Glass forming roll with molded pockets for thermal management of glass ribbon

Abstract

A forming apparatus is disclosed that includes a pair of opposing forming rolls having a molding pocket formed in a cylindrical glass forming surface of at least one of the pair of opposing forming rolls. The molding pocket includes a plurality of distinct molding features formed in the molding pocket and extending from a base of the molding pocket, the base of the molding pocket having a depth measured from the cylindrical glass forming surface of one of the pair of opposing forming rolls. The plurality of distinct molding features in the molding pocket increase heat extraction from the formed glass ribbon.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 63 / 428,178, filed November 28, 2022, the contents of which are incorporated by reference in their entirety and are hereby incorporated by reference.

[0002] FIELD OF THE INVENTION The present disclosure relates generally to glass manufacturing apparatus for forming glass ribbons, and more particularly to glass manufacturing apparatus including forming rolls with features for enhancing heat extraction from the glass ribbon. [Background technology]

[0003] Glass manufacturing equipment can include a variety of individual components for melting, processing, and shaping glass. To form glass articles with non-uniform thickness, such as glass sheets with non-uniform thickness, glass manufacturing equipment can incorporate forming rolls to form a continuous ribbon of glass with a non-uniform thickness profile as produced. This approach can significantly improve material utilization without introducing defects that can occur in other glass manufacturing processes, such as glass bonding processes.

[0004] However, within the glass ribbon produced by such processes, there may be temperature differences where thicker regions experience significantly higher temperatures than thinner regions of the glass ribbon. Furthermore, using existing roll-forming techniques, there may not be enough time after forming and before the glass solidifies to address this temperature difference. Furthermore, addressing the thick-to-thin temperature difference as early as possible in the process may improve the quality of the resulting article, for example, improving the ability to produce glass ribbons with lower stress and less warpage.

[0005] Therefore, there is a need for alternative designs for roll-forming glass manufacturing equipment components that address temperature differences in glass ribbons having non-uniform thickness. Summary of the Invention

[0006] According to a first aspect, an apparatus for roll-forming a glass ribbon or glass ceramic ribbon includes a molten glass delivery device and a pair of opposing upper forming rolls, each upper forming roll having a pair of circular end faces and a cylindrical glass forming surface extending between the pair of circular end faces, the pair of opposing upper forming rolls defining a glass forming gap between the cylindrical glass forming surfaces, the glass forming gap being located below the molten glass delivery device and positioned to receive a flow of molten glass from the molten glass delivery device such that the flow of molten glass is thinned between the pair of opposing upper forming rolls to form a molded glass ribbon, and The method includes a pair of opposing upper forming rolls, each upper forming roll having a molding pocket formed in a cylindrical glass forming surface of the at least one upper forming roll, the molding pocket having a plurality of distinct molding features extending from a base of the molding pocket, the base of the molding pocket having a depth evaluated from the cylindrical glass forming surface of at least 0.5 mm, and a pair of opposing lower rolls defining a glass sizing gap therebetween, the glass sizing gap being located below the glass forming gap and configured to receive a molded glass ribbon such that the molded glass ribbon is reshaped to a target thickness by the pair of opposing lower rolls.

[0007] A second embodiment includes the apparatus of the first embodiment, wherein the plurality of distinct molding features comprises a plurality of lands extending from a base of the molding pocket, the lands extending continuously circumferentially around at least one upper molding roll and spaced apart by a plurality of grooves defined between each of the lands.

[0008] A third aspect includes the device of any of the preceding aspects, wherein the plurality of lands are equally spaced apart by a plurality of grooves.

[0009] A fourth aspect includes the apparatus of any of the preceding aspects, wherein the cylindrical glass forming surface of a first upper forming roll of the pair of opposing upper forming rolls includes a first mold forming pocket with a plurality of first lands extending from a base of the first mold forming pocket and spaced apart by a plurality of first grooves defined between the plurality of first lands; and the cylindrical glass forming surface of a second upper forming roll of the pair of opposing upper forming rolls includes a second mold forming pocket with a plurality of second lands extending from a base of the second mold forming pocket and spaced apart by a plurality of second grooves defined between the plurality of second lands.

[0010] A fifth aspect includes the apparatus of the fourth aspect, wherein the base of the first molded pocket comprises a plurality of first base segments, each of the plurality of first lands being positioned between a pair of the plurality of first base segments and each of the plurality of first lands extending radially toward one of the plurality of second grooves so as to face one of the second base segments of the second molded pocket; and the base of the second molded pocket comprises a plurality of second base segments, each of the plurality of second lands being positioned between a pair of the plurality of second base segments and each of the plurality of second lands extending radially toward one of the plurality of first grooves so as to face one of the first base segments of the first molded pocket.

[0011] A sixth aspect includes the device of the fourth or fifth aspect, wherein each of the plurality of first lands and each of the plurality of second lands comprises a land surface and a pair of side surfaces on either side of the land surface, each of the pair of side surfaces being oriented at a draft angle of less than 90° relative to the base of the first molded pocket or the second molded pocket associated with each of the pair of side surfaces.

[0012] A seventh aspect includes the device of any one of the fourth to sixth aspects, wherein the draft angle of each of the plurality of first lands is equal to the draft angle of each of the plurality of second lands.

[0013] An eighth aspect includes the device of any of the fourth to seventh aspects, wherein the plurality of first lands and the plurality of second lands each have a height dimension equal to the depth of the respective molded pocket, the height dimension of the plurality of first lands being measured between the land surface of the plurality of first lands and the base of the first molded pocket, and the height dimension of the plurality of second lands being measured between the land surface of the plurality of second lands and the base of the second molded pocket.

[0014] A ninth aspect includes the device of any of the fourth to eighth aspects, wherein the land surface of each of the plurality of first lands is coaxial with a first upper forming roll of a pair of opposing upper forming rolls, and the land surface of each of the plurality of second lands is coaxial with a second upper forming roll of the pair of opposing upper forming rolls.

[0015] A tenth aspect includes the device of any of the fourth to ninth aspects, wherein each of the plurality of first base segments is coaxial with a first upper forming roll of a pair of opposing upper forming rolls, and each of the plurality of second base segments is coaxial with a second upper forming roll of the pair of opposing upper forming rolls.

[0016] An eleventh aspect includes the device of any of the fourth to tenth aspects, wherein the first lands of the first molded pocket are equally spaced apart by a plurality of first base segments, and the second lands of the second molded pocket are equally spaced apart by a plurality of second base segments.

[0017] A twelfth aspect includes the device of any one of the fourth to eleventh aspects, wherein the number of first lands in the first mold forming pocket is greater than the number of second lands in the second mold forming pocket.

[0018] A thirteenth aspect includes the device of any one of the fourth to twelfth aspects, wherein the number of first lands in the first molded pocket is equal to the number of second grooves in the second molded pocket.

[0019] A fourteenth aspect includes the apparatus of any of the first to third aspects, wherein the cylindrical glass forming surface of a first upper forming roll of a pair of opposing upper forming rolls includes a first mold forming pocket, and the cylindrical glass forming surface of a second upper forming roll of the pair of opposing upper forming rolls includes a second mold forming pocket, and the plurality of lands of the first mold forming pocket include a plurality of first lands extending from a base of the first mold forming pocket, the plurality of first lands being spaced apart by a plurality of first grooves defined between the plurality of first lands, and the plurality of lands of the second mold forming pocket include a plurality of second lands extending from a base of the second mold forming pocket, the plurality of second lands being spaced apart by a plurality of second grooves defined between the plurality of second lands. The base of the first molding pocket comprises a plurality of first base segments, and each first land of the plurality of first lands is positioned between pairs of the plurality of first base segments; the base of the second molding pocket comprises a plurality of second base segments, and each second land of the plurality of second lands is positioned between pairs of the plurality of second base segments; each of the plurality of first lands of the first molding pocket is raised from the cylindrical glass forming surface of a first upper forming roll of a pair of opposing upper forming rolls; and each of the plurality of second lands of the second molding pocket is raised from the cylindrical glass forming surface of a second upper forming roll of a pair of opposing upper forming rolls.

[0020] A fifteenth aspect includes the engine of the fourteenth aspect, wherein each of the plurality of first base segments and each of the plurality of second base segments is at least partially curved when evaluated in a plane extending through a first axis of rotation of a first upper forming roll of a pair of opposing upper forming rolls and a second axis of rotation of a second upper forming roll of the pair of opposing upper forming rolls.

[0021] A sixteenth aspect includes the apparatus of the fourteenth or fifteenth aspects, wherein each of the plurality of first lands of the first molded pocket extends radially toward one of the plurality of second base segments of the second molded pocket, and each of the plurality of second lands of the second molded pocket extends radially toward one of the plurality of first base segments of the first molded pocket.

[0022] A seventeenth aspect includes the device of any of the fourteenth to sixteenth aspects, wherein each of the plurality of first lands extends radially beyond the centerline of the glass forming gap, each of the plurality of second lands extends radially beyond the centerline of the glass forming gap, each of the plurality of first lands is raised from the plurality of second lands of a second upper forming roll of the pair of opposing upper forming rolls, and each of the plurality of second lands is raised from the plurality of first lands of a first upper forming roll of the pair of opposing upper forming rolls.

[0023] An 18th aspect includes the device of any of the 14th to 17th aspects, wherein the plurality of first grooves defined in the first molded pocket include an innermost groove, an outermost groove, and a plurality of central grooves, and the plurality of second lands in the second molded pocket include an innermost land extending radially to the innermost groove, an outermost land extending radially to the outermost groove, and a plurality of central lands extending radially to each of the plurality of central grooves.

[0024] A nineteenth aspect includes the apparatus of any of the fourteenth to eighteenth aspects, wherein each of the plurality of first lands has a first land surface and a height dimension measured between the first land surface and a base of the first mold forming pocket, the height dimension of each of the plurality of first lands being greater than the sum of the depth and the glass forming gap, such that each of the plurality of first lands is raised from the cylindrical glass forming surface of the second upper forming roll of the pair of opposing upper forming rolls; and each of the plurality of second lands has a second land surface and a height dimension measured between the second land surface and a base of the second mold forming pocket, such that each of the plurality of second lands is raised from the cylindrical glass forming surface of the first upper forming roll of the pair of opposing upper forming rolls, the height dimension of each of the plurality of second lands being greater than the sum of the depth and the glass forming gap.

[0025] A twentieth aspect includes the device of any of the fourteenth to nineteenth aspects, wherein each of the plurality of first lands comprises a first land surface that transitions at a rounded edge to an associated one of the plurality of first base segments, and each of the plurality of second lands comprises a second land surface that transitions at a rounded edge to an associated one of the plurality of second base segments.

[0026] A 21st aspect includes the device of any of the 14th to 20th aspects, wherein each of the plurality of first lands includes a first land surface defined by a first constant arc, and each of the plurality of second lands includes a second land surface defined by a second constant arc.

[0027] A 22nd aspect includes the device of any of the 14th to 21st aspects, and each of the plurality of first lands and each of the plurality of second lands has a cylindrical land surface having a pair of side surfaces on either side of the cylindrical land surface.

[0028] A 23rd aspect includes the device of any of the 14th to 22nd aspects, wherein each of the plurality of first lands and each of the plurality of second lands comprises a land surface and a pair of side surfaces on either side of the land surface, and each of the pair of side surfaces is oriented at a draft angle of less than 90° relative to the cylindrical glass forming surface associated with each of the pair of side surfaces.

[0029] A twenty-fourth aspect includes the device of any of the fourteenth to twenty-third aspects, wherein the number of first lands in the first mold forming pocket is greater than the number of second lands in the second mold forming pocket.

[0030] A 25th aspect includes the device of any of the 14th to 24th aspects, wherein the number of first lands in the first molded pocket is equal to the number of second grooves associated with the second molded pocket.

[0031] A twenty-sixth aspect includes the apparatus of any of the first through third aspects, wherein the plurality of distinct molded features includes a knurling pattern defined by a first array of grooves and a second array of grooves, the first array of grooves and the second array of grooves extending at least partially continuously around at least one of the pair of opposing upper molding rolls, the second array of grooves intersecting the first array of grooves to define a plurality of knurls of the knurling pattern, each of the plurality of knurls including a peak, each distinct groove of the first array of grooves and the second array of grooves including a groove base, and each of the plurality of knurls including a height dimension measured between the peak and the groove base.

[0032] A twenty-seventh embodiment includes the device of the twenty-sixth embodiment, wherein the height dimension is equal to the depth.

[0033] A 28th aspect includes the apparatus of the 26th or 27th aspects, wherein the first array of grooves and the second array of grooves each extend spirally around the circumference of at least one of the pair of opposing upper forming rolls.

[0034] A 29th aspect includes the device of any of the 26th to 28th aspects, wherein the peak of each of the plurality of knurls has a flat contact surface.

[0035] A thirtieth aspect includes the device of any of the twenty-sixth to twenty-ninth aspects, wherein the flat contact surface of each of the plurality of knurls is flush with the cylindrical glass forming surface.

[0036] A thirty-first aspect includes the device of any one of the twenty-sixth to thirtieth aspects, wherein each of the plurality of knurls has a truncated pyramidal shape.

[0037] A 32nd aspect includes the device of any of the 26th to 31st aspects, wherein the molded pocket formed on at least one of the pair of opposing upper forming rolls extends over the entire axial length of at least one of the pair of opposing upper forming rolls.

[0038] A 33rd aspect includes the device of any of the 26th to 32nd aspects, and the knurling pattern includes a first knurling pattern formed on the cylindrical glass forming surface of a first upper forming roll of a pair of opposing upper forming rolls, and a second knurling pattern formed on the cylindrical glass forming surface of a second upper forming roll of the pair of opposing upper forming rolls.

[0039] A thirty-fourth aspect includes the device according to any one of the twenty-sixth to thirty-third aspects, in which the first knurling pattern and the second knurling pattern are the same.

[0040] A thirty-fifth embodiment includes the apparatus of any of the preceding embodiments, wherein the axial length of the molding pocket is less than the axial length of at least one of the pair of opposing upper molding rolls.

[0041] Additional features and advantages of the forming roll embodiments of the glass forming apparatus disclosed herein are set forth in the detailed description that follows, and in part will be readily apparent to those skilled in the art from the detailed description or will be learned by practicing the embodiments described herein, including the detailed description that follows, the claims, and the accompanying drawings.

