WO2015026777A1

WO2015026777A1 - Apparatus and method for applying cross-ribbon tension in a glass making process

Info

Publication number: WO2015026777A1
Application number: PCT/US2014/051620
Authority: WO
Inventors: James Michael Brown; Keith Mitchell Hill; Garrett David SPIER; George Davis Treichler; Xi Xie
Original assignee: Corning Incorporated
Priority date: 2013-08-23
Filing date: 2014-08-19
Publication date: 2015-02-26
Also published as: KR20160044577A; JP2016532627A; CN105683100A; TW201522245A

Abstract

A caster assembly configured to engage a continuously moving ribbon of material, such as a glass ribbon, and apply a tension force to the glass ribbon. The caster assembly may be used in a set of caster assemblies, wherein each set includes two opposing pairs of opposing caster assemblies configured to pinch opposing edge portions of the glass ribbon between the opposing caster assemblies with a predetermined pinch force. Each caster assembly includes at least one force device, wherein engagement between a caster wheel and the ribbon of material rotates a caster wheel mounting member against a force produced by force device, thereby applying the tension force. Each caster assembly may further include a second force device configured to vary the pinch force.

Description

APPARATUS AND METHOD FOR APPLYING CROSS-RIBBON TENSION IN A

GLASS MAKING PROCESS

PRIORITY

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S.

Provisional Application Serial No. 61/869133 filed on August 23, 2013, the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND

Field

[0002] The present disclosure relates generally to apparatus and methods of processing a ribbon of material, and more specifically to apparatus and method of producing tension across a width of a glass ribbon.

Technical Background

[0003] In a typically fusion downdraw method for manufacturing glass sheets, molten glass is supplied to a forming body over which the molten glass flows as separate streams of glass.

The separate streams of glass re-unite at the bottom of the forming body to form a glass ribbon having surfaces of exceptional quality. Thermal gradients and other factors may induce a curvature in the ribbon in a width direction across the glass ribbon. In some instances this curvature is helpful, as it can add stiffness to the glass ribbon. However, the glass ribbon is easier to process, for example during cutting and separation processes, when such curvature is reduced.

[0004] For high speed processing and smooth ribbon motion, it is desirable to have a mechanism that can continuously tension the ribbon with as little adverse impact as possible, while minimizing motion disturbance from other sources and stabilizing the process.

SUMMARY

[0005] Described herein are apparatus for applying a tension in a continuously moving glass ribbon. For example, the apparatus described herein may be used in a downdraw glass making process intended for the production of glass sheet. For example, the apparatus described herein may be used in a fusion downdraw process, or in other processes wherein a glass ribbon is conveyed from one location to another location, such as reel-to-reel processing of a thin flexible glass ribbon. The apparatus include opposing caster assemblies configured to engage surfaces of the glass ribbon, thereby pinching the glass ribbon between the opposing caster assemblies. The caster assemblies are rotatable in a direction parallel with a general plane of the glass ribbon and apply a tensioning force to the glass ribbon in a direction perpendicular to the direction in which the glass ribbon is being drawn, the draw direction. That is the caster assemblies produce a tension across a width of the glass ribbon that tends to flatten the glass ribbon, thereby reducing curvature in the glass ribbon. For example, the caster assemblies may be spring-loaded such that when engaged with a surface of the glass ribbon, the force derived from a spring is applied to the glass ribbon. Opposing pairs of the caster assemblies maybe employed and positioned along opposing edge portions of the glass ribbon, thereby producing a tension in the ribbon across the width of the glass ribbon between the opposing pairs of caster assemblies. The caster assemblies may have multiple degrees of freedom (axes of rotation), allowing for control of tension and pinch force. In some embodiments a pre-set tension or pinch force can be varied by a controller. Accordingly, the pre-set tension or pinch force can be set according to draw conditions, such as ribbon thickness and ribbon curvature.

[0006] In one aspect an apparatus for manufacturing a sheet of glass is disclosed comprising: a forming body from which molten glass is drawn to produce a continuously moving ribbon of glass; a scoring apparatus positioned below the forming body relative to a draw direction; a caster assembly positioned between the scoring apparatus and the moving ribbon of glass and configured to engage with the moving ribbon of glass, the caster assembly comprising: a caster wheel mounting member a caster wheel rotatably coupled to the caster wheel mounting member and rotatable about a first axis of rotation; a frame member rotatably coupled to the caster wheel mounting member, the caster wheel mounting member being rotatable about a second axis of rotation; a first force mechanism configured to apply a first force to the caster wheel mounting member that urges the caster wheel mounting member in a rotation about the second axis of rotation; and wherein a plane perpendicular to and passing through the first axis of rotation intersects the second axis of rotation.

[0007] The caster assembly may further comprise a drive mechanism coupled to the first force device and configured to vary the first force applied to the caster wheel mounting member. In some embodiments the caster wheel mounting member comprises a gimbal block and a body portion rotatably coupled to the gimbal block, and wherein the body portion is rotatable about a third axis of rotation. The third axis of rotation may intersect the moving glass ribbon at a location on the moving glass ribbon where the caster wheel is configured to engage with the moving glass ribbon. For example, the third axis of rotation may intersect a surface of the moving glass ribbon at a non-zero angle.

[0008] In some embodiments the caster wheel mounting member may be configured to rotate about a fourth axis of rotation perpendicular to the second axis of rotation.

[0009] The apparatus may further comprise a second force mechanism configured to apply a second force to the caster wheel mounting member and urge the caster wheel mounting member in a rotation about the fourth axis of rotation. A second drive device can be coupled to the second force mechanism and configured to vary the second force.

[0010] In some embodiments the caster assembly is movable between an engaged position and a disengaged position relative to the moving glass ribbon, wherein in the engaged position the caster wheel is in contact with the moving glass ribbon, and in the disengaged position the caster wheel is not in contact with the moving glass ribbon.

[0011] In some embodiments the frame member may be rotatably coupled to a base member configured to rotate the frame member such that the caster wheel is engaged and disengaged with the glass ribbon. In other embodiments the frame member may be coupled to a linear slide configured to translate the frame member such that the caster wheel is engaged and disengaged with the glass ribbon.

[0012] In another aspect a method of drawing a ribbon of glass is described comprising: flowing molten glass from a forming body to form the ribbon of glass, the ribbon of glass moving in a draw direction; engaging the ribbon of glass with a caster assembly, the caster assembly comprising: a caster wheel mounting member; a caster wheel rotatably coupled to the caster wheel mounting member and rotatable about a first axis of rotation; a frame member rotatably coupled to the caster wheel mounting member, the caster wheel mounting member being rotatable about a second axis of rotation; a first force mechanism configured to apply a first force to the caster wheel mounting member that urges the caster wheel mounting member in a rotation about the second axis of rotation; and wherein the engaging causes the caster wheel mounting member to rotate about the second axis of rotation in opposition to the first force, the first force thereby forming a tension force in the glass ribbon in a direction away from a centerline of the glass ribbon.

[0013] In some embodiments a plane passing through and perpendicular to the first axis of rotation forms an angle a relative to the draw direction after the engaging. The angle a may be, for example, in a range from about 0 degrees to about 10 degrees, from about 0 degrees to about 5 degrees, or in a range from about 0 degrees to about 3 degrees. [0014] The first force mechanism can be coupled to a first drive device, wherein the method may further comprise varying the first force with the first drive device.

[0015] In some embodiments the caster wheel mounting member comprises a gimbal block and a body portion, and wherein the body portion is coupled to the gimbal portion and rotatable about a third axis of rotation relative to the gimbal block.

[0016] The caster assembly may further comprise a second force mechanism configured to apply a second force to rotate the caster wheel mounting member about a fourth axis of rotation perpendicular to the second axis of rotation.

[0017] The caster assembly may further comprise a second drive device coupled to the second force mechanism, the method further comprising using the second drive device to vary the second force.

[0018] The method may further comprise varying the second force to vary a normal force applied against the glass ribbon by the caster wheel.

[0019] The method may further comprise varying the first force to vary a lateral tension in the glass ribbon.

