WO2012004625A1

WO2012004625A1 - Apparatus and method for continuous shaping of a glass ribbon

Info

Publication number: WO2012004625A1
Application number: PCT/IB2010/002049
Authority: WO
Inventors: Thierry Luc Alain Dannoux
Original assignee: Corning Incorporated
Priority date: 2010-07-08
Filing date: 2010-07-08
Publication date: 2012-01-12
Also published as: JP2013530922A; CN103003208A; KR20130040232A; JP5571852B2; TW201206846A; TWI503291B

Abstract

In the formation of sheet material from molten glass, pairs (41) of offset shaping rollers (40) are used to produce curved shapes in a glass ribbon (34) as the ribbon is being formed. When the glass ribbon is later separated, the curved portions of the ribbon become curved edges (16) that can wrap around the edges of display products such as computer monitors or televisions that the cover sheets can be installed on. Embodiments of the present invention can be used to eliminate off line reheating and reshaping of individual glass sheets used in conventional glass shaping processes.

Description

APPARATUS AND METHOD FOR CONTINUOUS SHAPING OF A GLASS RIBBON

FIELD

[0001] This invention relates to a method and apparatus for shaping a continuous flowing ribbon of molten glass, and more particularly to a method and apparatus for forming curved surfaces in a continuously flowing ribbon of molten glass in a glass sheet forming process.

BACKGROUND

[0002] When molten glass is drawn into sheet form, the glass is stretched or attenuated from an initial delivered thickness to a final sheet thickness. In an overflow downdraw process such as the fusion process, where molten glass flows downwardly along opposed converging sides of a forming member and is withdrawn as a single ribbon of glass from the root or bottom edge thereof, great effort is expended ensuring a flat, uniform thickness of the glass sheet. The resulting flat sheets of glass are then combined with appropriate components (e.g. liquid crystal material and associated electronics) to produce a display device. The display device may then be incorporated into an end product, such as a computer monitor or a television. Typically, the display device is confined within a frame or bezel that provides structural integrity and border.

[0003] Recent trends in the display industry point to increasingly thinner devices. One such example is light emitting diode backlighting for televisions that allow for a dramatically thinner device compared to earlier cold cathode fluorescent lighting. Additional steps are being undertaken to significantly reduce, or eliminate, the frame around the display to provide a simple, cleaner and more aesthetically pleasing appearance to the overall product. One method of producing a product of this type is to include a faceplate or cover glass that wraps around the product front, and in particular the edge area of the product.

[0004] In the past, the shaping of individual sheets of glass has been done largely through heating and pressing, or heating and slumping. That is, an individual sheet of glass is heated to an appropriate forming temperature, then pressed to obtain the final shape. Alternatively, during slumping the sheet is placed in a mold, heated, and allowed to conform to the desired shape via gravity. Such methods have been restricted to actions taken on a sheet by sheet basis, and while multiple glass sheets may be acted on during a single step (by employing multiple molds for example), the process suffers from the lack of an economy of scale that could be achieved by a continuous, non-stop process.

SUMMARY

[0005] In accordance with one embodiment, an apparatus for continuous shaping of a moving ribbon of molten glass is disclosed. In one embodiment, the moving ribbon of molten glass is formed in a downdraw glass making process, such as a fusion downdraw process. As used herein, the term molten glass is used to denote a viscous or viscoelastic material that, when cooled, can produce a glassy elastic material. The method includes the use of offset shaping roller pairs that engage the molten glass ribbon during the production of the ribbon, and produce a - curvature in the moving ribbon of molten glass. Thus, as long as the forming body producing the molten glass ribbon is supplied with molten glass, a continuous molten glass ribbon is produced, and the offset shaping rollers engaged with the ribbon form curved portions in the ribbon. Once the glass ribbon has reached an elastic state, the ribbon can be sectioned, both lengthwise and widthwise, to produce individual glass sheets having curved surfaces, and in particular curved edges, that can be used in a manufacture of wrap-around faceplates for various display products.

