Patent Application
20140144965
The present disclosure relates generally to methods of manipulating a brittle material sheet compound shape, and more particularly, to methods for manipulating a brittle material sheet compound shape during a severing operation.
Producing flat product glass for displays, such as LCDs, involves many challenges. A significant aspect in this process is an ability to produce a very consistent shape in large product glass plates. Typical large product glass sheets can be, for example up to 3.3 square meters.
Corning Incorporated has developed a process known as the fusion process (e.g., downdraw process) to form high quality thin glass sheets that can be used in a variety of devices like flat panel displays. The fusion process is a preferred technique for producing glass sheets used in flat panel displays because the product sheets have surfaces with superior flatness and smoothness when compared to glass sheets produced by other methods. The general fusion process is described in, for example, U.S. Pat. Nos. 3,338,696 and 3,682,609.
One embodiment of the fusion process involves using a fusion draw machine (FDM) to form a glass sheet and then draw the glass sheet between two rolls to stretch the glass sheet to a desired thickness. A traveling anvil machine (TAM) is used to cut the glass sheet into smaller glass sheets requested by customers.
Residual product stress and shape can be caused in the glass sheet by a number of factors, such as the process temperature profile, the glass ribbon motion caused by the TAM, and glass cutting. There are a number problems that can occur in the manufacture of liquid crystal displays whenever the residual stress of glass sheet is large or its shape is not stable.
The following summary provides a basic understanding of some example aspects described in the detailed description.
In one example aspect, a method to manipulate a glass sheet compound shape during a severing operation is provided. The method comprises providing the glass sheet having a pair of opposed edge portions and a central portion laterally spanning between the opposed edge portions. The central portion has a first side facing a first direction and a second side facing a second direction opposite the first direction. The method further comprises the steps of positioning a scoring device against the first side of the central portion of the glass sheet, and temporarily bending an extended portion of the glass sheet located between the scoring device and a selected one of the edge portions from a first orientation to a severing orientation by applying a force to the extended portion of the glass sheet. The method further comprises forming a score line along the first side of the central portion of the glass sheet while the force is being applied to the extended portion of the glass sheet, and breaking away the selected one of the edge portions from the glass sheet along the score line
In another example aspect, a method to manipulate a glass sheet compound shape during a severing operation is provided. The method comprises providing the glass sheet having a pair of opposed edge portions and a central portion laterally spanning between the opposed edge portions. The central portion has a first side facing a first direction and a second side facing a second direction opposite the first direction. The method can further comprise positioning a scoring device against the first side of the central portion of the glass sheet, and applying a force to an extended portion of the glass sheet located between the scoring device and a selected one of the edge portions sufficient to achieve a predetermined surface stress along the first side of the glass sheet adjacent the scoring device. The method can further comprise forming a score line along the first side of the central portion of the glass sheet while the force is being applied to the extended portion of the glass sheet, and breaking away the selected one of the edge portions from the glass sheet along the score line.
In yet another example aspect, a method to manipulate a glass sheet compound shape during a severing operation is provided. The method comprises providing the glass sheet with a pair of opposed edge portions and a central portion laterally spanning between the opposed edge portions. The central portion has a first side facing a first direction and a second side facing a second direction opposite the first direction. The method can further comprise positioning a scoring device against the first side of the central portion of the glass sheet, and sensing a first orientation of an extended portion of the glass sheet located between the scoring device and a selected one of the edge portions. The method can further comprise determining an amount of a force to be applied to the extended portion of the glass sheet sufficient to achieve a predetermined severing orientation, based upon a comparison of the sensed first orientation and the predetermined severing orientation. The method can further comprise applying the force to the extended portion of the glass sheet to temporarily bend the extended portion of the glass sheet to achieve the predetermined severing orientation, and forming a score line along the first side of the central portion of the glass sheet while the force is being applied to the extended portion of the glass sheet, and breaking away the selected one of the edge portions from the glass sheet along the score line.
These and other features, aspects and advantages of the present disclosure are better understood when the detailed description is read with reference to the accompanying drawings:
Methods will now be described more fully with reference to the accompanying drawings in which example embodiments of the disclosure are shown. Whenever possible, the same reference numerals are used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
Recent trends in the LCD glass manufacture have been to progressively wider size and more recently a move to thinner glass sheets, such as about 0.3 mm (i.e., 300 microns) thickness or less. Both of these trends (wider and thinner) significantly reduce the inherent stiffness of the glass sheet and make the production process more sensitive at the Bottom of Draw (BOD). This sensitivity is primarily driven by the non-planarity of the glass sheet. This shape is primarily driven by the thin center portion of the glass sheet cooling much more rapidly than the thicker bead edge regions. Consequently, a thermal mismatch results in a vertical and/or horizontal bow being induced into the glass sheet as a result of internal stresses that cause the glass sheet to distort into a non-symmetric compound shape (e.g., a “potato chip” type shape). This can create many problems in sheet glass processing such as breakage and transport instability.
