WO2020086272A1

WO2020086272A1 - Glass forming apparatuses having controlled radiation heat transfer elements

Info

Publication number: WO2020086272A1
Application number: PCT/US2019/055306
Authority: WO
Inventors: Frank Coppola; Vladislav Yuryevich Golyatin; Bulent Kocatulum; Timothy Douglas LOCKWOOD
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2018-10-23
Filing date: 2019-10-09
Publication date: 2020-04-30
Anticipated expiration: 2021-04-23
Also published as: TW202023973A

Abstract

A glass forming apparatus includes a forming body comprising a draw plane that extends in a draw direction. A thermal control door is positioned below the forming body in the draw direction and spaced apart from the draw plane. An actively cooled thermal sink is positioned below the thermal control door in the draw direction. The actively cooled thermal sink is shielded from view of the root by the thermal control door.

Description

GLASS FORMING APPARATUSES HAVING CONTROLLED RADIATION HEAT

TRANSFER ELEMENTS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to US Provisional Application Serial No. 62/749,282 filed on October 23, 2018 the contents of which are relied upon and incorporated herein by reference in their entirety as if fully set forth below.

FIELD

[0002] The present specification generally relates to glass forming apparatuses used in glass manufacturing operations and, in particular, glass forming apparatuses comprising shielding members to control radiation heat transfer.

BACKGROUND

[0003] Glass substrates, such as cover glasses, glass backplanes and the like, are commonly employed in both consumer and commercial electronic devices such as LCD and LED displays, computer monitors, automated teller machines (ATMs) and the like. Various manufacturing techniques may be utilized to form molten glass into ribbons of glass which, in turn, are segmented into discrete glass substrates for incorporation into such devices. These manufacturing techniques include, for example and without limitation, down draw processes such as slot draw processes and fusion forming processes, up draw processes, and float processes.

[0004] Regardless of the process used, premature devitrification of the molten glass may lead to defects in the glass ribbon. Alternatively or additionally, deviations in the width and/or thickness of the glass ribbon may also be considered defects. Such defects may decrease manufacturing through-put and/or increase manufacturing costs as portions of the glass ribbon with such defects are discarded as waste glass.

[0005] Accordingly, a need exists for glass forming apparatus and methods for forming glass ribbons which mitigate defects in the glass ribbon.

SUMMARY

[0006] According to a first aspect Al, a glass forming apparatus may include a forming body comprising a draw plane extending from the forming body in a draw direction. A thermal control door may be spaced apart from the draw plane. At least a portion of the thermal control door may be positioned below the forming body in the draw direction. An actively cooled thermal sink may be positioned below the thermal control door in the draw direction. The actively cooled thermal sink may be shielded from a line-of-sight view of the forming body by the thermal control door.

[0007] A second aspect A2 includes the glass forming apparatus of the first aspect Al, further comprising an edge roller positioned below the actively cooled thermal sink in the draw direction.

[0008] A third aspect A3 includes the glass forming apparatus of any of the first or second aspects A1-A2, wherein a spacing between the actively cooled thermal sink and the draw plane increases with increasing distance from the forming body in the draw direction.

[0009] A fourth aspect A4 includes the glass forming apparatus of any of the first through third aspects A1-A3, wherein the actively cooled thermal sink comprises a plate cooler.

[0010] A fifth aspect A5 includes the glass forming apparatus of any of the first through fourth aspects A1-A4, wherein the actively cooled thermal sink comprises a plurality of fluid conduits.

[0011] A sixth aspect A6 includes the glass forming apparatus of any of the first through fifth aspects A1-A5, wherein the actively cooled thermal sink extends parallel to the draw plane a width greater than a width of a glass ribbon drawn from the forming body.

[0012] A seventh aspect A7 includes the glass forming apparatus of any of the first through fifth aspects A1-A5, wherein the actively cooled thermal sink extends parallel to the draw plane a width less than a width of a glass ribbon drawn from the forming body.

[0013] An eighth aspect A8 includes the glass forming apparatus of any of the first through fifth aspects A1-A5, wherein the actively cooled thermal sink comprises a plurality of sink portions arranged parallel to the draw plane, each of the plurality of sink portions comprising a width less than a width of a glass ribbon drawn from the forming body.

[0014] A ninth aspect A9 includes the glass forming apparatus of any of the first through eighth aspects A1-A8, further comprising heat transfer shields positioned along opposing sides of the actively cooled thermal sink and extending transverse to the draw plane. [0015] A tenth aspect A10 includes the glass forming apparatus of any of the first through ninth aspects A1-A9, further comprising edge directors positioned at ends of a root of the forming body and providing a contour change from converging surfaces of the forming body; and edge director shield members positioned to block a line-of-sight view of at least a portion of the edge directors to the actively cooled thermal sink.

[0016] An eleventh aspect Al l includes the glass forming apparatus of any of the first through tenth aspects A1-A10, wherein the thermal control door comprises a leading-edge portion and a cooling face extending away from the leading-edge portion at an incline away from the draw plane such that the cooling face is shielded from a line-of-sight view of the forming body.

[0017] A twelfth aspect A12 includes the glass forming apparatus of the eleventh aspect Al l, wherein the thermal control door comprises a gas inlet tube positioned to impinge cooling gas on the cooling face of the thermal control door.

[0018] A thirteenth aspect A13 includes the glass forming apparatus of the twelfth aspect A12, wherein the thermal control door further comprises an outflow vent passing through an insulation layer; and the gas inlet tube is positioned within the outflow vent.

[0019] A fourteenth aspect A14 includes the glass forming apparatus of the eleventh aspect Al l, wherein the thermal control door comprises an insulation layer that thermally insulates the cooling face from a surface of the thermal control door that faces the forming body.

[0020] A fifteenth aspect A15 includes the glass forming apparatus of any of the firth through fourteenth aspects A1-A14, further comprising a positional lock that selectively secures a position of the actively cooled thermal sink relative to the draw plane.

[0021] A sixteenth aspect A16 includes the glass forming apparatus of any of the firth through fifteenth aspects A1-A15, further comprising a positional lock that selectively secures a position of the thermal control door relative to the draw plane.

[0022] According to a seventeenth aspect A17, a glass forming apparatus may include a forming body comprising a draw plane extending below the forming body in a draw direction. A thermal control door may be spaced apart from the draw plane, wherein at least a portion of the thermal control door is positioned below the forming body in the draw direction. The thermal control door may include a leading-edge portion and a cooling face extending from the leading-edge portion at an incline away from the draw plane such that the cooling face is shielded from a line-of-sight view of the forming body by the leading-edge portion.

[0023] An eighteenth aspect A18 includes the glass forming apparatus of the seventeenth aspect A17, wherein the thermal control door comprises a gas inlet tube positioned to impinge cooling gas on the cooling face of the thermal control door.

[0024] A nineteenth aspect A19 includes the glass forming apparatus of any of the seventeenth through eighteenth aspects A17-A18, wherein the thermal control door comprises an insulation layer that thermally insulates the leading-edge portion from the cooling face.

[0025] A twentieth aspect A20 includes the glass forming apparatus of any of the seventeenth through nineteenth aspects A17-A19, further comprising a positional lock that selectively secures a position of the thermal control door relative to the draw plane.

[0026] According to a twenty-first aspect A21, a glass forming apparatus may include a forming body comprising a draw plane extending from the forming body in a draw direction. A slide gate may be spaced apart from the draw plane. An actively cooled thermal sink may be positioned below the slide gate in the draw direction. The actively cooled thermal sink may be shielded from a line-of-sight view of the forming body by the slide gate.

[0027] A twenty-second aspect A22 includes the glass forming apparatus of the twenty- first aspect A21, further comprising a thermal control door positioned below the actively cooled thermal sink in the draw direction.

[0028] A twenty-third aspect A23 includes the glass forming apparatus of the twenty- second aspect A22, wherein the thermal control door comprises a gas inlet tube positioned to impinge cooling gas on a cooling face of the thermal control door.

[0029] A twenty-fourth aspect A24 includes the glass forming apparatus of any of the twenty-first through twenty-third aspects A21-A23, further comprising a positional lock that selectively secures a position of the actively cooled thermal sink relative to the draw plane.

[0030] A twenty-fifth aspect A25 includes the glass forming apparatus of any of the twenty-first through twenty-fourth aspects A21-A24, further comprising a positional lock that selectively secures a position of the slide gate relative to the draw plane. [0031] A twenty-sixth aspect A26 includes the glass forming apparatus of any of the twenty-first through twenty-fifth aspects A21-A25, wherein a spacing between the actively cooled thermal sink and the draw plane increases with increasing distance from the forming body in the draw direction.

[0032] A twenty-seventh aspect A27 includes the glass forming apparatus of any of the twenty-first through twenty-sixth aspects A21-A26, wherein the actively cooled thermal sink comprises a plate cooler.

[0033] A twenty-eighth aspect A28 includes the glass forming apparatus of any of the twenty-first through twenty-seventh aspects A21-A27, wherein the actively cooled thermal sink comprises a plurality of fluid conduits.

[0034] A twenty-ninth aspect A29 includes the glass forming apparatus of any of the twenty-first through twenty-eighth aspects A21-A28, wherein the actively cooled thermal sink extends parallel to the draw plane a width that is greater than a width of a glass ribbon drawn from the forming body.

[0035] A thirtieth aspect A30 includes the glass forming apparatus of any of the twenty- first through twenty-ninth aspects A21-A29, wherein the actively cooled thermal sink extends parallel to the draw plane a width that is less than a width of a glass ribbon drawn from the forming body.