[0042] Both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and features of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments described herein and, together with the detailed description, serve to explain the principles and operation of the claimed subject matter. [Brief explanation of the drawings]

[0043] [Figure 1] 1 illustrates a schematic diagram of a glass manufacturing apparatus including a forming apparatus for roll-forming a glass ribbon or glass-ceramic ribbon according to one or more embodiments shown and described herein. [Figure 2A] 2 shows a schematic partial cross-sectional view of a pair of opposing upper forming rolls of the forming apparatus of FIG. 1; [Figure 2B] 2 shows a schematic partial cross-sectional view of a pair of opposed lower forming rolls of the forming apparatus of FIG. 1; [Figure 3A] 2A and 2B schematically illustrate a cross-sectional view of a pair of opposing upper forming rolls that may be utilized with the forming apparatus of FIG. 1 according to one or more embodiments shown and described herein. [Figure 3B] 3B shows a detailed view of a portion of the pair of opposing upper forming rolls of FIG. 3A. [Figure 4A] 2A and 2B schematically illustrate a cross-sectional view of a pair of opposing upper forming rolls that may be utilized with the forming apparatus of FIG. 1 according to one or more embodiments shown and described herein. [Figure 4B] 4B is a schematic diagram showing a detailed view of a portion of the pair of opposing upper forming rolls of FIG. 4A; [Figure 5A] 2 illustrates a schematic diagram of an upper forming roll that may be utilized with the forming apparatus of FIG. 1 according to one or more embodiments shown and described herein. [Figure 5B] 5B shows a detailed cross-sectional view of a portion of the molding pocket of the upper molding roll of FIG. 5A. [Figure 5C] 5B shows a detailed isometric view of a portion of the molding pocket of the upper molding roll of FIG. 5A. [Figure 6] 10 graphically illustrates thermal modeling results for different molded pocket designs. [Figure 7] 10 graphically illustrates the relationship between the average temperature difference between the thick and thin sections of the glass ribbon and the ratio of roll surface contact area to volume for different molding pocket designs. DETAILED DESCRIPTION OF THE INVENTION

[0044] Reference will now be made in detail to embodiments of forming rolls having mold-forming pockets for extracting heat from a glass ribbon, and glass forming apparatuses comprising the same, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. One embodiment of a forming roll having a mold-forming pocket is shown in Figures 3A and 3B. The mold-forming pocket includes a plurality of distinct mold features formed in the mold-forming pocket and extending from a base of the mold-forming pocket, the plurality of distinct mold features in the mold-forming pocket increasing the surface of the roll in contact with the molten glass ribbon, thereby increasing heat extraction from the molten glass ribbon. Various embodiments of forming rolls having mold-forming pockets, glass forming apparatuses comprising the same, and methods for their use in producing glass ribbons are described herein with specific reference to the accompanying drawings.

[0045] Ranges may be expressed herein as from "about" one particular value, and / or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values ​​are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0046] Directional terms used herein, such as up, upper, lower, below, right, left, front, rear, top, bottom, are for reference only as drawn in the figures and are not intended to imply absolute orientation.

[0047] Unless otherwise expressly stated, it is in no way intended that any method described herein be construed as requiring its steps to be performed in a particular order, or that any apparatus require a particular orientation. Thus, where a method claim does not actually recite an order in which its steps are to be followed, or where any apparatus claim does not actually recite an order or orientation for particular components, or where the claims or the Detailed Description otherwise specifically state that the steps are to be limited to a particular order or that no particular order or orientation for apparatus components is recited, no order or orientation is intended to be inferred in any respect. This applies to any possible implicit basis for interpretation, including logical matters regarding the arrangement of steps, workflow, component order, or component orientation, apparent meaning derived from grammatical constructions or punctuation, and the number or type of embodiments described herein.

[0048] 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 dictates otherwise.

[0049] Referring now to FIG. 1 , an exemplary glass manufacturing apparatus 10 for forming a glass ribbon from molten glass is shown schematically. The glass manufacturing apparatus 10 may include a melter 11, a fining system 13, a mixing vessel 14, a feed vessel 18, and a forming apparatus 20. Glass batch materials are introduced into the melter 11 through a batch inlet port 12. The batch materials are melted in the melter 11 to form molten glass 16. The melter 11 is fluidly coupled to the fining system 13 with a connecting tube 15. The molten glass 16 flows from the melter 11, through the connecting tube 15, and into the fining system 13.

[0050] The fining system 13 may include a high-temperature processing area that receives the molten glass 16 from the melter 11. While the molten glass 16 is in the fining system 13, dissolved gases and / or bubbles are removed from the molten glass 16. The fining system 13 may be fluidly coupled to the mixing vessel 14 by a connecting tube 21. That is, the molten glass flowing from the fining system 13 to the mixing vessel 14 may flow through the connecting tube 21. As the molten glass 16 passes through the mixing vessel 14, the molten glass 16 may be agitated to homogenize the molten glass 16. The mixing vessel 14 may be fluidly coupled to the feed vessel 18 by a connecting tube 17 such that the molten glass 16 flowing from the mixing vessel 14 to the feed vessel 18 flows through the connecting tube 17. The feed vessel 18 supplies the molten glass 16, which has passed through a downcomber 19, to a glass forming apparatus 20 via a glass delivery device 22. As described below, the glass forming apparatus 20 uses forming rolls to form the molten glass into a glass ribbon 24. Thus, the glass manufacturing apparatus 10 can be used to roll form glass ribbons or glass-ceramic ribbons.

[0051] The glass forming apparatus 20 includes a pair of opposing upper forming rolls 30 and a pair of opposing lower forming rolls 32. The pair of opposing upper forming rolls 30 includes a first upper forming roll 30a and a second upper forming roll 30b. In the illustrated embodiment, the first upper forming roll 30a is an upper inner forming roll, and the second upper forming roll 30b is an upper outer forming roll. Similarly, the pair of opposing lower forming rolls 32 includes a first lower roll 32a and a second lower roll 32b. In the illustrated embodiment, the first lower roll 32a is an inner lower roll, and the second lower roll 32b is an outer lower roll. The glass forming apparatus 20 includes a vertical dimension along the Z-axis of the coordinate axes shown in the figure, a width dimension along the X-axis of the coordinate axes shown in the figure, and a thickness dimension along the Y-axis of the coordinate axes shown in the figure. The vertical dimension generally corresponds to the draw direction 31 in which the glass ribbon 24 is drawn by a pair of opposing upper forming rolls 30 and a pair of opposing lower forming rolls 32. The width dimension is perpendicular to the vertical dimension, and the width of the glass ribbon 24 may be measured in terms of the width dimension. The thickness dimension is perpendicular to the vertical and width dimensions, and the thickness of the glass ribbon 24 (i.e., the measurement between opposing surfaces of the glass ribbon 24) may be measured in terms of the thickness dimension.

[0052] The first upper forming roll 30a and the second upper forming roll 30b each include a pair of opposing circular end faces 34a and 34b, respectively, although only one of the pair of opposing circular end faces 34a of the first upper forming roll 30a and only one of the pair of opposing circular end faces 34b of the second upper forming roll 30b are shown in the schematic side view of Figure 1. The first upper forming roll 30a and the second upper forming roll 30b each include cylindrical glass forming surfaces 36a and 36b, which extend between the pair of opposing circular end faces 34a and 34b associated with the glass forming surfaces 36a and 36b. In particular, the cylindrical glass forming surface 36a of the first upper forming roll 30a extends between a pair of opposing circular end faces 34a of the glass forming surface 36a, and the cylindrical glass forming surface 36b of the second upper forming roll 30b extends between a pair of opposing circular end faces 34b of the glass forming surface 36b. In operation, the first upper forming roll 30a and the second upper forming roll 30b rotate in opposite directions to facilitate forming the molten glass into a glass ribbon, as indicated by the arrows in FIG.

[0053] Similarly, the first lower roll 32a and the second lower roll 32b each include circular end faces 40a and 40b, respectively. The first lower roll 32a and the second lower roll 32b also each include cylindrical glass forming surfaces 42a and 42b extending between a pair of opposing circular end faces 40a and 40b. In particular, the cylindrical glass forming surface 42a of the first lower roll 32a extends between the pair of opposing circular end faces 40a of the glass forming surface 42a, and the cylindrical glass forming surface 42b of the second lower roll 32b extends between the pair of opposing circular end faces 40b of the glass forming surface 42b. Thus, while each of the pair of opposing lower forming rolls 32 may be cylindrical in shape, in embodiments, either or both of the cylindrical glass forming surfaces 42a and 42b may be at least partially curved across the length of the roll between the end faces when evaluated in cross section along the length of the glass forming surface. In operation, first lower roll 30a and second lower roll 30b rotate in opposite directions, as indicated by the arrows in FIG. 1, to facilitate forming the molten glass into a glass ribbon.

[0054] The pair of opposing upper forming rolls 30 are spaced apart from one another to define a glass forming gap 50 between the cylindrical glass forming surfaces 36a, 36b of the first and second upper forming rolls 30a, 30b, respectively. As shown, the glass forming gap 50 of the pair of opposing upper forming rolls 30 is positioned vertically below the glass delivery device 22 to receive a stream of molten glass 16 supplied by the glass delivery device 22. The glass delivery device 22 deposits molten glass 16 into the glass forming gap 50 between the pair of opposing upper forming rolls 30, where the molten glass 16 can form a puddle 52 at a nip above the glass forming gap 50. The glass forming gap 50 receives the molten glass 16, and the counter-rotation of the pair of opposing upper forming rolls 30 thins the molten glass 16, thereby forming a glass ribbon 24 as the pair of opposing upper forming rolls 30 rotate.

[0055] Similarly, the pair of opposing lower forming rolls 32 are spaced apart to define a glass sizing gap 60 between the cylindrical glass forming surfaces 42 a, 42 b of the first and second lower rolls 32 a, 32 b, respectively. As shown, the glass sizing gap 60 is positioned vertically below the glass forming gap 50 to receive the glass ribbon 24 previously formed by the pair of upper forming rolls 30 and to reshape the glass ribbon 24 to a target thickness as the opposing lower forming rolls 32 rotate. The target thickness is defined by the glass sizing gap 60, which is established by the spacing between the pair of opposing lower forming rolls 32.

[0056] Molten glass flows downstream from the glass delivery device 22 into a glass forming gap 50 defined between a pair of opposing upper forming rolls 30, which form the molten glass into a glass ribbon 24 as the opposing upper forming rolls 30 rotate. The first upper forming roll 30a and the second upper forming roll 30b may extend across the width of the glass ribbon 24. Rotation of the pair of opposing upper forming rolls 30 causes the glass ribbon 24 to extend downward from the glass delivery device 22. For example, the first upper forming roll 30a and the second upper forming roll 30b may each be connected to one or more suitable mechanical devices (e.g., drive controller(s), motor(s), etc.) that rotate the associated first upper forming roll 30a and / or second upper forming roll 30b, where the speed of the pair of opposing upper forming rolls 30 can be adjusted to match the downward flow of the glass ribbon 24. The first upper forming roll 30 a and the second upper forming roll 30 b are rotated in opposite directions to draw the glass ribbon 24 downwardly toward a pair of opposing lower forming rolls 32 .

[0057] Additionally, the first upper forming roll 30 a and the second upper forming roll 30 b may each be connected to one or more suitable mechanical devices (e.g., air cylinders) that apply a horizontal force in the thickness dimension between the first upper forming roll 30 a and the second upper forming roll 30 b (i.e., such that the cylindrical glass forming surfaces 36 a and 36 b associated with the mechanical devices may be pressed together or such that the glass forming surfaces 36 a and 36 b may be pressed toward each other), thereby allowing a horizontal force to be applied to the glass ribbon 24 as it is formed between the pair of opposing upper forming rolls 30. The applied horizontal force, which defines the glass forming gap 50 between the upper forming rolls 30, or the mechanical stop position of each of the pair of opposing upper forming rolls 30, may be set to roll the glass ribbon 24 to at least one target thickness.

[0058] After being formed and rolled by the pair of opposing upper forming rolls 30, the glass ribbon 24 flows downstream toward the pair of opposing lower forming rolls 32. In particular, the glass ribbon 24 flows into a glass sizing gap 60 defined between the pair of opposing lower forming rolls 32, which sizes (and / or reshapes) the glass ribbon 24 to a target thickness.

[0059] Similar to the pair of opposing upper forming rolls 30, each of the pair of opposing lower forming rolls 32 extends across the width of the glass ribbon 24. Furthermore, the first lower roll 32 a and the second lower roll 32 b can each pull the glass ribbon 24 downward from the pair of upper forming rolls 30. For example, the first lower roll 32 a and the second lower roll 32 b can each be rotated (e.g., via drive controller(s), motor(s), etc.) to thereby pull the glass ribbon 24 downstream in a manner similar to that described above with reference to the pair of opposing upper forming rolls 30. Furthermore, the pair of opposing lower forming rolls 32 can be configured to apply a horizontal force between the lower forming rolls 32 to thereby squeeze the glass ribbon 24 in a manner similar to that described above with reference to the pair of opposing upper forming rolls 30.

[0060] Referring now to FIGS. 2A and 2B, which schematically illustrate a glass forming gap 50 defined between a pair of opposing upper forming rolls 30 and a glass sizing gap 60 defined between a pair of opposing lower forming rolls 32, at least one of the pair of opposing upper forming rolls 30 may include a groove 200. In the illustrated example, the groove 200 may be located in the second upper forming roll 30b. In other embodiments, the first upper forming roll 30a may include a corresponding groove. Also, although not fully illustrated in the partial view of FIG. 2A, the groove 200 may extend continuously around the circumference of the cylindrical glass forming surface 36b of the second upper forming roll 30b. Here, the groove 200 has a rectangular cross-section.

[0061] The groove 200 is formed into the cylindrical glass forming surface 36b of the second upper forming roll 30b at a depth 202 such that the groove 200 includes a base surface 204 and a pair of side surfaces 203a, 203b on either side of the base surface 204, and the base surface 204 is offset relative to the cylindrical glass forming surface 36b by an amount equal to the depth 202. In this manner, a nip distance 206 between the base surface 204 of the groove 200 of the second upper forming roll 30b and the cylindrical glass forming surface 36a of the first upper forming roll 30a is greater than a nip distance 208 between the cylindrical glass forming surface 36a of the first upper forming roll 30a and the cylindrical glass forming surface 36b of the second upper forming roll 30b outside the groove 200. An edge 205a is defined where the cylindrical glass forming surface 36b meets the side 203a of the groove 200, and an edge 205b is defined where the cylindrical glass forming surface 36b meets the side 203b of the groove 200. The groove 200 has an axial pocket length 201 measured in the width dimension between the edges 205a, 205b of the groove 200 along the axis of rotation of the second upper forming roll 30b.

[0062] As described herein, molten glass 16 is introduced into a glass forming gap 50 defined between and rolled between a pair of opposing upper forming rolls 30, thereby forming a glass ribbon 24. Due to the nip distance 206 in the groove 200 being greater than the nip distance 208 outside the groove 200, the glass ribbon 24 is formed having a thin portion 210 and a thick portion 212, with the thin portion 210 having a thickness corresponding to the nip distance 208 between the pair of opposing upper forming rolls 30 outside the groove 200 and the thick portion 212 having a thickness corresponding to the nip distance 206 between the pair of opposing upper forming rolls 30 within the groove 200. In this manner, the glass ribbon 24 is formed with a non-uniform thickness across the width of the glass ribbon 24.