One aspect discussed herein is the management of this compound shape during the glass cutting (e.g., severing) process. Another aspect discussed herein relates to a method of manipulating the sheet shape on thin glass such that the resulting surface stress in the glass is advantageous to the score and break separation process. Manipulation of the glass sheet towards a predetermined shape, in conjunction with the scoring wheel and breaking mechanism, work to remove the outer bead portion of the sheet within a machine designed to do the same, referred to as a Vertical Bead Scoring machine (VBS). A thin glass sheet, such as 0.3 mm thickness, develops the described compound shape as the sheet is conveyed from the FDM (Fusion Draw Machine) to the VBS prior to sheet edge bead removal.
Generally, one goal when scoring thin glass sheet for edge bead removal is to produce a uniform median vent simultaneously on both sides of the VBS (e.g., on both of the inlet and compression sides). A general rule is for the score vent depth to be normally about 10% of the glass thickness. If a sheet is flat and the surface stress is controlled, the median crack depth can be relatively easily controlled by applying a stable scoring force to the score wheel. However, when scoring on thin glass with unpredictable shape, the vent depth cannot be controlled using standard methods due to the glass shape inducing either or both of compressive and tensile stresses on the glass surface during a single scoring event. This change in stress results in a highly variable median crack, normally resulting in sheet breakage.
Each of the opposed edge portions 104, 106 terminates at an enlarged bead area that is beneficial to remove (e.g., sever) from the glass sheet 102. Although the following discussion focuses on one selected edge portion 104, it is contemplated that the structure and methodology can be similarly applied to various other portions of the glass sheet 102, such as the other edge portion 106. The severing process can incorporate a wide range of techniques. For example, the edge portion 104 can be severed from the central portion 108 by way of a glass cutting device, such as a scoring device 114. The scoring device 114 can be positioned against the first side 110 of the central portion 108 of the glass sheet 102.
For example, the scoring device 114 can be, for example, a scribe or other mechanical device that can create an initial defect (e.g., crack, scratch, chip, or other defect) with the point of the scribe to create a controlled surface defect at the site where the glass sheet 102 is to be severed. The scoring device 114 can include a tip although an edge blade or other scribe technique may be used in further examples. Still further, the initial defect or other surface imperfection may be formed by etching, laser impact, or other techniques. The initial defect may be created at the edge of the glass sheet 102 or at an inboard location on the surface of the glass sheet 102. An active or passive nosing device 115 can be used on the other side of the glass sheet 102 opposite to the scoring device 114 to inhibit glass sheet motion transferred from the scoring or breaking process. A side push break assembly 117 is located near the scoring device 114 to facilitate the glass breaking process to remove the edge portion 104. The side break assembly 117 is located between the scoring device 114 and the edge portion 104, and can be positioned on either the first or second side 110, 112 of the glass sheet 102.
The central portion 108 of the glass sheet 102 may be clamped at a distance away from the edge 104 and generally near the scoring device 114 to facilitate the scoring process by stabilizing the glass sheet 102. In one example, the central portion 108 may be clamped by a tower clamp 120 located inboard of the scoring device 114. An extended portion 116 of the glass sheet 102 is then defined between the scoring device 114 and the edge portion 104. The extended portion 116 acts as a cantilever due to the tower clamp 120. Thus, because of the tower clamp 120, the extended portion 116 of the glass sheet 102 may still be vertically movable relative to the scoring device 114, which can cause a variable distance gap 122 between the glass surface to be scored and the scoring device 114, nosing device 115, or both.
For example, as illustrated schematically in
Turning now to the example shown in
The apparatus 100 can be used to temporarily bend the extended portion 116 of the glass sheet 102 from a first orientation 130 (
Turning briefly to
Returning to
In embodiments, the manipulation device 140 can include an extendable element 144 that is movable towards and away from the extended portion 116 of the glass sheet 102. Although it is contemplated that the extendable element 144 can be moved towards and away from the extended portion 116 along one or more various axes, the extendable element 144 described herein is movable generally along an axis perpendicular to the second side 112 of the glass sheet 102. Although only a single manipulation device 140 is shown, it is contemplated that multiple manipulation devices 140, multiple extendable elements 144, or both, can be utilized to bend the extended portion 116 to a predetermined severing orientation, to achieve a predetermined surface stress along the first side 110 of the glass sheet 102, or both.