[0006] In one embodiment, an apparatus for shaping a continuously moving ribbon of molten glass, such as may be used in a downdraw glass making process, is disclosed comprising a forming body for producing a moving ribbon of molten glass and an offset shaping roller pair disposed downstream of the forming body relative to a direction of flow of the ribbon of molten glass to impart a three-dimensional shape to the ribbon. The offset shaping roller pair comprises a first shaping roller positioned adjacent to and in contact with a first side of the moving ribbon of molten glass and a second shaping roller positioned adjacent to and in contact with a second side of the glass ribbon. The first and second opposing offset shaping rollers are laterally offset from each other, and a contact surface of the first roller where the first roller contacts the moving ribbon of molten glass extends past a contact surface of the second roller where the second roller contacts the moving ribbon of molten glass, thereby producing curvature in the moving ribbon of molten glass. Positioning the first and second shaping rollers each in a direction where they pass or overlap each other causes the rollers to impart a curvature in the ribbon. Preferably, a viscosity of the moving ribbon of molten glass contacted by the first and second shaping rollers is in a range between lxlO⁵ and lxlO⁷ Poise.

[0007] In some embodiments, a plurality of offset shaping roller pairs are in contact with the moving ribbon of molten glass. The plurality of offset shaping roller pairs may, for example, be at different vertical positions relative to a root of the forming body. Alternatively, the plurality of offset shaping roller pairs may lie along a single horizontal plane. That is, the roller pairs may be vertically displaced relative to the forming body root, where a first shaping roller pair is positioned at a first vertical distance from the forming body root, while a second shaping roller pair is positioned a second distance from the forming body root.

[0008] A distance between a midpoint of a first shaping roller and a midpoint of a second shaping roller of a given shaping roller pair is preferably greater than a length of either the first or second shaping roller. In addition, a distance between the nearest ends of the first and second shaping rollers is preferably less than a length of either the first or second shaping roller.

[0009] In accordance with another embodiment, a method of shaping a moving ribbon of material is described comprising forming a moving ribbon of material having first and second major surfaces, the ribbon of material comprising a viscoelastic portion and an elastic portion, contacting the first major surface of the ribbon of material in the viscoelastic portion with a first shaping roller and contacting the second major surface of the ribbon of material in the viscoelastic portion with a second shaping roller laterally offset from the first shaping roller. The first and second shaping rollers form an offset shaping roller pair, and contact with the ribbon by the offset shaping roller pair produces a first curvature in the ribbon. A distance between the nearest ends of the first and second shaping rollers is preferably less than a length of either the first or second shaping roller. A distance between a midpoint of the first shaping roller and a midpoint of the second shaping roller of a given roller pair is preferably greater than a length of either the first or second shaping roller. The ribbon of material may, for example, comprise a glass material. The ribbon of material may comprise a glass-ceramic or a plastic, such as a thermoplastic. The ribbon of material may comprise a metal. Preferably, a viscosity of the ribbon of material contacted by the first and second shaping rollers is in the range between about lxlO⁵ and lxlO⁷ Poise. Each of the first and second shaping rollers may comprise a flange. Because of the close proximity between edges of the flanges, a score line is formed in the ribbon where the glass between the shaping rollers is pinched and thinned by the flanges.

[OOIO] In some embodiments, pluralities of curvature are induced in the ribbon of material by a plurality of offset shaping roller pairs contacting the ribbon.

[0011] Once the ribbon has been shaped, the ribbon may be separating to form a sheet of material having the first curvature. Separation may be performed by conventional means, such as by mechanical scoring and then flexing the ribbon ("score and snap"), or by laser scoring and/or cutting. For example, the ribbon can be separated across its width to form a sheet of material, and the sheet can be separated along the first curvature to produce sub-sheets of material having one or more curved edges. These sub-sheets may be further processed, such as by finishing (e.g. grinding or polishing the cut edges) to form a cover glass or faceplate.

[0012] In still another embodiment, a method of forming a sheet of glass having a curved edge is disclosed comprising forming a moving ribbon of material having first and second major surfaces, the ribbon of material comprising a viscoelastic portion and an elastic portion, contacting the first major surface of the ribbon of material in the viscoelastic portion with a first shaping roller and contacting the second major surface of the ribbon of material in the viscoelastic portion with a second shaping roller laterally offset from the first shaping roller. The first and second shaping rollers form an offset shaping roller pair, and contact with the ribbon by the offset shaping roller pair produces a first curvature in the ribbon. The ribbon of material can be separated across a width of the ribbon in the elastic portion to form a glass sheet having the first curvature. Subsequently, the glass sheet can be separated along the first curvature to produce sub-sheets with one or more curved edges. Preferably, a distance between the nearest ends of the first and second shaping rollers is less than a length of either the first or second shaping roller. A viscosity of the ribbon of material contacted by the first and second shaping rollers is preferably in the range between about lxlO⁵ and lxlO⁷ Poise.