[0063] The glass ribbon 24 then travels downstream and is received in a glass sizing gap 60 defined between the pair of opposing lower forming rolls 32. However, due to the non-uniform thickness of the glass ribbon 24 and the fact that the pair of opposing lower forming rolls 32 are spaced apart by a nip distance 214, each of the pair of opposing lower forming rolls 32 may not fully contact the glass ribbon 24 across the entire width of the glass ribbon. For example, as shown in FIG. 2B , the cylindrical glass shaping surface 42b of the second lower roll 32b contacts the glass ribbon 24 only at the thick portion 212. As previously described, the pair of opposing lower forming rolls 32 receive and size the glass ribbon 24 to a target thickness, and when a puddle is formed in the pair of opposing lower forming rolls 32, the pair of opposing lower forming rolls 32 may also reshape the glass ribbon 24 such that any undesirable artifacts or shapes previously imparted to the glass ribbon 24 can be corrected by use of the pair of opposing lower forming rolls 32. For example, the thicker portions 212 of the glass ribbon 24 may have a sufficiently low viscosity such that a puddle can be formed on the pair of opposing lower forming rolls 32, thereby enabling the pair of opposing lower forming rolls 32 to reshape the thicker portions 212 of the glass ribbon 24.

[0064] 1 , the glass ribbon 24, sized to a target thickness, proceeds downstream from the pair of opposing lower forming rolls 32 and may be redirected at a turning section 70. The turning section 70 may include a porous surface 72 facing the glass ribbon 24, through which a gas (e.g., air) may be introduced so that the glass ribbon 24 rides on an air cushion as it is redirected around the turning section 70.

[0065] 1 includes a pair of opposing upper forming rolls 30 and a pair of opposing lower forming rolls 32; this "two-stage setup" helps reduce any temperature difference between the thick and thin portions 212 and 210 of the glass ribbon 24 compared to a single-stage forming apparatus having a single roll set. This "two-stage setup" also helps improve stress and warpage compared to a single-stage forming apparatus (i.e., using only a pair of opposing rolls). However, in the above-described "two-stage setup," the temperature difference between the thin and thick portions 210 and 212 of the glass ribbon 24 at the turning section 70 is still very high, e.g., greater than 150° Celsius (C), for a thickness delta (i.e., thickness difference between the thin and thick portions 210 and 212) of approximately 1.4 millimeters (mm). Such temperature differences between the thicker portions 212 of the glass ribbon 24 and the thinner portions 210 of the glass ribbon 24 can result in curtain warp, sheet bowing, and stresses in the glass ribbon 24 and / or glass sheets segmented from the glass ribbon 24. As used herein, the term curtain warp refers to undulations in the glass ribbon 24 across its width caused when a glass ribbon 24 of non-uniform thickness is pulled around a turning section 70, with the thicker portions 212 and thinner portions 210 having different temperatures and viscosities.

[0066] By reducing the temperature difference between the thick section 212 and the thin section 210 before the turn 70, curtain warp, sheet bowing, and stress in the glass ribbon 24 can be reduced.

[0067] Disclosed herein is an upper forming roll including a molding pocket formed in the cylindrical glass forming surface of the upper forming roll. The molding pocket comprises a plurality of distinct molding features formed in the molding pocket extending from the base of the molding pocket. In embodiments, the molding pocket can have a depth of at least 0.5 mm when evaluated from or relative to the cylindrical glass forming surface of the forming roll. In embodiments, the depth is at least 0.75 mm, at least 1 mm, at least 1.25 mm, at least 1.5 mm, at least 1.75 mm, at least 2 mm, at least 2.25 mm, at least 2.5 mm, at least 2.75 mm, at least 3 mm, at least 3.25 mm, at least 3.5 mm, at least 3.75 mm, at least 4 mm, at least 4.25 mm, at least 4.5 mm, at least 4.75 mm, at least 5 mm, at least 5.25 mm, at least 5.5 mm, at least 5.75 mm, or even at least 6 mm. In embodiments, the depth is up to 10 mm. In embodiments, the depth is 0.75 mm to 10 mm, 2 mm to 6 mm, 2.25 mm to 5.75 mm, 2.5 mm to 5.5 mm, 2.75 mm to 5.25 mm, 3 mm to 5 mm, 3.25 mm to 4.75 mm, 3.5 mm to 4.5 mm, or even 3.75 mm to 4.25 mm. The molding pocket and the plurality of distinct molding features formed in the molding pocket increase the amount of surface of at least one of the pair of opposing upper forming rolls that contacts the glass ribbon, thereby increasing heat extraction from the glass ribbon and increasing the viscosity of the glass ribbon compared to a conventional upper forming roll such as that shown in FIG. 2A. Either or both of the pair of opposing upper forming rolls may include a molding pocket and a plurality of distinct molding features.When the glass ribbon being formed includes thin and thick portions, the molding pockets and multiple separate molding features are formed in multiple locations on the upper forming roll to increase surface contact with the thick portions of the glass ribbon. By increasing the amount of surface contact with the thick portions, the molding pockets and multiple separate molding features reduce the temperature difference in the glass ribbon (i.e., the temperature difference between the thick and thin portions of the glass ribbon is reduced). In these cases, one or more additional pairs of opposing rolls, such as a pair of opposing lower forming rolls, can be positioned below the pair of opposing upper forming rolls to reshape the glass ribbon of variable thickness so that the thick and thin portions of the glass ribbon are each at a target thickness. By reducing the temperature difference in the glass ribbon during the early stages of forming (i.e., before the turning section 70), such as a pair of opposing upper forming rolls, the embodiments disclosed herein can improve the quality of the glass ribbon by reducing curtain warp, sheet bowing, and stress in the glass ribbon. Also, in other cases where the glass ribbon being formed is of uniform thickness, embodiments described herein may be incorporated into existing "two-stage setups," such as those described in Figures 1-2, to provide greater heat extraction before turning section 70 and thereby facilitate the formation of a thicker glass ribbon of uniform thickness, or an evenly thick glass ribbon with higher flow density. In such embodiments, molding pockets and multiple separate molding features may be formed on either or both of a pair of opposing upper forming rolls and / or either or both of a pair of opposing lower forming rolls.

[0068] 3A-3B, FIG. 3A schematically illustrates a cross-sectional view of a pair of opposing upper forming rolls 300 according to one or more embodiments shown and described herein. The pair of opposing upper forming rolls 300 includes a first (or inner) upper forming roll 302a and a second (or outer) upper forming roll 302b. In embodiments, the first upper forming roll 302a and the second upper forming roll 302b may be incorporated into the forming apparatus 20 of FIG. 1 and utilized in place of the first upper forming roll 30a and the second upper forming roll 30b, respectively, to increase heat extraction from the glass ribbon 24. In such embodiments, the forming apparatus 20 may include at least a pair of opposing lower rolls, such as a pair of opposing lower forming rolls 32, positioned downstream of the pair of opposing upper forming rolls 300 to further extract heat from the glass ribbon 24 and / or reshape the glass ribbon 24 to a target size and shape.

[0069] The first upper forming roll 302a extends along and is rotatable about a first axis 304a, and the second upper forming roll 302b extends along and is rotatable about a second axis 304b. The first upper forming roll 302a includes a pair of opposing circular end faces 306a, 308a, and the axial length of the first upper forming roll 302a along the first axis 304a is defined between the pair of opposing circular end faces 306a, 308a. Similarly, the second upper forming roll 302b includes a pair of opposing circular end faces 306b, 308b, and the axial length of the second upper forming roll 302b along the second axis 304b is defined between the pair of opposing circular end faces 306b, 308b.

[0070] The first upper forming roll 302a includes a cylindrical glass forming surface 310a extending between a pair of opposing circular end faces 306a, 308a of the first upper forming roll 302a. Similarly, the second upper forming roll 302b includes a cylindrical glass forming surface 310b extending between a pair of opposing circular end faces 306b, 308b of the second upper forming roll 302b. The pair of opposing upper forming rolls 300 are spaced apart from each other to define a glass forming gap 312 between the cylindrical glass forming surfaces 310a, 310b. When the glass ribbon 24 to be formed includes portions having different thicknesses (e.g., the glass ribbon 24 shown in FIGS. 2A-2B including a thick portion 212 and a thin portion 210), the glass forming gap 312 can be set to a distance corresponding to the target thickness of the thin portion 210 of the glass ribbon 24.

[0071] In the illustrated embodiment, the first upper forming roll 302a and the second upper forming roll 302b each include molding pockets 320a, 320b formed within cylindrical glass forming surfaces 310a, 310b, respectively. Each of the molding pockets 320a, 320b extends circumferentially around the first upper forming roll 302a and the second upper forming roll 302b such that the molding pockets 320a, 320b, respectively, are generally cylindrical in shape.

[0072] 3A and 3B, each of the mold-forming pockets 320a, 320b includes a plurality of separate mold-forming features 322a, 322b formed therein and extending from a base 324a, 324b of the respective mold-forming pocket 320a, 320b. The base 324a, 324b of each of the mold-forming pockets 320a, 320b is radially offset by a depth d from the cylindrical glass forming surface 310a, 310b associated with the base (see FIG. 3B). Thus, the depth d of each of the mold-forming pockets 320a, 320b is measured between the base 324a, 324b of the mold-forming pocket 320a, 320b and the cylindrical glass forming surface 310a, 310b, respectively. The depth d and the geometry of the plurality of discrete mold-forming features 322a, 322b are selected to increase the surface area of ​​the mold-forming pockets 320a, 320b that contact the glass ribbon 24, thereby increasing heat extraction from the glass ribbon 24. In embodiments, the depth d may be at least 0.5 mm. In embodiments, the depth is at least 0.75 mm, at least 1 mm, at least 1.25 mm, at least 1.5 mm, at least 1.75 mm, at least 2 mm, at least 2.25 mm, at least 2.5 mm, at least 2.75 mm, at least 3 mm, at least 3.25 mm, at least 3.5 mm, at least 3.75 mm, at least 4 mm, at least 4.25 mm, at least 4.5 mm, at least 4.75 mm, at least 5 mm, at least 5.25 mm, at least 5.5 mm, at least 5.75 mm, or even at least 6 mm. In embodiments, the depth d is up to 10 mm. In embodiments, the depth d is 0.75 mm or more and 10 mm or less, 2 mm or more and 6 mm or less, 2.25 mm or more and 5.75 mm or less, 2.5 mm or more and 5.5 mm or less, 2.75 mm or more and 5.25 mm or less, 3 mm or more and 5 mm or less, 3.25 mm or more and 4.75 mm or less, 3.5 mm or more and 4.5 mm or less, or even 3.75 mm or more and 4.25 mm or less.

[0073] Figure 3A shows a region 330 of the glass forming gap 312 between the cylindrical glass forming surfaces 310a, 310b and the molding pockets 320a, 320b of the pair of opposing upper forming rolls 300, and Figure 3B illustrates a detailed view of region 330. As shown in Figure 3B, the plurality of separate mold forming features 322a of mold forming pocket 320a includes a plurality of lands 332a each extending from a base 324a of mold forming pocket 320a. Similarly, the plurality of separate mold forming features 322b of mold forming pocket 320b includes a plurality of lands 332b each extending from a base 324b of mold forming pocket 320b. In the illustrated embodiment, each of the plurality of lands 332a extends circumferentially and continuously around the first upper forming roll 302a, and each of the plurality of lands 332b extends circumferentially and continuously around the second upper forming roll 302b.

[0074] In the illustrated embodiment, the lands 332a are spaced apart by grooves 334a defined between them, and the grooves 334a extend continuously circumferentially around the first upper forming roll 302a. Similarly, the lands 332b are spaced apart by grooves 334b ​​defined between them, and the grooves 334b ​​extend continuously circumferentially around the second upper forming roll 302b. Although the lands 332a are equally spaced apart by the grooves 334a and the lands 332b are equally spaced apart by the grooves 334b ​​in the illustrated embodiment, in other embodiments, one or both of the lands 332a, 332b may not be equally spaced apart. For example, at least some of the plurality of lands 332a may be unevenly spaced, and / or at least some of the plurality of lands 332b may be unevenly spaced.

[0075] With respect to the first upper forming roll 302a, the base 324a of the molding pocket 320a may include a plurality of base segments 336a, and each of the plurality of lands 332a may be positioned between a pair of the plurality of base segments 336a. Similarly, with respect to the second upper forming roll 302b, the base 324b of the molding pocket 320b may include a plurality of base segments 336b, and each of the plurality of lands 332b may be positioned between a pair of the plurality of base segments 336b. In an embodiment, the plurality of base segments 336a define a cylindrical surface that is coaxial with the first upper forming roll 302a, and the plurality of base segments 336b define a cylindrical surface that is coaxial with the second upper forming roll 302b.

[0076] In the illustrated embodiment, each of the lands 332a associated with the first upper forming roll 302a includes a land surface 340a and a pair of side surfaces 342a, 344a on either side of the land surface 340a. Similarly, each of the lands 332b associated with the second upper forming roll 302b includes a land surface 340b and a pair of side surfaces 342b, 344b on either side of the land surface 340b. Here, each of the lands 332a includes a height dimension H measured between the land surface 340a and the base 324a of the mold forming pocket 320a, and each of the lands 332b includes a height dimension H measured between the land surface 340b and the base 324b of the mold forming pocket 320b. In embodiments, any one or more of the land surfaces 340a may be cylindrical and coaxial with the first upper forming roll 302a, and / or any one or more of the land surfaces 340b may be cylindrical and coaxial with the second upper forming roll 302b. In other embodiments, any one or more of the land surfaces 340a may be non-cylindrical (e.g., curved in cross section) and / or any one or more of the land surfaces 340b may be non-cylindrical (e.g., curved in cross section).