[0036] A thirty -first aspect A31 includes the glass forming apparatus of any of the twenty- first through thirtieth aspects A21-A30, wherein the actively cooled thermal sink comprises a plurality of sink portions arranged in a direction parallel to the draw plane, each of the plurality of sink portions comprising a width less than a width of a glass ribbon drawn from the forming body.

[0037] A thirty-second aspect A32 includes the glass forming apparatus of any of the twenty-first through thirty -first aspects A21-A31, further comprising heat transfer shields positioned along opposing sides of the actively cooled thermal sink and extending transverse to the draw plane.

[0038] A thirty-third aspect A33 includes the glass forming apparatus of any of the twenty- first through thirty-second aspects A21-A32, further comprising edge directors positioned at ends of a root of the forming body and providing a contour change from converging surfaces of the forming body; and edge director shield members positioned to block a line-of-sight view of at least a portion of the edge directors to the actively cooled thermal sink.

[0039] According to a thirty-fourth aspect A34, a method of forming a glass ribbon comprising flowing molten glass from a forming body; maintaining the molten glass at or above a liquidus temperature of the molten glass while the molten glass remains in contact with the forming body; drawing the molten glass from the forming body in a draw direction between thermal control doors and a pair of actively cooled thermal sinks positioned in the draw direction from the thermal control doors to form a glass ribbon; and reducing a temperature of the glass ribbon below the liquidus temperature at a position spaced apart from the forming body in the draw direction, wherein the pair of actively cooled thermal sinks are shielded from a line-of-sight view of the forming body by the thermal control doors.

[0040] A thirty -fifth aspect A35 includes the method of the thirty -fourth aspect A34, further comprising contacting the glass ribbon with edge rollers at a location below the pair of actively cooled thermal sinks in the draw direction.

[0041] A thirty-sixth aspect A36 includes the method of the thirty-fourth aspect A34 or the thirty-fifth aspect A35, further comprising directing a cooling fluid through the pair of actively cooled thermal sinks.

[0042] A thirty-seventh aspect A37 includes the method of any of the thirty -fourth through thirty-sixth aspects A34-A36, further comprising directing cooling gas through a plurality of gas inlet tubes of the thermal control doors, the plurality of gas inlet tubes positioned to impinge the cooling gas on a cooling face of the thermal control doors.

[0043] According to a thirty-eighth aspect A38, a method of forming a glass ribbon includes flowing molten glass from a forming body; maintaining the molten glass at or above a liquidus temperature of the molten glass while the molten glass remains in contact with the forming body; drawing the molten glass from the forming body in a draw direction between slide gates and between actively cooled thermal sinks positioned below the slide gates in the draw direction to form a glass ribbon; and reducing a temperature of the glass ribbon below the liquidus temperature at a position below the forming body in the draw direction, wherein the actively cooled thermal sinks are shielded from a line-of-sight view of the forming body by the slide gates. [0044] A thirty -ninth aspect A39 includes the method of the thirty-eighth aspect A38, further comprising contacting the glass ribbon with edge rollers at a location below the actively cooled thermal sinks in the draw direction.

[0045] A fortieth aspect A40 includes the method of either the thirty-eighth aspect A38 or the thirty ninth-aspect A39, further comprising directing a fluid through the actively cooled thermal sinks.

[0046] According to a forty-first aspect A41, a method of forming a glass includes flowing molten glass from a forming body; maintaining the molten glass at or above a liquidus temperature of the molten glass while the molten glass remains in contact with the forming body; drawing the molten glass from the forming body in a draw direction between a pair of thermal control doors to form a glass ribbon; and reducing a temperature of the glass ribbon below the liquidus temperature at a position spaced apart from the forming body in the draw direction, wherein cooling faces of the pair of thermal control doors are shielded from a line- of-sight view of the forming body by leading-edge portions of the pair of thermal control doors.

[0047] A forty-second aspect A42 includes the method of the forty-first aspect A41, further comprising directing cooling gas through a plurality of gas inlet tubes of the pair of thermal control doors, the plurality of gas inlet tubes positioned to impinge the cooling gas on the cooling faces of the pair of thermal control doors.

[0048] A forty -third aspect A43 includes the method of either the forty-first aspect A41 or the forty-second aspect A42, further comprising contacting the glass ribbon with edge rollers at a location below the pair of thermal control doors in the draw direction.

[0049] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary and intended to provide an overview or framework to understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description, explain principles and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] FIG. 1 is a schematic view of a glass forming apparatus according to one or more embodiments shown and described herein; [0051] FIG. 2 is a side sectional view of a glass forming apparatus according to one or more embodiments shown and described herein;

[0052] FIG. 3 is a side sectional view of a glass forming apparatus according to one or more embodiments shown and described herein;

[0053] FIG. 4 is a side sectional view of a glass forming apparatus according to one or more embodiments shown and described herein;

[0054] FIG. 5 is a side sectional view of one embodiment of a thermal control door according to one or more embodiments shown and described herein;

[0055] FIG. 6 is a side perspective schematic view of a thermal control door according to one or more embodiments shown and described herein;

[0056] FIG. 7 is a side perspective schematic view of a thermal control door according to one or more embodiments shown and described herein;

[0057] FIG. 8 is a side sectional view of a glass forming apparatus according to one or more embodiments shown and described herein;

[0058] FIG. 9 is a side view of a glass forming apparatus according to one or more embodiments shown and described herein;

[0059] FIG. 10 is a bottom schematic view (i.e., looking upwards along the +Z direction of the coordinate axes depicted in the figures) of a glass forming apparatus according to one or more embodiments shown and described herein;

[0060] FIG. 11 is a bottom schematic view (i.e., looking upwards along the +Z direction of the coordinate axes depicted in the figures) of a glass forming apparatus according to one or more embodiments shown and described herein; and

[0061] FIG. 12 is a bottom schematic view (i.e., looking upwards along the +Z direction of the coordinate axes depicted in the figures) of a glass forming apparatus according to one or more embodiments shown and described herein.

DETAILED DESCRIPTION [0062] Reference will now be made in detail to various embodiments 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. The components in the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the embodiments.

[0063] Numerical values, including endpoints of ranges, can be expressed herein as approximations preceded by the term "about," "approximately," or the like. In such cases, other embodiments include the particular numerical values. Regardless of whether a numerical value is expressed as an approximation, two embodiments are included in this disclosure: one expressed as an approximation, and another not expressed as an approximation. It will be further understood that an endpoint of each range is significant both in relation to another endpoint, and independently of another endpoint.

[0064] 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.

[0065] 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.

[0066] As used herein, the phrase“actively cooled thermal sink” refers to an apparatus that is positioned within an environment at an elevated temperature and that absorbs and removes thermal energy from the environment. In embodiments, the actively cooled thermal sink includes a heat transfer medium that may be controlled to modulate the rate of thermal energy that is absorbed by the actively cooled thermal sink.

[0067] As used herein,“liquidus temperature” refers to the temperature of the glass below which the glass begins to devitrify.

[0068] As used herein,“viscoelastic state” refers to a physical state of glass in which the viscosity of the glass is from about lxlO⁸ poise to about lxlO¹⁴ poise.

[0069] As used herein,“viscous state” refers to a physical state of glass in which the viscosity of the glass is less than the viscosity of the glass in the viscoelastic state, e.g., less than about lxlO⁸ poise.

[0070] As used herein,“elastic state” refers to a physical state of the glass in which the viscosity of the glass is greater than the viscosity of the glass in the viscoelastic state, e.g., greater than about lxlO¹⁴ poise.

[0071] As used herein, the singular forms“a,”“an” and“the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to“a” component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0072] Referring now to FIG. 1, a glass forming apparatus 100 is schematically depicted. As will be described in further detail herein, molten glass flows into and is drawn away from the forming body 90 on a draw plane 96 as a glass ribbon 86. As the glass ribbon 86 is drawn away from the forming body 90, the glass ribbon 86 is cooled and the viscosity of the glass ribbon 86 increases. The increase in viscosity of the glass allows the glass ribbon to sustain pulling forces applied to the glass ribbon to manage the thickness of the glass ribbon. Surfaces and components of the glass forming apparatus 100 adjacent to the forming body 90 and draw plane 96 may be used to regulate the temperature of the molten glass that flows into and travels away from the forming body 90 as the glass ribbon 86. In general, glass formed in a draw process is subjected to pulling forces that are applied by pulling rollers downstream of the forming body 90 and by the weight of the glass ribbon.

[0073] Certain glass compositions may exhibit low viscosity at the liquidus temperature. Thus, to prevent devitrification of the molten glass, particularly on surfaces of the forming body over which the molten glass flows, the temperature of the molten glass on the forming body should be maintained at a temperature above the liquidus temperature. However, in some instances, the viscosity of the molten glass as it leaves the forming body may be sufficiently low as to prevent the glass sheet from sustaining a pulling force applied by the pulling rollers. Glasses with such low viscosities may also have unwanted variations in the width and/or thickness of the glass ribbon due to low viscosity. To process such glass compositions, the temperature of the glass ribbon must be rapidly decreased over a short distance below the forming body to increase the viscosity of the glass. However, this rapid cooling must be controlled so as not to simultaneously cool molten glass flowing over surfaces of the forming body which may cause premature devitrification of the glass which disrupts the forming process and may lead to other undesirable defects in the resulting glass ribbon.

[0074] As will be discussed in greater detail below, the present disclosure is directed to glass forming apparatuses for forming a glass ribbon that comprise radiation heat transfer elements for controlling the temperature of the molten glass as it flows over a forming body and is shaped into a glass ribbon that travels away from the forming body. The heat transfer elements assist in maintaining the molten glass in contact with the forming body at a temperature above the liquidus temperature to prevent devitrification of the molten glass while the molten glass remains in contact with the forming body. The heat transfer elements also assist in rapidly cooling the glass over a short distance below the forming body as the glass travels away from the forming body to increase the viscosity of the glass.