[0020] In some embodiments the method may further comprise varying the second force in response to a change in lateral tension in the glass ribbon.

[0021] Additional features and advantages of various embodiments 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 embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings. The accompanying drawings are included to provide a further understanding of the embodiments, and are incorporated into and constitute a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a cross sectional elevational schematic an embodiment of a glass making system;

[0023] FIG. 2 is a side view of a forming body of a type employed in the glass making system of FIG. 1 ;

[0024] FIG. 3 is a front view of a forming body of a type employed in the glass making system of FIG. 1 ;

[0025] FIG. 4 is a cross-sectional side view of a forming body and cutting apparatus of a type employed in the glass making system of FIG. 1; [0026] FIGS. 5A and 5B are top and side views, respectively, of a simple rotary caster assembly;

[0027] FIG. 6 is an embodiment of a caster assembly according to the present disclosure;

[0028] FIG. 7 is another embodiment of a caster assembly according to the present disclosure;

[0029] FIG. 8 is a side view of a pair of caster assemblies of the type depicted in FIG. 6 and shown engaged with a glass ribbon, wherein the glass ribbon is pinched between the caster assemblies;

[0030] FIGS. 9A - 9C are three isometric views of an embodiment of a caster assembly according to an embodiment disclosed herein;

[0031] FIG. 10 is a front view of another embodiment of a caster assembly according to an embodiment described herein;

[0032] FIG. 11 is an front view of a portion of a glass drawing apparatus including a first set of caster assemblies positioned above a scoring apparatus, and an optional second set of caster assemblies positioned below the scoring apparatus, the first and optional second caster assemblies arranged to engage a glass ribbon drawn from the glass drawing apparatus;

[0033] FIG. 12 is a side view of a pair of caster assemblies of the type depicted in FIGS. 8A - 8C and shown engaged with a glass ribbon, wherein the glass ribbon is pinched between the caster assemblies;

[0034] FIG. 13 is a front view of a caster assembly of FIGS. 9A- 9C showing the caster assembly canted at an angle relative to the draw direction;

[0035] FIG. 14 is a front view of another embodiment of a glass drawing apparatus including a first set of caster assemblies positioned above a scoring apparatus, and an optional second set of caster assemblies positioned below the scoring apparatus, the first and optional second caster assemblies arranged to engage a glass ribbon drawn from the glass drawing apparatus;

[0036] FIG. 15 is a graph showing the modeled effect on the lateral (width-wise) shape of a set of caster assemblies engaged with a continuously moving glass ribbon; and

[0037] FIG. 16 is a perspective view of a reel-to-reel process utilizing caster assemblies as described herein. DETAILED DESCRIPTION

[0038] Reference will now be made in detail to the embodiments described herein, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

[0039] In a typical downdraw process, molten glass is drawn from a forming body into a ribbon of glass. Such downdraw processes include slot draw, wherein molten glass is drawn from a reservoir of molten glass through a slot, or the fusion downdraw process wherein molten glass supplied to a trough disposed in an upper surface of a forming body overflows the trough and flows down converging forming surfaces of the forming body. The separate flows rejoin at the bottom of the forming body to form the ribbon of glass. Other processes, such as a redraw process, can rely on the softening of a preformed body of glass and subsequently drawn to thinner dimensions. As used herein, a downdraw process shall be interpreted to mean any method for manufacturing sheets of glass that utilizes drawing the glass in a downward direction from a softened state, and includes without limitation a fusion process, a slot draw process or a redraw process. To that end, by way of example, the fusion process will be described in more detail below, with the understanding that the teaching of the present disclosure can be used in the practice of other glass making processes including, without limitation, slot draw and redraw.

[0040] In an exemplary fusion glass manufacturing apparatus 10 illustrated in FIG. 1 , batch material, represented by arrow 12, is fed into a melting furnace 14 and melted to form molten glass 16 at a first temperature Ti. First temperature Ti is dependent on the particular glass composition, but for liquid crystal display-capable glasses, as a non-limiting example, Ti can be in excess of 1500°C. The molten glass flows from melting furnace 14 through connecting conduit 18 to finer conduit (finer) 20. From finer 20 the molten glass flows to stirring vessel 22 through connecting conduit 24 to be mixed and homogenized, and from stirring vessel 22 through connecting conduit 26 to delivery vessel 28 and thereafter to downcomer 30. The molten glass can then be directed from downcomer 30 to forming body 32 through inlet 34. As best seen in FIG. 2 showing forming body 32 in cross section, forming body 32 comprises a trough 36 that receives the flow of molten glass from inlet 34 and exterior converging forming surfaces 38 that meet along a line, root 40, at the bottom edge of the forming body. In the case of the fusion downdraw process depicted in FIG. 1 , the molten glass delivered to trough 36 flows over converging forming surfaces 38 of forming body 32 as separate streams that join together, or fuse, at root 40 to form ribbon of glass 42. The ribbon of glass is drawn downward from root 40 by pulling rolls 44. The ribbon may then be cooled and separated to form individual glass sheets 46 as will be described in more detail below.

[0041] FIG. 3 shows front view of the forming body 32 of FIG. 1, and includes also a depiction of pulling rolls 44 and a glass scoring apparatus 48. Pulling rolls 44 are arranged in opposing pairs and are counter-rotating. That is, an individual pulling roll positioned adjacent to a first side of the glass ribbon is rotating in a direction opposite a pulling roll positioned across from the first pulling roll and adjacent the second side of the glass ribbon. The glass ribbon is positioned between the opposing pairs of pulling rolls so that the pulling rolls contact and pinch the glass ribbon at the edge portions of the glass ribbon. The counter- rotating pulling rolls are driven by motors and apply a downward force on the glass ribbon, thereby drawing the glass ribbon from the forming body in a draw direction 50. The pulling rolls also help support a weight of the glass ribbon, as during at least a portion of the separation cycle that portion of the glass ribbon below the pulling rolls may be unsupported. Without a suitable pinching force, the pulling rolls may be unable to apply a sufficient downward pulling force, or be unable to support that portion of the glass ribbon below the pulling rolls against the force of gravity.

[0042] As the glass ribbon descends from the forming body, glass scoring apparatus 48 periodically engages the ribbon and forms a score 52 across at least a portion of the glass ribbon. To ensure maximum utilization of the sheets of glass separated from the glass ribbon, it is desirable to produce a score that is substantially perpendicular to lateral edges 54 of the glass ribbon. As the glass ribbon is moving continuously in the draw direction 50, and the scoring device travels across the width of the glass ribbon at a finite speed to form the score, it should be apparent that to produce a score that is perpendicular to the lateral edges of the glass ribbon the scoring device should move such that there is no relative motion between the scoring device and the glass ribbon in a direction parallel with the draw direction during the scoring process. Accordingly, in one embodiment glass scoring apparatus 48 first moves from an initial position in the draw direction at a velocity that matches that of the moving glass ribbon. That is, the glass ribbon is continuously moving with a velocity vector V having a direction in the draw direction 50 and a predetermined speed S. The glass scoring apparatus starts to move in the draw direction and acquires a velocity vector matching the velocity vector of the glass ribbon. At a predetermined time during the travel of the glass scoring apparatus in the draw direction, a nosing member 56 (see FIG. 4) coupled to the glass scoring apparatus engages a first side of the glass ribbon that is opposite a second side of the glass ribbon that is contacted by a scoring device 58. For clarity, the side of the glass ribbon contacted by the scoring device 58 (e.g. by a score wheel) will be designated as the "A" side of the glass ribbon, whereas the opposing side of the glass ribbon that is contacted by the nosing member will be designated the "B" side (for simplicity, the same designation will be carried through to the glass sheet separated from the glass ribbon such that the side of the glass sheet that was formally contacted by the scoring device or the nosing member will be designated the "A" side and the "B" side of the glass sheet, respectively). The nosing member 56 can be used to flatten the glass sheet and to provide a force counter to the force applied by the scoring wheel. That is, the nosing member functions as an anvil against which the scoring wheel presses the glass ribbon during the scoring process. Although not shown, in some embodiments additional nosing members may be used, either on the "A" side of the glass ribbon, on the "B" side of the glass ribbon, or both the "A" side and the "B" side to aid in flattening the ribbon or reducing vibration that would otherwise travel upward along a length of the ribbon into a portion of the ribbon that is visco-elastic. Vibration in the visco- elastic portion of the ribbon, where the glass ribbon is transitioning from a viscous state to an elastic state, can induce unwanted stress in the glass ribbon that may result in warping of the glass sheet removed from the glass ribbon.

