TW201446665A - Method of separating a glass sheet from a continuous glass ribbon - Google Patents

Abstract

A method of separating a glass sheet from a continuous glass ribbon wherein counter rotating wheels comprise teeth such that a tooth on one wheel aligns with the tooth on the other wheel as the wheels rotate. The aligned teeth contact bead portions of the glass ribbon and pinch the ribbon between the aligned teeth to form indents. The pinching reduces a thickness of the bead, thereby weakening the bead and facilitating crack propagation across the bead after the bead cools to an elastic solid.

Description

Method for separating glass sheets from continuous glass ribbon [Reciprocal Reference Related Applications]

The present application is based on the benefit of the U.S. Patent Provisional Application Serial No. 61/824,169, filed on May 16, 2013, which is hereby incorporated herein in In this article.

The present invention generally relates to a method of separating a glass sheet from a continuous glass ribbon, and more particularly to a method for reducing the energy required to extend a crack across a full width of a glass ribbon by weakening the bead region of the glass ribbon. .

Typically, the glass sheets formed by the melt process are separated from the glass ribbon by mechanical scoring and subsequent bend separation in a fusion draw machine (FDM). The glass ribbon usually has a shape, or in other words, because of the residual stress and thermal stress inside the glass, the glass ribbon generally exhibits an arcuate shape beyond the plane in both the horizontal and vertical directions. The shape of the glass ribbon is also related to the presence of thickened portions (beads) placed along the lateral edges of the glass ribbon. The thickened portions are much thicker than the central portion of the glass ribbon and produce significant thermal gradients and stress gradients. Through the glass.

When the glass ribbon is made thinner, the ratio of the thickness of the beads to the thickness of the central portion of the glass ribbon becomes larger. In addition, as the size of the glass sheet is increased and/or the thickness of the glass is reduced, the rigidity of the glass ribbon is reduced, which typically results in a larger arcuate shape of the glass sheet cut from the glass ribbon. The combined effect of the larger bead-to-center thickness ratio and the smaller glass ribbon stiffness can present significant challenges in controlling glass ribbon movement and maintaining glass ribbon stability during the scoring and separation process. Due to the reduced pull stability, both the forming process window and the process window at the bottom of the drawing area become narrow and produce high process upset frequencies. The movement of the glass ribbon caused by the scoring and separating process not only affects the glass sheet cutting process itself, but also extends to the glass forming process and ultimately affects the final glass quality, so the narrow process window becomes a serious problem.

Another challenge in the melt forming process is the formation of hollow beads (air gaps in the molten wire in the bead) due to aging of certain parts of the shaped body and difficulty in fluid and thermal control in the bead forming zone. . Once the hollow bead is formed, the scoring and separation process window will become even narrower and uncontrollable cracks may occur during the separation of the glass sheets.

Conventional mechanical cutting involves: scribing the glass ribbon between the beads and then separating them by, for example, mechanical bending. Because the thickness at the bead suddenly increases, the scoring across the bead is very difficult and unstable. The main disadvantage of today's cutting processes is that the thickened and unmarkable beads have significant resistance to the bending separation process through structural rigidity and minimal defect surfaces. As a result, crack propagation at the beads can result in dog ears or vertical cracks due to failure of the separation crack to propagate through the beads. The target glass thickness becomes thinner, making this situation become Worse.

Therefore, it is desirable to introduce a small bend angle or lower energy to separate the glass sheets, as this allows for the introduction of smaller glass sheet movements with less impact on the pull stability.

Due to the ratio of the thickness of the beads to the thickness of the glass ribbon and the shape of the glass sheet, the separation of the glass at the bottom of the drawing requires significantly more energy to separate the glass through the beads. In some embodiments, the glass ribbon separation scoring occurs only in the quality region of the glass ribbon, with the high quality regions of the glass ribbon being laterally interposed between the beads. This becomes more common on thinner glass ribbons. Since the mechanical scoring wheel skips the rough bead surface, it is impossible to achieve a "good" vent crack in the bead. Since cracks cannot be introduced on the surface of the beads, additional energy is required to bend the glass for separation, resulting in more interference with the melt forming process described above. If a hollow bead is present, crack out will be more likely to occur during the separation.

