WO2013009293A1

WO2013009293A1 - Wire pulling rolls for use in glass manufacturing processes and glass manufacturing processes incorporating the same

Info

Publication number: WO2013009293A1
Application number: PCT/US2011/043629
Authority: WO
Inventors: Ralph A. Langensiepen
Original assignee: Corning Incorporated
Priority date: 2011-07-12
Filing date: 2011-07-12
Publication date: 2013-01-17
Also published as: CN103648993A; TW201305068A; JP2014524879A; KR20140039273A

Abstract

In one embodiment, a pulling roll for drawing glass sheet includes a shaft member and a brush assembly. The brush assembly includes a plurality of loops formed from metal wire. Each loop overlaps an adjacent loop and is parallel to and non-concentric with the adjacent loop. The brush assembly is spirally wound on the shaft member such that the plurality of loops project from a surface of the shaft member and a plane of each loop of the plurality of loops is non-parallel with a long axis of the shaft member. The brush assembly forms a cover of the pulling roll for contacting a planar surface such that the planar surface is tangential to at least a portion of the plurality of loops of the brush assembly when the cover contacts the planar surface. Glass manufacturing processes incorporating the pulling rolls are also disclosed.

Description

WIRE PULLING ROLLS FOR USE IN GLASS MANUFACTURING PROCESSES AND GLASS MANUFACTURING PROCESSES INCORPORATING THE SAME

BACKGROUND Field

[0001] The present specification generally relates to pulling rolls for use in the manufacture of glass sheets and, more specifically, to pulling rolls comprising wire loop brush assemblies for use in glass manufacturing processes.

Technical Background

[0002] Pulling rolls are used in the manufacture of sheet glass to apply tension to a ribbon or web of glass from which individual sheets of glass are formed. The amount of tension applied by the pulling rolls to the glass is utilized to control the nominal thickness of the glass as the glass is drawn from molten glass, such as in an overflow downdraw fusion process, as described in U.S. Patent Nos. 3,338,696 and 3,682,609, or in similar glass manufacturing processes.

[0003] Pulling rolls are generally designed to contact the glass web at its outer edges, usually in an area just inboard of the thickened beads that form at the very edges of the glass web. Because the pulling rolls are in direct contact with the surface of the glass web, damage to the surface of the glass can occur due to the wear characteristics of the pulling roll material. For example, glass particles can become embedded in the surface of the pulling roll resulting in damage to the glass as the pulling rolls contact the glass.

[0004] Similarly, the pulling roll may shed particulate matter if the material of the pulling roll degrades with use at the elevated temperatures of the glass drawing process. This particulate matter may become embedded in the soft glass thereby fomiing defects in the glass. Similarly, particulate matter generated from the glass drawing process (e.g., debris, dust, glass shards and the like) may become embedded in the surface of the pulling roll thereby creating repetitive defects in the glass web. Damage to the glass web caused by any of these mechanisms may result in the glass being discarded thereby decreasing manufacturing efficiencies and increasing costs.

[0005] Accordingly, alternative designs for pulling rolls for use in glass manufacturing processes are needed.

SUMMARY

[0006] The embodiments described herein relate to pulling rolls for use in glass drawing processes which reduce the occurrence of defects in glass sheets drawn with the pulling rolls. Also disclosed are methods for forming glass sheets utilizing pulling rolls which mitigate the occurrence of defects in the glass sheets.

[0007] According to one embodiment, a pulling roll for reducing the occurrence of defects in glass sheets includes a shaft member and a brush assembly having a plurality of loops formed from metal wire. Each loop of the plurality of loops may overlap an adjacent loop and is parallel to and non-concentric with the adjacent loop. The brush assembly may be spirally wound on the shaft member such that the plurality of loops project from a surface of the shaft member and a plane of each loop of the plurality of loops is non-parallel with a long axis of the shaft member. The brush assembly forms a cover of the pulling roll for contacting a planar surface such that the planar surface is tangential to at least a portion of the plurality of loops of the brush assembly when the cover contacts the planar surface.