[0077] In the illustrated embodiment, land surface 340a may be flush with (or share an extent with) cylindrical glass forming surface 310a, and land surface 340b is flush with (or share an extent with) cylindrical glass forming surface 310b. In other words, height dimension H of lands 332a is equal to depth d of mold forming pocket 320a, and height dimension H of lands 332b is equal to depth d of mold forming pocket 320b. However, in other embodiments, one or more of land surfaces 340a may be raised from the cylindrical glass forming surface 310a associated with land surface 340a (i.e., the height dimension H of one or more of lands 332a is greater than the depth d of mold forming pocket 320a), and / or one or more of land surfaces 340b may be raised from the cylindrical glass forming surface 310b associated with land surface 340b (i.e., the height dimension H of one or more of lands 332b is greater than the depth d of mold forming pocket 320b). As used herein, the term "raised" is used to describe an element that extends beyond a designated reference. For example, one or more of land surfaces 340a can be raised from the cylindrical glass shaping surface 310a associated with land surface 340a because glass shaping surface 310a extends toward the centerline 313 of glass shaping gap 312, and / or one or more of land surfaces 340b can be raised from the cylindrical glass shaping surface 310b associated with land surface 340b because glass shaping surface 310b extends toward the centerline 313 of glass shaping gap 312. In embodiments, one or more of land surfaces 340a can be offset radially inward from the cylindrical glass shaping surface 310a associated with land surface 340a toward the first axis 304a, and / or one or more of land surfaces 340b can be offset radially inward from the cylindrical glass shaping surface 310b associated with land surface 340b toward the second axis 304b.For example, one or more of the land surfaces 340a may be recessed toward the first axis 304a relative to the cylindrical glass forming surface 310a (i.e., the height dimension H of one or more of the lands 332b is less than the depth d of the mold forming pocket 320a), and / or one or more of the land surfaces 340b may be recessed toward the second axis 304b relative to the cylindrical glass forming surface 310b (i.e., the height dimension H of one or more of the lands 332b is less than the depth d of the mold forming pocket 320b). In other embodiments, some of the lands 332a have a different height dimension H than others of the lands 332a. For example, the lands 332a in the center 370a of the molded pocket 320a may have a height dimension H greater than the lands 332a positioned on either side 372a, 374a of the land 332a, and similarly, some of the lands 332b may have a height dimension H different from other lands 332b, for example, the lands 332b in the center 370b of the molded pocket 320b may have a height dimension H greater than the lands 332b positioned on either side 372b, 374b of the land 332b.

[0078] In the illustrated embodiment, each of the lands 332 a of the molding pocket 320 a in the first upper forming roll 302 a extends radially toward one of the grooves 334 b in the second upper forming roll 302 b such that each of the lands 332 a faces one of the base segments 336 b of the molding pocket 320 b. Similarly, in the illustrated embodiment, each of the lands 332 b of the molding pocket 320 b in the second upper forming roll 302 b extends radially toward one of the grooves 334 a in the first upper forming roll 302 a such that each of the lands 332 b faces one of the base segments 336 a of the molding pocket 320 a.

[0079] The lands 332a, 332b may be molded at various draft angles. In the illustrated embodiment, the lands 332b are molded at a draft angle Θ, where the draft angle Θ is measured between one of the base segments 336b and a sidewall 346 that defines the edge of the molded pocket 320b. However, it should be understood that the angle defined between the side 342b and an associated one of the base segments 336b and the angle defined between the side 344b and an associated one of the base segments 336b are also draft angles that are equal to the draft angle Θ in this embodiment. Also, in this embodiment, the lands 332a are oriented at a draft angle Θ. Thus, the draft angle Θ of the lands 332a may be equal to the draft angle Θ of the lands 332b. In an embodiment, the draft angle Θ may be equal to or less than 90°, such as equal to or less than 85°, equal to or less than 80°, or even equal to or less than 75°. The draft angle Θ is greater than 0°. In embodiments, the draft angle Θ is at least 15°, at least 30°, at least 45°, or even at least 60°. In embodiments, the draft angle Θ is greater than or equal to 15° and less than or equal to 90°, greater than or equal to 30° and less than or equal to 90°, greater than or equal to 45° and less than or equal to 90°, or even greater than or equal to 60° and less than or equal to 90°. In embodiments, the draft angle Θ may be 75°. In other embodiments, any one or more of the plurality of lands 332a, 332b may be oriented at one or more different draft angles Θ.

[0080] In the illustrated embodiment, the lands 332b in the molding pockets 320b of the second upper forming roll 302b are more numerous than the lands 332a in the molding pockets 320a of the first upper forming roll 302a. Also, in this embodiment, the lands 332b in the molding pockets 320b are equal in number to the grooves 334a in the molding pockets 320a of the first upper forming roll 302a. However, in other embodiments, the lands 332b associated with the second upper forming roll 302b do not correspond in number to the grooves 334a associated with the first upper forming roll 302a. Thus, in other embodiments, the number of lands 332b molded on the first upper forming roll 302a can be any number, regardless of how many of the grooves 334a are molded into the molding pockets 320a, or vice versa.

[0081] When the first upper forming roll 302a and the second upper forming roll 302b are used in the glass forming apparatus 20 to form molten glass into a glass ribbon 24, heat is extracted from the glass ribbon 24 as the first upper forming roll 302a and the second upper forming roll 302b contact opposite sides of the glass ribbon 24, and the amount of heat extracted from the glass ribbon 24 depends on the amount of contact that each of the pair of opposing upper forming rolls 300 makes with the glass ribbon 24. Compared to conventional forming rolls, such as the pair of opposing upper forming rolls 30 described above in Figures 1 and 2A, the first upper forming roll 302a and the second upper forming roll 302b each have a relatively large amount of surface area in contact with the glass ribbon 24 due to the design of the molding pockets 320a, 320a, which include a plurality of lands 332a, 332b and a plurality of base segments 336a, 336b separating the plurality of lands 332a, 332b, respectively. Thus, first upper forming roll 302 a and second upper forming roll 302 b are able to extract a relatively large amount of heat from glass ribbon 24 .

[0082] In the illustrated embodiment, the plurality of grooves 334a in the first upper forming roll 302a includes an innermost groove 335a, an outermost groove 337a, and a plurality of central grooves located between the innermost groove 335a and the outermost groove 337a. Similarly, the plurality of grooves 334b ​​in the second upper forming roll 302b includes an innermost groove 335b, an outermost groove 337b, and a plurality of central grooves located between the innermost groove 335b and the outermost groove 337b. The molding pocket 320a includes an axial pocket length 321a measured along the first axis 304a from the innermost edge 338a of the innermost groove 335a to the outermost edge 339a of the outermost groove 337a. Similarly, molded pocket 320b includes an axial pocket length 321b measured along second axis 304b from the innermost edge 338b of innermost groove 335b to the outermost edge 339b of outermost groove 337b. In the illustrated embodiment, axial pocket length 321b of molded pocket 320b is greater than axial pocket length 321a of molded pocket 320a. In other embodiments, axial pocket lengths 321a, 321b are equal. In embodiments, the axial pocket length 321 a of the molding pocket 320 a spans the entire axial length of the first upper molding roll 302 a between the pair of opposing circular end faces 306 a, 308 a of the first upper molding roll 302 a, and / or the axial pocket length 321 b of the molding pocket 320 b spans the entire axial length of the second upper molding roll 302 b between the pair of opposing circular end faces 306 b, 308 b of the second upper molding roll 302 b. In embodiments, the axial pocket lengths 321 a, 321 b are at least 10 mm, at least 20 mm, at least 30 mm, at least 40 mm, at least 50 mm, or even at least 60 mm.In an embodiment, the axial pocket length 321a may be 10 mm or more and less than the total axial length of the first upper forming roll 302a, 20 mm or more and less than the total axial length, 40 mm or more and less than the total axial length, or even 60 mm or more and less than the total axial length, and the axial pocket length 321b may be 10 mm or more and less than the total axial length of the second upper forming roll 302b, 20 mm or more and less than the total axial length, 40 mm or more and less than the total axial length, or even 60 mm or more and less than the total axial length. In the illustrated embodiment, molding pocket 320a is centrally located along the axial length of the first upper molding roll 302a and molding pocket 320b is centrally located along the axial length of the second upper molding roll 302b; however, molding pocket 320a may be offset toward either of the pair of opposing circular end faces 306a, 308a so as to be non-centered, and / or molding pocket 320b may be offset toward either of the pair of opposing circular end faces 306b, 308b so as to be non-centered.

[0083] When evaluated in cross-section (and in a plane extending through the axis 304 a of the first upper forming roll 302 a and the axis 304 b of the second upper forming roll 302 b), the molding pocket 320 a contacts the glass ribbon along a contact line that is equal to the sum of the lengths of the land surface 340 a, the side surfaces 342 a, the side surfaces 344 a, and the base segment 336 a of the molding pocket 320 a, which sum is greater than the axial pocket length 321 a of the molding pocket 320 a due to the incorporation of multiple lands 332 a and multiple grooves 334 a. The contact line of the molding pocket 320 a can be varied by adjusting various parameters, such as the depth d, draft angle Θ, and / or dimensions of any one or more of the land surface 340 a, the side surfaces 342 a, the side surfaces 344 a, and / or the base segment 336 a of the molding pocket 320 a. Additionally, the contact line of the mold-forming pocket 320 a may vary due to rounded edges or beveled surfaces between any one or more of the land surfaces 340 a and either or both of the side surfaces 342 a, 344 a associated with the land surface 340 a. The contact line of the mold-forming pocket 320 a may also vary due to including a large or small number of the lands 332 a and grooves 334 a. Similarly, when evaluated in the same plane, the mold-forming pocket 320 b contacts the glass ribbon along a contact line equal to the sum of the lengths of the land surface 340 b, the side surfaces 342 b, the side surfaces 344 b, and the base segment 336 b of the mold-forming pocket 320 b, which sum is greater than the axial pocket length 321 b of the mold-forming pocket 320 b due to the incorporation of the lands 332 b and grooves 334 b. The contact line of molding pocket 320b may vary in a manner similar to that described above with reference to the contact line of molding pocket 320a. In embodiments, the total contact line of molding pockets 320a, 320b, which is the sum of the contact line of molding pocket 320a and the contact line of molding pocket 320b, is 20% to 100% greater than the total contact line for a pair of opposing upper forming rolls with molding pockets that do not have multiple molding features.In embodiments, the characteristic periods 380a, 380b, measured between adjacent lands 332a, 332b, respectively, are greater than or equal to 2 mm and less than or equal to 30 mm, greater than or equal to 3 mm and less than or equal to 25 mm, greater than or equal to 4 mm and less than or equal to 20 mm, or even greater than or equal to 5 mm and less than or equal to 15 mm. In the illustrated embodiment, the characteristic periods 380a are uniform across mold forming pocket 320a and the characteristic periods 380b are uniform across mold forming pocket 320b, although in other embodiments, one or more of the characteristic periods 380a may differ from the other characteristic periods 380a in mold forming pocket 320a and / or one or more of the characteristic periods 380b may differ from the other characteristic periods 380b in mold forming pocket 320b.

[0084] Each of the plurality of grooves 334a defined between the plurality of lands 332a and the cylindrical glass forming surface 310a has a first cross-sectional area, and each of the plurality of grooves 334b ​​defined between the plurality of lands 332b and the cylindrical glass forming surface 310b has a second cross-sectional area, when evaluated in a plane extending through the axis 304a of the first upper forming roll 302a and the axis 304b of the second upper forming roll 302b. The total cross-sectional area of ​​the plurality of grooves 334a, 334b ​​is the sum of all of the first and second cross-sectional areas. However, molding pocket 320a and / or molding pocket 320b may include different geometries and dimensions such that a greater or lesser portion of glass ribbon 24 contacts molding pocket 320a, 320b, depending on how much heat is desired to be extracted from the glass ribbon 24 and from which portion(s) of the glass ribbon 24, depending on the desired thickness of the glass ribbon 24, and / or whether any additional pairs of forming rolls are utilized. Depending on the geometry of molding pockets 320a, 320b, the combined cross-sectional area of ​​multiple grooves 334a, 334b ​​may be greater than, less than, or the same as the cross-sectional area of ​​a molding pocket without the multiple molding features.

[0085] When contacted by the pair of opposing upper forming rolls 300, the portion of the glass ribbon 24 located in the grooves 334a, 334b ​​is exposed to a relatively low pressure. However, in a region 350 between the pair of opposing upper forming rolls 300 where the distance between the lands 332a (of the first upper forming roll 302a) and the lands 332b (of the second upper forming roll 302b) is smallest, the glass ribbon 24 is exposed to a relatively high pressure. In other words, the portion of the glass ribbon 24 corresponding to region 350 may experience a pressure spike, while other portions of the glass ribbon 24 located in the grooves 334a, 334b ​​are exposed to a significantly lower pressure. Because increased pressure is associated with increased temperature, the glass ribbon 24 will experience a higher temperature in region 350. However, due to the lower pressure in the grooves 334a, 334b, the glass ribbon 24 will experience a localized area of ​​relatively lower temperature. In particular, these localized relatively low temperature regions in the glass ribbon 24 correspond to corners 352a defined between the plurality of base segments 336a and a pair of side surfaces 342a, 344a on either side of the base segments 336a, and also correspond to corners 352b defined between the plurality of base segments 336b and a pair of side surfaces 342b, 344b on either side of the base segments 336b.

[0086] 4A-4B, Figure 4A schematically illustrates a cross-sectional bottom view of an alternative embodiment of a pair of opposing upper forming rolls 300 according to one or more embodiments shown and described herein. As shown, the first upper forming roll 302a and the second upper forming roll 302b each have molding pockets 420a, 420b formed within their cylindrical glass forming surfaces 310a, 310b, respectively, with the molding pockets 420a, 420b in Figures 4A-4B including different geometries than the molding pockets 320a, 320b in Figures 3A-3B.

[0087] 4A-4B may be incorporated into the forming apparatus 20 of FIG. 1 and utilized in place of the first upper forming roll 30a and the second upper forming roll 30b, respectively, to increase heat extraction from the glass ribbon 24. In such embodiments, the forming apparatus 20 may include at least one pair of opposing lower rolls, such as a pair of opposing lower forming rolls 32, positioned downstream to further extract heat from the glass ribbon 24 and / or reshape the glass ribbon 24 to a target size and shape.

[0088] Each of the molding pockets 420 a, 420 b extends circumferentially around the first and second upper forming rolls 302 a, 302 b such that the molding pockets 420 a, 420 b are generally cylindrical in shape. Each of the molding pockets 420 a, 420 b includes a plurality of distinct molding features 422 a, 422 b formed into the molding pocket and extending from a base 424 a, 424 b of the respective molding pocket 420 a, 420 b. The base 424 a, 424 b of each of the molding pockets 420 a, 420 b is radially offset by a depth d′ from the cylindrical glass forming surface 310 a, 310 b associated with the base (see FIG. 4B ). Thus, the depth d' of each of mold forming pockets 420a, 420b is measured between base 424a, 424b and cylindrical glass forming surface 310a, 310b, respectively. The depth d and the geometry of the plurality of discrete mold forming features 422a, 422b are selected to increase the amount of surface of mold forming pockets 420a, 420b that contacts glass ribbon 24, thereby increasing heat extraction from glass ribbon 24. In an embodiment, depth d' may be at least 0.5 mm. In embodiments, the depth d' is at least 0.75 mm, at least 1 mm, at least 1.25 mm, at least 1.5 mm, at least 1.75 mm, at least 2 mm, at least 2.25 mm, at least 2.5 mm, at least 2.75 mm, at least 3 mm, at least 3.25 mm, at least 3.5 mm, at least 3.75 mm, at least 4 mm, at least 4.25 mm, at least 4.5 mm, at least 4.75 mm, at least 5 mm, at least 5.25 mm, at least 5.5 mm, at least 5.75 mm, or even at least 6 mm.In embodiments, the depth d' is 0.75 mm or more and 10 mm or less, 2 mm or more and 6 mm or less, 2.25 mm or more and 5.75 mm or less, 2.5 mm or more and 5.5 mm or less, 2.75 mm or more and 5.25 mm or less, 3 mm or more and 5 mm or less, 3.25 mm or more and 4.75 mm or less, 3.5 mm or more and 4.5 mm or less, or even 3.75 mm or more and 4.25 mm or less.