[0075] Such temperature control may also aid in manufacturing glass ribbons at high throughput rates. Increased throughput rates correspond to an increase in the mass flow rate of molten glass and an increased thermal load that must be dissipated. The increased thermal load presented by the molten glass necessitates increased heat transfer rates from the molten glass to maintain equivalent temperatures as compared to lower throughput rates.

[0076] One embodiment of a glass forming apparatus according to the present disclosure comprises a forming body comprising a draw plane that extends below the forming body in a draw direction. The glass forming apparatus further comprises thermal control doors that are spaced apart from the draw plane. At least a portion of the thermal control doors are positioned below the forming body in the draw direction. The glass forming apparatus further comprises actively cooled thermal sinks positioned below the thermal control doors in the draw direction. The actively cooled thermal sinks are shielded from view of the root by the thermal control doors. This arrangement prevents devitrification of the glass in contact with the forming body while providing for rapid cooling of the glass below the forming body, thereby mitigating defects such as variations in the width and/or thickness of the glass ribbon.

[0077] Specifically, the glass ribbon dissipates heat to the actively cooled thermal sink and/or other cooling surfaces that are positioned in the draw direction from the thermal control doors by radiation heat transfer. Positioning the thermal control doors in the draw direction relative to the root of the forming body shields a line-of-sight view of the forming body and glass on the forming body from elements of the actively cooled thermal sinks positioned in the draw direction from the thermal control doors. Shielding the line-of-sight view between the root of the forming body and the actively cooled thermal sinks reduces heat that is dissipated from the molten glass present on the forming body. Therefore, the molten glass may be maintained at a desired high temperature at positions above the thermal control doors.

[0078] By dissipating sufficient heat from the glass into the surrounding environment, the glass can be cooled to a desired temperature within a short distance after the glass is drawn from the forming body. Rapid cooling of the glass encourages stability in the glass manufacturing operation because the glass ribbon is maintained at a viscosity sufficient to sustain a pulling force applied to the glass ribbon.

[0079] While embodiments according to the present disclosure are generally described with respect to a fusion draw process in which a glass ribbon is drawn downward from a forming body, it should be understood that elements of the glass forming apparatus described herein may be incorporated into a variety of glass forming processes, for example, slot forming, up draw, or float processes, without regard to the direction that the glass ribbon is drawn.

[0080] Referring now to FIGS. 1 and 2, a glass forming apparatus 100 for making glass articles, such as a glass ribbon 86, is schematically depicted. The glass forming apparatus 100 may generally comprise a melting vessel 15 configured to receive batch material 16 from a storage bin 18. The batch material 16 can be introduced to the melting vessel 15 by a batch delivery device 20 powered by a motor 22. An optional controller 24 may be provided to activate the motor 22 and a molten glass level probe 28 can be used to measure the glass melt level within a standpipe 30 and communicate the measured information to the controller 24.

[0081] The glass forming apparatus 100 can also comprise a fining vessel 38, such as a fining tube, coupled to the melting vessel 15 by way of a first connecting tube 36. A mixing vessel 42 is coupled to the fining vessel 38 with a second connecting tube 40. A delivery vessel 46 is coupled to the mixing vessel 42 with a delivery conduit 44. As further illustrated, a downcomer 48 is positioned to deliver molten glass from the delivery vessel 46 to a forming body inlet 50 of a forming body 90. The forming body 90 may be positioned within an enclosure 112. The enclosure 112 may extend in the draw direction 88 (i.e., the downward vertical direction corresponding to the -Z direction of the coordinate axes depicted in the figures). The forming body 90 has a trough 62 and a pair of weirs 64 (one shown in FIG. 1) bounding the trough 62. A pair of opposed vertical surfaces extend in the downward vertical direction from the pair of weirs 64 to a pair of break lines 91 (one depicted in FIG. 1). A pair of opposed converging surfaces 92 (one depicted in FIG. 1) extend in the downward vertical direction from the pair of break lines 91 and converge at a root 94 of the forming body 90. In the embodiments shown and described herein, the forming body 90 is a fusion-forming vessel. However, while FIG. 1 depicts a fusion-forming vessel as the forming body 90, it should be understood that other forming bodies are compatible with the methods and apparatuses described herein, including, without limitation, slot-draw forming bodies and the like.

[0082] In operation, molten glass from the delivery vessel 46 flows through the downcomer 48, the forming body inlet 50 and into the trough 62. Molten glass in the trough 62 flows over the pair of weirs 64 as separate streams. The molten glass flows down (-Z direction) the pair of opposed vertical surfaces extending from the pair of weirs 64 and down the pair of opposed converging surfaces 92 extending from the pair of break lines 91 before converging at the root 94. The streams of molten glass 80 join (i.e., fuse) below the root 94 to form a glass ribbon 86. The glass ribbon 86 is drawn away from the forming body 90 along a draw plane 96 in a draw direction 88. In the embodiments described herein, the draw plane 96 extends below the forming body 90 and is generally parallel to a vertical plane (i.e., parallel to the X-Z plane of the coordinate axes depicted in the figures). [0083] The molten glass 80 increases in viscosity as the molten glass 80 cools. As the molten glass cools it transitions from a viscous state through a viscoelastic state and into an elastic state. The viscosity of the molten glass once it leaves the forming body determines whether the molten glass can sustain a pulling force applied to the glass by pulling rollers (not depicted) positioned below the forming body in the draw direction 88. The pulling force applied by the pulling rollers aids in controlling the thickness of the glass ribbon as it continues to cool and its viscosity increases. Glass compositions having relatively low viscosity as the glass is drawn from the forming body 90 may result in reduced pulling force and poor process (e.g., thickness) control. For example, relatively low viscosity of the molten glass below the forming body 90 may result in undesirable variations in the width and/or thickness of the glass ribbon. Embodiments according to the present disclosure comprise elements for cooling the glass ribbon 86 by reducing the temperature of the glass ribbon 86 at positions below the forming body 90 while simultaneously reducing or mitigating cooling of the molten glass 80 in contact with the forming body 90.

[0084] Referring now to FIG. 2, one embodiment of a portion of the glass forming apparatus 100 is schematically depicted. The glass forming apparatus 100 comprises an enclosure 112 that is positioned around at least a portion of the forming body 90. The enclosure 112 assists in maintaining the temperature of the molten glass 80 while the molten glass 80 is in contact with the forming body 90. For example, the glass forming apparatus 100 may further comprise a plurality of heating elements 114 that control the temperature of the forming body 90 and the molten glass in contact with the forming body 90. In the embodiment depicted in FIG. 2, the heating elements 114 are positioned outside the enclosure 112 such that the heating elements 114 heat at least a portion of the enclosure 112 and, in turn, the enclosure 112 radiates heat towards the forming body 90 and the molten glass 80.

[0085] In the embodiment depicted in FIG. 2, the glass forming apparatus 100 comprises slide gates 120 that extend through sidewalls of the enclosure 112. The slide gates 120 are positioned opposite and spaced apart from the draw plane 96 in the +/- Y directions of the coordinate axes depicted in FIG. 2. Accordingly, the slide gates 120 are also spaced apart from one another in the +/- Y direction with the draw plane 96 disposed there between. In the embodiment depicted in FIG. 2, each of the slide gates 120 is spaced apart from the draw plane 96 by a distance Dl. The slide gates generally extend in a direction corresponding to the width of the forming body 90 (i.e., in the +/- X directions of the coordinate axes depicted in the figures). The slide gates 120 are located at a position in the draw direction 88 from the forming body 90 such that at least a portion of the slide gates 120 is positioned below the forming body 90 in the draw direction 88. Spacing is maintained between the slide gates 120 and the draw plane 96 to prevent contact between the slide gates 120 and the glass ribbon 86 drawn on the draw plane 96 from the forming body 90. The glass forming apparatus 100 may further comprise slide gate positional locks 121 that selectively secure a position of the slide gates 120 relative to the draw plane 96. In embodiments, the slide gate positional locks 121 also facilitate repositioning the slide gates 120 relative to the draw plane 96. Accordingly, the slide gates 120 are translatable relative to the draw plane 96 in a direction perpendicular to the draw plane (i.e., in the +/- Y direction of the coordinate axes depicted in the figures).

[0086] In some embodiments, the slide gates 120 may be uncooled, such that the slide gates 120 equilibrate at a temperature based on heat input from the molten glass 80 and/or the glass ribbon 86. The slide gates 120 may be made from materials that maintain their mechanical properties, insulating properties, and/or corrosion resistance at elevated temperatures, such as insulating material encapsulated by sheets of high temperature alloys (for example, Haynes 188, Haynes 214, Hastelloy, Inconel 625, Inconel 718, or the like) or insulating material encapsulated by ceramic materials such as silicon carbide. For example, in embodiments, the slide gates 120 comprise an exterior shell 122 that defines a cavity which is filled with an insulating material 123 as depicted in FIG. 2. The exterior shell 122 may be formed, for example, from a high temperature alloy or a ceramic material as noted herein. The insulating material may be formed, for example, from refractory insulation such as Duraboard®, ALTRA® KVS, or an alumina-based refractory board.

[0087] In the embodiment depicted in FIG. 2, the slide gates 120 function as thermal shields which mitigate cooling of molten glass located upstream (i.e., in the +Z direction of the coordinate axes depicted in the drawings) of the slide gates 120, such as the molten glass 80 flowing through and/or over the forming body 90.