[0043] In some scoring processes, a robot 60 engages with the end of the glass ribbon prior to the scoring process. The robot includes a robot arm 62 terminating in a frame 64 comprising clamping devices 66 (e.g. suction cups) that engage with edge portions of the "B" side of the glass ribbon. The robot arm moves the engaged clamping devices in the draw direction at the velocity vector of the glass ribbon such that the glass ribbon, the glass scoring apparatus

(including the scoring device and the nosing) and the engaged clamping devices are all moving in tandem so that there is no relative motion between them. It should be noted that the velocity vector include the draw direction and a draw speed. In other words, the robot arm causes the clamping devices to track with the ribbon. When the robot arm is tracking with the glass ribbon so that no relative motion between the engaged clamping devices and the glass ribbon in the draw direction is occurring, the clamping devices are engaged with the glass ribbon below the score (or in a location that will be below the score once formed).

Once the score has been completed, the robot arm imparts a bending moment to the glass ribbon against nosing member 56, creating tension across the score so that the vent crack formed in the glass ribbon as a result of the scoring propagates through the thickness of the glass ribbon and separates a glass sheet from the glass ribbon. The robot arm, through the clamping devices, remains engaged with the glass sheet that has just been separated from the glass ribbon and moves the glass ribbon to a receiving station. The robot arm can, for example, deposit the glass sheet onto a conveyor assembly that moves the glass ribbon for downstream processing (such as removal of the edge portions of the glass sheet, edge finishing, washing, etc.).

[0044] It is desirable that the glass ribbon in the region where the score is produced is flat. That is, that any curvature in the width direction be removed, at least within the vicinity of the scoring. To produce a consistent scoring depth and therefore a consistent separation process, this curvature should be removed as the scoring device forms the score line. To wit, the glass ribbon should exhibit adequate stiffness, i.e. a resistance to bending. In addition to the use of nosing 56, another method of producing such stiffness comprises applying a tensioning force to the glass ribbon.

[0045] A key component to embodiments disclosed herein is a tensioning device comprising a caster assembly, wherein a wheel of the caster assembly is pressed or pinched onto a surface of the continuously moving glass ribbon. The relative motion between the ribbon and the caster wheel operates the tensioning device. The caster wheel can be configured, if desired, to provide a mechanical feedback loop that adjusts the trailing angle of the caster wheel to ensure proper tensioning of the glass ribbon.

[0046] The following brief description in respect of FIGS. 5A and 5B shows an example of a basic caster assembly 68. As shown in FIGS. 5A and 5B, exemplary caster assembly 68 comprises a caster wheel mounting member 70 comprising body portion 72 and one or more legs 74 extending therefrom and between which is mounted a caster wheel 76. Caster wheel 76 is mounted to legs 74 by axle 78. Caster wheel 76 is configured to rotate about a first axis of rotation 80 that lies within axle 78. For example, in some embodiments, axle 78 is a unitary structure that extends through caster wheel 76 and is mounted to the one or more legs 74. Caster wheel 76 may be rigidly coupled to axle 78, wherein axle 78 is rotatably coupled to the one or more legs 74 by bearings, or caster wheel 76 may be rotatably coupled to axle 78 by bearings, and wherein axle 78 is rigidly coupled to legs 74. More simply put, caster wheel 76 is configured to rotate about axis of rotation 80.

[0047] Caster wheel mounting member 70 may be rigidly mounted to a frame member 82, wherein caster assembly 68 is referred to as a rigid caster assembly. In an alternative embodiment, caster wheel mounting member 70 may be mounted to frame member 82 so that the caster assembly may be configured to swivel.

[0048] In the instance of a swivel caster assembly, shown in FIGS. 5 A and 5B, the caster assembly further comprises a second axle 84 having an axis of rotation 86 that lies within the second axle. Second axis of rotation 86 is perpendicular to first axis of rotation 80 and is separated therefrom by an offset distance δ.

[0049] Swivel casters may be configured to rotate about second axis of rotation 86 in response to an imbalance of forces acting on the caster. That is, assume second axle 84 is fixed, but caster wheel mounting member 70 is free to rotate about second axis of rotation 86 and caster wheel 76 is in contact with surface 88 moving in direction 90. Caster wheel 76 will "trail" second axis of rotation 86 relative to the direction of movement of surface 88, and, further assuming symmetric arrangement of caster wheel 76 and caster wheel mounting member 70, caster wheel 76 will lie along line 92 parallel with the direction of movement of surface 88, wherein line 92 represents a plane of caster wheel 76. As used herein, the term trail means the caster wheel is positioned downstream of (behind) second axis of rotation 86 in the direction of movement of surface 88. If the direction of movement of surface 88 changes, an imbalance of frictional forces between caster wheel 76 and surface 88 will result in a realignment of the caster wheel to again trail second axis of rotation 86 and wherein a plane of the caster wheel will be parallel with the direction of movement of the surface. In other terms, neglecting bearing forces (e.g. friction within the bearings), the caster assembly described above rotates about second axis of rotation 86 to again align parallel with the relative motion between itself and the surface the caster wheel is in contact with.

[0050] In accordance with embodiments described herein, a caster assembly is employed wherein the caster assembly is neither a rigid caster assembly, nor is the caster assembly a freely rotating swivel caster. Rather, the caster assembly includes a force mechanism that applies a force to the caster assembly to align the caster assembly, in the absence of other forces, in a direction that is not parallel with the direction of relative motion between the caster assembly and the surface the caster assembly is in contact with. That is, the caster assembly is configured such that while the caster wheel can rotate about an axis of rotation that is perpendicular to the axis of rotation about which the wheel itself rotates, and thus the plane of the wheel can align with the draw direction, a force is applied to the wheel, or a mounting member thereof, that urges the caster wheel into a non-aligning position. Put another way, an imbalance in force is intentionally introduced so that a force perpendicular to the direction of relative motion is needed to maintain this equilibrium position. The principal of operation of such caster assemblies is described in more detail below in reference to FIGS. 6 and 7. [0051] Shown in FIG. 6 is a caster assembly 100 incorporating a force mechanism. Caster assembly 100 comprises a caster wheel mounting member 102 to which caster wheel 104 is rotatably coupled by first axle 106 at a distal end 108 of caster wheel mounting member 102. Caster wheel 104 is rotatable about first axis of rotation 110 that lies within first axle 106. A proximal end 112 of caster wheel mounting member 102 is in turn rotatably mounted to frame member 114 by second axle 116, wherein caster wheel mounting member 102 is rotatable about second axis of rotation 118 that lies within second axle 116. A force mechanism 120 is engaged with caster wheel mounting member 102 and applies a force against caster wheel mounting member 102 so that caster wheel mounting member 102 is urged in a predetermined direction of rotation 122 about second axis of rotation 118. A stop (not shown) may be provided that limits rotational movement of the caster wheel mounting arm about second axis of rotation 118. In the example of FIG. 6, force mechanism 120 comprises a simple torsion spring engaged with both caster wheel mounting member 102 and frame member 114. In this example, the torsion spring is positioned about second axle 116. Other mechanisms for applying a rotational force against caster wheel mounting member 102 that urges caster wheel mounting arm 102 to rotate about second axis of rotation 118 may also be employed. For example, a pneumatic cylinder 119 maybe employed, as shown in FIG. 7.