[0008] In another embodiment, a pulling roll for reducing the occurrence of defects in glass sheets includes a shaft member and a brush assembly. The brush assembly may include a single metallic wire formed into a plurality of loops, wherein each loop of the plurality of loops overlaps an adjacent loop and is parallel to and non-concentric with the adjacent loop. The brush assembly may further include a holding member having a channel. The plurality of loops may be secured in the channel of the holding member. The brush assembly may be spirally wound on the shaft member such that the plurality of loops project from a surface of the shaft member and a plane of each loop of the plurality of loops is non-parallel with a long axis of the shaft member. The brush assembly forms a cover of the pulling roll for contacting a planar surface such that the planar surface is tangential to at least a portion of the plurality of loops of the brush assembly when the cover contacts the planar surface.

[0009] In yet another embodiment, a method for forming a glass sheet with reduced defects may include melting glass batch materials to form molten glass and forming the molten glass into a glass sheet. At least a first surface of the glass sheet may be contacted with at least one pulling roll to convey the glass sheet in a downstream direction. The at least one pulling roll may include a shaft member and a brush assembly. The brush assembly may include a plurality of loops formed from metal wire. Each loop of the plurality of loops may overlap an adjacent loop and be oriented in parallel to and non-concentric with the adjacent loop. The brush assembly may be spirally wound on the shaft member such that the plurality of loops project from a surface of the shaft member and a plane of each loop of the plurality of loops is non- parallel with a long axis of the shaft member. At least a portion of the plurality of loops of the pulling roll may be tangential to the first surface of the glass sheet when the pulling roll contacts the first surface of the glass sheet.

[0010] Additional features and advantages of the present disclosure will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0011] It is to be understood that 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 character 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 the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1A schematically depicts a glass drawing apparatus for forming glass sheets according to one or more embodiments shown and described herein;

[0013] FIG. IB schematically depicts a cross section of a draw assembly for use in drawing a glass sheet;

[0014] FIG. 2 schematically depicts a cross section of a pulling roll formed from wire loops, according to one or more embodiments shown and described herein;

[0015] FIG. 3 schematically depicts a cross section of the pulling roll of FIG. 2 according to one or more embodiments shown and described herein;

[0016] FIG. 4A schematically depicts a cross section of the pulling roll of FIG. 2 according to another embodiment shown and described herein;

[0017] FIG. 4B schematically depicts a cross section of the pulling roll of FIG. 2 according to another embodiment shown and described herein;

[0018] FIG. 5A schematically depicts the formation of the plurality of wire loops of the brush assembly of the pulling roll of FIG. 2 according to one or more embodiments shown and described herein;

[0019] FIG. 5B schematically depicts a plurality of loops of metal wire for forming the brush assembly of the pulling roll of FIG. 2 according to one or more embodiments shown and described herein;

[0020] FIG. 5C schematically depicts the wire brush assembly of the pulling roll of FIG. 2 prior to installation on the shaft member of the pulling roll;

[0021] FIG. 5D schematically depicts a cross section of the brush assembly of FIG. 5C according to one or more embodiments shown and described herein; [0022] FIG. 6 schematically depicts a brush assembly for a pulling roll having discrete loops formed from individual pieces of metallic wire;

[0023] FIG. 7 schematically depicts drawing a glass sheet utilizing a pair of pulling rolls constructed according to one embodiment described herein; and

[0024] FIG. 8 schematically depicts drawing a glass sheet utilizing a pulling roll constructed according to another embodiment described herein.

DETAILED DESCRIPTION

[0025] Reference will now be made in detail to various embodiments of pulling rolls for use in the manufacture of glass sheets and glass manufacturing processes incorporating the same. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. One embodiment of a pulling roll is schematically depicted in FIG. 2. The pulling roll generally comprises a shaft member and a brush assembly having a plurality of loops formed from metal wire. The brush assembly may be spirally wound on the shaft member such that the plurality of loops project from a surface of the shaft member and a plane of each loop of the plurality of loops is non-parallel with a long axis of the shaft member. The brush assembly forms a cover of the pulling roll for contacting a planar surface such that the planar surface is tangential to at least a portion of the plurality of loops of the brush assembly when the cover contacts the planar surface. The pulling roll and methods for using the pulling roll to draw glass sheet will be described in more detail herein with specific reference to the appended drawings.

[0026] Glass sheet materials may generally be formed by melting glass batch materials to form molten glass and thereafter forming the molten glass into a glass sheet. Exemplary processes include the float glass process, the slot draw process and the fusion downdraw process. In each of these processes, one or more pulling rolls may be utilized to contact the glass sheet and convey the glass sheet in a downstream direction.