[0013] In some embodiments, each of the first and second shaping rollers comprises a flange, and a score line is formed in the ribbon by the flanges where the flanges pinch and thin the ribbon.

[0014] In some embodiments a plurality of curvatures can be formed in the ribbon by contacting the ribbon of material with a plurality of offset shaping roller pairs. The plurality of offset shaping roller pairs may be positioned at different vertical locations relative to a root of the forming body.

[0015] Additional features and advantages of the invention are 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 invention as described herein. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. It is to be understood that the various features of the invention disclosed in this specification and in the drawings can be used in any and all combinations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is an edge view of a portion of a device, such as a television display, shown viewing the device edge-on, and with a wrap-around faceplate depicted partially pulled away.

[0017] FIG. 2 is a side view of an exemplary fusion downdraw glass making apparatus according to an embodiment of the present invention. [0018] FIG. 3 is a cross sectional view of the fusion downdraw apparatus of FIG. 2.

[0019] FIG. 4A is a top down view of a plurality of offset shaping roller pairs engaged with a glass sheet as viewed from above (the glass ribbon in cross section).

[0020] FIG. 4B is a close up view a central shaping roller pair of FIG. 4A.

[0021] FIG. 5 is a perspective view of the offset shaping rollers of FIG. 3 engaged with a continuously moving ribbon of glass.

[0022] FIG. 6 is a cross sectional view of a glass ribbon formed with a glass making apparatus (shown in cross section across a width of the ribbon) according to embodiments of the present invention, and illustrating locations for cutting the ribbon longitudinally.

[0023] FIG. 7 shows the two sections (sub-sheets) of glass produced by cutting or separating the ribbon portion of FIG. 6 at the indicated cutting locations.

[0024] FIG. 8 is close-up view of several offset shaping rollers according to an embodiment of the present invention, wherein the rollers engage with the glass ribbon to produce a curved arcuate shape, and wherein flanges on the rollers produce a thinned portion in the arcuate shape to facilitate separating the ribbon.

[0025] FIG. 9 is another close-up view of several offset shaping rollers according to an embodiment of the present invention, wherein the rollers engage with the glass ribbon to produce a curved arcuate shape, and wherein flanges on the rollers produce a thinned portion in the arcuate shape to facilitate separating the ribbon.

[0026] FIG. 10 is another close-up view of the offset shaping roller pair of FIGS. 8 and 9, shown without the glass.

DETAILED DESCRIPTION

[0027] In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one having ordinary skill in the art, having had the benefit of the present disclosure, that the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omitted so as not to obscure the description of the present invention. Finally, wherever applicable, like reference numerals refer to like elements.

[0028] Shown in FIG. 1 is an edge portion of a display product 10, such as a television or computer monitor, illustrating the placement of a wrap-around cover or faceplate glass 12 that will be fitted to the front (viewer side) of a display device 14 comprising the display product. By wrap-around what is meant is that a curved edge portion 16 of the cover glass deviates from the plane of the majority of a surface of the glass cover plate. When placed over an appropriate display product, curved edge portion 16 of the cover glass wraps or folds around at least a portion of the thickness of the display. The end result is a smooth, aesthetically pleasing display front. The manufacture of such cover glass sheets is the subject of the following disclosure.

[0029] FIGS. 2 and 3 depict an apparatus 20 for drawing a glass ribbon from a viscous material according to an exemplary fusion downdraw process. The viscous material is preferably a molten glass material, but may, according to some embodiments, be a glass-ceramic material or a plastic material. The following description will be presented in the context of a molten glass material.