[0089] Figure 4A shows a region 430 of the glass forming gap 312 between the cylindrical glass forming surfaces 310a, 310b and the molding pockets 420a, 420b of the pair of opposing upper forming rolls 300, and Figure 4B illustrates a detailed view of region 430. As shown in Figure 4B, the plurality of separate mold forming features 422a of mold forming pocket 420a includes a plurality of lands 432a each extending from a base 424a of mold forming pocket 420a. Similarly, the plurality of separate mold forming features 422b of mold forming pocket 420b includes a plurality of lands 432b each extending from a base 424b of mold forming pocket 420b. In the illustrated embodiment, each of the plurality of lands 432a extends circumferentially and continuously around the first upper forming roll 302a, and each of the plurality of lands 432b extends circumferentially and continuously around the second upper forming roll 302b.

[0090] In the illustrated embodiment, the lands 432a are spaced apart by grooves 434a defined between them, and the grooves 434a extend continuously circumferentially around the first upper forming roll 302a. Similarly, the lands 432b are spaced apart by grooves 434b defined between them, and the grooves 434b extend continuously circumferentially around the second upper forming roll 302b. In the illustrated embodiment, the lands 432a are equally spaced apart by the grooves 434a, and the lands 432b are equally spaced apart by the grooves 434b. However, it should be understood that in other embodiments, either or both of the lands 432a, 432b may not be equally spaced. At least some of the plurality of lands 432a may be unevenly spaced, and / or at least some of the plurality of lands 432b may be unevenly spaced.

[0091] In the illustrated embodiment, the number of lands 432b in mold forming pocket 420b is greater than the number of lands 432a in mold forming pocket 420a. Stated another way, Figures 4A and 4B illustrate an example in which there are more lands 432b than lands 432a. Also, in the illustrated embodiment, the number of lands 432a in mold forming pocket 420a is equal to the number of grooves 434b associated with mold forming pocket 420b. Stated another way, Figures 4A and 4B illustrate an example in which the number of lands 432a in mold forming pocket 420a is equal to the number of grooves 434b in mold forming pocket 420b.

[0092] For the first upper forming roll 302a, the base 424a of the molding pocket 420a may include a plurality of base segments 436a, and each of the plurality of lands 432a may be positioned between a pair of the plurality of base segments 436a. Similarly, for the second upper forming roll 302b, the base 424b of the molding pocket 420b may include a plurality of base segments 436b, and each of the plurality of lands 432b may be positioned between a pair of the plurality of base segments 436b. In embodiments, each of the plurality of base segments 436a of the molding pocket 420a and each of the plurality of base segments 436b of the molding pocket 420b may be at least partially curved when evaluated in a plane extending through the first axis 304a and the second axis 304b. In embodiments, each of the plurality of base segments 436a and each of the plurality of base segments 436b have equal curvatures. In other embodiments, each of the plurality of base segments 436a can have a first curvature, while each of the plurality of base segments 436b can have a second curvature that is different from the first curvature. In other embodiments, at least one of the plurality of base segments 436a can have a different curvature than the remainder(s) of the plurality of base segments 436a, and / or at least one of the plurality of base segments 436b can have a different curvature than the remainder(s) of the plurality of base segments 436b.

[0093] In the illustrated embodiment, each of the plurality of lands 432a of the molding pocket 420a is raised from the cylindrical glass forming surface 310a of the first upper forming roll 302a, and each of the plurality of lands 432b of the molding pocket 420b is raised from the cylindrical glass forming surface 310b of the second upper forming roll 302b. For example, each of the multiple lands 432a of mold forming pocket 420a includes a land surface 460a, and the height dimension H' of each of the multiple lands 432a measured between the land surface 460a and the base 424a of mold forming pocket 420a is greater than the depth d' of mold forming pocket 420a, and each of the multiple lands 432b of mold forming pocket 420b includes a land surface 460b, and the height dimension H' of each of the multiple lands 432b measured between the land surface 460b and the base 424b of mold forming pocket 420b is greater than the depth d' of mold forming pocket 420b. In other embodiments, at least one of the lands 432a of the molding pocket 420a may not be raised above the cylindrical glass forming surface 310a of the first upper forming roll 302a (i.e., the height dimension H' of at least one of the lands 432a is less than or equal to the depth d' of the molding pocket 420a), and / or at least one of the lands 432b of the molding pocket 420b may not be raised above the cylindrical glass forming surface 310b of the second upper forming roll 302b (i.e., the height dimension H' of at least one of the lands 432b is less than or equal to the depth d' of the molding pocket 420b).In other embodiments, at least one of the lands 432a of the mold forming pocket 420a may be at the same height as the cylindrical glass forming surface 310a associated with the land 432a (i.e., the height dimension H' of at least one of the lands 432a is equal to the depth d' of the mold forming pocket 420a), and / or at least one of the lands 432b of the mold forming pocket 420b may be at the same height as the cylindrical glass forming surface 310b associated with the land 432b (i.e., the height dimension H' of at least one of the lands 432b is equal to the depth d' of the mold forming pocket 420b). In other embodiments, at least one of the lands 432a of the mold-forming pocket 420a may be recessed within the mold-forming pocket 420a relative to the cylindrical glass forming surface 310a associated with the land 432a such that the land 432a extends a distance from the base 424a of the mold-forming pocket 420a that is less than the depth d' (i.e., the height dimension H' of at least one of the lands 432a is less than the depth d' of the mold-forming pocket 420a), and / or at least one of the lands 432b of the mold-forming pocket 420b may be recessed within the mold-forming pocket 420b relative to the cylindrical glass forming surface 310b associated with the land 432b such that the land 432b extends a distance from the base 424b of the mold-forming pocket 420b that is less than the depth d' (i.e., the height dimension H' of at least one of the lands 432b is less than the depth d' of the mold-forming pocket 420b). In an embodiment, the height dimension H' of one or more of the multiple lands 432a at the center 470a of the molded pocket 420a is greater than the height dimension H' of the multiple lands 432a on either side 472a, 474a of the center 470a, and / or the height dimension H' of one or more of the multiple lands 432b at the center 470b of the molded pocket 420b is greater than the height dimension H' of the multiple lands 432b on either side 472b, 474b of the center 470b.

[0094] In the illustrated embodiment, each of the multiple lands 432a of the molding pockets 420a of the first upper molding roll 302a extends radially toward one of the multiple grooves 434b of the second upper molding roll 302b, and each of the multiple lands 432b of the molding pockets 420b of the second upper molding roll 302b extends radially toward one of the multiple grooves 434a of the first upper molding roll 302a. As shown, each of the multiple lands 432a of the molding pocket 420a of the first upper molding roll 302a extends radially toward one of the multiple base segments 436b of the molding pocket 420b of the second upper molding roll 302b, and each of the multiple lands 432b of the molding pocket 420b of the second upper molding roll 302b extends radially toward one of the multiple base segments 436a of the molding pocket 420a of the first upper molding roll 302a. In the illustrated embodiment, each of the lands 432a of the mold forming pocket 420a of the first upper forming roll 302a is flush with the cylindrical glass forming surface 310b of the second upper forming roll 302b, and each of the lands 432b of the mold forming pocket 420b of the second upper forming roll 302b is flush with the cylindrical glass forming surface 310a of the first upper forming roll 302a. In other words, in the illustrated embodiment, the height dimension H' of each of the lands 432a is equal to the sum of the depths d' of the mold forming pocket 420a and the glass forming gap 312, and the height dimension H' of each of the lands 432b is equal to the sum of the depths d' of the mold forming pocket 420b and the glass forming gap 312.In this embodiment, each of the multiple lands 432a of the first upper forming roll 302a extends beyond the centerline 313 of the glass forming gap 312, and each of the multiple lands 432b of the second upper forming roll 302b extends beyond the centerline 313 of the glass forming gap 312, so that each of the multiple lands 432a of the first upper forming roll 302a also extends beyond the land surface 460b of the multiple lands 432b of the second upper forming roll 302b, and so that each of the multiple lands 432b of the second upper forming roll 302b also extends beyond the land surface 460a of the multiple lands 432a of the first upper forming roll 302a. In other embodiments, at least one of the multiple lands 432a may extend from the base 424a of the mold forming pocket 420a to the centerline 313 (i.e., the height dimension H' of the land 432a is equal to the sum of the depth d' and half the glass forming gap 312), and / or at least one of the multiple lands 432b may extend from the base 424b of the mold forming pocket 420b to the centerline 313 (i.e., the height dimension H' of the land 432b is equal to the sum of the depth d' and half the glass forming gap 312).

[0095] In other embodiments, at least one land surface 460a of the plurality of lands 432a of the first upper forming roll 302a may be raised from the cylindrical glass forming surface 310b of the second upper forming roll 302b, and at least one land surface 460b of the plurality of lands 432b of the second upper forming roll 302b may be raised from the cylindrical glass forming surface 310a of the first upper forming roll 302a, where, for example, at least one of the plurality of lands 432a extends beyond the centerline 313 by an amount that is the greater half of the glass forming gap 312, and at least one of the plurality of lands 432b extends beyond the centerline 313 by an amount that is the greater half of the glass forming gap 312. In these embodiments, at least one of the lands 432a of the molding pocket 420a of the first upper molding roll 302a extends radially (at least partially) through one of the grooves 434b of the second upper molding roll 302b, and at least one of the lands 432b of the molding pocket 420b of the second upper molding roll 302b extends radially (at least partially) through one of the grooves 434a of the first upper molding roll 302a.

[0096] In the embodiment, the plurality of grooves 434a defined in the molding pockets 420a of the first upper molding roll 302a include an innermost groove 440a, an outermost groove 442a, and a plurality of central grooves 444a between the innermost groove 440a and the outermost grooves 442a, and the plurality of grooves 434b defined in the molding pockets 420b of the second upper molding roll 302b include an innermost groove 440b, an outermost groove 442b, and a plurality of central grooves 444b between the innermost groove 440b and the outermost grooves 442b. In this embodiment, the multiple lands 432a of the molding pocket 420a of the first upper molding roll 302a include an innermost land 450a extending radially through the innermost groove 440b of the molding pocket 420b of the second upper molding roll 302b, an outermost land 452a extending radially through the outermost groove 442b of the molding pocket 420b of the second upper molding roll 302b, and multiple central lands 454a each extending radially through a respective one of the multiple central grooves 444b of the molding pocket 420b of the second upper molding roll 302b.

[0097] The molding pocket 420a of the first upper forming roll 302a includes an axial pocket length 421a measured along the first axis 304a. In the illustrated embodiment, the axial pocket length 421a of the molding pocket 420a of the first upper forming roll 302a is measured from the inner edge 456a (defined between the innermost land 450a and the cylindrical glass forming surface 310a) to the outer edge 458a (defined between the outermost land 452a and the cylindrical glass forming surface 310a). Similarly, the molding pocket 420b of the second upper forming roll 302b includes an axial pocket length 421b measured along the second axis 304b. In the illustrated embodiment, the axial pocket length 421b of the molding pocket 420b of the second upper forming roll 302b is measured from the inner edge 450b (defined between the innermost groove 440b and the cylindrical glass forming surface 310b) to the outer edge 452b (defined between the outermost groove 442b and the cylindrical glass forming surface 310b).

[0098] In embodiments, the land surface 460a of each of the plurality of lands 432a transitions to an associated one of the plurality of base segments 436a at an edge 462a. In embodiments, at least one of the edges 462a may be a rounded edge. In embodiments, at least one of the edges 462a may be a non-rounded edge (e.g., a sharp edge, a beveled edge, etc.). In embodiments, the land surface 460b of each of the plurality of lands 432b transitions to an associated one of the plurality of base segments 436b at an edge 462b. In embodiments, at least one of the edges 462b may be a rounded edge. In embodiments, the edges 462a, 463b are defined by a radius of greater than or equal to 0.2 mm and less than or equal to 6 mm, greater than or equal to 0.6 mm and less than or equal to 3 mm, or even greater than or equal to 0.9 mm and less than or equal to 1.5 mm. In embodiments, at least one of the plurality of lands 432a has a constant arc such that the land surface 460a and the edge 462a define a curved surface having a constant radius. Similarly, in embodiments, at least one of the plurality of lands 432b has a constant arc such that the land surface 460b and the edge 462b define a curved surface having a constant radius. In embodiments, the constant radius of at least one of the plurality of lands 432a and / or at least one of the plurality of lands 432b is equal to or greater than 0.2 mm and equal to or less than 6 mm, equal to or greater than 0.6 mm and equal to or less than 3 mm, or even equal to or greater than 0.9 mm and equal to or less than 1.5 mm. In embodiments, at least one of the edges 462b may be a non-rounded edge (e.g., a sharp edge, a beveled edge, etc.). In embodiments, at least one of the land surfaces 460a and / or at least one of the land surfaces 460b may be at least partially defined by a radius.

[0099] The lands 432a, 432b of the first upper forming roll 302a and the second upper forming roll 302b can be oriented at one or more draft angles. In an embodiment, each of the lands 432a includes a side surface 464a, 466a on either side of the land surface 460a, and each of the lands 432b includes a side surface 464b, 466b on either side of the land surface 460b. In the illustrated embodiment, the lands 432a each extend at a draft angle Θ', illustrated as a measurement between the side surface 464a of the innermost land 450a and the cylindrical glass forming surface 310a. However, measurements between the cylindrical glass forming surface 310a and either of the side surfaces 464a, 466a of other of the lands 432a (i.e., the outermost land 452a and the central lands 454a) are also, in this embodiment, at a draft angle equal to the draft angle Θ'. The draft angle Θ' is greater than 0°. In embodiments, the draft angle Θ is greater than or equal to 15° and less than or equal to 90°, greater than or equal to 30° and less than or equal to 90°, greater than or equal to 45° and less than or equal to 90°, or even greater than or equal to 60° and less than or equal to 90°.