The manipulation device 140 can include various configurations for operating the extendable element 144 relative to the glass sheet 102, such as a linear motor, motorized threaded screw assembly, pneumatic or hydraulic cylinder, or similarly functioning devices. In the illustrated example, the manipulation device 140 includes a pneumatic cylinder, such as a constant force air cylinder that can accommodate various glass profiles and can apply a generally uniform contact force F to the glass. Pressure to the air cylinder controls the velocity of the extendable element 144, and adjustable mechanical stops 141 (see
The manipulation device 140 can further include a tip 142 at a distal end of the extendable element 144 that is configured to contact and push against the second side 110 of the extended portion 116. The extendable element 144 is illustrated in a retracted position 146 in
The location of the tip 142 on the glass, relative to the location of the desired score line, can influence the quality of the removed edge portion 104. For example, if the tip 142 is too close to the score line, it can create a mechanical stress field much like a “bulls-eye” due to the localized glass sheet deformation. Conventionally, this localized deformation did not affect scoring quality on the thicker glass due the inherent glass sheet stiffness. However, on relatively thin glass sheets (e.g., 0.3 mm or less) that exhibit relatively low sheet stiffness, this “bulls-eye” deformation becomes more pronounced. If this deformed region extends into the score line, the resulting high stress region can pull the score line away from its intended path and create glass breakage due to inconsistent median crack formation. Without a controlled median crack depth, scoring defects and breakage are more likely to occur. Thus, adjusting the position of the tip 142 and the force F application location can provide a beneficial variable for controlling the shape of the glass sheet and in turn median crack formation and stability.
In embodiments, the manipulation device 140 can be mounted on a conventional VBS tower assembly, such as on a conventional VBS breaker wing area, and used in conjunction with a conventional push break system for removal of the edge portion 104. When the extendable element 144 is in the extended position 148 and the tip 142 is in contact with the extended portion 116 of the glass, the force F, in conjunction with the push break fulcrum of the VBS machine, provides a load force to the glass sheet 102 that reduces, such as eliminates, the gap 122 on the side of the glass sheet 102 adjacent the scoring device 114, the nosing device 115, or both.
Turning to
Turning briefly to
Turning back to the illustrated example of
Using the structure and methods described herein, increased stabilization and rigidity of the extended portion 116 of the glass sheet 102 can be achieved by bending the extended portion 116 to induce an upwardly convex surface, an upwardly concave surface, or both along a direction arranged generally transverse to the direction of the force F. However, due to the temperature differential along the length of the glass sheet due to the manufacturing process, and due to either or both of the tower clamp 120 and the use of the push break assembly 117 as a fulcrum, the glass sheet 102 may exhibit a “bow pop” situation where the original direction of the glass sheet 102 changes direction or shape (e.g., convex to concave, or vice-versa). The “bow pop” behavior is counter-intuitive. For example, turning briefly for
As a result, by inducing a predetermined concave or convex geometry, the edge portion 104 can be stabilized while the glass scoring occurs to enable the scoring device 114 to encounter a stable, predetermined, or both, surface stress field that stabilizes the vent depth and inhibits, such as prevents, premature score crack propagation. The terms concave and convex are used for convenience, and that the “bow pop” behavior can be induced in other directions. Furthermore, although
An example method to manipulate a glass sheet compound shape during a severing operation using the aforedescribed apparatus 100 will now be described with reference to
The method can further include the step of temporarily bending the extended portion 116 from first orientation 130 to a severing orientation 132 by applying a force F to the extended portion 116 of the glass sheet 102. In embodiments, as shown in
Optionally, the method can further include, for example, the step of adjusting an amount, a the position, or both, of the force F (e.g., a position of the tip 142 of the extendable element 144), such as along the slide 150, to achieve either or both of the severing orientation of the glass sheet 102 and the predetermined surface stress along the first side 110 of the glass sheet 102. Optionally, the method can further include, for example, the step of applying multiple forces using multiple manipulation devices, adjusting the location, adjusting the force, or both, of the multiple manipulation devices.
Thereafter, the method can further include, for example, the steps of forming a score line along the first side 110 of the central portion 108 of the glass sheet 102 while the force F is being applied to the extended portion 116 of the glass sheet 102, and subsequently breaking away the edge portion 104 from the glass sheet 102 using the side push break assembly 117. Once scoring is complete, extendable element 144 is moved to the retracted position 146 so that the glass sheet 102 can be removed from the VBS machine. Extendable element 144 can be moved to the refracted position either before or after the breaking operation. The extension and retraction timing can be varied, computer controlled, or both, to match the scoring process so substantially the entire length of the score is sufficiently flattened for successful scoring.