[0027] Referring to FIG. 1A by way of example, an exemplary glass manufacturing apparatus 100 for fomiing glass sheet material from molten glass is schematically depicted in which a fusion draw machine is used to form the molten glass into glass sheets. The glass manufacturing apparatus 100 includes a melting vessel 101, a fining vessel 103, a mixing vessel 104, a delivery vessel 108, and a fusion draw machine (FDM) 120. Glass batch materials are introduced into the melting vessel 101 as indicated by arrow 102. The batch materials are melted to form molten glass 106. The fining vessel 103 has a high temperature processing area that receives the molten glass 106 from the melting vessel 101 and in which bubbles are removed from the molten glass 106. The fining vessel 103 is fluidly coupled to the mixing vessel 104 by a connecting tube 105. That is, molten glass flowing from the fining vessel 103 to the mixing vessel 104 flows through the connecting tube 105. The mixing vessel 104 is, in turn, fluidly coupled to the delivery vessel 108 by a connecting tube 107 such that molten glass flowing from the mixing vessel 104 to the delivery vessel 108 flows through the connecting tube 107.

[0028] The delivery vessel 108 supplies the molten glass 106 through a downcomer 109 into the FDM 120. The FDM 120 comprises an enclosure 122 in which an inlet 110, a foirning vessel 111 and at least one draw assembly 150 are positioned. As shown in FIG. 1, the molten glass 106 from the downcomer 109 flows into an inlet 110 which leads to the foirning vessel 111. The foirning vessel 111 includes an opening 112 that receives the molten glass 106 which flows into a trough 113 and then overflows and runs down two converging sides 114a and 114b before fusing together at a root, where the two sides join, before being contacted and drawn in a downstream direction 151 by the draw assembly 150 to form a continuous glass sheet 148.

[0029] Referring to FIG. IB, a cross section of the draw assembly 150 is schematically depicted. As shown in FIG. IB, the draw assembly 150 generally comprises a pair of opposed pulling rolls 200a, 200b which contact the glass sheet 148 on opposite sides. Accordingly, it should be understood that the glass sheet 148 is impinged between the pulling rolls 200a, 200b. The pulling rolls 200a, 200b may be powered (i.e., the pulling rolls 200a, 200b are actively rotated and thus impart a drawing force which conveys the glass sheet 148 in the downstream direction 151) or passive (i.e., the pulling rolls 200a, 200b contact the glass sheet 148 and stabilize the glass sheet as it is drawn in the downstream direction 151 by other pulling rolls).

[0030] While the pulling rolls 200a, 200b have been described herein as being used in conjunction with an apparatus which utilizes a fusion draw machine to form the glass sheet, it should be understood that the pulling rolls may be used with similar processes in which glass batch materials are melted to form molten glass and the molten glass is then formed into a glass sheet and drawn with pulling rolls. By way of example and not limitation, the pulling rolls described herein may also be utilized in conjunction with up-draw processes, slot-draw processes, float-draw processes and other, similar glass drawing processes.

[0031] As briefly described hereinabove, the pulling rolls used in the aforementioned processes are in direct contact with the glass sheet and, as such, damage to the surface of the glass can occur due to the wear characteristics of the pulling roll material. For example, glass particles can become embedded in the surface of the pulling roll resulting in damage to the glass as the pulling rolls contact the glass. Similarly, the pulling roll may degrade with prolonged use at elevated temperatures and shed particulate matter. This particulate matter may become embedded in the soft glass, thereby forming defects in the glass. The pulling rolls described herein utilize metal wire loops to contact the glass sheet and thus have a greater stability at elevated temperatures and do not readily degrade after prolonged use or shed particulate matter. Moreover, the open-loop structure of the pulling rolls allows particulate matter to be readily absorbed into the body of the pulling roll rather than embedded into the surface of the pulling roll.

[0032] Referring now to FIGS. 2 and 3, an exemplary pulling roll 200 for use in a glass manufacturing process is schematically depicted. The pulling roll 200 generally includes a shaft member 204 around which a brush assembly 250 is wound. The brush assembly is generally formed from a plurality of wire loops which form a compliant cover around the shaft member. In the embodiments described herein, the shaft member 204 of the pulling roll 200 is generally cylindrical in shape and may be formed from a metallic material suitable for use at elevated temperatures (i.e., temperatures greater than about 700°C or even 800°C) without loss of mechanical strength. Suitable materials include, for example, stainless steel, nickel- based alloys and other similar materials commonly used in high temperature applications.