[0088] Still referring to FIG. 2, the glass forming apparatus 100 further comprises actively cooled thermal sinks 140. The actively cooled thermal sinks 140 are positioned on opposite sides of the draw plane 96 below the slide gates 120 in the draw direction 88. The actively cooled thermal sinks 140 are spaced apart from the draw plane 96 at a distance D2 in the +/- Y direction of the coordinate axes depicted in the figures. In the embodiment depicted in FIG. 2, the distance D2 is greater than the distance Dl at which the slide gates 120 are spaced apart from the draw plane 96. This relative positioning between the actively cooled thermal sinks 140 and the slide gates 120 facilitates shielding the forming body 90 (and the molten glass 80 flowing through and/or over the forming body 90) from the actively cooled thermal sinks 140, as will be described in further detail.

[0089] In various embodiments, each of the actively cooled thermal sinks 140 comprises active cooling elements. For example, the actively cooled thermal sinks 140 may include fluid conduits 142 that are oriented parallel to a width of the draw plane 96 (i.e., in the +/- X direction of the coordinate axes depicted in the figures). A cooling fluid is directed through the fluid conduits 142. The cooling fluid maintains the temperature of the fluid conduits 142, and heat from the glass forming apparatus 100 may be dissipated into the fluid.

[0090] In some embodiments, the selection of cooling fluid and the flow rate of the cooling fluid through the fluid conduits 142 can be based on the thermal properties of the fluid as well as the amount of heat to be dissipated from the molten glass being in the glass forming apparatus 100. Examples of acceptable fluids include, for illustration and not limitation, air, water, nitrogen, water vapor, or a commercially available refrigerant. In some embodiments, the cooling fluid and the flow rate of the cooling fluid through the fluid conduits 142 may be selected such that the fluid does not undergo a phase change when passing through the fluid conduits 142. In some embodiments, the fluid may be cycled through the fluid conduits 142 and through a cooling system (not shown) to maintain the temperature of the cooling fluid in a closed loop system. In other embodiments, the cooling fluid may be discharged after flowing through the fluid conduits 142.

[0091] Referring now to FIG. 3, in some embodiments, the fluid conduits 142 of the actively cooled thermal sinks 140 may be made from a material having exterior surfaces 144 exhibiting a high emissivity, such that a substantial portion of the thermal energy emitted by the glass ribbon 86 in view of the fluid conduits 142 is absorbed by the exterior surfaces 144 of the fluid conduits 142. Fluid conduits 142 exhibiting a high emissivity reduce the portion of thermal energy reflected by the exterior surfaces 144 of the fluid conduits 142, thereby increasing the efficacy of heat absorption by the fluid conduits 142. In some embodiments, the exterior surfaces 144 of the fluid conduits 142 may have regions of high emissivity 146 and regions of low emissivity 148. In such embodiments, the regions of high emissivity 146 may be located closest to the glass ribbon 86 such as when the regions of high emissivity 146 face surfaces of the glass ribbon 86, as depicted in FIG. 3. In this embodiment the regions of low emissivity 148 face away from the glass ribbon 86 and towards surfaces of the glass forming apparatus (for example, towards the slide gates 120 and/or the enclosure 112 (not depicted)). In some embodiments, the fluid conduits 142 may be made from a corrosion resistant stainless steel having polished surfaces in the regions of low emissivity 148, and weathered or oxidized surfaces in the regions of high emissivity 146. In some embodiments, the regions of high emissivity 146 comprise a coating to provide the high emissivity. In some embodiments, the regions of high emissivity 146 have an emissivity of greater than or equal to 0.85.

[0092] Referring again to FIG. 2, in some embodiments, the glass forming apparatus 100 may further include thermal control doors 160 positioned below the actively cooled thermal sinks 140 in the draw direction 88. The thermal control doors 160 extend through the enclosure 112 and are positioned on opposite sides of the draw plane 96 from one another and spaced apart from the draw plane 96 in the +/- Y direction of the coordinate axes depicted in the figures. The thermal control doors 160 each comprise a plurality of gas inlet tubes 166 that extend through a portion of the thermal control door 160. The gas inlet tubes 166 are positioned to direct cooling gas toward a cooling face 164 of the thermal control door 160. The cooling gas that flows through the gas inlet tubes 166 cools the cooling face 164 by convective heat transfer. Specifically, the cooling gas impinges against an interior surface of the cooling face 164 (i.e., the surface of the cooling face 164 facing away from the draw plane 96) of each thermal control door 160 and heat is dissipated to the cooling gas from the hotter exterior surface of the cooling face 164 (i.e., the surface of the cooling surface facing towards the draw plane 96) of each thermal control door 160. The cooling gas may exit the thermal control door 160 through outflow vents 168 that surround each of the gas inlet tubes 166.

[0093] In some embodiments, the glass forming apparatus 100 may include thermal break members 190 positioned between the slide gates 120 and the actively cooled thermal sinks 140. The thermal break members 190 may act as radiation shields and conduction shields to limit the transfer of heat from the slide gates 120 into the actively cooled thermal sinks 140. In embodiments, thermal break members 190 may also be positioned between the actively cooled thermal sinks 140 and the thermal control doors 160 to thermally isolate the actively cooled thermal sinks 140 from the thermal control doors 160. The thermal break members 190 may be formed from, for example and without limitation, refractory insulation such as Duraboard®, ALTRA® KVS, or an alumina-based refractory board.

[0094] Still referring to FIG. 2, because the actively cooled thermal sinks 140 are relatively cooler than the glass ribbon 86, heat energy from the glass ribbon 86 drawn on the draw plane 96 is absorbed by the actively cooled thermal sinks 140 by radiation heat transfer. Because of the temperature differential between the glass ribbon 86 and the actively cooled thermal sinks 140, substantial heat from the glass ribbon 86 can be dissipated to the actively cooled thermal sinks 140. Dissipating a large amount of heat from the glass ribbon 86 at locations immediately below the root 94 of the forming body 90 may be beneficial for glass manufacturing operations in which a rapid decrease in the temperature of the glass ribbon 86 is targeted at positions in the draw direction 88 from the root 94. Further, because of the positioning of the actively cooled thermal sinks 140 relative to the slide gates 120 and the forming body 90, heat dissipation from surfaces of the forming body 90 itself or from molten glass 80 that is in contact with the forming body 90 can be minimized, thereby reducing the likelihood of devitrification defects forming in the molten glass while the molten glass is in contact with the forming body 90.

[0095] More specifically, the slide gates 120 are positioned to minimize or eliminate the line-of-sight view of the forming body 90 from the actively cooled thermal sinks 140. As depicted, dashed lines 98 indicate the extent of the line-of-sight view between the root 94 of the forming body 90 and the actively cooled thermal sinks 140 in the draw direction 88. As depicted, the dashed lines 98 contact the proximal edges of the slide gates 120 at positions closer to the draw plane 96 than the actively cooled thermal sinks 140. Accordingly, the line- of-sight view from the root 94 to the actively cooled thermal sinks 140 is interrupted by the slide gates 120. That is, the slide gates 120 shield the root 94 of the forming body 90 (and portions of the forming body 90 upstream of the root 94) from the actively cooled thermal sinks 140. Because the actively cooled thermal sinks 140 are shielded from line-of-sight view of the root 94 by the slide gates 120, the actively cooled thermal sinks 140 do not receive and dissipate a substantial amount of heat radiated from the root 94 of the forming body 90. Said differently, the slide gates 120 are positioned such that minimal heat is dissipated by radiation heat transfer from the forming body 90 or the molten glass 80 in contact with the forming body 90 to the actively cooled thermal sinks 140. [0096] By minimizing the view of the actively cooled thermal sinks 140 from the forming body 90 with the slide gates 120, the temperature of the molten glass 80 in contact with the forming body 90 can be maintained at a desired temperature above the liquidus temperature of the molten glass, thereby avoiding devitrification of the molten glass 80 while in contact with the forming body 90. However, at positions below the forming body 90 and the slide gates 120 in the draw direction 88, the actively cooled thermal sinks 140 are in view of the glass ribbon 86 drawn along the draw plane 96. As such, the actively cooled thermal sinks 140 can rapidly cool the glass ribbon 86, thereby increasing the viscosity of the glass and mitigating variations in the width and/or thickness of the glass below the forming body 90.

[0097] Additional heat can be removed from the glass ribbon 86 by the thermal control doors 160. Specifically, the thermal control doors 160 can be maintained at a temperature below the temperature of the glass ribbon 86 to allow additional heat to be dissipated from the glass ribbon 86 as it is drawn past the thermal control doors 160 on the draw plane 96. In various embodiments, the thermal control doors 160 may be utilized to control the temperature across the width of the glass ribbon 86, thereby assisting in controlling both the viscosity and thickness of the glass ribbon 86.

[0098] In the embodiment described herein, the glass forming apparatus 100 further includes a plurality of edge rollers 180 that are positioned opposite the draw plane 96 from one another. In various embodiments, the edge rollers 180 are positioned below the actively cooled thermal sinks 140 in the draw direction 88. For example, in some embodiments the edge rollers 180 are located between the actively cooled thermal sinks 140 and the thermal control doors 160. In other embodiments, the edge rollers are located below the thermal control doors 160 in the draw direction 88. The edge rollers 180 are brought into contact with the edge of the glass ribbon 86 to assist in maintaining the width of the glass ribbon 86 as it is drawn in the draw direction 88. The edge rollers 180 can also reduce the temperature of the glass ribbon 86 at locations of contact. Because the glass ribbon is brought to the viscoelastic state in proximity to the actively cooled thermal sinks 140, the edge rollers 180 closest to the root 94 of the forming body are positioned below the actively cooled thermal sinks 140 in the draw direction 88. In such embodiments, no edge rollers are positioned opposite the draw direction 88 from the actively cooled thermal sinks 140. That is, the edge rollers are not positioned between the forming body 90 and the actively cooled thermal sinks 140. [0099] Referring now to FIG. 4, another embodiment of a glass forming apparatus 200 is schematically depicted. In this embodiment the glass forming apparatus 100 comprises an enclosure 112 positioned around at least a portion of the forming body 90. The enclosure 112 assists in maintaining the temperature of the molten glass 80 while the molten glass 80 is in contact with the forming body 90. For example, the glass forming apparatus 200 may further comprise a plurality of heating elements 114 that heat the enclosure 112 to maintain heat in the forming body 90 and the molten glass 80. The heating elements 114 and the enclosure 112 may assist with managing the temperature of the molten glass 80 while the molten glass 80 is in contact with the forming body 90. In the embodiment depicted in FIG. 4, the heating elements 114 are positioned outside the enclosure 112 such that the heating elements 114 heat at least a portion of the enclosure 112 and, in turn, the enclosure radiates heat towards the forming body 90 and the molten glass 80.

