling fluid 544 is a gaseous cooling fluid, for example air. In some embodiments, tube 500 may comprise a plurality of orifices 546, such as depicted in FIG. 7A. As illustrated in FIG. 7A, the plurality of orifices 546 can be arranged along a length of tube 500, for example in general alignment with longitudinal axis 502. In other embodiments, such as the embodiment of FIG. 7B, the at least one orifice 546 may be a single high aspect ratio slot extending along at least a portion of the length of tube 500, for example at least 25% of the length of the tube 500 between the proximal and distal ends 504, 506, such as equal to or greater than 50% of the length, for example equal to or greater than 75% of the length of tube 500. In some embodiments, a single slot extending equal to or greater than about 25% of the length of the tube may be aligned parallel with longitudinal axis 502. In still further embodiments, tube 500 may comprise a plurality of shorter slots, i.e., wherein each slot of the plurality of slots is equal to or less than about 50% of the length of tube 500, for example equal to or less than about 25%, equal to or less than about 15%, or equal to or less than about 5% of the length of tube 500. The plurality of orifices, regardless of shape, may be linearly aligned, e.g., parallel with longitudinal axis 502, although in further embodiments, the plurality of orifices may be arranged in other patterns.

[00100] When positioned within compartment 136, cooling tube 148d can be arranged such that second cooling gas 544 exiting the at least one orifice 546 is directed at and impinges on thermal plate 138.

[00101] First and second tubes 500 and 530 may be formed from any material capable of withstanding temperatures in excess of 400°C, for example in excess of 600°C, such as in excess of 800°C. For example, in some embodiments, first and second tubes 500 and 530 may be formed of stainless steel. Other suitable materials can include nickel alloys, titanium alloys, molybdenum alloys, tungsten alloys and cobalt alloys, for example Hastelloy® brand metals produced by Haynes International.

[00102] It should be clear from the foregoing that the injection-type cooling tubes represented by the embodiments shown FIGS. 5A - 5C, 6A - 6C and 7 A - 7C entail heating of the cooling fluid exhausted from the one or more orifices. That is, since the primary cooling fluid in each case traverses a passage directly adjacent the outside environment, when that outside environment is a hot environment, the cooling fluid is heated by the outside environment as the cooling gas traverses the length of the cooling tube. When used as a cooling tube in a glass making process, such as within compartment 136, and arrayed in a widthwise direction, the result may be uneven cooling of the glass ribbon from one edge of the ribbon to the opposite edge.

[00103] FIGS. 8A, 8B and 8C illustrate two longitudinal cross sectional views and an axial cross sectional view, respectively, of yet another exemplary injection-type cooling tube 148. More specifically, FIGS. 8A - 8C show a cooling tube 148e comprising first, outer tube 600 extending along longitudinal axis 602 between proximal end 604 and distal end 606. In some embodiments, first tube 600 may be a cylindrical tube with a circular cross sectional shape in a plane orthogonal to longitudinal axis 602, although in other embodiments first tube 600 can have other cross sectional shapes, such as a rectangular cross sectional shape, an elliptical cross sectional shape, a triangular cross sectional shape, or any other suitable cross sectional shape. First tube 600 may be formed from any suitable material capable of withstanding temperatures in excess of 400°C, for example in excess of 600°C, such as in excess of 800°C. For example, in some embodiments, first tube 600 may be formed of stainless steel, or variants thereof. Other suitable materials can include nickel alloys, titanium alloys, molybdenum alloys, tungsten alloys and cobalt alloys, for example Hastelloy® brand metals produced by Haynes International.

[00104] Cooling tube 148e may further comprise an inner, second tube 610 extending between proximal end 612 and distal end 614 and positioned inside first tube 600. In some embodiments, second tube 610 may have a cross sectional shape in a plane orthogonal to longitudinal axis 602 that is circular and concentric with first tube 600. However, in further embodiments, second tube 610 may comprise other cross sectional shapes, for example an elliptical cross sectional shape, a rectangular cross sectional shape, or any other suitable cross sectional shape. Second tube 610 is spaced apart from first tube 600, thereby forming a first passage 616 positioned between first and second tubes 600, 610. Second tube 610 may be formed of stainless steel. Other suitable materials can include nickel alloys, titanium alloys, molybdenum alloys, tungsten alloys and cobalt alloys, for example Hastelloy® brand metals produced by Haynes International

[00105] In accordance with the embodiment of FIGS. 8A - 8C, second tube 610 is a double walled tube comprising outer wall 618 and inner wall 620 interior to and spaced apart from outer wall 618, thereby forming a second passage 622 between the inner wall and the outer wall. Outer wall 618 and inner wall 620 are joined at distal end 614 around the perimeters of the outer and inner walls such that second passage 622 is closed off at distal end 614 and isolated from first passage 616.