The present disclosure describes a method for reducing energy and performing a reliable separation process in the presence of a bead of a thickened glass ribbon by the following steps: inside the melt drawing machine, and still having viscosity in the bead At a height (e.g., viscoelastic), a symmetrical indentation is introduced mechanically on both sides of the bead. The shrinking beads reduce the local bending rigidity and reduce the energy required for sheet separation at the bottom of the drawing (where the glass ribbon is in the elastic solid state), thereby promoting crack propagation through stress concentration, reducing glass sheet movement, and increasing Forming stability.

In addition, the indented beads can be used as a scoring wheel for guidance along the cross-draw direction and/or because a much lower bend is required Folding energy as a guide to the scribe line crack extension into the bead area. Therefore, it is possible to reduce the movement of the glass ribbon and increase the stability of the drawing because of the low bending (low energy) separation, and to significantly reduce or eliminate the defects of the separation of the beads, such as the dog ear (expansion of the angle transition) Or upward vertical expansion of cracks generated during separation.

A series of indentations in the bead region of the glass sheet can weaken the beads and thus reduce the bending angle and reduce the energy required for subsequent glass sheet separation. The indentation can be initiated mechanically at a predetermined frequency in the forming region such that the indentation is aligned with the subsequent score line for each glass sheet glass cycle. The indentation is symmetrical along the lateral edges of the glass ribbon. Ideally, the indented glass thickness will have the same glass thickness as the quality region glass thickness.

Thus, in one embodiment, a method of separating a glass sheet from a continuous glass ribbon is disclosed, the method comprising the steps of: forming a continuous glass ribbon in a downward draw process; in a viscous state of the glass ribbon Simultaneously engaging the glass ribbon with a pair of opposing rollers, each of the pair of opposing rollers including a tooth portion projecting from the roller, wherein the opposing rollers are synchronized such that one of the pair of rollers is rotated during rotation of the opposite roller The teeth are aligned with respect to the teeth of the roller to create a relative indentation in both sides of the edge of the glass ribbon; after the glass ribbon is cooled to the elastic state, the glass ribbon is scored to form a score line, so that the score line Aligning the relative indentations; and applying a tensile stress across the score line to separate the glass sheets from the glass ribbon by bending. The score line can be formed by engaging the glass ribbon along the width of the glass ribbon to score the blade. Each of the pair of rollers may include a single tooth, or a plurality of teeth. In certain embodiments, the thickness of the glass ribbon between the opposing indentations is substantially the same as in the central portion of the glass ribbon. Glass strip thickness.

The additional features and advantages of the present invention are set forth in the Detailed Description of the Drawings. The present invention (including the following detailed description, claims, and claims)

It is to be understood that the foregoing general description of the embodiments of the invention, The drawings are included to provide a further understanding of the present disclosure, and are incorporated in the specification and constitute a part of the specification. The drawings illustrate various embodiments of the disclosed subject matter, and together with the description of the embodiments.