[00100] In this embodiment, the glass forming apparatus 200 further comprises thermal control doors 260 that extend through the sidewalls of the enclosure 112. The thermal control doors 260 are positioned opposite and spaced apart from the draw plane 96 in the +/- Y directions of the coordinate axes depicted in FIG. 4. Accordingly, the thermal control doors 260 are also spaced apart from one another in the +/- Y direction with the draw plane 96 disposed there between. The thermal control doors 260 generally extend in a direction corresponding to the width of the forming body 90 (i.e., in the +/- X directions of the coordinate axes depicted in the figures). The thermal control doors 260 are located at a position in the draw direction 88 from the forming body 90 such that at least a portion of the thermal control doors 260 is positioned below the root 94 of the forming body 90 in the draw direction 88. Spacing is maintained between the thermal control doors 260 and the glass ribbon 86 to prevent contact between the thermal control doors 260 and the glass ribbon 86 as the glass ribbon 86 is drawn from the forming body 90.

[00101] The glass forming apparatus 200 may further comprise thermal control door positional locks 261 that selectively secure a position of the thermal control doors 160 relative to the draw plane 96. In embodiments, the thermal control door positional locks 161 also facilitate repositioning the thermal control doors 260 relative to the draw plane 96. Accordingly, the thermal control doors 260 are translatable relative to the draw plane 96 in a direction perpendicular to the draw plane (i.e., in the +/- Y direction of the coordinate axes depicted in the figures). [00102] The thermal control doors 260 each include a leading-edge portion 262, a trailing edge portion 265 located below the leading-edge portion 262 in the draw direction 88, and a cooling face 264 that extends between the leading-edge portion 262 and the trailing edge portion 265. In embodiments, the cooling face 264 may be planar, as depicted in FIG. 4. The leading-edge portion 262, the trailing edge portion 265, and the cooling face 264 may be constructed from, for example and without limitation, silicon carbide (SiC). Each of the cooling faces 264 is oriented at an incline away from the draw plane 96 such that the cooling face 264 is shielded from view of the root 94 of the forming body 90 by the leading-edge portion 262.

[00103] More specifically, the leading-edge portions 262 of the thermal control doors 260 are spaced apart from the draw plane 96 by a distance DO. The trailing edge portions 265 of the thermal control doors 260 are spaced apart from the draw plane 96 by a distance Dl which is greater than the distance DO such that the cooling faces 264 of the thermal control doors 260 are oriented at an angle with respect to the draw plane. Accordingly, the spacing between the cooling faces 264 of the thermal control doors 260 and the draw plane 96 increases in the draw direction 88.

[00104] In the embodiment depicted in FIG. 4, the cooling faces 264, the leading-edge portions 262, and the trailing edge portions 265 of the thermal control doors 260 are oriented as described herein to minimize the line-of-sight view of the forming body 90 onto the cooling faces 264. As depicted in FIG. 4, dashed lines 98 indicate the extent of the line-of- sight view from the root 94 of the forming body 90 in the draw direction 88. As depicted, the dashed lines 98 contact the proximal edges of the leading-edge portions 262 at positions closer to the draw plane 96 than the cooling faces 264. Moreover, the cooling faces 264 face away from the root 94 of the forming body 90 (i.e., the cooling faces 264 have a downward facing orientation). Accordingly, the line-of-sight view from the root 94 to the cooling faces 264 is interrupted by the leading-edge portions 262. Because the cooling faces 264 are shielded from view of the root 94 by the leading-edge portions 262 and the downward-facing orientation of the cooling faces 264, the cooling faces 264 do not receive heat (and thus do not dissipate heat) that is radiated from the root 94 of the forming body 90. That is, the leading-edge portions 262, the trailing edge portions 265, and the cooling faces 264 of the thermal control doors 260 are shaped and positioned such that minimal heat is directed by radiation heat transfer from the forming body 90 or the molten glass 80 in contact with the forming body 90 to the cooling faces 264 of the thermal control doors 260.

[00105] Specifically, the thermal control doors 260 can be positioned such that the leading- edge portion 262 of the thermal control doors 260 shields the line-of-sight view of the root 94 of the forming body 90 from the cooling faces 264 of the thermal control doors 260. In such embodiments, the thermal control doors 260 may be positioned such that minimal heat is directed from the forming body 90 or the molten glass 80 in contact with the forming body 90 to the cooling faces 264 of the thermal control doors 260. By shielding the line-of-sight view of the root 94 of the forming body 90 from the cooling faces 264, the temperature of the molten glass 80 in contact with the forming body 90 can be maintained at a temperature above which devitrification of the glass is avoided, thereby mitigating defects in the glass ribbon 86 drawn from the forming body. However, at positions below the leading-edge portions 262 of the thermal control doors 260 in the draw direction 88, the glass ribbon 86 comes into view of the cooling faces 264 of the thermal control doors 260, such that heat from the glass ribbon 86 located in such positions is dissipated into the cooling faces 264 of the thermal control doors 260, thereby rapidly cooling the glass ribbon 86 and increasing the viscosity of the glass ribbon 86 and mitigating variations in the width and/or thickness of the glass below the forming body 90.

[00106] In some embodiments, the thermal control doors 260 are located at a position in the draw direction 88 relative to the forming body 90 such that the leading-edge portion 262 is generally positioned proximate to the root 94 of the forming body 90. In some embodiments, the leading-edge portion 262 of the thermal control doors 260 are positioned below the forming body 90 in the draw direction 88 from the root 94 of the forming body 90. In some embodiments, the leading-edge portions 262 of the thermal control doors 260 are positioned above the root 94 of the forming body 90 in a direction opposite the draw direction 88 (i.e., the leading-edge portions 262 of the thermal control doors 260 are positioned upstream from the root 94 of the forming body 90). In general, the leading-edge portions 262 of the thermal control doors 260 are positioned to be in proximity to the root 94 of the forming body 90 and to the glass ribbon 86 itself to facilitate shielding the forming body 90 from the cooling faces 264 of the thermal control doors 260. However, spacing is maintained between the thermal control doors 260 and the glass ribbon 86 to prevent contact between the thermal control doors 260 and the glass ribbon 86 as the glass ribbon is drawn from the forming body 90. [00107] Still referring to FIG. 4, the thermal control doors 260 may further comprise insulation layers 263 that intersect with the leading-edge portions 262 and the interior surfaces 267 of the cooling faces 264. The insulation layers 263 extend from the leading- edge portions 262 and the interior surfaces 267 of the cooling faces 264 in directions opposite the draw plane 96 (i.e., in the +/- Y directions of the coordinate axes depicted in the figures). In embodiments, the insulation layers 263 may be, for example and without limitation, refractory insulation such as Duraboard®, ALTRA® KVS, or an alumina-based refractory board. The insulation layers prevent the extraction of heat from the forming body 90 to the interior of the thermal control doors 260.

[00108] In the embodiment depicted in FIG. 4, the thermal control doors 260 are adjustable in a direction transverse to the draw direction 88 (i.e., in the +/- Y direction of the coordinate axes depicted in the figures) to facilitate adjusting a distance between the leading-edge portion 262 of the thermal control doors 260 and the glass ribbon 86. However, as noted herein, the thermal control doors 260 are spaced from the glass ribbon 86 to minimize the risk of contact between the glass ribbon 86 and the thermal control doors 260 during the glass forming process.

[00109] While FIG. 4 schematically depicts one embodiment of the thermal control doors 260, other embodiments of thermal control doors are contemplated and possible. Referring now to FIG. 5 by way of example, another embodiment of a thermal control door 260 is schematically depicted. In this embodiment, the thermal control door 260 comprises a leading-edge portion 262, a trailing edge portion 265, and a cooling face 264 formed from silicon carbide and oriented as described herein with respect to FIG. 4. In this embodiment, the leading-edge portion 262, the trailing edge portion 265, and the cooling face 264 are coupled to a housing 290. The housing 290 may be formed from, for example and without limitation, sheets of high temperature alloys such as Haynes 188, Haynes 214, Hastelloy, Inconel 625, Inconel 718, or the like. The housing is lined with insulation layers 263. The insulation layers 263 may be, for example and without limitation, refractory insulation such as Duraboard®, ALTRA® KVS, or an alumina-based refractory board. In embodiments, the insulation layers 263 extend along the length of the housing 290 and abut an interior surface 267 of the cooling face 264 thereby preventing heat extraction from the forming body 90 to the interior of the thermal control door 260, including through the joints between the housing 290 and the leading-edge portion 262 and the trailing edge portion 265 of the thermal control door 260.