[00106] Still referring to FIGS. 8A - 8C, inner wall 620 defines a central passage 624 extending through second tube 610 and in fluid communication with first passage 616 through an opening at distal end 614. However, central passage 620 is isolated from second passage 622.

[00107] Cooling tube 148e further comprises a blocking member 626 positioned between first tube 600 and outer wall 618 of second tube 610, blocking member 626 extending along at least a portion of the length of outer wall 618. As shown in FIG. 8C, blocking member 626 further extends across an angular range between first tube 600 and second tube 610, i.e., over an angle a. Angle a may be, for example, equal to or less than 180 degrees, for example equal to or less than about 90 degrees, such as equal to or less than about 45 degrees, or even equal to or less than about 20 degrees. At least one orifice 628 is provided that extends from second passage 622 through outer wall 618, blocking member 626 and first tube 600 such that the at least one orifice provides fluid communication between second passage 622 and the environment outside of cooling tube 148e.

[00108] In some embodiments, such as the embodiment of FIG. 8 A, a plurality of orifices 628 can be arranged along a length of first tube 600, for example in a general direction of longitudinal axis 602. In other embodiments, such as the embodiment of FIG. 8B, the at least one orifice 628 may be a high aspect ratio slot extending along at least a portion of the length of blocking member 626, for example at least 25% of the length of blocking member 626, such as equal to or greater than 50% of the length, for example equal to or greater than 75% of the length of blocking member 626. In still further embodiments, a plurality of shorter slots may be provided, i.e., wherein each slot of the plurality of slots is equal to or less than about 50% of the length of blocking member 626, for example equal to or less than about 25%, equal to or less than about 15%, or equal to or less than about 5% of the length of blocking member 626. The plurality of orifices 628, regardless of shape, may be linearly aligned, e.g., parallel with longitudinal axis 602. Indeed, a slot extending equal to or greater than about 25% of the length of the blocking member may be aligned parallel with longitudinal axis 602.

[00109] In operation, a first cooling fluid 640 is supplied to central passage 624 at proximal end 612 of second tube 610, first cooling fluid 640 flowing down the length of central passage 624 in a direction away from proximal end 612 and toward distal end 614, first cooling fluid 640 exiting central passage 624 through the opening defined by inner wall 620 at distal end 614, and thereafter entering first passage 616. First cooling fluid 640 entering first passage 616 from central passage 624 is then directed through first passage 616 in a direction toward proximal end 604. First cooling fluid 640 exiting first passage 616 can be recovered, for example in a closed loop system, whereupon the first cooling fluid may be filtered and/or chilled and/or otherwise processed, and then returned to central passage 624, or first cooling fluid 630 may be discharged as waste and treated accordingly. In some embodiments, first cooling fluid 640 can be a liquid, such as water. However, first cooling fluid 640 can be another cooling medium, such as a cooling gas, such as air.

[00110] In addition to supplying first cooling fluid 640 to central passage 624, a second cooling fluid 642 is supplied to second passage 622. Second cooling fluid 642 flows through second passage 622 in a direction toward distal end 614, but is blocked at closed distal end 614. Accordingly, second cooling fluid 642 is forced through the one or more orifices 628 extending from second passage 622 to the environment external to first tube 600. Second cooling fluid 632 is a gaseous cooling fluid, for example air.

[00111] It can be seen that the combination of central passage 624 and first passage 616, in fluid communication with each other, provides a cooling jacket in contact with outer wall 618 about second passage 622. Surrounding second cooling fluid 642 with a cooling jacket (e.g., first cooling fluid 640) helps maintain a relatively low temperature of second cooling fluid 632 as it traverses second passage 622, thereby improving cooling efficiency and reducing across-the-draw temperature non-uniformity.