[0052] Frame member 1 14 may be rotatably mounted to base member 124 to facilitate movement of the caster assembly away from the path of a moving glass ribbon 42 moving in a draw direction 50 prior to engagement of the caster wheel with material. For example, in the embodiment of FIG. 6, caster assembly 100 may be rotated such that caster wheel 104 does not contact the ribbon of moving material. For example, frame member 114 may be mounted to base member 124 so that if second axis of rotation 118 is positioned to be perpendicular to a surface of the moving material 128 (e.g. continuously moving glass ribbon 42) and a plane 130 of caster wheel 104 is aligned with (parallel to) a draw direction 50 of the moving material, caster wheel 104 will contact moving material 128 at an edge portion 132 of the moving material. As shown in the embodiment of FIG. 6, the plane 130 of caster wheel 104 intersects both first axis of rotation 110 and second axis of rotation 118. Preferably, plane 130 is perpendicular to first axis 110 and second axis of rotation 118 is parallel to and lies within plane 130.

[0053] Alternatively, frame member 114 may be rigidly mounted to base member 124, wherein base member 124 is mounted to a slide device that translates caster assembly 100 so that caster wheel 104 does not contact the moving glass ribbon 42. In some embodiments, frame member 114 may be capable of being both rotated and translated, wherein frame member 1 14 is rotatably mounted to base member 124 and base member 124 may be translated.

[0054] The following is a description of the operation of a pair of caster assemblies 100 relative to glass ribbon 42, as shown in FIG. 8. In FIG. 8, the view of the caster assemblies 100 is from above and the continuously moving glass ribbon 42 is assumed to be moving into the drawing page. For purposes of discussion and not limitation, it will be assumed that a) both caster assemblies are identical, but arranged on opposite sides of the continuously moving glass ribbon, b) that frame members 114 are rotatably mounted to base members 124 that comprise one or more linear slides for translating caster assemblies 100 in a direction toward or away from the continuously moving glass ribbon (between an engaging position and a non-engaging position), and c) that force mechanisms 120 comprise torsion springs engaged with the caster wheel mounting members 102 and frame members 114 of the respective caster assemblies. It will be further assumed that the caster assemblies are initially in non-engaging positions and glass ribbon 42 is continuously moving at a position adjacent to the caster assemblies. In the non-engaging position, force mechanisms 120 are applying a force against caster wheel mounting members 102 that urge the caster wheel mounting members 102 into a position so that the planes 130 of the respective caster wheels are not parallel (not aligned with) the direction of travel 50 of the continuously moving glass ribbon as shown in FIG. 6. It should be noted that although this and following embodiments are described in terms of a continuously moving glass ribbon, caster assemblies described herein can be used in the processing of other materials.

[0055] Base members 124 may be moved in a direction toward continuously moving glass ribbon 42 until caster wheels 104 contact respective surfaces of continuously moving glass ribbon 42 and the glass ribbon 42 is pinched between the opposing caster wheels with a predetermined pinch force. For example, the pinch force per side of the glass ribbon should be suitable to achieve a tension force across the width of the glass ribbon in a range from about 2 kg to about 10 kg, and in some embodiments a tension force in a range from about 2 kg to about 5 kg. For example, the pinch force may be in a range from about 0.5 kg force to about 3 kg and in some embodiments in a range from about 2 kg to about 5 kg. In accordance with the preceding principals of operation, caster wheel mounting members 102 may be rotated about their respective second axis of rotation 118 in directions that tend to align the planes 130 of the respective caster wheels into trailing alignment with the direction of travel 50 of the continuously moving glass ribbon 42. However, rotation of the caster wheel mounting members 102 about second axis of rotation 118 in response to their contact with the continuously moving glass ribbon occurs against the force applied by the torsion springs 120. Accordingly, the force applied by each torsion spring increases as the caster wheel mounting members 102 rotate according to their individual spring constants. Rotation of caster wheel mounting members 102 continues until the force applied by torsion springs 120 is in equilibrium with the frictional forces between caster 104 wheels and the continuously moving glass ribbon 42. Each caster assembly 100 may be moved into an engaging position with continuously moving glass ribbon 42 by translating the caster assemblies away from the glass ribbon (in a direction perpendicular to the glass ribbon) via linear slide mechanism 134 as indicated by double headed arrows 136, or rotated into an engaging or non-engaging position by rotating frame members 114 on axles 138 comprising linear slide mechanism 134 and containing a third axis of rotation 140 as indicated by double headed arrows 142, or both translated and rotated.

[0056] The foregoing description assumes the continuously moving glass ribbon is constrained laterally (in a widthwise direction), or otherwise incapable of lateral movement. However, in a typical downdraw glass sheet manufacturing operation as previously described, the continuously moving glass ribbon can in fact be moved in a lateral direction, so that during the process of reaching an equilibrium position, the pair of caster assemblies will tend to pull the ribbon in a width direction via the force mechanism 120, thereby changing a position of the glass ribbon. Such movement in a single direction is generally undesirable. Accordingly, a second pair of caster assemblies may be positioned adjacent the second edge of the glass ribbon to pull the glass ribbon in a lateral direction with a force equal to but opposite the first pair of caster assemblies so that the second pair of caster assemblies are laterally aligned with the first pair of caster assemblies and the tension produced is predominately perpendicular to the draw direction 50.

[0057] It should be noted that in a typical downdraw glass sheet forming process, such as the fusion process previously described, the glass ribbon may have a curvature in the width dimension of the glass ribbon that can be undesirable. Moreover, the glass ribbon is often very thin and provides little resistance to "deformation". Accordingly, in the preceding scenario, where two pair of caster assemblies are engaged with the glass ribbon adjacent opposite edges of the glass ribbon so that a tension is applied across a width of the glass ribbon in a direction perpendicular to the draw direction, and wherein the opposing widthwise forces applied by the caster assemblies from each edge portion 54 of the glass ribbon are substantially equal, the glass ribbon can be "stretched" into a planar shape without deviating the glass ribbon from the draw direction. In other words, the glass sheet can be ironed out to be substantially flat between the two opposite pairs of opposing caster assemblies. Ideally, the imbalance of frictional forces between the caster wheels and the continuously moving ribbon of glass drive the respective caster assemblies until the planes of their individual caster wheels are aligned with the draw direction, however from a practical perspective, there will always be an equilibrium offset angle a (see FIG. 6). In some examples, offset angle a in a direction away from a centerline of the glass ribbon can be in a range from about 0 degrees to about 3 degrees. However, the more tension that applied across the width of the glass ribbon, the larger the angle. Thus, the angle is a function of the desired tension, and an angle a greater than 3 degrees may be used depending on the desired tension, for example in a range from about 0 degrees to about 5 degrees, and in some embodiment in a range from about 0 degrees to about 10 degrees.

[0058] While the preceding example is capable of producing a region of flattening of the glass ribbon along a line or narrow strip of the glass ribbon across a width of the ribbon, it should be clear that adding a second set of oppositely placed, opposing caster assemblies positioned along a line in the width dimension of the glass ribbon that is displaced in the draw direction from a similar lateral line formed by the first set of caster assemblies by a predetermined amount can produce a much larger flattened region along the draw direction (e.g. a length direction of the glass ribbon).

[0059] FIGS. 9A - 9C illustrate three orthogonal views of another embodiment of a caster assembly 200 according to the present disclosure. As shown in a first front view of FIG. 9A, caster assembly 200 comprises caster wheel mounting member 202 comprising gimbal block 204, body portion 206 and at least one leg portion 208 extending from the body portion. In the embodiment of FIGS. 9A - 9C, caster wheel mounting member 202 comprises two leg portions 208. FIG. 10 illustrates another embodiment of caster assembly 200 wherein caster wheel mounting member 202 comprises only a single leg portion 208. Caster wheel 210 is rotatably coupled to caster wheel mounting member 202 (e.g. leg portion 208) via first axle 212, and is configured to rotate about first axis of rotation 214 that lies within and extends through the length of first axle 212, as indicated by arrow 216 (FIG. 9B).

[0060] Caster assembly 200 further comprises frame member 218. Caster wheel mounting member 202 is rotatably coupled to frame member 218 by second axle 220 (see FIG. 9B) that is connected to gimbal block 204. That is, second axle 220 extends through and is rotatable within frame member 218, and is coupled to gimbal block 204. Accordingly, caster wheel mounting member 202 is configured to rotate about second axis of rotation 222 that lies within and extends through second axle 220.