[00110] Referring collectively to FIGS. 4-7, the thermal control doors 260 each comprise a plurality of gas inlet tubes 266 that extend through a portion of the thermal control door 260. The gas inlet tubes 266 are generally arrayed in a width direction of the draw plane 96 (i.e., in the +/- X direction of the coordinate axes depicted in the figures). The gas inlet tubes 266 are positioned to direct cooling gas toward the cooling faces 264 of the thermal control doors 260. The cooling gas impinges on the interior surfaces 267 of the cooling faces 264, thereby cooling the cooling surfaces of the thermal control doors 260 by convective heat transfer. The cooling gas can exit the thermal control door 260 through outflow vents 268 that surround each of the gas inlet tubes 266.

[00111] The insulation layers 263 (FIGS. 4 and 5) of the thermal control doors 260 minimize a temperature decrease of the cooling gas on the molten glass flowing on the forming body 90. For example, the insulation layers 263 thermally isolate surfaces 269 of the thermal control doors 260 facing the forming body 90 from the cooling gas that is impinged onto the cooling face 264 of the thermal control doors 260. The insulation layers 263 allow for temperature variation in various regions of the thermal control door 260, for example, allowing the cooling face 264 to be maintained at a lower temperature than surfaces 269 of the thermal control door 260 facing the forming body 90.

[00112] In some embodiments, a transition between the leading-edge portion 262 and the cooling face 264 of the thermal control door 260 occurs at a tangent point between a curved leading-edge portion 262 and the planar cooling face 264.

[00113] Referring now to FIG. 7, in some embodiments, the transition between the leading- edge portion 262 and the cooling face 264 of the thermal control door 260 occurs at a position corresponding to the extent that backside cooling of the cooling face 264 with the cooling gas from the gas inlet tubes 166 is effective. The extent of the effect of cooling of the cooling face 264 depends on the temperature of the glass ribbon, the ambient temperatures within the glass forming apparatus, the temperature of the cooling gas, the flow rate of the cooling gas, and thermal conduction through the cooling face 264. The extent to which backside cooling of the cooling face 264 is effective for cooling a glass ribbon 86 drawn on the draw plane 96 may be relatively local and limited to locations proximate to where the cooling gas impinges against the backside of the cooling face 264. For example, FIG. 7 depicts effective cooling zones 270 that correspond to temperature differentials along the cooling face 264. An effective cooling boundary 272 represents the extent to which the effective cooling zones 270 produce a temperature differential along the cooling face 264. The effective cooling boundary 272 defines the transition between the leading-edge portion 262 and the cooling face 264 of the thermal control door 260.

[00114] Referring again to FIG. 4, as a glass ribbon 86 is drawn from the forming body 90 on the draw plane 96, the thermal control doors 260 allow heat to be dissipated from the glass ribbon 86 and into the thermal control doors 260, thereby reducing the temperature of the glass ribbon 86 at locations proximate to the thermal control doors 260. Reducing the temperature of the glass ribbon 86 at such locations aids in controlling the thickness of the glass ribbon 86 by selectively increasing the viscosity of the glass ribbon 86 as a function of the width of the glass ribbon 86. In addition, the angled orientation of the cooling faces 264 of the thermal control doors 260 shields the forming body 90 from being cooled by the cooling faces 264 while the spacing between the draw plane 96 and the thermal control doors 260 mitigates contact between the glass ribbon 86 and the thermal control doors 260, thereby reducing the risk of an uncontrolled separation of the glass ribbon through mechanical contact.

[00115] In the embodiment depicted in FIG. 4, the glass forming apparatus 200 further comprises actively cooled thermal sinks 240. The actively cooled thermal sinks 240 are positioned on opposite sides of the draw plane below the thermal control doors 260 in the draw direction 88. The actively cooled thermal sinks 240 are spaced apart from the draw plane 96 at a distance D2 in the +/- Y direction of the coordinate axes depicted in the figures. In the embodiments described herein, the distance D2 is greater than the distance DO at which the leading-edge portions 262 of the thermal control doors 260 are spaced apart from the draw plane 96. The distance D2 is also greater than the distance Dl at with the trailing edge portions 265 of the thermal control doors 260 are spaced apart from the draw plane 96.

[00116] In various embodiments, the actively cooled thermal sinks 240 comprise active cooling elements. For example, the actively cooled thermal sinks 240 may include fluid conduits 242 positioned in an orientation that generally extends parallel to a width of the glass ribbon 86 (i.e., in the +/- X direction of the coordinate axes depicted in the figures). In embodiments, the fluid conduits 242 may have regions of high emissivity and low emissivity, as described herein with respect to FIG. 3. A cooling fluid is directed through the fluid conduits 242. The cooling fluid maintains the temperature of the fluid conduits 242, and heat from the glass forming apparatus 200 may be dissipated into the fluid.

[00117] As noted herein, the selection of cooling fluid and the flow rate of the cooling fluid through the fluid conduits 242 can be based on the thermal properties of the fluid as well as the amount of heat to be dissipated from the molten glass being in the glass forming apparatus 200. Examples of acceptable fluids comprise, for illustration and not limitation, air, water, nitrogen, water vapor, or a commercially available refrigerant. In some embodiments, the cooling fluid and the flow rate of the cooling fluid through the fluid conduits 242 may be selected such that the fluid does not undergo a phase change when passing through the fluid conduits 242. In some embodiments, the fluid may be cycled through the fluid conduits 242 and through a cooling system (not shown) to maintain the temperature of the cooling fluid in a closed loop system. In other embodiments, the cooling fluid may be discharged after flowing through the fluid conduits 242.

[00118] In the embodiments described herein, the thermal control doors 260 are positioned and oriented to minimize the line-of-sight view of the forming body 90 from the actively cooled thermal sinks 240. As depicted in FIG. 4, dashed lines 98 indicate the extent of the line-of-sight view from the root 94 of the forming body 90 in the draw direction 88. As depicted, the dashed lines 98 contact the proximal edges (the leading-edge portions 262) of the thermal control doors 260 at positions closer to the draw plane 96 than the actively cooled thermal sinks 240. Accordingly, the line-of-sight view from the root 94 to the actively cooled thermal sinks 240 is interrupted by the thermal control doors 260. Because the actively cooled thermal sinks 240 are shielded from a line-of-sight view of the root 94 by the thermal control doors 260, the actively cooled thermal sinks 240 do not receive heat (and thus do not dissipate heat) that is radiated from the root 94 of the forming body 90. That is, the leading- edge portions 262 of the thermal control doors 260 are positioned such that minimal heat is directed by radiation heat transfer from the forming body 90, or the molten glass 80 in contact with the forming body 90, to the actively cooled thermal sinks 240. [00119] In some embodiments, the actively cooled thermal sinks 240 each comprise a plurality of fluid conduits 242, as depicted in FIG. 4. In these embodiments, the plurality of actively cooled thermal sinks 240 are arranged in the draw direction 88 from one another. In such embodiments, the plurality of fluid conduits 242 may be oriented at an incline away from the glass ribbon 86. That is, the plurality of fluid conduits 242 are spaced with increasing distance from the draw plane 96 in the draw direction 88.

[00120] In the embodiment of the glass forming apparatus 200 depicted in FIG. 4, the temperature of the molten glass 80 in contact with the forming body 90 can be maintained at a temperature above which devitrification of the molten glass does not occur by shielding the root 94 of the forming body 90 from view with the actively cooled thermal sinks 240, thereby mitigating defects in the glass ribbon 86 drawn from the forming body. However, at positions below the leading-edge portions 262 of the thermal control doors 260 in the draw direction 88, the actively cooled thermal sinks 240 are not shielded from view of the glass ribbon 86. Thus, portions of the glass ribbon 86 located below the leading-edge portions 262 of the thermal control doors 260 in the draw direction dissipate heat into the actively cooled thermal sinks 240, allowing for the glass ribbon 86 to be rapidly cooled thereby increasing the viscosity of the glass ribbon 86 and mitigating variations in the width and/or thickness of the glass below the forming body 90.

[00121] Still referring to FIG. 4, the glass forming apparatus 200 also includes a plurality of edge rollers 280 positioned opposite the draw plane 96 from one another. In various embodiments, the edge rollers 280 are positioned below the actively cooled thermal sinks 240 in the draw direction 88. The edge rollers 280 are brought into contact with the edge of the glass ribbon 86 to assist in maintaining the width of the glass ribbon 86 as it is drawn in the draw direction 88. The edge rollers 280 can also reduce the temperature of the glass ribbon 86 at locations of contact. Because the glass ribbon is brought to the viscoelastic state in proximity to the actively cooled thermal sinks 240, the edge rollers 280 closest to the root 94 of the forming body are positioned below the actively cooled thermal sinks in the draw direction 88. In such embodiments, no edge rollers are positioned opposite the draw direction 88 from the actively cooled thermal sinks 240. That is, the edge rollers are not positioned between the forming body 90 and the actively cooled thermal sinks 240. [00122] In some embodiments, the glass forming apparatus 200 may further include thermal break members 291 positioned between the thermal control doors 260 and the actively cooled thermal sinks 240. The thermal break members 291 may act as radiation shields and conduction shields to limit the transfer of heat from the thermal control doors 260 into the actively cooled thermal sinks 240. In embodiments, thermal break members 291 may also be positioned between the actively cooled thermal sinks 240 and the edge rollers 280 to thermally isolate the actively cooled thermal sinks 240 from the edge rollers 280. The thermal break members 291 may be formed from, for example and without limitation, refractory insulation such as Duraboard®, ALTRA® KVS, or an alumina-based refractory board.