[0100] In embodiments, the lands 432b may be oriented at a draft angle Θ'. Thus, the draft angle Θ' of the lands 432b may be equal to the draft angle Θ' of the lands 432a. In embodiments, the draft angle Θ may be 90° or less, such as about 85° or less, about 80° or less, or even about 75° or less. In other embodiments, any one or more of the lands 432a, 432b may be oriented at one or more different draft angles Θ'.

[0101] In these embodiments, the molding pockets 420a, 420b of the first upper forming roll 302a and the second upper forming roll 302b are designed so that the glass ribbon 24 (or portions of the glass ribbon 24) located between the molding pocket 420a of the first upper forming roll 302a and the molding pocket 420b of the second upper forming roll 302b has a uniform or constant thickness, evaluated along the first axis 304a and the second axis 304b, which in the illustrated embodiment is equal to the depth d'. This is because the distance between the base segment 436b and the plurality of lands 432a and the distance between the base segment 436a and the plurality of lands 432b are equal and uniform over the axial pocket lengths 421a, 421b of the molding pockets 420a, 420b. If the glass ribbon 24 to be formed is to have a variable thickness (e.g., such as the glass ribbon 24 shown in Figures 2A and 2B, which includes thick portions 212 and thin portions 210), the axial pocket lengths 421a, 421b of the molding pockets 420a, 420b will correspond to the width of the thick portions 212 of the glass ribbon 24, such that the thick portions 212 of the glass ribbon 24 will have a thickness corresponding to the spacing between the molding pockets 420a, 420b, and will have a geometric shape corresponding to the molding pockets 420a, 420b.

[0102] The molding pocket 420a formed in the first upper forming roll 302a effectively increases the amount of the first upper forming roll 302a that contacts the glass ribbon 24 relative to the amount that the molding pocket 420a would otherwise be present (i.e., the first upper forming roll 302a were substantially fully cylindrical or included only the grooves 200 of FIG. 2A ). In particular, the lands 432a and base segments 436a of the molding pocket 420a increase contact with the glass ribbon 24 such that more heat may be extracted from the portion of the glass ribbon 24 that contacts the molding pocket 420a. Similarly, the molding pocket 420b of the second upper forming roll 302b increases contact with the portion of the glass ribbon 24, thereby increasing heat extraction from the portion of the glass ribbon 24 that contacts the molding pocket 420b.

[0103] When evaluated in cross section (and in a plane extending through the axis 304a of the first upper forming roll 302a and the axis 304b of the second upper forming roll 302b), the molding pocket 420a contacts the glass ribbon 24 along a contact line that is equal to the sum of the lengths of each of the base segments 436a and the land surfaces 460a of the lands 432a in the molding pocket 420a of the first upper forming roll 302a, which sum is greater than the axial pocket length 421a of the molding pocket 420a due to the incorporation of the lands 432a and grooves 434a. The contact line of the molded pocket 420a can be varied by adjusting various parameters, such as the depth d', draft angle Θ', and / or dimensions of any one or more of the lands 432a, land surfaces 460a of the lands 432a, and / or base segments 436a of the molded pocket 420a. Additionally, the contact line of the molded pocket 420a can be varied by changing the geometry of the edges 462a, 462b (e.g., rounded or sharp) or whether a beveled surface is utilized in place of any one or more of the edges 462a, 462b. In embodiments, the contact line of the molded pocket 420a can be varied by including a large number or a small number of the lands 432a and grooves 434a. Similarly, when evaluated in the same plane, the molding pocket 420b of the second upper forming roll 302b contacts the glass ribbon 24 along a contact line equal to the sum of the lengths of the base segments 436b and the land surfaces 460b of the lands 432b in the molding pocket 420b, which sum is greater than the axial pocket length 421b of the molding pocket 420b due to the incorporation of the lands 432b and grooves 434b. The contact line of the molding pocket 420b of the second upper forming roll 302b can vary in a similar manner as described above with reference to the contact line of the molding pocket 420a of the first upper forming roll 302a.In some embodiments, the total contact line of molding pockets 420a, 420b, which is the sum of the contact line of molding pocket 420a and the contact line of molding pocket 420b, is 20% to 100% greater than the total contact line for a pair of opposing upper molding rolls with molding pockets that do not have multiple molding features. In embodiments, the feature period 480a, 480b, measured between adjacent lands 432a, 432b, respectively, is 2 mm to 30 mm, 3 mm to 25 mm, 4 mm to 20 mm, or even 5 mm to 15 mm. In the illustrated embodiment, the characteristic periodicity 480a is uniform for the molding pocket 420a and the characteristic periodicity 480b is uniform for the molding pocket 420b, however, in other embodiments, one or more of the characteristic periodicities 480a may differ from the other characteristic periodicities 480a in the molding pocket 420a and / or one or more of the characteristic periodicities 480b may differ from the other characteristic periodicities 480b in the molding pocket 420b. A cross-sectional area is defined between a pair of opposing upper molding rolls 300 along the axial pocket length 421b when evaluated in a plane defined by the first axis 304a and the second axis 304b. However, molding pocket 420b and / or molding pocket 420a may include different geometries and dimensions so that a larger or smaller portion of the glass ribbon 24 is in contact with molding pockets 420a, 420b (i.e., so that the total contact line and / or cross-sectional area is larger or smaller), depending on how much heat is desired to be extracted from the glass ribbon 24 and from which portion(s) of the glass ribbon 24 the heat is extracted, depending on the desired thickness of the glass ribbon 24, and / or depending on whether any additional pairs of forming rolls are utilized.Depending on the geometry of the molding pocket 420a, 420a, including the multiple lands 432a, 432b and the multiple grooves 434a, 434b in the multiple lands 432a, 432b, the total cross-sectional area defined between a pair of opposing upper molding rolls 300 along the axial pocket length 421b may be greater than, less than, or the same as the cross-sectional area of ​​a molding pocket without the multiple molding features.

[0104] When the first upper forming roll 302a and the second upper forming roll 302b are used in the glass forming apparatus 20 to form molten glass into a glass ribbon 24, heat is extracted from the glass ribbon 24 as the first upper forming roll 302a and the second upper forming roll 302b contact opposite sides of the glass ribbon 24, and the amount of heat extracted from the glass ribbon 24 depends on the amount of contact that each of the pair of opposing upper forming rolls 300 makes with the glass ribbon 24. Compared to conventional forming rolls, such as the pair of opposing upper forming rolls 30 described above in Figures 1 and 2A, the first upper forming roll 302a and the second upper forming roll 302b each have a relatively large amount of surface area in contact with the glass ribbon 24 due to the design of the mold forming pockets 420a, 420a, which include a plurality of lands 432a, 432b and a plurality of base segments 436a, 436b separating the plurality of lands 432a, 432b, respectively. Thus, first upper forming roll 302 a and second upper forming roll 302 b are able to extract a relatively large amount of heat from glass ribbon 24 .

[0105] As the molten glass is rolled by the pair of opposing upper forming rolls 300, the pressure experienced by the portions of the glass ribbon 24 corresponding to the molding pockets 420a, 420b is more uniform than that described with reference to Figures 3A and 3B. In particular, the design of the molding pockets 420a, 420b eliminates localized high-pressure areas (i.e., the relatively small-distance area 350 between the lands 332a and 332b, as shown in Figure 3B), which in turn reduces corresponding temperature spikes at the lands 432a, 432b. Because of this, and because the thickness of the glass ribbon 24 is uniform between and along the width of the glass ribbon 24 located within the molding pockets 420a, 420b, the temperature of the glass ribbon 24 within the molding pockets 420a, 420b may also be more uniform than that described with reference to Figures 3A and 3B, reducing localized temperature spikes.

[0106] 5A, an upper forming roll 500 is illustrated schematically in accordance with one or more embodiments shown and described herein. In embodiments, the upper forming roll 500 may be incorporated into the forming apparatus 20 of FIG. 1 and utilized in place of either the first upper forming roll 30a or the second upper forming roll 30b to increase heat extraction from the glass ribbon 24. In other embodiments, both the first upper forming roll 30a or the second upper forming roll 30b of FIG. 1 are replaced with the upper forming roll 500, such that a pair of upper forming rolls 500 is utilized in place of a pair of opposing upper forming rolls 30. Regardless of whether one or two of the upper forming rolls 500 are utilized, the forming apparatus 20 may include at least one pair of opposing lower rolls, such as a pair of opposing lower forming rolls 32, positioned downstream of the forming apparatus 20 to further extract heat from the glass ribbon 24 and / or reshape the glass ribbon 24 to a target size and shape.

[0107] The upper forming roll 500 extends along an axis 504 and is rotatable about the axis 504. The upper forming roll 500 includes a pair of opposing circular end faces 506, 508, with the entire axial length of the upper forming roll 500, as measured along the axis 504, defined between the pair of opposing circular end faces 506, 508. The upper forming roll 500 includes a cylindrical glass forming surface 510 that extends between the pair of opposing circular end faces 506, 508 of the upper forming roll 500. In the illustrated embodiment, the upper forming roll 500 includes a molding pocket 520 formed within the cylindrical glass forming surface 510. The molding pocket 520 extends circumferentially around the upper forming roll 500 such that it is generally cylindrical in shape.

[0108] 5B illustrates a detailed cross-sectional view of a portion of pocket 520 shown in FIG. 5A. Molding pocket 520 includes a plurality of distinct molding features 522 formed into and extending from a base 524 of molding pocket 520. Base 524 of molding pocket 520 is radially offset from cylindrical glass forming surface 510 by a depth d''. Depth d'' of molding pocket 520 is measured between base 524 and cylindrical glass forming surface 510.

[0109] The depth d" and geometry of the plurality of distinct mold-forming features 522 are selected to increase the surface area of ​​the mold-forming pocket 520 that can contact the glass ribbon 24, thereby increasing heat extraction from the portion of the glass ribbon 24 that contacts the mold-forming pocket 520. In embodiments, the depth d" may be at least 0.5 mm. In embodiments, the depth d" is at least 0.75 mm, at least 1 mm, at least 1.25 mm, at least 1.5 mm, at least 1.75 mm, at least 2 mm, at least 2.25 mm, at least 2.5 mm, at least 2.75 mm, at least 3 mm, at least 3.25 mm, at least 3.5 mm, at least 3.75 mm, at least 4 mm, at least 4.25 mm, at least 4.5 mm, at least 4.75 mm, at least 5 mm, at least 5.25 mm, at least 5.5 mm, at least 5.75 mm, or at least 6 mm. In embodiments, the depth d" is at most 10 mm. In embodiments, the depth d is 0.75 mm or more and 10 mm or less, 2 mm or more and 6 mm or less, 2.25 mm or more and 5.75 mm or less, 2.5 mm or more and 5.5 mm or less, 2.75 mm or more and 5.25 mm or less, 3 mm or more and 5 mm or less, 3.25 mm or more and 4.75 mm or less, 3.5 mm or more and 4.5 mm or less, or even 3.75 mm or more and 4.25 mm or less.

[0110] Referring again to FIG. 5C , which is a detailed view of a portion of the molding pocket 520 of the upper molding roll 500 of FIG. 5A , a plurality of distinct molding features 522 are present in a knurled pattern 530. The knurled pattern 530 is defined by a first array of grooves 532 and a second array of grooves 534. The first array of grooves 532 and the second array of grooves 534 each extend at least partially continuously around the upper molding roll 500. The second array of grooves 534 intersect the first array of grooves 532 to define a plurality of knurls 536 of the knurled pattern 530. As shown in FIG. 5A , the first array of grooves 532 and the second array of grooves 534 may each extend spirally around the circumference of the upper molding roll 500. Here, the first array of grooves 532 and the second array of grooves 534 are all oriented at the same helix angle measured relative to an axis parallel to the axis 504 of the upper forming roll 500. In other embodiments, at least one of the first array of grooves 532 and / or at least one of the second array of grooves 534 are oriented at different helix angles. In embodiments, each of the first array of grooves 532 is oriented at a helix angle of 35° or greater and 55° or less, or 40° or greater and 50° or less, and each of the second array of grooves 534 is oriented at a helix angle of 125° or greater and 145° or less, or 130° or greater and 140° or less. In some embodiments, each of the first array of grooves 532 is oriented at a helix angle of about 45°, and each of the second array of grooves 534 is oriented at a helix angle of about 135°. In the illustrated embodiment, each of the plurality of knurls 536 is truncated pyramidal in shape, although any one or more of the plurality of knurls 536 may have a different geometric shape.

[0111] As shown in FIG. 5B , each of the plurality of knurls 536 includes a peak 540, and each individual groove of the first array of grooves 532 and the second array of grooves 534 includes a groove base 542 that shares an extent with the base 524 of the mold-forming pocket 520. In embodiments, the groove base 542 may be at least partially curved, while in other embodiments, at least a portion of the groove base 542 is a flat surface. In the illustrated embodiment, the groove base 542 may include a curved surface defined by a radius when evaluated in cross section. The radius of the groove base 542 may vary, and in embodiments, the radius of the groove base 542 is at least 0.1 mm. The radius of the groove base 542 may be selected to help provide desired glass contact with the groove base 542, because it may be difficult for the molten glass to contact the groove base 542 if the molten glass is formed at an acute angle or too small a radius. In one example, the radius of curvature was 0.2 mm.

[0112] In embodiments, each of the plurality of knurls 536 comprises a height dimension H" measured between the peak 540 and the groove base 542. In the illustrated embodiment, the height dimension H" of each of the plurality of knurls may be equal to the depth d". However, the height dimension H" of one or more of the plurality of knurls 536 may be equal to or greater than the depth d". In embodiments, the height dimension H" of any one or more of the plurality of knurls 536 is equal to or greater than 2 mm and equal to or less than 10 mm. The peak 540 of each of the plurality of knurls 536 comprises a contact surface 544. In embodiments, the contact surface 544 may be flat when evaluated in cross-section, and in such embodiments, the contact surface 544 may be flush with the cylindrical glass forming surface 510. In embodiments, the contact surface 544 of at least one of the plurality of knurls 536 may be raised from the cylindrical glass forming surface 510. In embodiments, the height dimension H'' of the knurling 536 proximate the circular end faces 506, 508 is smaller than the height dimension H'' of the knurling 536 distal from the circular end faces 506, 508. In embodiments, the contact surface 544 of at least one of the plurality of knurlings 536 may be offset radially inward from (and recessed relative to) the cylindrical glass forming surface 510 toward the axis 504. In embodiments, the contact surface 544 may be at least partially curved when evaluated in cross section.