[0030] Apparatus 20 comprises forming body 22 having an upper channel or trough 24 disposed therein. Forming body 22 includes converging forming surface 26a and converging forming surface 26b, the converging forming surfaces converging at a lower edge 28. Lower edge 28 represents a draw line from where molten glass 30 is drawn from forming body 22. Lower edge 28 may also be referred to as root 28. Molten glass 30 is supplied to trough 24 through inlet 31, and overflows the trough such that the molten glass flows over upper edges of the trough and down converging forming surfaces 26a, 26b as two separate flows of molten glass. These separate flows of molten glass reunite, or fuse, at the forming body root, and continue downward in direction of travel 32 from the root as a single ribbon of glass 34. Hence, the process is sometimes referred to as the fusion process, or the fusion downdraw process. Those portions of the molten glass contacting the forming surfaces of forming body 22 are positioned within the interior of the fused ribbon drawn from root 28, leaving the outer surfaces of the ribbon in a pristine condition as they leave the forming body.

[0031] Once ribbon 34 leaves the forming body root 28, it transitions from a viscosity liquid state through a viscoelastic state to a final elastic state. The ribbon is typically engaged in the viscous or viscoelastic state between counter-rotating edge rollers 36 positioned at each longitudinal edge 38 of the ribbon. The viscosity of the molten glass is preferably between lxlO⁵ and lxlO⁷ Poise. Edge rollers 36 may be driven by motors (not shown) or un-driven. Driven edge rollers 36, for example, are used to supplement gravity and aid in applying a pulling force to the glass ribbon. Both driven and un-driven edge rollers serve to maintain the width of the ribbon by reducing shrinking or attenuation of the ribbon width. Opposing edge rollers 36 are positioned at vertically equal locations relative to root 28 (e.g. such that a horizontal plane passing through an axis of rotation of one edge roller of the opposing edge roller pair also passes through the axis of rotation of the other edge roller of the edge roller pair), and directly opposite each other, so that the position of one roller of the opposing edge roller pair is mirrored across the ribbon by the position of the other, counter-rotating roller of the edge roller pair. Horizontally, opposing edge rollers 36 are equally positioned such that each roller of an opposing edge roller pair is directly opposite the other roller of the opposing edge roller pair.

[0032] In accordance with one embodiment of the present invention, glass ribbon 34 descending from forming body 22 in direction of travel 32 is further engaged by counter-rotating shaping rollers 40 shown in FIGS. 4A, 4B and 5. The shaping rollers form a shaping roller pair 41, and are positioned in an offset manner on surfaces 42 and surface 44, respectively of the ribbon, i.e. adjacent the two major surface areas of the ribbon. That is, a first shaping roller is positioned adjacent surface 42 of the ribbon and turns in a first direction, while a second shaping roller is positioned adjacent surface 44 of the ribbon and turns in the opposite direction. Each shaping roller includes a shaft 46. A plurality of shaping rollers 40 and shaping roller pairs 41 may be used. Although shown having individual shafts in FIGS. 4A and 4B, each shaping roller 40 disposed on a given side of the moving ribbon 34 can be coupled to a single, common shaft (see FIG. 5) if the axis of rotation of each shaping roller is positioned equidistant from root 28. The shaping rollers may be driven in a manner similar to driven edge rollers, but may also be un-driven. A shaping roller of the first shaping roller pair contacts first surface 42 of the ribbon along a contact surface of the first shaping roller, while the second roller contacts second surface 44 of the ribbon along a contact surface of the second shaping rollers. However, unlike the edge rollers described supra, the shaping rollers of a shaping roller pair are staggered or offset laterally (horizontally). This offset can be better understood with the aid of FIG. 4B.