[0061] Body portion 206 of caster wheel mounting member 202 is rotatably coupled to gimbal block 204 via third axle 224. Accordingly, body portion 206 is configured to rotate about third axis of rotation 226 that lies within and extends through the length of third axle 224, as indicated by the double headed arrow 228 (FIG. 9C). It should be noted that dashed line 228 in FIG. 9A represents the edge of a plane that bisects caster wheel 210. Plane 228 is perpendicular to first axis of rotation 214, and second axis of rotation 226 is parallel to and lies within plane 228. Plane 228 will hereafter be referred to as the plane of caster wheel 210.

[0062] Frame member 218 is coupled to one end of fourth axle 230 and configured to rotate about fourth axis of rotation 232 that lies within and extends through the length of fourth axle 230. Accordingly caster wheel mounting member 202, which is rotatably coupled to frame member 218 by gimbal block 204 and second axle 220, is also configured to rotate about fourth axis of rotation 232. Fourth axis of rotation 232 intersects with and is perpendicular to second axis of rotation 222.

[0063] As best seen in FIG. 9B, second axle 220 is coupled to first force mechanism 234, such as first torsion spring 234. In accordance with FIG. 9B, first torsion spring retaining plate 236 is rigidly coupled to frame member 218. Second axle 220 extends through first torsion spring retaining plate 236 and is rotatable therein. One end of first torsion spring 234 is coupled to, or at least prevented from rotating against first torsion spring retaining plate 236 by a stop (not shown). The other end of first torsion spring 234 is coupled to, or at least prevented from rotating against second torsion spring retaining plate 238 by a stop (not shown). Second torsion spring retaining plate 238 is coupled to first drive gear 244.

[0064] While one end of second axle 220 is coupled to gimbal block 204, the other end of second axle 220 is coupled to first drive device 242 comprising first drive gear 244, first worm gear 246 and first worm gear drive shaft 248. First worm gear drive shaft 248 may be coupled with, for example, a stepper motor (not shown) configured to rotate first worm gear drive shaft 248 and thereby first worm gear 246. First worm gear 246 is engaged with first drive gear 244, and rotation of first worm gear 246 causes a rotation of first drive gear 244 about second axis of rotation 222. First drive gear 244 is rotatable on second axle 220. Since first torsion spring 234 is coupled at one end to frame member 218, and the opposite end of first torsion spring 234 is coupled to first drive gear 244, and wherein second axle 220 is rotatable within frame member 218 and one end of second axle 220 is coupled to gimbal bock

204, a torque applied to second axle 220 will cause a rotation of caster wheel mounting member 202 about second axis of rotation 222. First torsion spring 234 may be coupled to frame member 218, such as by first torsion spring retaining plate 236, and to first drive gear 244 by second torsion spring retaining plate 238, such that with first worm gear 246 preventing rotation of first drive gear 244, torsion spring 234 applies a torque to second axle 220 that rotates caster wheel mounting member 202 about second axis of rotation 222 in a first direction of rotation 250.

[0065] The amount of torque applied to axle 220 by torsion spring 234 maybe adjusted by varying the amount of torsion applied to first torsion spring 234 by rotating first drive gear 244 with worm gear 246. More simply put, first torsion spring 234 may be "set" with a predetermined degree of torsion so that when the rotation of caster wheel mounting member 202 in a first direction of rotation 250 is at a maximum rotation, a predetermined amount of torque is nevertheless applied to the stationary shaft. The predetermined amount of torque applied by first torsion spring 234 will be hereinafter referred to as the set tensioning torque, and is the minimum torque applied to second axle 220 by first torsion spring 234.

[0066] A second torque applied in second direction of rotation 252 that is opposite from the first direction of rotation is resisted by the first torsion spring 234. If the second torque is greater than the set tensioning torque, the second torque will cause second axle 220 to rotate about second axis of rotation 22 in the second direction of rotation 252. However, first torsion spring 234 is configured such that rotation in the second direction of rotation increases the torque applied to second axle 220 by first torsion spring 234 in accordance, for example, with the spring constant of first torsion spring 234. This increased torque applied by first torsion spring 234 to second axle 220 will be hereinafter referred to as the dynamic tensioning torque. Second axle 220 will continue to rotate under the influence of the second applied torque until the dynamic tensioning torque equals the second applied torque, at which time second axle 220 will have reached an equilibrium angular position.

[0067] It should be apparent from the foregoing that the set tensioning torque can be adjusted by rotating first drive gear 244 using first worm gear 246. That is, first drive device 242 can be used to increase the set tensioning torque applied to second axle 220 by first torsion spring 234. More simply, with caster wheel mounting member 202 resting against a stop so that second axle 220 can no longer rotate in first direction of rotation 250, first drive device 242 can be used to increase the twist of first torsion spring 234 by rotating first drive gear 244 so that the set tensioning torque is increased. Accordingly, an increased second applied torque is required to move second axle 220 in the second direction of rotation 252. Looked at another way, rotation of second axle 220 in the second direction of rotation causes an increase in the force applied to drive second axle 220 in the first direction of rotation.

[0068] As best seen in FIGS. 9 A and 9C, fourth axle 230 is coupled to second force mechanism 260, such as second torsion spring 260. In accordance with FIGS. 9A and 9C, fourth axle 230 is coupled at one end to frame member 218. Fourth axle 230 extends from frame member 218 and passes through and is rotatable within bearing block 262. Bearing block 262 may be coupled to a base member (not shown) that positions caster assembly 200 adjacent glass ribbon 42. For example, the base member may be identical or similar to base member 224. Third torsion spring retaining plate 264 is coupled to bearing block 262, and fourth axle 230 extends through and is rotatable within third torsion spring retaining plate 264. Second torsion spring 266 is coupled to or at least retained at a first end by third torsion spring retaining plate 264. The second end of second torsion spring 260 is coupled to second drive device 268.

[0069] Second drive device 268, comprises second drive gear 270, second worm gear 272 and second worm gear drive shaft 274. Fourth torsion spring retaining plate 276 is coupled to second drive gear 270. Second drive gear 270 is rotatably engaged with fourth axle 230 such that second drive gear 270 is rotatable on fourth axle 230 about fourth axis of rotation 232. Second worm gear drive shaft 274 may be coupled to a source of rotational motion, for example, a stepper motor (not shown) configured to rotate second worm gear drive shaft 274 and thereby second worm gear 272.

[0070] Second worm gear 272 is engaged with second drive gear 270, and rotation of second worm gear 272 causes a rotation of second drive gear 270. The second end of second torsion spring 260 is coupled to or at least retained by fourth torsion spring retaining plate 276. Since second torsion spring 260 is coupled at one end to bearing block 262, and coupled at the opposite end to second drive gear 270, and wherein fourth axle 230 is rotatable within bearing block 262 and one end of fourth axle 230 is coupled to frame 218 through bearing bock 204, a torque applied to fourth axle 230 will cause a rotation of frame 218, and subsequently caster wheel mounting member 202, about fourth axis of rotation 232. With second torsion spring 234 rotatably engaged with bearing block 262 via third torsion spring retaining plate 264 and to second drive gear 270 via fourth torsion spring retaining plate 276, and with bearing block 262 rigidly mounted, second torsion spring 260 applies a torque to fourth axle 230 that rotates frame member 218, and caster wheel mounting member 202, about fourth axis of rotation 232. The amount of torque applied to fourth axle 230 by second torsion spring 260 may be adjusted by the amount of torsion applied to second torsion spring 260. More simply put, second torsion spring may be set by drive device 268 with a predetermined degree of torsion so that when the rotation of caster wheel mounting member 202 in a first direction of rotation 278 about fourth axis of rotation 262 is at a maximum rotation, a predetermined amount of torque is nevertheless applied to the stationary fourth axle. The predetermined amount of torque applied by second torsion spring 260 to fourth axle 230 will be hereinafter referred to as the set pinch torque, and is the minimum torque applied to fourth axle 230 by second torsion spring 260.