[0113] Each of the plurality of knurls 536 includes a plurality of side surfaces 550, which are defined by either the first array of grooves 532 or the second array of grooves 534. The side surfaces 550 of each of the plurality of knurls 536 may each be similarly angled such that each of the plurality of knurls 536 is oriented at a similar draft angle. However, one or more of the plurality of knurls 536 may be oriented at a different draft angle than the rest. Also, any one or more of the side surfaces 550 of a particular one of the plurality of knurls 536 may be oriented at a different angle than the rest of the side surfaces 550 of a particular one of the plurality of knurls 536. In the illustrated embodiment, each of the plurality of knurls 536 is oriented at a draft angle Θ'', which is the angle between the base 524 of the mold forming pocket 520 and the side surface 550 of the particular one of the plurality of knurls 536. In embodiments, the draft angle Θ" for each of the plurality of knurls 536 may be the same, while in other embodiments, the draft angle Θ" for at least one of the plurality of knurls 536 may be different from the others. In embodiments, the draft angle Θ" may be 90° or less, such as about 85° or less, about 80° or less, or even about 75° or less. In other embodiments, any one or more of the plurality of knurls 536 may be oriented at one or more different draft angles Θ". In embodiments, an angle φ is defined between adjacent knurls 536a, 536b of the plurality of knurls 536. In particular, the angle φ is defined as the angle between the side 550a of the knurl 536a and the side 550b of the adjacent knurl 536b. In embodiments in which the draft angle Θ" is the same for each of the plurality of knurls 536, the angle φ may also be uniform for each of the plurality of knurls 536. However, the draft angle Θ'' of any one or more of the plurality of knurls 536 may be different from the rest, and further, the angle φ between any pair of adjacent knurls 536a, 536b may be different from the rest.

[0114] In embodiments, the molding pocket 520 includes an axial pocket length 521 measured along the axis 504 from an innermost edge 560 of the knurling pattern 530 to an outermost edge 562 of the knurling pattern 530. In the illustrated embodiment, the molding pocket 520 extends less than the axial length 531 of the upper molding roll 500, the axial length 531 being measured along the axis 504 between a pair of opposing circular end faces 506, 508. Stated differently, the axial pocket length 521 of the molding pocket 520 may be shorter than the axial length 531 of the upper molding roll 500. In other embodiments, the molding pocket 520 may span the entire axial length 531 of the upper molding roll 500 such that the axial pocket length 521 of the molding pocket 520 is equal to the axial length 531 of the upper molding roll 500. In the illustrated embodiment, the molding pocket 520 is centrally located along the axial length 531 of the upper molding roll 500, but in other embodiments, the molding pocket 520 may be closer to the circular end face 506 than to the circular end face 508, or vice versa.

[0115] In some embodiments, the upper forming roll 500 may be a first upper forming roll positioned opposite a second upper forming roll such that a glass forming gap is defined between the upper forming roll 500 and the second upper forming roll. In some of these embodiments, the second upper forming roll may include a knurling pattern that is identical to the knurling pattern 530 of the upper forming roll 500, while in other embodiments, the knurling pattern of the second upper forming roll may differ from the knurling pattern 530 of the upper forming roll 500.

[0116] When the upper forming roll 500 is used in the glass forming apparatus 20 to form molten glass into a glass ribbon 24 (i.e., whether utilized in combination with a conventional upper forming roll, or when a pair of upper forming rolls 500 is utilized), heat is extracted from the glass ribbon 24 as the upper forming roll 500 contacts the surface of the glass ribbon 24, and the amount of heat extracted from the glass ribbon 24 depends on the amount of contact the upper forming roll 500 makes with the glass ribbon 24. Compared to conventional forming rolls, such as the pair of opposing upper forming rolls 30 described above in FIGS. 1 and 2A , the upper forming roll 500 has a greater amount of surface that contacts the glass ribbon 24 due to the design of the molding pocket 520, which includes a first array of grooves 532 and a second array of grooves 534 that collectively define a plurality of knurls 536 and groove bases 542 positioned between the plurality of knurls 536. Thus, the upper forming roll 500 is able to extract a relatively greater amount of heat from the glass ribbon 24. As evaluated in a cross section taken along axis 504, mold-forming pocket 520 contacts glass ribbon 24 along a contact line defined by each of contact surfaces 544, sides 550, and groove bases 542. Thus, when evaluated in cross section, the length of the contact line is equal to the sum of the lengths of each of contact surfaces 544, sides 550, and groove bases 542, which sum is greater than its axial pocket length 521 due to the incorporation of multiple knurls 536 positioned within mold-forming pocket 520. However, the contact line of mold-forming pocket 520 can be varied by adjusting various parameters, such as the dimensions of multiple knurls 536 (e.g., the dimensions of contact surfaces 544 and / or sides 550), the draft angle Θ″ at which multiple knurls 536 are oriented, the shape of multiple knurls 536, etc. Additionally, the contact line of mold-forming pocket 520 can be varied depending on whether it includes a majority or minority of multiple knurls 536.Compared to a pair of opposing upper forming rolls with molding pockets that do not have multiple molding features, the molding pockets 520 can provide at least the same amount of surface area in contact with the glass, and in embodiments, the amount of surface area of ​​the molding pockets 520 in contact with the glass is 101% to 1,000% greater than a pair of opposing upper forming rolls with molding pockets that do not have multiple molding features. [Example]

[0117] The embodiments described herein are further clarified by the following examples.

[0118] Testing and modeling were conducted to evaluate the embodiments of the opposing upper forming rolls 300 of Figures 3A and 3B (referred to herein as the "A Case") and the opposing upper forming rolls 300 of Figures 4A and 4B (referred to herein as the "B Case") to determine how effective each embodiment was in reducing the temperature difference between the thick and thin portions 212, 210 of the glass ribbon 24 compared to a standard setup (referred to herein as the "base case"). Testing and modeling were also conducted to evaluate a pair of opposing upper forming rolls, each configured as described in the upper forming rolls 500 of Figures 5A-5C (referred to herein as the "C Case"), to determine how effective the upper forming rolls were in reducing the temperature difference between the thick and thin portions 212, 210 of the glass ribbon 24 compared to the base case, the A Case, and the B Case.

[0119] For the base case, a pair of opposing upper forming rolls 30, as depicted in FIG. 2A, was modeled with a groove 200 formed in a second upper forming roll 30b. The first upper forming roll 30a was generally cylindrical. The nip distance 208 between the cylindrical glass forming surface 36a of the first upper forming roll 30a and the cylindrical glass forming surface 36b (outside of the groove 200) of the second upper forming roll 30b had a thickness dimension of 0.9 mm. The depth 202 of the groove 200 was 2.2 mm, such that the nip distance 206 between the base surface 204 of the groove 200 and the cylindrical glass forming surface 36a of the first upper forming roll 30a was 3.1 mm. The groove 200 was designed so that the total contact line along the pair of opposing upper forming rolls 30 was equal to 178.51 mm. In the base case, the total contact line is the sum of the first contact line (associated with the groove 200 of the second upper forming roll 30b) and the second contact line (associated with the first upper forming roll 30a). In particular, the first contact line is the length of the groove 200, evaluated in cross section, that contacts the thickened portion 212 of the glass ribbon 24, and the second contact line is the length of the first upper forming roll 30a that contacts the side of the glass ribbon 24 opposite the thickened portion 212. Here, the first contact line of the second upper forming roll 30b is equal to the sum of the lengths of the pair of side surfaces 203a, 203b and the base surface 204 of the groove 200, and the second contact line of the first upper forming roll 30a is equal to the axial pocket length 201. The groove 200 also has a cross-sectional area of ​​187.8 mm, measured between the pair of side surfaces 203a, 203b and the base surface 204 and a line corresponding to the cylindrical glass forming surface 36b. 2 Therefore, the total volume of the thick portions 212 of the glass ribbon 24 formed by the first upper forming roll 30a and the second upper forming roll 30b in the modeled base case was 7.51 mm for a segment of the glass ribbon 24 having a length of 40 mm in the draw direction. 3and the total contact area between the first upper forming roll 30a and the thick portion 212 of the formed glass ribbon 24 and between the second upper forming roll 30b and the thick portion 212 of the formed glass ribbon 24 is 71.4 mm for a segment of the glass ribbon having a length of 40 mm in the draw direction. 2 It should be noted that the total contact area refers to the sum of the contact area between the first upper forming roll 30a and the thickened portion 212 of the formed glass ribbon 24 having a length of 40 mm in the draw direction and the contact area between the second upper forming roll 30b and the thickened portion 212 of the formed glass ribbon 24 for the segment of the formed glass ribbon having a length of 40 mm in the draw direction.

[0120] For consistency, Cases A, B, and C were each modeled with a glass forming gap of 0.9 mm. In addition, mold forming pockets 320a, 320b, 420a, 420b, and 520 were modeled with a glass forming gap of 187.8 mm for each of Cases A, B, and C, as well as the base case. 2 (+ / - 1%) for Case A and Case B. Furthermore, the mold-forming pockets 320a, 320b, 420a, 420b were modeled to have a cross-sectional area of ​​7.51 mm for Case A and Case B, respectively, where the total volume of the thick portion of the formed glass ribbon segment having a length of 40 mm in the draw direction and the total contact area between the forming rolls and the thick portion of the glass ribbon were 7.51 mm for Case A and Case B, respectively. 3 and 71.4 mm 2 As noted herein, total contact area refers to the sum of the contact area between the first upper forming roll and the thick portion of the formed glass ribbon and the contact area between the second upper forming roll and the thick portion of the formed glass ribbon for a segment of the glass ribbon having a length of 40 mm in the draw direction.

[0121] For Case A, the molded pockets 320a, 320b have a total cross-sectional area of ​​approximately 187.1 mm, which is within approximately 1% of the base case, of all of the grooves 334a, 334b ​​in the molded pockets 320a, 320b. 2 The mold forming pockets 320a, 320b were modeled so that the total line of contact of the mold forming pockets 320a, 320b, which is the sum of the line of contact of the mold forming pockets 320a and 320b, was approximately 295.66 mm, which is approximately 166% of (i.e., greater than) the total line of contact of the base case. The draft angle Θ of each of the multiple lands 332a, 332b was modeled at 75°. In summary, Case A was modeled based on the premise that increasing the total line of contact within the mold forming pockets 320a, 320b increases heat transfer within the thick portion 212 of the glass ribbon 24, lowering the temperature of the thick portion 212 relative to the base case and reducing the temperature difference between the thick portion 212 and the thin portion 210 relative to the base case. However, in this Case A model, the thickness of the thick portion 212 of the glass ribbon 24 varied from approximately 1.5 mm to approximately 4.3 mm along the axial pocket lengths 321a, 321b, and the thickness of the thick portion 212 of the glass ribbon was non-uniform.

[0122] For Case B, the molded pockets 420a, 420b have a cross-sectional area defined between a pair of opposing upper forming rolls 300 along an axial pocket length 421b of approximately 186.4 mm, which is within approximately 1% of the base and A cases. 2The mold forming pockets 420a, 420b were also modeled so that the total contact line length of the mold forming pockets 420a, 420b, which is the sum of the contact line of the mold forming pockets 420a and 420b, was approximately 270.3 mm, which is approximately 151% (i.e., greater than) the total contact line length of the base case (but less than Case A). In Case B, the draft angle Θ' was set to 75°. Case B was modeled to maintain a constant thickness of 2 mm for the thick portion 212 of the glass ribbon 24 manipulated by the mold forming pockets 420a, 420b and also to eliminate sharp edges contacting the glass. As a result, the glass ribbon 24 in Case B had a more uniform pressure and temperature distribution compared to Case A, in which the glass ribbon 24 exhibited temperature and pressure spikes in region 350 and relatively lower pressures and temperatures at corners 352 a, 352 b. Additionally, the modeled Case B exposed the glass ribbon 24 to a lower absolute pressure than Case A, and Case B also reduced the occurrence of stagnant flow zones that could occur at corners 352 a, 352 b in Case A due to the localized lower temperatures present at corners 352 a, 352 b.

[0123] For Case C, the molding pockets 520 of each pair of rollers have a total volume of the thick portions of the segments of the formed glass ribbon having a length of 40 mm in the drawing direction, which is about 7.7 cm , which is within about 2% of the base case. 3 and the mold forming pocket 520 is modeled such that the total contact area between the forming rolls and the thick portion of the glass ribbon is 174.8 cm, which is about 245% of (i.e., greater than) the total contact area of ​​the base case for a segment of the formed glass ribbon having a length of 40 mm in the draw direction. 2 For case C, the draft angle Θ'' was set to 75°. Also, for case C, the depth d'' was 2.13 mm.

[0124] Example 1 FIG. 6 is a chart graphically illustrating thermal modeling results at the nip for the base case, Case A, and Case B. In particular, the chart in FIG. 6 shows representative examples of average temperatures along the width W of the glass ribbon 24 at the nip for the base case (see line 602), Case A (see line 604), and Case B (see line 606). As expected, the base case exhibited the highest average temperature along the width W of the glass ribbon 24, while Cases A and B both exhibited significantly lower average and median temperatures along the width W of the glass ribbon 24 compared to the base case. Additionally, Case A exhibited a large spike in average temperature due to sharp corners and glass thickness variations across the width W of the glass ribbon 24; the spike in average temperature corresponded to region 350 shown in FIG. 3B . Case B exhibited some temperature fluctuations, but they were not as severe as those of Case A.

[0125] Example 2 Table 1 below includes the results of the volumetric thermal modeling utilized to analyze the base case, Case A, Case B, and Case C. In particular, because the mold-forming pocket 520 in Case C produced a glass ribbon with a non-uniform cross-section when evaluated along the draw direction 31, which stretched the glass ribbon 24, a volumetric method was used to compare the thermal performance among the four cases. Despite Case C having a non-uniform cross-section when evaluated at different slices taken upstream or downstream, the glass volume in each slice was nearly identical (within + / - 2%). For better comparison and integration of results, a 10 mm strip of the glass ribbon 24 below the nip was used as the integration region, and the temperature was integrated over the volume of the thick portion 212 and the thin portion 210. Because the temperature environment in which glass forming occurs is significantly lower than the temperature of the glass forming process, the median temperature of the glass ribbon 24 was also determined. The volumetric average temperatures of the thin portion 210 and the thick portion 212 of the glass ribbon 24 are recorded in Table 1 below. [Table 1]

[0126] Table 1 shows the average temperature difference (dT avg ) for the base case, as shown in Table 1. avg is 170.49℃, and dT for case A avg is approximately 152.12°C, and dT for case B avg is about 134.25°C, and dT for the C case avg was approximately 100.07°C. Therefore, dT in Case A avg is about 89.2% of the base case, and dT avg is about 78.74% of the base case, and dT avg was about 58.7% of the base case. These results suggest that the dT of the base case may lead to improved attributes of the glass ribbon 24 (i.e., reduced stress, sheet bow, and curtain warp) upon rolling. avg This is a significant reduction.