[0033] The view of FIG. 4A is looking downward across a cross sectional width of the ribbon, and dashed line 48 represents an imaginary plane seen edge-on passing through the centerline of the ribbon. Looking at the center shaping roller pair from FIG. 4A, the shaping roller pair 41 of FIG. 4B consists of a first shaping roller 40a and a second shaping roller 40b, the first shaping roller 40a is displaced to one side of the ribbon centerline 48, while the second shaping roller 40b is displaced to the opposite side of the centerline 48 from the first shaping roller. Moreover, the contact surface 43a of the first shaping roller 40a and in contact with the glass ribbon overlaps or extends beyond the contact surface 43b of the second shaping roller 40b in contact with the glass ribbon, thereby forming an ^WS" shaped curve in the region of the glass ribbon along the ribbon centerline. Put another way, and referring to FIG. 4A, assuming the ribbon is represented by a vertical plane having first and second major surfaces 42 and 44, a first shaping roller of the shaping roller pair positioned proximate the first surface of the plane is translated in a direction toward the second, opposite surface of the plane as indicated by arrow 50, while the other shaping roller of the pair positioned proximate the second major surface of the plane is translated in a direction toward the first major surface indicated by arrow 52. Thus, the contact surfaces of the rollers pass each other going in opposite directions and produce an overlap δ (see FIG. 9). Since the ribbon of molten glass material is viscous (or viscoelastic), it gives in response to the opposing forces applied by the shaping roller pair, and the horizontal displacement of the ribbon caused by the oppositely directed forces cause the ribbon in the vicinity of these forces to assume an "S" shape. Preferably, the viscosity of the ribbon contacted by the shaping rollers is in the range from about lxlO⁵ Poise to about lxlO⁷ Poise. Of course, the lateral (width-wise) placement of the offset shaping rollers proximate the centerline of the ribbon depicted in FIGS. 4A and 4B is only an example, and placement of offset shaping rollers could be at other locations across a width of the ribbon, depending on where a curvature is desired. However, placement of a first pair of offset shaping rollers proximate the centerline allows later separation of the ribbon at the centerline producing two individual sections of glass having generally the same width. Note also that if the "S" shaped portion of the ribbon is separated at an inflection point of the curve, the two separate glass sections have an edge curve that is nearly identical. In the example of FIGS. 4A and 4B, ribbon centerline 48 coincides with the inflection point of the central "S" curve.

[0034] According to FIG. 4A, two additional offset shaping roller pairs are engaged proximate (just inward of) the ribbon edges, thereby producing an "S" shaped curved portion proximate each outer edge of the ribbon. Again, separating the ribbon length-wise through the inflection points (at dashed lines 54, 56) of the respective edge "S" curves produces curved portions at the edges of the ribbon similar to the curve produced proximate the centerline. Separating the ribbon laterally (across a width of the ribbon) as the ribbon moves vertically downward from the forming body produces separate glass sheets 58. That is, the three offset shaping roller pairs of FIG. 4A, engaged at approximately the centerline of the ribbon, and proximate the edges of the ribbon, produce a minimum of three "S" shaped curves in the ribbon. When the ribbon is separated across a width of the ribbon to produce separate sheets of glass, and each separate sheet of glass is separated along the inflection point (or line) of each "S" shaped curve, the result is two sheets (i.e. sub-sheets) of glass including two curved portions at edges of the sheets, both curved in the same direction for each individual sub-sheet. It should be apparent based on the disclosure herein that additional offset shaping roller pairs could be employed to yield additional glass sheets having curved edges (albeit of smaller size assuming the same size ribbon).

[0035] It is notable that first surface 42 to the left of centerline 48 as viewed in FIG. 4A remains pristine during the shaping operation. That is, the edge shape of the left portion of the ribbon includes concave (downward pointing edges as viewed in the figure), and thus surface 42 between lines 48 and 54 will form the front (viewer side) surface of the resultant glass sheet. This surface is unmarked by the "lower" rollers, and the portion of the sheet contacted by the "upper" rollers will be separated away. Here, upper and lower are arbitrary but opposite directions, and should be viewed, in the context of the present description, according to the orientation of the figure, wherein upper corresponds to a direction toward the top of the figure, and lower corresponds to a direction to ward the bottom of the figure. Similarly, the right side portion of surface 44 between lines 48 and 56 remains pristine, being untouched by the "lower" rollers. In both sections of the ribbon, the viewer side of the glass portions, after separation into sub-sheets, remain untouched during the shaping process and are contacted by the shaping rollers only on the device or back side (opposite the viewer side).

[0036] FIG. 5 is a perspective view of a portion of the ribbon descending from the forming body of FIG. 2, wherein shaping rollers are disposed between pairs of edge rollers positioned upstream and downstream of the shaping rollers relative to the direction of travel 32 of the ribbon. Also shown is a score line running laterally across a width of the ribbon (generally perpendicular to the direction of travel 32 of the ribbon), and indicated by the dotted line 57.