[00123] Referring now to FIG. 8, another embodiment of the glass forming apparatus 300 is schematically depicted. This embodiment of the glass forming apparatus 300 is similar to the embodiment discussed hereinabove with respect to FIG. 4. That is, the glass forming apparatus 300 includes a forming body 90 and thermal control doors 260 as described herein with respect to FIGS. 4-7. This embodiment of the glass forming apparatus 300 also includes actively cooled thermal sinks 240, as described herein with respect to FIG. 4. However, in this embodiment, the actively cooled thermal sinks 240 each comprise a plate cooler 350 through which a cooling fluid can be directed. The cooling fluid may be as described herein with respect to FIGS. 2 and 4. The cooling fluid controls the temperature of the respective plate cooler 350, and heat from the glass ribbon 86 drawn on the draw plane 96 can be dissipated into the cooling fluid.

[00124] As noted hereinabove with respect to FIG. 4, the actively cooled thermal sinks 240 are positioned on opposite sides of the draw plane 96 below the thermal control doors 260 in the draw direction 88. The actively cooled thermal sinks 240 are spaced apart from the draw plane 96 at a distance D2 in the +/- Y direction of the coordinate axes depicted in the figures. In the embodiment depicted in FIG. 8, the distance D2 is greater than the distance DO at which the leading-edge portions 262 of the thermal control doors 260 are spaced apart from the draw plane 96. The distance D2 is also greater than the distance Dl at which the trailing edge portions 265 of the thermal control doors 260 are spaced apart from the draw plane 96.

[00125] As previously described, the leading-edge portions 262 of the thermal control doors 260 shield the plate coolers 350 of the actively cooled thermal sinks 240 from line-of-sight view with the root 94 of the forming body 90. As depicted in FIG. 8, dashed lines 98 indicates the extent of the line-of-sight view from the root 94 of the forming body 90 in the draw direction 88. As depicted, the dashed lines 98 contact the proximal edges (the leading- edge portions 262) of the thermal control doors 260 at positions closer to the draw plane 96 than the plate coolers 350. Accordingly, the line-of-sight view from the root 94 to the plate coolers 350 is interrupted by the thermal control doors 260. Because the plate coolers 350 of the actively cooled thermal sinks 240 are shielded from line-of-sight view of the root 94 by the thermal control doors 260, the plate coolers 350 do not receive heat (a therefore do not dissipate heat) that is radiated from the root 94 of the forming body 90. That is, the thermal control doors 260 are positioned such that minimal heat is directed by radiation heat transfer from the forming body 90 or the molten glass 80 in contact with the forming body 90 to the plate coolers 350.

[00126] The plate coolers 350 of the actively cooled thermal sinks 240 may be oriented at an incline away from the glass ribbon 86 (e.g., away from draw plane 96) such that the distance between the plate coolers 350 of the actively cooled thermal sinks 240 and the draw plane 96 increases with increasing distance from the forming body 90 in the draw direction 88, as depicted in FIG. 8. As such, the faces 351 of the plate coolers 350 of the actively cooled thermal sinks 240 have a downward facing orientation, such that the faces 351 face away from the forming body 90.

[00127] By shielding the root 94 of the forming body 90 from line-of-sight view with the actively cooled thermal sinks 240, the temperature of the molten glass 80 that is in contact with the forming body 90 can be maintained at a temperature above which devitrification of the glass is avoided, thereby mitigating defects in the glass ribbon 86 drawn from the forming body 90. However, at positions below the leading-edge portions 262 of the thermal control doors 260 in the draw direction 88, the plate coolers 350 of the actively cooled thermal sinks 240 are not shielded from view of the glass ribbon 86. Thus, portions of the glass ribbon 86 located below the leading-edge portions 262 of the thermal control doors 260 in the draw direction dissipate heat into the plate coolers 350 of the actively cooled thermal sinks 240, allowing for the glass ribbon 86 to be rapidly cooled thereby increasing the viscosity of the glass ribbon 86 and mitigating variations in the width and/or thickness of the glass ribbon.

[00128] Referring now to FIG. 9, a cross section of the glass forming apparatuses 200, 300 of FIGS. 4 and 8 is schematically depicted along a vertical plane (i.e., a plane parallel to the X-Z plane of the coordinate axes depicted in the figures) parallel to the draw plane 96. Specifically, FIG. 9 schematically depicts the orientation of a thermal control door 260 and an actively cooled thermal sink 240 relative to the root 94 of the forming body 90.

[00129] As depicted in FIG. 9, the forming body 90 may further include edge directors 398 positioned at the ends of the converging surfaces 92 of the forming body 90. The edge directors 398 have a contour change from the converging surfaces 92 of the forming body 90 and assist in guiding molten glass as it flows over the converging surfaces 92 towards the root 94. The edge directors 398 generally extend from the root 94 of the forming body 90 at opposite ends of the converging surfaces 392 in the +/- X directions of the coordinate axes depicted in FIG. 9. In embodiments, the glass forming apparatus 200, 300 may further comprise heaters (not depicted) to heat the edge directors 398, thereby preventing devitrification of the molten glass flowing over the edge directors 398.

[00130] Given the proximity of the thermal control doors 260 and the actively cooled thermal sinks 240 to the edge directors 398, there is a risk that the edge directors 398 and/or molten glass flowing over the edge directors may be cooled by the thermal control doors 260 and/or the actively cooled thermal sinks, thereby causing devitrification of the molten glass and defects in the glass ribbon drawn on the draw plane 96. Accordingly, in some embodiments, the glass forming apparatus 200, 300 may further include thermal shields to thermally isolate the edge directors 398 from the thermal control doors 260 and/or the actively cooled thermal sinks 240 to mitigate this risk.

[00131] For example, in some embodiments, the glass forming apparatus 200, 300 also comprises edge director shield members 410 positioned to at least partially block the view of the edge directors 398 on the actively cooled thermal sinks 240 and/or thermal control doors 260. In embodiments, the edge director shield members 410 are positioned between the edge directors 398 and both the thermal control doors 260 and the actively cooled thermal sinks 240. The edge director shield members 410 act as radiation shields to reduce the heat transferred from the molten glass 80 flowing over the edge directors 398 to the actively cooled thermal sinks 240 and the thermal control doors 260. The edge director shield members 410 may be made from a material suitable for operation at elevated temperatures, for example temperatures in excess of 700°C, for example in excess of 800°C, such as in excess of 900°C. For example, in some embodiments, the edge director shield members 410 may be formed from, for example and without limitation, refractory insulation such as Duraboard®, ALTRA® KVS, or an alumina-based refractory board.

[00132] In embodiments, the glass forming apparatus 200, 300 also comprises heat transfer shields 420 positioned along opposing sides of the actively cooled thermal sinks 240. The heat transfer shields 420 are oriented transverse to the draw plane 96 and extend in the draw direction 88 along the actively cooled thermal sinks 240. The heat transfer shields 420 may shield the edge directors and/or other components of the glass forming apparatus 200, 300 from the actively cooled thermal sinks 240 to reduce heat transferred to the actively cooled thermal sinks 240.

[00133] While reference is made herein to the glass forming apparatus 200, 300 having thermal control doors 260 and actively cooled thermal sinks 240, it should be understood that various elements, such as the edge director shield members 410 and the heat transfer shields 420, may be incorporated into embodiments of the glass forming apparatus with various other configurations of elements.

[00134] Referring now to FIGS. 4 and 10-11, embodiments of the glass forming apparatuses 200 according to the present disclosure may comprise a variety of configurations of actively cooled thermal sinks, such as actively cooled thermal sinks 340, 440, 540 depicted in FIGS. 10-12, to provide cooling at various positions along a width 87 of the glass ribbon 86 that is drawn away from the forming body 90.

[00135] Referring now to FIG. 10 by way of example, a bottom schematic view of a glass forming apparatus 200 (i.e., looking upwards along the +Z direction of the coordinate axes depicted in the figures) with actively cooled thermal sinks 340 is depicted. In this embodiment, the actively cooled thermal sinks 340 each comprise a fluid conduit 342 that extends parallel to the width 87 of the glass ribbon to a length that is greater than the width 87 of the glass ribbon 86. Such a configuration of the fluid conduit 342 can provide for the dissipation of heat along the entire width of the glass ribbon 86.

[00136] Referring now to FIG. 11, a bottom schematic view of a glass forming apparatus 200 (i.e., looking upwards along the +Z direction of the coordinate axes depicted in the figures) with another embodiment of actively cooled thermal sinks 440 is depicted. In this embodiment, the actively cooled thermal sinks 440 each comprise a fluid conduit 442 that extends parallel to the glass ribbon 86 along a length less than the width 87 of the glass ribbon 86. In such embodiments, the actively cooled thermal sinks 440 can provide cooling of the glass ribbon 86 between the edges 89 of the glass ribbon 86. Such an embodiment may also reduce cooling at positions proximate to edge directors of the forming body (as shown in FIG. 9). The glass forming apparatus 300 may further comprise sink positional locks 441 so that the position of the actively cooled thermal sink 440 can be adjusted and selectively secured relative to the draw plane 96.

[00137] Referring now to FIG. 12, a bottom schematic view of a glass forming apparatus 200 (i.e., looking upwards along the +Z direction of the coordinate axes depicted in the figures) with actively cooled thermal sinks 540 is depicted. In this embodiment, the actively cooled thermal sinks 540 comprise a plurality of fluid conduits 542, 544, 546 arranged across the width 87 of the glass ribbon 86. Each fluid conduit 542, 544, 546 extends parallel to the glass ribbon 86 and each has a length that is less than the width 87 of the glass ribbon 86. Cooling fluid flow rates through the fluid conduits 542, 544, 546 may be controlled such that thermal energy dissipated from the glass ribbon 86 and into the actively cooled thermal sinks 540 is either uniform or non-uniform across the width 87 of the glass ribbon 86. Alternatively or additionally, the relative positioning between the glass ribbon 86 and the fluid conduits 542, 544, 546 may be non-uniform such that the thermal energy dissipated from the glass ribbon 86 and into the actively cooled thermal sinks 540 is non-uniform across the width 87 of the glass ribbon 86.