10‧‧‧Melt glass drawing machine

12‧‧‧fused glass

14‧‧‧Formed body

16‧‧‧ Entrance

18‧‧‧

20‧‧‧Formed surface

22‧‧‧ Root

24‧‧‧glass ribbon

26‧‧‧ Pulling roller

28‧‧‧ beads

30‧‧‧Central Part

32‧‧‧ Scotch

33‧‧‧ Pulling direction

34‧‧‧Roller

36‧‧‧ teeth

38‧‧‧ dotted line

40‧‧‧ contraction

42‧‧‧ radial axis

44‧‧‧Rotary axis

46‧‧‧ scoring device

48‧‧‧ Robot

49‧‧‧ longitudinal centerline

1 is a front elevational view of an exemplary apparatus for drawing a continuous glass ribbon in accordance with the present disclosure; and FIG. 2 is a cross-sectional view of the exemplary apparatus for drawing a continuous glass ribbon of FIG. 1 (from one end of the example device) Figure 3 is a cross-sectional view of the glass ribbon showing the bead; Figure 4 is a cross-sectional view of the bead portion of the glass ribbon pinched by the counter-rotating roller, with each reverse rotation The roller includes a tooth portion, and the tooth portion forms a retraction portion in the glass bead body; FIGS. 5A to 5C illustrate the timing of the reverse rotation roller position of FIG. 4, and the tooth portion of the reverse rotation roller moves to be aligned, To pinch the glass with beads; Figure 6 is a front elevational view of a portion of the glass ribbon, wherein the glass ribbon is being lowered from the shaped body, and wherein the time during which the indentation is formed is arranged such that the arrangement of the indentations coincides with the arrangement of the score lines; Figure 7 A roller having more than one tooth is illustrated; Figure 8 depicts a model constructed by a function of the vertical stress in the ribbon as a function of the distance from the longitudinal centerline of the ribbon under a number of specified bending conditions.

Now, please refer to the various embodiments of the disclosure, and some examples of the embodiments are illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used throughout the drawings to refer to the

Figs. 1 and 2 depict an exemplary glass drawing machine, and in particular, a fusion glass drawing machine (FDM) 10 for forming a glass sheet. According to Figures 1 and 2, the molten glass 12 is supplied to the shaped body 14 through the inlet 16. The shaped body 14 includes a trough body 18 that extends longitudinally along the upper surface of the shaped body 14. The molten glass 12 overflows the trough 18 and flows through the tapered forming surface 20 in a separate flow of molten glass. Next, individual molten glass streams are joined along the line where the tapered forming surfaces meet, and the roots 22 are joined (melted) to form a continuous glass ribbon 24. The pull roller 26 can pull the glass ribbon 24 from the root portion 22.

Figure 3 depicts a cross-sectional view of an exemplary glass ribbon 24. The pulling force and surface tension tend to create a thickened portion along the outer edge of the glass ribbon, commonly referred to as a bead 28. The central portion 30 of the glass ribbon 24 extends between the beads and is commonly referred to as the quality region because the central portion is moving A commercially available glass ribbon portion after the bead body. However, in some glass sheet manufacturing operations, the glass sheets are separated by a glass ribbon prior to removal of the beads. Therefore, the beads pose unique challenges to the separation process.

Typically, a score 32 is formed in the glass ribbon in the same direction as the width (see Figure 1). The score can be formed mechanically, wherein the score roller or other scoring element contacts the glass ribbon and traverses across the width of the glass ribbon. In other embodiments, the laser can be used to form a score. As used herein, a score represents a line that causes mechanical damage to the glass ribbon, for example, the score represents a line of mechanical damage to the glass ribbon, such as an open crack that extends at least partially into the thickness of the glass ribbon. Therefore, the score can also be called a score line. In many instances, the thickened beads prevent the formed score from traversing the entire width of the glass ribbon. Therefore, the score usually does not extend into the bead. Once the score is formed, such as across the central portion 30, tensile stress across the score (i.e., orthogonal to the score line) can generally be created by bending the glass ribbon. However, thicker, ungrained beads require a larger energy input glass to cause the crack to extend through the beads of the glass ribbon. Once the crack propagates through the bead, excess energy is released and can form a disturbance that travels through the glass ribbon and interferes with the glass ribbon in the setting zone. The shaped area is where the glass ribbon transforms from a viscous liquid to an elastic solid. Such perturbations can create stresses that freeze into the glass ribbon and can, for example, affect the shape of the glass sheet separated from the glass ribbon. Therefore, increasing the ease with which cracks can expand through the beads reduces the residual stress in the subsequent glass sheets separated from the glass ribbon.

According to embodiments disclosed herein, a symmetrical retraction is mechanically introduced into the edge portion of the glass ribbon (eg, the bead region) within the melt puller to reduce the need for sheet separation at the bottom of the draw. Energy, and then through stress Concentrate on promoting crack propagation, reducing glass sheet movement, and increasing form stability. Therefore, a series of indentations are formed in the edge portion of the glass ribbon to weaken the beads, thereby reducing the bending angle and reducing the energy required to separate the glass sheets from the glass ribbon.