[00112] FIGS. 9A, 9B and 9C show two longitudinal cross sectional views and an axial cross sectional view, respectively, of another exemplary injection-type cooling tube 148. More specifically, FIGS. 9A - 9C show a cooling tube 148f comprising an outer, first tube 700 extending along longitudinal axis 702 between proximal end 704 and distal end 706. First tube 700 may be a cylindrical tube with a circular cross sectional shape in a plane orthogonal to longitudinal axis 702, although in further embodiments, first tube 700 may have other shapes, for example an elliptical shape, a rectangular shape, or any other appropriate shape.

[00113] Cooling tube 148f may further comprise an inner, second tube 710 extending along longitudinal axis 702 between proximal end 712 and closed distal end 714 along longitudinal axis 702, second tube 710 positioned interior to and spaced apart from first tube 700, forming a gap between first tube 700 and second tube 710. In some embodiments, second tube 710 may comprise a circular cross sectional shape concentric with first tube 700, although in further embodiments, second tube 710 can have other cross sectional shapes, such as an elliptical shape or a rectangular shape, or any other suitable shape. At least two blocking members 716, 718 are positioned in the gap between first and second tubes 700, 710 and extend along at least a portion of a length of second tube 710, dividing the gap between first tube 700 and second tube 710 into first and second passages 720 and 722 that are in fluid communication with each between distal end 714 and distal end 706. Blocking members 716 and 718 each further extend across an azimuthal angular range between first tube 700 and second tube 710, i.e., over an angle β. Angle β may be, for example, equal to or less than 90 degrees, for example equal to or less than about 45 degrees, or even equal to or less than about 20 degrees, although each blocking member may extend over other angles. The angular extent of each blocking member can be the same as the other blocking member, or different. Second tube 710 further defines a central, third passage 724 extending along the length of second tube 710, wherein central passage 720 isolated from both of passages 720 and 722.

[00114] Blocking members 716, 718 serve the dual purpose of dividing the gap between first and second tubes 700, 710 into first and second passages 720, 722 and providing orifices for a cooling gas to exhaust from the cooling tube while isolated from first and second passages 720, 722. First tube 700 and/or second tube 710, and/or blocking members 716, 718 may be formed of stainless steel. Other suitable materials can include nickel alloys, titanium alloys, molybdenum alloys, tungsten alloys and cobalt alloys, for example Hastelloy® brand metals produced by Haynes International.

[00115] In operation, a first cooling fluid 730, for example water, flows into first passage 720 at proximal end 704, and flows longitudinally along first passage 720 in a direction toward distal end 706. First cooling fluid 730 then enters second passage 722 and flows in a direction toward proximal end 704, opposite the direction of flow in first passage 720. First cooling fluid 730 returning toward proximal end 704 may be recycled in a closed loop cooling system, wherein first cooling fluid 730 can be filtered, chilled, for example in a refrigeration unit, and flowed back to first passage 720. However, in further embodiments, first cooling fluid can be discarded as waste and appropriately treated. A second cooling fluid 732, for example a cooling gas, such as air, is supplied to central passage 724 at proximate end 712 of second tube 710. Second cooling fluid 732 is prevented from exiting at closed distal end 714 of second tube 710, and is forced out of central passage 724 through the at least one orifice 726 extending from third passage 724 through a wall of second tube 710, blocking members 716, 718, and first tube 700 to the environment exterior to cooling tube 148f. In some embodiments, such as the embodiment of FIG. 9A, each blocking member 716, 718 may comprise a plurality of orifices 726 extending therethrough. However, in other embodiments, only a single orifice 726 in each blocking member may be present. For example, in some embodiments, such as the embodiment of FIG. 9B, cooling tube 148f may comprise a single slot-shaped orifice 726 extending along at least a portion of the length of each blocking member, providing fluid communication between third passage 724 and the exterior of cooling tube 148f. The at least one orifice 726 may be a high aspect ratio slot extending along at least a portion of the length of a blocking member, for example at least 25% of the length of a blocking member, such as equal to or greater than 50% of the length, for example equal to or greater than 75% of the length of a blocking member. Indeed, a single slot extending equal to or greater than about 25% of the length of a blocking member may be aligned parallel with longitudinal axis 702. In still further embodiments, a plurality of shorter slots may be provided, i.e., wherein each slot of the plurality of slots is equal to or less than about 50% of the length of a blocking member 716 and/or 718, for example equal to or less than about 25%, equal to or less than about 15%, or equal to or less than about 5% of the length of the blocking members. The plurality of orifices 726, regardless of shape, may be linearly aligned, e.g., parallel with longitudinal axis 702.