[0071] A second torque applied to fourth axle 230 in a second direction of rotation 280 that is opposite from the first direction of rotation is resisted by second torsion spring 260. If the second torque is greater than the set pinch torque, the second torque will cause fourth axle 230 to rotate about the fourth axis of rotation in the second direction of rotation 280.

However, second torsion spring 260 is configured such that rotation about fourth axis of rotation 232 in the second direction of rotation increases the torque applied to fourth axle 230 by second torsion spring 260 according to, for example, the spring constant of second torsion spring 260. This increased torque will be hereinafter referred to as the dynamic pinch torque, which is variable depending on the angular position of second axle 260. Fourth axle 260 will continue to rotate under the influence of the second applied torque until the dynamic pinch torque equals the second applied torque, at which time fourth axle 230 will have reached an equilibrium angular position.

[0072] It should be apparent from the foregoing that the set pinch torque can be adjusted by rotating fourth axle 230 using second drive device 268. That is, second drive device 268 can be used to increase the initial torque applied to fourth axle 230 by second torsion spring 260. More simply, with frame 218 against a stop, second drive device 268 canbe used to increase the twist of second torsion spring 260 so that the set pinch torque is increased. Accordingly, an increased second applied torque is required to rotate fourth axle 230 in the second direction of rotation. Looked at another way, rotation of fourth axle 230 in the second direction of rotation causes an increase in the force applied to fourth axle 230 in the first direction of rotation.

[0073] Summarizing, caster wheel 210 is configured to rotate about first axis of rotation 214.

Caster wheel mounting member 202 is configured to rotate about second axis of rotation 222 against the force applied by first force mechanism 234 (first torsion spring 234) such that rotation of caster wheel mounting member 202 about second axis of rotation 222 is resisted by first force mechanism 234. Caster wheel mounting member body portion 206 is configured to rotate about third axis of rotation 226. Frame member 218 (and consequently caster wheel mounting member 202) is configured to rotate about fourth axis of rotation 232 against the force applied to fourth axle 230 by second force mechanism 260 such that rotation of caster wheel mounting member 202 about fourth axis of rotation 232 is resisted by second force mechanism 260 (e.g. torsion spring 260). While not shown, mechanical stops may be used where necessary to limit the rotational motion of the foregoing components.

[0074] As can be seen from FIGS. 9B and 9C, during operation second axis of rotation 222 is generally perpendicular to the surface of glass ribbon 128 contacted by caster wheel 210, whereas axis of rotation 232 is generally parallel with the contacted surface of glass ribbon 128. It should further be noted that caster assembly 200 may be configured such that third axis of rotation 226 forms a non-zero angle β with the surface of glass ribbon 42 contacted by caster wheel 210 (see FIG. 89). The angle β introduced to third axle 224 helps avoid flutter or wobble of body portion 206 about third axis of rotation 226. In some embodiments, caster assembly 200 may be designed so that third axis of rotation 226 intersects glass ribbon 128 at a location 282 where caster wheel 210 contacts the glass ribbon.

[0075] The following will describe the operation of the caster assemblies 100 in respect of moving ribbon of glass 42 and FIGS. 8 and 11. As shown in FIG. 11, molten glass 16 descends downward from forming body 32 as continuously moving glass ribbon 42. Glass ribbon 42 is engaged by and drawn downward in a draw direction 50 by pulling rolls 44. Draw direction 50 is typically, but not necessarily, a vertical direction. As glass ribbon descends from forming body 32, the glass ribbon cools from a viscous material to an elastic material. A scoring apparatus 48 is positioned below pulling rolls 44 and is configured to engage glass ribbon 42 in an elastic portion thereof and form a lateral score in the glass ribbon in a direction generally perpendicular to draw direction 50. Scoring apparatus 48 may in some embodiment be configured to translate in a direction parallel with the draw direction.

[0076] FIG. 11 further illustrates a set of caster assemblies positioned adjacent the lateral edge portions 54 of glass ribbon 42. Each set of caster assemblies 100 consists of two pair of caster assemblies, wherein a first pair of caster assemblies is positioned adjacent to one lateral edge portion 54 and a second pair of caster assemblies 100 is positioned adjacent the opposite lateral edge portion of glass ribbon 42. Additionally, referring to FIG. 8, each pair of caster assemblies 100 includes a first caster assembly positioned on one side of glass ribbon 42 adjacent an edge portion 54 and a second caster assembly 100 positioned on the opposite side of glass ribbon 42 adjacent the same edge portion 54. Each caster assembly of the set of caster assemblies is typically positioned an equal distance from root 40 of forming body 32.

[0077] Referring to FIG. 6, just prior contact between caster wheel 104 and glass ribbon 42, the force applied to caster wheel mounting member 102 by force mechanism 120 (e.g. torsion spring 120) causes the torsion wheel mounting member 102 to rotate to a position of maximum rotation until the rotation of caster wheel mounting member 102 is in a stable initial position, and the plane 130 of the caster wheel makes an angle with draw direction 50. In the instance illustrated in FIG. 6, caster wheel mounting member 102 rotates is rotated in a clockwise direction. As base member 124 moves caster assembly 100 so that caster wheel 104 contacts a surface of glass ribbon 42 that is moving in draw direction 50, caster wheel mounting member 102 the interaction between caster wheel 104 and moving glass ribbon 42 causes caster wheel mounting member 102 to rotate in a counter-clockwise rotation against the force applied to caster wheel mounting member 102 by torsion spring 120. As caster wheel mounting member 102 rotates in the counter-clockwise direction, the torsion applied to torsion spring 120 increases, and thereby the force applied to caster wheel mounting member 102 my torsion spring 120 also increases. When the frictional forces between caster wheel 104 and glass ribbon 42, combined with the downward movement of glass ribbon 42 and the resistance to flattening contributed by the glass ribbon, are balanced by the increased force applied to caster wheel mounting member by torsion spring 120, caster wheel mounting member 102, and caster wheel 104, reach and equilibrium position on glass ribbon 42.

[0078] Put more simply, when caster wheel 104 contacts the continuously moving glass ribbon 42, movement of the glass ribbon rotates caster wheel mounting member 102 to align the plane 130 of the caster wheel with the direction of movement of the glass ribbon (the draw direction 50). However, rotation of caster wheel mounting member produced by contact with the glass ribbon produces a twisting in torsion spring 120, thereby increasing the force applied by torsion spring 120 against caster wheel mounting member 102, tending to rotate caster wheel mounting member in the opposite direction of rotation. Thus, an outward lateral force is applied to the edge portion of the moving glass ribbon in a direction away from a centerline of the glass ribbon.

[0079] While the proceeding description of operation involved only a single caster assembly

100, is should be remembered that a second caster assembly is positioned on an opposite side of the glass ribbon so that an edge portion of the glass ribbon is pinched between the two caster assemblies, as shown in FIG. 8. Moreover, it should also be recognized that in accordance with FIG. 11, a second pair of caster assemblies is similarly positioned along the opposite edge portion of the glass ribbon and configured such that the second pair of caster assemblies is also applying an outward lateral force to the glass ribbon in a direction opposite to the lateral force applied by the first pair of cater assemblies. Thus, the two pairs of caster assemblies engaged with the continuously moving glass apply opposing lateral forces in the glass ribbon that flattens the glass ribbon.