[0033] In the exemplary embodiment of the pulling roll 200 depicted in FIG. 2, the shaft member 204 includes threads 205 on one end while the opposing end is formed with a shoulder 203 which assists in retaining the brush assembly 250 on the shaft member 204. The shoulder 203 may also facilitate securing the pulling roll 200 to a frame or a mechanism for actively rotating the pulling roll 200.

[0034] Referring now to FIGS. 2, 3, and 5B, the pulling roll 200 further comprises a brush assembly 250 which is spirally wrapped around the shaft member 204 to form a compliant, resilient cover. The brush assembly 250 generally comprises a plurality of wire loops 218. The plurality of loops 218 of the brush assembly 250 are shown in an "unwound" state in FIG. 5B. As depicted in FIG. 5B, each loop 220 of the plurality of wire loops 218 overlaps an adjacent loop but is non-concentric with the adjacent loop. Moreover, the plane of each individual loop 220 (i.e., the plane in which the loop 220 lies) is generally parallel with the plane of an adjacent loop. However, directly adjacent loops are generally non-coplanar with one another. In some embodiments, none of the loops 220 in the plurality of loops 218 are coplanar.

[0035] Still referring to FIG. 5B, in the embodiments described herein, the plurality of loops are formed such that each loop has a loop diameter D in the range from about 2.5 cm to about 5.08 cm. In some embodiments, all the loops 220 of the plurality of loops 218 have the same diameter. However, it is contemplated that the brush assembly may be constructed from a plurality of loops having different diameters.

[0036] As noted above, adjacent loops of the brush assembly 250 overlap with one another. The overlap between the loops provides the pulling roll with a uniform contact surface as the pulling roll is rotated which, in turn, enables the pulling roll to exert a drawing force on the planar surface of a glass sheet. In general, the center-to-center spacing S between adjacent loops is at least 0.25 cm. For example, in the embodiments described herein where the plurality of loops have a loop diameter D in the range from about 2.5 cm to about 5.08 cm, the center- to -center spacing S between adjacent loops is greater than or equal to 0.25 cm and less than or equal to about 1.3 cm.

[0037] The plurality of loops 220 of the brush assembly 250 are formed from metallic wire which is suitable for use at elevated temperatures without undergoing significant loss of mechanical properties and/or oxidation which would contaminate the glass drawing process and degrade the pulling roll. For example, suitable materials from which the plurality of loops 220 are formed include, without limitation, 304 stainless steel, 310 stainless steel, 434 stainless steel, Inconel 625 nickel-based alloy, Haynes 230 alloy, 800 HT alloy, HR-120 alloy, PM 2000 alloy, Nicrofer 602CA alloy, MA956 alloy, Kanthal, Fecralloy steel JA13, Stellite series steels, and rare-earth doped nickel aluminum alloys. However, it should be understood that other metallic materials may be used.

[0038] Alternatively or additionally, the metallic wire may be coated with one or more coatings or surface treatments which mitigate the oxidation of the metallic wire (i.e., an oxidation resistant coating) and prevents the degradation of the pulling roll after exposure to elevated temperatures. Suitable coatings include, without limitation, aluminum oxide, zirconia, and/or similar coatings which prevent the oxidation of metallic materials at elevated temperatures.

[0039] Various diameters of metallic wire may be used to form the plurality of wire loops. In some embodiments, the metallic wire has a diameter greater than or equal to about 0.25 mm. For example, the diameter of the metallic wire may be greater than or equal to about 0.25 mm and less than or equal to about 1.5 mm. It is contemplated that wire having diameters within this range may be used to form a pulling roll that is sufficiently compliant to enable contact with a glass sheet without damaging the surface of the glass. In one particular embodiment, the metallic wire has a diameter of about 0.5 mm.