Figure 4 depicts a portion of one longitudinal edge of the glass ribbon 24 that is lowered in the pull direction 33. The positions of the counter-rotating rollers 34 are arranged in an opposing relationship at the longitudinal edges of the glass ribbon such that one roller is positioned adjacent each side of the edge, wherein each roller 34 includes a projection, i.e., a tooth portion 36. The roller can be coupled to a driving driving force (such as an electric motor or other mechanical driving device) through a suitable connection (not shown) and synchronized so that when the roller 34 rotates, the teeth 36 on each roller can be aligned and close. The opposing teeth on the roller are indicated by the dashed line 38 in Figure 4. Thus, as the rollers rotate such that the teeth on each roller contact the moving glass ribbon, a relative indentation 40 can be formed at the bead on the surface of the moving glass ribbon. In other words, the aligned teeth pinch the glass ribbon at the beads, thereby reducing the thickness of the beads at which the teeth contact the glass.

The indentation is symmetrically formed at the opposite edges of the moving glass ribbon, meaning that the indentations formed along one edge of the moving glass ribbon are aligned in the horizontal direction on the opposite edges of the moving glass ribbon. Retraction.

Figures 5A through 5C illustrate the position of a series of rollers 34 as the roller 34 rotates in the opposite direction. For each roller, the radial axis 42 of the respective tooth on each roller is depicted such that travel through the pattern can show how the radial axis 42 of each roller rotates as the corresponding roller rotates, causing the tooth to rotate Closer to alignment. Each radial shaft 42 bisects or substantially bisects the teeth on the roller and passes through the axis of rotation 44 of the roller.

In addition, the diameter of the rollers can be selected such that during each of the sheet separation cycles, the score lines formed by the associated scoring equipment in the moving glass ribbon coincide with the relative indentations formed in the moving glass ribbon. It should be noted that the spatial frequency at the indentation does not need to coincide with the spatial frequency of the scribe line formed by the scoring equipment. As used herein, the spatial frequency in the view of the indentation refers to the number of indentations per unit length (on one side of the edge portion of the glass ribbon), for example, 2 indentations per meter. The spatial frequency of the score line refers to the presence of the score line as a function of the distance between the score lines, for example, a score line produced every 4 meters along the length of the glass ribbon. It should be understood that since the separation may be performed at the first scribe line before the second scribe line is created, the two scribe lines may not be formed (present) in the glass ribbon at the same time. The spatial frequency at the relative indentation may be greater than the spatial frequency of the score line, but the spatial frequency relative to the indentation causes the relative indentation to be formed at each score line. Alternatively, this can be considered as the scribe line does not need to be formed at each indentation while the glass sheet is separated from the glass ribbon at each score line. In the case of a glass sheet having a length L cut from the glass ribbon (i.e., a score line is created on the moving glass ribbon along the glass ribbon increments L), assuming that each roller has a single tooth portion, the roller 34 should be selected. The diameter D is such that L is m times pi (m is a positive integer) multiplied by the diameter D. In other words, the diameter D of the roller 34 should be selected such that L/mπ = D. If m is greater than 1, then more indentations will be formed than the score line. This assumption only marks the glass ribbon where the glass piece is to be separated.

Figure 6 illustrates a portion of the glass ribbon that has been lowered from the shaped body 14 (not shown). As the ribbon is lowered, the indentation 40 can be periodically formed at the bead along the length of the ribbon. The scoring device 46 travels on the glass ribbon At least a portion of the width, a score (scribe line 32) is formed in the glass ribbon between the beads 28. The scoring time is mechanically or electronically arranged such that each score line corresponds to a position of the indentation 40. Below the scoring device 46, the robot 48 engages the free end of the glass ribbon and applies a bend to the glass ribbon. The bending can form a tensile stress across the scribe line above the robot to separate the glass sheets from the glass ribbon. As noted earlier, the point in time between the pinch by the roller 34 and the scribe by the scoring device 46 allows the scribe to be scored at a position coincident with the pinch, causing the score line 32 to be aligned The indentation is 40.