[0037] Separation of the ribbon, either longitudinally, lines 48, 54 and 56 for example, or across a width of the ribbon (score line 57), can be accomplished via contact scribing (e.g. carbide wheel or diamond), or by scoring and/or cutting with a laser. Separation of the ribbon along score line 57 (such as by applying a bending force to the ribbon), forms glass sheet 58. [0038] FIG. 6 is a cross sectional view across a width of the glass sheet 58 showing additional locations where the glass sheet can be separated into individual sub-sheets. In accordance with FIG. 6, glass sheet 58 (or alternatively, ribbon 34) can be scored length-wise along the curvature formed by the shaping roller pairs (see FIG. 5).

[0039] FIG. 7 shows a cross sectional view of the two sub-sheets obtained by cutting or separating the ribbon lengthwise along the indicated score lines. Both sub-sheets 58a and 58b have a cross sectional shape that is generally flat, but that includes curved edge portions 16. It should be apparent that the edge portions could be other shapes depending on the shape of the shaping rollers themselves. For example, the edge portions could be substantially flat, but angled relative to the flat interior portion of the glass sheet. Generally, the edge portions may be viewed as not within the plane of the interior portion of the resultant glass sheet (interior to the edge portions).

[0040] In another embodiment, shown in FIGS. 8 - 10, each shaping roller 40 in an offset shaping roller pair 40 includes a flange 60, wherein the flange on one shaping roller cooperates with the flange on the other shaping roller of the pair to pinch the ribbon, wherein the close proximity of the two flanges thins the glass between the flanges (e.g. along the inflection line). This thinned portion 62 of the ribbon (best seen in FIG. 9) serves as a score line, facilitating later separation of the glass sheet 58 into separate sub-sheets along the vertical score lines. In the example embodiment illustrated in FIG. 10 (shown without glass ribbon 34), each shaping roller of shaping roller pair 41 has the same length L (not including flange 60), and a distance D between the midpoint (LV2) of each shaping roller of the shaping roller pair is greater than the length L of either of the shaping rollers of the shaping roller pair (assuming the length L of each shaping roller is equal). In some embodiments, a distance d between the nearest ends of the shaping rollers of a shaping roller pair, that is, the ends of the rollers closest to each other, is less than a length L of either of the shaping rollers. [0041] In some embodiments, additional shaping roller pairs may be included at a vertical position different that the vertical position of a first pair of shaping rollers. Additional shaping rollers may be desirable if a particular shape imparted by the first shaping rollers requires modification. For example, in the same manner a progression of dies can be used to progressively shape an extruded object, a progression of shaping rollers can be used to achieve a given final shape in the glass that might be difficult to obtain with a single shaping roller pair. The apparatus according to FIG. 5, for example, includes multiple shaping roller pairs at different vertical positions. In this instance, there are shown three shaping roller pairs at a first vertical position, and three shaping roller pairs at a different vertical position. For example, the shaping rollers may have curved edges as shown in FIGS. 4A - B, and 8 - 9, but progressive shaping rollers (in the direction of glass travel) may include a different radius of curvature to each shaping roller edge, such as progressively smaller. Similarly, the horizontal placement of the shaping roller pairs, either at one vertical location or multiple vertical locations relative to the forming body root 28, can be varied such that the shaping rollers do not create symmetrically spaced shapes in the glass ribbon. That is, the horizontal distance separating shaping rollers of any set of shaping roller pairs need not be equal, but may be varied to meet future product needs. Moreover, the distance between individual shaping rollers (e.g. distance "D") of a shaping roller pair may be varied to obtain varied shapes. Positioning of the shaping rollers, at least within a given horizontal plane, can be easily automated by including positioning servos, thereby allowing for position adjustment. One or more computers may be included and linked to the positioning servos so that an automated feedback system may be employed to position the shaping rollers.

[0042] It should be emphasized that the above-described embodiments of the present invention, particularly any "preferred" embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiments of the invention without departing substantially from the spirit and principles of the invention. For example, although the preceding description has been directed to the shaping of glass sheets, the apparatus and methods described herein can be applied to other materials that exhibit a viscous, viscoelastic state, or are otherwise deformable, such as glass-ceramic materials, plastics, or in some instances even metals. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.