[0040] Referring to FIGS. 5A-5D, in one embodiment, the plurality of loops may be formed from a single metallic wire. For example, the plurality of loops 218 may be formed by wrapping a single metallic wire 301 around a forming mandrel 300 to create a spring-like coil structure. Thereafter, the forming mandrel 300 is removed from the spring-like coil structure and the individual loops are skewed in a direction perpendicular to the long axis of the coil such that each loop 220 overlaps and is non-concentric with an adjacent loop, as shown in FIG. 5B. In one embodiment, a support wire 303 may be inserted through the plurality of loops 218 to provide the loops with structural support and to maintain the relative orientation of the loops during assembly of the pulling roll.

[0041] Thereafter, the plurality of loops 218 are positioned in a holding member 230 to form the brush assembly 250, as shown in FIGS. 5C and 5D. Specifically, the holding member 230 is formed from a plastically deformable metallic material and comprises a central channel 234 in which the plurality of loops 218 are positioned, as shown in FIGS. 5C and 5D. The sidewalls of the holding member 230 are then crimped onto the plurality of loops 218 such that the plurality of loops 218 are secured in the holding member and the holding member maintains the relative positioning and orientation of the plurality of loops 218 with respect to one another.

[0042] While FIGS. 5C and 5D depict the brush assembly 250 as comprising a holding member, it should be understood that, in other embodiments, the brush assembly 250 may be formed without the holding member.

[0043] Referring now to FIG. 6, in another embodiment, the brush assembly 250 may be formed from individual metallic wires. For example, each loop 220 may be formed from a discrete circle or semi-circle of metallic wire. Thereafter, each individual loop may be positioned in a holding member, such as the holding member 230 described above, such that the loops 220 have the desired overlap and relative orientation. The holding member 230 may then be crimped to secure the loops in the holding member to form the brush assembly 250.

[0044] Referring again to FIG. 2, once the brush assembly 250 is formed using either of the aforementioned techniques, the brush assembly 250 is wrapped around the shaft member 204 such that the brush assembly 250 forms a compliant cover around the shaft member 204. In the embodiments described herein, the brush assembly 250 is spirally wound around the shaft member 204 to form the cover around the shaft member 204. The cover extends along the axial length of the shaft member 204, as depicted in FIG. 2. More specifically, the brush assembly 250 is wrapped around the shaft member 204 such that each loop 220 of the plurality of loops projects from the surface of the shaft member 204 and a plane of each loop is non- parallel with the long axis 251 of the shaft member 204, as depicted in FIG. 2. In some embodiments, the plane of each loop may be substantially perpendicular to the long axis 251 of the shaft member 204. With each loop 220 of the brush assembly 250 in this orientation (i.e., non-parallel with the long axis 251 of the shaft member), each loop 220 is centered on an axis which is non-coaxial with the long axis 251 of the shaft member 204. For example, as shown in FIG. 2, at least one loop of the brush assembly 250 is centered on axis 253 which is non- coaxial with the long axis 251 of the shaft member 204.

[0045] Referring to FIG. 4A, in some embodiments, a thermally insulating layer 231 may be positioned between the brush assembly 250 and the shaft member 204 prior to spirally winding the brush assembly 250 onto the shaft member 204. The thermally insulating layer 231 may be formed from a rigid insulating material such as, for example, rigid ceramic insulation. Suitable materials include, without limitation, KVS 174/1000 vacuum formed alumina fiber insulation manufactured by Rath-USA, or a similar material. Use of the thermally insulating layer 231 minimizes the loss of heat from the surface of the glass sheet through the pulling roll 200 and, as a result, reduces temperature gradients that may develop in the glass sheet potentially damaging the glass sheet.

[0046] Referring again to FIG. 2, a pair of retaining elements 206a, 206b may be used to assist in retaining the brush assembly 250 on the shaft member 204. Specifically, prior to winding the brush assembly 250 onto the shaft member 204, a first retaining element 206a is positioned on the shaft member 204 against shoulder 203. Thereafter, the brush assembly 250 is spirally wound around the shaft member 204 to form the cover around the shaft member 204. The second retaining element 206b is then positioned on the shaft member 204 and secured with washer 207 and nut 232 thereby axially compressing the brush assembly 250 on the shaft member 204 between the first retaining element 206a and the second retaining element 206b. The nut 232 may be tightened until a desired amount of compression of the brush assembly 250 is reached. Axially compressing the brush assembly 250 on the shaft member 204 by tightening the nut 232 increases the hardness of the pulling roll while loosening the nut 232 decreases the axial compression and softens the pulling roll. Accordingly, it should be understood that the amount of axial compression applied to the brush assembly 250 is adjustable by loosening or tightening the nut 232.