[0080] Referring again to FIG. 11 in respect of caster assemblies 200, it should be readily apparent from the foregoing that caster assemblies 200 can be substituted for caster assemblies 100 so that two pair of caster assemblies are positioned to engage with opposing edge portions of glass ribbon 42 and apply opposing outwardly directed lateral forces on the glass ribbon that tension the glass ribbon in a direction generally perpendicular to draw direction 50. However, while caster assemblies 100 and 200 are similar, their different designs result in similar but different methods of operation. As previously described, first force mechanism 234 (e.g. torsion spring 234) is configured to urge caster wheel mounting member 202 in a rotation about second axis of rotation 222 in a direction of rotation that applies an outward lateral force to glass ribbon 42. Drive device 242 can be used to set the minimum outward force (set tensioning force) by applying more or less torsion to torsion spring 234. The greater the torsion applied to torsion spring 234, the greater the outward lateral force applied to the glass ribbon. Accordingly, drive device 242 can be used to adjust the lateral outward force. In some embodiments, drive device 242 can be electrically coupled to a controller, where a force set point signal developed by the controller is compared to a force signal provided by a load cell coupled to the caster assembly. An error signal comprising the difference between the set point and the force signal can then be used to control drive device 242, which can increase or decrease the applied tension force to the glass ribbon. In other embodiment, tension in the glass ribbon can be measured during the drawing process, wherein this real-time tension can be provided to the system controller and an error signal developed that represents the difference between the actual ribbon tension and the set point tension. The error signal can be used to control drive device 242.

[0081] Similarly, second force mechanism 260 and drive device 268 can be used to control the normal force applied to glass ribbon 42 by caster assembly 200. This normal force can be referred to as the pinch force when a first caster assembly is positioned on a first side of the glass ribbon, and a second caster assembly is positioned on a second side of the glass ribbon and the first and second caster assemblies are positioned such that the glass ribbon is pinched between the caster wheels of the first and second caster assemblies. Accordingly, the drive device 268 of each caster assembly of the caster assembly pair (i.e. the first and second caster assemblies) can be used to vary the amount of pinch force by applying more or less torsion to the second force mechanism (e.g. second torsion spring 260).

[0082] In use, each caster assembly 200 may include a base member similar to base member 124 can provide either linear motion or rotary motion to the caster assembly so that the caster assembly can be moved into engagement with the glass ribbon, or disengagement with the glass ribbon.

[0083] FIG. 12 further illustrates a set of caster assemblies 200 positioned adjacent the lateral edge portions 54 of glass ribbon 42. Each set of caster assemblies 200 consists of two pair of caster assemblies, wherein a first pair of caster assemblies is positioned adjacent to one lateral edge portion 54 and a second pair of caster assemblies 200 is positioned adjacent the opposite lateral edge portion of glass ribbon 42. Additionally, referring to FIG. 8, each pair of caster assemblies 200 includes a first caster assembly positioned on one side of glass ribbon 42 adjacent an edge portion 54 and a second caster assembly 200 positioned on the opposite side of glass ribbon 42 adjacent the same edge portion 54. Each caster assembly of the set of caster assemblies is typically positioned an equal distance from root 40 of forming body 32.

[0084] Referring to FIG. 13, just prior contact between caster wheel 210 and glass ribbon 42, the force applied to caster wheel mounting member 102 by force mechanism 234 (e.g. torsion spring 234) causes the torsion wheel mounting member 202 to rotate to a position of maximum rotation in a first direction until the rotation of caster wheel mounting member 202 is in a stable initial position, and the plane 228 of the caster wheel makes an angle a with draw direction 50. In the instance illustrated in FIG. 13, caster wheel mounting member 202 is rotated in a counter-clockwise direction. As caster assembly 200 is moved, such as via a base member 124 so that caster wheel 210 contacts a surface of glass ribbon 42 that is moving in draw direction 50, the interaction between caster wheel 210 and moving glass ribbon 42 causes caster wheel mounting member 202 to rotate in a clockwise rotation against the force applied to caster wheel mounting member 202 by first torsion spring 234. As caster wheel mounting member 202 rotates in the clockwise direction, the torsion applied to torsion spring 234 increases, and thereby the force applied to caster wheel mounting member 202 by torsion spring 234 also increases. When the frictional forces between caster wheel 210 and glass ribbon 42, combined with the downward movement of glass ribbon 42 and the resistance to flattening contributed by the glass ribbon, are balanced by the increased force applied to caster wheel mounting member by first torsion spring 234, caster wheel mounting member 202, and caster wheel 210, reach an equilibrium position on glass ribbon 42.

[0085] Put more simply, when caster wheel 210 contacts the continuously moving glass ribbon 42, movement of the glass ribbon rotates caster wheel mounting member 202 in a direction of rotation to align the plane 228 of the caster wheel with the direction of movement of the glass ribbon (the draw direction 50). However, rotation of caster wheel mounting member 202 produced by contact with the glass ribbon produces a twisting in first torsion spring 234, thereby increasing the force applied by first torsion spring 234 against caster wheel mounting member 202, tending to rotate caster wheel mounting member in the opposite direction of rotation. Thus, an outward lateral force is applied to the edge portion of the moving glass ribbon in a direction away from a centerline of the glass ribbon.

[0086] While the proceeding description of operation involved only a single caster assembly 200, is should be remembered that a second caster assembly is positioned on an opposite side of the glass ribbon so that an edge portion of the glass ribbon is pinched between the two caster assemblies, as shown in FIG. 12. Moreover, it should also be recognized that in accordance with FIG. 11, a second pair of caster assemblies is similarly positioned along the opposite edge portion of the glass ribbon and configured such that the second pair of caster assemblies is also applying an outward lateral force to the glass ribbon in a direction opposite to the lateral force applied by the first pair of cater assemblies. Thus, the two pairs of caster assemblies engaged with the continuously moving glass apply opposing lateral forces in the glass ribbon that flattens the glass ribbon. As described above, first drive device 242 can be used to vary the outward lateral force and thereby the tension applied to the glass ribbon, whereas second drive device 268 can be used to vary the pinch force. A stop, such as set screw 298, can be used to limit the rotational motion of caster wheel mounting member 202.

[0087] In still another embodiment illustrated in FIG. 14, caster assemblies 100 or 200 can be used in conjunction with a scoring apparatus 300 wherein a scoring device comprising scoring apparatus 300 travels at an angle relative to draw direction 50, as indicated by double headed arrow 302. Accordingly, scoring apparatus 300 is not required to move in the draw direction to ensure no relative motion parallel with the draw direction occurs during the scoring process. This facilitates placement of a second set of caster assemblies below the scoring apparatus with interfering with the motion of robots or other apparatus below the scoring apparatus.

[0088] FIG. 15 is a graph of modeled data of the effect of a set of caster assemblies on a continuously moving glass ribbon. The vertical axis represents the distance between the glass ribbon and a plane tangent to the glass ribbon at the centerline position. That is, the vertical axis represents the departure of the glass ribbon from a planar shape as a function of distance from the centerline of the glass ribbon (horizontal axis). The glass ribbon was assumed to have an average thickness of 0.3 mm, a width of 1800 mm, a longitudinal downward draw force of about 7 kg and a cylindrical curvature (bow) of 25 mm, where the curvature is measured as the maximum deviation from a plane. Curve 304 represents the curvature in the glass ribbon prior to engaging the opposing pairs of caster assemblies, and curve 306 represents curvature of the glass ribbon after engaging edge portions of the glass ribbon with opposing pairs of caster assemblies. The data show a significant improvement of the "flatness" of the ribbon in a width direction by using caster assemblies disclosed herein.

[0089] As previously described, although the caster assemblies disclosed herein have been presented in respect of a glass forming process, the caster assemblies may be employed in other apparatus and systems wherein a thin glass ribbon 42 is conveyed from one location to another location. For example, as shown in FIG. 16, a thin, flexible glass ribbon 42 may be paid out (dispensed) from a source reel 400 and taken up (received) by a take-up reel 402. The glass may have a thickness equal to or less than 0.3 mm, equal to or less than 0.1 mm, or equal to or less than 0.05 mm. The radius of the source reel or the take-up reel will vary as a function of the thickness of the glass ribbon. Various processing equipment represented by reference numeral 404 maybe positioned between source reel 400 and take-up reel 402 to further process the glass ribbon. For example, such processing equipment maybe used to grind and/or polish edges of the glass ribbon, apply a handling tape to the edges of the glass ribbon, deposit other materials onto the glass ribbon without limitation such as protective films or electronic functional materials such as semiconductor materials. Caster assemblies 100 and/or 200 as described herein may be used to apply a tension across a width of the glass ribbon to reduce curvature of the glass ribbon that can improve the processing of the glass ribbon, depending on the specific process.