[00116] As with the embodiment of FIGS. 8A - 8C, the embodiments of FIGS. 9A - 9C provide a cooling jacket flowing outside of and in contact with second tube 710, forming a cooling jacket around cooling fluid 732, thereby improving cooling efficiency and reducing across-the-draw temperature non-uniformity.

[00117] While FIGS. 9A - 9C illustrate a first orifice, or array of orifices, and a second orifice or array of orifices positioned 180 degrees from the first orifice or array of orifices, the angular offset of the sets of orifices need not be 180 degrees, as other angular offsets may be employed depending on need. In some embodiments, one set of orifices can be blocked, such that cooling gas 732 is exhausted from only one orifice, or array of orifices through a single blocking member.

[00118] While the cooling tubes described above can provide rapid cooling of the glass ribbon positioned on the opposite side of thermal plate 138, exhausted cooling gas (e.g., cooling gases 312, 428, 544, 642, 732), if not removed from compartment 136, may leak through seams where the cooling plate meets other wall members of upper housing portion 126, thereby causing air currents within chamber 128. Accordingly, in some embodiments, at least one exhaust tube 750 may be provided, the at least one exhaust tube 750 extending from compartment 136 to an atmosphere external to upper housing portion 126. For example, in some embodiments, the at least one exhaust tube 750 may be arranged in fluid communication with a vacuum source, wherein gas is actively removed from compartment 136 through exhaust tube 750, thereby preventing pressurization of compartment 136 due to the buildup of cooling gas being exhausted from the at least one cooling tube 148 when injection-type cooling tubes are employed (e.g., cooling tubes 148b - 148f).

[00119] FIG. 10 illustrates temperature along the centerline of the glass ribbon (a line extending in draw direction 60 midway between the lateral edges of the ribbon) as a function of distance below the root of the forming body, and the temperature difference for an arrangement of six cooling tubes positioned on both sides of the ribbon (three per side) within the upper housing portion behind a cooling plate. The data compare the case 1) where all six cooling tubes are 2.1 cm in diameter and of a closed, water-cooled variety relying on radiative heat exchange as shown in FIG. 4A, curve 800, and the case 2) where the middle cooling tube of each group of three 2.1 cm cooling tubes was of the injection variety (e.g., cooling tubes of the type disclosed in FIG. 6B), wherein a cooling gas (air) was directed at the back side of the thermal plate from a slot extending along a length of the cooling tube at a mass flow rate of 1077.3 kg/hr, curve 802. Cases 1) and 2) were compared to a baseline case (curve 804) involving four 3.8 cm diameter closed, water-cooled radiative-style cooling tubes, two cooling tubes behind a thermal plate on each side of the ribbon. Curve 806 depicts the temperature difference between the baseline case and case 1), while curve 808 depicts the temperature difference between the baseline case and case 2). The data show that replacing only one radiative-type cooling tube on each side of the ribbon with an impingement-style cooling tube reduced the centerline temperature by about 27% over the case where all cooling tubes were of a closed, radiative design. [00120] FIG. 11 shows the calculated temperature rise of the cooling gas flowing through a cooling tube as shown in FIG. 6B (curve 900) and the cooling tube of FIG. 8B (curve 902) as a function of distance from the proximal end of the cooling tube. As was expected, the temperature rise (325°C) of the cooling fluid flowing through an existing cooling tube was greater than the temperature rise (25°C) of the cooling fluid flowing through the cooling tube of FIG. 8B. In accordance with this example, the low temperature of cooling air in cooling tube of FIG. 8B, wherein the cooling fluid exhausted by the cooling tube is cooled by a second cooling fluid conveyed as a cooling jacket about the flow of the first cooling fluid will improve the cooling efficiency of the impinging jets and the minimal variation of cooling air temperature between upstream and downstream ends (proximal and distal ends) of the cooling tube can improve cross draw temperature uniformity on the glass ribbon.