[0047] The term "axial compression," as used herein, generally refers to the amount of force applied to the brush assembly in an axial direction to compress adjacent loops of the brush assembly against one another. A greater amount of axial compression yields a harder pulling roll by making it more difficult to elastically flex individual loops. Conversely, a lower amount of axial compression yields a softer pulling roll by making it easier to elastically flex individual loops, particularly in the axial direction. For softer pulling rolls, particulate matter, such as glass debris, readily penetrates between the individual loops of the brush assembly, effectively becoming enveloped between the individual loops and drawn into the void space of the loops of the pulling roll and away from the contact surface of the pulling roll. However, such particulate matter can be readily removed from the interior volume by gently brushing the loops.

[0048] Referring now to FIG. 4B, in another embodiment, the brush assembly 250 may be spirally wrapped around a hollow metallic sleeve 237 and attached to the metallic sleeve by mechanical fasteners and/or by welding. Thereafter, shaft member 204 may be inserted into the metallic sleeve 237 with the attached brush assembly 250 and the metallic sleeve 237 may be welded or otherwise affixed to the shaft member 204.

[0049] When the brush assembly 250 is positioned on the shaft member 204 such that each loop 220 of the plurality of loops 218 projects from the surface of the shaft member 204 and a plane of each loop is non-parallel with the long axis 251 of the shaft member 204, as described above, and the cover of the pulling roll 200 (i.e., the brush assembly 250) is brought into contact with a planar surface, at least a portion of the plurality of loops are tangential to the planar surface. Referring to FIG. IB by way of example, pulling rolls 200a, 200b are depicted being used to draw a glass sheet 148 in a downstream direction 151. As the pulling rolls are rotated, each loop 220 rotates into contact with the surface plane 149 of the glass sheet 148. As each loop 220 contacts the surface plane 149 of the glass sheet 148, the surface plane 149 of the glass sheet 148 is tangential with the individual loop 220. [0050] The pulling rolls described herein may also be used to both draw the glass sheet in a draw direction and, simultaneously, apply a tensile force to the glass sheet in a direction transverse to the draw direction, flattening the glass sheet. Referring to FIG. 7, by way of example, a glass sheet 148 is drawn in the downstream direction 151 by at least one pulling roll. In the embodiment shown in FIG. 7 two pulling rolls 200a, 200c contact a first surface of the glass sheet proximate opposing lateral edges of the glass sheet. For example, the first pulling roll 200a contacts the first surface of the glass sheet 148 proximate a first lateral edge while the second pulling roll 200c contacts the glass sheet 148 proximate a second lateral edge. The brush assembly 250a of the first pulling roll 200a is spirally wound in a first direction while the brush assembly 250c of the second pulling roll 200c is spirally wound in a second direction which is opposite the first direction. Each of the first pulling roll 200a and the second pulling roll 200c may have a complimentary pulling roll which contacts a second surface of the glass sheet 148 opposite the first pulling roll 200a and the second pulling roll 200c (see, e.g., FIG. IB, wherein complimentary pulling roll 200b opposes first pulling roll 200a). In the embodiments described herein, the complimentary pulling rolls may be constructed with a spirally wound brush assembly, as described herein or, alternatively, with a conventional roll assembly (i.e., a ceramic and/or composite roll assembly). In embodiments where the complimentary pulling rolls have a spirally wound wire brush assembly, the spirally wound brush assembly may be spirally wound in a direction opposite its corresponding pulling roll. Referring to FIG. IB, by way of example, the brush assembly of the complimentary pulling roll 200b may be wound in a direction opposite the brush assembly of the first pulling roll 200a.