As will be apparent from the foregoing description, each of the rollers 23 can have more than one tooth. For example, Figure 7 illustrates a roller 34 having two teeth positioned in a 180 degree separation. In this example, the foregoing formula is modified by counting the number of teeth on each of the rollers 34.

A Finite Element Analysis (FEA) model can be developed to study the bead notch concept described above. Figure 8 shows on a Corning Eagle XG ^TM made of glass and having a retracted examples of glass beads with (where the ribbon is bent in the retracted impose about 6 degrees (curve 50) and 12 degrees (curve 52)), And in the same glass ribbon with non-retracted bead at 6 degree bend (curve 54) and 12 degree bend (curve 56), stress in the vertical direction (in pounds per square inch) The result of the model construction as a function of the position across the width of the glass ribbon (measured in millimeters (mm), measured from the longitudinal centerline 49). It is assumed that the example glass ribbon has a thickness of 0.3 mm in the central portion and a maximum bead thickness of about 0.65 mm. In the case of intrinsicized beads, higher stresses can be created in the bead region, indicating that the beads are more susceptible to breakage or can separate the beads at lower energies.

For those of ordinary skill in the art to which the invention pertains, It is apparent that various modifications and variations can be made to the embodiments disclosed herein without departing from the spirit and scope of the disclosure. Therefore, the present disclosure is intended to cover such modifications and variations as the scope of the modifications and the scope of the invention.

24‧‧‧glass ribbon

33‧‧‧ Pulling direction

34‧‧‧Roller

36‧‧‧ teeth

38‧‧‧ dotted line

40‧‧‧ contraction

44‧‧‧Rotary axis

Claims (9)

A method for separating a glass sheet from a continuous glass ribbon, comprising the steps of: forming a continuous glass ribbon in a downward drawing process, the glass ribbon comprising a viscous portion; and a first edge portion of the viscous portion Engaging a first pair of opposing rollers, each of the first pair of opposing rollers including a projection extending from the roller, wherein the first pair of opposing rollers are synchronized such that during the rotation of the rollers, the first pair The projection of one of the rollers is aligned with the projection of the opposing roller to create a relative indentation in the first edge portion of the glass ribbon; after the ribbon is cooled to an elastic state, Marking the glass ribbon to form a score line across a width of one of the glass ribbons, the score line being aligned with the relative indentations in the first edge portion; and applying a tensile stress across the score a wire to separate a piece of glass from the glass ribbon. The method of claim 1, wherein the score line is formed by joining the glass ribbon to a scoring element. The method of claim 1, wherein each of the pair of opposing rollers comprises only a single projection. The method of claim 1, wherein each of the pair of opposing rollers comprises a plurality of projections. The method of claim 1 wherein the thickness of the glass ribbon between the relative indentations is substantially the same as the thickness of the glass ribbon in a central portion of the glass ribbon. The method of claim 1, wherein the glass ribbon comprises a second edge portion located within the viscous portion and relative to the first edge portion, the method further comprising the step of: engaging the second edge portion with the second For each of the opposing rollers, each of the second pair of opposing rollers includes a projection extending from the roller, wherein the second pair of opposing rollers are synchronized such that during rotation of the rollers, the second pair of rollers The projection of a roller is aligned with the projection of the opposing roller of the second pair of rollers to create a relative indentation in the second edge portion of the glass ribbon. The method of claim 6, wherein the scribe line is aligned with the relative indentations of the first edge portion and the relative indentations of the second edge portion. The method of claim 7, wherein the score line does not extend to the relative indentations of the first edge portion and the relative indentations of the second edge portion. The method of claim 6 wherein the thickness of the glass ribbon between the opposing indentations of the second edge portion is substantially the same as the thickness of the glass ribbon in a central portion of the glass ribbon. .