[00121] In some embodiments, lower housing portion 130 may include at least one cooling tube 148 positioned within lower housing portion chamber 132. Because the glass ribbon is less susceptible to influence from convection (i.e., air currents) within lower housing portion chamber 132 than within the upper chamber 128, the at least one cooling tube 148 within chamber 132 can have a direct view of the glass ribbon and does not need to be positioned behind a barrier placed between the glass ribbon and the cooling tube.

[00122] It should be understood that several different styles of cooling tubes may be employed within compartment 136. In some embodiments, a mix of closed, radiative style cooling tubes (e.g., cooling tubes 148a) and injection-type cooling tubes (cooling tubes 148b - 148f) may be positioned within compartment 136. Additionally, the mass flow rate of cooling fluids through the cooling tubes may be varied to vary the cooling capacity of each cooling tube when desired.

[00123] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiments of the present disclosure without departing from the spirit and scope of the disclosure. Thus it is intended that the present disclosure cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. An apparatus for cooling a glass ribbon, comprising:

a forming body configured to form a glass ribbon along a draw plane;

a housing assembly positioned below the forming body and through which the glass ribbon is drawn in a draw direction;

at least one cooling tube positioned in the housing assembly, the at least one cooling tube comprising a longitudinal axis extending parallel with the draw plane and orthogonal to the draw direction; and

a thermal plate positioned between the at least one cooling tube and the draw plane, the at least one cooling tube oriented to direct the flow of cooling gas against the thermal plate.

2. The apparatus according to claim 1 , wherein the at least one cooling tube comprises at least one orifice configured to direct a flow of cooling gas from the cooling tube.

3. The apparatus according to claim 1 , wherein the at least one cooling tube is a linear cooling tube.

4. The apparatus according to claim 1, wherein the housing assembly comprises an upper housing portion and a lower housing portion.

5. The apparatus according to claim 4, wherein the thermal plate is positioned in the upper housing portion.

6. The apparatus according to claim 1 , wherein the at least one cooling tube comprises a plurality of cooling tubes.

7. The apparatus according to claim 6, wherein the plurality of cooling tubes comprises at least one closed cooling tube and at least one cooling tube comprising at least one orifice configured to direct a flow of cooling gas from the cooling tube.

8. The apparatus according to claim 2, wherein the at least one orifice comprises a plurality of orifices.

9. The apparatus according to claim 1 , wherein the at least one cooling tube comprises: a first tube;

a second tube positioned interior to and spaced apart from the first tube, a gap between the first tube and the second tube forming a first passage configured to receive a flow of cooling fluid, the second tube comprising an outer wall and an inner wall, a gap between the outer wall and the inner wall forming a second passage isolated from the first passage, the inner wall defining a third passage in fluid communication with the first passage; a blocking member positioned between and in contact with the first tube and the second tube, the blocking member extending along at least about 50% of a length of the second tube; and

wherein the at least one orifice extends between the second passage and an exterior of the first tube.

10. The apparatus according to claim 9, wherein the at least one orifice comprises a slot extending along at least 50% of a length of the blocking member.

11. The apparatus according to claim 1 , wherein the at least one cooling tube comprises: a first tube;

a second tube positioned interior to and spaced apart from the first tube to form a gap therebetween;

a pair of blocking members positioned in the gap between and in contact with the first tube and the second tube, the blocking members dividing the gap into a first passage and a second passage in fluid communication with the first passage; and

wherein the second tube defines a third passage interior to and extending along a length of the second tube and isolated from the first and second passages, the at least one orifice extending between the third passage and an exterior of the first tube.

12. The apparatus according to claim 11 , wherein the at least one orifice comprises a slot extending along at least 50% of a length of the blocking member

13. The apparatus according to claim 4, wherein the upper housing portion comprises a compartment positioned behind the thermal plate relative to the draw plane, and the at least one cooling tube is positioned within the compartment.

14. The apparatus according to claim 13, wherein the compartment is isolated from an interior atmosphere of the upper housing portion.