[0051] Referring again to FIG. 7, as the pulling rolls 200a and 200c contact the glass sheet 148 and draw the glass sheet in the downstream direction 151, the spirally wound brush assemblies of the respective pulling rolls 200a, 200c work in conjunction with one another to exert a tensile force on the glass sheet 148 transverse to the downstream direction 151. Specifically, the spirally wound brush assembly 250a of the first pulling roll 200a exerts a force on the glass sheet 148 as indicated by arrow 171 due to the winding direction of the brush assembly. Similarly, the spirally wound brush assembly 250c of the second puling roll 200c exerts a force on the glass sheet 148 in a direction indicated by arrow 172 which is equal and opposite to the force exerted by the first pulling roll 200a. While the net force acting on the glass sheet 148 in the direction transverse to the downstream direction 151 is zero, the first pulling roll 200a and the second pulling roll 200c place the glass sheet 148 in tension in the direction transverse to the downstream direction 151, flattening the glass sheet 148 and removing any bows that may develop in the glass sheet.

[0052] While FIG. 7 depicts the first pulling roll 200a and the second pulling roll 200c as being positioned on stub shaft members 204a, 204c, respectively, it should be understood that other configurations are contemplated. For example, FIG. 8 depicts one embodiment where the a first pulling roll 200a and the second pulling roll 200c are positioned on a single shaft member 204 and spaced apart in an axial direction such that the first pulling roll 200a and the second pulling roll 200c contact the first surface of the glass sheet 148 adjacent to opposed lateral edges of the glass sheet. The brush assembly 250a of the first pulling roll 200a and the brush assembly 250c of the second pulling roll 200c are wound in opposite directions, as described above, such that the first pulling roll 200a exerts a lateral force on the glass sheet 148 in the direction indicated by arrow 171 and the second pulling roll 200c exerts an equal and opposite lateral force on the glass sheet 148 as indicated by arrow 172. These forces place the glass sheet 148 in tension as the glass sheet is drawn in the downstream direction 151 thereby flattening the glass sheet.

[0053] It should now be understood that the pulling rolls described herein can be used in a glass manufacturing process to draw and/or guide glass sheets. Specifically, the overlapping loops of the brush assembly present a smooth, resilient surface with which a glass sheet can be contacted without imparting damage to the surface of the glass sheet. Moreover, because the pulling roll is constructed from metallic components suitable for use at elevated temperatures, the pulling roll does not readily degrade with prolonged use at elevated temperatures or shed particulate matter and/or debris which could contaminate the glass drawing process. Further, the individual wire loops are sufficiently resilient to envelope and absorb particulate matter into the void space of each loop reducing damage to the glass sheet.

[0054] Moreover, it should also be understood that multiple pulling rolls may be used to draw a glass sheet in a downstream direction while simultaneously placing the glass sheet under tension in a direction transverse to the downstream direction. This may be accomplished by using pulling rolls with oppositely wound brush assemblies positioned adjacent to opposing lateral edges of the glass sheet. The tensile force exerted on the glass sheet in this direction can be utilized to flatten the glass sheet as the glass sheet is drawn thereby providing additional dimensional control to the glass drawing process.

[0055] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A pulling roll for drawing glass sheet in a down-draw process, the pulling roll comprising:

a shaft member;

a brush assembly comprising a plurality of loops formed from metallic wire, wherein: each loop of the plurality of loops overlaps an adjacent loop and is parallel to and non-concentric with the adjacent loop; and

the brush assembly is spirally wound on the shaft member such that the plurality of loops project from a surface of the shaft member and a plane of each loop of the plurality of loops is non-parallel with a long axis of the shaft member, the brush assembly forming a cover of the pulling roll for contacting a planar surface such that the planar surface is tangential to at least a portion of the plurality of loops of the brush assembly when the cover contacts the planar surface.

2. The pulling roll of claim 1 , wherein the metallic wire is a single metallic wire.

3. The pulling roll of claim 1, wherein each loop of the plurality of loops is formed from individual metallic wires.

4. The pulling roll of claim 1, wherein the brush assembly further comprises a holding member having a channel, wherein the plurality of loops are secured in the channel of the holding member.

5. A pulling roll for drawing glass sheet in a down-draw process, the pulling roll comprising:

a shaft member;

a brush assembly comprising:

a single metallic wire formed into a plurality of loops, wherein each loop of the plurality of loops overlaps an adjacent loop and is parallel to and non-concentric with the adjacent loop;

a holding member having a channel, wherein the plurality of loops are secured in the channel of the holding member; and

6. The pulling roll of claim 1 or claim 5, wherein the plane of each loop of the plurality of loops is perpendicular to the long axis of the shaft member when the brush assembly is spirally wound around the shaft member.