[00138] It should now be understood that glass forming apparatuses according to the present disclosure comprise actively cooled thermal sinks positioned below the root of the forming body. The actively cooled thermal sinks are maintained at temperatures below the temperature of the glass ribbon such that heat can be dissipated from the glass ribbon to the actively cooled thermal sinks. The root of the forming body is shielded from view of the actively cooled thermal sinks to prevent cooling of the molten glass that is in contact with the forming body to prevent devitrification of the molten glass while the molten glass is in contact with the forming body, thereby mitigating the formation of defects in the glass ribbon drawn from the glass forming body.

[00139] It will be apparent to those skilled in the art that various modifications and alterations can be made to the present disclosure without departing from the scope and spirit 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

CLAIMS What is claimed is:

1. A glass forming apparatus, comprising:

a forming body comprising a draw plane extending from the forming body in a draw direction;

a thermal control door spaced apart from the draw plane, at least a portion of the thermal control door positioned below the forming body in the draw direction; and

an actively cooled thermal sink positioned below the thermal control door in the draw direction, the actively cooled thermal sink shielded from a line-of-sight view of the forming body by the thermal control door.

2. The glass forming apparatus of claim 1, further comprising an edge roller positioned below the actively cooled thermal sink in the draw direction.

3. The glass forming apparatus of claim 1 or claim 2, wherein a spacing between the actively cooled thermal sink and the draw plane increases with increasing distance from the forming body in the draw direction.

4. The glass forming apparatus of any one of claims 1 to 3, wherein the actively cooled thermal sink comprises a plate cooler.

5. The glass forming apparatus of any one of claims 1 to 3, wherein the actively cooled thermal sink comprises a plurality of fluid conduits.

6. The glass forming apparatus of any one of claims 1 to 5, wherein the actively cooled thermal sink extends parallel to the draw plane a width greater than a width of a glass ribbon drawn from the forming body.

7. The glass forming apparatus of any one of claims 1 to 5, wherein the actively cooled thermal sink extends parallel to the draw plane a width less than a width of a glass ribbon drawn from the forming body.

8. The glass forming apparatus of any one of claims 1 to 5, wherein the actively cooled thermal sink comprises a plurality of sink portions arranged parallel to the draw plane, each of the plurality of sink portions comprising a width less than a width of a glass ribbon drawn from the forming body.

9. The glass forming apparatus of any one of claims 1 to 8, further comprising heat transfer shields positioned along opposing sides of the actively cooled thermal sink and extending transverse to the draw plane.

10. The glass forming apparatus of any one of claims 1 to 9, further comprising:

edge directors positioned at ends of a root of the forming body and providing a contour change from converging surfaces of the forming body; and

edge director shield members positioned to block a line-of-sight view of at least a portion of the edge directors to the actively cooled thermal sink.

11. The glass forming apparatus of any one of claims 1 to 10, wherein the thermal control door comprises a leading-edge portion and a cooling face extending away from the leading- edge portion at an incline away from the draw plane such that the cooling face is shielded from a line-of-sight view of the forming body.

12. The glass forming apparatus of claim 11, wherein the thermal control door comprises a gas inlet tube positioned to impinge cooling gas on the cooling face of the thermal control door.

13. The glass forming apparatus of claim 12, wherein:

the thermal control door further comprises an outflow vent passing through an insulation layer; and

the gas inlet tube is positioned within the outflow vent.

14. The glass forming apparatus of claim 11, wherein the thermal control door comprises an insulation layer that thermally insulates the cooling face from a surface of the thermal control door that faces the forming body.

15. The glass forming apparatus of any one of claims 1 to 14, further comprising a positional lock that selectively secures a position of the actively cooled thermal sink relative to the draw plane.

16. The glass forming apparatus of any one of claims 1 to 15, further comprising a positional lock that selectively secures a position of the thermal control door relative to the draw plane.

17. A glass forming apparatus, comprising:

a forming body comprising a draw plane extending below the forming body in a draw direction; and

a thermal control door spaced apart from the draw plane, at least a portion of the thermal control door positioned below the forming body in the draw direction, the thermal control door comprising:

a leading-edge portion; and

a cooling face extending from the leading-edge portion at an incline away from the draw plane such that the cooling face is shielded from a line-of-sight view of the forming body by the leading-edge portion.

18. The glass forming apparatus of claim 17, wherein the thermal control door comprises a gas inlet tube positioned to impinge cooling gas on the cooling face of the thermal control door.

19. The glass forming apparatus of claim 17 or claim 18, wherein the thermal control door comprises an insulation layer that thermally insulates the leading-edge portion from the cooling face.

20. The glass forming apparatus of any one of claims 17 to 19, further comprising a positional lock that selectively secures a position of the thermal control door relative to the draw plane.

21. A glass forming apparatus, comprising: a forming body comprising a draw plane extending from the forming body in a draw direction;

a slide gate spaced apart from the draw plane; and

an actively cooled thermal sink positioned below the slide gate in the draw direction, the actively cooled thermal sink shielded from a line-of-sight view of the forming body by the slide gate.

22. The glass forming apparatus of claim 21, further comprising a thermal control door positioned below the actively cooled thermal sink in the draw direction.

23. The glass forming apparatus of claim 22, wherein the thermal control door comprises a gas inlet tube positioned to impinge cooling gas on a cooling face of the thermal control door.

24. The glass forming apparatus of any one of claims 21 to 23, further comprising a positional lock that selectively secures a position of the actively cooled thermal sink relative to the draw plane.

25. The glass forming apparatus of any one of claims 21 to 24, further comprising a positional lock that selectively secures a position of the slide gate relative to the draw plane.

26. The glass forming apparatus of any one of claims 21 to 25, wherein a spacing between the actively cooled thermal sink and the draw plane increases with increasing distance from the forming body in the draw direction.

27. The glass forming apparatus of any one of claims 21 to 26, wherein the actively cooled thermal sink comprises a plate cooler.

28. The glass forming apparatus of any one of claims 21 to 26, wherein the actively cooled thermal sink comprises a plurality of fluid conduits.

29. The glass forming apparatus of any one of claims 21 to 28, wherein the actively cooled thermal sink extends parallel to the draw plane a width that is greater than a width of a glass ribbon drawn from the forming body.

30. The glass forming apparatus of any one of claims 21 to 28, wherein the actively cooled thermal sink extends parallel to the draw plane a width that is less than a width of a glass ribbon drawn from the forming body.

31. The glass forming apparatus of any one of claims 21 to 28, wherein the actively cooled thermal sink comprises a plurality of sink portions arranged in a direction parallel to the draw plane, each of the plurality of sink portions comprising a width less than a width of a glass ribbon drawn from the forming body.

32. The glass forming apparatus of any one of claims 21 to 31, further comprising heat transfer shields positioned along opposing sides of the actively cooled thermal sink and extending transverse to the draw plane.

33. The glass forming apparatus of any one of claims 21 to 32, further comprising:

34. A method of forming a glass ribbon comprising:

flowing molten glass from a forming body;

maintaining the molten glass at or above a liquidus temperature of the molten glass while the molten glass remains in contact with the forming body;

drawing the molten glass from the forming body in a draw direction between thermal control doors and a pair of actively cooled thermal sinks positioned in the draw direction from the thermal control doors to form a glass ribbon; and

reducing a temperature of the glass ribbon below the liquidus temperature at a position spaced apart from the forming body in the draw direction, the pair of actively cooled thermal sinks shielded from a line-of-sight view of the forming body by the thermal control doors.

35. The method of claim 34, further comprising contacting the glass ribbon with edge rollers at a location below the pair of actively cooled thermal sinks in the draw direction.

36. The method of claim 34 or claim 35, further comprising directing a cooling fluid through the pair of actively cooled thermal sinks.

37. The method of any one of claims 34 to 36, further comprising directing cooling gas through a plurality of gas inlet tubes of the thermal control doors, the plurality of gas inlet tubes positioned to impinge the cooling gas on a cooling face of the thermal control doors.

38. A method of forming a glass ribbon comprising:

flowing molten glass from a forming body;

drawing the molten glass from the forming body in a draw direction between slide gates and between actively cooled thermal sinks positioned below the slide gates in the draw direction to form a glass ribbon; and

reducing a temperature of the glass ribbon below the liquidus temperature at a position below the forming body in the draw direction, the actively cooled thermal sinks shielded from a line-of-sight view of the forming body by the slide gates.

39. The method of claim 38, further comprising contacting the glass ribbon with edge rollers at a location below the actively cooled thermal sinks in the draw direction.

40. The method of claim 38 or claim 39, further comprising directing a fluid through the actively cooled thermal sinks.

41. A method of forming a glass comprising:

flowing molten glass from a forming body; maintaining the molten glass at or above a liquidus temperature of the molten glass while the molten glass remains in contact with the forming body;

drawing the molten glass from the forming body in a draw direction between a pair of thermal control doors to form a glass ribbon; and

reducing a temperature of the glass ribbon below the liquidus temperature at a position spaced apart from the forming body in the draw direction, cooling faces of the pair of thermal control doors shielded from a line-of-sight view of the forming body by leading- edge portions of the pair of thermal control doors.

42. The method of claim 41, further comprising directing cooling gas through a plurality of gas inlet tubes of the pair of thermal control doors, the plurality of gas inlet tubes positioned to impinge the cooling gas on the cooling faces of the pair of thermal control doors.

43. The method of claim 41 or claim 42, further comprising contacting the glass ribbon with edge rollers at a location below the pair of thermal control doors in the draw direction.