[0090] 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 thereof. Thus it is intended that the present embodiments cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. An apparatus for manufacturing glass comprising:

a forming body from which molten glass is drawn to produce a continuously moving glass ribbon;

a caster assembly positioned below the forming body and configured to engage with the moving glass ribbon, the caster assembly comprising:

a caster wheel mounting member;

a caster wheel rotatably coupled to the caster wheel mounting member and rotatable about a first axis of rotation;

a frame member rotatably coupled to the caster wheel mounting member, the caster wheel mounting member being rotatable about a second axis of rotation;

a first force mechanism configured to apply a first force to the caster wheel mounting member that urges the caster wheel mounting member in a rotation about the second axis of rotation; and

wherein a plane perpendicular to and passing through the first axis of rotation intersects the second axis of rotation.

2. The apparatus according to claim 1, further comprising a scoring apparatus positioned below the forming body relative to a draw direction, and wherein the caster assembly is positioned between the forming body and the scoring apparatus.

3. The apparatus according to claim 1, wherein the caster assembly further comprises a drive mechanism coupled to the first force device and configured to vary the first force applied to the caster wheel mounting member.

4. The apparatus according to claim 1, wherein the caster wheel mounting member comprises a gimbal block and a body portion rotatably coupled to the gimbal block, and wherein the body portion is rotatable about a third axis of rotation.

5. The apparatus according to claim 4, wherein the third axis of rotation intersects the moving glass ribbon at a location on the moving glass ribbon where the caster wheel is configured to engage with the moving glass ribbon.

6. The apparatus according to claim 4, wherein the third axis of rotation intersects a surface of the moving glass ribbon at a non-zero angle.

7. The apparatus according to claim 1, wherein the caster wheel mounting member is configured to rotate about a fourth axis of rotation perpendicular to the second axis of rotation.

8. The apparatus according to claim 7, further comprising a second force mechanism configured to apply a second force to the caster wheel mounting member and urge the caster wheel mounting member in a rotation about the fourth axis of rotation.

9. The apparatus according to claim 8, further comprising a second drive device coupled to the second force mechanism and configured to vary the second force.

10. The apparatus according to claim 1 , wherein the caster assembly is movable between an engaged position and a disengaged position relative to the moving glass ribbon, wherein in the engaged position the caster wheel is in contact with the moving glass ribbon, and in the disengaged position the caster wheel is not in contact with the moving glass ribbon.

11. The apparatus according to claim 1 , wherein the frame member is rotatably coupled to a base member configured to rotate the frame member such that the caster wheel is engaged and disengaged with the glass ribbon.

12. The apparatus according to claim 1 , wherein the frame member is coupled to a linear slide configured to translate the frame member such that the caster wheel is engaged and disengaged with the glass ribbon.

13. An apparatus for processing a glass ribbon comprising:

a source reel comprising a length of glass ribbon;

a take-up reel configured to receive the length of glass ribbon from the source reel; a caster assembly positioned between the source reel and the take-up reel and configured to engage with the glass ribbon, the caster assembly comprising:

a caster wheel mounting member; a caster wheel rotatably cou led to the caster wheel mounting member and rotatable about a first axis of rotation;

14. The apparatus according to claim 13, wherein the caster assembly further comprises a drive mechanism coupled to the first force device and configured to vary the first force applied to the caster wheel mounting member.

15. The apparatus according to claim 13, wherein the caster wheel mounting member comprises a gimbal block and a body portion rotatably coupled to the gimbal block, and wherein the body portion is rotatable about a third axis of rotation.

16. The apparatus according to claim 15, wherein the third axis of rotation intersects the glass ribbon at a location on the glass ribbon where the caster wheel is configured to engage with the glass ribbon.

17. The apparatus according to claim 15, wherein the third axis of rotation intersects a surface of the glass ribbon at a non-zero angle.

18. The apparatus according to claim 13, wherein the caster wheel mounting member is configured to rotate about a fourth axis of rotation perpendicular to the second axis of rotation.

19. The apparatus according to claim 18, further comprising a second force mechanism configured to apply a second force to the caster wheel mounting member and urge the caster wheel mounting member in a rotation about the fourth axis of rotation.

20. The apparatus according to claim 19, further comprising a second drive device coupled to the second force mechanism and configured to vary the second force.

21. The apparatus according to claim 13, wherein the caster assembly is movable between an engaged position and a disengaged position relative to the glass ribbon, wherein in the engaged position the caster wheel is in contact with the glass ribbon, and in the disengaged position the caster wheel is not in contact with the glass ribbon.

22. The apparatus according to claim 13, wherein the frame member is rotatably coupled to a base member configured to rotate the frame member such that the caster wheel is engaged and disengaged with the glass ribbon.

23. The apparatus according to claim 13, wherein the frame member is coupled to a linear slide configured to translate the frame member such that the caster wheel is engaged and disengaged with the glass ribbon.

24. A method of drawing a glass ribbon comprising:

flowing molten glass from a forming body to form a glass ribbon, the glass ribbon moving in a draw direction;

engaging the glass ribbon with a caster assembly, the caster assembly comprising:

a caster wheel mounting member;

wherein the engaging causes the caster wheel mounting member to rotate about the second axis of rotation in opposition to the first force, the first force thereby forming a tension force in the glass ribbon in a direction away from a centerline of the glass ribbon.

25. The method according to claim 24, wherein a plane passing through and perpendicular to the first axis of rotation forms an angle a relative to the draw direction after the engaging.

26. The method according to claim 25, wherein a is in a range from 0 to 5 degrees.

27. The method according to claim 24, wherein the first force mechanism is coupled to a first drive device, the method further comprising varying the first force with the first drive device.

28. The method according to claim 24, wherein the caster wheel mounting member comprises a gimbal block and a body portion, and wherein the body portion is coupled to the gimbal portion and rotatable about a third axis of rotation relative to the gimbal block.

29. The method according to claim 24, wherein the caster assembly further comprises a second force mechanism configured to apply a second force to rotate the caster wheel mounting member about a fourth axis of rotation perpendicular to the second axis of rotation.

30. The method according to claim 29, wherein the caster assembly further comprises a second drive device coupled to the second force mechanism, the method further comprising using the second drive device to vary the second force.

31. The method according to claim 29, further comprising varying the second force to vary a normal force applied against the glass ribbon by the caster wheel.

32. The method according to claim 29, further comprising varying the second force in response to a change in lateral tension in the glass ribbon.

33. The method according to claim 24, further comprising varying the first force to vary a lateral tension in the glass ribbon.

34. A method of conveying a glass ribbon comprising:

paying out a glass ribbon from a source reel;

taking up the glass ribbon from the source reel onto a take-up reel; engaging the glass ribbon between the source reel and the take-up reel with a caster assembly, the caster assembly comprising:

a caster wheel mounting member

35. The method according to claim 34, wherein a plane passing through and perpendicular to the first axis of rotation forms an angle a relative to the draw direction after the engaging.

36. The method according to claim 35, wherein a is in a range from 0 to 5 degrees.

37. The method according to claim 34, wherein the first force mechanism is coupled to a first drive device, the method further comprising varying the first force with the first drive device.

38. The method according to claim 34, wherein the caster wheel mounting member comprises a gimbal block and a body portion, and wherein the body portion is coupled to the gimbal portion and rotatable about a third axis of rotation relative to the gimbal block.

39. The method according to claim 34, wherein the caster assembly further comprises a second force mechanism configured to apply a second force to rotate the caster wheel mounting member about a fourth axis of rotation perpendicular to the second axis of rotation.

40. The method according to claim 39, wherein the caster assembly further comprises a second drive device coupled to the second force mechanism, the method further comprising using the second drive device to vary the second force.

41. The method according to claim 39, further comprising varying the second force to vary a normal force applied against the glass ribbon by the caster wheel.

42. The method according to claim 39, further comprising varying the second force in response to a change in lateral tension in the glass ribbon.

43. The method according to claim 34, further comprising varying the first force to vary a lateral tension in the glass ribbon.