15. The apparatus according to claim 13, wherein the upper housing portion further comprises an exhaust tube providing fluid communication between the compartment and an atmosphere outside the upper housing portion.

16. The apparatus according to claim 13, wherein the lower housing portion comprises a chamber through which the glass ribbon is drawn, the lower housing portion comprising at least one cooling tube positioned within the lower housing portion chamber extending in a direction parallel with the draw plane and orthogonal to the draw direction, and in direct view of the glass ribbon.

17. The apparatus according to claim 16, wherein the at least one cooling tube positioned within the lower housing portion chamber comprises at least one orifice configured to direct a flow of cooling gas onto the glass ribbon.

18. The apparatus according to claim 16, wherein the at least one cooling tube positioned within the lower housing portion chamber comprises:

a first tube;

a second tube positioned interior to and spaced apart from the first tube, a first gap between the first tube and the second tube forming a first passage configured to receive a flow of cooling fluid, the second tube comprising an outer wall and an inner wall, a second gap between the outer wall and the inner wall forming a second passage isolated from the first passage, the inner wall defining a third passage in fluid communication with the first passage;

a blocking member positioned between and in contact with the first tube and the second tube, the blocking member extending along at least about 50% of a length of the second tube; and at least one orifice extending between the second passage and an exterior of the first tube.

19. The apparatus according to claim 17, wherein the at least one orifice of the at least one cooling tube positioned in the lower housing portion chamber comprises a slot extending along at least 50% of a length of the blocking member.

20. The apparatus according to claim 16, wherein the at least one cooling tube positioned in the lower housing portion chamber comprises:

a first tube;

wherein the second tube defines a third passage interior to and extending along a length of the second tube and isolated from the first and second passages, the at least one cooling tube further comprising at least one orifice extending between the third passage and an exterior of the first tube.

21. The apparatus according to claim 20, wherein the at least one orifice of the at least one cooling tube positioned in the lower housing portion chamber comprises a slot extending along at least 50% of a length of the blocking member.

22. The apparatus according to claim 1 , further comprising cooling doors positioned above the housing assembly, the cooling doors comprising a plurality of cooling tubes positioned therein, each cooling tube of the plurality of cooling tubes comprising a longitudinal axis extending orthogonal to the draw plane and orthogonal to the draw direction.

23. A method of cooling a glass ribbon, comprising:

drawing a glass ribbon from a forming body along a draw plane in a draw direction, the glass ribbon passing through a housing assembly positioned below the forming body:

at least one cooling tube positioned in the housing assembly, the at least one cooling tube comprising a longitudinal axis parallel to the draw plane and orthogonal to the draw direction, the at least one cooling tube comprising a proximal end and a distal end and at least one orifice intermediate between the proximal end and the distal end;

a thermal plate extending parallel to the draw plane and orthogonal to the draw direction and positioned between the at least one cooling tube and the draw plane; and cooling the glass ribbon by flowing a cooling gas from the at least one orifice onto the thermal plate as the glass ribbon traverses through the housing assembly.

24. The method according to claim 23, wherein the housing assembly comprises an upper housing portion and a lower housing portion, the thermal plate positioned in the upper housing portion.

25. The method according to claim 23, further comprising cooling the cooling gas with a cooling fluid flowing in the cooling tube.

26. The method according to claim 25, wherein the cooling fluid is flowed through a first passage in the cooling tube, and the cooling gas is flowed through a second passage in the cooling tube interior to the first passage.

27. The method according to claim 24, wherein the upper housing portion defines a compartment, the at least one cooling tube positioned within the compartment.

28. The method according to claim 27, further comprising extracting the cooling gas from the compartment through an exhaust tube extending from the compartment to outside the upper housing portion.

29. The method according to claim 24, wherein the lower housing portion defines a chamber through which the glass ribbon is drawn, the lower housing portion comprising at least one cooling tube extending into the chamber with a direct view to the glass ribbon, the at least one lower housing portion cooling tube comprising at least one orifice and a longitudinal axis parallel to the draw plane and orthogonal to the draw direction, the method further comprising cooling the glass ribbon by flowing cooling gas from the at least one orifice of the lower housing portion cooling tube onto the glass ribbon as the glass ribbon traverses the chamber.