7. The pulling roll of claim 1 or claim 5, further comprising a thermally insulating layer positioned between the shaft member and the brush assembly.

8. The pulling roll of claim 1 or claim 5, further comprising a metallic sleeve positioned between the shaft member and the brush assembly.

9. The pulling roll of claim 1 or claim 5, wherein the brush assembly is axially compressed on the shaft member.

10. The pulling roll of claim 9, wherein the brush assembly is axially compressed between a pair of retaining elements.

11. The pulling roll of claim 9, wherein an axial compression of the brush assembly on the shaft member is adjustable.

12. The pulling roll of claim 1 or claim 5, wherein the metallic wire has a diameter greater than or equal to 0.25 mm and less than or equal to 1.5 mm.

13. The pulling roll of claim 1 or claim 5, wherein the metallic wire comprises an oxidation-resistant coating.

14. The pulling roll of claim 1 or claim 5, wherein the brush assembly further comprises a support wire extending through the plurality of loops.

15. The pulling roll of claim 1 or claim 5, wherein each loop of the plurality of loops has the same loop diameter.

16. The pulling roll of claim 1 or claim 5, wherein each loop of the plurality of loops has a loop diameter greater than or equal to about 2.5 cm and less than or equal to about 5.08 cm.

17. The pulling roll of claim 1 or claim 5, wherein a center-to-center spacing between adjacent loops is greater than or equal to about 0.25 cm and less than or equal to about 1.3 cm.

18. A method for forming a glass sheet, the method comprising:

melting glass batch materials to form molten glass;

forming the molten glass into the glass sheet;

contacting at least a first surface of the glass sheet with at least one pulling roll to convey the glass sheet in a downstream direction, wherein the at least one pulling roll comprises:

a shaft member; and a brush assembly comprising a plurality of loops formed from metallic wire, wherein: each loop of the plurality of loops overlaps an adjacent loop and is parallel to and non-concentric with the adjacent loop; and the brush assembly is spirally wound on the shaft member such that the plurality of loops project from a surface of the shaft member and a plane of each loop of the plurality of loops is non-parallel with a long axis of the shaft member, wherein at least a portion of the plurality of loops of the at least one pulling roll are tangential to the first surface of the glass sheet when the at least one pulling roll contacts the first surface of the glass sheet.

19. The method of claim 18, wherein the at least one pulling roll comprises a first pulling roll and a second pulling roll, wherein the first pulling roll and the second pulling roll exert a tensile force on the glass sheet transverse to the downstream direction as the glass sheet is drawn in the downstream direction.

20. The method of claim 18, wherein:

the at least one pulling roll comprises a first pulling roll and a second pulling roll, wherein the brush assembly of the first pulling roll is spirally wound in a first direction and the brush assembly of the second pulling roll is spirally wound in a second direction opposite the first direction;

the first pulling roll contacts the first surface of the glass sheet adjacent to a first lateral edge of the glass sheet; and

the second pulling roll contacts the first surface of the glass sheet adjacent to a second lateral edge of the glass sheet such that the first pulling roll and the second pulling roll exert a tensile force on the glass sheet transverse to the downstream direction as the glass sheet is drawn in the downstream direction.

21. The method of claim 18, wherein the brush assembly is a first brush assembly and the pulling roll further comprises a second brush assembly spirally wound on the shaft member and spaced apart from the first brush assembly in an axial direction.

22. The method of claim 21, wherein the first brush assembly is spirally wound on the shaft member in a first direction and the second brush assembly is spirally wound on the shaft member in a second direction opposite the first direction such that the first brush assembly and the second brush assembly exert a tensile force on the glass sheet transverse to the downstream direction as the glass sheet is drawn in the downstream direction.

23. The method of claim 18, wherein the metallic wire is a single metallic wire.

24. The method of claim 18, wherein each loop of the plurality of loops is formed from individual metallic wires.

25. The method of claim 18, wherein the brush assembly further comprises a holding member having a channel, wherein the plurality of loops are secured in the channel of the holding member.

26. The method of claim 18, wherein the plane of each loop of the plurality of loops is perpendicular to the long axis of the shaft member when the brush assembly is spirally wound around the shaft member.

27. The method of claim 18, further comprising a thermally insulating layer positioned between the shaft member and the brush assembly.

28. The method of claim 18, wherein the brush assembly is axially compressed on the shaft member.