[0127] Thus, Table 1 illustrates that the embodiments disclosed herein can significantly reduce the temperature difference between the thick portions 212 and thin portions 210 of the glass ribbon 24, which may not only improve the above-noted attributes of the glass ribbon 24, but also enable the production of glass ribbons having thick portions and portions with large variations in thickness between the thick and thin portions, and may achieve acceptable ribbon attributes without significantly modifying the forming process.

[0128] Example 3 Figure 7 shows the dT avg 7 shows a graph of the relationship between the ratio of the total contact area of ​​the thin portions of the formed glass ribbon to the volume of the thick portions of the formed glass ribbon for a 40 mm length of the glass ribbon in the draw direction. As can be seen from FIG. 7, increasing the ratio of the total contact area of ​​the thick portions of the formed glass ribbon to the volume of the thick portions of the formed glass ribbon generally increases dTavg However, the ratio of the total contact area to the volume of the thick part of the glass ribbon is dT avg As previously mentioned, the thickness of the thickened portion 212 of the glass ribbon 24 and the pressure exerted on the glass ribbon 24 also affect dT avg and the same total contact area to volume ratio dT (in the thick portion 212 of the glass ribbon 24) avg All of these factors can be taken into consideration when designing the molded pocket to further reduce .

[0129] The molding pockets disclosed herein may be incorporated into one or more of a pair of forming rolls. The molding pockets disclosed herein may comprise a plurality of distinct molding features. The plurality of distinct molding features may include a plurality of lands spaced apart by a plurality of grooves. The geometry of the lands and grooves may be varied to affect how much of the molding pocket contacts the glass ribbon, thereby affecting the thermal profile of the glass ribbon formed by the molding pocket. The depth at which the grooves are formed may be at least 0.5 mm, but may be increased, and / or one or more of the grooves may have a different depth than the other grooves. The draft angle at which the lands are oriented may also be varied; all of the lands may be oriented at the same draft angle, or one or more of the lands may be oriented at a different draft angle than the remaining lands. The edges of the lands may be rounded, beveled, or sharp. In some embodiments, all of the lands may have the same type of edge, while in other embodiments, one or more of the edges may be different from the others. The grooves may be equally spaced, or the spacing of one or more of the grooves may be different from the rest. In some embodiments, all of the grooves may extend in the same direction, such as generally circumferentially around the roll, while in some embodiments, at least one groove may extend in a different direction than the other grooves. For example, the grooves may include a first array of grooves and a second array of grooves that extend in a different direction than the first array of grooves, with the second array of grooves intersecting the first array of grooves to define a plurality of knurls.

[0130] The mold-forming pockets disclosed herein can be incorporated to reduce temperature differentials experienced across the glass ribbon and increase the viscosity of the glass ribbon prior to the turning section, thereby reducing curtain warp, sheet bow, and stress in the glass ribbon during forming. The mold-forming pockets are formed into the cylindrical glass forming surface of the associated forming roll to a depth of at least 0.5 mm and may include multiple distinct mold-forming features extending from the base of the mold-forming pocket such that the mold-forming pocket contacts a greater amount of the glass ribbon during forming compared to conventional forming rolls. By contacting a greater amount of the glass ribbon, the mold-forming pockets disclosed herein are operable to extract more heat from the glass ribbon than conventional forming rolls. When the glass ribbon to be formed is a variable thickness glass ribbon having thin and thick portions, the molding pockets and multiple separate molding features may be formed at locations on the associated forming roll(s) to increase surface contact with the thick portions of the variable thickness glass ribbon; by increasing the amount of surface contact with the thick portions, the molding pockets and multiple separate molding features can reduce the temperature difference of the variable thickness glass ribbon (i.e., the temperature difference between the thick and thin portions). In applications where the glass ribbon to be formed is of uniform thickness, embodiments described herein can be utilized to provide greater heat extraction before the turning section, thereby facilitating the formation of a thicker glass ribbon of uniform thickness, or a glass ribbon of equal thickness with a higher flow density.

[0131] It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments described herein without departing from the spirit or scope of the claimed subject matter. Thus, it is intended that the present specification cover modifications and variations of the various embodiments described herein, provided that such modifications and variations come within the scope of the appended claims and their equivalents.

Claims

1. 1. An apparatus for roll-forming a glass ribbon or a glass-ceramic ribbon, comprising: a molten glass delivery device; a pair of opposing upper forming rolls, each upper forming roll comprising a pair of circular end faces and a cylindrical glass forming surface extending between the pair of circular end faces, the pair of opposing upper forming rolls defining a glass forming gap between the cylindrical glass forming surfaces, the glass forming gap being positioned below the molten glass delivery device and configured to receive a flow of molten glass from the molten glass delivery device such that the flow of molten glass is thinned between the pair of opposing upper forming rolls to form a molded glass ribbon, at least one upper forming roll of the pair of opposing upper forming rolls comprising a molding pocket formed in the cylindrical glass forming surface of the at least one upper forming roll, the molding pocket comprising a plurality of distinct molding features extending from a base of the molding pocket, the base of the molding pocket comprising a depth measured from the cylindrical glass forming surface of at least 0.5 mm; a pair of opposing lower rolls defining a glass sizing gap therebetween, the glass sizing gap being located below the glass forming gap and configured to receive the molded glass ribbon such that the molded glass ribbon is reshaped to a target thickness by the pair of opposing lower rolls.

2. 2. The apparatus of claim 1, wherein the plurality of distinct molding features comprises a plurality of lands extending from the base of the molding pocket, the lands extending continuously circumferentially around the at least one upper molding roll and spaced apart by a plurality of grooves defined between each of the lands.

3. 3. The apparatus of claim 2, wherein the plurality of lands are equally spaced apart by the plurality of grooves.

4. the cylindrical glass forming surface of a first upper forming roll of the pair of opposing upper forming rolls includes a first mold forming pocket with a plurality of first lands extending from the base of the first mold forming pocket and spaced apart by a plurality of first grooves defined between the first lands; 3. The apparatus of claim 2, wherein the cylindrical glass forming surface of a second upper forming roll of the pair of opposing upper forming rolls includes a second molding pocket, and a plurality of second lands extending from the base of the second molding pocket and spaced apart by a plurality of second grooves defined between the plurality of second lands.

5. the base of the first molded pocket comprises a plurality of first base segments, each of the plurality of first lands being positioned between a pair of the plurality of first base segments, and each of the plurality of first lands extending radially toward one of the plurality of second grooves so as to face one of the second base segments of the second molded pocket; 5. The apparatus of claim 4, wherein the base of the second molded pocket comprises a plurality of second base segments, each of the plurality of second lands is positioned between a pair of the plurality of second base segments, and each of the plurality of second lands extends radially toward one of the plurality of first grooves so as to face one of the first base segments of the first molded pocket.

6. 5. The apparatus of claim 4, wherein each of the plurality of first lands and each of the plurality of second lands comprises a land surface and a pair of side surfaces on either side of the land surface, each of the pair of side surfaces being oriented at a draft angle of less than 90° relative to the base of the first molded pocket or the second molded pocket associated with each of the pair of side surfaces.

7. The apparatus of claim 6 , wherein the draft angle of each of the plurality of first lands is equal to the draft angle of each of the plurality of second lands.

8. 7. The apparatus of claim 6, wherein the plurality of first lands and the plurality of second lands each have a height dimension equal to the depth of the respective molded pocket, the height dimension of the plurality of first lands being measured between the land surface of the plurality of first lands and the base of the first molded pocket, and the height dimension of the plurality of second lands being measured between the land surface of the plurality of second lands and the base of the second molded pocket.

9. 7. The apparatus of claim 6, wherein the land surface of each of the plurality of first lands is coaxial with the first upper forming roll of the pair of opposing upper forming rolls, and the land surface of each of the plurality of second lands is coaxial with the second upper forming roll of the pair of opposing upper forming rolls.

10. 6. The apparatus of claim 5, wherein each of the plurality of first base segments is coaxial with the first upper forming roll of the pair of opposing upper forming rolls, and each of the plurality of second base segments is coaxial with the second upper forming roll of the pair of opposing upper forming rolls.

11. 6. The apparatus of claim 5, wherein the plurality of first lands of the first molded pocket are equally spaced apart by the plurality of first base segments, and the plurality of second lands of the second molded pocket are equally spaced apart by the plurality of second base segments.

12. The apparatus of claim 4 , wherein the plurality of first lands in the first molded pocket is greater in number than the plurality of second lands in the second molded pocket.

13. The apparatus of claim 12 , wherein the plurality of first lands in the first molded pocket are equal in number to the plurality of second grooves in the second molded pocket.

14. the cylindrical glass forming surface of a first upper forming roll of the pair of opposing upper forming rolls includes a first mold forming pocket; the cylindrical glass forming surface of a second upper forming roll of the pair of opposing upper forming rolls includes a second mold forming pocket; the plurality of lands of the first molded pocket include a plurality of first lands extending from the base of the first molded pocket, the plurality of first lands being spaced apart by a plurality of first grooves defined between the plurality of first lands; the plurality of lands of the second molded pocket include a plurality of second lands extending from the base of the second molded pocket, the plurality of second lands being spaced apart by a plurality of second grooves defined between the plurality of second lands; the base of the first molded pocket comprises a plurality of first base segments, each first land of the plurality of first lands being positioned between a pair of the plurality of first base segments; the base of the second molded pocket comprises a plurality of second base segments, and each second land of the plurality of second lands is positioned between a pair of the plurality of second base segments; each of the plurality of first lands of the first molding pocket is raised from the cylindrical glass forming surface of a first upper forming roll of the pair of opposing upper forming rolls; 3. The apparatus of claim 2, wherein each of the plurality of second lands of the second molding pocket is raised from the cylindrical glass forming surface of the second upper forming roll of the pair of opposing upper forming rolls.

15. 15. The apparatus of claim 14, wherein each of the plurality of first base segments and each of the plurality of second base segments is at least partially curved when evaluated in a plane extending through a first axis of rotation of the first upper forming roll of the pair of opposing upper forming rolls and a second axis of rotation of the second upper forming roll of the pair of opposing upper forming rolls.

16. 15. The apparatus of claim 14, wherein each of the plurality of first lands of the first molded pocket extends radially toward one of the plurality of second base segments of the second molded pocket, and each of the plurality of second lands of the second molded pocket extends radially toward one of the plurality of first base segments of the first molded pocket.

17. 17. The apparatus of claim 16, wherein each of the plurality of first lands extends radially beyond a centerline of the glass forming gap, each of the plurality of second lands extends radially beyond the centerline of the glass forming gap, each of the plurality of first lands is raised from the plurality of second lands of the second upper forming roll of the pair of opposing upper forming rolls, and each of the plurality of second lands is raised from the plurality of first lands of the first upper forming roll of the pair of opposing upper forming rolls.

18. 18. The apparatus of claim 17, wherein the plurality of first grooves defined in the first molded pocket include an innermost groove, an outermost groove, and a plurality of central grooves, and the plurality of second lands in the second molded pocket include an innermost land extending radially to the innermost groove, an outermost land extending radially to the outermost groove, and a plurality of central lands extending radially to each central groove of the plurality of central grooves.

19. each of the plurality of first lands comprises a first land surface and a height dimension measured between the first land surface and the base of the first mold forming pocket, the height dimension of each of the plurality of first lands being greater than the sum of the depth and the glass forming gap such that each of the plurality of first lands is raised from the cylindrical glass forming surface of the second upper forming roll of the pair of opposing upper forming rolls; 18. The apparatus of claim 17, wherein each of the plurality of second lands comprises a second land surface and a height dimension measured between the second land surface and the base of the second mold forming pocket, the height dimension of each of the plurality of second lands being greater than the sum of the depth and the glass forming gap such that each of the plurality of second lands is raised from the cylindrical glass forming surface of the first upper forming roll of the pair of opposing upper forming rolls.

20. 15. The apparatus of claim 14, wherein each of the plurality of first lands comprises a first land surface that transitions with a rounded edge to an associated one of the plurality of first base segments, and each of the plurality of second lands comprises a second land surface that transitions with a rounded edge to an associated one of the plurality of second base segments.

21. 15. The apparatus of claim 14, wherein each of the plurality of first lands includes a first land surface defined by a first constant arc, and each of the plurality of second lands includes a second land surface defined by a second constant arc.

22. 15. The apparatus of claim 14, wherein each of the plurality of first lands and each of the plurality of second lands comprises a cylindrical land surface having a pair of side surfaces on either side of the cylindrical land surface.

23. 15. The apparatus of claim 14, wherein each of the plurality of first lands and each of the plurality of second lands comprises a land surface and a pair of side surfaces on either side of the land surface, each of the pair of side surfaces being oriented at a draft angle of less than 90° with respect to the cylindrical glass forming surface associated with each of the pair of side surfaces.

24. The apparatus of claim 14 , wherein the plurality of first lands in the first molded pocket is greater in number than the plurality of second lands in the second molded pocket.

25. 25. The apparatus of claim 24, wherein the plurality of first lands in the first molded pocket are equal in number to the plurality of second grooves associated with the second molded pocket.

26. 2. The apparatus of claim 1, wherein the plurality of distinct molded features comprises a knurling pattern defined by a first array of grooves and a second array of grooves, the first array of grooves and the second array of grooves extending at least partially continuously around at least one of the pair of opposing upper molding rolls, the second array of grooves intersecting the first array of grooves to define a plurality of knurls of the knurling pattern, each of the plurality of knurls comprising a peak, each distinct groove of the first array of grooves and the second array of grooves comprising a groove base, and each of the plurality of knurls comprising a height dimension measured between the peak and the groove base.

27. 27. The apparatus of claim 26, wherein the height dimension is equal to the depth.

28. 27. The apparatus of claim 26, wherein the first array of grooves and the second array of grooves each extend helically around the circumference of the at least one of the pair of opposing upper forming rolls.

29. 27. The apparatus of claim 26, wherein the peak of each of the plurality of knurls comprises a flat contact surface.

30. 30. The apparatus of claim 29, wherein the flat contact surface of each of the plurality of knurls is flush with the cylindrical glass forming surface.

31. 27. The apparatus of claim 26, wherein each of the plurality of knurls is truncated pyramidal in shape.

32. 27. The apparatus of claim 26, wherein the molded pocket molded on the at least one of the pair of opposing upper forming rolls extends the entire axial length of the at least one of the pair of opposing upper forming rolls.

33. 27. The apparatus of claim 26, wherein the knurling pattern includes a first knurling pattern molded into the cylindrical glass forming surface of a first upper forming roll of the pair of opposing upper forming rolls and a second knurling pattern molded into the cylindrical glass forming surface of a second upper forming roll of the pair of opposing upper forming rolls.

34. 34. The apparatus of claim 33, wherein the first knurling pattern and the second knurling pattern are identical.

35. The apparatus of claim 1 , wherein the axial length of the molding pocket is less than the axial length of the at least one of the pair of opposing upper molding rolls.

Images