Optionally, the method can further include, for example, the step of waiting a predetermined amount of time after applying the force F to the extended portion 116 of the glass sheet 102, to stabilize the extended portion 116 before forming the score line. The “bow pop” behavior can take some time to occur, and thereafter it may take further time to dissipate the internal vibrations within the glass sheet 102. For example, turning briefly to
The distance of the edge portion 104B among the group one 310 glass sheets was highly variable, which caused variable surface stress and undesirable vibrations in the surface of each sample glass sheet. The variable surface stress and vibrations ultimately resulted in a highly variable median crack among the sample glass sheets, resulting in sheet breakage and lower yields. The glass sheets of group two 312 showed a more consistent distance of the edge portion 104B that provided consistent surface stress and reduced vibrations in the surface of each sample glass sheet. However, the glass sheets of group three 314 exhibited an even more consistent distance of the edge portion 104B, providing even more consistent surface stress and greatly reduced vibrations in the sample glass sheets. The more consistent surface stress and reduced vibrations ultimately resulted in a highly consistent median crack among the sample glass sheets that provided clean and accurate glass severing and higher product yields.
Preferably, the method can be performed multiple times on numerous similar glass sheets 102 during a production run without having to re-adjust the various elements discussed herein. Still, it can be beneficial to adjust one or more of the settings of the apparatus 100 dynamically for each glass sheet 102 to be severed. For example, the method can optionally include the step of sensing a first orientation of the glass sheet 102 after the step of positioning the scoring device 114 against the first side 110 of the central portion 108 of the glass sheet 102. Various portions of the glass sheet 102 could be sensed. In one example, shown in
The method can further include, for example, the optional step of determining the amount of a force F to be applied to the extended portion 116 of the glass sheet 102 sufficient to achieve a predetermined severing orientation based, for example, upon a comparison of the sensed first orientation and the predetermined severing orientation. For example, the sensed first orientation can be similar to the predetermined severing orientation, requiring a relatively small amount of force F to be applied to the extended portion 116. Alternatively, the sensed first orientation can be relatively more divergent from the predetermined severing orientation, requiring a relatively larger amount of force F to be applied to the extended portion 116. The amount of force F can be dynamically determined and adjusted for each glass sheet 102. Optionally, the amount of force F can be dynamically determined and adjusted multiple times in an iterative fashion for each glass sheet 102. In addition or alternatively, the method can further include the optional step of determining the amount of a force F sufficient to achieve a predetermined surface stress along the first side 110 of the glass sheet 102 adjacent the scoring device 114.
Next, based on the determined amount of force, the method can include, for example, the step of applying the force F to the extended portion 116 of the glass sheet 102 to temporarily bend the extended portion 116 of the glass sheet 102 to achieve the predetermined severing orientation, surface stress, or both. Optionally, the method can further include, for example, the step of dynamically adjusting a location of the force F application on the extended portion 116 of the glass sheet 102 based upon the comparison of the sensed first orientation and the predetermined severing orientation. The glass sheet 102 may have internal stresses that cause the glass sheet to distort into a non-symmetric compound shape (e.g., a “potato chip” type shape) that can be corrected by leveraging the “bow pop” behavior across one or more axes. One or more manipulation devices 140 can be dynamically located to apply the force(s) F to accommodate the compound glass shape.
It is further contemplated that the aforedescribed dynamic adjustment method can also be applied to an initial glass sheet in a production run, with the determined settings of the apparatus 100 being used for multiple glass sheets in the production run. For example, the dynamic adjustment method can be used to partially or completely determine the settings of the apparatus 100 for the production run. In embodiments, the location, the amount of force F, or both, can be determined manually or automatically (e.g., by a computer control system) using various techniques, such as via algorithms, look-up tables, finite element analysis (FEA), previous experimental results, etc.
Conventional glass scoring practices in production on 1160×1680 FS size glass product on 0.3 mm thick glass produced about a 60% yield using a standard scoring wheel. Applying the methods and apparatus described herein has been shown to experimentally produce about a 90% yield on the same glass and scoring equipment, which is a significant improvement. The methods described herein can also provide some or all of the following advantages and benefits: reduces bead vibration while scoring by providing consistent stress field during scoring; stabilizes score vent depth; prevents premature bead score crack propagation; produces consistent and repeatable bow direction, magnitude and/or shape; reduces sheet breakage; reduces large and variable sheet shape; facilitates and optimizes sheet positioning for scoring; facilitates scoring of high vertical and horizontal bowed glass sheet; facilitates scoring glass with low sheet stiffness; facilitates scoring glass sheet while cooling is occurring and is heat resistant; facilitates scoring of rapidly changing glass sheet shape (dynamic shape) by directing the glass bow preferentially; the technology and methods can be easily applied across various glass sizes ranges and thicknesses; manipulation structure and methods can be utilized for both narrow and wide bead glass; manipulation structure and methods can be readily integrated into current production systems; installation is uncomplicated requiring minimal disruption to current production set-ups; external pneumatic control can be utilized; manipulation structure and methods are adjustable (e.g., depth, velocity, and/or hold position can be adjusted to fine tune to desire bead shape); manipulation structure and methods have narrow and wide bead capabilities; and prevents fracture during scoring even with variable incoming sheet shapes.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.