Claims

1. An apparatus (20) for shaping a continuously moving ribbon of molten glass (34) comprising:

a forming body (22) for producing a moving ribbon of molten glass (34); and

a pair (41) of offset shaping rollers (40) disposed downstream of the forming body (22) relative to a direction of travel (32) of the ribbon of molten glass (34), the pair (41) of offset shaping rollers (40) comprising a first offset shaping roller (40a) positioned adjacent to and in contact with a first side (42) of the moving ribbon of molten glass (34) and a second offset shaping roller (40b) positioned adjacent to and in contact with a second side (44) of the moving ribbon of molten glass (34), wherein the first offset shaping roller (40a) and the second offset shaping roller (40b) are laterally offset from each other, and a contact surface (43a) of the first offset shaping roller (40a) where the first offset shaping roller (40a) contacts the moving ribbon of molten glass (34) extends past a contact surface (43b) of the second offset shaping roller (43b) where the second offset shaping roller (40b) contacts the moving ribbon of molten glass (34), thereby producing curvature in the moving ribbon of molten glass (34).

2. The apparatus according to claim 1, further comprising a plurality of offset shaping roller pairs (41) in contact with the moving ribbon of molten glass (34).

3. The apparatus according to claim 1 or 2, wherein the plurality of offset shaping roller pairs (41) are at different vertical positions relative to a root (28) of the forming body (22).

4. The apparatus according to claim 1 or 2, wherein the plurality of offset shaping roller pairs (41) lie along a single horizontal plane.

5. The apparatus according to any one of claims 1 - 4, wherein a distance D between a midpoint of the first shaping roller (40a) and a midpoint of the second shaping roller (40b) is greater than a length L of either the first (40a) or the second (40b) shaping roller.

6. The apparatus according to any one of claims 1 - 5, wherein a distance d between nearest ends of the first (40a) and second (40b) shaping rollers is less than a length L of either the first (40a) or second (40b) shaping roller.

7. A method of shaping a moving ribbon of material (34) comprising:

forming a moving ribbon of material (34) having first (42) and second (44) major surfaces, the moving ribbon of material (34) comprising a viscoelastic portion and an elastic portion;

contacting the first major surface (42) of the moving ribbon of material (34) in the viscoelastic portion with a first shaping roller (40a); and

contacting the second major surface (44) of the moving ribbon of material (34) in the viscoelastic portion with a second shaping roller (40b) laterally offset from the first shaping roller (40a), the first and second shaping rollers (40a, 40b) forming an offset shaping roller pair (41), and wherein contact with the ribbon of material (34) by the offset shaping roller pair (41) produces a first curvature in the ribbon (34).

8. The method according to claim 7, wherein a plurality of curvatures are induced by a plurality of offset shaping roller pairs (41) contacting the moving ribbon of material (34).

9. The method according to claim 7 or 8, wherein the moving ribbon of material (34) comprises a glass material.

10. The method according to any one of claims 7 - 9, wherein each of the first (40a) and second (40b) shaping rollers comprises a flange (60), and a score line (62) is formed in the moving ribbon of material (34) by the flanges (60) of the first and second shaping rollers (40a, 40b).

11. The method according to any one of claims 7 - 10, wherein a viscosity of the moving ribbon of material (34) contacted by the first (40a) and second (40b) shaping rollers is in the range between about lxlO⁵ and lxlO⁷ Poise.

12. The method according to any one of claims 7 - 11, further comprising separating the moving ribbon of material (34) in a direction perpendicular to a direction of flow (32) of the moving ribbon of material (34) to form a sheet of material (58) having the first curvature.

13. The method according to claim 12, further comprising separating the sheet of material (58) along the first curvature to produce sub-sheets (58a, 58b) of material having a curved edge (16).

14. The method according to any one of claims 7 - 13, wherein a distance d between nearest ends of the first (40a) and second (40b) shaping rollers is less than a length L of either the first (40a) or second (40b) shaping roller.

15. The method according to any one of claims 7 - 14, wherein a distance D between a midpoint of the first shaping roller (40a) and a midpoint of the second shaping roller (40b) is greater than a length L of either the first (40a) or the second (40b) shaping roller.